A hyperbranched polymer, a preparation method thereof and an epoxy potting material

Abstract

The application discloses a hyperbranched polymer, a preparation method thereof and an epoxy potting material. The hyperbranched polymer is prepared by reacting an intermediate with isocyanuric acid triglycidyl ester, and the intermediate is obtained by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, paraformaldehyde and diethanolamine. The hyperbranched polymer contains phosphorus and nitrogen elements, and simultaneously contains epoxy groups and hydroxyl groups in the surface molecular structure. The hyperbranched polymer is used for preparing the epoxy potting material. When the hyperbranched polymer is added into an epoxy resin matrix and is cured together with an acid anhydride curing agent, the epoxy groups and the hydroxyl groups on the surface participate in cross-linking reaction, and chemical bonds are formed with the epoxy resin matrix. The application realizes the improvement of the toughness and the flame retardance of the epoxy potting material without loss of the glass transition temperature and the strength, and due to the absence of silicon elements, the hydrolysis risk in a damp-heat environment is avoided, and the application is suitable for the potting protection of electronic components.

Description

Technical Field

[0001] This invention relates to the field of epoxy potting technology, specifically to a hyperbranched polymer, its preparation method, and epoxy potting materials. Background Technology

[0002] Amid the global wave of industrial transformation towards intelligent and green manufacturing, the continuous development of new energy vehicles places higher demands on their components. As one of the core technologies of electric vehicles, the electric drive system provides driving force and ensures smooth and stable driving. Thin-film capacitors, as crucial components in the electric drive system, directly determine the efficiency, power density, and lifespan of the entire system through their performance and reliability.

[0003] Film capacitors are evolving towards lighter weight, smaller size, longer lifespan, and better operational stability. Therefore, higher requirements are placed on the potting compounds used. In addition to basic insulation and sealing properties, the potting compounds must also have better heat resistance to prevent cracking during prolonged operation at high temperatures, which could affect the capacitor's lifespan or even cause failure. Furthermore, as an electronic component itself, the potting compound must possess good flame-retardant properties.

[0004] In recent years, significant progress has been made in using hyperbranched polymers for toughening and flame retardant modification of epoxy resins. Hyperbranched polymers possess characteristics such as highly branched three-dimensional spherical structures, no entanglement between molecular chains, internal cavities that can absorb impact energy, and surfaces rich in active functional groups. These characteristics enable them to maintain or increase the crosslinking density of epoxy resins while simultaneously toughening them. One study reported the reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) with paraformaldehyde and diethanolamine to generate a phosphorus- and nitrogen-containing diol intermediate. This intermediate was then condensed with trichlorosilane compounds to prepare a phosphorus-, nitrogen-, and silicon-containing hyperbranched polymer, which was then used in single-component epoxy resin systems. This approach provides flame retardancy by introducing phosphorus and nitrogen elements and provides toughening through the flexible chains of siloxanes, thus improving the toughness and flame retardancy of epoxy resins to a certain extent.

[0005] However, the aforementioned existing technologies still have the following shortcomings: First, silicon is introduced into these hyperbranched polymers, and silicon-oxygen bonds (Si-OC) are prone to hydrolysis in humid and hot environments, which may lead to material performance degradation during long-term use and affect the reliability of electronic components; Second, these hyperbranched polymers only contain hydroxyl groups on their surface and do not contain epoxy groups. When used in epoxy resin systems, the lack of epoxy groups that can participate in curing and crosslinking results in limited crosslinking density, making it difficult to maintain a high glass transition temperature while toughening.

[0006] Therefore, there is an urgent need to find ways to improve the toughening and flame retardant properties of epoxy potting compounds without introducing silicon, while maintaining a high glass transition temperature. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a method for preparing a hyperbranched polymer containing both rigid and flexible segments. Phosphorus and nitrogen elements are introduced into the structure of the hyperbranched polymer. This hyperbranched polymer is then added to an epoxy potting material to improve the toughness and flame retardancy of the epoxy potting material without sacrificing its glass transition temperature and strength. This provides a two-component epoxy potting compound that combines toughness and strength.

[0008] The present invention adopts the following technical solution.

