A preparation method of hyperbranched epoxy resin and potting glue containing the hyperbranched epoxy resin

Abstract

The present invention provides a preparation method of a hyperbranched epoxy resin and a potting adhesive containing the hyperbranched epoxy resin. An AB2 monomer - amino acid ester compound is prepared by using an amino acid compound and an alcohol, and then, using 1,3,5 - benzenetricarbonyl chloride as the central core, it reacts with the AB2 monomer to prepare a first - generation polyamide - ester star - shaped polymer. The polyamide - ester star - shaped polymer then undergoes an amidation reaction with the AB2 monomer. By repeating such chemical reaction steps, star - shaped growth can occur around the central core to obtain an N - generation polyamide - ester star - shaped polymer. The N - generation polyamide - ester star - shaped polymer is subjected to a saponification reaction to obtain a carboxyl - terminated N - generation polyamide - carboxylic acid star - shaped polymer, and finally, it is capped with epichlorohydrin to obtain the hyperbranched epoxy resin. The thermally conductive potting adhesive containing the hyperbranched epoxy resin has excellent thermal conductivity and anti - cracking properties.

Description

Technical Field

[0001] The invention belongs to the technical field of epoxy potting adhesives, and in particular relates to a preparation method of a hyperbranched epoxy resin and a potting adhesive containing the hyperbranched epoxy resin. Background Art

[0002] In recent years, the share of new energy electric vehicles in the international market competition has been rising rapidly. New energy electric vehicles such as pure power electric vehicles, plug-in hybrid electric vehicles, fuel cell electric vehicles, and hydrogen electric vehicles can effectively reduce people's excessive dependence on non-renewable energy. The development and utilization of new energy electric vehicles has gradually become a new technological trend for the rapid development of my country's automobile industry.

[0003] The motor is the direct or indirect driving component of the car and is an indispensable core component for driving the car. Therefore, the stable operation of the motor is the guarantee for the normal driving of new energy vehicles. However, the use environment of the motor is relatively complex. Problems such as high temperature, humidity, and vibration will interfere with its normal operation. In order to ensure the stable operation of the equipment, using potting glue to encapsulate it is a more ideal solution. Common potting glues for motors include silicone potting glue and epoxy potting glue. Since the latter has outstanding performance in terms of volume strength and bonding strength, it can largely overcome the shortcomings of the silicone material itself that lacks mechanical strength, and is more suitable for high-power operation in a rotating and strong vibration environment. For example, patent CN111040698B discloses epoxy resin potting glue, preparation method and novel electric drive motor, including modified epoxy resin and modified acid anhydride curing agent in a mass ratio of 100:48-71; the modified epoxy resin is prepared by comprising the following components in parts by mass: 90-95 parts of epoxy resin, 5-10 parts of epoxy diluent, 1.5 parts of coupling agent, 0.03 parts of defoaming agent, 0.5 parts of dispersant, and 315-355 parts of thermal conductive filler; the modified acid anhydride curing agent is prepared by comprising the following components: 100 parts of acid anhydride, 1-3 parts of curing accelerator, and 290-330 parts of filler. Patent CN100355851C discloses an epoxy resin potting compound, which is a motor stator potting material made of TDE-85# as an epoxy resin matrix, methyltetrahydrophthalic anhydride as a curing agent, 2-methylimidazole and propylene oxide butyl ether adduct, 2-methylimidazole, 2-ethyl-4-methylimidazole as composite accelerators, polyurethane and active nano-oxide as toughening agents, low molecular weight epoxy resin as a diluent, and active silicon micropowder as a filler, and is uniformly mixed in a specified mass ratio. The material has good technical properties, especially mechanical properties.

