Methods for converting hydrolyzable chlorine in epoxy resin into bound chlorine, epoxy resin materials containing bound chlorine and their curing methods

Abstract

This invention provides a method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, an epoxy resin material containing bound chlorine, and a curing method thereof, relating to the field of insulating materials technology. The method for converting hydrolyzable chlorine into bound chlorine is as follows: S1. Dissolve the epoxy resin containing hydrolyzable chlorine in an organic solvent and sequentially add a catalyst, an acid-binding agent, and a water-absorbing agent; S2. Allow the reaction system to react under an inert atmosphere or nitrogen; S3. Add the reaction reagent to the mixture under ice bath conditions and complete the conversion at room temperature. The epoxy resin material containing bound chlorine and its curing method are as follows: S1. Heat and stir the epoxy resin containing bound chlorine, a curing agent, and an accelerator until homogeneous to obtain a casting material; S2. Crosslink and cure the casting material to obtain the epoxy resin material containing bound chlorine. The epoxy resin material containing bound chlorine of this invention has superior electrical insulation properties. When applied in the field of electrical equipment manufacturing, it can significantly improve the reliability and stability of electrical equipment operating in humid environments.

Description

Technical Field

[0001] This invention relates to the field of insulating materials technology, specifically to a method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, epoxy resin materials containing bound chlorine, and their curing methods. Background Technology

[0002] Epoxy resin is a polymer containing two or more epoxy groups in its molecule. Due to its excellent insulation and mechanical properties, epoxy resin is a key material in the manufacture of electrical equipment such as large-capacity dry-type transformers, dry-type bushings, basin insulators, and saturated reactive electrical devices. The purity of epoxy resin significantly affects the reliability and stability of epoxy insulation materials used in electrical equipment under actual operating conditions. The hydrolyzable chlorine content is a key indicator of epoxy resin purity. When epoxy insulation materials are exposed to humid air, the hydrolyzable chlorine molecules in the epoxy resin undergo nucleophilic attack by water molecules, causing the C-Cl polar covalent bond to break, releasing freely moving chloride ions. Under the influence of an applied electric field, this accelerates the aging of the epoxy insulation material, leading to a decrease in its insulation performance and a shortened service life, ultimately causing electrical breakdown and insulation failure. Therefore, reducing the hydrolyzable chlorine content in epoxy resin and inhibiting the hydrolysis of hydrolyzable chlorine when epoxy resin operates in a humid environment for a long time is an effective means to improve the electrical insulation performance of epoxy resin.

[0003] Existing technologies can reduce the content of hydrolyzable chlorine in epoxy resins by addressing both the epoxy resin synthesis process and the purification process:

[0004] (1) Synthesis process: By avoiding the use of epichlorohydrin as a raw material for synthesizing epoxy resin, the chlorine content in epoxy resin is reduced from the source. For example, the Non-Halite catalyst used by Japan's JMTC can oxidize olefin raw materials with H2O2 without producing by-products under solvent-free conditions. However, this method is limited by the structure of the raw materials, and the types of resins produced are not needed by the electronics market. The price is high and it is difficult to be widely used.

[0005] (2) Purification process: Currently, secondary purification, molecular distillation and chromatographic purification are commonly used to purify epoxy resins with high chlorine content in order to further reduce the chlorine content in epoxy resins. For example, Chinese patent CN113248687A discloses that under negative pressure, water and organic solvents in the reaction system are removed to promote the removal of hydrogen chloride and ring closure of epoxy resins. However, these methods have high energy consumption, complicated processes, and increase the amount of strong alkali sodium hydroxide used, which greatly increases the production cost of epoxy resins and is not conducive to environmental protection. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, an epoxy resin material containing bound chlorine, and a curing method thereof. This solves the problem that hydrolyzable chlorine hydrolysis in a humid environment leads to a decrease in the insulation performance of epoxy resin, which in turn leads to a decrease in the operational reliability and stability of electrical equipment made from the epoxy resin.

[0008] (II) Technical Solution

[0009] One object of the present invention is to provide a method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, which is achieved through the following technical solution:

[0010] A method for converting hydrolyzable chlorine in epoxy resin into bound chlorine includes the following steps:

[0011] S1. Take epoxy resin containing hydrolyzable chlorine impurities, dissolve it in an organic solution, and add a catalyst, an acid-binding agent, and a water-absorbing agent sequentially into a reactor. Stir the mixture evenly at room temperature to obtain a mixed solution. The epoxy resin is an unextended epoxy resin molecule.