[0009] According to a first aspect of the present invention, a hyperbranched polymer is provided. The hyperbranched polymer contains phosphorus and nitrogen elements, and its molecular structure simultaneously contains epoxy and hydroxyl groups; The hyperbranched polymer was prepared by reacting an intermediate with triglycidyl isocyanate (TGIC). The intermediate is obtained by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), paraformaldehyde, and diethanolamine.

[0010] Preferably, the phosphorus element is derived from DOPO, and the nitrogen element is derived from the triazine ring in the molecular structure of diethanolamine and TGIC.

[0011] Preferably, the chemical formula of the hyperbranched polymer is: .

[0012] According to a second aspect of the present invention, a method for preparing a hyperbranched polymer as described in the first aspect of the present invention is provided. The method includes the following steps: DOPO, paraformaldehyde, and diethanolamine were reacted in an organic solvent to obtain an intermediate; The obtained intermediate and organic solvent were added to a container equipped with a stirrer and a reflux condenser for stirring and dissolution. Then, a catalyst was added, and the mixture was heated to 90-100°C under nitrogen protection and refluxed. TGIC was then added and the mixture was mixed and kept at the temperature for 5-6 hours to ensure that the product retains both epoxy and hydroxyl groups. After the reaction was completed, the product was cooled, separated, and dried to obtain the hyperbranched polymer.

[0013] Preferably, the organic solvent is DMF, DMSO, or tetrahydrofuran; and the catalyst is 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, or 1-methylimidazole.

[0014] Preferably, the molar ratio of the intermediate to TGIC is 1:1 to 1.4:1; the epoxy value of the hyperbranched polymer is 0.19 to 0.25 mol / 100g, and the hydroxyl value is 33 to 42 mg KOH / g.

[0015] According to a third aspect of the present invention, a two-component epoxy potting material is provided. The two-component epoxy potting material is obtained by mixing component A and component B in a mass ratio of 1:0.8 to 1:1.2 and then curing the mixture. Component A comprises epoxy resin and the hyperbranched polymer described in the first aspect of the present invention; Component B contains an anhydride curing agent.

[0016] Preferably, the phosphorus and nitrogen elements in the hyperbranched polymer are incorporated into the cured network of the epoxy resin through chemical cross-linking.

[0017] Preferably, in component A, the amount of hyperbranched polymer added is 5 to 50 parts by mass of epoxy resin per 100 parts of epoxy resin.

[0018] Preferably, the epoxy resin is selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin; the anhydride curing agent is selected from one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride.

[0019] Preferably, component A further comprises one or more of inorganic fillers, defoamers, dispersants, diluents, colorants, and antisettling agents; and component B further comprises one or more of curing accelerators, inorganic fillers, antisettling agents, and dispersants.

[0020] Preferably, the glass transition temperature of the two-component epoxy potting material after curing is 145-160℃, the impact strength at -40℃ is ≥27 J / cm², and the flame retardancy rating reaches UL94 V0.

[0021] The beneficial effects of this invention are that, compared with the prior art, 1. A hyperbranched polymer is prepared by reacting an intermediate obtained from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), paraformaldehyde, and diethanolamine, followed by reaction of this intermediate with triglycidyl isocyanate (TGIC). This hyperbranched polymer contains phosphorus and nitrogen elements, and its surface molecular structure contains both epoxy and hydroxyl groups, but no silicon. This hyperbranched polymer possesses both rigid and flexible segments, integrating multiple functions such as flame retardancy, toughening, and reinforcement. When this hyperbranched polymer is added to an epoxy resin matrix and co-cured with an anhydride curing agent, its surface epoxy and hydroxyl groups participate in the curing reaction, forming chemical bonds with the epoxy resin, thus toughening the resin without lowering the glass transition temperature. Furthermore, since this hyperbranched polymer does not contain silicon, it avoids the risk of hydrolysis of silicon-oxygen bonds in humid and hot environments, which helps ensure the long-term reliability of electronic components.

[0022] 2. By adjusting the molar ratio of the intermediate to TGIC, the content of epoxy and hydroxyl groups in the product can be precisely controlled to obtain the best performance balance, so that the hyperbranched polymer molecule contains both epoxy and hydroxyl groups, which can participate in the subsequent curing network and improve the crosslinking density.

