Vanillin-modified nitrogen-phosphorus flame-retardant monomer as well as preparation and application thereof

Abstract

The invention discloses a vanillin-modified nitrogen-phosphorus flame-retardant monomer as well as preparation and application thereof. According to the method, vanillin extracted from lignin is taken as a reaction site, a vanillin compound based on a nitrogen-phosphorus system is synthesized through a one-pot method, and then the vanillin compound is acylated to obtain the flame-retardant monomer with acrylate. In addition, a series of copolymers of flame-retardant monomers and acrylic ester are synthesized, and the glass transition temperature of the synthesized flame-retardant polymer is changed by adjusting the proportion of the flame-retardant monomers and the acrylic ester, so that a series of flame-retardant polymers with different properties are obtained.

Description

Technical Field

[0001] The present invention relates to the field of flame retardant acrylates, and in particular to a vanillin-modified nitrogen-phosphorus flame retardant monomer and a preparation and application thereof. Background Art

[0002] Even today, fires continue to cause immeasurable loss of life and property each year. Faced with this dire situation, all industries are placing strict demands on flame retardant materials. With the advancement of technology and the progress of the times, traditional small-molecule flame retardants can no longer meet the demand for flame-retardant materials, necessitating the urgent need for innovative and efficient flame-retardant methods.

[0003] In recent years, there has been growing concern about carbon emissions and environmental pollution during polymer production. Renewable bio-based materials such as vanillin, phytic acid, cardanol, and furfural are emerging as new options for flame retardant design. These materials offer multiple reactive sites and are renewable. Among these raw materials, vanillin, with its reactive phenolic hydroxyl and aldehyde groups, is a favorite in industrial production and an ideal candidate for the development of multifunctional bio-based flame retardants. Unfortunately, flame retardants prepared entirely from bio-based compounds have limited effectiveness. Therefore, the introduction of highly effective flame-retardant elements is necessary. With increasing environmental and safety awareness, flame retardants are required to produce no substances harmful to the environment or human health during use. Therefore, low-toxicity, safe, and environmentally friendly halogen-free flame retardants are the trend in flame retardant development. Over the past few decades, a variety of halogen-free flame retardants have been studied, including those based on phosphorus, nitrogen, silicon, boron, phosphorus-nitrogen, phosphorus-boron, phosphorus-silicon, aluminum hydroxide, and magnesium hydroxide. Compared to other types of flame retardants, reactive flame retardants containing phosphorus and nitrogen are widely used for flame retardant modification of various materials due to their low smoke, low toxicity, excellent flame retardancy, good dispersibility, and compatibility. Reactive flame retardants offer significant advantages over traditional additive flame retardants for flame retardant modification of polymer materials. Reactive flame retardants introduce flame retardant groups into polymers through chemical reactions and then copolymerize the monomers to form flame-retardant polymers. During the polymerization process, the active flame retardant acts as a comonomer or functional group, chemically bonding with the polymer chain. Copolymerization is a more effective method for flame retardant modification of materials.

[0004] Acrylate polymers are increasingly used in optical coatings due to their excellent water and weather resistance. However, their flammable structure significantly limits their application. Therefore, enhancing the flame retardancy of acrylate polymers is a hot topic worthy of in-depth research. Most flame-retardant modifications to acrylate polymers are achieved by adding halogens or other flame retardants. However, the addition of halogen flame retardants not only pollutes the environment but also affects the optical properties of the material during addition, resulting in low flame retardancy. Further exploration of various acrylate polymers with similar high performance is of great significance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a flame retardant monomer that can undergo copolymerization. The flame retardant monomer can self-polymerize and can also be copolymerized with acrylic ester compounds to prepare polymers with different glass transition temperatures, which can then be used in different scenarios.

[0006] In order to solve the above technical problems, the first aspect of the present invention provides a vanillin-modified nitrogen-phosphorus flame-retardant monomer, wherein the flame-retardant monomer has the following structural formula:

[0007]

[0008] Among them, R1 is R 11 is —H or —CH3;

[0009] R1 is preferably R 11 Is -H or -CH3; R1 is more preferably R2 is R2 is preferably

[0010] R3 is Or -H; R3 is preferably n is an integer ≥1, preferably 1-10, more preferably 2-6.