[0004] The above technology discloses epoxy glue that can be used for motor potting, which can effectively provide functional protection for the motor or its internal parts such as waterproofing, moisture-proofing, vibration-proofing, and heat conduction. However, as H-class and C-class motors become the mainstream motors in the electric vehicle market, their operating temperatures continue to rise, and the defects of ordinary epoxy resins in thermal conductivity and high and low temperature resistance are gradually emerging. It is necessary to further improve the thermal conductivity and high and low temperature resistance of ordinary epoxy resins to expand the scope of application. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing a hyperbranched epoxy resin and a potting adhesive containing the hyperbranched epoxy resin. An AB2 monomer-amino acid ester compound is prepared by using amino acid compounds and alcohols. Then, 1,3,5-benzenetricarboxylic acid chloride is used as a central core to react with the AB2 monomer to prepare a first-generation polyamide-ester star polymer. The polyamide-ester star polymer is then subjected to an amidation reaction with the AB2 monomer. Such chemical reaction steps are repeated to allow star-shaped growth around the central core to obtain an N-generation polyamide-ester star polymer. The N-generation polyamide-ester star polymer is subjected to a saponification reaction to obtain a carboxyl-terminated N-generation polyamide-carboxylic acid star polymer. Finally, epichlorohydrin is used to terminate the polymer to obtain a hyperbranched epoxy resin. The thermal conductive potting adhesive containing the hyperbranched epoxy resin has excellent thermal conductivity and crack resistance.

[0006] In order to achieve the above purpose, the following technical solutions are adopted:

[0007] A method for preparing a hyperbranched epoxy resin comprises the following steps:

[0008] 1) uniformly mixing an amino acid compound containing two carboxyl groups, a monohydric alcohol, p-toluenesulfonic acid, and a first organic solvent, heating the mixture to react, extracting the mixture with a first alkali solution after the reaction is completed, drying the organic layer, and separating the organic layer by distillation and column chromatography to obtain an amino acid ester compound for later use;

[0009] 2) adding the amino acid ester compound obtained in step 1) and the second organic solvent to a reaction kettle, mixing them evenly, cooling them in an ice bath, respectively dropping 1,3,5-benzenetricarboxylic acid chloride solution and the second alkali solution under stirring conditions, reacting at a constant temperature after the addition, adjusting the pH to neutral after the reaction, separating the oil layer, washing, separating the liquids, distilling, and distilling under reduced pressure to obtain a first-generation polyamide-ester star polymer for use;

[0010] 3) determining the ester content of the first generation polyamide-ester star polymer, adding the polyamide-ester star polymer obtained in step 2) into a third organic solvent and mixing evenly, heating and maintaining the temperature, dripping the solution of the product obtained in step 1), and reacting at the constant temperature after dripping, distilling and distilling under reduced pressure after the reaction is completed to obtain a second generation polyamide-ester star polymer; repeating the reaction of the obtained (N-1) generation polyamide-ester star polymer with the amino acid ester compound obtained in step 1) to obtain an N generation polyamide-ester star polymer, where N is an integer ≥3;

[0011] 4) dispersing the N-generation polyamide-ester star polymer obtained in step 3) into a third alkali solution, heating and maintaining the temperature, reacting under stirring conditions, adjusting the pH to neutral after the reaction, separating the oil layer, and drying to obtain the N-generation polyamide-carboxylic acid star polymer for later use;

[0012] 5) Determine the content of carboxyl groups on the N-generation polyamide-carboxylic acid star polymer, add the N-generation polyamide-carboxylic acid star polymer, epichlorohydrin, and quaternary ammonium salt into a reaction kettle and mix them evenly, heat the reaction, then cool down and keep the temperature constant, drop the fourth alkali solution, continue to react at a constant temperature after the drop, filter and distill after the reaction is completed, adjust the pH to neutral, filter, and vacuum dry to obtain a hyperbranched epoxy resin.

[0013] Step 1) the amino acid compound containing two carboxyl groups is selected from one or a combination of aspartic acid, glutamic acid, and 2-amino-2-methylglutaric acid; the monohydric alcohol is selected from at least one of methanol and ethanol; the molar ratio of the amino acid compound containing two carboxyl groups, the monohydric alcohol and p-toluenesulfonic acid is 1:2.08-2.12:2.08-2.12, the first organic solvent is selected from one or a combination of two or more of benzene, toluene and carbon tetrachloride, and the heating is raised to 120-150°C , the reaction time is 3-5h, the extract is a first alkali solution with a concentration of 5-8wt%, the number of extractions is 1-3 times, there is no special limitation on the first alkali solution, and sodium hydroxide and potassium hydroxide solutions are commonly used in the art, the drying is drying with a desiccant, the desiccant includes but is not limited to sodium sulfate and magnesium sulfate, the drying time is 12-36h, the distillation is to remove the organic solvent and / or unreacted alcohol, and the eluent used in the column chromatography is a mixture of petroleum ether and isopropanol in a volume ratio of 8-10:1;