[0023] As can be seen, this invention prepares a hyperbranched polymer containing both rigid and flexible segments, as well as a two-component epoxy potting material. By introducing phosphorus and nitrogen elements into the structure of the hyperbranched polymer and controlling the reaction to ensure that both epoxy and hydroxyl groups are retained on the surface of the hyperbranched polymer, the invention effectively improves the toughness and flame retardancy of the epoxy potting material without sacrificing its glass transition temperature or strength. Attached Figure Description

[0024] Figure 1 This is a schematic diagram illustrating the preparation principle of DPDE, the intermediate used in the preparation of hyperbranched polymers in this invention. Figure 2 This is a schematic diagram illustrating the preparation principle of hyperbranched polymers in this invention; Figure 3 The Fourier transform infrared spectra are obtained by testing the hyperbranched polymers DTHB-1 and DTHB-2 prepared in this invention. Figure 4 This is a graph showing the results of 500 cycles of thermal shock under conditions of (-40℃ / 1h~125℃ / 1h) in Example 4 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0026] In a first aspect of the invention, a hyperbranched polymer is provided. This hyperbranched polymer contains both phosphorus and nitrogen elements, and its molecular structure contains both epoxy and hydroxyl groups. The hyperbranched polymer is prepared by reacting an intermediate (denoted as DPDE) with triglycidyl isocyanate (TGIC), wherein the intermediate is obtained by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), paraformaldehyde, and diethanolamine.

[0027] Phosphorus is derived from DOPO, and nitrogen is derived from the triazine ring in the molecular structure of diethanolamine and TGIC.

[0028] Preferably, the chemical formula of the hyperbranched polymer is: .

[0029] This hyperbranched polymer can be used as a functional additive for epoxy potting materials, giving them excellent toughening and flame retardant properties, and achieving a synergistic improvement in mechanical and flame retardant properties without significantly reducing the glass transition temperature.

[0030] In a second aspect of the invention, a method for preparing the hyperbranched polymer described in the first aspect is provided, the method employing a two-step synthesis of the hyperbranched polymer. Specifically, refer to... Figure 2 The method includes the following steps: S1. DOPO, paraformaldehyde and diethanolamine are reacted in an organic solvent to obtain an intermediate.

[0031] refer to Figure 1 This step specifically includes: In a three-necked flask equipped with a condenser, thermometer, and mechanical stirrer, an organic solvent, DOPO, paraformaldehyde, and diethanolamine are added. The organic solvent can be selected from one or more of toluene, xylene, tetrahydrofuran, and N,N-dimethylformamide, preferably toluene. The molar ratio of DOPO, paraformaldehyde (based on formaldehyde), and diethanolamine is typically 1:1.0~1.5:1.0~1.5, preferably 1:1.05~1.2:1.0~1.2. Under an inert gas (such as nitrogen) atmosphere, the reaction mixture is heated to 110~115°C and refluxed for 10~12 hours. After the reaction is complete, the solvent is removed by rotary evaporation. The crude product is repeatedly washed with ethanol and then vacuum dried at 110~130°C for 12 hours to obtain a white solid intermediate, denoted as DPDE.

[0032] The molecular structure of DPDE includes a phosphenanthrene ring of DOPO (providing rigidity and phosphorus flame retardancy), a methylene bridge introduced by paraformaldehyde, and diethanolamine residues (providing hydroxyl groups, nitrogen flame retardancy, and flexible segments). This intermediate contains reactive hydroxyl groups, which can be used for subsequent ring-opening reactions with epoxy groups.

[0033] S2. The obtained intermediate and organic solvent are added to a container equipped with a stirrer and a reflux condenser for stirring and dissolution. Then, a catalyst is added, and the mixture is heated to 90-100°C under nitrogen protection and refluxed. TGIC is then added for mixing and the reaction is maintained at this temperature for 5-6 hours, so that the product retains both epoxy and hydroxyl groups. After the reaction is completed, the product is cooled, separated, and dried to obtain the hyperbranched polymer.

[0034] In this step, the container is preferably a three-necked flask equipped with a condenser, a thermometer, and a magnetic stirrer. TGIC, or triglycidyl isocyanate, has a molecular structure containing three epoxy groups and a triazine ring, with the triazine ring providing nitrogen flame retardancy and a rigid structure. The organic solvent can be selected from N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran, etc., with DMF being preferred. The catalyst can be selected from 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, or 1-methylimidazole, with 2-methylimidazole being preferred.