[0012] S2. Replace the air in the reaction vessel with inert gas and / or nitrogen 3 to 4 times to make the reaction system react in an inert gas and / or nitrogen atmosphere;

[0013] S3. Add the reaction reagent to the mixture under ice bath conditions and mix it evenly. After 0.4 to 0.6 hours, remove the ice bath and react at room temperature for 24 to 48 hours to finally convert the hydrolyzable chlorine in the epoxy resin into bound chlorine.

[0014] Preferably, the initial epoxy value of the epoxy resin is 0.28–0.95 mol / 100g;

[0015] It should be noted that the epoxy resin used in this application is selected from unextended single-molecule epoxy resins purchased from manufacturers. The initial epoxy value of the epoxy resin is 0.28–0.95 mol / 100g, and the main molecular chain does not contain hydroxyl groups. Therefore, the reaction reagents will not react with the main molecular chain of the epoxy resin, thereby avoiding damage to the molecular structure of the epoxy resin main chain.

[0016] Preferably, the reaction reagent is a small molecule organochlorosilane.

[0017] Preferably, the main reaction expression for the hydrolyzable chlorine conversion using small molecule organochlorosilanes is as follows:

[0018]

[0019] Where: X = -O- or -COO- or -N-;

[0020] When X = -O-, R = -CH2 or -CH(CH3)2 or -CH(CF3)2 or -SO2 or -C(C6H5)CH3;

[0021] R1 = -SiR2R3R4; R2 = -CH3 or -Ph or -CH = CH2.

[0022] Preferably, the hydrolyzable chlorine content in the epoxy resin is 1000-160000 ppm.

[0023] Preferably, the small molecule organochlorosilane is one or more combinations of methylchlorosilane, phenylchlorosilane, and vinylchlorosilane.

[0024] Preferably, the epoxy resin is one or more of glycidyl ether, glycidyl ester, and glycidyl amine epoxy resins.

[0025] Preferably, the catalyst is one or a combination of aliphatic amine catalysts, alicyclic amine catalysts, and aromatic amine catalysts.

[0026] Preferably, the acid-binding agent is one or a combination of two of the following: organic amine acid-binding agents and inorganic salt acid-binding agents.

[0027] Preferably, the organic solvent is one or a combination of dichloromethane, tetrahydrofuran, chloroform, dimethyl sulfoxide, diethyl ether, acetone, benzene, toluene, and xylene.

[0028] Preferably, the water-absorbing agent is one or more of 3A, 4A, and 5A molecular sieves.

[0029] Preferably, the mass ratio of epoxy resin, hydrolyzable chlorine, the small molecule organochlorosilane, the catalyst, and the acid-binding agent is 1000:(50-200):(16.82-38.50):(0.5-2):(0-5).

[0030] The second objective of this invention is to provide epoxy resin materials containing bound chlorine, which is achieved through the following technical solution:

[0031] The epoxy resin material containing bound chlorine includes an epoxy resin containing bound chlorine, a curing agent, and an accelerator, wherein the mass ratio of the epoxy resin containing bound chlorine, the curing agent, and the accelerator is (20-60):(10-40):(0.1-0.5).

[0032] Preferably, the mass ratio of the epoxy resin containing bound chlorine, the curing agent, and the accelerator is 40:35.2:0.24.

[0033] Preferably, the curing agent is one or more combinations of aromatic anhydrides, alicyclic anhydrides, and aliphatic anhydrides.

[0034] Preferably, the curing agent has an acid value of 600-750 mg KOH / g.

[0035] Preferably, the accelerator is one or a combination of amine accelerators, phenolic accelerators, imidazole and its salt accelerators, and boron trifluoride amine complex accelerators.

[0036] The third objective of this invention is to provide a curing method for epoxy resin materials containing bound chlorine, which is achieved through the following technical solution:

[0037] A method for curing epoxy resin materials containing bound chlorine includes the following steps:

[0038] S1. An epoxy resin containing bound chlorine, a curing agent, and an accelerator are heated and stirred evenly under vacuum conditions to obtain a casting material;

[0039] S2. The casting material is poured into the mold and cross-linked and cured to obtain an epoxy resin material containing bound chlorine.

[0040] Preferably, in step S1, the heating temperature for stirring the epoxy resin containing bound chlorine, the curing agent, and the accelerator under vacuum heating conditions is 60–120°C.

[0041] Preferably, the crosslinking curing in step S2 specifically involves pre-curing for 2–12 hours and post-curing for 6–30 hours.

[0042] Preferably, the pre-curing temperature is 60–100°C and the post-curing temperature is 100–140°C.

