Flame-retardant recycled impregnant and method of making

Abstract

This invention discloses a flame-retardant recyclable impregnating agent and its preparation method, relating to the field of impregnating agent materials. The flame-retardant recyclable impregnating agent comprises the following components in parts by weight: 45-60 parts of monofunctional acrylate monomer, 30-40 parts of difunctional acrylate monomer, 9-14 parts of reactive flame retardant, 0.2-0.5 parts of polymerization inhibitor, and 0.6-1.0 parts of initiator; the structural formula of the reactive flame retardant is as follows. This invention designs and synthesizes an environmentally friendly, low-toxicity phosphorus-based reactive flame retardant, which is chemically bonded and cured with acrylate monomer to form a novel flame-retardant recyclable impregnating agent, endowing the impregnating agent with high heat resistance, high aging resistance, and high flame retardancy; simultaneously, this flame retardant possesses the function of a surfactant, is easily washed with water, and can quickly separate and efficiently recycle acrylate monomers from water, improving the utilization rate of raw materials and minimizing environmental pollution.

Description

Technical Field

[0001] This invention relates to the field of impregnating agent materials, specifically to a flame-retardant recyclable impregnating agent and its preparation method. Background Technology

[0002] During the casting process, aluminum alloy castings may experience uneven crystal shrinkage and difficulty in gas escape, resulting in a large number of micropores or cracks. Therefore, it is necessary to seal and reinforce these micropore defects to restore the airtightness of the casting while improving its hardness and rigidity.

[0003] Acrylic ester vacuum impregnation agents are liquid substances mainly composed of acrylate monomers with different functionalities in a certain proportion, supplemented with initiators, polymerization inhibitors and surfactants. Due to the good chemical stability, mechanical properties and weather resistance of ester monomers and thermosetting materials, they have become the most widely used micropore defect repair agents for metal die castings.

[0004] However, general-purpose acrylic vacuum impregnation agents are not recyclable. The impregnating agent on the casting surface, along with the cleaning water, becomes waste liquid, resulting in raw material waste and increased wastewater treatment costs. Therefore, developing recyclable acrylic vacuum impregnation agents has become the mainstream direction in this field.

[0005] By utilizing the hydrophobicity of acrylates and the density difference between them and water, they can be effectively separated from water and recycled. This not only improves the utilization rate of raw materials but also minimizes environmental pollution. Currently, recyclable impregnating agents are primarily separated from water and recycled using surfactants and separating agents.

[0006] However, existing recyclable acrylate impregnating agents generally use a high proportion of soft acrylate monomers (such as lauryl methacrylate) and a very low proportion or no water-soluble functional monomers (such as hydroxyethyl methacrylate). This results in poor water washability of the impregnating agents, so surfactants need to be added to the impregnating agent formulation to improve water washability. Since surfactants do not participate in the polymerization reaction of acrylate monomers, they are prone to volatilization and exudation during thermosetting, which further aggravates the low hardness of the cured polymer of soft acrylate monomers. At the same time, the heat resistance and aging resistance are poor. Moreover, existing recyclable impregnating agents do not have flame retardancy, which poses a significant safety hazard in the production, use and storage process.

[0007] Furthermore, CN104387522A discloses a flame-retardant acrylate-based organic impregnating agent for sealing and reinforcement, and its preparation method. This method utilizes the highly efficient flame-retardant properties of bromine to bond it to the methacrylate monomer molecular chain, significantly improving the flame-retardant performance of the cured impregnating agent, achieving an oxygen index of over 27%. However, halogenated flame retardants are inherently toxic and easily produce dense smoke, dioxins, and hydrogen halides during combustion, posing a threat to the environment and human health. Currently, their application in electronic products and new energy vehicles is restricted.

[0008] Therefore, developing an environmentally friendly, low-toxicity, highly efficient, flame-retardant, and high-performance recyclable acrylate impregnating agent is of great application significance. Summary of the Invention

[0009] The purpose of this invention is to provide a flame-retardant recyclable impregnating agent and its preparation method.