[0035] During the reaction, the hydroxyl groups in the DPDE molecule undergo a ring-opening addition reaction with the epoxy groups in the TGIC molecule, gradually constructing a polymer with a highly branched structure.

[0036] It is particularly important to note that the key to this invention lies in controlling the feed ratio of DPDE to TGIC and the reaction conditions, so that some of the epoxy groups in TGIC participate in the ring-opening reaction, while the remaining epoxy groups are retained. Simultaneously, the ring-opening reaction generates new hydroxyl groups, resulting in the final product molecule containing both epoxy and hydroxyl groups. This feature is crucial for its subsequent application in epoxy potting materials: the retained epoxy groups can participate in the curing network of the epoxy resin, forming chemical bonds with the matrix and increasing the crosslinking density; the hydroxyl groups can catalyze the curing reaction of acid anhydrides and also react with epoxy groups, further participating in the network structure.

[0037] After the reaction is complete, the mixture is naturally cooled to room temperature, washed multiple times with deionized water or chloroform, filtered, and dried under reduced pressure to obtain the desired hyperbranched polymer product, denoted as DTHB.

[0038] By adjusting the molar ratio of DPDE to TGIC, the content of epoxy and hydroxyl groups in the product can be controlled. Preferably, the molar ratio of DPDE:TGIC is 1:1 to 1.4:1. Within this preferred range, the epoxy value of the obtained hyperbranched polymer can reach 0.19 to 0.25 mol / 100g, and the hydroxyl value can reach 33 to 42 mg KOH / g. When the molar ratio of DPDE:TGIC is too high (i.e., excessive DPDE), almost all the epoxy groups of TGIC are ring-opened, resulting in a low epoxy content in the product, which is not conducive to subsequent curing and crosslinking. When the molar ratio of DPDE:TGIC is too low (i.e., excessive TGIC), the branching degree of the hyperbranched polymer is insufficient, affecting its toughening and heat resistance effect in epoxy potting materials. Therefore, selecting an appropriate feed ratio and controlling the degree of reaction are important conditions for achieving the technical effects of this invention.

[0039] The preparation method of hyperbranched polymers is further illustrated below through specific examples.

[0040] Preparation Example 1 Approximately 160 mL of toluene, 35.64 g (approximately 0.11 mol) of DOPO, 7.43 g (approximately 0.25 mol, calculated as formaldehyde) of paraformaldehyde, and 15.84 g (approximately 0.15 mol) of diethanolamine were weighed and added to a 500 mL three-necked flask equipped with a thermometer, a condenser, and a mechanical stirrer. The reaction was carried out under nitrogen protection at 110 °C with continuous stirring for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, filtered, and repeatedly washed with ethanol to obtain a white solid crude product. The crude product was dried under vacuum at 130 °C for 12 hours to obtain the intermediate DPDE.

[0041] 33.3 g (approximately 0.10 mol) of DPDE and 150 mL of DMF were added to a 250 mL three-necked round-bottom flask equipped with a magnetic stirrer and a reflux condenser. The mixture was stirred until dissolved, and 0.03 g of 2-methylimidazole was added. Under nitrogen protection, the mixture was heated to 90-100 °C and refluxed. 29.72 g (approximately 0.10 mol) of TGIC was slowly added, and the mixture was kept at this temperature for 6 hours. After the reaction was completed, the mixture was allowed to cool naturally to room temperature, extracted with 300 mL of chloroform, washed three times with deionized water, filtered, precipitated in petroleum ether, and dried under reduced pressure to obtain the terminal epoxy hyperbranched polymer DTHB-1.

[0042] Fourier transform infrared spectroscopy, hydrochloric acid-acetone method for epoxy value titration, and acetic anhydride-pyridine method were used to qualitatively and quantitatively verify the structure and residual epoxy and hydroxyl groups of the target hyperbranched polymer DTHB.

[0043] like Figure 3 The infrared spectrum shows that DTHB-1 is at 910 cm⁻¹ -1 The position shows a distinct characteristic absorption peak of the epoxy group, indicating that the active epoxy group is retained in the molecule; 3200-3600 cm⁻¹ -1 The broad and strong hydroxyl absorption peak at 1180-1210 cm⁻¹ is significantly enhanced. -1 The peak at point P=O indicates the introduction of a phosphorus-containing flame-retardant structure into the hyperbranched polymer. The measured epoxy value of the terminal epoxy hyperbranched polymer DHTB-1 is 0.23 mol / 100g, and the hydroxyl value is 35 mg KOH / g, retaining a large number of reactive epoxy groups.

