A phosphorus-containing multi-arm hyperbranched resin, its preparation and use as a multifunctional adhesive which is inherently flame-retardant

Abstract

This invention discloses a phosphorus-containing multi-arm hyperbranched resin, its preparation, and its application as an intrinsically flame-retardant multifunctional adhesive. The phosphorus-containing multi-arm hyperbranched resin is prepared by a method comprising the following steps: Step 1, using an α-diimide palladium catalyst to catalyze the polymerization of ethylene and 2-(2-bromoisobutyryloxy)ethyl acrylate to obtain a bromo-based multi-arm hyperbranched resin; Step 2, polymerizing the bromo-based multi-arm hyperbranched resin with glycidyl methacrylate to obtain an epoxy-based multi-arm hyperbranched resin; Step 3, subjecting the epoxy-based multi-arm hyperbranched resin to a ring-opening reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to obtain a phosphorus-containing multi-arm hyperbranched resin. This invention provides the application of this phosphorus-containing multi-arm hyperbranched resin as an intrinsically flame-retardant multifunctional adhesive, possessing both excellent bonding and flame-retardant properties, and offering advantages such as low cost, controllable performance, simple process, and suitability for large-scale production and application.

Description

Technical Field

[0001] This invention relates to a phosphorus-containing multi-arm hyperbranched resin, its preparation, and its application as an intrinsically flame-retardant multifunctional adhesive. Background Technology

[0002] As humanoid robot technology advances towards higher power density and integration, the encapsulation and protection of its core components, such as joint motors and servo drives, faces severe challenges. Encapsulation materials not only require excellent adhesive strength to maintain structural stability but also must meet stringent flame retardant standards (UL94 V-0) and efficient heat dissipation and insulation requirements. However, traditional epoxy adhesives used for motor potting are generally brittle, have poor impact resistance, and are highly flammable under high temperatures or electric arcs, releasing dense smoke and toxic gases, posing a serious threat to precision circuits and personal safety.

[0003] To overcome these shortcomings, the industry commonly uses additive flame retardants for modification. However, this method faces a dilemma: while high-filler content of flame retardants can improve the flame retardancy rating, it disrupts the continuity of the resin matrix, leading to a sharp increase in viscosity and poor flowability, making it difficult to penetrate into the tiny gaps of the motor stator coils, severely affecting encapsulation tightness and thermal conductivity. Simultaneously, additive flame retardants pose a risk of migration and precipitation, resulting in a decline in long-term flame retardant performance. Although high thermal conductivity potting compounds formulated with inorganic fillers have emerged in recent years, balancing processing performance and mechanical strength under high filler content remains a pain point for the industry.

[0004] In the field of flame retardant technology, intrinsic flame retardancy (achieving flame retardancy through molecular structure design) is considered an ideal approach to resolving the aforementioned contradictions. Among these, hyperbranched polymers, due to their three-dimensional spherical structure, abundant terminal functional groups, low viscosity, and good reactivity, have become a research hotspot for constructing multifunctional polymer materials. Studies have shown that introducing phosphorus into the hyperbranched framework through chemical bonds can significantly improve the char formation ability and flame retardant efficiency of materials. For example, phosphorus-containing hyperbranched polyols have been proven to significantly reduce the heat release rate and smoke production of polymers; hyperbranching auxiliaries containing phosphorus-containing phenanthrene (DOPO) structures have also been shown to significantly improve the toughness of epoxy resins while enhancing their flame retardancy.

[0005] Despite the progress made in flame-retardant modification in the aforementioned studies, most reported phosphorus-containing hyperbranched resins are limited to use as single-function flame retardants or curing agents, and none have been designed into multi-arm structures that combine high adhesion, excellent flowability, and intrinsic flame-retardant properties. In particular, for the comprehensive protection requirements of "low stress buffering," "resistance to thermal shock," and "halogen-free and low-smoke" in robotic encapsulation scenarios, developing a phosphorus-containing multi-arm hyperbranched resin adhesive that integrates flame retardancy, adhesion, and encapsulation functions holds promise for applications in such scenarios. Its hyperbranched structure provides a material basis for meeting these requirements in the future. Summary of the Invention

[0006] This invention provides a phosphorus-containing multi-arm hyperbranched resin, its preparation method, and its application as an intrinsically flame-retardant multifunctional adhesive. As an adhesive, this resin can exhibit excellent flame-retardant properties while maintaining superior bonding performance. In terms of preparation, it has advantages such as readily available and low-cost raw materials, adjustable flame-retardant components leading to controllable performance, and simple process suitable for large-scale production and application.

[0007] The technical solution adopted in this invention will be described in detail below.

[0008] In a first aspect, the present invention provides a phosphorus-containing multi-arm hyperbranched resin, which is prepared by a method comprising the following steps: Step 1: Using an α-diimide palladium catalyst, ethylene and 2-(2-bromoisobutyryloxy)ethyl acrylate (as shown in Formula I) are polymerized in a one-step "chain-walking" copolymerization mechanism to obtain a bromine-based multi-arm hyperbranched resin.

