Flame-retardant hydrophobic copolyamide nylon material, and preparation method and application thereof

Abstract

The application belongs to the technical field of high polymer materials, and discloses a flame-retardant hydrophobic copolymer nylon material, a preparation method and application thereof. A low steric hindrance short-chain perfluoroalkyl hydrophobic unit (modified with heptafluoro) and a DOPO flame-retardant unit are integrated in a single caprolactam monomer and embedded in a polymer main chain, so that a hydrophobic barrier is constructed to protect the flame-retardant structure from hydrolysis, a stable mechanism of synergistic enhancement of the two is constructed, and a technical bottleneck that the prior art cannot guarantee long-term safety and reliability of the material under high-humidity harsh environment at the same time is overcome.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and specifically relates to a flame-retardant hydrophobic copolymer nylon material, its preparation method, and its application. Background Technology

[0002] Nylon 6 (polycaprolactam), as an important engineering plastic, is widely used in the automotive, electronics, textile, and machinery manufacturing industries (CN119859160A, CN110041370A) due to its excellent mechanical strength, wear resistance, chemical corrosion resistance, and ease of processing. However, its two inherent defects—flammability and high water absorption—severely restrict its application in high-end, high-reliability fields. First, unmodified nylon 6 is a UL94 HB-class flammable material, which burns rapidly and produces molten droplets when in contact with a fire source, easily igniting other items and posing a significant fire safety hazard.

[0003] Therefore, the industry typically modifies nylon by adding flame retardants. Among these, halogen-free and environmentally friendly DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) and its derivatives have become a research hotspot due to their efficient gas-phase and condensed-phase flame-retardant mechanisms. However, current mainstream technologies mostly employ physical blending to add DOPO-type flame retardants to the nylon matrix. This method has two significant drawbacks: flame retardant precipitation and degradation of the material's mechanical properties (e.g., invention patents CN110041370A, CN112920410A, CN113337004A). Although invention patent CN119708470A introduces the DOPO structure into the nylon molecular chain through chemical bonding, it overlooks the strong polarity of the amide bond (-CONH-) in the nylon 6 molecular chain, making it prone to absorbing moisture from the environment. After absorbing water, the flame-retardant molecules in the material will hydrolyze and become ineffective due to prolonged exposure to a humid environment (e.g., invention patent CN110156840A). Furthermore, the material undergoes a plasticizing effect, leading to dimensional expansion, a significant decrease in rigidity and strength, and easy hydrolytic degradation at high temperatures. More importantly, in electronic and electrical applications, water absorption causes a sharp deterioration in its insulation properties, easily leading to leakage, short circuits, and even breakdowns under high voltage or high humidity environments.

[0004] Most importantly, flame retardancy and water absorption are not isolated issues, but rather interconnected and mutually reinforcing. On one hand, the intrusion of water molecules can interact with certain flame retardants (such as phosphorus-based flame retardants), potentially leading to their hydrolytic failure and weakening the long-term flame-retardant stability of the material. On the other hand, in electrical applications, the insulation degradation and leakage current caused by water absorption can lead to localized overheating. This overheating is precisely the potential ignition source for flammable substrates, forming a vicious cycle of "moisture absorption - insulation degradation - leakage overheating - material ignition." Although invention patent CN118834241B reports an α-aminocaprolactam flame retardant with PCN bond functional group substitution, its preparation method, and applications, this flame retardant possesses both flame-retardant and hydrophobic functions. However, the introduced hydrophobic portion is a trifluoro modified unit with a benzene ring group, which suffers from steric hindrance during polymerization and insufficient hydrophobic structure, resulting in high polymerization difficulty and poor hydrophobic performance.