[0014] Step 2) the second organic solvent is selected from one or a combination of two or more of dichloromethane, methyl formate, and ethyl acetate; the second alkali solution is not particularly limited, and the commonly used sodium hydroxide and potassium hydroxide solutions in the art can be used; the concentration of the second alkali solution is 1-3 mol / L, and the dropping time is 0.5-3h; the concentration of the 1,3,5-benzenetricarboxylic acid chloride solution is 0.1-0.3 mol / L, the dropping time is 1-3h, and the solvent used is one of hexane, carbon tetrachloride, and chloroform. or a combination of two or more; the molar ratio of the amino group of the product obtained in step 1), the alkali in the alkali solution and the acyl chloride group of 1,3,5-benzenetricarboxylic acid chloride is 1:0.95-1.1:0.90-0.95, the reaction time is 1-3h, the pH is adjusted to a concentration of 10-20wt% dilute hydrochloric acid, the washing and separation are performed alternately 1-3 times with water, the distillation is to remove the solvent, and the reduced pressure distillation is to remove unreacted amino acid ester compounds.

[0015] The third organic solvent in step 3) is selected from one or a combination of benzene, toluene, dichloromethane, and carbon tetrachloride, the temperature is raised to 40-100°C, the product obtained in step 1) is dripped in 1-3 hours, and the reaction time is 6-12 hours; the solution concentration of the product obtained in step 1) is 10-20wt%, and the solvent is the second organic solvent; when preparing the N-generation polyamide-ester star polymer, the molar ratio of the amino group on the amino acid ester compound obtained in step 1) to the ester group on the (N-1)-generation polyamide-ester star polymer is 1:1.08-1.2, and the determination of the ester content is determined by referring to the standard GB / T 8021-2003 petroleum product saponification value determination method, the distillation is to remove the solvent and the generated small molecule by-products, and the reduced pressure distillation is to remove the unreacted amino acid ester compound;

[0016] Step 4) The mass ratio of the N-generation polyamide-ester star polymer to the third alkali solution is 1:100-120. The third alkali solution is not particularly limited, and the sodium hydroxide and potassium hydroxide solutions commonly used in the art can be used. The concentration of the third alkali solution is 5-7.5 g / L, the temperature is raised to 40-60°C, the reaction time is 1-2h, the pH is adjusted to neutral with hydrochloric acid with a concentration of 10-20wt%, the drying is dried with a desiccant, the desiccant includes but is not limited to anhydrous sodium sulfate and anhydrous magnesium sulfate, and the carboxyl group is determined by alkali titration;

[0017] Step 5) the temperature is raised to 90-110°C, the reaction time is 2-6h, the temperature is lowered to 70-100°C, the concentration of the fourth alkali solution is 10-15mol / L, there is no special restriction on the fourth alkali solution, and the sodium hydroxide and potassium hydroxide solutions commonly used in the art can be used, the fourth alkali solution is added for 1-3h, and the constant temperature reaction time after the fourth alkali solution is added is 1-2h, the filtration is to remove the generated sodium chloride, and the distillation is to remove the unreacted epichlorohydrin; the epichlorohydrin The molar ratio of oxychloropropane to the carboxyl group in the N-generation polyamide-carboxylic acid star polymer is 18.0-21.6:1.2, the molar amount of the quaternary ammonium salt is 1-3% of the molar amount of the carboxyl group in the N-generation polyamide-carboxylic acid star polymer, the amount of the alkali in the alkali solution is 1.1-1.5 mol of the alkali per 1 mol of the carboxyl group in the N-generation polyamide-carboxylic acid star polymer, and the quaternary ammonium salt is selected from one or a combination of two of tetrabutylammonium bromide, tetraethylammonium chloride, tetramethylammonium bromide, and benzyltriethylammonium chloride.

[0018] The amount of the base used in the present invention refers to the hydroxide (OH) in the base.

[0019] A potting adhesive containing a hyperbranched epoxy resin comprises the following raw materials in parts by weight: 60-80 parts of epoxy resin, 5-10 parts of the hyperbranched epoxy resin, 90-100 parts of a curing agent, 0.5-2 parts of a curing accelerator, 800-1000 parts of a thermal conductive filler, 10-30 parts of a toughening filler, 80-100 parts of a reinforcing filler, and 10-15 parts of a diluent. The hyperbranched epoxy resin is prepared by the method.

