Preparation method of diglycidyl ester type epoxy resin used as reactive diluent

Abstract

The invention discloses a preparation method of diglycidyl ester type epoxy resin capable of being used as a resin reactive diluent, and belongs to the field of organic chemical synthesis. The synthesis process of the epoxy resin comprises the following steps: mixing tetrahydrophthalic anhydride, water, epichlorohydrin and tetramethylammonium chloride, heating by taking methylbenzene as a solvent, and carrying out hydrolysis and ring-opening reaction for 2-12 hours; desolventizing the ring-opening reaction liquid through reduced pressure distillation to remove excessive epichlorohydrin and methylbenzene; adding toluene as a solvent, heating under a reduced pressure condition until reflux occurs, starting to dropwise add a NaOH aqueous solution, filtering, washing and desalting the reaction liquid after the ring-closure reaction is finished, and carrying out reduced pressure distillation to obtain the tetrahydrophthalic acid diglycidyl ester epoxy resin.

Description

Technical Field

[0001] The invention discloses a method for preparing a glycidyl ester epoxy resin used as an active diluent, and belongs to the technical field of organic chemistry. Background Art

[0002] The development of epoxy resin in my country began in 1956. After more than 60 years of efforts, the production and application of epoxy resin has developed rapidly. Unlike other resins such as phenolic resin and polyurethane resin, epoxy resin has the following characteristics: (1) high bonding strength and wide bonding surface; (2) low curing shrinkage; (3) good stability, acid and alkali resistance and various media resistance; (4) excellent electrical insulation; (5) high mechanical strength; (6) good processability. Therefore, epoxy resin is widely used in various fields of the national economy. According to its application method, it can be used as: coating material, reinforcing material, casting material, molding compound, adhesive, modifier, etc.

[0003] At present, the main industrial epoxy resin products are glycidyl ether epoxy resins, which are obtained by polycondensation of polyols or polyphenols with epichlorohydrin. Among them, the most representative variety is diglycidyl ether of bisphenol A (DGEBPA), which is known as a general-purpose epoxy resin. Although this type of epoxy resin has many excellent properties, it also has the following disadvantages: (1) poor weather resistance, it will degrade under ultraviolet radiation, resulting in performance degradation and cannot be used outdoors for a long time; (2) low impact strength; (3) poor resistance to high and low temperatures. Summary of the invention

[0004] In view of some technical defects of existing industrial production of epoxy resin in practical application, the present invention interprets a new synthesis process route of diglycidyl ester type epoxy resin, and its main preparation comprises: using 1,2,3,6-tetrahydrophthalic anhydride, water and epichlorohydrin as raw materials, tetramethylammonium chloride as catalyst, firstly evacuating the reaction system for 2 hours, then introducing nitrogen, and repeating this process three times; slowly heating up to carry out esterification reaction, the esterification temperature is 40-130°C; after esterification reaction for 2-12 hours, adding alkali into the reaction system, and carrying out ring-closing saponification reaction at 35-100°C, reflux dehydration is required during the reaction process, and solvent is added after the reaction is completed, washing with water to remove salt, standing and separating to finally obtain a neutral organic phase, and after decompression and solvent removal, tetrahydrophthalic acid diglycidyl ester epoxy resin is obtained.

[0005] The pretreatment method after the raw materials are fed is as follows: the reaction system is evacuated for 2 hours, and then nitrogen is introduced for protection. The nitrogen is introduced for protection during the entire esterification reaction process, which can ensure that the obtained tetrahydrophthalic acid diglycidyl ester epoxy resin has excellent chromaticity. During the saponification reaction, the water in the reaction system can be removed in time by adding alkali and then decompressing and refluxing for dehydration, which greatly helps the ring-closing reaction and effectively prevents the hydrolysis of the target product and the occurrence of side reactions.

[0006] The method for preparing diglycidyl tetrahydrophthalate of the present invention comprises the following steps:

[0007] A. Under normal pressure, heat tetrahydrophthalic anhydride to dissolve in an organic solvent, add water and quaternary ammonium salt as catalysts for the ring-opening step, and drop epihalohydrin to carry out esterification reaction. The ring-opening esterification reaction temperature is 40-130°C and the esterification time is 2-12h;

[0008] B. Add 20-80% of liquid alkali to the first step esterification reaction solution for ring-closing reaction. The ring-closing reaction time is 2-8 hours of heat preservation time, and the whole ring-closing reaction temperature is 35-100°C;

[0009] C. Adding organic solvent to the saponification reaction solution of the second step, filtering, washing with water, dissolving salt and then treating to obtain tetrahydrophthalic acid diglycidyl ester epoxy resin.