[0043] (III) Beneficial Effects

[0044] This invention provides a method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, an epoxy resin material containing bound chlorine, and a curing method thereof. Compared with the prior art, it has the following advantages:

[0045] Unextended single-molecule epoxy resin purchased from the manufacturer is treated to convert hydrolyzable chlorine impurities into bound chlorine. Since the epoxy resin has not undergone chain extension, its degree of polymerization (n) is 0, meaning the main chain does not contain hydroxyl groups. This prevents small-molecule organochlorosilanes from reacting with the epoxy resin main chain, thus ensuring the integrity of the epoxy resin main chain molecular skeleton. The initial epoxy value of the epoxy resin of this invention is between 0.28 and 0.95 mol / 100g. This type of epoxy resin is widely used in the preparation of high-end electrical equipment.

[0046] Small-molecule organochlorosilanes chemically couple only with the active functional groups of hydroxyl groups in the hydrolyzable chlorine impurities of epoxy resin, converting the hydrolyzable chlorine into bound chlorine. Since the α-position of the terminal chlorine atom in the bound chlorine no longer contains an active hydroxyl group, the stability of the terminal isolated chloromethyl group increases. Simultaneously, the increased steric hindrance at the ortho position hinders the nucleophilic attack of the terminal chloromethyl group by H₂O molecules. This preserves the original excellent properties of the epoxy resin without altering its basic molecular framework. Furthermore, a bound chlorine molecule with Si-O bonds is constructed within the epoxy resin system. Its surface enrichment promotes the dissipation of surface charge in the epoxy resin material, suppresses electric field distortion caused by surface charge accumulation, and improves the electrical insulation properties of the epoxy resin. Therefore, by utilizing organosilicon to convert the hydrolyzable chlorine in epoxy resin into bound chlorine, the reliability and stability of electrical equipment operating in humid environments are significantly improved. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 The NMR spectrum of unconverted hydrolyzable epoxy resin is shown in the figure. Figure 1 (b) is Figure 1 (a) Enlarged view of the circled area;

[0049] Figure 2 The NMR 13C spectrum of unconverted hydrolyzable chlorine epoxy resin is shown below. Figure 2 (d) is Figure 2 (c) Enlarged view of the circled area;

[0050] Figure 3 The first embodiment of this invention uses a small molecule organochlorosilane to convert hydrolyzable chlorine into bound chlorine in the 1H NMR spectrum of the epoxy resin. Figure 3 (f) is Figure 3 (e) Enlarged view of the circled area;

[0051] Figure 4 The carbon NMR spectrum of the epoxy resin after hydrolyzable chlorine is converted into bound chlorine using a small molecule organochlorosilane in Example 1 of this invention is shown below. Figure 4 (h) is Figure 4 (g) Enlarged view of the circled area;

[0052] Figure 5This is a comparison chart of the volume / surface resistivity of the epoxy resin materials prepared in Example 1 and Comparative Example 1 of the present invention;

[0053] Figure 6 This is a comparison diagram of the volume / surface resistivity of epoxy resin materials prepared in Example 1 and Comparative Example 1 after hygrothermal aging.

[0054] Figure 7 This is a comparison diagram of the dielectric constants of the epoxy resin materials prepared in Example 1 and Comparative Example 1 of the present invention;

[0055] Figure 8 This is a comparison diagram of the dielectric constants of the epoxy resin materials prepared in Example 1 and Comparative Example 1 after hygrothermal aging.

[0056] Figure 9 This is a comparison diagram of the Weibull distribution of the breakdown field strength of the epoxy resin materials prepared in Example 1 and Comparative Example 1 of the present invention;

[0057] Figure 10 This is a comparison diagram of the Weibull distribution of the breakdown field strength of the epoxy resin materials prepared in Example 1 and Comparative Example 1 after hygrothermal aging.

[0058] Figure 11 This is a comparison chart of the pressure resistance time of epoxy resin materials prepared in Example 1 and Comparative Example 1 after damp heat aging. Detailed Implementation

[0059] 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 are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] This application provides a method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, an epoxy resin material containing bound chlorine, and a curing method thereof. This avoids the problem that hydrolyzable chlorine is prone to hydrolysis in humid environments, leading to a decrease in the insulation performance of epoxy resin and a decrease in the reliability and stability of electrical equipment manufactured from the epoxy resin. This achieves an improvement in the insulation performance of epoxy resin and significantly enhances the reliability and stability of electrical equipment manufactured from the epoxy resin in humid environments.