[0011] The second aspect of the present invention provides a method for preparing the nitrogen-phosphorus flame retardant monomer modified with the vanillin described in the first aspect, which specifically comprises the following steps:

[0012] (1) dissolving a vanillin compound, an amine compound, and a phosphate diester in an organic solvent and heating the mixture to react to obtain a vanillin flame retardant monomer intermediate;

[0013] (2) dissolving the vanillin flame retardant monomer intermediate in an organic solvent, adding an acylating agent to react, and obtaining the vanillin-modified nitrogen-phosphorus flame retardant monomer;

[0014] The structural formula of the vanillin compound is as follows:

[0015]

[0016] Wherein: n is an integer ≥1, preferably 1-10, more preferably 2-6.

[0017] Furthermore, the amine compound in (1) is an aniline compound, more preferably aniline.

[0018] Furthermore, the phosphoric acid diester in (1) is a phosphorous acid diester, more preferably dimethyl phosphite, diethyl phosphite and diphenyl phosphite; most preferably dimethyl phosphite.

[0019] Furthermore, the acylating agent in (2) is an acyl halide compound, preferably acryloyl chloride and / or methacryloyl chloride, more preferably acryloyl chloride.

[0020] Furthermore, the molar ratio of the vanillin compound, the amine compound, and the phosphodiester compound in (1) is (0.5-1):1:(1-1.5); more preferably 1:1:(1.2-1.5).

[0021] Furthermore, in step (2), the organic solvent is selected from one or more of dichloromethane, chloroform, and cyclohexane; more preferably chloroform.

[0022] Furthermore, in step (1), the organic solvent is an alcohol organic compound, preferably ethanol.

[0023] Furthermore, in step (2), the reaction is further heated at a temperature of 20-100° C., preferably 20-80° C., more preferably 80° C.; the heating time is 4-24 h, preferably 12-24 h.

[0024] The third aspect of the present invention provides a flame retardant polymer based on vanillin acrylate, the structural formula of the flame retardant polymer is as follows:

[0025]

[0026] Among them, R 11 is -H or -CH3; R 11 Preferably -H;

[0027] R2 is R2 is preferably

[0028] R3 is Or -H; R3 is preferably n is an integer ≥ 1, preferably 1-10, more preferably 2-6;

[0029] m is an integer ≥ 1, preferably 1-5000, more preferably 100-1000.

[0030] A fourth aspect of the present invention provides a flame-retardant copolymer based on vanillin acrylate, the structural formula of the flame-retardant copolymer is as follows:

[0031]

[0032] Among them, R 11 is -H or -CH3; R 11 Preferably -H;

[0033] R2 is R2 is preferably

[0034] R3 is Or -H; R3 is preferably R4 is R4 is preferably R4 is more preferably n is an integer ≥ 1, preferably 1-10, more preferably 1-6;

[0035] p is an integer ≥ 1, preferably 1-3000, more preferably 100-1000;

[0036] t is an integer ≥ 1, preferably 1-3000, more preferably 100-1000.

[0037] The fifth aspect of the present invention is to provide a method for preparing the polymer described in the third aspect, which specifically comprises the following steps:

[0038] S1. Dissolve the vanillin-modified nitrogen-phosphorus flame-retardant monomer, BTPA, and a photoinitiator in an organic solvent and mix them evenly to obtain a mixed solution; the structural formula of the BTPA is:

[0039] S2. subjecting the mixed solution to a photoinduced polymerization reaction to obtain the polymer.

[0040] Furthermore, the molar ratio of the vanillin-modified nitrogen-phosphorus flame-retardant monomer: BTPA: photoinitiator is (50-300):1:0.05; including but not limited to 50:1:0.05, 100:1:0.05, 150:1:0.05, 200:1:0.05, 250:1:0.05 and 300:1:0.05, etc.