[0020] The epoxy value of the epoxy resin is 0.3-0.55, and the epoxy resin is selected from one or a combination of two or more of alicyclic epoxy resin, bisphenol A epoxy resin, and bisphenol F epoxy resin.

[0021] The curing agent is an acid anhydride curing agent, which is selected from one or a combination of two or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, dodecenyl anhydride, glutaric anhydride and polyazelaic anhydride.

[0022] The curing accelerator is selected from one or a combination of amine curing accelerators and imidazole curing accelerators.

[0023] The amine curing accelerator is selected from one or a combination of two or more of benzyldimethylamine, triethylamine, and benzyltriethylammonium chloride.

[0024] The imidazole curing accelerator is selected from one or a combination of two or more of 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-phenylimidazole, and 2-heptadecylimidazole.

[0025] The thermal conductive filler includes large-particle filler, medium-particle filler and small-particle filler. The large-particle filler has an average particle size of 20-60 μm, the medium-particle filler has an average particle size of 1-10 μm, and the small-particle filler has an average particle size of 0.1-1 μm.

[0026] The weight ratio of the large particle size filler, the medium particle size filler and the small particle size filler is 1-3:3-5:1-3.

[0027] The thermally conductive filler is selected from one or a combination of two or more of aluminum hydroxide, aluminum oxide, silicon dioxide, boron nitride, aluminum nitride, silicon nitride, boron nitride, magnesium oxide, silicon carbide, zinc oxide, and magnesium oxide.

[0028] The toughening filler is selected from one or a combination of two or more of polyacrylic acid derivatives, nitrile rubber, core-shell structured acrylic polymer-epoxy system, elastomer-modified epoxy resin, and polyester microspheres.

[0029] The average particle size of the reinforcing filler is 20-50 μm. The reinforcing filler is not particularly limited and includes but is not limited to one of silicon dioxide and calcium carbonate or a combination of the two.

[0030] The diluent is selected from one or a combination of two or more of 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polypropylene glycol diglycidyl ether.

[0031] The present invention also provides a method for preparing the above-mentioned potting compound containing hyperbranched epoxy resin, comprising the following steps:

[0032] Add epoxy resin, hyperbranched epoxy resin and toughening filler into the mixer and mix evenly at a high temperature, cool to room temperature, add diluent and mix evenly, add curing agent and curing accelerator and mix evenly, add thermal conductive filler and reinforcing filler and mix evenly, evacuate and continue stirring, and release the pressure to obtain the above-mentioned anti-cracking epoxy thermal conductive potting glue.

[0033] The temperature is raised to 90-150° C.; the vacuum degree of the vacuuming is 0.08-0.1 MPa, and the stirring time under vacuum is 60-90 min.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] An AB2 monomer-amino acid ester compound is prepared by using amino acid compounds and alcohols, and then 1,3,5-benzenetricarboxylic acid chloride is used as a central core and reacted with the AB2 monomer to prepare a first-generation polyamide-ester star polymer. The polyamide-ester star polymer is then subjected to an amidation reaction with the AB2 monomer. Such chemical reaction steps are repeated to achieve star-shaped growth around the central core to obtain an N-generation polyamide-ester star polymer. The N-generation polyamide-ester star polymer is subjected to a saponification reaction to obtain a carboxyl-terminated N-generation polyamide-carboxylic acid star polymer, and finally epichlorohydrin is used to terminate the polymer to obtain a hyperbranched epoxy resin. The thermal conductive potting adhesive containing the hyperbranched epoxy resin has excellent thermal conductivity and crack resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a photo of the motor stator after potting. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, the "parts" described in the embodiments of the present invention are all parts by weight. The reagents used are all commercially available reagents in the art.

[0038] The quantitative determination of ester groups is carried out in accordance with the standard GB / T 8021-2003 for determination of saponification value of petroleum products;

[0039] The quantitative test method for carboxyl groups is the alkaline titration method;

[0040] The epoxy value was determined by the hydrochloric acid-acetone method;

[0041] Alicyclic epoxy resin S-21, epoxy equivalent weight 140, purchased from Nantong Synasia New Materials Co., Ltd.;

[0042] Toughening filler is Arkema acrylic polymer M51;

[0043] Silicon dioxide was purchased from Jiangsu Lianrui New Materials Co., Ltd., brand NQ1177D, d50=28 um.