[0010] Wherein: after the raw materials are added, the reaction system is evacuated for 2 hours and nitrogen is introduced for protection. In step A, the epihalohydrin is selected from 1-chloro-2,3-epoxypropane, 1-bromo-2,3-epoxypropane, etc., preferably 1-chloro-2,3-epoxypropane.

[0011] In step A, the organic solvent is selected from: aromatic hydrocarbons such as benzene, toluene, xylene, etc.; ketones such as methyl isobutyl ketone; alkanes such as dichloromethane, dichloroethane, n-heptane, etc., and the suitable solvent is toluene, methyl isobutyl ketone, and n-heptane in combination with the characteristics of each solvent, and the preferred solvent is toluene. The amount of solvent input is 2 to 6 times the amount of tetrahydrophthalic anhydride input.

[0012] In step A, the quaternary ammonium salt is tetrabutylammonium bromide or hexadecyltrimethylammonium bromide. The molar ratio of the catalyst to tetrahydrophthalic anhydride is 0.01 to 0.08:1, preferably 0.01 to 0.03:1.

[0013] In step A, the molar ratio of tetrahydrophthalic anhydride to water is 0.8-1.5:1, preferably 0.8-1.1:1.

[0014] In step A, the epichlorohydrin is added dropwise. Since epichlorohydrin and tetrahydrophthalic anhydride react violently under the action of a catalyst and release a large amount of heat, it is easy to add the material dropwise and remove the reaction heat by an effective cooling method.

[0015] In step A, the ring-opening esterification reaction must be carried out at an appropriate temperature and time to better complete the reaction. Suitable process parameters are a temperature of 40 to 130° C. and a time of 2 to 12 hours. Optimum process parameters are 60 to 90° C. and a time of 5 to 7 hours.

[0016] In step A, the molar ratio of epichlorohydrin to tetrahydrophthalic anhydride is greater than 3 / 1, so as to ensure that the esterification reaction is fully and completely. Excessive epichlorohydrin input can ensure that the esterification reaction is fully and completely, but it also increases the process steps of recovering epichlorohydrin. The appropriate input amount is 3 to 10 times the mole number of tetrahydrophthalic anhydride, and the preferred input amount is 4 to 6 times the mole number of tetrahydrophthalic anhydride.

[0017] In step B, the base is selected from: inorganic bases such as NaOH, KOH, etc.; organic bases such as sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide, etc. The suitable base raw material is NaOH aqueous solution, the suitable concentration is 20-80%, and the preferred concentration range is 30-50%.

[0018] In step B, the liquid alkali is added dropwise, and the ring-closing reaction is highly exothermic. If the liquid alkali is added at one time, the local temperature of the reaction solution rises sharply, which seriously affects the quality of the product. At the same time, a decompression dehydration process should be adopted during the liquid alkali addition process to remove the water in the reaction system in time and prevent the product from being hydrolyzed so as to better improve the product quality.

[0019] In step B, the ring-closing reaction must be completed at an appropriate temperature and time to ensure that the product has a high epoxy value and a low organic chlorine content. Suitable process parameters are a temperature of 35 to 100° C. and a time of 2 to 8 hours. Optimum process parameters are 40 to 60° C. and a time of 2 to 4 hours.

[0020] In step B, the amount of alkali added is more than 2 times the molar number of tetrahydrophthalic anhydride to ensure that the ring-closing reaction is fully carried out. Too much alkali will cause the product to decompose and generate sodium soap, which seriously affects the product quality. The appropriate feed ratio is 1:2.0-3.0, and the preferred feed ratio is 1:2.2-2.5.

[0021] In step C, the organic solvent is toluene, and the amount of toluene added is the same mass as tetrahydrophthalate. The amount of solvent added to the overall reaction system is 2 to 6 times (mass ratio) of tetrahydrophthalate.

[0022] In step C, in the water washing and salt dissolving process, the suitable salt dissolving temperature is 30-80°C and the salt dissolving time is 1-5 hours. The preferred salt dissolving temperature is 30-50°C and the salt dissolving time is 1-2 hours.

[0023] In step C, the subsequent treatment measures include extraction of the product solution-brine solution, neutralization, water washing, filtration, and distillation to remove the solvent and excess epichlorohydrin.