[0044] It should be noted that in the process of preparing the terminal epoxy hyperbranched polymer DTHB-1, the added 2-methylimidazole is used as a catalyst to lower the reaction temperature and prevent the self-polymerization reaction of TGIC epoxy under high temperature conditions. Other alternative catalysts include 2-ethyl-4-methylimidazole, 2-phenylimidazole, and 1-methylimidazole. The amount added can be adjusted according to actual needs.

[0045] Preparation Example 2 DPDE was prepared using the same method as in Preparation Example 1. 56.61 g (approximately 0.17 mol) of DPDE and 150 mL of DMF were added to a 250 mL three-necked round-bottom flask equipped with a magnetic stirrer and a reflux condenser. The mixture was stirred until dissolved, and 0.04 g of 2-methylimidazole was added as a catalyst. Under nitrogen protection, the mixture was heated to 90-100 °C and refluxed. 29.72 g (approximately 0.10 mol) of TGIC was slowly added, and the reaction was maintained at this temperature for 6 hours. The post-treatment was the same as in Preparation Example 1, yielding a pale yellow solid product, DTHB-2. The epoxy value of DTHB-2 was tested to be 0.09 mol / 100 g, and the hydroxyl value was 58 mg KOH / g. Meanwhile, as... Figure 3DTHB-2 at 910 cm -1 No obvious absorption peak was observed at the position. This indicates that the epoxy group content in the product is significantly reduced. This is because DPDE is in excess, and almost all the epoxy groups of TGIC are consumed by the ring-opening reaction, resulting in a significant reduction in surface-active epoxy groups.

[0046] Preparation Example 3 Following the procedure in Preparation Example 1, with a fixed amount of TGIC (0.1 mol), the amount of DPDE was varied to prepare hyperbranched polymers with different DPDE:TGIC molar ratios. The reaction time was 90–100 °C for 6 hours. The epoxy and hydroxyl values ​​of the products were tested.

[0047] Test results show that when the DPDE:TGIC molar ratio is 1:1 to 1.4:1, the product has a high epoxy value (0.19~0.25 mol / 100g) and a moderate hydroxyl value (33~42 mg KOH / g), which can be considered the preferred range. When DPDE is in excessive excess, the epoxy value decreases significantly, while the hydroxyl value is high, indicating that the epoxy groups are excessively opened and the degree of branching may be insufficient.

[0048] It is evident that by adjusting the molar ratio of the intermediate to TGIC, the content of epoxy and hydroxyl groups in the product can be precisely controlled to obtain the optimal performance balance, so that the obtained hyperbranched polymer molecular structure contains both epoxy and hydroxyl groups, enabling them to participate in the subsequent curing network and improve the crosslinking density.

[0049] In a third aspect of the invention, a two-component epoxy potting material is provided. This two-component epoxy potting material is obtained by mixing component A and component B in a mass ratio of 1:0.8 to 1:1.2 and then curing the mixture. Component A comprises epoxy resin and the hyperbranched polymer (DTHB) described in the first aspect of the invention. Component B comprises an anhydride curing agent.

[0050] The epoxy resin can be selected from one or more of bisphenol A type epoxy resins (such as E51, E44), bisphenol F type epoxy resins, and alicyclic epoxy resins. The amount of hyperbranched polymer added is usually 5 to 50 parts per 100 parts of epoxy resin by weight, preferably 10 to 40 parts per 100 parts of epoxy resin, and more preferably 20 to 30 parts per 100 parts of epoxy resin.

[0051] Among them, the anhydride curing agent can be selected from one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride. Anhydride curing agents exhibit a low exothermic peak, good heat resistance, and electrical insulation properties when reacting with epoxy resins, making them suitable for electronic potting materials.

[0052] In addition, commonly used additives in the art may be added to component A as needed, including but not limited to: inorganic fillers, defoamers, dispersants, diluents, colorants, anti-settling agents, etc. Component B includes, but is not limited to: curing accelerators, inorganic fillers, anti-settling agents, dispersants, etc.