[0009] I

[0010] Step 2: The bromo-based multi-arm hyperbranched resin obtained in Step 1 is subjected to atom transfer radical polymerization with glycidyl methacrylate as shown in Formula II to obtain an epoxy-based multi-arm hyperbranched resin.

[0011] II

[0012] Step 3: The epoxy-based multi-arm hyperbranched resin obtained in Step 2 is subjected to a ring-opening reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as shown in Formula III to obtain a phosphorus-containing multi-arm hyperbranched resin.

[0013] III.

[0014] The α-diimine palladium catalyst of this invention uses either α-diimine palladium catalyst 1 or 2 as follows:

[0015] Both of the above can be synthesized in the laboratory with reference to the following literature: [1] Johnson LK, Killian CM, Brookhart MJ Am. Chem. Soc., 1995, 117, 6414; [2] Johnson LK, Mecking S., Brookhart MJ Am. Chem. Soc., 1996, 118, 267. In a second aspect, the present invention provides a method for preparing the phosphorus-containing multi-arm hyperbranched resin described in the first aspect, the method comprising the following steps: Step 1: Using an α-diimide palladium catalyst, ethylene and 2-(2-bromoisobutyryloxy)ethyl acrylate (as shown in Formula I) are polymerized in a one-step "chain-walking" copolymerization mechanism to obtain a bromine-based multi-arm hyperbranched resin.

[0016] I

[0017] Step 2: The bromo-based multi-arm hyperbranched resin obtained in Step 1 is subjected to atom transfer radical polymerization with glycidyl methacrylate as shown in Formula II to obtain an epoxy-based multi-arm hyperbranched resin.

[0018] II

[0019] Step 3: The epoxy-based multi-arm hyperbranched resin obtained in Step 2 is subjected to a ring-opening reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as shown in Formula III to obtain a phosphorus-containing multi-arm hyperbranched resin.

[0020] III.

[0021] In some embodiments, the first step of the present invention is specifically carried out as follows: after ethylene gas is introduced into an anhydrous and oxygen-free reaction vessel, anhydrous solvent, ethyl acrylate-2-(2-bromoisobutyryloxy)acrylate and α-diimide palladium catalyst are added. The reaction is carried out uniformly and thoroughly for 6-48 hours under the conditions of reaction temperature of 10-35 °C and ethylene pressure of 0.1-5 atm. After the reaction is completed, the obtained product is separated and purified to obtain bromo-based multi-arm hyperbranched resin.

[0022] The 2-(2-bromoisobutyryloxy)ethyl acrylate described in this invention is a commercially available analytical grade or chemically pure product.

[0023] Furthermore, in step 1, the anhydrous solvent is selected from one of the following anhydrous solvents: anhydrous dichloromethane, anhydrous trichloromethane, anhydrous toluene, with anhydrous dichloromethane being preferred.

[0024] Furthermore, in step 1, the initial concentration of the ethyl acrylate monomer 2-(2-bromoisobutyryloxy) ester is 0.1-2.0 mol / L, preferably 0.5-1.5 mol / L; the initial concentration of the α-diimine palladium catalyst is 1-40 mg / mL, preferably 5-20 mg / mL, more preferably 10-15 mg / mL.

[0025] Furthermore, in step 1, the copolymerization reaction temperature is controlled at 15-30 ℃, preferably 20-30 ℃; the ethylene pressure is controlled at 0.5-2 atm, preferably 1 atm; and the polymerization time is controlled at 12-24 h, preferably 20-24 h.

[0026] Furthermore, in step 1, the separation and purification of the bromine-based multi-arm hyperbranched resin is carried out according to the following steps: (a) After the reaction is complete, remove all solvent by blowing with cold air; (b) Dissolve the initially obtained product in tetrahydrofuran (THF), add an appropriate amount of hydrogen peroxide and concentrated hydrochloric acid aqueous solution and stir thoroughly to remove the residual catalyst in the product; (c) Methanol is added to the product solution to precipitate the product and remove the solvent; (d) The product is dissolved again in tetrahydrofuran and precipitated with methanol. This process is repeated 2 to 3 times until the supernatant is colorless and transparent. (e) The final product solution can be vacuum dried at 30~60 °C for 24-48 h to obtain bromine-based multi-arm hyperbranched resin.

[0027] In some embodiments, step 2 of the present invention is specifically implemented as follows: Brominated multi-arm hyperbranched resin (initiator), glycidyl methacrylate (monomer), cuprous bromide (CuBr, catalyst), N,N,N',N,'N”-pentamethyldiethylenetriamine (PMDETA, ligand), and anhydrous solvent are added to a reaction vessel under nitrogen protection. The reaction is carried out uniformly and thoroughly with stirring for 2-4 hours at a reaction temperature of 15-45°C. After the reaction is completed, the obtained product is separated and purified to obtain epoxy multi-arm hyperbranched resin.

[0028] The glycidyl methacrylate monomer, CuBr, and PMDETA described in this invention are all commercially available analytical grade or chemically pure products.

[0029] Furthermore, in step 2, the anhydrous organic solvent is one of the following anhydrous organic solvents: cyclohexanone, tetrahydrofuran, toluene, preferably cyclohexanone.