[0010] This invention designs and synthesizes an environmentally friendly, low-toxicity phosphorus-based reactive flame retardant, which is chemically bonded and cured with acrylate monomers to form a novel flame-retardant recyclable impregnating agent. This impregnating agent possesses high heat resistance, high aging resistance, and high flame retardancy. At the same time, this flame retardant has the function of a surfactant, is easy to wash with water, and can quickly separate and efficiently recycle acrylate monomers from water, thereby improving the utilization rate of raw materials and minimizing environmental pollution.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides a flame-retardant recyclable impregnating agent, wherein the flame-retardant recyclable impregnating agent comprises the following components in parts by weight: 45-60 parts of monofunctional acrylate monomer, 30-40 parts of difunctional acrylate monomer, 9-14 parts of reactive flame retardant, 0.2-0.5 parts of polymerization inhibitor, and 0.6-1.0 parts of initiator; The structural formula of the reactive flame retardant is as follows: ; In the formula, R1 is H or Me; n = 1, 2, or 3; R2 is H, Me, or ; X is and / or .

[0012] In the flame-retardant recyclable impregnating agent of the present invention, the acrylate monomers are mainly divided into monofunctional and difunctional monomers; wherein, the monofunctional acrylate monomers are selected from alkyl esters with 5-25 carbon atoms; preferably, they are selected from at least one of octyl methacrylate, decyl methacrylate, isodecyl methacrylate, isobornyl methacrylate, lauryl methacrylate, diethylene glycol ethyl ether methacrylate, tridecanol methacrylate, tetradecanol methacrylate, and octadecyl methacrylate.

[0013] More preferably, the monofunctional acrylate monomer is selected from at least one of lauryl methacrylate, isodecanyl methacrylate, and tridecyl methacrylate.

[0014] The bifunctional acrylate is selected from dialkyl esters with 10-25 carbon atoms; preferably from at least one of dimethyl acrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,10-decanediol dimethacrylate, tripropylene glycol diacrylate, and triethylene glycol dimethacrylate.

[0015] More preferably, the difunctional acrylate is selected from at least one of 1,6-hexanediol dimethacrylate, 1,10-decanediol dimethacrylate, and triethylene glycol dimethacrylate.

[0016] According to the flame-retardant recyclable impregnating agent of the present invention, preferably, the initiator is selected from peroxide or azo compound initiators.

[0017] More preferably, the initiator is selected from at least one of lauroyl peroxide, diisopropylbenzene peroxide, tert-butyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyronitrile.

[0018] More preferably, the initiator is azobisisobutyronitrile, azobisisoheptanenitrile, or dimethyl azobisisobutyrate.

[0019] According to the flame-retardant recyclable impregnating agent of the present invention, preferably, the polymerization inhibitor is selected from at least one of hydroquinone, benzoquinone, anthraquinone, 1,4-naphthoquinone, tert-butylcatechol, and 2,6-dibutyl-p-cresol.

[0020] More preferably, the polymerization inhibitor is hydroquinone, tert-butylcatechol, or 2,6-dibutyl-p-cresol.

[0021] Another aspect of the present invention provides a method for preparing any one of the above-mentioned flame-retardant recyclable impregnating agents, wherein the preparation method includes the following steps: The monofunctional acrylate monomer, difunctional acrylate monomer, reactive flame retardant, polymerization inhibitor and initiator are mixed evenly at room temperature to obtain the flame-retardant recyclable impregnating agent.

[0022] The reactive flame retardant is preferably prepared through the following steps: Phosphorus oxychloride (POCl3) reacts with pentaerythritol phosphate (PEPA) to obtain PEPA-PODC (pentaerythritol phosphate-dichlorophosphate compound); then, PEPA-PODC is grafted with DOPO-HQ [10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide] and hydroxy acrylate (HA) respectively in a one-pot process to obtain the reactive flame retardant, denoted as PEPA-DOPQ-HA.