[0053] Inorganic fillers: spherical silica (D50 of 1μm, 10μm, 20μm), aluminum hydroxide, barium sulfate; Curing accelerators: phenolic accelerators, imidazole accelerators, amine accelerators; Toughening agents: core-shell toughening agents, rubber toughening agents, thermoplastic toughening agents; Defoamers: BYK-A530, BYK9070, BYK S-732; Dispersants: BYK163, BYK110, BYK w996; Diluents: Butyl glycidyl ether, phenyl glycidyl ether, benzyl glycidyl ether; Anti-settling agents: hydrophobic fumed silica, BYK P104; Colorant: Carbon black.

[0054] The following describes the preparation method of the two-component epoxy potting material of the present invention.

[0055] First, the inorganic filler is dried in an oven at 150°C for 4-6 hours, and then cooled to 25°C for later use.

[0056] Next, components A and B were prepared.

[0057] The preparation of component A includes: adding epoxy resin, reactive diluent, and hyperbranched polymer DTHB into a stirred tank according to the specified ratio, and stirring at 600-1000 rpm for 10-20 minutes, maintaining a vacuum of -0.09 to -0.1 MPa to remove air bubbles. Subsequently, defoamer, dispersant, inorganic filler, colorant, and anti-settling agent are added sequentially, and high-speed stirring is performed at 1500-2000 rpm, maintaining a vacuum below -0.09 MPa, for 30-60 minutes. After homogeneous mixing, the mixture is filtered, discharged, and packaged to obtain component A.

[0058] The preparation of component B includes: adding the anhydride curing agent and curing accelerator to a mixing tank according to the specified ratio, and mixing them evenly at 600-1000 rpm. Then, inorganic fillers, anti-settling agents, dispersants, etc., are added sequentially, controlling the rotation speed at 1200-1500 rpm, maintaining the vacuum degree below -0.09 MPa, and mixing for 40-80 minutes. After uniform mixing, the mixture is filtered, discharged, and packaged to obtain component B.

[0059] After obtaining components A and B, preheat them separately to appropriate temperatures (usually 80~100℃), then mix them thoroughly at a mass ratio of 1:0.8~1:1.2. After vacuum degassing, pour the mixture into molds or electronic components to be encapsulated. A gradient temperature curing process is used: first cure at 80℃ for 1.5 hours, then increase the temperature to 105℃ for 2 hours, and finally increase the temperature to 120℃ for 2.5 hours. The curing program can also be adjusted according to the specific system.

[0060] After curing, the epoxy potting material is naturally cooled to room temperature to obtain the cured product.

[0061] The following examples 1-7 and comparative examples 1-3 further illustrate the preparation method of the two-component epoxy potting material of the present invention and the technical effects achieved.

[0062] Specifically, in Example 2, the preparation method of the two-component epoxy potting material includes: Preparation of Component A: 42 parts of E51 epoxy resin, 10 parts of TTA21P resin, and 5.5 parts of benzyl glycidyl ether were mixed sequentially according to the specified ratio and then added to a stirred tank. The mixture was stirred at 600 rpm for 10 minutes while maintaining a vacuum of -0.09 MPa until homogeneous. Then, 0.5 parts of defoamer and 0.8 parts of dispersant were added sequentially according to the specified ratio and stirred until homogeneous. Next, 35.6 parts of spherical silica (D50 = 10 μm), 62.3 parts of spherical silica (D50 = 20 μm), 12.1 parts of barium sulfate, 10 parts of DTHB-1, and 1.6 parts of carbon black were added. The mixture was stirred at 1500-2000 rpm while maintaining a vacuum of -0.09 MPa for 40 minutes. The mixture was then filtered and discharged to obtain Component A.

[0063] Preparation of Component B: 65 parts of methyltetrahydrophthalic anhydride and 1.5 parts of DMP30 were mixed in sequence and added to a stirred tank. Then, 63.2 parts of spherical silica (D50 of 10 μm), 63.2 parts of spherical silica (D50 of 20 μm), 0.5 parts of hydrophobic fumed silica, and 0.5 parts of BYK P104 were added sequentially. The mixture was stirred at a speed of 1200~1500 rpm, the vacuum degree was maintained at -0.09 MPa, and the mixing time was 1 hour. The mixture was then filtered, discharged, and packaged to obtain Component B.

[0064] Curing process: Preheat components A and B in a 100℃ forced-air drying oven for 1 hour, then mix them in a 1:1 ratio and cure using a gradient temperature increase: 80℃ for 1.5 hours, 105℃ for 2 hours, and 120℃ for 2.5 hours. After curing, allow to cool naturally to room temperature to obtain the cured epoxy potting material.