[0030] Furthermore, in step 2, the molar ratio of Br, glycidyl methacrylate, CuBr, and PMDETA contained in the brominated multi-arm hyperbranched resin is 1:1–200: 0.5–2:1–5, preferably 1:80–120:0.8–1.2:1.5–2.5, and more preferably 1:100:1:2.

[0031] Furthermore, in step 2, the initial concentration of the bromine-based multi-arm hyperbranched resin is 5–30 mol / L, based on the initial concentration of Br contained therein.

[0032] Furthermore, in step 2, the reaction temperature is controlled at 25-35℃, preferably 30℃; the reaction time is controlled at 2-3 h, preferably 2 h.

[0033] Furthermore, in step 2, the separation and purification of the epoxy-based multi-arm hyperbranched resin is carried out according to the following steps: (a) After the reaction is complete, the precipitate is dripped off from the reaction solution with methanol and the solvent is removed; (b) Dissolve the initially obtained product in tetrahydrofuran, precipitate it again with methanol to remove unreacted monomers, repeat the process 2-3 times after removing the solvent, until the supernatant is colorless and transparent; (c) The final solid product can be vacuum dried at 20-40 °C for 20-30 h to obtain epoxy-based multi-arm hyperbranched resin.

[0034] In some embodiments, step 3 of the present invention is specifically implemented as follows: epoxy-based multi-arm hyperbranched resin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triphenylphosphine catalyst, and anhydrous organic solvent are added to a reaction vessel under nitrogen protection. The reaction is carried out uniformly and thoroughly at a reaction temperature of 100-150°C for 2-4 hours. After the reaction is completed, the obtained product is separated and purified to obtain phosphorus-containing multi-arm hyperbranched resin.

[0035] The 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triphenylphosphine described in this invention are both commercially available analytical grade or chemically pure products.

[0036] Furthermore, in step 3, the anhydrous organic solvent is one of the following anhydrous organic solvents: dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, preferably dimethyl sulfoxide.

[0037] Furthermore, in step 3, the molar ratio of the epoxy group, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and triphenylphosphine catalyst contained in the epoxy-based multi-arm hyperbranched resin is 1:0.5–2.0: 0.1–1, preferably 1:1.5:0.5.

[0038] Furthermore, in step 3, the initial concentration of the epoxy-based multi-arm hyperbranched resin is 0.1-5 mol / L, based on the initial concentration of the epoxy groups it contains.

[0039] Furthermore, in step 3, the reaction temperature is controlled at 110-130℃, preferably 120℃, and the reaction time is controlled at 2-4 h, preferably 3 h.

[0040] Furthermore, in step 3, the separation and purification of the phosphorus-containing multi-arm hyperbranched resin is carried out according to the following steps: (a) After the reaction is complete, the precipitate is removed dropwise from the reaction solution with ethanol, and the solvent is removed; (b) Dissolve the initially obtained product with N,N-dimethylformamide, precipitate again with ethanol to remove unreacted monomers, repeat 2-3 times after removing the solvent, until the supernatant is colorless and transparent; (c) The final solid product can be vacuum dried at 60 °C for 24 h to obtain a phosphorus-containing multi-arm hyperbranched resin.

[0041] Thirdly, the present invention provides the application of the phosphorus-containing multi-arm hyperbranched resin described in the first aspect as an intrinsically flame-retardant multifunctional adhesive.

[0042] The substrate to be bonded by the adhesive can be selected from steel sheets, aluminum sheets, glass, wood, polymethyl methacrylate, polycarbonate, etc., with steel sheets, aluminum sheets or glass being preferred.

[0043] The bonding temperature of the phosphorus-containing multi-arm hyperbranched resin is controlled at 120-180 °C, preferably 120-150 °C, and more preferably 120 °C; the bonding time is 12-36 hours, preferably 20-30 hours, and more preferably 24 hours.

[0044] The present invention has the following advantages over the prior art: First, the phosphorus-containing multi-arm hyperbranched resin of the present invention can leverage the topological characteristics of the hyperbranched polyethylene core. The active sites at the ends of the branches can be easily designed through molecular structure to endow hyperbranched polyethylene with multiple functions such as adhesion and flame retardancy. Compared with linear polymer systems with adhesion and flame retardancy properties, this system has advantages in preparation, such as readily available and low-cost raw materials, adjustable flame retardant components leading to controllable performance, and simple process suitable for large-scale production and application.

[0045] Secondly, the phosphorus-containing multi-arm hyperbranched resin of the present invention contains a large number of active hydroxyl groups after the ring-opening reaction of epoxy groups. These hydroxyl groups are distributed at the ends of the multi-arms of the hyperbranched molecules, which can form strong hydrogen bonds and even chemical bonds with the surfaces of various substrates (such as metals and polymer materials), significantly improving the interfacial bonding force, thereby giving the material excellent adhesion properties.