[0023] In the preparation of the reactive flame retardant, preferably, the reaction between phosphorus oxychloride (POCl3) and pentaerythritol phosphate (PEPA) is carried out in the presence of triethylamine; more preferably, the reaction is carried out in THF (tetrahydrofuran) solvent at 0°C to room temperature.

[0024] In the preparation of the reactive flame retardant, preferably, the one-pot process is carried out under the action of triethylamine; more preferably, the one-pot process is carried out in THF solvent at 0°C to room temperature.

[0025] In a preferred embodiment, the reactive flame retardant has the following reaction formula:

[0026] In the formula, R1 is H or Me; n = 1, 2 or 3; R2 is H, Me or X is and / or The two isomers corresponding to X do not need to be distinguished or separated, and have virtually no impact on the flame retardant properties of the impregnating agent.

[0027] In the preparation of the reactive flame retardant, preferably, the hydroxy acrylate (HA) is selected from 2-hydroxyethyl acrylate (HA). HEA), hydroxyethyl methacrylate (HEA), hydroxyethyl methacrylate HEMA), hydroxypropyl methacrylate (HEMA), HPMA), 2-hydroxypropyl isobutylene ester (HPMA), ), 4-hydroxybutyl acrylate ( 4HBA), 4-hydroxybutyl methacrylate ( 4HBMA), 3-(acryloyloxy)-2-hydroxypropyl methacrylate ( One of them is AO-HPMA.

[0028] In the preparation of the reactive flame retardant, preferably, the molar ratio of phosphorus oxychloride (POCl3) to pentaerythritol phosphate (PEPA) is 2:1.

[0029] In the preparation of the reactive flame retardant, preferably, in the first step of the reaction, the molar ratio of triethylamine to phosphorus oxychloride is 1:1.

[0030] In the preparation of the reactive flame retardant, preferably, the molar ratio of PEPA-PODC to DOPO-HQ and hydroxy acrylate (HA) is 1:1:1.

[0031] In the preparation of the reactive flame retardant, preferably, in the one-pot process, the molar ratio of triethylamine to PEPA-PODC is 2:1.

[0032] Pentaerythritol phosphate (PEPA) is an intumescent flame retardant with a symmetrical cage-like structure. Due to its good char-forming properties, excellent thermal stability, and abundant carbon and acid sources, it is widely used in the preparation of phosphorus-containing flame retardant intermediates or for synergistic effects in mixed intumescent flame retardants. DOPO-HQ [10-(2,5-dihydroxyphenyl)-10-hydro-9-oxa-10-phosphaphenanthrene-10-oxide] is a phospholipid compound containing a phosphaphenanthrene ring and a phenol structure. It belongs to the green and environmentally friendly phosphorus-based flame retardants and has the characteristics of high thermal stability, low smoke and non-toxicity, low addition amount and minimal impact on the properties of polymer materials. It has been applied in various composite materials.

[0033] The reactive flame retardant (PEPA-DOPQ-HA) in this invention is a combined flame retardant prepared by chemically grafting phosphorus oxychloride (POCl3) with PEPA, hydroxy acrylate (HA), and DOPO-HQ, respectively. It achieves a synergistic flame retardant effect during combustion and can form a stronger, denser, and more stable phosphorus-rich closed char layer. Therefore, an addition of 9%-14% is sufficient to make the cured polymer of the impregnating agent reach the level of flame retardant material. Compared with existing flame retardants, the addition amount usually needs to be more than 30% to achieve higher flame retardancy.