[0041] Furthermore, the wavelength of the light for the photo-induced polymerization reaction in S2 is 450-480 nm, more preferably 450-460 nm, and most preferably 460 nm.

[0042] Furthermore, the illumination time of the photoinduced polymerization reaction in S2 is 1-20 h, more preferably 5-20 h.

[0043] Furthermore, the power of the light for photo-induced polymerization in S2 is 10-30 mW / cm 2 , more preferably 15 mW / cm 2 .

[0044] Furthermore, the photoinitiator is 4CzIPN; the structural formula of the photoinitiator is:

[0045]

[0046] The sixth aspect of the present invention is to provide a method for preparing the copolymer described in the fourth aspect, which specifically comprises the following steps:

[0047] F1. Dissolve the vanillin-modified nitrogen-phosphorus flame retardant monomer, acrylate compound, BTPA and photoinitiator in an organic solvent and mix them evenly to obtain a mixed solution; the structural formula of the BTPA is:

[0048]

[0049] F2. Subjecting the mixed solution to a photoinduced polymerization reaction to obtain the copolymer.

[0050] Furthermore, the molar ratio of the acrylic acid ester compound: vanillin-modified nitrogen-phosphorus flame retardant monomer: BTPA: photoinitiator in F1 is (100-400): (50-250): 1: 0.05; preferably (200-300): (50-250): 1: 0.05; including but not limited to 300:50: 1: 0.05, 300:100: 1: 0.05, 300:150: 1: 0.05, 300:250: 1: 0.05, etc.

[0051] Furthermore, the acrylic acid ester compound in F1 is selected from one or more of isooctyl acrylate, acrylic acid, methyl acrylate, ethyl acrylate and butyl acrylate; preferably one or more of isooctyl acrylate, methyl acrylate and ethyl acrylate; more preferably isooctyl acrylate.

[0052] Furthermore, the wavelength of the light for photo-induced polymerization in F2 is 450-480 nm, more preferably 450-460 nm, and most preferably 460 nm.

[0053] Furthermore, the illumination time for the photoinduced polymerization reaction in F2 is 1-20 h, more preferably 5-20 h.

[0054] Furthermore, the power of the light for photo-induced polymerization in F2 is 10-30 mW / cm2 , more preferably 15 mW / cm 2 .

[0055] Furthermore, the photoinitiator is 4CzIPN; the structural formula of the photoinitiator is:

[0056]

[0057] The seventh aspect of the present invention provides the use of the polymer described in the third aspect in a flame retardant coating.

[0058] The eighth aspect of the present invention provides the use of the copolymer described in the fourth aspect in a flame retardant coating.

[0059] Beneficial effects of the present invention:

[0060] 1. This invention utilizes vanillin, extracted from lignin, as a reactive site to produce a novel nitrogen-phosphorus synergistic bio-based flame retardant monomer. Vanillin, a renewable bioresource extracted from lignin, is safe, environmentally friendly, non-toxic, and highly carbon-forming. By incorporating highly effective nitrogen-phosphorus flame retardant elements and acrylate functional groups into the vanillin structure, a photoinduced polymerization reaction results in the formation of an intrinsically flame-retardant macromolecular flame retardant.

[0061] 2. This invention produces copolymers of the flame-retardant monomer vanillin and isooctyl acrylate. By adjusting the ratio of the two monomers, a series of transparent flame-retardant copolymers with varying glass transition temperatures can be prepared. Furthermore, the molecular weight and molecular weight distribution of the polymers obtained through photoinduced polymerization are controllable, resulting in highly consistent flame retardant properties across the copolymers. Compared to doped flame retardants, these copolymers exhibit superior flame retardancy and show promising application prospects in coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is the NMR image of the NP-synergistic vanillin-based flame retardant monomer (II) prepared in Example 1 of the present invention;

[0063] Figure 2 This is the NMR image of the NP-synergistic vanillin-based flame retardant monomer (IV) prepared in Example 2 of the present invention;

[0064] Figure 3 This is the NMR image of the NP-synergistic vanillin-based flame retardant monomer (VI) prepared in Example 3 of the present invention;