[0046] Third, this invention introduces phosphorus into a hyperbranched framework through molecular structure design via chemical bonds, thus preparing an intrinsically flame-retardant phosphorus-containing multi-arm hyperbranched resin. When used as an adhesive, this resin achieves the UL94 V-0 flame-retardant standard without the addition of traditional flame-retardant fillers, effectively avoiding the viscosity surge and decreased flowability problems caused by high-filler inorganic flame retardants. Simultaneously, it completely eliminates the risk of migration and precipitation of additive flame retardants, ensuring stable and reliable long-term flame-retardant performance. Attached Figure Description

[0047] Figure 1Preparation process of phosphorus-containing multi-arm hyperbranched multifunctional resin; Figure 2 A is the sample obtained in steps 1 and 2 of Example 1. 1 H NMR spectrum; B is the phosphorus-containing multi-arm hyperbranched resin obtained in step 3 of Example 1. 1 H NMR spectrum; C is the lap shear strength of the samples obtained in Example 1 and Comparative Example 1 on the steel sheet; Figure 3 A is the sample obtained in Examples 2 and 3. 1 H NMR spectrum; B is the sample obtained from Comparative Example 2. 1 H NMR spectrum; C is the GPC curve of the phosphorus-containing multi-arm hyperbranched resin obtained in Examples 2 and 3; D is the GPC curve of the sample of Comparative Example 2; E is the lap shear strength of the samples obtained in Examples 2, 3 and Comparative Example 2. Figure 4 The lap shear strength of the samples obtained in Examples 4 and 5-8; Figure 5 A is the vertical combustion performance test of the sample obtained in Example 9; B is the vertical combustion performance test of the sample obtained in Comparative Example 3. Figure 6 A is the vertical combustion performance test of the sample obtained in Example 10; B is the vertical combustion performance test of the sample obtained in Example 11; C is the vertical combustion performance test of the sample obtained in Comparative Example 4. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the implementation of the present invention is not limited thereto.

[0049] Unless otherwise specified in the embodiments of this invention, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained through conventional technical means or commercially available.

[0050] Example 1, Comparative Example 1

[0051] 1. Sample preparation

[0052] (1) Example 1

[0053] Step 1: Ethylene gas was introduced into a 250 mL Schlenk flask, maintaining a pressure of 1 atm. Then, 0.02 mol of 2-(2-bromoisobutyryloxy)ethyl acrylate monomer and 20 mL of dichloromethane solution containing 250 mg of α-diimine palladium catalyst 1 were added. The reaction was carried out at 25 °C, 600 rpm, and under light-shielding conditions for 24 h. After the reaction, all solvent was removed by purging with cold air. The initially obtained product was dissolved in tetrahydrofuran (THF). Appropriate amounts of hydrogen peroxide and concentrated hydrochloric acid aqueous solution were added and stirred for 2 hours to remove residual catalyst. The product solution was precipitated with methanol to remove the solvent, and the product was redissolved in tetrahydrofuran. Precipitation with methanol was repeated 2-3 times until the supernatant was colorless and transparent. The final product solution was vacuum dried at 60 °C for 48 h to obtain the bromo-based multi-arm hyperbranched resin.

[0054] Step 2: In a 250 mL Schlenk flask under nitrogen protection, 1.0 g of brominated multi-arm hyperbranched resin initiator, 9.95 g of glycidyl methacrylate monomer, 100.4 mg of CuBr catalyst, 242.6 mg of PMDETA ligand, and 20 mL of anhydrous cyclohexanone were added. After purging with nitrogen for 30 min, the mixture was reacted at 30 °C and a stirring rate of 600 rpm for 2 h. After the reaction was complete, the precipitate was removed dropwise from the reaction solution with methanol, and the solvent was removed. The initially obtained product was dissolved in tetrahydrofuran, and the product was precipitated again with methanol to remove unreacted monomers. This process was repeated 2-3 times until the supernatant was colorless and transparent. The final solid product was dried under vacuum at 30 °C for 24 h to obtain the epoxy multi-arm hyperbranched resin.

[0055] Step 3: In a 250 mL three-necked flask under nitrogen protection, add 8.0 g of epoxy-based multi-arm hyperbranched resin, 12.97 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 5.25 g of triphenylphosphine catalyst, and 20 mL of dimethyl sulfoxide solvent. Stir the mixture thoroughly and uniformly for 3 hours at 120 °C. After the reaction, precipitate is removed dropwise from the reaction solution with ethanol, and the solvent is removed. The initially obtained product is dissolved in N,N-dimethylformamide (DMF solvent), and precipitated again with ethanol to remove unreacted monomers. This process is repeated 2-3 times until the supernatant is colorless and transparent. The final solid product is dried under vacuum at 60 °C for 24 h to obtain the phosphorus-containing multi-arm hyperbranched resin.

[0056] Step 4: Prepare a 500 mg / mL solution of the sample obtained in Step 3 in DMF solvent, apply it evenly to the steel sheet substrate, and after the steel sheets are bonded together, heat them in an oven at 120 °C for 24 h to obtain the sample bonded by the phosphorus-containing multi-arm hyperbranched resin.

