A method for synthesizing low-total-chlorine o-cresol-formaldehyde epoxy resin

Abstract

The invention discloses a method for synthesizing a low-total-chlorine o-cresol-formaldehyde epoxy resin, comprising the following steps: after mixing an organic raw material with an organic auxiliary agent, decompress and evaporate to remove moisture in the system, under inert gas protection, add an alkaline agent, heat and react, decompress and reflux to dehydrate, reflux the organic raw material epichlorohydrin, remove the unreacted organic raw material and organic auxiliary agent in the reaction solution by decompressing and evaporating to obtain a crude product of o-cresol-formaldehyde epoxy resin; add the crude product to methyl isobutyl ketone or toluene, add an alkaline agent for refining reaction, wash with water and remove the aqueous phase, decompress and evaporate to remove impurities, and obtain a low-total-chlorine o-cresol-formaldehyde epoxy resin. The present invention successfully achieves effective control of the chlorine content of the epoxy resin product and reduces the inactive chlorine content therein by optimizing the organic auxiliary agent, regulating the addition amount thereof, optimizing the alkaline agent addition method, and adopting sodium ethoxide and an organic solvent for re-refining treatment, so as to reduce the total chlorine level and improve the quality of the epoxy resin.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, in particular to a method for synthesizing a low-total-chlorine o-cresol-formaldehyde epoxy resin. Background Art

[0002] As a high-performance polymer material, epoxy resin is widely used in many industrial fields such as coatings, composite materials, electronic packaging, casting materials, adhesives, etc. due to its excellent physical and mechanical properties, electrical insulation properties and good adhesion. However, the chlorine content in epoxy resin, especially the presence of inactive chlorine, has an adverse effect on its electrical properties, corrosion resistance and heat resistance, limiting its application potential in high-end electronic and electrical fields.

[0003] The chlorine element in epoxy resin mainly comes from raw materials, catalysts, solvents and by-products in the production process, and can be divided into two categories: inorganic chlorine and organic chlorine. Inorganic chlorine usually exists in the form of chloride ions, and its content can be effectively reduced to an extremely low level through simple water washing treatment, which has relatively little effect on the performance of the resin. Organic chlorine is much more complicated. As part of an organic molecule, it includes two forms: active chlorine and inactive chlorine. Active chlorine can be effectively removed by chemical methods such as alkali refining, but inactive chlorine is difficult to remove by conventional refining methods due to its strong chemical stability, becoming a key factor affecting the total chlorine content of the resin.

[0004] Inactive chlorine mainly comes from by-products in the resin synthesis process, which may be generated in the process of incomplete reaction of raw materials, side reactions under the action of catalysts, or solvent residues. The presence of inactive chlorine not only reduces the electrical insulation and corrosion resistance of epoxy resin, but also may affect its processing performance and long-term stability. This problem is particularly prominent in the electronic and electrical fields where material performance requirements are extremely high.

[0005] In view of the adverse effects of inactive chlorine on the performance of epoxy resin and its difficulty in removal, developing a process method that can effectively control and reduce the inactive chlorine content in epoxy resin and thereby reduce its total chlorine level is of great significance for improving the quality of epoxy resin and expanding its application areas. Summary of the invention

[0006] In view of the technical problem in the prior art that inactive chlorine is difficult to remove, which in turn has an adverse effect on the performance of epoxy resin, the present invention develops and optimizes a synthesis method to effectively control and reduce the inactive chlorine content in the epoxy resin, so as to reduce the total chlorine level and improve the quality of the epoxy resin.