[0034] The reactive flame retardant (PEPA-DOPQ-HA) of this invention has a cage-like phosphate ester and phosphenanthrene ring structure, which not only significantly improves the rigidity and hardness of the impregnating agent, but also significantly improves the high-temperature resistance and aging resistance of the cured polymer. Therefore, the application of the flame retardant also solves the problem that the hardness, heat resistance, and aging resistance of recyclable impregnating agents are difficult to meet the standards due to the large-dose use of soft monomers. In addition, the phenolic hydroxyl groups in the flame retardant have surface-active functions, which can provide wetting and activity to the contact surface of the casting, making it easy to clean off the casting surface; the cage-like phosphate ester, phosphenanthrene ring, and acrylate structure makes the flame retardant more compatible with acrylate monomers, promoting their rapid and efficient separation from water, thus resulting in a higher impregnating agent recovery rate.

[0035] The reactive flame retardant (PEPA-DOPQ-HA) of this invention is a reactive acrylic monomer that chemically bonds with other acrylic monomers to the polymer chain segments during the thermosetting process of the impregnating agent. This improves the thermal and dimensional stability of the polymer's linear structure and prevents flame retardant migration, thus ensuring that the flame retardant performance of the cured polymer is more durable.

[0036] The reactive flame retardant (PEPA-DOPQ-HA) of the present invention has the functions of both surfactant and separating agent. It can not only replace the surfactant in the impregnating agent formulation and avoid the serious defect of the workpiece surface being contaminated by the surfactant seeping out from the thermosetting body, but also avoid the decrease in the sealing performance of the impregnating agent on the die casting due to the use of the separating agent. Detailed Implementation

[0037] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0038] All numerical specifications in this invention (e.g., temperature, time, concentration, and weight, including ranges for each) are generally approximate values ​​that may be changed (+) or (-) in increments of 0.1 or 1.0. All numerical specifications are to be understood as being preceded by the term "about".

[0039] The preparation of the reactive flame retardant PEPA-DOPQ-HA includes the following steps: Under stirring, 61.3 g of phosphorus oxychloride (0.4 mol) was dissolved in 200 mL of tetrahydrofuran, and the mixture was kept in an ice bath at 0 °C. Then, PEPA (36.2 g, 0.2 mol) and triethylamine (40.4 g, 0.4 mol) dissolved in 100 mL of tetrahydrofuran were slowly added dropwise to the above solution. After the addition was complete, the mixture was stirred at 0 °C for 5 hours. The reaction mixture was then heated to room temperature and stirred for another 5 hours. The triethylamine hydrochloride was removed by filtration, and then tetrahydrofuran, triethylamine, and unreacted phosphorus oxychloride were removed by vacuum distillation to obtain pentaerythritol phosphate-dichlorophosphate (PEPA-PODC).

[0040] Under stirring, HA (0.2 mol) and triethylamine (40.4 g, 0.4 mol) were dissolved in 120 mL of tetrahydrofuran, and the mixture was kept in an ice bath at 0°C. Then, 100 mL of tetrahydrofuran solution containing PEPA-PODC (59.4 g, 0.2 mol) was slowly added to the above mixture. After the addition was complete, the reaction mixture was heated to room temperature and the reaction was continued at room temperature for 6 hours. Subsequently, DOPO-HQ (64.9 g, 0.2 mol) was slowly added to the above reaction system. The reaction was then continued at room temperature for 12 hours. The precipitated triethylamine hydrochloride and tetrahydrofuran were removed, and the residue was dissolved in dichloromethane. The residue was then washed with dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and deionized water, respectively. After drying and removing dichloromethane, the reactive flame retardant PEPA-DOPQ-HA was obtained.

[0041] Example 1

[0042] This embodiment provides a flame-retardant recyclable impregnating agent, prepared by mixing the following weight proportions: 55 parts lauryl methacrylate, 32 parts 1,10-decanediol dimethacrylate, 12 parts flame retardant PEPA-DOPQ-HEMA, 0.7 parts dimethyl azobisisobutyrate, and 0.3 parts 2,6-dibutyl-p-cresol.