[0061] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0062] Example 1

[0063] A method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, and then curing the conversion product:

[0064] S1. Take 600g of bisphenol A type epoxy resin with a hydrolyzable chlorine content of 80000ppm and an epoxy value of 0.588 and dissolve it in a reaction vessel containing 3000mL of dichloromethane solution. Add 0.6g of 4-dimethylaminopyridine, 3g of sodium carbonate and 4A type molecular sieve in sequence, and stir evenly at room temperature to obtain a mixed solution.

[0065] S2. Use nitrogen to replace the air in the reaction vessel three times to make the entire reaction system in a nitrogen atmosphere; then place the reaction vessel in an ice bath. When the reaction system cools to 0°C, slowly add 11g of trimethylchlorosilane through a syringe. Half an hour after the addition is completed, remove the ice bath and stir the reaction system at room temperature for 36 hours.

[0066] S3. After the reaction is complete, saturated NH4Cl solution is added to quench the reaction. The mixture is washed multiple times with saturated NaHCO3 solution, and then the saturated NaHCO3 solution is extracted with ethyl acetate. The organic phases are combined, dried, filtered, and concentrated to obtain epoxy resin containing bound chlorine.

[0067] S4. Take 280g of epoxy resin containing bound chlorine, add 209.66g of methyltetrahydrophthalic anhydride and 1.68g of tris-(dimethylaminomethyl)phenol, mix evenly, and stir in a vacuum reactor at 80℃ for 20min at a speed of 500r / min to obtain casting material.

[0068] S5. Pour the casting material into the mold, let it stand at 80°C for 3 hours, and then continue to stand at 120°C for 20 hours to obtain an epoxy resin material with a diameter of 100 mm and a thickness of 1 mm that can be hydrolyzed into bound chlorine.

[0069] The epoxy resin material that converts hydrolyzable chlorine into bound chlorine was placed in a damp heat aging chamber. The damp heat aging conditions were in accordance with the JESD22-A102C standard (evaluation of non-hermetic IC packaged devices). After 48 hours of damp heat aging, the epoxy resin material that converts hydrolyzable chlorine into bound chlorine was taken out for performance testing.

[0070] Example 2

[0071] A method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, and then curing the conversion product:

[0072] S1. Take 600g of bisphenol A type epoxy resin with a hydrolyzable chlorine content of 40000ppm and an epoxy value of 0.588 and dissolve it in a reaction vessel containing 3000mL of dichloromethane solution. Add 0.3g of 4-dimethylaminopyridine, 1.5g of sodium carbonate and 4A type molecular sieve in sequence, and stir evenly at room temperature to obtain a mixed solution.

[0073] S2. Use argon to replace the air in the reaction vessel three times to make the entire reaction system in an argon atmosphere; then place the reaction vessel in an ice bath. When the reaction system cools to 0°C, slowly add 5.5g of trimethylchlorosilane through a syringe. Half an hour after the addition is completed, remove the ice bath and stir the reaction system at room temperature for 36 hours.

[0074] S3. After the reaction is complete, saturated NH4Cl solution is added to quench the reaction, and the mixture is washed multiple times with saturated NaHCO3 solution. The saturated NaHCO3 solution is then extracted with ethyl acetate. The organic phases are combined, dried, filtered, and concentrated to obtain an epoxy resin containing bound chlorine.

[0075] S4. Take 280g of epoxy resin containing bound chlorine, add 221.9g of methyltetrahydrophthalic anhydride and 1.68g of tris-(dimethylaminomethyl)phenol, mix evenly, and stir in a vacuum reactor at 80℃ and 500r / min for 20min to obtain casting material.

[0076] S5. Pour the casting material into the mold, let it stand at 80°C for 3 hours, and then continue to stand at 120°C for 20 hours to obtain an epoxy resin material with a diameter of 100 mm and a thickness of 1 mm that can be hydrolyzed into bound chlorine.

[0077] Example 3

[0078] A method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, and then curing the conversion product:

[0079] S1. Take 600g of bisphenol A type epoxy resin with a hydrolyzable chlorine content of 120000ppm and an epoxy value of 0.588 and dissolve it in a reaction vessel containing 3000mL of dichloromethane solution. Add 0.3g of 4-dimethylaminopyridine, 4.5g of sodium carbonate and 4A type molecular sieve in sequence, and stir evenly at room temperature to obtain a mixed solution.

[0080] S2. Use nitrogen to replace the air in the reaction vessel three times to make the entire reaction system in a nitrogen atmosphere; then place the reaction vessel in an ice bath. When the reaction system cools to 0°C, slowly add 16.5g of trimethylchlorosilane through a syringe. Remove the ice bath half an hour after the addition is complete and stir the reaction system at room temperature for 36 hours.