[0007] The present invention provides a method for synthesizing a low-total-chlorine o-cresol-formaldehyde epoxy resin, comprising the following steps:

[0008] S1: Dehydration stage, o-cresol resin, epichlorohydrin and organic additives are mixed in a reaction container, and the water in the system is removed by evaporation under reduced pressure to obtain a raw material liquid;

[0009] S2: Reaction stage, under the protection of inert gas, adding alkaline reagent to the raw material liquid, heating for reaction, decompressing and refluxing for dehydration, refluxing the epichlorohydrin into the reaction container, and obtaining a reaction liquid;

[0010] S3: Removal stage, removing unreacted epichlorohydrin and organic additives in the reaction solution by reduced pressure evaporation to obtain a crude product of o-cresol-formaldehyde epoxy resin;

[0011] S4: a refining stage, wherein the crude o-cresol epoxy resin product is added to methyl isobutyl ketone or toluene, and an alkaline reagent is added to perform a refining reaction to obtain a refined liquid;

[0012] S5: impurity removal stage, after the refined liquid is washed with water and the water phase is removed, impurities are removed by evaporation under reduced pressure to obtain a low total chlorine o-cresol epoxy resin.

[0013] Furthermore, the following steps are included between step S4 and step S5:

[0014] S4-0: re-refining stage, adding sodium ethoxide and an organic solvent to the refined liquid, heating to perform a re-refining reaction, and obtaining a re-refined liquid;

[0015] The re-refined liquid is subjected to the impurity removal process in step S5 to obtain a low total chlorine o-cresol epoxy resin.

[0016] Furthermore, the vacuum degree of the reduced pressure condition in steps S1, S2 and S5 is 5 to 30 kPa, the vacuum degree of the reduced pressure condition in step S3 is 3 to 30 kPa, and the alkaline reagent in steps S2 and S4 is sodium hydroxide or potassium hydroxide.

[0017] Furthermore, in step S1, the mass ratio of the o-cresol resin, epichlorohydrin and the organic auxiliary agent is 5:10-30:1-15, and the organic auxiliary agent is at least one of diisobutyl ketone, butyl ether, ethylene glycol monomethyl ether and propylene glycol monomethyl ether.

[0018] Furthermore, the dehydration conditions in step S1 are a temperature of 60 to 90° C. and a dehydration time of 0.5 to 2 hours.

[0019] Furthermore, the mass ratio of the alkaline reagent in step S2 to the o-cresol-formaldehyde resin in step S1 is 3:4-6, the heating temperature is 40-90° C., and the reaction time is 2-5 hours.

[0020] Furthermore, the alkaline agent is added in multiple times and evenly, and preferably added once every 15 minutes.

[0021] Furthermore, the evaporation temperature in step S3 is 60-150°C for 1-5 hours, and the evaporation temperature in step S5 is 100-180°C.

[0022] Furthermore, the mass ratio of the o-cresol-formaldehyde resin in step S1, the methyl isobutyl ketone or toluene in step S4, and the alkaline reagent is 1:1-5:0.01-0.1, and sampling is performed during the reaction to detect the hydrolysis chlorine index. When the hydrolysis chlorine reaches below 50 ppm, water is added to liquidate and remove the aqueous phase.

[0023] Furthermore, the mass ratio of the sodium ethoxide, the organic solvent and the o-cresol-formaldehyde resin in step S4-0 is 1:1-5:5-20, the organic solvent is preferably ethanol, the heating temperature is 35-90° C., and the reaction time is 1-3 h.

[0024] The present invention has the following beneficial effects:

[0025] 1. The present invention achieves effective suppression of the water content of the reaction system by optimizing the type of organic auxiliary agent, regulating the addition amount thereof, and regulating the addition method of the alkaline agent in the reaction process, thereby improving the solubility of the alkaline agent in the system, promoting the contact efficiency between the alkaline agent and the organic raw material, ensuring the precise guidance of the reaction path, and fundamentally reducing the generation of unnecessary by-products, especially those by-products that may introduce inactive chlorine, reducing the proportion of inactive chlorine in the epoxy resin product, and improving the purity and quality of the product.