[0065] Examples 1, 3, 4, 5, and 6 differed in the amount of DTHB-1 added to component A, while other conditions were the same as in Example 2. Example 7 added DTHB-2 to component A, while other conditions were the same as in Example 2. Comparative Example 1 did not add flame retardant or toughening agent, Comparative Example 2 added a core-shell toughening agent, and Comparative Example 3 added DOPO and a core-shell toughening agent, while other conditions were the same as in Example 2. The relationship (by mass) between the fillers in each example and each comparative example is shown in Table 1.

[0066] Table 1

[0067] The prepared two-component epoxy potting compound was subjected to performance tests, including: Viscosity test of component A: A rotational viscometer was used, referring to GB / T 2794-2022 "Determination of viscosity of adhesives", at 40±0.5℃ and 12 rpm, with a No. 4 rotor continuously rotated, and the reading was taken after the reading stabilized.

[0068] Glass transition temperature (Tg) test: Differential scanning calorimetry (DSC) was used with a heating rate of 10℃ / min under nitrogen atmosphere. The inflection point temperature of the two heating curves was taken.

[0069] Impact resistance test: Refer to GB / T 1043.1-2008 "Determination of impact properties of simply supported beams of plastics", use a simply supported beam impact tester to test the unnotched impact strength at -40℃, 25℃ and 125℃ respectively. The sample size is 80mm×10mm×4mm.

[0070] Flame retardancy rating test: The vertical flammability rating is tested in accordance with the UL94 standard.

[0071] The performance test results of the cured products of the two-component epoxy potting materials prepared in each embodiment and comparative example are shown in Table 2 below.

[0072] Table 2

[0073] As shown in Table 2, when the amount of DHTB-1 added is greater than 20 parts, the epoxy potting compound exhibits good heat resistance and mechanical properties. The hyperbranched polymer prepared in this invention has abundant epoxy and hydroxyl groups, which can participate in the curing network when applied to epoxy potting materials, effectively building the epoxy matrix crosslinking density. The hyperbranched polymer contains both rigid and flexible structures, and the introduction of elements such as nitrogen and phosphorus toughens and strengthens the epoxy potting compound in a homogeneous phase, resulting in good reliability. When the content of DHTB-1 is too high, it aggregates in the epoxy resin as a defect, exacerbating shear deformation and leading to a corresponding decrease in impact strength. DHTB-1 retains some epoxy groups and covalently embeds into the three-dimensional crosslinking network of the epoxy resin through the epoxy-anhydride reaction during curing. The rigid isocyanuric acid ring structure restricts molecular chain movement, ensuring Tg; at the same time, the branched structure of the hyperbranched macromolecule can induce stress dispersion and passivate crazing, achieving covalent chemical toughening and improving toughness without sacrificing thermal properties. When DPDE is in excess, the product DHTB-2 is mainly composed of hydroxyl groups and cannot effectively participate in the main crosslinking. It exists only in a physically dispersed form, and toughening depends on phase separation, making it difficult to simultaneously achieve high Tg and toughness.

[0074] Figure 4 This graph shows the results of 500 thermal shock cycles under conditions of (-40℃ / 1h~125℃ / 1h) in Example 4 of the present invention. The graph visually demonstrates that the epoxy potting material of the present invention has excellent thermal shock resistance and can meet the reliability requirements for long-term use under harsh operating conditions.

[0075] In summary, compared with the prior art, the beneficial effects of the present invention are as follows: 1. A hyperbranched polymer is prepared by reacting an intermediate obtained from 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), paraformaldehyde, and diethanolamine, followed by reaction of this intermediate with triglycidyl isocyanate (TGIC). This hyperbranched polymer contains phosphorus and nitrogen elements, and its surface molecular structure contains both epoxy and hydroxyl groups, but no silicon. This hyperbranched polymer possesses both rigid and flexible segments, integrating multiple functions such as flame retardancy, toughening, and reinforcement. When this hyperbranched polymer is added to an epoxy resin matrix and co-cured with an anhydride curing agent, its surface epoxy and hydroxyl groups participate in the curing reaction, forming chemical bonds with the epoxy resin, thus toughening the resin without lowering the glass transition temperature. Furthermore, since this hyperbranched polymer does not contain silicon, it avoids the risk of hydrolysis of silicon-oxygen bonds in humid and hot environments, which helps ensure the long-term reliability of electronic components.