[0057] (2) Comparative Example 1

[0058] Step 1: In a 250 mL Schlenk flask under nitrogen protection, add 0.89 g of ethyl 2-bromoisobutyrate initiator, 36.13 g of glycidyl methacrylate monomer, 180 mg of CuBr catalyst, 390 mg of dipyridine, and 20 mL of anhydrous cyclohexanone. After purging with nitrogen for 30 min, react at 30 °C and a stirring rate of 600 rpm for 2 h. After the reaction is complete, precipitate is dripped from the reaction solution with methanol, and the solvent is removed. The preliminarily obtained product is dissolved in tetrahydrofuran, and precipitated again with methanol to remove unreacted monomers. This process is repeated 2-3 times until the supernatant is colorless and transparent. The final solid product is dried under vacuum at 30 °C for 24 h to obtain linear epoxy resin.

[0059] Step 2: In a 250 mL three-necked flask under nitrogen protection, add 10.0 g of linear epoxy resin, 15.0 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 2.0 g of triphenylphosphine catalyst, and 35 mL of dimethyl sulfoxide solvent. Stir the mixture thoroughly and uniformly at 120 °C for 3 hours. After the reaction, precipitate is removed dropwise from the reaction solution with ethanol, and the solvent is removed. The initially obtained product is dissolved in N,N-dimethylformamide, and precipitated again with ethanol to remove unreacted monomers. This process is repeated 2-3 times until the supernatant is colorless and transparent. The final solid product is dried under vacuum at 60 °C for 24 h to obtain the linear phosphorus-containing resin.

[0060] Step 3: Referring to Step 4 of Example 1, replace the phosphorus-containing multi-arm hyperbranched resin with a linear phosphorus-containing resin to obtain a sample bonded by the linear phosphorus-containing resin.

[0061] 2. Characterization and Testing

[0062] (1) 1 H nuclear magnetic resonance spectroscopy analysis

[0063] The tests were conducted using a 500 MHz ANANCE III nuclear magnetic resonance spectrometer (Bruker, Switzerland). The test solvent for the samples obtained in steps 1 and 2 of Example 1 was deuterated chloroform, and the test solvent for the samples obtained in step 3 of Example 2 was deuterated dimethyl sulfoxide. The test temperature was room temperature.

[0064] (2) Overlap shear strength test

[0065] The substrate dimensions and bonding area of ​​the standard lap shear test specimens can be referenced in GB / T 7124-2008. The lap shear performance of the adhesive is tested in an electronic universal testing machine at a tensile rate of 5 mm / min and at room temperature. The average value is taken after testing 5 specimens in each group.

[0066] 3. Comparison and Analysis of Test Results

[0067] Figure 2 In the 1H NMR spectra of the samples obtained in Step 1 and Step 2 of Example 1 shown in Figure A, the chemical shift peaks and the chemical structures of the bromine-based multi-arm hyperbranched resin and the epoxy-based multi-arm hyperbranched resin are all consistent. Figure 2 B is the 1H NMR spectrum of the phosphorus-containing multi-arm hyperbranched resin prepared in step 3 of Example 1. The presence of a hyperbranched polyethylene backbone can be confirmed by the characteristic peaks of methyl, methylene, and methine groups. Meanwhile, in the figure... j The peak corresponds to the phosphorus-containing group in the phosphorus-containing multi-arm hyperbranched resin. Figure 2 Based on the characteristic peak areas in the NMR spectra of A and B, the branch density of the hyperbranched polyethylene skeleton of the phosphorus-containing multi-arm hyperbranched resin can be calculated to be 87 branches / 1000C, and the grafting ratio of phosphorus-containing groups is 46.9 mol%, indicating that the phosphorus-containing multi-arm hyperbranched resin can be successfully synthesized according to steps 1 to 3 of Example 1. Furthermore, from... Figure 2 As shown in C, the phosphorus-containing multi-arm hyperbranched resin prepared in Example 1 exhibits an lap shear strength of 4.26 MPa after bonding to the steel sheet surface; compared to Comparative Example 1, the linear phosphorus-containing resin only exhibits a strength of 1.27 MPa after bonding. This is because the phosphorus-containing multi-arm hyperbranched resin in Example 1 has a higher phosphorus-containing group grafting rate compared to the linear phosphorus-containing resin in Comparative Example 1. Successful grafting of phosphorus-containing groups simultaneously causes the epoxy groups to open, generating hydroxyl groups. Therefore, the phosphorus-containing multi-arm hyperbranched resin in Example 1 has a higher hydroxyl molar ratio. The presence of hydroxyl groups can improve the interaction energy between the resin and the steel sheet substrate, thereby enhancing the bonding performance. Therefore, the above performance characterization demonstrates that a phosphorus-containing multi-arm hyperbranched resin with high bonding performance can be prepared from Example 1.

[0068] Example 2, Example 3, Comparative Example 2

[0069] 1. Sample preparation

[0070] (1) Example 2

[0071] Step 1: Synthesize phosphorus-containing multi-arm hyperbranched resin according to Example 1, except that the molar ratio of epoxy-based multi-arm hyperbranched resin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and triphenylphosphine catalyst in Step 3 of Example 1 is changed from 1:1.5:0.5 to 1:2:0.5.

[0072] Step 2: Referring to Step 4 of Example 1, prepare a sample bonded with the phosphorus-containing multi-arm hyperbranched resin obtained in Step 1 of Example 2.