[0065] Figure 4 7 is a graph showing the change in heat release rate of copolymer 2, copolymer 4 and P(2-EHA) as a function of temperature in Example 7 of the present invention;

[0066] Figure 53 is a graph showing the change in total heat release rate of copolymer 2, copolymer 4 and P(2-EHA) as a function of temperature in Example 7 of the present invention. DETAILED DESCRIPTION

[0067] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0068] In the following examples and comparative examples of the present invention, the monomer isooctyl acrylate was passed through a neutral alumina column to remove the polymerization inhibitor before use. All other reagents were obtained from commercial sources and used directly. The testing instruments and methods used in the following examples and comparative examples of the present invention are as follows:

[0069] 1. NMR spectra: Bruker 300 MHz NMR spectrometer, CDCl3 as the deuterated reagent and tetramethylsilane (TMS) as the internal standard.

[0070] 2. Monomer conversion: The monomer conversion was determined by measuring the 1H NMR spectrum of the polymerization stock solution using Bruker 300 MHz nuclear magnetic resonance (NMR) at room temperature using CDCl 3 as the solvent.

[0071] 3. Number average molecular weight (Mn, GPC) and molecular weight distribution (Mw / Mn) of the polymer: determined by TOSOH-HLC-8320 or TOSOH-HLC-8420 gel permeation chromatograph (GPC) equipped with a refractive index detector, using a TSK gel SuperAWM-H column (4.6 mm ID × 15 cm × 2), which can measure molecular weights in the range of 103 to 10 × 105 g mol -1 The test temperature was 40 °C, THF was used as the eluent, and the flow rate was 0.35 mL min -1 The samples were injected into the test chamber using a TOSOH automatic sampler. During data analysis, the THF phase was calibrated using a PMMA standard sample.

[0072] 4. Microcalorimeter (MCC): Model 0001 from FTT, UK. The test obtains the heat release rate, peak heat release rate, total heat release, and temperature corresponding to the maximum heat release rate.

[0073] Example 1

[0074] This embodiment relates to the preparation of a vanillin-modified nitrogen-phosphorus flame-retardant monomer, and the reaction equation is as follows:

[0075]

[0076] The specific preparation steps are as follows:

[0077] 1. Vanillin (8.0 g, 0.05 mol), aniline (4.7 g, 0.05 mol), and dimethyl phosphite (9.5 g, 0.075 mol) were weighed into a 100 ml eggplant flask. 10 ml of anhydrous ethanol was added as the solvent and the mixture was reacted at 80°C for 4 h. After the reaction, the mixture was settled with petroleum ether, washed three times with ether, and filtered and dried to obtain a light green solid (I) (14.0 g, 80.0% yield).

[0078] 2. Weigh product (I) (13.2 g, 0.04 mol) into a 250 ml three-necked flask, add 200 ml of dichloromethane as solvent to dissolve, and then add triethylamine (6.1 g, 0.06 mol) to obtain a mixed solution. To the above mixed solution, add a mixed solution of acryloyl chloride (4.4 g, 0.048 mol) and 20 mL of dichloromethane dropwise, and stir at room temperature overnight. After the reaction is completed, filter the insoluble salts, extract the filtrate with water, saturated NaCl solution, and saturated NaHCO3 solution in sequence, and dry the organic layer with anhydrous NaSO4 overnight. Then, remove the anhydrous NaSO4 by suction filtration, and evaporate the filtrate to remove the dichloromethane solvent. Use an intelligent rapid liquid phase preparative chromatography system to separate and obtain product (II) (11.0 g, yield 70.1%).

[0079] like Figure 1 Shown is the NMR image of the prepared flame retardant monomer II, and the results show that the vanillin-modified acrylate flame retardant monomer was prepared.