[0024] Wherein: the extraction process includes standing for stratification, removing the lower layer of salt water solution, and obtaining the product solution.

[0025] Neutralization refers to the use of weak acidic substances to neutralize the alkaline substances remaining in the product solution. Suitable weak acidic substances as neutralizers include organic acids such as formic acid, acetic acid, oxalic acid, etc.; inorganic substances such as phosphoric acid, potassium dihydrogen phosphate, etc. The preferred neutralizing weak acid is phosphoric acid. Phosphoric acid is prepared into a low-concentration aqueous solution, and then added dropwise with stirring, and pH test paper is used to detect until pH = 7. The water washing process is to remove the salt remaining in the product solution.

[0026] Filtration refers to the use of filter aids such as diatomaceous earth, activated carbon, kaolin, etc., preferably activated carbon.

[0027] Distillation desolventization refers to the separation of solvent and product by distillation under heating and vacuum conditions. First, a water ring vacuum pump is used to remove most of the solvent at 50℃ / -0.09Mpa, and then a magnetic pump is used to remove the residual solvent at 90℃ / -0.095Mpa.

[0028] The technical parameter indicators of the tetrahydrophthalic acid diglycidyl epoxy resin prepared by the present invention are:

[0029] (1) Appearance: Colorless to light yellow transparent liquid,

[0030] (2) Epoxy equivalent (eq / 100g): 150-180,

[0031] (3) Viscosity (mpa.s, 25°C): 600-900,

[0032] (4) Color number (platinum-cobalt colorimetric): ≤40,

[0033] (5) Total chlorine (ppm): ≤8000

[0034] The specific analysis and detection methods refer to GB / T13657-92 "General Epoxy Resin Standard". The present invention has the following technical advantages:

[0035] (1) After the raw materials are added, the present invention uses a stirring belt to reduce pressure and evacuate the air in the reaction system as much as possible, and nitrogen is introduced for protection, which effectively prevents the oxygen in the air from affecting the reaction intermediates and the finished product during the reaction, ensuring that the finished product has a lower color number;

[0036] (2) In the ring-closing reaction stage, the present invention adopts a reduced pressure vacuum reflux dehydration method to timely remove the total moisture of the reaction system and recover the excess epichlorohydrin, thereby reducing the total chlorine content of the product to a lower level and reducing the consumption of epichlorohydrin, thereby reducing the cost;

[0037] (3) The tetrahydrophthalic acid diglycidyl ester epoxy resin synthesized by the present invention has the advantages of low unit consumption, stable process, simple extraction and water washing steps, low inorganic chlorine and organic chlorine content in the product, low color number of the finished product, etc., and is suitable for industrial production. DETAILED DESCRIPTION

[0038] The following examples are intended to illustrate the present invention but are not intended to limit the scope of the present invention.

[0039] Example 1

[0040] In a 1000mL four-necked flask equipped with an oil bath heating device, a magnetic stirrer, a thermometer, a condenser and a constant pressure dropping funnel, add 100g of tetrahydrophthalic anhydride and 300g of toluene solvent. The oil bath is heated to 80°C to dissolve tetrahydrophthalic anhydride in the toluene solvent, and then cooled to room temperature. Turn on the magnetic stirring, add 12g of water and 2.1g of tetrabutylammonium bromide catalyst, and the reaction system is evacuated for 2h before nitrogen protection is introduced. 180g of epichlorohydrin is added dropwise through a constant pressure dropping funnel for hydrolysis and esterification reaction, the reaction time is 4h, and the temperature is 90°C. The dropping process is slow dropping, and at the same time, pay attention to the temperature change, adjust the dropping speed, and prevent boiling. Then 115g of 45% liquid alkali solution (NaOH aqueous solution) is added dropwise through a constant pressure dropping funnel, the reaction time is 3h, and the temperature is 40°C. After the reaction process requirements are met, 100g toluene and 300g water are added to the reaction system for salt extraction, the salt temperature is 30°C, and the time is 1h. Stop stirring, let stand and separate the lower brine, and use 10% H3PO4 to adjust pH to 7. Add 300g water, wash again to separate the lower aqueous phase, and repeat twice. Use a sand funnel filled with activated carbon to filter to obtain a transparent colorless liquid. Under oil bath heating conditions, reduce pressure distillation to remove the solvent toluene and excess epichlorohydrin to obtain 170g of tetrahydrophthalic acid diglycidyl ester.