[0005] Faced with the dilemma of existing technologies where flame retardancy and hydrophobic properties are disconnected or even mutually weakened, as well as the shortcomings of insufficient steric hindrance and hydrophobicity, a fundamental solution is urgently needed in this field. Therefore, developing a novel nylon material that integrates flame retardancy and hydrophobic functions in a stable and durable manner into the nylon polymer chain at the molecular structure level, achieving synergistic effects between the two, is key to overcoming the bottlenecks of existing technologies and has urgent demand and enormous market value. Summary of the Invention

[0006] In view of this, the present invention provides a flame-retardant hydrophobic copolynylon material, its preparation method and application. By integrating a short-chain perfluoroalkyl hydrophobic unit with low steric hindrance (heptafluoro modified) and a DOPO flame-retardant unit into a single caprolactam monomer and embedding it into the polymer backbone, a hydrophobic barrier is constructed to protect the flame-retardant structure from hydrolysis and a stable mechanism is formed through synergistic enhancement of the two, thus overcoming the technical bottleneck of existing technologies that cannot simultaneously ensure the long-term safety and reliability of materials in harsh high-humidity environments.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A modified caprolactam monomer with both flame-retardant and hydrophobic properties has the following structural formula:

[0009] .

[0010] This invention also provides a method for preparing a modified caprolactam monomer with both flame-retardant and hydrophobic properties, comprising the following steps:

[0011] (1) 3-amino-2-caprolactam is reacted with a perfluoroalkyl compound containing an aldehyde group under an inert atmosphere to generate a caprolactam intermediate containing a hydrophobic perfluoroalkyl structure. The structural formula of the caprolactam intermediate is shown below:

[0012] ;

[0013] (2) The caprolactam intermediate obtained in step (1) is subjected to an addition reaction with DOPO to obtain the modified caprolactam monomer.

[0014] The beneficial effects of the above technical solution are as follows: the caprolactam intermediate containing a perfluoroalkyl hydrophobic structure reacts with DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) in an organic solvent through a pH bond addition reaction to the C=N bond, thereby introducing the flame-retardant structure of DOPO in the form of a covalent bond, and finally preparing a modified caprolactam monomer with both flame-retardant and hydrophobic properties.

[0015] The aldehyde-containing perfluoroalkyl compound is 2,2,3,3,4,4,4-heptafluorobutanal.

[0016] The synthetic route for the modified caprolactam monomer is shown below:

[0017] .

[0018] A flame-retardant and hydrophobic copolymer nylon material is prepared by anionic ring-opening copolymerization of the above-mentioned modified caprolactam monomer and caprolactam monomer; the structural formula of the flame-retardant and hydrophobic copolymer nylon material is shown below:

[0019] ;

[0020] Where x is 0.50 to 0.99, y is 0.01 to 0.50, and x + y = 1.

[0021] This invention also provides a method for preparing the above-mentioned flame-retardant hydrophobic copolymer nylon material, comprising the following steps:

[0022] The modified caprolactam monomer, lactam monomer, catalyst and activator are mixed and subjected to anionic ring-opening copolymerization reaction. After the reaction is completed, the product is precipitated, washed with water for extraction and dried to obtain the flame-retardant hydrophobic copolymer nylon material.

[0023] Preferably, the molar ratio of the modified caprolactam monomer to the lactam monomer is 0.01 to 1:1.

[0024] Preferably, the ratio of the total molar amount of the modified caprolactam monomer to the total molar amount of the lactam monomer, the molar amount of the catalyst, and the molar amount of the activator is 100:0.1~2:0.1~2.

[0025] Preferably, the catalyst is selected from sodium metal, sodium hydride, and sodium hydroxide; and the activator is selected from hexamethylene diisocyanate, toluene diisocyanate, and N-acetylcaprolactam.

[0026] Preferably, the solvent for precipitation is selected from acetone, diethyl ether, and tetrahydrofuran.

[0027] Preferably, the copolymerization reaction is carried out at a temperature of 160~220℃ for a time of 0.5~4 h;

[0028] The drying process involves vacuum drying at 50-100°C for 6-48 hours.

[0029] The synthesis route of the flame-retardant hydrophobic copolymer nylon material is shown below:

[0030] .

[0031] This invention also provides the application of the above-mentioned flame-retardant and hydrophobic copolymer nylon material in the preparation of new energy vehicle battery pack components, high-voltage electrical connectors, outdoor electronic equipment housings, special protective clothing or flame-retardant fabrics.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. Fundamentally improved durability and stability of flame-retardant and hydrophobic copolynylon materials. This invention directly anchors DOPO flame-retardant units and perfluoroalkane hydrophobic units to the nylon polymer backbone through chemical bonds, fundamentally solving the problem of easy migration and precipitation of functional components in physical blending methods. The obtained flame-retardant and hydrophobic properties originate from the material itself, thus exhibiting excellent durability, washability, and abrasion resistance, ensuring the reliability and safety of products during long-term use.

