Imine modified unsaturated polyester resin and preparation method thereof, and insulating paint and preparation method thereof

Abstract

The invention discloses imine modified unsaturated polyester resin and a preparation method thereof, and insulating paint and a preparation method thereof. The imine-modified unsaturated polyester resin comprises a compound shown in a formula I, the molecular weight of the imine-modified unsaturated polyester resin is 600-1200, R4 at different positions independently represent active double bonds (carbon-carbon double bonds) contained in an end-capping part in the imgabs 1 # imine-modified unsaturated polyester resin, and when the imine-modified unsaturated polyester resin is used in insulating paint, the imine-modified unsaturated polyester resin can be used for insulating paint. Active double bonds can participate in reaction in the cross-linking and curing process of the insulating paint, and the curing and cross-linking density of the insulating paint is increased, so that the heat resistance of the cured insulating paint is improved; moreover, the imine-modified unsaturated polyester resin has proper molecular weight, the viscosity is not too high, subsequent dilution is facilitated, and the dosage of the reactive diluent is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of insulating varnishes, and in particular to an imide-modified unsaturated polyester resin and a preparation method thereof, an insulating varnish and a preparation method thereof. Background Art

[0002] The current development trend of motors and electrical appliances is gradually moving towards high power, compactness, light weight, high voltage and high speed, which leads to slow natural heat dissipation and high temperature rise, thus putting forward higher requirements on the heat resistance level of the insulating resin used. Conventional epoxy resin and unsaturated polyester insulating resin can no longer meet the requirements, while imide-modified unsaturated polyester resin can be used as insulating resin with heat resistance level H and above due to its good heat resistance.

[0003] However, the heat resistance of the currently commonly used imine-modified unsaturated polyester resins still needs to be further improved. Summary of the invention

[0004] The present application aims to alleviate or solve at least one of the above-mentioned problems to at least some extent.

[0005] In one aspect of the present application, the present application provides an imine-modified unsaturated polyester resin. In some embodiments of the present application, the imine-modified unsaturated polyester resin includes a compound shown in Formula I, and the molecular weight of the imine-modified unsaturated polyester resin is 600 to 1200.

[0006] Among them, R1 is or C2-C4 alkylene, R2 at different positions are independently C2-C6 alkylene or R3 at different positions is independently C1-C4 alkylene, and R4 at different positions is independently

[0007] Therefore, the end-capping part of the imine-modified unsaturated polyester resin contains active double bonds (carbon-carbon double bonds). When it is used in insulating varnish, the active double bonds can participate in the reaction during the cross-linking and curing process of the insulating varnish, increase the curing cross-linking density of the insulating varnish, and thus improve the heat resistance of the insulating varnish (imine-modified unsaturated polyester insulating resin) after curing; and, the imine-modified unsaturated polyester resin has a suitable molecular weight and the viscosity is not too high, which is convenient for subsequent dilution and helps to reduce the amount of reactive diluent.

[0008] In some embodiments of the present application, the imine-modified unsaturated polyester resin satisfies at least one of the following conditions: R1 is R2 at different positions is independently

[0009] R3 at different positions is independently

[0010]

[0011] In some embodiments of the present application, the imine-modified unsaturated polyester resin satisfies at least one of the following conditions: R1 is R2 at different positions is independently R3 is

[0012] In another aspect of the present application, the present application proposes a method for preparing an imine-modified unsaturated polyester resin. In some embodiments of the present application, the method for preparing an imine-modified unsaturated polyester resin comprises: placing 20 to 45 parts by weight of a polyol, 10 to 22 parts by weight of a saturated dibasic acid or anhydride, and 20 to 29 parts by weight of an unsaturated dibasic acid or anhydride in a reaction container, reacting at a first temperature for a first time to obtain a first mixture; adding 15 to 30 parts by weight of a capping agent to the first mixture, reacting at a second temperature for a second time to obtain a second mixture; evacuating the reaction system, allowing the second mixture to continue to react at a third temperature for a third time to obtain an imine-modified unsaturated polyester resin; wherein the capping agent comprises R3 is a C1-C4 alkylene group, R4 is

[0013] Therefore, the end-capping agent can end-cap the condensation polymerization reaction. In addition, when the polyester resin is used in the insulating varnish, the active double bonds (carbon-carbon double bonds) contained in the end-capping agent can participate in the reaction during the cross-linking and curing of the insulating varnish, promote the cross-linking and curing of the insulating varnish, and help increase the curing cross-linking density of the insulating varnish, thereby helping to improve the heat resistance of the insulating varnish.

[0014] In some embodiments of the present application, the method for preparing an imine-modified unsaturated polyester resin satisfies at least one of the following conditions: the polyol includes one or more of ethylene glycol, propylene glycol, 1,2-propylene glycol, butanediol, neopentyl glycol, hexanediol, and tris(2-hydroxyethyl)isocyanurate; the saturated dibasic acid or anhydride includes one or more of phthalic acid, phthalic anhydride, isophthalic acid, succinic acid, glutaric acid, adipic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; the unsaturated dibasic acid or anhydride includes one or more of maleic anhydride and maleic acid; R3 is

[0015]

[0016] In some embodiments of the present application, the capping agent includes one or more of N-hydroxyethylmaleimide, N-hydroxyethylcitraconimide, and N-hydroxyethylitaconimide.

[0017] In some embodiments of the present application, the method for preparing an imide-modified unsaturated polyester resin satisfies at least one of the following conditions: the first temperature is 170°C to 200°C; the first time is 5 to 7 hours; the second temperature is 170°C to 200°C; the second time is 5 to 7 hours; the third temperature is 170°C to 200°C; the third time is 5 to 7 hours.

[0018] In some embodiments of the present application, the capping agent further includes trimethylolpropane diallyl ether.

[0019] In some embodiments of the present application, the acid value of the imine-modified unsaturated polyester resin is 20-32 mgKOH / g.

[0020] In another aspect of the present application, the present application proposes an insulating varnish. In some embodiments of the present application, the insulating varnish includes: 50 to 60 parts by weight of an imine-modified unsaturated polyester resin, the imine-modified unsaturated polyester resin is the imine-modified unsaturated polyester resin described above, or the imine-modified unsaturated polyester resin is an imine-modified unsaturated polyester resin prepared by the method described above; 37 to 49 parts by weight of an active diluent; 1 to 3 parts by weight of an initiator; 0.01 to 0.03 parts by weight of an inhibitor. As a result, the insulating varnish has all the characteristics and advantages of the imine-modified unsaturated polyester resin described above, which will not be repeated here. In general, the imine-modified unsaturated polyester resin in the insulating varnish contains active double bonds, which can participate in the subsequent curing and cross-linking reaction, which is beneficial to increase the curing and cross-linking density of the insulating varnish, thereby improving the heat resistance of the insulating varnish after curing.