[0081] S3. After the reaction is complete, saturated NH4Cl solution is added to quench the reaction, and the mixture is washed multiple times with saturated NaHCO3 solution. The saturated NaHCO3 solution is then extracted with ethyl acetate. The organic phases are combined, dried, filtered, and concentrated to obtain an epoxy resin containing bound chlorine.

[0082] S4. Take 280g of epoxy resin containing bound chlorine, add 203.8g of methyltetrahydrophthalic anhydride and 1.68g of tris-(dimethylaminomethyl)phenol, mix evenly, and stir in a vacuum reactor at 80℃ and 500r / min for 20min to obtain casting material.

[0083] S5. Pour the casting material into the mold, let it stand at 80°C for 3 hours, and then continue to stand at 120°C for 20 hours to obtain an epoxy resin material with a diameter of 100 mm and a thickness of 1 mm that can be hydrolyzed into bound chlorine.

[0084] Example 4

[0085] A method for converting hydrolyzable chlorine in epoxy resin into bound chlorine, and then curing the conversion product:

[0086] S1. Take 600g of bisphenol A type epoxy resin with a hydrolyzable chlorine content of 160000ppm and an epoxy value of 0.588 and dissolve it in a reaction vessel containing 3000mL of dichloromethane solution. Then add 1.2g of 4-dimethylaminopyridine, 6g of sodium carbonate and 4A type molecular sieve in sequence and stir evenly at room temperature to obtain a mixed solution.

[0087] S2. Use nitrogen to replace the air in the reaction vessel three times to make the entire reaction system in a nitrogen atmosphere; then place the reaction vessel in an ice bath. When the reaction system cools to 0°C, slowly add 22g of trimethylchlorosilane through a syringe. Half an hour after the addition is completed, remove the ice bath and stir the reaction system at room temperature for 36 hours.

[0088] S3. After the reaction is complete, saturated NH4Cl solution is added to quench the reaction, and the mixture is washed multiple times with saturated NaHCO3 solution. The saturated NaHCO3 solution is then extracted with ethyl acetate. The organic phases are combined, dried, filtered, and concentrated to obtain an epoxy resin containing bound chlorine.

[0089] S4. Take 280g of epoxy resin containing bound chlorine, add 190.7g of methyltetrahydrophthalic anhydride and 1.68g of tris-(dimethylaminomethyl)phenol, mix evenly, and stir in a vacuum reactor at 80℃ and 500r / min for 20min to obtain casting material.

[0090] S5. Pour the casting material into the mold, let it stand at 80°C for 3 hours, and then continue to stand at 120°C for 20 hours to obtain an epoxy resin material with a diameter of 100 mm and a thickness of 1 mm that can be hydrolyzed into bound chlorine.

[0091] Comparative Example 1

[0092] Curing methods for epoxy resins that do not undergo hydrolytic chlorine conversion:

[0093] 392g of bisphenol A type epoxy resin with a hydrolyzable chlorine content of 80,000ppm was mixed with 312g of methyltetrahydrophthalic anhydride and 2.35g of tris-(dimethylaminomethyl)phenol. The mixture was stirred in a vacuum reactor at 80°C and 500r / min for 20min to obtain a casting material. The uniformly dispersed casting material was then poured into a mold and allowed to stand at 80°C for 3h. After standing at 120°C for another 20h, an epoxy resin material with a diameter of 100mm and a thickness of 1mm without undergoing hydrolyzable chlorine conversion was obtained.

[0094] Unconverted hydrolyzable chlorine-containing epoxy resin material was placed in a damp heat aging chamber. The damp heat aging conditions were in accordance with the JESD22-A102C standard (evaluation of non-hermetic IC packaged devices). After 48 hours of damp heat aging, the epoxy resin material that had not undergone hydrolyzable chlorine conversion was taken out for performance testing.

[0095] Performance testing

[0096] 1. Epoxy value determination test of converted epoxy resin

[0097] The epoxy values ​​of the epoxy resins in Examples 1-4 after hydrolyzable chlorine was converted into bound chlorine were determined according to the test requirements of GB-T1677-2008. The test results are recorded in Table 1. The formula for calculating the epoxy value of epoxy resin is as follows:

[0098]

[0099] In the formula, V is the volume of standard sodium hydroxide solution consumed by the sample, in ml;

[0100] V0—The volume of standard sodium hydroxide solution consumed by the blank sample, in ml;

[0101] C – Equivalent concentration of sodium hydroxide standard solution, mol / L;

[0102] W – Sample mass, g.