[0034] 2. The flame retardant and superhydrophobic properties produce a synergistic enhancement effect. This invention achieves this synergistic effect through molecular structure design:

[0035] Hydrophobic structure ensures flame retardancy: Perfluoroalkane side chains have extremely low surface energy, forming a dense hydrophobic layer on the material surface. This effectively prevents moisture and even oily contaminants from penetrating the nylon matrix. This not only maintains the material's dimensional stability and electrical insulation, but more importantly, it provides excellent protection for the DOPO flame-retardant structure, completely preventing hydrolysis and failure due to contact with moisture or chemicals. This ensures the material maintains stable and highly efficient flame-retardant performance even in harsh environments such as extreme humidity and acid rain.

[0036] Flame-retardant structure protects the safety chain: DOPO's superior flame retardancy acts as the final safety line, cutting off the risk of overheating or open flames that may be caused by other factors. Together, they create a comprehensive and advanced safety guarantee, from "actively resisting environmental attacks" to "passively preventing fires."

[0037] 3. Simplified preparation process, facilitating industrialization. Since all functionalities are introduced at the monomer stage, the final polymerization process is fully compatible with the anionic polymerization process of ordinary nylon, eliminating the need for complex post-processing steps (such as surface coatings). This not only simplifies the production process and reduces energy consumption and costs but also avoids potential damage to the material's intrinsic properties caused by post-processing, thus enabling large-scale industrial production.

[0038] 4. Excellent comprehensive performance and broad application prospects. The copolymer nylon material prepared by this invention achieves excellent flame retardancy and hydrophobicity. Because the functional groups are linked by stable chemical bonds and uniformly distributed, they have minimal impact on the bulk properties of the nylon matrix, such as mechanical strength, thus achieving a balance between high performance and good processability. This makes it widely applicable in fields with extremely high requirements for material safety and surface resistance, such as new energy vehicle battery packs, high-voltage electrical connectors, outdoor communication equipment housings in harsh environments, and special chemical protective clothing. Detailed Implementation

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1: Synthesis of flame-retardant and hydrophobic modified caprolactam monomer

[0041] (1) Synthesis of hydrophobic intermediates containing aldehyde groups

[0042] In a 250 mL three-necked round-bottom flask equipped with a magnetic stirrer, thermometer, and constant-pressure dropping funnel, 31.4 mmol of 2,2,3,3,4,4,4-heptafluorobutanal, 31.4 mmol of anhydrous magnesium sulfate, and 100 mL of anhydrous ethanol were added. Under nitrogen protection, the reaction system was kept at room temperature, and a solution of 3-amino-2-caprolactam (31.4 mmol) dissolved in 20 mL of anhydrous ethanol was slowly added dropwise using a constant-pressure dropping funnel. After the addition was complete, a catalytic amount of glacial acetic acid (0.5 mL) was added, and the reaction solution was heated to 70 °C and stirred under reflux for 8 hours. The reaction progress was monitored by thin-layer chromatography. After the reaction was completed, the mixture was cooled to room temperature, and most of the ethanol was removed by rotary evaporation under reduced pressure. The crude product was washed with petroleum ether (3 × 30 mL) and recrystallized to obtain a white caprolactam intermediate with a yield of 88%. The structural formula of the caprolactam intermediate is shown below.

[0043] ;

[0044] (2) Synthesis of modified caprolactam monomers with both flame retardant and hydrophobic properties

[0045] In a 100 mL round-bottom flask, the caprolactam intermediate (14.4 mmol) and DOPO (15.8 mmol) obtained in step (1) were added to 50 mL of N,N-dimethylformamide (DMF) to dissolve them; the reaction system was heated to 120 °C and refluxed for 12 hours; the reaction progress was monitored by thin-layer chromatography until the reaction was complete; after the reaction was completed, the mixture was cooled to room temperature and poured into 200 mL of ice water, and a white solid precipitated; the solid was filtered and washed with a large amount of deionized water until neutral, and the solid was dried in a vacuum drying oven at 60 °C for 24 hours to obtain a modified caprolactam monomer with both flame retardant and hydrophobic properties, with a yield of 80%; the structural formula of the modified caprolactam monomer is shown below:

[0046] .