[0073] (2) Example 3

[0074] Step 1: Synthesize phosphorus-containing multi-arm hyperbranched resin according to Example 1, except that the molar ratio of epoxy multi-arm hyperbranched resin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and triphenylphosphine catalyst in Step 3 of Example 1 is changed from 1:1.5:0.5 to 1:0.5:0.5.

[0075] Step 2: Referring to Step 4 of Example 1, prepare a sample bonded with the phosphorus-containing multi-arm hyperbranched resin obtained in Step 1 of Example 3.

[0076] (3) Comparative Example 2

[0077] Step 1: Referring to Step 1 and Step 2 of Example 1, synthesize epoxy-based multi-arm hyperbranched resin.

[0078] Step 2: Referring to Step 4 of Example 1, prepare a sample bonded with the epoxy-based multi-arm hyperbranched resin obtained in Step 1 of Comparative Example 2.

[0079] 2. Characterization and Testing

[0080] (1) 1 H nuclear magnetic resonance spectroscopy analysis: performed according to Example 1.

[0081] (2) Gel permeation chromatography (GPC) analysis

[0082] The samples obtained in Examples 2 and 3 were analyzed using an Agilent GPC 50 gel permeation chromatography analyzer (Agilent, USA). The analytes were dissolved in DMF to prepare solutions of 2-5 mg / mL, filtered through a 0.2 μm syringe filter, and then tested. The test temperature was 25 °C, the mobile phase was DMF solvent, and the standard was styrene (PS).

[0083] The sample obtained in Comparative Example 2 was determined using a 1525 / 2414 gel permeation chromatography analyzer (Water, USA). The analyte was dissolved in tetrahydrofuran (THF) to prepare a solution of 2–5 mg / mL, filtered through a 0.2 μm syringe filter, and then tested. The test temperature was 25 °C, the mobile phase was THF solvent, and the standard was styrene (PS).

[0084] (3) Overlap shear strength test: Refer to Example 1.

[0085] 3. Comparison and Analysis of Test Results

[0086] Figure 3 A and B are the 1H NMR spectra of Examples 2, 3, and Comparative Example 2, respectively. The epoxy-based multi-arm hyperbranched resin obtained in Comparative Example 2 is consistent with step 2 of Example 1. Based on this, referring to step 3 of Example 1, by changing the molar amount of the flame-retardant monomer DOPO, phosphorus-containing multi-arm hyperbranched resins with different phosphorus group grafting rates can be obtained. Figure 3 From the two 1H NMR spectra (A and B), calculations using characteristic peak area integration revealed that the epoxy group grafting ratio of the epoxy-containing multi-arm hyperbranched resin in Comparative Example 2 was 58.2 mol%. After adding different molar amounts of DOPO to induce ring-opening reactions of the epoxy groups, phosphorus-containing multi-arm hyperbranched resins with a phosphorus group grafting ratio of 54.8 mol% (as in Example 2) and 27.6 mol% (as in Example 3) were obtained. Meanwhile, Figure 3 C and D respectively include the GPC elution curves of Examples 2, 3, and Comparative Example 2. The epoxy-based multi-arm hyperbranched resin obtained in Comparative Example 2 has a regular single-peak shape and a narrow molecular weight distribution, which conforms to the general rules of products obtained from atom transfer radical reactions. In contrast, the phosphorus-containing multi-arm hyperbranched resins obtained in Examples 2 and 3 generally exhibit a relatively wide molecular weight distribution, but it tends to narrow with increasing DOPO molar ratio. This is mainly because increasing the DOPO monomer ratio allows more epoxy groups in the epoxy-based multi-arm hyperbranched resin to participate in the reaction, thus making the functional groups in the phosphorus-containing multi-arm hyperbranched resin more uniform, and consequently narrowing the molecular weight distribution. Secondly, Figure 3The E value characterizes the lap shear strength of the steel sheet substrate bonding system of Examples 2, 3, and Comparative Example 2. A comparison of Example 2 with Examples 3 and Comparative Example 2 demonstrates that the hydroxyl groups formed after successful grafting of DOPO segments are beneficial to improving the adhesive performance of the resin. Furthermore, the comparison between Examples 2 and 3 shows that increasing the proportion of phosphorus-containing grafting groups also improves the adhesive performance of phosphorus-containing multi-arm hyperbranched resins. These characterization results collectively demonstrate that the adhesive performance of phosphorus-containing multi-arm hyperbranched resins can be adjusted by introducing phosphorus-containing groups and controlling the grafting ratio of phosphorus-containing groups.

[0087] Examples 4-8

[0088] 1. Sample preparation

[0089] (1) Example 4

[0090] Following steps 1-4 of Example 1, an adhesive sample was obtained on a steel sheet substrate.

[0091] (2) Examples 5-8

[0092] The bonding samples were prepared according to the method of Example 4, except that the bonding substrates were changed to aluminum sheet, glass, polycarbonate (PC) and wood, respectively.

[0093] 2. Characterization and Testing

[0094] Overlap shear strength test: Refer to Example 1.