[0026] 2. The present invention uses sodium ethoxide and an organic solvent to purify the crude product, converting the residual chlorine element structure in the product into a double bond structure or an ether compound, thereby achieving the chemical conversion and effective removal of the chlorine element, further reducing the total chlorine content in the product to a lower level, and ensuring the final quality of the epoxy resin product. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 The synthetic process flow chart of the low total chlorine o-cresol epoxy resin of the present invention is DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] The present invention provides a method for synthesizing a low total chlorine o-cresol-formaldehyde epoxy resin, comprising the following steps: Figure 1 As shown:

[0031] S1: Dehydration stage, o-cresol resin, epichlorohydrin and organic additives are mixed in a reaction container, and the water in the system is removed by evaporation under reduced pressure to obtain a raw material liquid;

[0032] S2: Reaction stage, under the protection of inert gas, adding alkaline reagent to the raw material liquid, heating for reaction, decompressing and refluxing for dehydration, refluxing the epichlorohydrin into the reaction container, and obtaining a reaction liquid;

[0033] S3: Removal stage, removing unreacted epichlorohydrin and organic additives in the reaction solution by reduced pressure evaporation to obtain a crude product of o-cresol-formaldehyde epoxy resin;

[0034] S4: a refining stage, wherein the crude o-cresol epoxy resin product is added to methyl isobutyl ketone or toluene, and an alkaline reagent is added to perform a refining reaction to obtain a refined liquid;

[0035] S5: impurity removal stage, after the refined liquid is washed with water and the water phase is removed, impurities are removed by evaporation under reduced pressure to obtain a low total chlorine o-cresol epoxy resin.

[0036] The synthesis method provided in this scheme achieves effective suppression of the water content of the reaction system by optimizing the type of organic additives and regulating their addition amount, improves the solubility of the alkaline reagent in the system, ensures the precise guidance of the reaction path, and fundamentally reduces the generation of unnecessary by-products, especially those by-products that may introduce inactive chlorine, reduces the proportion of inactive chlorine in the epoxy resin product, and improves the purity and quality of the product. Furthermore, the following steps are also included between step S4 and step S5:

[0037] S4-0: re-refining stage, adding sodium ethoxide and an organic solvent to the refined liquid, heating to perform a re-refining reaction, and obtaining a re-refined liquid;

[0038] This solution uses sodium ethoxide and organic solvents to purify the crude product, converting the residual chlorine element structure in the product into a double bond structure or ether compounds, achieving the chemical conversion and effective removal of the chlorine element, further reducing the total chlorine content in the product to a lower level, and ensuring the final quality of the epoxy resin product.

[0039] The re-refined liquid is subjected to the impurity removal process in step S5 to obtain a low total chlorine o-cresol epoxy resin.

[0040] Furthermore, the vacuum degree of the reduced pressure condition in steps S1, S2 and S5 is 5 to 30 kPa, the vacuum degree of the reduced pressure condition in step S3 is 3 to 30 kPa, and the alkaline reagent in steps S2 and S4 is sodium hydroxide or potassium hydroxide.

[0041] Furthermore, in step S1, the mass ratio of the o-cresol resin, epichlorohydrin and the organic auxiliary agent is 5:10-30:1-15, and the organic auxiliary agent is at least one of diisobutyl ketone, butyl ether, ethylene glycol monomethyl ether and propylene glycol monomethyl ether.

[0042] Furthermore, the dehydration conditions in step S1 are a temperature of 60 to 90° C. and a dehydration time of 0.5 to 2 hours.

[0043] Furthermore, the mass ratio of the alkaline reagent in step S2 to the o-cresol-formaldehyde resin in step S1 is 3:4-6, the heating temperature is 40-90° C., and the reaction time is 2-5 hours.

[0044] Furthermore, the alkaline agent is added in multiple times and evenly, and preferably added once every 15 minutes.

[0045] Furthermore, the evaporation temperature in step S3 is 60-150°C for 1-5 hours, and the evaporation temperature in step S5 is 100-180°C.

[0046] Furthermore, the mass ratio of the o-cresol-formaldehyde resin in step S1, the methyl isobutyl ketone or toluene in step S4, and the alkaline reagent is 1:1-5:0.01-0.1, and sampling is performed during the reaction to detect the hydrolysis chlorine index. When the hydrolysis chlorine reaches below 50 ppm, water is added to liquidate and remove the aqueous phase.