[0103] Table 1 - Epoxy values ​​of the converted epoxy resins in Examples 1-4

[0104] Example Theoretical epoxy value Measured epoxy value Example 1 0.5110 0.5006 Example 2 0.5433 0.5389 Example 3 0.4884 0.4866 Example 4 0.4567 0.4553

[0105] 2. The proton NMR spectrum of the unconverted hydrolyzable epoxy resin was analyzed, and the results are as follows: Figure 1 As shown;

[0106] The carbon NMR spectrum of the unconverted hydrolyzable epoxy resin was analyzed, and the results are as follows: Figure 2 As shown;

[0107] The proton NMR spectrum of the epoxy resin obtained by converting hydrolyzable chlorine into bound chlorine using small molecule chlorosilane in Example 1 was analyzed, and the results are as follows: Figure 3 As shown;

[0108] The carbon NMR spectrum of the epoxy resin obtained by converting hydrolyzable chlorine into bound chlorine using small molecule chlorosilane in Example 1 was analyzed, and the results are as follows: Figure 4 As shown.

[0109] 3. Volume / Surface Resistivity Test

[0110] The test method is as follows: under the conditions of 20℃ temperature and 50% relative humidity, the volume / surface resistivity test is carried out using a ZC36 high resistance meter.

[0111] Volume / surface resistivity tests were performed on the epoxy resin material containing bound chlorine prepared in Example 1, the epoxy resin material containing hydrolyzable chlorine prepared in Comparative Example 1, and the epoxy resin material after the damp heat aging test in the Examples. The test results are compared as follows: Figure 5 and Figure 6 As shown.

[0112] 4. Dielectric constant test

[0113] The test method is as follows: According to standard IEC 60250:1969, a 1000V / 50Hz AC voltage is applied using a high-voltage bridge (QS 87) at power frequency to conduct a dielectric constant test.

[0114] The dielectric constants of the epoxy resin material containing bound chlorine prepared in Example 1 and the epoxy resin material containing hydrolyzable chlorine prepared in Comparative Example 1, as well as the epoxy resin material after a damp heat aging test, were tested. The test results are compared as follows: Figure 7 and Figure 8 As shown.

[0115] 5. Power Frequency AC Breakdown Field Strength Test

[0116] The test method is as follows: According to the GB / T1408.1-2016 test standard, the test power supply is a high-voltage test transformer with a frequency of 50Hz, and the measuring electrode system consists of two identical spherical electrodes with a diameter of 20mm. The power frequency AC breakdown field strength test is carried out.

[0117] The epoxy resin material containing bound chlorine prepared in Example 1 and the epoxy resin material containing hydrolyzable chlorine prepared in Comparative Example 1, as well as the epoxy resin material after damp heat aging, were subjected to power frequency AC breakdown field strength tests. The test results are compared as follows: Figure 9 and Figure 10 As shown.

[0118] 6. Pressure resistance time test

[0119] The test method is as follows: In an environment with SF6 gas at 0.2 MPa, the temperature and humidity are 25℃ and 50% RH, respectively. The test needle-plate electrode has a diameter of 1 mm, a radius of curvature of 50 μm, and an angle of 30° with the sample. The plate electrode is a 40×30×5 mm copper electrode. The rated AC voltage is 0.9 times the AC breakdown voltage, and a withstand voltage time test is conducted.

[0120] The pressure resistance time of the epoxy resin material containing bound chlorine prepared in Example 1 and the epoxy resin material containing hydrolyzable chlorine prepared in Comparative Example 1 after wet heat aging were tested. The test results were compared with those of the epoxy resin material containing bound chlorine prepared in Comparative Example 1. Figure 11 As shown.

[0121] Experimental data analysis

[0122] As shown in Table 1, the theoretical epoxy value of the converted epoxy resin is basically the same as the measured value, indicating that the use of small-molecule chlorosilanes can effectively convert the hydrolyzable chlorine in the resin into bound chlorine, thereby further improving the insulation performance of the epoxy resin. At the same time, the small-molecule chlorosilanes do not affect the basic molecular skeleton and epoxy groups of the epoxy resin when reacting with the hydrolyzable chlorine in the epoxy resin.

[0123] from Figures 1-4 It can be seen that the small molecule organochlorosilane and the hydrolyzable chlorine molecule were chemically coupled. After coupling, the silanyl methyl segment on the bound chlorine molecule caused the hydrogen at the α position on both sides of the oxygen-bonded carbon to shift to a higher field, and the peak splitting shape also changed significantly.