[0043] The preparation method of flame retardant PEPA-DOPQ-HEMA is as follows: Under stirring, HEMA (26.0 g, 0.2 mol) and triethylamine (40.4 g, 0.4 mol) were dissolved in 120 mL of tetrahydrofuran, and the mixture was kept in an ice bath at 0°C. Then, 100 mL of tetrahydrofuran solution containing PEPA-PODC (59.4 g, 0.2 mol) was slowly added to the above mixture. After the addition was complete, the reaction mixture was heated to room temperature and the reaction was continued at room temperature for 6 hours. Subsequently, DOPO-HQ (64.9 g, 0.2 mol) was slowly added to the above reaction system. Then, the reaction was continued at room temperature for 12 hours. The precipitated triethylamine hydrochloride and tetrahydrofuran were removed, and the residue was dissolved in dichloromethane. The residue was then washed with dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and deionized water, respectively. After drying and removing dichloromethane, the reactive flame retardant PEPA-DOPQ-HEMA was obtained, with the following structural formula:

[0044] In the formula, X is and / or .

[0045] Example 2

[0046] This embodiment provides a flame-retardant recyclable impregnating agent, prepared by mixing the following weight proportions: 60 parts lauryl methacrylate, 30 parts 1,10-decanediol dimethacrylate, 9 parts flame retardant PEPA-DOPQ-HEMA, 0.8 parts dimethyl azobisisobutyrate, and 0.2 parts 2,6-dibutyl-p-cresol.

[0047] Example 3

[0048] This embodiment provides a flame-retardant recyclable impregnating agent, prepared by mixing the following weight proportions: 45 parts lauryl methacrylate, 40 parts 1,10-decanediol dimethacrylate, 14 parts flame retardant PEPA-DOPQ-AO-HPMA, 0.7 parts dimethyl azobisisobutyrate, and 0.3 parts 2,6-dibutyl-p-cresol.

[0049] The preparation method of flame retardant PEPA-DOPQ-AO-HPMA is as follows: Under stirring, 3-(acryloyloxy)-2-hydroxypropyl methacrylate (AO-HPMA, 42.4 g, 0.2 mol) and triethylamine (40.4 g, 0.4 mol) were dissolved in 120 mL of tetrahydrofuran and the mixture was kept in an ice bath at 0°C. Then, 100 mL of tetrahydrofuran solution containing PEPA-PODC (59.4 g, 0.2 mol) was slowly added to the above mixture. After the addition was complete, the reaction mixture was heated to room temperature and the reaction was continued at room temperature for 6 hours. Subsequently, DOPO-HQ (64.9 g, 0.2 mol) was slowly added to the above reaction system. The reaction was then continued at room temperature for 12 hours. The precipitated triethylamine hydrochloride and tetrahydrofuran were removed, and the residue was dissolved in dichloromethane. The residue was then washed with dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and deionized water, respectively. After drying and removing dichloromethane, the reactive flame retardant PEPA-DOPQ-AO-HPMA was obtained, with the following structural formula:

[0050] In the formula, X is and / or .

[0051] Example 4

[0052] This embodiment provides a flame-retardant recyclable impregnating agent, prepared by mixing the following weight proportions: 57 parts lauryl methacrylate, 31 parts 1,10-decanediol dimethacrylate, 11 parts flame retardant PEPA-DOPQ-AO-HPMA, 0.8 parts dimethyl azobisisobutyrate, and 0.2 parts 2,6-dibutyl-p-cresol.

[0053] Example 5

[0054] This embodiment provides a flame-retardant recyclable impregnating agent, prepared by mixing the following weight proportions: 50 parts isodecyl methacrylate, 39 parts 1,6-ethylene glycol dimethacrylate, 10 parts flame retardant PEPA-DOPQ-HEA, 0.6 parts azobisisoheptanenitrile, and 0.4 parts hydroquinone.