[0095] 3. Comparison and Analysis of Test Results

[0096] Figure 4 The bonding performance of the same phosphorus-containing multi-arm hyperbranched resin used in Example 4 was compared between different substrates. Due to the abundance of hydroxyl groups, benzene rings in the DOPO segments, and a small number of epoxy groups that did not participate in the ring-opening reaction, the phosphorus-containing multi-arm hyperbranched resin can form hydrogen bonds, coordination bonds, or polar interactions with the surfaces of different substrates. On the surfaces of steel and aluminum sheets, the metal oxide layer (such as Fe-OH, Al-OH) can form strong coordination bonds and hydrogen bonds with epoxy and hydroxyl groups, resulting in the strongest interaction and thus high metal lap shear strength. The glass surface is also rich in hydroxyl groups (Si-OH), which can form a large number of hydrogen bonds with the polymer, resulting in slightly lower strength than metal but still high strength. Although polycarbonate (PC) is a polar polymer, it has fewer surface-active groups and mainly relies on hydrogen bonds and polar interactions, resulting in relatively low bonding strength. The wood surface is rich in cellulose hydroxyl groups, which can also form strong hydrogen bonds, but due to the low strength of the wood itself, the actual bonding strength is only slightly higher than that of PC. In summary, the phosphorus-containing multi-arm hyperbranched resin can effectively bond to different substrate surfaces, demonstrating a certain degree of versatility.

[0097] Example 9, Comparative Example 3

[0098] 1. Sample preparation

[0099] (1) Example 9

[0100] Step 1: Prepare a phosphorus-containing multi-arm hyperbranched resin sample according to steps 1-3 of Example 1.

[0101] Step 2: Using the phosphorus-containing multi-arm hyperbranched resin obtained in Step 1 of Example 5 above, hot-press it at 80 ℃ and 5 MPa for 5 min to obtain a phosphorus-containing multi-arm hyperbranched resin flame retardant test strip with a length of 125 mm, a width of 13 mm, and a thickness of 1.6 mm.

[0102] (2) Comparative Example 3

[0103] Step 1: Referring to Step 1 and Step 2 of Comparative Example 1, synthesize a linear phosphorus-containing resin.

[0104] Step 2: Referring to Step 2 of Example 9, the phosphorus-containing multi-arm hyperbranched resin was replaced with the linear phosphorus-containing resin of Step 1 of Comparative Example 3, and the linear phosphorus-containing resin flame retardant test strip was obtained after hot pressing.

[0105] 2. Characterization and Testing

[0106] Vertical burning (UL-94) test: The test was conducted in the HVUL2 vertical burning test system (ATLAS, USA) according to GB / T2408 "Determination of flammability of plastics - Horizontal and vertical methods". Each sample was tested 3 times, and the self-extinguishing time of the first and second self-extinguishing tests was recorded and the average value was taken.

[0107] 3. Comparison and Analysis of Test Results

[0108] Figure 5 The results presented are the flame retardant performance test results of the samples obtained in Example 9 and Comparative Example 3. Figure 5 Example A (phosphorus-containing multi-arm hyperbranched resin) showed that it could self-extinguish within 10 seconds after two ignitions, and there was no dripping phenomenon, indicating excellent flame retardant performance. Figure 5 B shows the vertical combustion test of Comparative Example 3 (linear phosphorus-containing resin). Its first self-extinguishing time was as long as 21.1 s, but the combustion height did not reach the top of the sample and there was no burning dripping phenomenon, indicating that it has certain flame retardant properties. Figure 5 C compared the average self-extinguishing times of the two samples from Example 9 and Comparative Example 3 on two separate occasions. In summary, compared to linear phosphorus-containing resins, phosphorus-containing multi-arm hyperbranched resins exhibit superior flame retardant properties due to their greater number of DOPO grafted segments, achieving a flame retardant level of UL94 V-0.

[0109] Example 10, Example 11, Comparative Example 4

[0110] 1. Sample preparation

[0111] (1) Example 10

[0112] Step 1: Prepare a phosphorus-containing multi-arm hyperbranched resin according to Step 1 of Example 2.

[0113] Step 2: Prepare a flame retardant test strip for phosphorus-containing multi-arm hyperbranched resin, referring to Step 2 of Example 9.

[0114] (2) Example 11

[0115] Step 1: Prepare a phosphorus-containing multi-arm hyperbranched resin according to Step 1 of Example 3.

[0116] Step 2: Prepare a flame retardant test strip for phosphorus-containing multi-arm hyperbranched resin, referring to Step 2 of Example 9.

[0117] (3) Comparative Example 4

[0118] Step 1: Referring to Step 1 and Step 2 of Example 1, synthesize epoxy-based multi-arm hyperbranched resin.

[0119] Step 2: Referring to Step 2 of Example 9, the phosphorus-containing multi-arm hyperbranched resin was replaced with the epoxy-based multi-arm hyperbranched resin of Comparative Example 4, and the epoxy-based multi-arm hyperbranched resin flame retardant test strip was obtained after hot pressing.

[0120] 2. Characterization and Testing

[0121] Vertical burning (UL-94) test: Performed according to Example 5.