[0124] Furthermore, in the 1H and 1C NMR spectra of epoxy resin before and after the conversion of hydrolyzable chlorine to bound chlorine, singlet peaks of hydrogen and carbon on the silanyl methyl group appeared near the high-field chemical shift of 0 ppm, respectively, due to the methyl group in the small molecule chlorosilane being connected to the silicon atom. This indicates that the small molecule chlorosilane successfully converted the hydrolyzable chlorine in the epoxy resin into bound chlorine.

[0125] from Figure 5 and Figure 6It can be seen that the volume / surface resistivity of the epoxy resin material after organosilicon conversion of hydrolyzable chlorine to bound chlorine in Example 1 is lower than that of the epoxy resin material without organosilicon conversion. This proves that after converting the hydrolyzable chlorine molecules in the epoxy resin system into bound chlorine molecules with Si-O bonds, the method utilizes the surface enrichment effect of siloxane molecules to reduce the volume / surface resistivity of the epoxy material and accelerate the charge dissipation of the epoxy resin material. After damp heat aging, the volume / surface resistivity of the epoxy resin material containing hydrolyzable chlorine in Example 1 is lower than that of the epoxy resin material after organosilicon conversion of hydrolyzable chlorine to bound chlorine. This also verifies that converting the hydrolyzable chlorine in the epoxy resin into bound chlorine can improve the insulation performance of the epoxy resin material after damp heat aging.

[0126] from Figure 7 and Figure 8 It can be seen that, before and after damp heat aging in Example 1, the dielectric constant of the epoxy resin material after the organosilicon is converted into hydrolyzable chlorine to bound chlorine is lower under power frequency conditions than that of the epoxy resin material without organosilicon conversion. This indicates that the conversion of hydrolyzable chlorine in the organosilicon resin into bound chlorine reduces the dielectric constant of the epoxy resin material before and after damp heat aging.

[0127] from Figure 9 and Figure 10 It can be seen that, before and after damp heat aging in Example 1, the breakdown field strength of the epoxy resin material after the organosilicon is converted into hydrolyzable chlorine is higher than that of the epoxy resin material without organosilicon conversion, thereby improving the short-time insulation performance of the epoxy resin material before and after damp heat aging.

[0128] from Figure 11 It can be seen that, after damp heat aging in Example 1, the pressure resistance time of the epoxy resin material after the organosilicon is converted into hydrolyzable chlorine to bound chlorine is longer than that of the epoxy resin material without conversion, thereby improving the long-term insulation performance of the epoxy resin material after damp heat aging, and ultimately achieving the purpose of improving the insulation performance of the epoxy resin material.

[0129] In summary, compared with existing technologies, it has the following beneficial effects:

[0130] Unextended single-molecule epoxy resin purchased from the manufacturer is treated to convert hydrolyzable chlorine impurities into bound chlorine. Since the epoxy resin has not undergone chain extension, its degree of polymerization (n) is 0, meaning the main chain does not contain hydroxyl groups. This prevents small-molecule organochlorosilanes from reacting with the epoxy resin main chain, thus ensuring the integrity of the epoxy resin main chain molecular skeleton. The initial epoxy value of the epoxy resin of this invention is between 0.28 and 0.95 mol / 100g. This type of epoxy resin is widely used in the manufacturing of high-end electrical equipment.

[0131] Small-molecule organochlorosilanes chemically couple only with the active functional groups of hydrolyzable chlorine impurities in epoxy resins, converting hydrolyzable chlorine into bound chlorine. Since the α-position of the terminal chlorine atom in the bound chlorine no longer contains an active hydroxyl group, the stability of the isolated terminal chloromethyl group increases. Simultaneously, the increased steric hindrance at the ortho position hinders the nucleophilic attack of H₂O molecules on the terminal chloromethyl group. This preserves the original excellent properties of the epoxy resin without altering its basic molecular framework. Furthermore, bound chlorine molecules with Si-O bonds are constructed within the epoxy resin system. Their surface enrichment promotes the dissipation of surface charge in the epoxy resin material, suppresses electric field distortion caused by surface charge accumulation, and improves the electrical insulation performance of the epoxy resin. Therefore, by utilizing organosilicon to convert hydrolyzable chlorine in epoxy resins into bound chlorine, the reliability and stability of electrical equipment operating in humid environments are significantly improved.