[0047] Furthermore, the mass ratio of the sodium ethoxide, the organic solvent and the o-cresol-formaldehyde resin in step S4-0 is 1:1-5:5-20, the organic solvent is preferably ethanol, the heating temperature is 35-90° C., and the reaction time is 1-3 h.

[0048] The above schemes significantly enhance the control accuracy of the reaction system by adjusting the selection and ratio of organic additives, alkaline reagents and organic additives, combined with optimized heating and decompression vacuum settings. In particular, adjusting the stepwise addition of alkaline reagents promotes efficient contact between alkaline reagents and organic raw materials, effectively reduces the inactive chlorine content, accelerates the reaction process, and improves the quality of epoxy resin products.

[0049] Example 1

[0050] Synthesis of low total chlorine o-cresol epoxy resin:

[0051] S1: 200 g of o-cresol resin, 556 g of epichlorohydrin, 23.1 g of diisobutyl ketone and 23.1 g of butyl ether were placed in a reaction kettle, stirred and dissolved, heated to 60°C, and vacuum-dried for 0.5 h to obtain a raw material solution.

[0052] S2: Add 97 g of solid potassium hydroxide into the reactor, add 8 g of potassium hydroxide every 15 minutes, react at 65°C for 3 hours, evacuate after adding, vacuum degree is 10 kPa, dehydrate for 0.5 hour, reflux epichlorohydrin into the reactor to obtain raw material liquid.

[0053] S3: gradually raise the temperature of the raw material liquid to 150°C and the vacuum degree to 10 kPa, remove epichlorohydrin, diisobutyl ketone and butyl ether, and obtain a crude product of o-cresol epoxy resin.

[0054] S4: Add 400 g of methyl isobutyl ketone to the reactor to dissolve the crude resin product, add 5 g of potassium hydroxide, measure the hydrolyzed chlorine every 0.5 h until the hydrolyzed chlorine is less than 50 ppm, and obtain a refined liquid.

[0055] S5: Add 400 g of deionized water to the refined liquid and stir for 20 min. Separate the liquid to remove the aqueous phase, repeat the water washing and separation to remove the aqueous phase for 3 times, using 80 g of deionized water for each water washing. Heat the organic phase to 140°C, evacuate to 10 kPa, remove methyl isobutyl ketone, and obtain the finished product.

[0056] Example 2

[0057] Synthesis of low total chlorine o-cresol epoxy resin:

[0058] Steps S1 to S4 are the same as those in Example 1

[0059] S4-0: Add 3.5 g of sodium ethoxide and 3.5 g of ethanol to the refined liquid in the reactor, heat to 65°C, and react for 1 hour to obtain a refined liquid.

[0060] S5: Add 400 g of deionized water to the refined liquid and stir for 20 min, separate the liquid to remove the water phase, then add 80 g of deionized water to wash, wash three times and separate the liquid to remove the water phase, heat to 140°C, evacuate to 10 kPa, remove methyl isobutyl ketone, and obtain the finished product.

[0061] Example 3

[0062] Synthesis of low total chlorine o-cresol epoxy resin:

[0063] S1: 200 g of o-cresol resin, 556 g of epichlorohydrin and 46.2 g of ethylene glycol monomethyl ether were placed in a reaction kettle, stirred and dissolved, heated to 90° C., and vacuum-dried for 0.5 h to obtain a raw material solution.

[0064] S2: Add 69.1 g of solid sodium hydroxide into the reactor, add 4.6 g of sodium hydroxide every 20 minutes, react at 40°C for 5 hours, evacuate after adding, vacuum degree is 10 kPa, dehydrate for 0.5 hours, reflux epichlorohydrin into the reactor to obtain raw material liquid.

[0065] S3: gradually heating the raw material liquid to 150°C and setting the vacuum degree to 6.5 kPa to remove epichlorohydrin and ethylene glycol monomethyl ether to obtain a crude product of o-cresol-formaldehyde epoxy resin.

[0066] S4: Add 400 g of methyl isobutyl ketone to the reactor to dissolve the crude resin product, add 3.6 g of sodium hydroxide, measure the hydrolyzed chlorine every 0.5 h until the hydrolyzed chlorine is less than 50 ppm, and obtain a refined liquid.