[0055] The preparation method of flame retardant PEPA-DOPQ-HEA is as follows: Under stirring, HEA (23.2 g, 0.2 mol) and triethylamine (40.4 g, 0.4 mol) were dissolved in 120 mL of tetrahydrofuran, and the mixture was kept in an ice bath at 0°C. Then, 100 mL of tetrahydrofuran solution containing PEPA-PODC (59.4 g, 0.2 mol) was slowly added to the above mixture. After the addition was complete, the reaction mixture was heated to room temperature and the reaction was continued at room temperature for 6 hours. Subsequently, DOPO-HQ (64.9 g, 0.2 mol) was slowly added to the above reaction system. Then, the reaction was continued at room temperature for 12 hours. The precipitated triethylamine hydrochloride and tetrahydrofuran were removed, and the residue was dissolved in dichloromethane. The residue was then washed with dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and deionized water, respectively. After drying and removing dichloromethane, the reactive flame retardant PEPA-DOPQ-HEA was obtained, with the following structural formula:

[0056] In the formula, X is and / or .

[0057] Example 6

[0058] This embodiment provides a flame-retardant recyclable impregnating agent, prepared by mixing the following weight proportions: 48 parts tridecyl methacrylate, 38 parts triethylene glycol dimethacrylate, 13 parts flame retardant PEPA-DOPQ-4HBMA, 0.7 parts azobisisobutyronitrile, and 0.3 parts tert-butylcatechol.

[0059] The preparation method of flame retardant PEPA-DOPQ-4HBMA is as follows: Under stirring, 4HBMA (31.6 g, 0.2 mol) and triethylamine (40.4 g, 0.4 mol) were dissolved in 120 mL of tetrahydrofuran, and the mixture was kept in an ice bath at 0°C. Then, 100 mL of tetrahydrofuran solution containing PEPA-PODC (59.4 g, 0.2 mol) was slowly added to the above mixture. After the addition was complete, the reaction mixture was heated to room temperature and the reaction was continued at room temperature for 6 hours. Subsequently, DOPO-HQ (64.9 g, 0.2 mol) was slowly added to the above reaction system. The reaction was then continued at room temperature for 12 hours. The precipitated triethylamine hydrochloride and tetrahydrofuran were removed, and the residue was dissolved in dichloromethane. The residue was then washed with dilute hydrochloric acid, saturated sodium bicarbonate aqueous solution, and deionized water, respectively. After drying and removing dichloromethane, the reactive flame retardant PEPA-DOPQ-4HBMA was obtained, with the following structural formula:

[0060] In the formula, X is and / or .

[0061] Comparative Example 1

[0062] This comparative example uses the formulation of Example 1, replacing the flame retardant PEPA-DOPQ-HEMA with DOPO-HQ. It is actually prepared by mixing the following components in parts by weight: 55 parts lauryl methacrylate, 32 parts decanediol dimethacrylate, 12 parts DOPO-HQ, 0.7 parts dimethyl azobisisobutyrate, and 0.3 parts 2,6-dibutyl-p-cresol.

[0063] Comparative Example 2

[0064] This comparative example uses the formulation of Example 1, replacing the flame retardant PEPA-DOPQ-HEMA with PEPA and DOPO-HQ. It is actually prepared by mixing the following components in parts by weight: 55 parts lauryl methacrylate, 32 parts decanediol dimethacrylate, 6 parts PEPA, 6 parts DOPO-HQ, 0.7 parts dimethyl azobisisobutyrate, and 0.3 parts 2,6-dibutyl-p-cresol.

[0065] Comparative Example 3

[0066] This comparative example uses the formulation of Example 2, replacing the flame retardant PEPA-DOPQ-HEMA with a surfactant commonly used in recyclable impregnating agents. It is actually prepared by mixing the following components in parts by weight: 60 parts lauryl methacrylate, 30 parts decanediol dimethacrylate, 9 parts nonylphenol polyoxyethylene ether surfactant (OP-10), 0.8 parts dimethyl azobisisobutyrate, and 0.2 parts 2,6-dibutyl-p-cresol.