[0044] Large-size spherical alumina A1, with an average particle size of 30 μm, was purchased from Ya'an Baitu High-tech Materials Co., Ltd., brand BAK-30;

[0045] Medium-sized spherical alumina A2, with an average particle size of 8 μm, was purchased from Ya'an Baitu High-tech Materials Co., Ltd., brand BAM-10M6;

[0046] Small-particle spherical alumina A3, with an average particle size of 0.8 μm, was purchased from Danyang Yunhui Electronics Co., Ltd., with the brand name HL-08H.

[0047] Preparation of hyperbranched epoxy resin

[0048] Preparation Example 1

[0049] 1) 1 mol of aspartic acid, 2.08 mol of methanol, 2.08 mol of p-toluenesulfonic acid and 300 mL of toluene were mixed uniformly, and the temperature was raised to 130° C. for reaction. After the reaction was completed, the mixture was extracted three times with a 5 wt % sodium hydroxide solution, and the organic layer was dried with anhydrous sodium sulfate for 24 h. Methanol was removed by distillation, and aspartic acid methyl ester was separated by column chromatography (the eluent was a mixture of petroleum ether and isopropanol in a volume ratio of 8:1), and the mixture was set aside;

[0050] 2) 1 mol of aspartic acid methyl ester obtained in step 1) and 200 mL of dichloromethane are added to a reaction kettle and mixed evenly, and then cooled in an ice bath. Under stirring conditions, 3 L of 0.3 mol / L 1,3,5-benzenetricarboxylic acid chloride solution (solvent is hexane) and 0.5 L of 2 mol / L sodium hydroxide solution are added dropwise, and the addition time is 3 h. After the addition is completed, the reaction is carried out at a constant temperature for 1 h. After the reaction is completed, the pH is adjusted to neutral with 10 wt % dilute hydrochloric acid, the oil layer is separated, the oil layer is washed with water, and then the separation is alternately performed three times, the solvent is distilled off, and the unreacted aspartic acid methyl ester is removed by distillation under reduced pressure to obtain a first-generation polyamide-ester star polymer for use.

[0051] 3) 191.7 g of the first generation polyamide-ester star polymer obtained in step 2) (the ester group -COO- content was 40.9 wt% by quantitative determination of the ester group, and the theoretical content of the ester group in the first generation polyamide-ester star polymer was 41.3 wt%) was added to 250 mL of benzene and mixed evenly, the temperature was raised to 80° C. and kept constant, and a solution of 0.2 mol / L aspartic acid methyl ester (solvent was dichloromethane) was added dropwise, the amount of aspartic acid methyl ester solution added was such that the molar ratio of the amino group in aspartic acid methyl ester to the ester group in the polyamide-ester star polymer was 1:0.9, and the addition was continued at a constant temperature for 1 h. The reaction was carried out for 10 hours. After the reaction was completed, the solvent and the generated methanol were distilled off, and the unreacted aspartic acid methyl ester was distilled off under reduced pressure to obtain a second-generation polyamide-ester star polymer; the second-generation polyamide-ester star polymer (the ester group -COO- content was 36.8wt% by quantitative determination of the ester group, and the theoretical content of the ester group in the first-generation polyamide-ester star polymer was 37.4wt%) was reacted with aspartic acid methyl ester to obtain a third-generation polyamide-ester star polymer; the amount of aspartic acid methyl ester solution added still satisfied that the molar ratio of amino group to ester group in the polyamide-ester star polymer was 1:0.9;

[0052] 4) The third-generation polyamide-ester star polymer obtained in step 3) is dispersed in a sodium hydroxide solution with a concentration of 6 g / L, and the mass ratio of the two is 1:100. The temperature is raised to 60° C. and kept constant at this temperature. The reaction is carried out under stirring for 1.5 hours. After the reaction, the pH is adjusted to neutral with 15wt% dilute hydrochloric acid, the oil layer is separated, and dried with anhydrous magnesium sulfate to obtain a third-generation polyamide-carboxylic acid star polymer for later use. The carboxyl -COOH content in the third-generation polyamide-carboxylic acid star polymer is measured by alkali titration to be 40.6wt%, which is close to the theoretical value of 41.1wt%.