[0041] Product technical indicators:

[0042] (1) Appearance: Colorless to light yellow transparent liquid

[0043] (2) Epoxy equivalent (eq / 100g): 170

[0044] (3) Viscosity (mpa.s, 25°C): 656

[0045] (4) Color number (platinum-cobalt colorimetric): 20

[0046] (5)Total chlorine (ppm): 7260.

[0047] Example 2

[0048] In a 1000mL four-necked flask equipped with an oil bath heating device, magnetic stirring, thermometer, condenser and constant pressure dropping funnel, add 100g of tetrahydrophthalic anhydride and 400g of toluene solvent. The oil bath is heated to 80°C to dissolve tetrahydrophthalic anhydride in toluene solvent, and then cooled to room temperature. Turn on the magnetic stirring, add 12g of water and 2.1g of tetrabutylammonium bromide catalyst, and the reaction system is evacuated for 2h before nitrogen protection is introduced. 240g of epichlorohydrin is added dropwise through a constant pressure dropping funnel for hydrolysis and esterification reaction, the reaction time is 5h, and the temperature is 80°C. The dropping process is slow dropping, and at the same time, pay attention to the temperature change, adjust the dropping speed, and prevent boiling. Then 115g of 48% liquid alkali solution (NaOH aqueous solution) is added dropwise through a constant pressure dropping funnel, the reaction time is 3h, and the temperature is 50°C. After the reaction process requirements are met, 100g toluene and 300g water are added to the reaction system for salt extraction. The salt temperature is 30°C and the time is 1h. Stop stirring, let stand and separate the lower brine, and use 10% H3PO4 to adjust the pH to 7. Add 300g water, wash again to separate the lower aqueous phase, and repeat twice. Use a sand funnel filled with activated carbon to filter to obtain a transparent colorless liquid. Under oil bath heating conditions, remove the solvent toluene and excess epichlorohydrin by reduced pressure distillation to obtain 173g of tetrahydrophthalic acid diglycidyl ester.

[0049] Product technical indicators:

[0050] (1) Appearance: Colorless to light yellow transparent liquid

[0051] (2) Epoxy equivalent (eq / 100g): 174

[0052] (3) Viscosity (mpa.s, 25°C): 725

[0053] (4) Color number (platinum-cobalt colorimetric): 20

[0054] (5)Total chlorine (ppm): 7700.

[0055] Example 3

[0056] In a 1000mL four-necked flask equipped with an oil bath heating device, a magnetic stirrer, a thermometer, a condenser and a constant pressure dropping funnel, add 100g of tetrahydrophthalic anhydride and 300g of toluene solvent. The oil bath is heated to 80°C to dissolve tetrahydrophthalic anhydride in the toluene solvent, and then cooled to room temperature. Turn on the magnetic stirring, add 14g of water and 2.5g of hexadecyltrimethylammonium bromide catalyst, and the reaction system is evacuated for 2h before nitrogen protection is introduced. 300g of epichlorohydrin is added dropwise through a constant pressure dropping funnel for hydrolysis and esterification reaction, the reaction time is 5h, and the temperature is 80°C. The dropping process is slow dropping, and at the same time, pay attention to the temperature change, adjust the dropping speed, and prevent boiling. Then 121g of 50% liquid alkali solution (NaOH aqueous solution) is added dropwise through a constant pressure dropping funnel, the reaction time is 3h, and the temperature is 40°C. After the reaction process requirements are met, 100g toluene and 300g water are added to the reaction system for salt extraction, the salt temperature is 30°C, and the time is 1h. Stop stirring, let stand and separate the lower brine, and use 10% H3PO4 to adjust the pH to 7. Add 300g water, wash again to separate the lower aqueous phase, and repeat twice. Use a sand funnel filled with activated carbon to filter to obtain a transparent colorless liquid. Under oil bath heating conditions, reduce the pressure and distill to remove the solvent toluene and excess epichlorohydrin to obtain 169g of tetrahydrophthalic acid diglycidyl ester.

[0057] Product technical indicators:

[0058] (1) Appearance: Colorless to light yellow transparent liquid

[0059] (2) Epoxy equivalent (eq / 100g): 165

[0060] (3) Viscosity (mpa.s, 25°C): 690

[0061] (4) Color number (platinum-cobalt colorimetric): 20

[0062] (5)Total chlorine (ppm): 6500.