[0080] Example 2

[0081] This embodiment relates to the preparation of a vanillin-modified nitrogen-phosphorus flame-retardant monomer, and the reaction equation is as follows:

[0082]

[0083] The specific preparation steps are as follows:

[0084] 1. Vanillin (3.1 g, 0.02 mol) and 1,2-ethylene glycol carbonate (3.6 g, 0.04 mol) were weighed and dissolved with stirring at 80°C. The catalyst, tetrabutylammonium iodide (1.5 g, 0.004 mol), was added and the mixture was allowed to react at 110°C for 12 h. After completion of the reaction, the reaction solution was diluted with water and extracted with ethyl acetate. The organic layer was dried over anhydrous sodium sulfate overnight, filtered to remove the anhydrous sodium sulfate, and the filtrate was rotary evaporated to remove the ethyl acetate. The product, 4-(2-hydroxyethoxy)-3-methoxybenzaldehyde (7.3 g, 93.6% yield), was isolated using an intelligent fast preparative liquid chromatography system.

[0085] 2. Weigh 4-(2-hydroxyethoxy)-3-methoxybenzaldehyde (4.0 g, 0.02 mol), aniline (2.0 g, 0.02 mol), and dimethyl phosphite (3.0 g, 0.024 mol), add 20 ml of anhydrous ethanol, and react at 80°C for 24 h. After the reaction, settle with petroleum ether, wash the solid three times with ether, filter, and dry to obtain a light green solid (III) (4.2 g, 55.6% yield).

[0086] 3. Weigh product (III) (4.0 g, 0.01 mol) into a 100 ml three-necked flask, add 40 ml of dichloromethane as solvent for dissolution, and add triethylamine (1.5 g, 0.015 mol). Add a mixed solution of acryloyl chloride (1.1 g, 0.012 mol) and 20 mL of dichloromethane dropwise, and stir at room temperature overnight. After the reaction is completed, filter out the insoluble salts, extract the filtrate with water, saturated NaCl solution, and saturated NaHCO3 solution in sequence, and dry the organic layer over anhydrous NaSO4 overnight. Then, remove the anhydrous NaSO4 by suction filtration, and evaporate the filtrate to remove the dichloromethane solvent. Use an intelligent rapid liquid phase preparative chromatography system to separate and obtain product (VI) (2.0 g, 45.4% yield).

[0087] like Figure 2 Shown is the NMR image of the prepared flame retardant monomer IV, and the results show that the vanillin-modified acrylate flame retardant monomer was prepared.

[0088] Example 3

[0089] This embodiment relates to the preparation of a vanillin-modified nitrogen-phosphorus flame-retardant monomer, and the reaction equation is as follows:

[0090]

[0091] 1. Vanillin (10.0 g, 0.07 mol) and 6-bromo-1-hexanol (15.5 g, 0.08 mol) were weighed into a 500 ml three-necked flask. 100 ml of acetonitrile was added as the solvent. K₂CO₃ (12.4 g, 0.09 mol) was added to provide an alkaline environment. The mixture was reacted at 80°C for 24 h. After the reaction, the K₂CO₃ was filtered off, and the filtrate was rotary evaporated to remove the acetonitrile to obtain a crude product. The crude product was dissolved in methanol and precipitated in ice water to obtain a white solid (15.4 g, 92.7% yield).

[0092] 2. The product from the previous step (12.7 g, 0.05 mol), aniline (5.0 g, 0.05 mol), and dimethyl phosphite (7.5 g, 0.06 mol) were weighed, added to 10 ml of anhydrous ethanol, and reacted at 80°C for 24 h. After the reaction, the mixture was settled with petroleum ether and separated using an intelligent fast preparative liquid chromatography system to obtain product (V) (5.3 g, 24.1% yield).

[0093] 3. Weigh product (V) (5.3 g, 0.012 mol) into a 100 ml three-necked flask, add 40 ml of dichloromethane as solvent for dissolution, and add triethylamine (1.8 g, 0.018 mol). Add a mixed solution of acryloyl chloride (1.4 g, 0.0144 mol) and 20 mL of dichloromethane dropwise, and stir at room temperature overnight. After the reaction is completed, filter the insoluble salts, extract the filtrate with water, saturated NaCl solution, and saturated NaHCO3 solution in sequence, and dry the organic layer with anhydrous NaSO4 overnight. Then, remove the anhydrous NaSO4 by suction filtration, and evaporate the filtrate to remove the dichloromethane solvent. Use an intelligent rapid liquid phase preparative chromatography system to separate and obtain product (VI) (2.1 g, 33.9% yield).