[0067] S5: Add 400 g of deionized water to the refined liquid and stir for 10 min. Separate the liquid to remove the aqueous phase, repeat the water washing and separation to remove the aqueous phase for 3 times, using 80 g of deionized water for each water washing. Heat the organic phase to 100° C., evacuate to 10 kPa, remove methyl isobutyl ketone, and obtain the finished product.

[0068] Example 4

[0069] Synthesis of low total chlorine o-cresol epoxy resin:

[0070] S1: 200 g of o-cresol resin, 556 g of epichlorohydrin and 46.2 g of propylene glycol monomethyl ether were added into a reaction kettle, stirred and dissolved, heated to 75°C, and vacuum-dried for 2 h to obtain a raw material solution.

[0071] S2: Add 69.1 g of solid sodium hydroxide into the reactor, add once every 10 minutes, 11.5 g of sodium hydroxide each time, react at 90°C for 2 hours, evacuate after adding, vacuum degree 10 kPa, dehydrate for 0.5 hours, reflux epichlorohydrin into the reactor to obtain a raw material solution.

[0072] S3: gradually raise the temperature of the raw material liquid to 60°C and set the vacuum degree to 3 kPa to remove epichlorohydrin and propylene glycol monomethyl ether to obtain a crude product of o-cresol-formaldehyde epoxy resin.

[0073] S4: Add 400 g of methyl isobutyl ketone to the reactor to dissolve the crude resin product, add 3.6 g of sodium hydroxide, measure the hydrolyzed chlorine every 0.5 h until the hydrolyzed chlorine is less than 50 ppm, and obtain a refined liquid.

[0074] S4-0: Add 3.5 g of sodium ethoxide and methanol to the refined liquid in the reactor, heat to 35°C, and react for 3 hours to obtain a refined liquid.

[0075] S5: Add 400 g of deionized water to the refined liquid and stir for 20 min. Separate the liquid to remove the aqueous phase, repeat the water washing and separation to remove the aqueous phase for 3 times, using 80 g of deionized water for each water washing. Heat the organic phase to 180° C., evacuate to 10 kPa, remove methyl isobutyl ketone, and obtain the finished product.

[0076] Comparative Example 1

[0077] Synthesis of o-cresol epoxy resin:

[0078] S1: 200 g of o-cresol resin and 556 g of epichlorohydrin were added into a reaction kettle, stirred and dissolved, heated to 60°C, and vacuum-dried for 0.5 h to obtain a raw material solution.

[0079] S2: Add 97 g of solid potassium hydroxide into the reactor at one time, react at 65° C. for 3 h, evacuate after the addition to a vacuum degree of 10 kPa, dehydrate for 0.5 h, and reflux epichlorohydrin into the reactor to obtain a raw material solution.

[0080] S3: gradually raise the temperature of the raw material liquid to 150°C and set the vacuum degree to 10 kPa to remove epichlorohydrin to obtain a crude product of o-cresol-formaldehyde epoxy resin.

[0081] S4: Add 400 g of methyl isobutyl ketone to the reactor to dissolve the crude resin product, add 5 g of potassium hydroxide, measure the hydrolyzed chlorine every 0.5 h until the hydrolyzed chlorine is less than 50 ppm, and obtain a refined liquid.

[0082] S5: Add 400 g of deionized water to the refined liquid and stir for 20 min. Separate the liquid to remove the aqueous phase, repeat the water washing and separation to remove the aqueous phase for 3 times, using 80 g of deionized water for each water washing. Heat the organic phase to 140°C, evacuate to 10 kPa, remove methyl isobutyl ketone, and obtain the finished product.

[0083] Comparative Example 2

[0084] Synthesis of o-cresol epoxy resin:

[0085] S1: 200 g of o-cresol resin, 556 g of epichlorohydrin, 23.1 g of ethylene glycol monomethyl ether and 23.1 g of propylene glycol monomethyl ether were placed in a reaction kettle, stirred and dissolved, heated to 60°C, and vacuum-dried for 0.5 h to obtain a raw material solution.