[0132] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0133] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. Process for converting hydrolyzable chlorine in an epoxy resin into bound chlorine, characterized in that, The method comprises the following steps: S1. Dissolving epoxy resin containing hydrolyzable chlorine impurities in an organic solution and sequentially adding a catalyst, an acid-binding agent and a water absorbent into a reactor, stirring uniformly at room temperature to obtain a mixed solution, wherein the epoxy resin is an un-chained epoxy resin molecule; S2. Replacing air in the reaction container with inert gas and / or nitrogen for 3-4 times to make the reaction system in an inert gas and / or nitrogen atmosphere for reaction; S3. Adding a small-molecule organic chlorosilane to the mixed solution under ice bath condition, stirring uniformly, removing the ice bath after 0.4-0.6 h, and reacting at room temperature for 24-48 h, so as to finally convert the hydrolyzable chlorine in the epoxy resin into combined chlorine; The main reaction expression for converting the hydrolyzable chlorine using the small-molecule organic chlorosilane is as follows: Wherein, X=-O- or -COO-; When X=-O-, R=-CH2 or -CH(CH3)2 or -CH(CF3)2 or -SO2 or -C(C6H5)CH3; R1=-SiR2R3R4; R2=-CH3; R3=-CH3; R4=-CH3; The small-molecule organic chlorosilane is trimethylchlorosilane.

2. The method of converting hydrolyzable chlorine in an epoxy resin to bound chlorine according to claim 1, wherein, The content of the hydrolyzable chlorine in the epoxy resin is 1000-160000 ppm.

3. The method of converting hydrolyzable chlorine in an epoxy resin to bound chlorine according to claim 1, wherein, The epoxy resin is one or a combination of glycidyl ether, glycidyl ester and glycidyl amine epoxy resin.

4. The method of converting hydrolyzable chlorine in an epoxy resin to bound chlorine according to Claim 1 wherein, The catalyst is one or a combination of aliphatic amine catalyst, alicyclic amine catalyst and aromatic amine catalyst.

5. The method of converting hydrolyzable chlorine in an epoxy resin to bound chlorine of claim 1 wherein, The acid-binding agent is one or a combination of organic amine acid-binding agent and inorganic salt acid-binding agent.

6. The method of converting hydrolyzable chlorine in an epoxy resin to bound chlorine of claim 1 wherein, The organic solvent is one or a combination of dichloromethane, tetrahydrofuran, chloroform, dimethyl sulfoxide, diethyl ether, acetone, benzene, toluene and xylene.

7. The method of converting hydrolyzable chlorine in an epoxy resin to bound chlorine of claim 1 wherein, The water absorbent is one or a combination of 3A, 4A and 5A molecular sieve.

8. The method of converting hydrolyzable chlorine in an epoxy resin to bound chlorine of claim 1 wherein, The mass ratio of the epoxy resin, the hydrolyzable chlorine, the small-molecule organic chlorosilane, the catalyst and the acid-binding agent is 1000:(50-200):(16.82-38.50):(0.5-2):(0-5).

9. An epoxy resin material containing bound chlorine, characterized in that, The method comprises the following steps:

10. The epoxy material containing bound chlorine of claim 9, wherein, The method comprises the following steps:

11. The epoxy material containing bound chlorine of claim 9, wherein, The mass ratio of the epoxy resin containing combined chlorine, the curing agent and the accelerator is (20-60):(10-40):(0.1-0.5).

12. The epoxy material containing bound chlorine of claim 11, wherein, The mass ratio of the epoxy resin containing combined chlorine, the curing agent and the accelerator is 40:35.2:0.

24.

13. The epoxy material containing bound chlorine of claim 9, wherein, The curing agent is one or a combination of aromatic anhydride, alicyclic anhydride and aliphatic anhydride.

14. The method of curing a chloro-comprising epoxy resin material according to any one of claims 9 to 13, characterized in that: The acid value of the curing agent is 600-750 mgKOH / g. The accelerator is one or a combination of amine accelerator, phenolic accelerator, imidazole and its salt accelerator and boron trifluoride amine complex accelerator. The method comprises the following steps: S1. Heating and stirring the epoxy resin containing combined chlorine, the curing agent and the accelerator under vacuum condition to obtain a casting material; S2. Pouring the casting material into a mold, and obtaining an epoxy resin material containing bound chlorine after cross-linking and curing.

15. The method of curing a chloro-comprising epoxy resin material according to claim 14, wherein The heating temperature in the step S1 of stirring the epoxy resin containing bound chlorine, the curing agent and the accelerator under vacuum heating conditions is 60-120°C.

16. The method of curing a chloro-comprising epoxy resin material according to claim 14, wherein The cross-linking and curing in the step S2 is specifically pre-curing for 2-12 hours and post-curing for 6-30 hours.

17. The method of curing a chloro-comprising epoxy resin material according to claim 16, wherein The pre-curing temperature is 60-100°C, and the post-curing temperature is 100-140°C.

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