[0063] Example 4

[0064] In a 1000mL four-necked flask equipped with an oil bath heating device, a magnetic stirrer, a thermometer, a condenser and a constant pressure dropping funnel, add 100g of tetrahydrophthalic anhydride and 300g of toluene solvent. The oil bath is heated to 80°C to dissolve tetrahydrophthalic anhydride in the toluene solvent, and then cooled to room temperature. Turn on the magnetic stirring, add 12g of water and 2.1g of tetrabutylammonium bromide catalyst, and the reaction system is evacuated for 2h before nitrogen protection is introduced. 180g of epichlorohydrin is added dropwise through a constant pressure dropping funnel for hydrolysis and esterification reaction, the reaction time is 6h, and the temperature is 90°C. The dropping process is slow dropping, and at the same time, pay attention to the temperature change, adjust the dropping speed, and prevent boiling. Then 115g of 48% liquid alkali solution (NaOH aqueous solution) is added dropwise through a constant pressure dropping funnel, the reaction time is 2h, and the temperature is 60°C. After the reaction process requirements are met, 100g toluene and 300g water are added to the reaction system for salt extraction. The salt temperature is 30°C and the time is 1h. Stop stirring, let stand and separate the lower brine, and adjust the pH to 7 with 10% H3PO4. Add 300g water, wash again to separate the lower aqueous phase, and repeat twice. Use a sand funnel filled with activated carbon to filter to obtain a transparent colorless liquid. Under oil bath heating conditions, reduce the pressure and distill to remove the solvent toluene and excess epichlorohydrin to obtain 170g of tetrahydrophthalic acid diglycidyl ester.

[0065] Product technical indicators:

[0066] (1) Appearance: Colorless to light yellow transparent liquid

[0067] (2) Epoxy equivalent (eq / 100g): 168

[0068] (3) Viscosity (mpa.s, 25°C): 700

[0069] (4) Color number (platinum-cobalt colorimetric): 30

[0070] (5)Total chlorine (ppm): 6100.

[0071] Example 5

[0072] In a 1000mL four-necked flask equipped with an oil bath heating device, a magnetic stirrer, a thermometer, a condenser and a constant pressure dropping funnel, add 100g of tetrahydrophthalic anhydride and 300g of toluene solvent. The oil bath is heated to 80°C to dissolve tetrahydrophthalic anhydride in the toluene solvent, and then cooled to room temperature. Turn on the magnetic stirring, add 16g of water and 2.8g of hexadecyltrimethylammonium bromide catalyst, and the reaction system is evacuated for 2h before nitrogen protection is introduced. 360g of epichlorohydrin is added dropwise through a constant pressure dropping funnel for hydrolysis and esterification reaction, the reaction time is 5h, and the temperature is 80°C. The dropping process is slow dropping, and at the same time, pay attention to the temperature change, adjust the dropping speed, and prevent boiling. Then 121g of 50% liquid alkali solution (NaOH aqueous solution) is added dropwise through a constant pressure dropping funnel, the reaction time is 2h, and the temperature is 45°C. After the reaction process requirements are met, 100g toluene and 300g water are added to the reaction system for salt extraction. The salt temperature is 30°C and the time is 1h. Stop stirring, let stand and separate the lower brine, and adjust the pH to 7 with 10% H3PO4. Add 300g water, wash again and separate the lower aqueous phase, repeat twice. Use a sand funnel filled with activated carbon to filter to obtain a transparent colorless liquid. Under oil bath heating conditions, reduce the pressure and distill to remove the solvent toluene and excess epichlorohydrin to obtain 173g of tetrahydrophthalic acid diglycidyl ester.

[0073] Product technical indicators:

[0074] (1) Appearance: Colorless to light yellow transparent liquid

[0075] (2) Epoxy equivalent (eq / 100g): 169

[0076] (3) Viscosity (mpa.s, 25°C): 684

[0077] (4) Color number (platinum-cobalt colorimetric): 20

[0078] (5)Total chlorine (ppm): 6350.