[0086] S2: Add 97 g of solid potassium hydroxide into the reactor at one time, react at 65° C. for 3 h, evacuate after the addition to a vacuum degree of 10 kPa, dehydrate for 0.5 h, and reflux epichlorohydrin into the reactor to obtain a raw material solution.

[0087] S3: gradually raising the temperature of the raw material liquid to 150°C and the vacuum degree to 10 kPa to remove epichlorohydrin, ethylene glycol monomethyl ether and propylene glycol monomethyl ether to obtain a crude product of o-cresol-formaldehyde epoxy resin.

[0088] S4: Add 400 g of methyl isobutyl ketone to the reactor to dissolve the crude resin product, add 5 g of potassium hydroxide, measure the hydrolyzed chlorine every 0.5 h until the hydrolyzed chlorine is less than 50 ppm, and obtain a refined liquid.

[0089] S4-0: Add 3.5 g of sodium ethoxide and 3.5 g of ethanol to the refined liquid in the reactor, heat to 90°C, and react for 1 hour to obtain a refined liquid.

[0090] S5: Add 400 g of deionized water to the refined liquid and stir for 20 min. Separate the liquid to remove the aqueous phase, repeat the water washing and separation to remove the aqueous phase for 3 times, using 80 g of deionized water for each water washing. Heat the organic phase to 140°C, evacuate to 10 kPa, remove methyl isobutyl ketone, and obtain the finished product.

[0091] Comparative Example 3

[0092] Synthesis of o-cresol epoxy resin:

[0093] S1: 200 g of o-cresol resin and 556 g of epichlorohydrin were added into a reaction kettle, stirred and dissolved, heated to 60°C, and vacuum-dried for 0.5 h to obtain a raw material solution.

[0094] S2: Add 69.1 g of solid sodium hydroxide into the reactor, add 8.6 g of sodium hydroxide every 10 minutes, react at 65°C for 3 hours, evacuate after adding, vacuum degree 10 kPa, dehydrate for 0.5 hours, reflux epichlorohydrin into the reactor to obtain a raw material solution.

[0095] S3: gradually raise the temperature of the raw material liquid to 150°C and set the vacuum degree to 10 kPa to remove epichlorohydrin to obtain a crude product of o-cresol-formaldehyde epoxy resin.

[0096] S4: Add 400 g of methyl isobutyl ketone to the reactor to dissolve the crude resin product, add 3.6 g of sodium hydroxide, measure the hydrolyzed chlorine every 0.5 h until the hydrolyzed chlorine is less than 50 ppm, and obtain a refined liquid.

[0097] S4-0: Add 3.5 g of sodium ethoxide and methanol to the refined liquid in the reactor, heat to 65°C, and react for 2 hours to obtain a refined liquid.

[0098] S5: Add 400 g of deionized water to the refined liquid and stir for 20 min. Separate the liquid to remove the aqueous phase, repeat the water washing and separation to remove the aqueous phase for 3 times, using 80 g of deionized water for each water washing. Heat the organic phase to 140°C, evacuate to 10 kPa, remove methyl isobutyl ketone, and obtain the finished product.

[0099] Comparative Example 4

[0100] The o-cresol-formaldehyde epoxy resin was synthesized according to the reaction conditions of Example 3 in patent CN10112175A.

[0101] The test conditions of each embodiment and comparative example are shown in Table 1.

[0102] Table 1 List of test conditions for each embodiment and comparative example

[0103]

[0104] Test results and analysis

[0105] The o-cresol-formaldehyde epoxy resins prepared in the embodiments and comparative examples were tested for various technical indicators including epoxy equivalent, softening point, etc., and in particular, the chlorine content of the resin was comprehensively tested and analyzed, and the inorganic chlorine, organic chlorine (active chlorine and inactive chlorine) and total chlorine levels were tested and calculated. The statistics of various parameters are shown in Table 1.