[0067] The impregnating agents prepared from Examples 1-6 and Comparative Examples 1-3 were subjected to the following performance tests, and the results are shown in Tables 1 and 2.

[0068] 1) Curing hardness: Tested according to GB / T531.1-2008 Shore hardness tester method.

[0069] 2) Washability: Drill a 20mm deep M8 threaded hole on each of the top, bottom, and left sides of a 30mm×30mm×30mm aluminum block. Immerse the specimen in the impregnating agent and then remove it. After rinsing it in a tap water tank for 5 minutes, place it in a 90℃ hot water tank for 15 minutes to cure it. Then remove it and observe whether there is any residual adhesive on the surface of the specimen and in the threaded hole.

[0070] 3) Limiting Oxygen Index (LOI): Determined according to GB / T 10707-2008 (Oxygen Index Tester Combustion Test Method).

[0071] 4) High-temperature sealing performance at 204℃: The test sample is impregnated with the organic impregnating agent specified in the US military standard MIL-I-17563C. After curing, it is placed in a constant temperature aging chamber at 204℃ for 42 days. After the aging period, it is taken out, cooled to room temperature, and then the sealing performance is tested using the sealing performance test device specified in MIL-I-17563C. If there is no leakage, it means that the test sample has good high-temperature performance at 204℃; otherwise, it has poor high-temperature performance at 204℃.

[0072] 5) Aging resistance: The test sample is impregnated with the organic impregnating agent specified in the US military standard MIL-I-17563C using a dedicated impregnation test ring. After curing, the rings are placed in the following aging environments: ethylene glycol, 149°C, 14 days; hydraulic oil, 99°C, 14 days; alcohol, 23°C, 2 days; 18% sulfuric acid solution, 23°C, 2 hours. After the expiration period, the rings are removed and the sealing performance is tested using the sealing test device specified in MIL-I-17563C. If there is no leakage, the aging resistance of the test sample is good; otherwise, the aging resistance is poor.

[0073] 6) Curing degree: Weigh 2.4000-2.5000 grams of impregnating agent, heat to cure and make glue sticks, wipe off the oil stains on the surface of the glue sticks with oil-absorbing paper and weigh them, calculate the curing degree: Curing degree = solid weight / liquid weight.

[0074] Table 1 Performance Comparison of Examples and Comparative Examples

[0075] As can be seen from Table 1, in Examples 1-6, adding 9%-14% of the reactive flame retardant PEPA-DOPQ-HA can give the impregnating agent a better flame retardant effect, while maintaining the curing hardness, high-temperature sealing performance and aging resistance of the impregnating agent; therefore, the reactive flame retardant of the present invention is an ideal flame retardant material.

[0076] In Comparative Example 1, the formulation of Example 1 was used, and the flame retardant DOPO-HQ was used instead of the flame retardant of the present invention. However, since it is not a reactive flame retardant, heating will cause the flame retardant to migrate, etc., so the flame retardant effect of the impregnating agent is not particularly ideal.

[0077] In Comparative Example 2, the formulation of Example 1 was used, with flame retardants PEPA and DOPO-HQ used instead of the flame retardants of the present invention. Similarly, since neither of them are reactive flame retardants, the flame retardant effect of the impregnating agent was not ideal.

[0078] In Comparative Example 3, the formulation of Example 2 was used, and the surfactant OP-10 was used instead of the flame retardant of the present invention. Therefore, the impregnating agent does not have a flame retardant effect and is a flammable material. At the same time, since OP-10 cannot participate in the polymerization reaction, it eventually seeps out from the cured body, resulting in serious surface contamination of the workpiece. Therefore, the curing performance of the impregnating agent is difficult to meet the standards.