[0122] 3. Comparison and Analysis of Test Results

[0123] Figure 6 The results presented are the flame retardant performance test results of the samples obtained in Examples 10, 11, and Comparative Example 4. Figure 6 Example A shows that Example 10 (a phosphorus-containing hyperbranched resin with a high DOPO grafting rate) can self-extinguish in a shorter time after two ignitions, and there is no dripping phenomenon, thus further improving the flame retardant performance. Figure 6 B shows the vertical combustion test of Example 11 (a phosphorus-containing multi-arm hyperbranched resin with low DOPO grafting rate). Its first self-extinguishing time was 14.9 s, but the combustion height did not reach the top of the sample and there was no burning dripping. It also has good flame retardant properties. Figure 6 C shows the vertical combustion test of Comparative Example 4 (epoxy multi-arm hyperbranched resin), which completely burned and melted 10 seconds after the first ignition, and the liquid dripped onto the cotton at the bottom of the test, failing to self-extinguish. Figure 6 The average self-extinguishing time of the two samples from Example 10 and Example 11 was compared twice. The above test results show that flame retardant properties can be imparted to multi-arm hyperbranched polyethylene copolymer resin by grafting flame-retardant segments, and the flame retardant properties of phosphorus-containing multi-arm hyperbranched resin can be adjusted by controlling the proportion of flame-retardant functional groups to achieve UL94 V-0 flame retardant performance.

Claims

1. A phosphorus-containing multi-arm hyperbranched resin, characterized in that: The phosphorus-containing multi-arm hyperbranched resin is prepared by a method comprising the following steps: Step 1: Using an α-diimide palladium catalyst, ethylene and 2-(2-bromoisobutyryloxy)ethyl acrylate (as shown in Formula I) are polymerized in a one-step "chain-walking" copolymerization mechanism to obtain a bromine-based multi-arm hyperbranched resin. I Step 2: The bromo-based multi-arm hyperbranched resin obtained in Step 1 is subjected to atom transfer radical polymerization with glycidyl methacrylate as shown in Formula II to obtain an epoxy-based multi-arm hyperbranched resin. II Step 3: The epoxy-based multi-arm hyperbranched resin obtained in Step 2 is subjected to a ring-opening reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as shown in Formula III to obtain a phosphorus-containing multi-arm hyperbranched resin. III.

2. The phosphorus-containing multi-arm hyperbranched resin as described in claim 1, characterized in that: The α-diimine palladium catalyst described herein is either α-diimine palladium catalyst 1 or 2 as follows: 。 3. A method for preparing a phosphorus-containing multi-arm hyperbranched resin as described in claim 1 or 2, characterized in that: The preparation method includes the following steps: Step 1: Using an α-diimide palladium catalyst, ethylene and 2-(2-bromoisobutyryloxy)ethyl acrylate (as shown in Formula I) are polymerized in a one-step "chain-walking" copolymerization mechanism to obtain a bromine-based multi-arm hyperbranched resin. I Step 2: The bromo-based multi-arm hyperbranched resin obtained in Step 1 is subjected to atom transfer radical polymerization with glycidyl methacrylate as shown in Formula II to obtain an epoxy-based multi-arm hyperbranched resin. II Step 3: The epoxy-based multi-arm hyperbranched resin obtained in Step 2 is subjected to a ring-opening reaction with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as shown in Formula III to obtain a phosphorus-containing multi-arm hyperbranched resin. III.

4. The preparation method according to claim 3, characterized in that: The third step is specifically implemented as follows: In a reaction vessel under nitrogen protection, epoxy-based multi-arm hyperbranched resin, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triphenylphosphine catalyst, and anhydrous organic solvent are added respectively. The reaction is carried out uniformly and thoroughly at a reaction temperature of 100-150℃ for 2-4 hours. After the reaction is completed, the obtained product is separated and purified to obtain phosphorus-containing multi-arm hyperbranched resin.

5. The preparation method according to claim 4, characterized in that: In step 3, the anhydrous organic solvent is one of the following anhydrous organic solvents: dimethyl sulfoxide, N,N-dimethylformamide, or N-methylpyrrolidone.

6. The preparation method according to claim 4, characterized in that: In step 3, the molar ratio of epoxy groups, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and triphenylphosphine catalyst in the epoxy-based multi-arm hyperbranched resin is 1:0.5–2.0:0.1–1.

7. The preparation method according to claim 6, characterized in that: In step 3, the molar ratio of epoxy groups, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and triphenylphosphine catalyst in the epoxy-based multi-arm hyperbranched resin is 1:1.5:0.

5.

8. The preparation method according to claim 4, characterized in that: In step 3, the initial concentration of the epoxy-based multi-arm hyperbranched resin is 0.1-5 mol / L, based on the initial concentration of the epoxy groups it contains.

9. The preparation method according to claim 4, characterized in that: In step 3, the reaction temperature is controlled at 110-130℃ and the reaction time is controlled at 2-4 h.

10. The application of the phosphorus-containing multi-arm hyperbranched resin as described in claim 1 as an intrinsically flame-retardant multifunctional adhesive.

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