[0047] Example 2: Preparation of low-proportion modified monomer (1%) copolymer

[0048] In a dry 100 mL glass polymerization tube, accurately weigh caprolactam (99 mmol) and the modified caprolactam monomer prepared in Example 1 (1.0 mmol); Deoxygenation: Connect the polymerization tube to a vacuum-nitrogen dual-row system and perform three cycles of vacuuming and filling with high-purity nitrogen; Melting: Under nitrogen protection, place the polymerization tube in a silicone oil bath preheated to 120°C for melting; turn on the top-mounted mechanical stirrer and stir evenly at 300 rpm; quickly weigh sodium catalyst (0.5 mmol) and activator hexamethylene diisocyanate (HDI, 1.0 mmol), rapidly add them to the polymerization tube under a continuous nitrogen flow, and immediately seal the tube opening; rapidly raise the oil bath temperature to 160°C, and simultaneously increase the mechanical stirring speed to 500 rpm, and carry out anionic ring-opening copolymerization reaction for 3 hours; after the reaction, remove the polymerization tube from the oil bath, and pour the polymer melt while hot into a 200 mL glass container. The solidified polymer particles were settled in mL of diethyl ether; the solid was crushed to obtain polymer particles; the polymer particles were transferred to a Soxhlet extractor and continuously washed with boiling deionized water for 24 hours; the washed polymer particles were placed in a vacuum drying oven and dried at 80°C for 24 hours to constant weight to obtain a flame-retardant hydrophobic copolynylon material, the structural formula of which is shown below:

[0049]

[0050] Where x is 0.99 and y is 0.01.

[0051] Example 3: Preparation of copolymer with a high proportion of modified monomer (20%)

[0052] In a dry 100 mL glass polymerization tube, caprolactam (80.0 mmol) and the modified caprolactam monomer prepared in Example 1 (20.0 mmol) were accurately weighed. The deoxygenation process was the same as in Example 2. Melting: Under nitrogen protection, the polymerization tube was heated in a 120°C oil bath. A top-mounted mechanical stirrer was turned on, and the mixture was stirred at 300 rpm until homogeneous. Sodium hydroxide catalyst (2.0 mmol) and N-acetylcaprolactam activator (AcCL, 2.0 mmol) were rapidly weighed and added to the polymerization tube under a continuous nitrogen flow, and the tube opening was immediately sealed. The oil bath temperature was rapidly increased to 200°C, and anionic ring-opening copolymerization was carried out at 500 rpm for 1 hour. After the reaction, the polymer melt was poured into a 200 mL solution of acetone and diethyl ether to settle and solidify. Subsequent crushing, washing, extraction, and drying steps were the same as in Example 2. A flame-retardant hydrophobic copolymer nylon material was obtained, with the following structural formula:

[0053]

[0054] Where x is 0.80 and y is 0.20.

[0055] Example 4: Preparation of copolymers with a moderate proportion of modified monomers (10%)

[0056] In a dry 100 mL glass polymerization tube, accurately weigh caprolactam (90.0 mmol) and the modified caprolactam monomer prepared in Example 1 (10.0 mmol); deoxygenation procedure is the same as in Example 2; melting: under nitrogen protection, place the polymerization tube in a 120°C oil bath for heating and melting; turn on the top-mounted mechanical stirrer and stir evenly at 300 rpm; quickly weigh out the catalyst sodium hydride (NaH, 1.0 mmol) and the activator hexamethylene diisocyanate (HDI, 1.0 mmol), and rapidly add them to the polymerization tube under a continuous nitrogen flow, and immediately seal the tube opening; raise the oil bath temperature to 180°C and increase the stirring speed to 500 rpm to carry out anionic ring-opening copolymerization reaction for 2 hours; after the reaction is completed, pour the hot polymer melt into a 200 mL glass container. The polymer particles were settled and solidified in a mixed solution of acetone and tetrahydrofuran; the solid was crushed to obtain polymer particles; the polymer particles were transferred to a Soxhlet extractor and continuously washed with boiling deionized water for 24 hours; the washed polymer particles were dried in a vacuum drying oven at 50°C for 48 hours to obtain a flame-retardant hydrophobic copolynylon material, the structural formula of which is shown below:

[0057]

[0058] Where x is 0.90 and y is 0.10.