[0106] Based on the parameters listed in Table 1, a detailed technical evaluation of the epoxy equivalent, softening point and chlorine content of the epoxy resin product of the present invention was carried out. Specifically, the epoxy resins prepared in all embodiments showed a stable epoxy equivalent range (197.4-198.2 g / mol), which is consistent with the industry-recognized high-quality epoxy resin standard (197-207 g / eq). At the same time, the softening point is maintained between 72.1 and 73.7°C, which also meets the conventional requirements of high-quality epoxy resins (70-76°C), thereby verifying the excellent characteristics of the products of the present invention in core quality indicators such as epoxy equivalent and softening point.

[0107] Table 1 Statistical table of cyclic resin parameters of various embodiments and comparative examples

[0108]

[0109] Regarding the control of chlorine content, the preparation process of the present invention has achieved significant improvement. As shown in Table 1, in terms of inorganic chlorine, through fine neutralization and elution procedures, the inorganic chlorine content in the epoxy resin finished products of all embodiments is less than 3ppm, which is far below the conventional level. In the regulation of active chlorine, through precise preparation process monitoring, the active chlorine content in the finished product is strictly controlled to be less than 100ppm, and some embodiments are even less than 50ppm, reflecting the precise grasp of the reaction conditions. In terms of inactive chlorine, all embodiments are effectively controlled within 700ppm, and embodiments 2 and 4 have reached an excellent level of less than 300ppm. In summary, the total chlorine content of epoxy resin prepared by the present invention is successfully reduced to less than 750ppm, and the lowest value (Example 2) is only 276ppm, which is significantly better than the traditional preparation method.

[0110] Further analysis shows that the innovation of the present invention lies in the fine control of the preparation process. Compared with Comparative Example 1 which has not been specifically optimized, Example 2 achieves a significant reduction in the total chlorine, active chlorine and inactive chlorine content by introducing an organic auxiliary agent, adding an alkaline agent in batches and using a sodium ethoxide-ethanol solution for re-refining treatment, which decreased by 80%, 53% and 81% respectively. This result shows that the introduction of organic auxiliary agents, the addition and regulation of alkaline agents and the re-refining steps can effectively promote the completeness of the reaction to reduce the generation of by-products, and realize the chemical conversion and removal of chlorine elements, thereby reducing the total chlorine level of the product.

[0111] By comparing the preparation differences between different examples, it can be found that the re-refining process of sodium ethoxide and organic solvent plays a key role in reducing the chlorine content. For example, compared with Example 1, Example 2 has a reduced content of total chlorine, active chlorine and inactive chlorine due to the addition of the re-refining step. Similarly, the comparison between Example 4 and Example 3 also confirms this point.

[0112] In terms of the method of adding alkaline reagents, Example 2 significantly reduced the total chlorine, active chlorine and inactive chlorine contents of the product by adding KOH evenly in batches compared to the one-time addition method of Comparative Example 2, which further proves the effectiveness of the batch addition strategy in improving the completeness of the reaction and reducing the formation of chlorine-containing by-products.

[0113] As for the application of organic additives, the comparison between Example 4 and Comparative Example 3 shows that the addition of propylene glycol monomethyl ether as an organic additive effectively suppresses the moisture content in the reaction system and improves the solubility of the alkaline reagent, thereby reducing the generation of unnecessary by-products, especially those by-products that may introduce inactive chlorine, thereby improving the purity and quality of the product.

[0114] In addition, compared with the prior art (such as Example 3 of Comparative Example 4 based on CN10112175A), the epoxy resin of the present invention shows significant advantages in total chlorine, active chlorine and inactive chlorine content, verifying the effectiveness of the present invention in optimizing the preparation process and reducing the chlorine content.