[0021] In some embodiments of the present application, the insulating paint satisfies at least one of the following conditions: the active diluent includes one or more of vinyl toluene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, and triallyl isocyanurate; the initiator includes one or more of tert-butyl perbenzoate and diisopropyl peroxide; the inhibitor includes one or more of p-methoxyphenol, hydroquinone, p-tert-butylcatechol, and 2,5-di-tert-butylhydroquinone.

[0022] In another aspect of the present application, the present application proposes a method for preparing an insulating paint. In some embodiments of the present application, the method for preparing an insulating paint comprises: providing 50 to 60 parts by weight of an imine-modified unsaturated polyester resin, wherein the imine-modified unsaturated polyester resin is the imine-modified unsaturated polyester resin described above, or the imine-modified unsaturated polyester resin is an imine-modified unsaturated polyester resin prepared by the method described above; setting the temperature of the imine-modified unsaturated polyester resin to 70°C to 90°C, adding 37 to 49 parts by weight of an active diluent and 0.01 to 0.03 parts by weight of an inhibitor to the imine-modified unsaturated polyester resin, and mixing them uniformly to obtain a third mixture; cooling the third mixture to below 30°C, adding 1 to 3 parts by weight of an initiator, and mixing them uniformly to obtain an insulating paint. Therefore, by adopting the above method to prepare insulating varnish, an insulating varnish with excellent performance can be obtained. The imide-modified unsaturated polyester resin in the insulating varnish contains active double bonds, which can participate in the reaction during the curing and cross-linking process of the insulating varnish, increase the curing cross-linking density of the insulating varnish, and thus help to improve the heat resistance of the insulating varnish after curing.

[0023] In some embodiments of the present application, the method for preparing an insulating varnish satisfies at least one of the following conditions: the active diluent includes one or more of vinyl toluene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, and triallyl isocyanurate; the initiator includes one or more of tert-butyl perbenzoate and diisopropyl peroxide; the inhibitor includes one or more of p-methoxyphenol, hydroquinone, p-tert-butylcatechol, and 2,5-di-tert-butylhydroquinone.

[0024] In some embodiments of the present application, after adding the reactive diluent and the polymerization inhibitor, stirring is performed for 1 to 2 hours to obtain the third mixture. DETAILED DESCRIPTION

[0025] The embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0026] The capping agents used in the synthesis process of the currently commonly used imide-modified unsaturated polyester resins are mostly saturated monoalcohols (such as N-hydroxyethylphthalimide and N-(2-hydroxyethyl)-tetrahydrophthalimide). The molecular structure of the above-mentioned capping agents does not contain active double bonds and cannot participate in the subsequent curing and cross-linking reaction. The heat resistance of the cured insulating resin prepared by diluting and preparing the above-mentioned capping agents may be limited.

[0027] In order to further improve the heat resistance of the insulating resin after curing, in the present application, a capping agent containing active double bonds is used when preparing the imide-modified unsaturated polyester resin. The active double bonds can participate in the subsequent curing and cross-linking reaction of the insulating resin, thereby increasing the curing and cross-linking density of the insulating resin, and improving the heat resistance of the cured product of the insulating resin.

[0028] In one aspect of the present application, the present application provides an imine-modified unsaturated polyester resin. In some embodiments of the present application, the imine-modified unsaturated polyester resin may include a compound shown in Formula I.

[0029]

[0030] Among them, R1 can be or C2-C4 alkylene, R2 at different positions are independently C2-C6 alkylene or R3 at different positions is independently C1-C4 alkylene, and R4 at different positions is independently

[0031] In some embodiments of the present application, the molecular weight of the imine-modified unsaturated polyester resin may be 600-1200. For example, the molecular weight of the imine-modified unsaturated polyester resin may be 600, 700, 800, 900, 1000, 1100, 1200, or the like.

[0032] Thus, the end-capping part of the imine-modified unsaturated polyester resin contains active carbon-carbon double bonds. When the polyester resin is used in the insulating varnish, the carbon-carbon double bonds can participate in the curing and cross-linking reaction of the insulating varnish, increase the curing and cross-linking density of the insulating varnish, and thus help improve the heat resistance of the insulating varnish cured product. In addition, the imine-modified unsaturated polyester resin has a suitable molecular weight, and thus has a suitable viscosity, which is easy to dilute. When the polyester resin is used to dilute and prepare the insulating varnish, less active diluent can be used for dilution.

[0033] In some embodiments, R4 at different positions may be the same. In some embodiments, R4 at different positions may be different.

[0034] In some embodiments of the present application, R1 can be

[0035] In some embodiments of the present application, R1 can be

[0036] In some embodiments of the present application, R2 at different positions can be independently

[0037] In some embodiments of the present application, R2 at different positions may be the same. In other embodiments of the present application, R2 at different positions may be different.

[0038] In some embodiments of the present application, R2 at different positions can be independently

[0039] In some embodiments of the present application, R3 at different positions can be independently

[0040] In some embodiments, R3 at different positions may be the same. In some embodiments, R3 at different positions may be different.

[0041] In some embodiments of the present application, R3 can be

[0042] In another aspect of the present application, the present application proposes a method for preparing an imine-modified unsaturated polyester resin. In some embodiments of the present application, the method for preparing an imine-modified unsaturated polyester resin may include the following steps:

[0043] S100: placing a polyol, a saturated dibasic acid or anhydride, and an unsaturated dibasic acid or anhydride in a reaction container, and reacting at a first temperature for a first time to obtain a first mixture.

[0044] During the above reaction process, the raw materials will undergo a certain degree of esterification and polycondensation reaction to form unsaturated polyester resin.

[0045] In the present application, there is no particular limitation on the type and size of the reaction container, and those skilled in the art can select one according to actual needs.

[0046] In some embodiments of the present application, the polyol may include one or more of ethylene glycol, propylene glycol, 1,2-propanediol, butanediol, neopentyl glycol, hexanediol, and tris(2-hydroxyethyl)isocyanurate.

[0047] In some embodiments of the present application, the polyol may include one or more of ethylene glycol, 1,2-propylene glycol, neopentyl glycol, and tris(2-hydroxyethyl)isocyanurate.

[0048] In some embodiments of the present application, the saturated dibasic acid or anhydride may include one or more of phthalic acid, phthalic anhydride, isophthalic acid, succinic acid, glutaric acid, adipic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid.

[0049] In some embodiments of the present application, the saturated dibasic acid or anhydride may include one or both of phthalic acid and phthalic anhydride.

[0050] In some embodiments of the present application, the unsaturated dibasic acid or anhydride may include one or more of maleic anhydride (also known as maleic anhydride) and maleic acid (also known as maleic acid).

[0051] The above-mentioned polyols, saturated dibasic acids or acid anhydrides, and unsaturated dibasic acids or acid anhydrides can be subjected to esterification and polycondensation reactions to form unsaturated polyester resins.