[0059] Example 5: Validation of different catalyst combinations (NaOH / AcCl)

[0060] In a dry 100 mL glass polymerization tube, caprolactam (90.0 mmol) and the flame-retardant hydrophobic modified caprolactam monomer prepared in Example 1 (10.0 mmol) were accurately weighed. The deoxygenation process was the same as in Example 2. Melting: Under nitrogen protection, the polymerization tube was placed in a 120°C oil bath for melting. The mixture was heated to melt. A top-mounted mechanical stirrer was turned on and stirred at 300 rpm until homogeneous. Sodium hydroxide catalyst (NaOH, 2.0 mmol) and activator N-acetylcaprolactam (AcCL, 2.0 mmol) were quickly weighed and added to the polymerization tube under a continuous nitrogen flow, and the tube opening was immediately sealed. The oil bath temperature was raised to 170°C, and the mechanical stirring speed was increased to 500 rpm for anionic ring-opening copolymerization for 2.5 hours. Subsequent sedimentation, solidification, crushing, water washing, extraction, and drying steps were the same as in Example 2. A flame-retardant hydrophobic copolymer nylon material was obtained, with the following structural formula:

[0061]

[0062] Where x is 0.90 and y is 0.10.

[0063] Comparative Example 1: Preparation of ordinary nylon 6

[0064] The difference from Example 2 is that 100.0 mmol caprolactam was used instead of 99 mmol caprolactam and 1.0 mmol modified caprolactam monomer; the catalyst was 0.5 mmol sodium hydroxide; the activator was 1.0 mmol HDI; and the anionic ring-opening copolymerization reaction was carried out at 180°C for 2 hours. All other operations were the same. Ordinary nylon 6 particles were obtained.

[0065] Comparative Example 2: Preparation of Physically Blended Modified Nylon

[0066] Take 25 kg of ordinary nylon 6 particles prepared in Comparative Example 1, add 2.5 kg of a mixture of commercially available DOPO and 2,2,3,3,4,4,4-heptafluorobutyraldehyde (the amount of the mixture is 10% of the mass of ordinary nylon 6 particles), mix in a high-speed mixer for 10 minutes, and then melt-blend and granulate through a twin-screw extruder to obtain physically blended modified nylon.

[0067] Comparative Example 3: Preparation of Flame-Retardant Nylon Copolymers Without Hydrophobic Segments

[0068] First, DOPO-modified caprolactam monomers without hydrophobic segments were prepared. The specific steps are as follows: Under nitrogen protection, DOPO (10.0 mmol) and p-aldehyde benzoic acid (10.0 mmol) were dissolved in 50 mL of anhydrous toluene, and a catalytic amount of triethylamine (0.10 mmol) was added. The mixture was refluxed at 110 °C for 12 hours. After post-treatment and purification by column chromatography, DOPO intermediates containing aldehyde groups were obtained (yield of approximately 98%).

[0069] Subsequently, 8.0 mmol of the aldehyde-containing DOPO intermediate and 8.8 mmol of 3-amino-2-caprolactam were dissolved in 40 mL of anhydrous ethanol, and 0.05 mL of glacial acetic acid was added as a catalyst. The mixture was refluxed at 70 °C for 8 hours to carry out a Schiff base reaction. After cooling, crystallization, filtration, and vacuum drying, the target monomer (yield approximately 85%) was obtained. Then, caprolactam (90.0 mmol) and DOPO-modified caprolactam monomer (10.0 mmol) were accurately weighed into a dry 100 mL glass polymerization tube. The deoxygenation and melting operations were the same as in Example 2. Sodium hydride (NaH, 1.0 mmol) and HDI (1.0 mmol) were added as catalysts, the tube was sealed, and the reaction was carried out at 180 °C and 500 rpm for 2 hours. The subsequent sedimentation, solidification, crushing, water washing, extraction, and drying steps were the same as in Example 2. A flame-retardant nylon copolymer without hydrophobic segments was obtained.