[0079] Example 6

[0080] In a 1000mL four-necked flask equipped with an oil bath heating device, a magnetic stirrer, a thermometer, a condenser and a constant pressure dropping funnel, add 100g of tetrahydrophthalic anhydride and 400g of toluene solvent. The oil bath is heated to 80°C to dissolve tetrahydrophthalic anhydride in the toluene solvent, and then cooled to room temperature. Turn on the magnetic stirring, add 14g of water and 2.8g of tetrabutylammonium bromide catalyst, and the reaction system is evacuated for 2h before nitrogen protection is introduced. 360g of epichlorohydrin is added dropwise through a constant pressure dropping funnel for hydrolysis and esterification reaction, the reaction time is 3h, and the temperature is 90°C. The dropping process is slow dropping, and at the same time, pay attention to the temperature change, adjust the dropping speed, and prevent boiling. Then 121g of 50% liquid alkali solution (NaOH aqueous solution) is added dropwise through a constant pressure dropping funnel, the reaction time is 4h, and the temperature is 50°C. After the reaction process requirements are met, 100g toluene and 300g water are added to the reaction system for salt extraction. The salt temperature is 30°C and the time is 1h. Stop stirring, let stand and separate the lower brine, and adjust the pH to 7 with 10% H3PO4. Add 300g water, wash again to separate the lower aqueous phase, and repeat twice. Use a sand funnel filled with activated carbon to filter to obtain a transparent colorless liquid. Under oil bath heating conditions, reduce the pressure and distill to remove the solvent toluene and excess epichlorohydrin to obtain 170g of tetrahydrophthalic acid diglycidyl ester.

[0081] Product technical indicators:

[0082] (1) Appearance: Colorless to light yellow transparent liquid

[0083] (2) Epoxy equivalent (eq / 100g): 170

[0084] (3) Viscosity (mpa.s, 25°C): 715

[0085] (4) Color number (platinum-cobalt colorimetric): 30

[0086] (5)Total chlorine (ppm): 6200.

[0087] The above are only preferred specific implementation methods of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing diglycidyl tetrahydrophthalate, characterized in that: The steps include: A. Under normal pressure, heat tetrahydrophthalic anhydride to dissolve in an organic solvent, add water and quaternary ammonium salt as catalysts for the ring-opening step, and drop epihalohydrin to carry out esterification reaction. The ring-opening esterification reaction temperature is 40-130°C and the esterification time is 2-12h; B. Add 20-80% of liquid alkali to the first step esterification reaction solution to carry out ring-closing reaction. The ring-closing reaction time is 2-8 hours of heat preservation time, and the whole ring-closing reaction temperature is 35-100°C; C. Adding organic solvent to the saponification reaction solution of the second step, filtering, washing with water, dissolving salt and then treating to obtain tetrahydrophthalic acid diglycidyl ester epoxy resin.

2. The method for preparing diglycidyl tetrahydrophthalate according to claim 1, wherein: In step A, the epihalohydrin is selected from 1-chloro-2,3-epoxypropane or 1-bromo-2,3-epoxypropane; and the organic solvent is selected from toluene, methyl isobutyl ketone, and n-heptane.

3. The method for preparing diglycidyl tetrahydrophthalate according to claim 1, characterized in that: In step A, the quaternary ammonium salt is tetrabutylammonium bromide or hexadecyltrimethylammonium bromide, the molar ratio of the catalyst to tetrahydrophthalic anhydride is 0.01 to 0.08:1, and the molar ratio of the tetrahydrophthalic anhydride to water is 0.8 to 1.5:

1.

4. The method for preparing diglycidyl tetrahydrophthalate according to claim 1, characterized in that: In step A, the ring-opening esterification reaction temperature is 60-90° C., and the reaction time is 5-7 hours; and the molar ratio of epichlorohydrin to tetrahydrophthalic anhydride is greater than 3 / 1.

5. The method for preparing diglycidyl tetrahydrophthalate according to claim 1, characterized in that: In step B, the base is selected from NaOH, KOH, sodium methoxide, potassium methoxide, sodium ethoxide, potassium ethoxide; the ring-closing reaction temperature is 40-60° C., and the time is 2-4 hours.

6. The method for preparing diglycidyl tetrahydrophthalate according to claim 1, characterized in that: In step B, the amount of alkali added is at least 2 times the molar amount of tetrahydrophthalic anhydride.

7. The method for preparing diglycidyl tetrahydrophthalate according to claim 1, characterized in that: In step C, the organic solvent is toluene, and the amount of toluene added is the same mass as tetrahydrophthalic acid.

8. The method for preparing diglycidyl tetrahydrophthalate according to claim 1, characterized in that: In step C, the water washing and salt dissolving process has a salt dissolving temperature of 30 to 50° C. and a salt dissolving time of 1 to 2 hours.

9. The method for preparing diglycidyl tetrahydrophthalate according to claim 1, characterized in that: In step C, the post-treatment includes extraction of the product solution-brine solution, neutralization, water washing, filtration, and distillation to remove the solvent and excess epichlorohydrin.