[0052] In some embodiments of the present application, 20 to 45 parts by weight of polyol, 10 to 22 parts by weight of saturated dibasic acid or anhydride, and 20 to 29 parts by weight of unsaturated dibasic acid or anhydride may be added to the reaction container. For example, 20, 25, 30, 35, 40 or 45 parts by weight of polyol, 10, 13, 15, 18, 20 or 22 parts by weight of saturated dibasic acid or anhydride, and 20, 22, 25, 27 or 29 parts by weight of unsaturated dibasic acid or anhydride may be added.

[0053] The weight proportions of various raw materials being within the above ranges are conducive to more complete esterification and polycondensation reactions, allowing more raw materials to participate in the reactions to form unsaturated polyesters.

[0054] In some embodiments of the present application, the first temperature may be 170° C. to 200° C., for example, the first temperature may be 170° C., 175° C., 180° C., 185° C., 190° C., 195° C., 200° C., etc. Carrying out the first reaction at the above temperature is conducive to promoting esterification and polycondensation between the raw materials, thereby facilitating the formation of unsaturated polyester resin.

[0055] In some embodiments of the present application, the first time may be 5 to 7 hours, for example, the first time may be 5 hours, 5.5 hours, 6 hours, 6.5 hours or 7 hours. This is conducive to the full progress of the esterification and polycondensation reactions, thereby facilitating the improvement of the yield and the utilization rate of the raw materials.

[0056] In some embodiments of the present application, the above reaction can be carried out under a protective atmosphere (such as nitrogen, argon, etc.), thereby better avoiding the adverse effects of external air on the esterification and polycondensation reactions, which is beneficial to improving the performance of the product. In some embodiments, the above reaction can be carried out under a nitrogen protective atmosphere.

[0057] In some embodiments of the present application, the degree of reaction and whether the next end-capping reaction can be performed can be judged by the acid value of the reaction product. In some embodiments, when the acid value of the product is ≤148 mgKOH / g, an end-capping agent can be added to the reaction system for subsequent reaction.

[0058] In some embodiments, during the above reaction process, the reaction system can be stirred to promote the reaction.

[0059] S200: adding 15 to 30 parts by weight of a capping agent to the first mixture, and reacting at a second temperature for a second time to obtain a second mixture.

[0060] In some embodiments of the present application, the capping agent may include Wherein, R3 can be a C1-C4 alkylene group, and R4 can be In some embodiments, R3 can be

[0061] After adding the capping agent to the first mixture, the capping agent can react with the first mixture under certain temperature conditions, and the hydroxyl group in the capping agent can react with the active group (such as hydroxyl group, carboxyl group, etc.) at the end of the polymer chain, thereby sealing the active end of the polymer chain.

[0062] In some specific embodiments of the present application, the end-capping agent may include one or more of N-hydroxyethyl maleimide, N-hydroxyethyl citraconimide, and N-hydroxyethyl itaconimide. Among them, the structural formula of N-hydroxyethyl maleimide is The structural formula of N-hydroxyethylcitraconimide is The structural formula of N-hydroxyethyl itaconimide is The above-mentioned end-capping agent contains a hydroxyl group and an imide ring, which can end-cap and imide-modify the unsaturated polyester resin to improve the performance of the unsaturated polyester resin; and the above-mentioned end-capping agent contains active carbon-carbon double bonds. After the imide-modified unsaturated polyester resin is applied to the insulating paint, the active double bonds in the end-capping agent can participate in the curing and cross-linking reaction of the insulating paint, increase the curing and cross-linking density of the insulating paint, and improve the heat resistance of the cured product of the insulating paint.

[0063] In some embodiments of the present application, in addition to the aforementioned structural formula The end-capping agent may further include trimethylolpropane diallyl ether, which also contains an active hydroxyl group and can end-cap the unsaturated polyester resin. In addition, trimethylolpropane diallyl ether is used to replace part of the structural formula The compound is beneficial to improve the air drying properties of the insulating varnish.

[0064] In some embodiments of the present application, the second temperature may be 170° C. to 200° C., for example, the second temperature may be 170° C., 175° C., 180° C., 185° C., 190° C., 195° C., 200° C., etc. The above temperature is conducive to the end-capping agent to block the active end of the polymer chain, so that the molecular weight of the polymer no longer continues to increase.

[0065] In some embodiments of the present application, the second time can be 5 to 7 hours, for example, the second time can be 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, etc. During the reaction time, the end-capping agent can react with more unsaturated polyester resin to form an end-capping structure containing an imide ring.

[0066] In some embodiments of the present application, the above reaction can be carried out under a protective atmosphere (such as nitrogen, argon, etc.), thereby better avoiding the adverse effects of external air on the esterification and polycondensation reactions, which is beneficial to improving the performance of the product. In some embodiments, the above reaction can be carried out under a nitrogen protective atmosphere.

[0067] In some embodiments, during the above reaction process, the reaction system may be stirred.

[0068] In some embodiments of the present application, the degree of reaction can be determined by the acid value of the second mixture. In some embodiments, when the acid value of the second mixture is ≤61 mgKOH / g, subsequent treatment can be performed.

[0069] S300: evacuating the reaction system, allowing the second mixture to continue to react at a third temperature for a third time, to obtain an imine-modified unsaturated polyester resin.

[0070] In steps S100 and S200, the raw materials are continuously subjected to esterification and polycondensation reactions, and water molecules are continuously generated. When the content of water molecules in the reaction system is relatively high, the reaction will be affected. Therefore, the reaction system can be vacuumed to remove the water molecules in the reaction system. After steps S100 and S200, there will still be a portion of unreacted raw materials in the reaction system. After vacuuming, the second mixture is allowed to continue to react at the third temperature to promote the forward progress of the reaction (e.g., esterification reaction, polycondensation reaction, and end-capping reaction) so as to obtain an imine-modified unsaturated polyester resin.

[0071] In some embodiments of the present application, the third temperature may be 170° C. to 200° C., for example, the third temperature may be 170° C., 175° C., 180° C., 185° C., 190° C., 195° C., 200° C., etc. The water molecules in the reaction system are removed by vacuum, and at the above temperature, the substances in the system can continue to undergo esterification reaction, polycondensation reaction and end-capping reaction, thereby facilitating the improvement of the yield of the imine-modified unsaturated polyester resin and the utilization rate of the raw materials.

[0072] In some embodiments of the present application, the third time may be 5 to 7 hours, for example, the third time may be 5 hours, 5.5 hours, 6 hours, 6.5 hours or 7 hours. Thus, it is beneficial for the substances in the system to react more fully, thereby further improving the yield and the utilization rate of the raw materials.