[0070] Comparative Example 4: Preparation of Flame-Retardant Nylon Copolymers Without Hydrophobic Segments

[0071] First, a DOPO-modified caprolactam monomer without hydrophobic properties was prepared, namely a DOPO intermediate containing an aldehyde group, following the same steps as in Comparative Example 3.

[0072] Subsequently, caprolactam (80.0 mmol) and DOPO intermediate containing aldehyde groups (20.0 mmol) were accurately weighed into a dry 100 mL glass polymerization tube; the deoxygenation and melting operations were the same as in Example 2; sodium hydride catalyst (NaOH, 1.0 mmol) and activator HDI (1.0 mmol) were added, the tube was sealed, and the reaction was carried out at 180°C and 500 rpm for 2 hours; the subsequent sedimentation, solidification, crushing, water washing, extraction, and drying steps were the same as in Example 2; flame-retardant nylon copolymer was obtained.

[0073] The products of each embodiment and the comparative example were subjected to performance tests:

[0074] 1. Tensile property test:

[0075] The samples were tested in accordance with the GB / T 1040.2-2022 standard.

[0076] 2. Flame retardant release test:

[0077] The test was conducted according to the China Petroleum and Chemical Industry Federation standard T / CPCIF 0194-2022 "Exudation Test of Powder Flame Retardants in Thermoplastic Plastics": 0.2 wt% carbon black was added to the resin, and samples were prepared by extrusion and injection molding. An accelerated exudation method was used, with the samples placed in a constant temperature and humidity chamber at (85±2)℃ and (85±2)%RH. The appearance of the samples was recorded daily, observing for any flame retardant exudation on the surface, for 7 consecutive days. The test results are shown in Table 1.

[0078] 3. Water contact angle test:

[0079] The test was conducted at 20℃ and 65% humidity. 5 μL of ultrapure water was added and the test was completed within 10 seconds of contacting the sample surface. The test was repeated 10 times, and the average value was taken. The test sample was a strip (150 mm × 10 mm × 4 mm) prepared by injection molding. The test results are shown in Table 1.

[0080] 4. Flame retardant performance test:

[0081] Vertical burning (UL94) tests were conducted according to the method described in national standard GB / T 2408-2021. The sample size was 130mm × 13mm × 3mm. The test results are shown in Table 1.

[0082] Table 1

[0083]

[0084] Examples 2-5 all used flame-retardant and hydrophobic modified caprolactam monomers to obtain the target materials through anionic ring-opening copolymerization. By covalently bonding DOPO flame-retardant units and perfluoroalkane hydrophobic units to the nylon backbone, the material achieved intrinsic flame retardancy and high hydrophobicity while maintaining the inherent excellent mechanical properties of nylon.

[0085] Flame retardancy analysis: As shown in Table 1, the proportion of modified monomers is the key factor determining the flame retardancy rating. The LOI value of the nylon material in Comparative Example 1 is 21.0%, indicating a low flame retardancy rating (V-2). However, Examples 4, 5 (10%), and Example 3 (20%) all achieve the highest V-0 rating. Although the nylon material prepared by blending flame retardants in Comparative Example 2 also achieves a V-0 rating (33.5%), it exhibits greater flame retardant precipitation, potentially leading to a lack of flame retardancy later on. This indicates that the covalently bonded DOPO structure provides efficient and stable flame retardancy.

[0086] Hydrophobicity Analysis: Although Comparative Example 3 (containing only flame-retardant groups) achieved a flame retardancy of V-0, its water contact angle was only 80°, making it a hydrophilic material like ordinary nylon (Comparative Example 1). When the amount of modified monomer added was 10%-20%, the water contact angle significantly increased (109°-120°), showing a significant hydrophobic effect compared to Comparative Example 3. Therefore, the barrier formed by the hydrophobic perfluoroalkane can effectively inhibit moisture intrusion and protect the nylon matrix. More importantly, the PH bond is a key site for DOPO to chemically react and attach to the polymer chain. It has a certain polarity and is easily broken under the action of water (especially hot water, acidic or alkaline conditions), generating phosphorous acid or its derivatives, causing a reduction or failure of flame retardant performance. Therefore, the strong hydrophobic properties can also protect the DOPO flame-retardant structure from hydrolysis or damage, ensuring the long-term reliability of the material in harsh humid and hot environments.