[0053] 5) Add 133.0g of the third generation polyamide-carboxylic acid star polymer (calculated according to the carboxyl-COOH content of 40.6wt% in step 4), 21.6mol of epichlorohydrin, and 0.036mol of tetrabutylammonium bromide into the reaction kettle and mix well. Heat to 100°C and keep the temperature constant for ring-opening reaction for 5h, then reduce to 90°C and keep the temperature constant. Add 0.12L of 15mol / L sodium hydroxide solution dropwise for 1.5h, and continue to keep the temperature constant for ring-closing reaction for 2h. After the reaction is completed, filter out the sodium chloride, distill off the unreacted epichlorohydrin, adjust the pH to neutral with 10wt% dilute hydrochloric acid, filter out the sodium chloride, and vacuum dry to obtain the hyperbranched epoxy resin. The epoxy value measured by the hydrochloric acid-acetone method is 0.590. (The theoretical value is 0.605)

[0054] Preparation Example 2

[0055] The rest is the same as Preparation Example 1, except that, in step 3), the reaction of the second generation polyamide-ester star polymer and aspartic acid methyl ester is no longer carried out, that is, the final product of step 3) is the second generation polyamide-ester star polymer; on the basis of the second generation polyamide-ester star polymer, step 4) and step 5) are continued to finally obtain a hyperbranched epoxy resin, and the epoxy value measured by the hydrochloric acid-acetone method is 0.611. (The theoretical value is 0.626)

[0056] Preparation Example 3

[0057] The rest is the same as Preparation Example 1, except that the amino acid compound is 2-amino-2-methylglutaric acid, and the epoxy value of the obtained hyperbranched epoxy resin is 0.48.

[0058] Preparation Example of potting compound containing hyperbranched epoxy resin

[0059] Example 1

[0060] Add 80 parts of alicyclic epoxy resin S-21, 10 parts of hyperbranched epoxy resin obtained in Preparation Example 1, and 10 parts of toughening filler into the mixer. M51, heat to 150℃ and mix evenly, cool to room temperature, add 15 parts of 1,4-butanediol diglycidyl ether, 100 parts of methyltetrahydrophthalic anhydride, and 1 part of curing accelerator benzyltriethylammonium chloride and mix evenly, then add 1000 parts of thermal conductive filler compounded by aluminum oxide A1, aluminum oxide A2, and aluminum oxide A3 in a weight ratio of 3:5:2 and 80 parts of reinforcing filler silicon dioxide NQ1177D and mix evenly, evacuate at a vacuum degree of 0.1MPa, continue stirring for 60min, and release the pressure to obtain the anti-cracking epoxy thermal conductive potting glue.

[0061] Example 2

[0062] The rest is the same as Example 1, except that the hyperbranched epoxy resin is prepared in Preparation Example 2.

[0063] Example 3

[0064] The rest is the same as Example 1, except that the hyperbranched epoxy resin is prepared in Preparation Example 3.

[0065] Example 4

[0066] The rest is the same as Example 1, except that the amount of the hyperbranched epoxy resin obtained in Preparation Example 1 is 5 parts.

[0067] Example 5

[0068] The rest is the same as Example 1, except that the amount of thermal conductive filler is 800 parts.

[0069] Example 6

[0070] The rest is the same as Example 1, except that the amount of alicyclic epoxy resin S-21 used is 100 parts.

[0071] Comparative Example 1

[0072] The rest is the same as Example 1, except that the amount of alicyclic epoxy resin S-21 is 90 parts, and no hyperbranched epoxy resin is added.

[0073] The potting glue prepared in the above examples and comparative examples was subjected to the following performance tests:

[0074] Glass transition temperature test: Tested in accordance with standard GB / T 27816-2011.

[0075] Thermal conductivity test: refer to standard GB / T 29313-2012.

[0076] Linear expansion coefficient: German NETZSCH DIL402C linear expansion coefficient instrument is used, and the heating rate is 2℃ / min.