[0073] In some embodiments of the present application, the acid value of the imine-modified unsaturated polyester resin may be 20-32 mgKOH / g, for example, the acid value of the imine-modified unsaturated polyester resin may be 20 mgKOH / g, 23 mgKOH / g, 25 mgKOH / g, 27 mgKOH / g, 30 mgKOH / g, 32 mgKOH / g, etc. Thus, the imine-modified unsaturated polyester resin has a suitable acid value, and at this time, the imine-modified unsaturated polyester resin has a suitable molecular weight and viscosity, which is convenient for subsequent dilution, and is conducive to reducing the amount of active diluent used in the subsequent dilution process and shortening the time required for the dilution process.

[0074] In some embodiments, during the above reaction process, the reaction system may be stirred.

[0075] The specific process of preparing imine-modified unsaturated polyester resin is further explained in combination with the reaction formula below:

[0076] 1) Synthesis of unsaturated polyester resin

[0077]

[0078] In the above reaction formula, HOOC-R1-COOH is a saturated dibasic acid. Specifically, HOOC-R1-COOH can be phthalic acid (corresponding R1 is ), isophthalic acid (corresponding to R1 is ), succinic acid (corresponding to R1 is ), glutaric acid (corresponding R1 is ), adipic acid (corresponding to R1 is )、1,3-cyclohexanedicarboxylic acid (corresponding to R1 is ) or 1,4-cyclohexanedicarboxylic acid (corresponding to R1 is ); HO-R2-OH is a polyol, specifically, HO-R2-OH can be ethylene glycol (corresponding R2 is ), 1,2-propylene glycol (corresponding to R2 is ), neopentyl glycol (corresponding to R2 is ), tris(2-hydroxyethyl)isocyanurate (corresponding to R2 is ), propylene glycol (corresponding to R2 is ), butanediol (corresponding R2 is ) or hexanediol (corresponding to R2 is ).

[0079] Saturated dibasic acid or anhydride, polyol, unsaturated dibasic acid or anhydride (eg, maleic anhydride) undergo esterification and polycondensation to form unsaturated polyester resin.

[0080] 2) Capping reaction with capping agent

[0081] ①N-Hydroxyethylmaleimide end-capping reaction

[0082]

[0083] ②N-Hydroxyethylcitraconimide end-capping reaction

[0084]

[0085] ③N-Hydroxyethylitaconimide end-capping reaction

[0086]

[0087] The hydroxyl groups in N-hydroxyethylmaleimide, N-hydroxyethylcitraconimide and N-hydroxyethylitaconimide can react with the active group hydroxyl groups at both ends of the unsaturated polyester resin molecular chain to block the active ends of the unsaturated polyester resin.

[0088] In another aspect of the present application, the present application proposes an insulating varnish. In some embodiments of the present application, the insulating varnish may include 50 to 60 parts by weight of an imine-modified unsaturated polyester resin, 37 to 49 parts by weight of a reactive diluent, 1 to 3 parts by weight of an initiator, and 0.01 to 0.03 parts by weight of a polymerization inhibitor. Among them, the imine-modified unsaturated polyester resin may be the imine-modified unsaturated polyester resin described above, or the imine-modified unsaturated polyester resin may be an imine-modified unsaturated polyester resin prepared by the method described above. Thus, the insulating varnish has all the characteristics and advantages of the imine-modified unsaturated polyester resin described above or the imine-modified unsaturated polyester resin prepared by the method described above, which will not be repeated here.

[0089] In some embodiments of the present application, the insulating paint may include: 50, 52, 55, 57 or 60 parts by weight of imide modified unsaturated polyester resin, 37, 40, 42, 45, 47 or 49 parts by weight of active diluent, 1, 1.5, 2, 2.5 or 3 parts by weight of initiator, 0.01, 0.015, 0.02, 0.025 or 0.03 parts by weight of inhibitor.

[0090] In the insulating varnish, each component has an appropriate content, and the insulating varnish has an appropriate viscosity and gel time (the time it takes for the insulating varnish to cure and crosslink under heating conditions when the insulating varnish is used to perform impregnation insulation treatment on coil windings and iron cores of various types of motor electrical components); the imide-modified unsaturated polyester resin in the insulating varnish contains active carbon-carbon double bonds, which can participate in the curing and crosslinking reaction of the insulating varnish, increase the curing and crosslinking density of the insulating varnish, and thus increase the heat resistance of the insulating varnish cured product.

[0091] The structural formula, molecular weight and other characteristics of the imine-modified unsaturated polyester resin have been described in detail above and will not be repeated here.

[0092] In some embodiments of the present application, the reactive diluent may include one or more of vinyl toluene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, and triallyl isocyanurate. In some embodiments, the reactive diluent may be vinyl toluene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, or triallyl isocyanurate. In other embodiments, the reactive diluent may include two or more of vinyl toluene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, and triallyl isocyanurate. As a result, the insulating paint in the present application has the characteristics of safety, environmental protection, and low volatility. In the present application, the use of low-odor, high-boiling-point reactive diluents to replace all or most of the currently commonly used reactive diluents such as styrene with a large odor, low boiling point, and low flash point can at least alleviate or even solve the problems of the traditional imide-modified unsaturated polyester insulating resin with a large odor, flammability, explosion, and high curing volatile matter to a certain extent.

[0093] In some embodiments of the present application, the initiator may include one or more of tert-butyl perbenzoate and dicumyl peroxide. In some embodiments, the initiator may be tert-butyl perbenzoate or dicumyl peroxide. In other embodiments, the initiator may be a mixture of tert-butyl perbenzoate and dicumyl peroxide. The above initiators may all initiate the cross-linking and curing reaction of each component in the insulating varnish under certain conditions, so that the insulating varnish forms a cured product.

[0094] In some embodiments of the present application, the inhibitor may include one or more of p-methoxyphenol, hydroquinone, p-tert-butylcatechol, and 2,5-di-tert-butylhydroquinone. In some embodiments, the inhibitor may be p-methoxyphenol, hydroquinone, p-tert-butylcatechol, or 2,5-di-tert-butylhydroquinone. In other embodiments, the inhibitor may include at least two of p-methoxyphenol, hydroquinone, p-tert-butylcatechol, and 2,5-di-tert-butylhydroquinone. The above-mentioned inhibitor can at least to some extent prevent unnecessary reactions between the components of the insulating varnish (for example, free radical addition reactions of double bonds), so that the insulating varnish maintains good stability during storage.

[0095] In another aspect of the present application, the present application proposes a method for preparing an insulating varnish. In some embodiments of the present application, the method for preparing an insulating varnish may include the following steps:

[0096] S400: providing 50 to 60 parts by weight of an imine-modified unsaturated polyester resin.