[0079] Table 2 Comparison of cleaning performance and recovery efficiency between the examples and comparative examples

[0080] As can be seen from Table 2, Examples 1-6 used flame retardants that function as both surfactants and separating agents, thus imparting water-washable properties and separation and recovery capabilities to the acrylate monomers. In comparison, DOPO-HQ in Comparative Examples 1 and 2 showed good water washability and separation effect, resulting in a higher recovery rate. Comparative Example 3 added 9% OP-10, which was easy to wash with water, but this led to severe emulsification of the impregnating agent and the washing water, resulting in poor separation effect and a poor recovery rate.

[0081] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A flame-retardant recyclable impregnating agent, characterized in that, The flame-retardant recyclable impregnating agent comprises the following components in parts by weight: 45-60 parts of monofunctional acrylate monomer, 30-40 parts of difunctional acrylate monomer, 9-14 parts of reactive flame retardant, 0.2-0.5 parts of polymerization inhibitor, and 0.6-1.0 parts of initiator; The structural formula of the reactive flame retardant is as follows: ； In the formula, R1 is H or Me; n = 1, 2, or 3; R2 is H, Me, or ; X is and / or .

2. The flame-retardant recyclable impregnating agent according to claim 1, characterized in that, The monofunctional acrylate monomer is selected from at least one of octyl methacrylate, decyl methacrylate, isodecyl methacrylate, isobornyl methacrylate, lauryl methacrylate, diethylene glycol ethyl ether methacrylate, tridecanol methacrylate, tetradecanol methacrylate, and octadecyl methacrylate.

3. The flame-retardant recyclable impregnating agent according to claim 1, characterized in that, The bifunctional acrylate is selected from at least one of dimethyl acrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,10-decanediol dimethacrylate, tripropylene glycol diacrylate, and triethylene glycol dimethacrylate.

4. The flame-retardant recyclable impregnating agent according to claim 1, characterized in that, The initiator is selected from at least one of lauroyl peroxide, diisopropylbenzene peroxide, tert-butyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, and dimethyl azobisisobutyronitrile.

5. The flame-retardant recyclable impregnating agent according to claim 1, characterized in that, The polymerization inhibitor is selected from at least one of hydroquinone, benzoquinone, anthraquinone, 1,4-naphthoquinone, tert-butylcatechol, and 2,6-dibutyl-p-cresol.

6. The flame-retardant recyclable impregnating agent according to claim 1, characterized in that, The monofunctional acrylate monomer is selected from at least one of lauryl methacrylate, isodecyl methacrylate, and tridecyl methacrylate. The bifunctional acrylate is selected from at least one of 1,6-hexanediol dimethacrylate, 1,10-decanediol dimethacrylate, and triethylene glycol dimethacrylate.

7. The flame-retardant recyclable impregnating agent according to claim 1, characterized in that, The initiator is azobisisobutyronitrile, azobisisoheptanenitrile, or dimethyl azobisisobutyrate; The polymerization inhibitor is hydroquinone, tert-butylcatechol, or 2,6-dibutyl-p-cresol.

8. A method for preparing a flame-retardant recyclable impregnating agent according to any one of claims 1-7, characterized in that, The preparation method includes the following steps: The monofunctional acrylate monomer, the difunctional acrylate monomer, the reactive flame retardant, the polymerization inhibitor, and the initiator are mixed uniformly at room temperature to obtain the flame-retardant recyclable impregnating agent.

9. The preparation method according to claim 8, characterized in that, The reactive flame retardant is prepared through the following steps: Phosphorus oxychloride reacts with pentaerythritol phosphate to obtain PEPA-PODC; then, PEPA-PODC is grafted with DOPO-HQ and hydroxyacrylate respectively in a one-pot process to obtain the reactive flame retardant.

10. The preparation method according to claim 9, characterized in that, The hydroxy acrylate is selected from one of 2-hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-hydroxypropyl isobutylene acrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, and 3-(acryloyloxy)-2-hydroxypropyl methacrylate.

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