[0115] In summary, the preparation process designed by the present invention, including selecting the organic auxiliary agent, adjusting the addition amount thereof, optimizing the addition method of the alkaline agent, and using sodium ethoxide and an organic solvent for re-refining treatment, successfully achieves effective control of the chlorine content of the epoxy resin product, while ensuring the high quality requirements of key performance indicators such as epoxy equivalent and softening point.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for synthesizing a low-total-chlorine o-cresol-formaldehyde epoxy resin, characterized in that: The following steps are involved: S1: Dehydration stage, o-cresol resin, epichlorohydrin and organic additives are mixed in a reaction container, and the water in the system is removed by evaporation under reduced pressure to obtain a raw material liquid; S2: Reaction stage, under the protection of inert gas, adding alkaline reagent to the raw material liquid, adding the alkaline reagent evenly in multiple times, heating for reaction, decompressing and refluxing for dehydration, refluxing the epichlorohydrin into the reaction container, and obtaining a reaction liquid; S3: Removal stage, removing unreacted epichlorohydrin and organic additives in the reaction solution by reduced pressure evaporation to obtain a crude product of o-cresol-formaldehyde epoxy resin; S4: a refining stage, wherein the crude o-cresol epoxy resin product is added to methyl isobutyl ketone or toluene, and an alkaline reagent is added to perform a refining reaction to obtain a refined liquid; S5: impurity removal stage, after the refined liquid is washed with water and the water phase is removed, impurities are removed by evaporation under reduced pressure to obtain a low total chlorine o-cresol epoxy resin; The following steps are also included between steps S4 and S5: S4-0: re-refining stage, adding sodium ethoxide and an organic solvent to the refined liquid, heating to perform a re-refining reaction, and obtaining a re-refined liquid; The re-refined liquid is subjected to the impurity removal process in step S5 to obtain a low total chlorine o-cresol epoxy resin.

2. The method for synthesizing a low-total-chlorine o-cresol-formaldehyde epoxy resin according to claim 1, wherein: The vacuum degree of the reduced pressure condition in steps S1, S2 and S5 is 5 to 30 kPa, the vacuum degree of the reduced pressure condition in step S3 is 3 to 30 kPa, and the alkaline reagent in steps S2 and S4 is sodium hydroxide or potassium hydroxide.

3. The method for synthesizing a low-total-chlorine o-cresol-formaldehyde epoxy resin according to claim 1, characterized in that: The mass ratio of the o-cresol resin, epichlorohydrin and organic additive in step S1 is 5:10-30:1-15, and the organic additive is at least one of diisobutyl ketone, butyl ether, ethylene glycol monomethyl ether and propylene glycol monomethyl ether.

4. The method for synthesizing the low total chlorine o-cresol-formaldehyde epoxy resin according to claim 1, characterized in that: The dehydration conditions in step S1 are a temperature of 60 to 90° C. and a dehydration time of 0.5 to 2 hours.

5. The method for synthesizing the low total chlorine o-cresol-formaldehyde epoxy resin according to claim 1, characterized in that: The mass ratio of the alkaline reagent in step S2 to the o-cresol-formaldehyde resin in step S1 is 3:4-6, the heating temperature is 40-90° C., and the reaction time is 2-5 hours.

6. The method for synthesizing the low total chlorine o-cresol-formaldehyde epoxy resin according to claim 1, characterized in that: The alkaline reagent is added once every 15 minutes.

7. The method for synthesizing the low total chlorine o-cresol-formaldehyde epoxy resin according to claim 1, characterized in that: In step S3, the evaporation temperature is 60-150°C and lasts for 1-5 hours. In step S5, the evaporation temperature is 100-180°C.

8. The method for synthesizing the low total chlorine o-cresol-formaldehyde epoxy resin according to claim 1, characterized in that: The mass ratio of the o-cresol-formaldehyde resin in step S1, the methyl isobutyl ketone or toluene in step S4, and the alkaline reagent is 1:1-5:0.01-0.

1. During the reaction, samples are taken to detect the hydrolysis chlorine index. When the hydrolysis chlorine reaches below 50 ppm, water is added to liquidate and remove the water phase.

9. The method for synthesizing the low total chlorine o-cresol-formaldehyde epoxy resin according to claim 1, characterized in that: The mass ratio of the sodium ethoxide, the organic solvent and the o-cresol-formaldehyde resin in step S4-0 is 1:1-5:5-20, the organic solvent is ethanol, the heating temperature is 35-90° C., and the reaction time is 1-3 hours.

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