[0097] In some embodiments of the present application, the imine-modified unsaturated polyester resin may be the imine-modified unsaturated polyester resin described above, or the imine-modified unsaturated polyester resin may be the imine-modified unsaturated polyester resin prepared by the method described above. The structure, molecular weight, etc. of the imine-modified unsaturated polyester resin have been described in detail above and will not be repeated here.

[0098] In some embodiments of the present application, 50, 53, 55, 57 or 60 parts by weight of the imine-modified unsaturated polyester resin may be provided.

[0099] S500: The temperature of the imine-modified unsaturated polyester resin is set at 70° C. to 90° C., 37 to 49 parts by weight of a reactive diluent and 0.01 to 0.03 parts by weight of a polymerization inhibitor are added to the imine-modified unsaturated polyester resin, and the mixture is mixed uniformly to obtain a third mixture.

[0100] In some embodiments of the present application, the imine-modified unsaturated polyester resin can be prepared by the aforementioned method. After the second mixture is reacted for a third time to obtain the imine-modified unsaturated polyester resin in step S300, the temperature of the reaction system is relatively high, and cold water can be passed to reduce the temperature of the imine-modified unsaturated polyester resin to 70° C. to 90° C., and then a reactive diluent and a polymerization inhibitor are added to the imine-modified unsaturated polyester resin. The temperature in the reaction system is 70° C. to 90° C., which is conducive to the rapid dilution and dissolution of the imine-modified unsaturated polyester resin, thereby facilitating the shortening of the preparation time.

[0101] In some embodiments of the present application, the reactive diluent may include one or more of vinyl toluene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, and triallyl isocyanurate. The above reactive diluents can be used to dilute and dissolve imine-modified unsaturated polyester resins, and the use of reactive diluents with advantages such as low odor and high boiling point to completely or mostly replace the currently commonly used reactive diluents such as styrene with strong odor, low boiling point, and low flash point can improve the problems of strong odor, flammability and explosion, and high curing volatile matter of the insulating paint, which is conducive to the preparation of safe, environmentally friendly, and low-volatile insulating paint.

[0102] In some embodiments of the present application, the amount of the active diluent added may be 37, 40, 42, 45, 47 or 49 parts by weight. The above amount of active diluent added can fully dilute and dissolve the imine-modified unsaturated polyester resin to obtain a mixture with a suitable viscosity.

[0103] In some embodiments of the present application, the polymerization inhibitor may include one or more of p-methoxyphenol, hydroquinone, p-tert-butylcatechol, and 2,5-di-tert-butylhydroquinone.

[0104] In some embodiments of the present application, the amount of polymerization inhibitor added can be 0.01, 0.015, 0.02, 0.025 or 0.03 parts by weight. The above amount of polymerization inhibitor added can effectively prevent the components of the insulating paint from reacting during storage, so that the insulating paint maintains good stability during storage.

[0105] In some embodiments of the present application, after adding the active diluent and the polymerization inhibitor, stirring may be performed for 1 to 2 hours to obtain a third mixture. The components may be mixed evenly by stirring to form a mixture with good uniformity.

[0106] The stirring rate is not particularly limited in the present application, and those skilled in the art can set and adjust it according to actual conditions.

[0107] S600: Cool the third mixture to below 30° C., add 1 to 3 parts by weight of an initiator, mix well, and obtain an insulating varnish.

[0108] The initiator can easily initiate the reaction between the components in the reaction system at a higher temperature. Therefore, after the active diluent and the inhibitor are evenly mixed, the third mixture needs to be cooled to below 30°C before adding the initiator.

[0109] In some embodiments of the present application, the initiator may include one or more of tert-butyl perbenzoate and dicumyl peroxide.

[0110] In some embodiments of the present application, the amount of the initiator added may be 1, 1.5, 2, 2.5 or 3 parts by weight. The initiator added in the above amount may initiate a curing and cross-linking reaction between the components in the insulating varnish under certain conditions, so that the insulating varnish forms a cured product.

[0111] The insulating paint is prepared by the method, with simple steps and easy operation; the prepared insulating paint has good stability during storage, and when in use, the active double bonds in the end-capping structure of the imide-modified unsaturated polyester resin can participate in the curing and cross-linking of the insulating paint, increase the curing and cross-linking density of the insulating paint, and improve the heat resistance of the insulating paint cured product.

[0112] The present application will be described below by specific examples, and it will be appreciated by those skilled in the art that the following specific examples are only for illustrative purposes, and do not limit the scope of the present application in any way. In addition, in the following examples, unless otherwise specified, the materials and equipment used are all commercially available. If in the following examples, specific processing conditions and processing methods are not clearly described, then conditions and methods known in the art can be used to process.

[0113] Example 1

[0114] Example 1 of the present application provides a method for preparing an imine-modified unsaturated polyester insulating resin (i.e., insulating varnish), the steps of which are:

[0115] 1) First, 14.55 parts of ethylene glycol, 9.91 parts of 1,2-propylene glycol, 21.43 parts of phthalic anhydride, and 28.38 parts of maleic anhydride are added to a reaction container, and the mixture is stirred and heated to 200°C for reaction for 5 to 7 hours under nitrogen protection, until the acid value is ≤148 mgKOH / g; then 25.73 parts of N-hydroxyethylmaleimide are added, and the mixture is stirred and reacted at 200°C for 5 to 7 hours under nitrogen protection, until the acid value is ≤61 mgKOH / g; then the mixture is evacuated and reacted at 200°C for 5 to 7 hours, until the acid value is ≤32 mgKOH / g.

[0116] 2) First, cool the imide-modified unsaturated polyester resin (60 parts) obtained by the above-mentioned high-temperature melt esterification / polycondensation reaction to 80°C through cooling water; then add 5 parts of vinyl toluene, 32.98 parts of 1,4-butanediol dimethacrylate and 0.02 parts of p-methoxyphenol that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate, and stir and mix evenly to obtain the imide-modified unsaturated polyester insulating resin finished product (insulating paint finished product).

[0117] It should be noted that the parts in Example 1 and the following examples and comparative examples are all parts by weight.

[0118] Example 2

[0119] Example 2 of the present application provides a method for preparing an imine-modified unsaturated polyester insulating resin, the steps of which are:

[0120] 1) First, add 26.86 parts of 1,2-propylene glycol, 20.75 parts of phthalic anhydride, and 27.48 parts of maleic anhydride into a reaction container, stir and heat to 185°C under nitrogen protection, react for 5 to 7 hours until the acid value is ≤141 mgKOH / g; then add 24.91 parts of N-hydroxyethylmaleimide, stir and react at 185°C under nitrogen protection for 5 to 7 hours until the acid value is ≤59 mgKOH / g; then evacuate and react at 185°C for 5 to 7 hours until the acid value is ≤31 mgKOH / g.