[0077] Thermal shock test: Prepare the bolt and nut insert test according to the standard GB / T15023-1994. The thermal shock test procedure is as follows: put a group of 5 bolt and nut insert samples into a 180℃ forced air oven for 1 hour, then take them out and immediately put them into a mixture of antifreeze and dry ice with a volume of not less than 10L and a constant temperature of (-35) to (-40)℃. After keeping it for 10 minutes, take out the antifreeze on the surface of the sample and observe whether the sample is cracked. This is one test cycle. Repeat the above operation until 2 out of the 5 samples are cracked.

[0078] Table 1

[0079] project Tg℃ Thermal conductivity W / m·K Linear expansion coefficient ppm / K Hot and cold shock cycles Example 1 168 2.34 15.4 650 Example 2 171 2.29 15.1 635 Example 3 167 2.31 16.0 646 Example 4 158 2.03 16.5 586 Example 5 160 2.10 17.5 620 Example 6 170 2.25 15.8 633 Comparative Example 1 151 1.75 21.8 368

[0080] It can be seen from the above test results that hyperbranched epoxy resin has the effect of improving thermal conductivity. It is speculated that the hyperbranched epoxy resin molecules form phonon channels through amide bonds, the thermal resistance of phonon transfer is reduced, and the thermal conductivity increases with the average sound velocity.

[0081] The use of hyperbranched epoxy resin in the potting compound increases the intermolecular interaction of the potting compound, which is beneficial to improving the hot and cold shock cracking resistance of the potting compound.

[0082] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A method for preparing a hyperbranched epoxy resin, characterized in that: The steps include: 1) Evenly mixing an amino acid compound containing two carboxyl groups, a monohydric alcohol, p-toluenesulfonic acid and a first organic solvent, heating the mixture to react, extracting the mixture with a first alkali solution after the reaction, drying the organic layer, and separating the organic layer by distillation and column chromatography to obtain an amino acid ester compound for later use; 2) adding the amino acid ester compound obtained in step 1) and the second organic solvent to a reaction kettle, mixing them evenly, cooling them in an ice bath, respectively dropping 1,3,5-benzenetricarboxylic acid chloride solution and the second alkali solution under stirring conditions, reacting at a constant temperature after the addition, adjusting the pH to neutral after the reaction, separating the oil layer, washing, separating the liquids, distilling, and distilling under reduced pressure to obtain a first-generation polyamide-ester star polymer for use; 3) determining the ester content of the first generation polyamide-ester star polymer, adding the polyamide-ester star polymer obtained in step 2) into a third organic solvent and mixing evenly, heating and maintaining the temperature, dripping the solution of the product obtained in step 1), and reacting at the constant temperature after dripping, distilling and distilling under reduced pressure after the reaction is completed to obtain a second generation polyamide-ester star polymer; repeating the reaction of the obtained (N-1) generation polyamide-ester star polymer with the amino acid ester compound obtained in step 1) to obtain an N generation polyamide-ester star polymer, where N is an integer ≥3; 4) dispersing the N-generation polyamide-ester star-shaped polymer obtained in step 3) into the third alkali solution, heating and maintaining the temperature, reacting under stirring conditions, adjusting the pH to neutral after the reaction, separating the oil layer, and drying to obtain the N-generation polyamide-carboxylic acid star-shaped polymer for later use; 5) Determine the carboxyl content of the N-generation polyamide-carboxylic acid star polymer, add the N-generation polyamide-carboxylic acid star polymer, epichlorohydrin, and quaternary ammonium salt into a reaction kettle and mix them evenly, heat the reaction, then cool down and keep the temperature constant, drop the fourth alkali solution, continue to keep the temperature constant after the drop, filter and distill after the reaction, adjust the pH to neutral, filter, and vacuum dry to obtain a hyperbranched epoxy resin; Step 1) The amino acid compound containing two carboxyl groups is selected from one or a combination of two or more of aspartic acid, glutamic acid, and 2-amino-2-methylglutaric acid; the monohydric alcohol is selected from at least one of methanol and ethanol; the molar ratio of the amino acid compound containing two carboxyl groups, the monohydric alcohol and p-toluenesulfonic acid is 1:2.08-2.12:2.08-2.

12.

2. The method for preparing a hyperbranched epoxy resin according to claim 1, wherein The eluent used in the column chromatography is a mixture of petroleum ether and isopropanol in a volume ratio of 8-10:

1.