[0087] Mechanical Property Analysis: The most prominent and unexpected effect of this invention lies in the significant mechanical enhancement exhibited by the flame-retardant and hydrophobic copolynylon materials prepared with perfluoroalkyl modified monomers (Example 4, tensile strength 73 MPa; Example 3, tensile strength 70 MPa) compared to the equivalent proportions of intrinsically flame-retardant non-fluorine samples (Comparative Example 3, tensile strength 68 MPa; Comparative Example 4, tensile strength 63 MPa). The fundamental reason is that the polar perfluoroalkyl chains have excellent compatibility with the nylon matrix and achieve a tight interfacial bond through strong dipole-dipole interactions. Simultaneously, their inherent ultra-high rigidity allows them to unexpectedly act as covalently bonded "nano-reinforcing fibers" while functioning as hydrophobic groups, thereby simultaneously improving the material's strength and toughness. This discovery indicates that the perfluoro modification strategy is not a simple functional additive but rather achieves a synergistic effect, unexpectedly obtaining superior mechanical properties compared to conventional flame-retardant nylons while imparting top-tier flame-retardant and hydrophobic properties. This is a breakthrough effect that cannot be achieved through physical blending or even non-fluorine chemical modification.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modified caprolactam monomer possessing both flame-retardant and hydrophobic properties, characterized in that, The structural formula is as follows: 。 2. The method for preparing a modified caprolactam monomer with both flame-retardant and hydrophobic properties according to claim 1, characterized in that, Includes the following steps: (1) 3-amino-2-caprolactam is reacted with a perfluoroalkyl compound containing an aldehyde group under an inert atmosphere to generate a caprolactam intermediate containing a hydrophobic perfluoroalkyl structure. The structural formula of the caprolactam intermediate is shown below: ； (2) The caprolactam intermediate obtained in step (1) is subjected to an addition reaction with DOPO to obtain the modified caprolactam monomer.

3. A flame-retardant and hydrophobic copolymer nylon material, characterized in that, The modified caprolactam monomer of claim 1 is prepared by anionic ring-opening copolymerization with a lactam monomer; the structural formula of the flame-retardant hydrophobic copolymer nylon material is shown below: Where x is 0.50 to 0.99, y is 0.01 to 0.50, and x + y = 1.

4. The method for preparing a flame-retardant hydrophobic copolymer nylon material according to claim 3, characterized in that, Includes the following steps: The modified caprolactam monomer, lactam monomer, catalyst and activator are mixed and subjected to anionic ring-opening copolymerization reaction. After the reaction is completed, the product is precipitated, washed with water for extraction and dried to obtain the flame-retardant hydrophobic copolymer nylon material.

5. The method for preparing a flame-retardant hydrophobic copolymer nylon material according to claim 4, characterized in that, The molar ratio of the modified caprolactam monomer to the lactam monomer is 0.01 to 1:

1.

6. The method for preparing a flame-retardant hydrophobic copolymer nylon material according to claim 4, characterized in that, The ratio of the total molar amount of the modified caprolactam monomer to the total molar amount of the lactam monomer, the molar amount of the catalyst, and the molar amount of the activator is 100:0.1~2:0.1~2.

7. The method for preparing a flame-retardant hydrophobic copolymer nylon material according to claim 4, characterized in that, The catalyst is selected from one of sodium metal, sodium hydride, and sodium hydroxide; the activator is selected from one of hexamethylene diisocyanate, toluene diisocyanate, and N-acetylcaprolactam.

8. The method for preparing a flame-retardant hydrophobic copolymer nylon material according to claim 4, characterized in that, The solvent used for precipitation is selected from acetone, diethyl ether, and tetrahydrofuran.

9. The method for preparing a flame-retardant hydrophobic copolymer nylon material according to claim 4, characterized in that, The copolymerization reaction is carried out at a temperature of 160~220℃ for a time of 0.5~4 h. The drying process involves vacuum drying at 50-100°C for 6-48 hours.

10. The application of the flame-retardant and hydrophobic copolymer nylon material according to claim 3 in the preparation of new energy vehicle battery pack components, high-voltage electrical connectors, outdoor electronic equipment housings, special protective clothing or flame-retardant fabrics.

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