[0121] 2) First, cool the imide-modified unsaturated polyester pure resin (60 parts) obtained by the above high-temperature melt esterification / polycondensation reaction to 80°C through cooling water; then add 3 parts of vinyl toluene, 34.98 parts of 1,4-butanediol dimethacrylate and 0.02 parts of hydroquinone that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate, and stir and mix evenly to obtain the finished imide-modified unsaturated polyester insulating resin.

[0122] Example 3

[0123] Example 3 of the present application provides a method for preparing an imine-modified unsaturated polyester insulating resin, the steps of which are:

[0124] 1) First, 33.46 parts of neopentyl glycol, 18.88 parts of phthalic anhydride and 25.0 parts of maleic anhydride are added to a reaction vessel, and the mixture is stirred and heated to 185° C. for reaction for 5 to 7 hours under nitrogen protection to an acid value of ≤125 mgKOH / g; then 22.66 parts of N-hydroxyethylmaleimide are added, and the mixture is stirred and reacted at 185° C. for 5 to 7 hours under nitrogen protection to an acid value of ≤54 mgKOH / g; then vacuuming is performed and the mixture is reacted at 185° C. for 5 to 7 hours to an acid value of ≤28 mgKOH / g.

[0125] 2) First, cool the imide-modified unsaturated polyester pure resin (55 parts) obtained by the above high-temperature melt esterification / polycondensation reaction to 80°C with cooling water; then add 5 parts of vinyl toluene, 27.38 parts of 1,4-butanediol dimethacrylate, 10 parts of triallyl isocyanurate and 0.02 parts of hydroquinone that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate and 0.6 parts of diisopropyl peroxide, and stir and mix evenly to obtain the finished imide-modified unsaturated polyester insulating resin.

[0126] Example 4

[0127] Example 4 of the present application provides a method for preparing an imine-modified unsaturated polyester insulating resin, the steps of which are:

[0128] 1) First, add 21.96 parts of 1,2-propylene glycol, 10.19 parts of tris(2-hydroxyethyl)isocyanurate, 19.25 parts of phthalic anhydride, and 25.49 parts of maleic anhydride into a reaction container, stir and heat to 185°C under nitrogen protection, react for 5 to 7 hours until the acid value is ≤128 mgKOH / g; then add 25.4 parts of N-hydroxyethylcitraconimide, stir and react at 185°C for 5 to 7 hours under nitrogen protection, until the acid value is ≤55 mgKOH / g; then evacuate and react at 185°C for 5 to 7 hours until the acid value is ≤29 mgKOH / g.

[0129] 2) First, cool the imine-modified unsaturated polyester pure resin (59 parts) obtained by the above high-temperature melt esterification / polycondensation reaction to 80°C through cooling water; then add 5 parts of vinyl toluene, 33.38 parts of 1,4-butanediol dimethacrylate and 0.02 parts of tert-butyl catechol that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate and 0.6 parts of diisopropyl peroxide, and stir and mix evenly to obtain the finished imine-modified unsaturated polyester insulating resin.

[0130] Example 5

[0131] Example 5 of the present application provides a method for preparing an imine-modified unsaturated polyester insulating resin, the steps of which are:

[0132] 1) First, add 27.36 parts of neopentyl glycol, 10.16 parts of tris(2-hydroxyethyl)isocyanurate, 17.73 parts of phthalic anhydride and 23.47 parts of maleic anhydride into a reaction vessel, stir and heat to 185°C under nitrogen protection, react for 5 to 7 hours until the acid value is ≤115 mgKOH / g; then add 22.66 parts of N-hydroxyethylmaleimide, stir and react at 185°C under nitrogen protection for 5 to 7 hours until the acid value is ≤51 mgKOH / g; then evacuate and react at 185°C for 5 to 7 hours until the acid value is ≤27 mgKOH / g.

[0133] 2) First, cool the imine-modified unsaturated polyester pure resin (53 parts) obtained by the above high-temperature melt esterification / polycondensation reaction to 80°C through cooling water; then add 3 parts of vinyl toluene, 31.38 parts of 1,4-butanediol dimethacrylate, 10 parts of triallyl isocyanurate and 0.02 parts of hydroquinone that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate and 0.6 parts of diisopropyl peroxide, and stir and mix evenly to obtain the finished imine-modified unsaturated polyester insulating resin.

[0134] Example 6

[0135] Example 6 of the present application provides a method for preparing an imine-modified unsaturated polyester insulating resin, the steps of which are:

[0136] 1) First, add 21.96 parts of 1,2-propylene glycol, 10.19 parts of tris(2-hydroxyethyl)isocyanurate, 19.25 parts of phthalic anhydride, and 25.49 parts of maleic anhydride into a reaction container, and stir and heat to 170°C under nitrogen protection for 5 to 7 hours to an acid value of ≤128 mgKOH / g; then add 25.41 parts of N-hydroxyethyl itaconimide, stir and react at 170°C for 5 to 8 hours under nitrogen protection to an acid value of ≤55 mgKOH / g; then evacuate and react at 170°C for 5 to 8 hours to an acid value of ≤29 mgKOH / g.

[0137] 2) First, cool the imine-modified unsaturated polyester pure resin (55 parts) obtained by the above high-temperature melt esterification / polycondensation reaction to 80°C through cooling water; then add 3.3 parts of vinyl toluene, 29.08 parts of 1,4-butanediol dimethacrylate, 10 parts of triallyl isocyanurate and 0.02 parts of 2,5-di-tert-butylhydroquinone that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate and 0.6 parts of diisopropyl peroxide, and stir and mix evenly to obtain the finished imine-modified unsaturated polyester insulating resin.

[0138] Example 7

[0139] Example 7 of the present application provides a method for preparing an imine-modified unsaturated polyester insulating resin, the steps of which are:

[0140] 1) First, add 7.49 parts of 1,2-propylene glycol, 17.95 parts of neopentyl glycol, 10.29 parts of tris(2-hydroxyethyl)isocyanurate, 18.23 parts of phthalic anhydride, and 24.14 parts of maleic anhydride into a reaction container, stir and heat to 185°C under nitrogen protection, react for 5 to 7 hours until the acid value is ≤120 mgKOH / g; then add 24.9 parts of N-hydroxyethylcitraconimide, stir and react at 185°C for 5 to 7 hours under nitrogen protection, until the acid value is ≤52 mgKOH / g; then evacuate and react at 185°C for 5 to 7 hours until the acid value is ≤27 mgKOH / g.

[0141] 2) First, cool the imine-modified unsaturated polyester pure resin (54 parts) obtained by the above high-temperature melt esterification / polycondensation reaction to 80°C with cooling water; then add 3 parts of vinyl toluene, 30.38 parts of 1,4-butanediol dimethacrylate, 10 parts of triallyl isocyanurate and 0.02 parts of hydroquinone that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate and 0.6 parts of diisopropyl peroxide, and stir and mix evenly to obtain the finished imine-modified unsaturated polyester insulating resin.