3. The method for preparing a hyperbranched epoxy resin according to claim 1, wherein Step 2) the second organic solvent is selected from one or a combination of two or more of dichloromethane, methyl formate, and ethyl acetate; the second alkali solution is selected from one of sodium hydroxide and potassium hydroxide solution; the concentration of the second alkali solution is 1-3 mol / L, and the dropping time is 0.5-3h; the concentration of the 1,3,5-benzenetricarboxylic acid chloride solution is 0.1-0.3 mol / L, the dropping time is 1-3h, and the solvent used is one or a combination of two or more of hexane, carbon tetrachloride, and chloroform; the molar ratio of the amino group of the product obtained in step 1), the alkali in the second alkali solution, and the acyl chloride group of 1,3,5-benzenetricarboxylic acid chloride is 1:0.95-1.1:0.90-0.

95.

4. The method for preparing a hyperbranched epoxy resin according to claim 1, wherein Step 3) The third organic solvent is selected from one or a combination of benzene, toluene, dichloromethane, and carbon tetrachloride, the temperature is raised to 40-100° C., the product obtained in step 1) is dripped in 1-3 hours, and the reaction time is 6-12 hours; the solution concentration of the product obtained in step 1) is 10-20wt%, and the solvent is the second organic solvent.

5. The method for preparing a hyperbranched epoxy resin according to claim 1, wherein In step 3), when preparing the N-generation polyamide-ester star polymer, the molar ratio of the amino groups on the amino acid ester compound obtained in step 1) to the ester groups on the (N-1)-generation polyamide-ester star polymer is 1:1.08-1.

2.

6. The method for preparing a hyperbranched epoxy resin according to claim 1, wherein Step 5) The molar ratio of epichlorohydrin to carboxyl groups in the N-generation polyamide-carboxylic acid star polymer is 18.0-21.6:1.2, the molar amount of the quaternary ammonium salt is 1-3% of the molar amount of carboxyl groups in the N-generation polyamide-carboxylic acid star polymer, the fourth alkali solution is selected from one of sodium hydroxide and potassium hydroxide solution, the amount of alkali in the fourth alkali solution is 1.1-1.5 mol of alkali per 1 mol of carboxyl groups in the N-generation polyamide-carboxylic acid star polymer, and the quaternary ammonium salt is selected from one of tetrabutylammonium bromide, tetraethylammonium chloride, tetramethylammonium bromide, and benzyltriethylammonium chloride, or a combination of two thereof.

7. A potting compound containing a hyperbranched epoxy resin, characterized in that: The invention comprises the following raw materials in parts by weight: 60-80 parts of epoxy resin, 5-10 parts of the hyperbranched epoxy resin according to any one of claims 1 to 6, 90-100 parts of curing agent, 0.5-2 parts of curing accelerator, 800-1000 parts of thermal conductive filler, 10-30 parts of toughening filler, 80-100 parts of reinforcing filler and 10-15 parts of diluent. The hyperbranched epoxy resin is prepared by the preparation method according to any one of claims 1 to 6.

8. The potting compound containing hyperbranched epoxy resin according to claim 7, characterized in that: The thermal conductive filler includes large-particle filler, medium-particle filler and small-particle filler. The large-particle filler has an average particle size of 20-60 μm, the medium-particle filler has an average particle size of 1-10 μm, and the small-particle filler has an average particle size of 0.1-1 μm.

9. The potting compound containing hyperbranched epoxy resin according to claim 8, characterized in that: The thermally conductive filler is selected from one or a combination of two or more of aluminum hydroxide, aluminum oxide, silicon dioxide, boron nitride, aluminum nitride, silicon nitride, boron nitride, magnesium oxide, silicon carbide, zinc oxide, and magnesium oxide.

10. The method for preparing a potting compound containing a hyperbranched epoxy resin according to any one of claims 7 to 9, characterized in that: The steps include: Add epoxy resin, hyperbranched epoxy resin and toughening filler into the mixer, heat up and mix evenly, cool to room temperature, add diluent and mix evenly, add curing agent and curing accelerator and mix evenly, add thermal conductive filler and reinforcing filler and mix evenly, evacuate and continue stirring, release pressure and filter to obtain anti-cracking epoxy thermal conductive potting glue.

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