[0076] 2. By adjusting the molar ratio of the intermediate to TGIC, the content of epoxy and hydroxyl groups in the product can be precisely controlled to obtain the best performance balance, so that the hyperbranched polymer molecule contains both epoxy and hydroxyl groups, which can participate in the subsequent curing network and improve the crosslinking density.

[0077] As can be seen, this invention prepares a hyperbranched polymer containing both rigid and flexible segments and a two-component epoxy potting material. By introducing phosphorus and nitrogen elements into the structure of the hyperbranched polymer and controlling the reaction to retain both epoxy and hydroxyl groups on the surface of the hyperbranched polymer, the present invention effectively improves the toughness and flame retardancy of the epoxy potting material without sacrificing its glass transition temperature and strength, thus providing a heat-resistant, flame-retardant, and crack-resistant epoxy potting material.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A hyperbranched polymer, characterized in that, The hyperbranched polymer contains phosphorus and nitrogen elements, and its molecular structure contains both epoxy and hydroxyl groups. The hyperbranched polymer was prepared by reacting an intermediate with triglycidyl isocyanate (TGIC). The intermediate is obtained by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), paraformaldehyde, and diethanolamine.

2. The hyperbranched polymer according to claim 1, characterized in that, The phosphorus element is derived from DOPO, and the nitrogen element is derived from the triazine ring in the molecular structure of diethanolamine and TGIC.

3. The hyperbranched polymer according to claim 1, characterized in that, The chemical formula of the hyperbranched polymer is: 。 4. A method for preparing a hyperbranched polymer as described in any one of claims 1 to 3, characterized in that, Includes the following steps: DOPO, paraformaldehyde, and diethanolamine were reacted in an organic solvent to obtain an intermediate; The obtained intermediate and organic solvent were added to a container equipped with a stirrer and a reflux condenser for stirring and dissolution. Then, a catalyst was added, and the mixture was heated to 90-100°C under nitrogen protection and refluxed. TGIC was then added and the mixture was mixed and kept at the temperature for 5-6 hours to ensure that the product retains both epoxy and hydroxyl groups. After the reaction was completed, the product was cooled, separated, and dried to obtain the hyperbranched polymer.

5. The preparation method according to claim 4, characterized in that, The organic solvent is DMF, DMSO, or tetrahydrofuran; the catalyst is 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, or 1-methylimidazole.

6. The preparation method according to claim 4, characterized in that, The molar ratio of the intermediate to TGIC is 1:1 to 1.4:1; the hyperbranched polymer has an epoxy value of 0.19 to 0.25 mol / 100g and a hydroxyl value of 33 to 42 mg KOH / g.

7. A two-component epoxy potting compound, characterized in that, The two-component epoxy potting material is obtained by mixing component A and component B in a mass ratio of 1:0.8 to 1:1.2 and then curing. Component A comprises epoxy resin and the hyperbranched polymer according to any one of claims 1-3; Component B contains an anhydride curing agent.

8. The two-component epoxy potting material according to claim 7, characterized in that, The phosphorus and nitrogen elements in the hyperbranched polymer are incorporated into the cured network of the epoxy resin through chemical cross-linking.

9. The two-component epoxy potting material according to claim 7, characterized in that, In component A, the amount of hyperbranched polymer added is 5 to 50 parts by mass of epoxy resin per 100 parts of epoxy resin.

10. The two-component epoxy potting material according to claim 7, characterized in that, The epoxy resin is selected from one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and alicyclic epoxy resin; the anhydride curing agent is selected from one or more of methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methylnadic anhydride.

11. The two-component epoxy potting material according to claim 7, characterized in that, Component A further comprises one or more of inorganic fillers, defoamers, dispersants, diluents, colorants, and antisettling agents; Component B further comprises one or more of curing accelerators, inorganic fillers, antisettling agents, and dispersants.

12. The two-component epoxy potting material according to any one of claims 7 to 11, characterized in that, The two-component epoxy potting material has a glass transition temperature of 145–160°C after curing, an impact strength of ≥27 J / cm² at -40°C, and a flame retardant rating of UL94 V0.

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