[0142] Example 8

[0143] Example 8 of the present application provides a method for preparing an imine-modified unsaturated polyester insulating resin, the steps of which are:

[0144] 1) First, add 11.52 parts of 1,2-propylene glycol, 13.03 parts of neopentyl glycol, 10.13 parts of tris(2-hydroxyethyl)isocyanurate, 18.53 parts of phthalic anhydride, and 24.54 parts of maleic anhydride into a reaction container, stir and heat to 185°C under nitrogen protection, react for 5 to 7 hours until the acid value is ≤122 mgKOH / g; then add 22.25 parts of N-hydroxyethylmaleimide, stir and react at 185°C for 5 to 7 hours under nitrogen protection, until the acid value is ≤53 mgKOH / g; then evacuate and react at 185°C for 5 to 7 hours until the acid value is ≤28 mgKOH / g.

[0145] 2) First, cool the imine-modified unsaturated polyester pure resin (54 parts) obtained by the above high-temperature melt esterification / polycondensation reaction to 80°C through cooling water; then add 5 parts of vinyl toluene, 28.38 parts of 1,4-butanediol dimethacrylate, 10 parts of triallyl isocyanurate and 0.02 parts of tert-butyl catechol that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate and 0.6 parts of diisopropyl peroxide, and stir and mix evenly to obtain the finished imine-modified unsaturated polyester insulating resin.

[0146] Comparative Example 1

[0147] Comparative Example 1 provides another method for preparing an imine-modified unsaturated polyester insulating resin, the steps of which are:

[0148] 1) First, 27.36 parts of neopentyl glycol, 10.16 parts of tris(2-hydroxyethyl)isocyanurate, 17.73 parts of phthalic anhydride and 23.47 parts of maleic anhydride were added to a reaction vessel, and the mixture was stirred and heated to 185°C for reaction for 5 to 7 hours under nitrogen protection to obtain an acid value of ≤115 mgKOH / g; then 31.35 parts of N-hydroxyethyltetrahydrophthalimide (the amount of the end-capping agent was the same as that of the end-capping agent in Example 5) were added, and the mixture was stirred and reacted at 185°C for 5 to 7 hours under nitrogen protection to obtain an acid value of ≤51 mgKOH / g; then the mixture was evacuated and reacted at 185°C for 5 to 7 hours to obtain an acid value of ≤27 mgKOH / g.

[0149] 2) First, cool the imide-modified unsaturated polyester pure resin (52 parts) obtained by the above high-temperature melt esterification / polycondensation reaction to 80°C through cooling water; then add 3 parts of vinyl toluene, 32.38 parts of 1,4-butanediol dimethacrylate, 10 parts of triallyl isocyanurate and 0.02 parts of hydroquinone that have been stirred and mixed in advance, and stir rapidly for 1.5 hours while hot; then, cool to below 30°C, add 2 parts of tert-butyl perbenzoate and 0.6 parts of diisopropyl peroxide, and stir and mix evenly to obtain the finished imide-modified unsaturated polyester insulating resin.

[0150] The finished products of the imine-modified unsaturated polyester insulating resin in each embodiment and comparative example were tested, and the test results are recorded in Table 1. The test contents and test methods are as follows:

[0151] 1) Appearance is measured in accordance with the provisions of 5.1.1 of GB / T 1981.2-2009;

[0152] 2) Viscosity is measured by rotational viscometer method according to GB / T 24148.4-2009 at 25±1°C;

[0153] 3) Gel time is measured at 100±2°C in accordance with the provisions of 4.9 of GB / T 15022.2-2017;

[0154] 4) The curing volatile matter is measured after curing at 150±2℃ for 2h in accordance with the provisions of 4.13 of GB / T 15022.2-2017;

[0155] 5) The curing volume shrinkage shall be determined in accordance with the provisions of GB / T 24148.9-2014;

[0156] 6) Thick layer curing is measured after curing for 2 hours at 150±2℃ in accordance with the provisions of 4.15 of GB / T 15022.2-2017;

[0157] 7) The glass transition temperature is measured according to the provisions of Method C (Dynamic Mechanical Analysis (DMA)) in GB / T 22567-2008; The test specimen preparation method is as follows: the insulating resin is poured into a polytetrafluoroethylene mold, placed in an oven at 150±2°C for curing for 2h, and then demolded after cooling to obtain a cured specimen;

[0158] 8) The water absorption rate is measured at room temperature in accordance with the provisions of GB / T 1034-2008;

[0159] 9) The bonding strength is tested by twisted coil method according to the provisions of 3.1 of GB / T 11028-1999. The sample to be tested is obtained by dipping the twisted coil in insulating resin once, then placing it horizontally in a blast oven, and baking and curing at 150°C for 2 hours;

[0160] 10) The electrical strength is measured in accordance with the provisions of GB / T 1408.1-2016. The paint cake (casting piece) specimen with a diameter of 100 mm and a thickness of 1.0 mm ± 0.1 mm is prepared by heating the paint liquid at 150 ° C for 2 h;

[0161] 11) The volume resistivity is determined by the paint cake method in accordance with the provisions of GB / T 1410-2006. The paint cake sample preparation process is the same as above.

[0162] 12) Storage stability is determined in accordance with the provisions of 4.4 of GB / T 15022.2-2017 and is determined after heating in a forced air oven at 50±2℃ for 96h.

[0163] Table 1 Test results of properties of imide-modified unsaturated polyester insulating resin

[0164]

[0165] As shown in Table 1, the imine-modified unsaturated polyester insulating resin (insulating varnish) prepared in Examples 1 to 8 of the present application has moderate viscosity, moderate gel time, low curing volatile matter, good thick layer curing performance, high bonding strength, good electrical insulation performance, and good storage stability, indicating that the imine-modified unsaturated polyester insulating resin provided by the present application has excellent comprehensive performance. Compared with Comparative Example 1, the imine-modified unsaturated polyester insulating resin prepared in Examples 1 to 8 of the present application has better heat resistance, among which the heat resistance (such as glass transition temperature, high temperature bonding strength) of the imine-modified unsaturated polyester insulating resin in Example 5 is better.

[0166] The above-mentioned embodiments 1 to 8 are some specific implementation methods of preparing imine-modified unsaturated polyester insulating resin, but the above-mentioned specific implementation methods do not constitute a limitation on the protection scope of this application. Any other corresponding changes and modifications made according to the technical concept of this application should be included in the protection scope of this application.

[0167] In general, the technical solution proposed in this application has the following beneficial effects:

[0168] 1. The acid value of the imine-modified unsaturated polyester resin synthesized in the present application can be 20 to 32 mgKOH / g, the degree of esterification / polycondensation reaction is high, and the molecular weight is appropriate, so that the imine-modified unsaturated polyester insulating resin prepared by dilution thereof has good mechanical properties (such as bonding strength) after curing; a capping agent containing active double bonds in the molecular structure is selected to synthesize the imine-modified unsaturated polyester resin, so that the number of sites (active double bonds) that can participate in the subsequent cross-linking curing reaction in the molecular chain of the imine-modified unsaturated polyester resin (especially the end of the molecular chain) is increased, so that the imine-modified unsaturated polyester insulating resin prepared by dilution thereof has good heat resistance after curing.

[0169] 2. Furthermore, in the present application, a low-odor, high-boiling-point active diluent is used to completely or mostly replace the currently commonly used styrene with a strong odor, low boiling point, and low flash point, which can at least to a certain extent alleviate or even solve the problems of traditional imide-modified unsaturated polyester insulating resins such as strong odor, flammability and explosion, and high curing volatile matter, and can produce safe, environmentally friendly, and low-volatile imide-modified unsaturated polyester insulating resins.

[0170] 3. The imide-modified unsaturated polyester insulating resin of the present application has the advantages of safety, environmental protection, low curing volatile matter, high heat resistance temperature, and excellent electrical insulation performance. It can be used for the impregnation insulation treatment of coil windings and iron cores of various types of motor electrical components. It is particularly suitable for the field of new energy vehicle drive motors with high power density, compact structure, and high heat resistance requirements.

[0171] In the description of this specification, the description of reference terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment are included in at least one embodiment of the present application. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples, unless they are contradictory. In addition, it should be noted that in this specification, the terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0172] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An imine-modified unsaturated polyester resin, characterized in that: The imine-modified unsaturated polyester resin comprises a compound shown in Formula I, and the molecular weight of the imine-modified unsaturated polyester resin is 600 to 1200. Among them, R1 is or C2-C4 alkylene, R2 at different positions are independently C2-C6 alkylene or R3 at different positions is independently C1-C4 alkylene, and R4 at different positions is independently 2. The imine-modified unsaturated polyester resin according to claim 1, characterized in that: At least one of the following conditions is met: R1 is R2 at different positions is independently R3 at different positions is independently 3. The imine-modified unsaturated polyester resin according to claim 1, characterized in that: At least one of the following conditions is met: R1 is R2 at different positions is independently R3 is 4. A method for preparing an imine-modified unsaturated polyester resin, characterized in that: include: 20 to 45 parts by weight of a polyol, 10 to 22 parts by weight of a saturated dibasic acid or anhydride, and 20 to 29 parts by weight of an unsaturated dibasic acid or anhydride are placed in a reaction container, and reacted at a first temperature for a first time to obtain a first mixture; Add 15 to 30 parts by weight of a capping agent to the first mixture, and react at a second temperature for a second time to obtain a second mixture; The reaction system is evacuated, and the second mixture is allowed to continue to react at a third temperature for a third time to obtain an imine-modified unsaturated polyester resin; Wherein, the capping agent includes R3 is a C1-C4 alkylene group, R4 is 5. The method according to claim 4, characterized in that At least one of the following conditions is met: The polyol includes one or more of ethylene glycol, propylene glycol, 1,2-propylene glycol, butylene glycol, neopentyl glycol, hexylene glycol, and tris(2-hydroxyethyl)isocyanurate; The saturated dibasic acid or anhydride includes one or more of phthalic acid, phthalic anhydride, isophthalic acid, succinic acid, glutaric acid, adipic acid, 1,3-cyclohexanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid; The unsaturated dibasic acid or anhydride includes one or more of maleic anhydride and maleic acid; R3 is 6. The method according to claim 4 or 5, characterized in that: The end-capping agent includes one or more of N-hydroxyethylmaleimide, N-hydroxyethylcitraconimide, and N-hydroxyethylitaconimide.

7. The method according to any one of claims 4 to 6, characterized in that: At least one of the following conditions is met: The first temperature is 170°C to 200°C; The first time is 5 to 7 hours; The second temperature is 170°C to 200°C; The second time is 5 to 7 hours; The third temperature is 170°C to 200°C; The third time is 5 to 7 hours.

8. The method according to any one of claims 4 to 7, characterized in that: The capping agent also includes trimethylolpropane diallyl ether.

9. The method according to any one of claims 4 to 8, characterized in that: The acid value of the imine-modified unsaturated polyester resin is 20 to 32 mgKOH / g.

10. An insulating varnish, characterized in that: include: 50 to 60 parts by weight of an imine-modified unsaturated polyester resin, wherein the imine-modified unsaturated polyester resin is the imine-modified unsaturated polyester resin described in any one of claims 1 to 3, or the imine-modified unsaturated polyester resin is the imine-modified unsaturated polyester resin prepared by the method described in any one of claims 4 to 9; 37-49 parts by weight of a reactive diluent; 1 to 3 parts by weight of an initiator; 0.01 to 0.03 parts by weight of polymerization inhibitor.

11. The insulating varnish according to claim 10, characterized in that: At least one of the following conditions is met: The active diluent includes one or more of vinyl toluene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, and triallyl isocyanurate; The initiator includes one or more of tert-butyl perbenzoate and dicumyl peroxide; The polymerization inhibitor includes one or more of p-methoxyphenol, hydroquinone, p-tert-butylcatechol, and 2,5-di-tert-butylhydroquinone.

12. A method for preparing an insulating varnish, characterized in that: include: Providing 50 to 60 parts by weight of an imine-modified unsaturated polyester resin, wherein the imine-modified unsaturated polyester resin is the imine-modified unsaturated polyester resin described in any one of claims 1 to 3, or the imine-modified unsaturated polyester resin is the imine-modified unsaturated polyester resin prepared by the method described in any one of claims 4 to 9; The temperature of the imine-modified unsaturated polyester resin is set at 70° C. to 90° C., 37 to 49 parts by weight of a reactive diluent and 0.01 to 0.03 parts by weight of a polymerization inhibitor are added to the imine-modified unsaturated polyester resin, and the mixture is uniformly mixed to obtain a third mixture; The third mixture is cooled to below 30° C., 1 to 3 parts by weight of an initiator is added, and the mixture is mixed evenly to obtain an insulating varnish.

13. The method according to claim 12, characterized in that At least one of the following conditions is met: The active diluent includes one or more of vinyl toluene, 1,4-butanediol dimethacrylate, triethylene glycol dimethacrylate, and triallyl isocyanurate; The initiator includes one or more of tert-butyl perbenzoate and dicumyl peroxide; The polymerization inhibitor includes one or more of p-methoxyphenol, hydroquinone, p-tert-butylcatechol, and 2,5-di-tert-butylhydroquinone.

14. The method according to claim 12 or 13, characterized in that After adding the active diluent and the polymerization inhibitor, stirring is performed for 1 to 2 hours to obtain the third mixture.

Images