[0094] like Figure 3 Shown is the NMR image of the prepared flame retardant monomer VII, and the results show that the vanillin-modified acrylate flame retardant monomer was prepared.

[0095] Example 4

[0096] This example relates to the preparation of a flame-retardant polymer of vanillin-based acrylate, using the vanillin-modified nitrogen-phosphorus flame-retardant monomer II prepared in Example 1 as the flame-retardant monomer. The specific steps are as follows:

[0097] (1) Flame retardant monomer II, BTPA and 4CzIPN were dissolved in DMF solvent to form a mixed solution; wherein the molar ratios of flame retardant monomer II:BTPA:4CzIPN were 50:1:0.05, 100:1:0.05, 150:1:0.05, 200:1:0.05, 250:1:0.05 and 300:1:0.05, respectively.

[0098] (2) Add the mixed solution to a 2 mL ampoule and place a magnet. Place the ampoule in liquid nitrogen to freeze the solution, then evacuate for 30 to 60 seconds, then thaw and dissolve it at room temperature while introducing argon protective gas, then freeze, evacuate, thaw, and inflate it again, performing three cycles in sequence to remove all oxygen from the ampoule. After deoxygenation, quickly move the ampoule to the nozzle of the spray gun for flame sealing. Transfer the sealed ampoule to a container equipped with a magnetic stirrer, an electric fan, and a blue LED light (λmax = 460 nm, 15 mW cm -2 ) to conduct photoinduced polymerization. After 5 hours of reaction, the ampoule was transferred to a dark location and the tube was broken. 20 μL of the system mixture was measured with a pipette for 1H NMR analysis to calculate the monomer conversion. An appropriate amount of THF was then added to the remaining polymerization system to dissolve the resulting polymer. The mixture was then poured into petroleum ether to precipitate the polymer. Finally, the purified polymer was dried in a vacuum oven at 30°C until constant weight was achieved.

[0099] Table 1

[0100]

[0101] Table 1 shows the polymerization results of mixed solutions with different ratios under blue light. Wherein, R represents the molar ratio, a represents the conversion rate calculated by nuclear magnetic hydrogen spectrum, b M n,GPC Indicates molecular weight, Represents molecular weight distribution.

[0102] Example 5

[0103] This example relates to the preparation of a flame-retardant copolymer of vanillin-based acrylates. In this example, 2-(butylmercaptosulfonyl) propionic acid (BTPA) is used as a chain transfer agent, and the carbazolyl dicyanophenyl fluorescein 4CzIPN is used as an initiator. Flame-retardant monomer II is reacted with methyl acrylate (MA), ethyl acrylate (BA), or isooctyl acrylate (2-EHA) under blue light to initiate a RAFT polymerization reaction. This allows the copolymer to be screened for a lower glass transition temperature suitable for coating applications.

[0104] Taking the molar ratio of isooctyl acrylate: flame retardant monomer II: BTPA: 4CzIPN = 300:50:1:0.05 as an example, the specific preparation method is as follows:

[0105] Isooctyl acrylate (0.2 g, 1.2 mmol), flame retardant monomer (0.08 g, 0.2 mmol), BTPA (0.1 mg, 0.004 mmol), and 4CzIPN (160 μL, 0.0002 mmol, 4CzIPN dissolved in DMF organic solvent) were added to a clean 2 mL ampoule and a clean magnetic stirrer was added. The ampoule was placed in liquid nitrogen to freeze the solution, then evacuated for 30 to 60 seconds. Subsequently, argon protective gas was introduced while thawing and dissolving at room temperature. The ampoule was then frozen, evacuated, thawed, and aerated three times in sequence to remove all oxygen from the ampoule. After deoxygenation, the ampoule was quickly moved to the nozzle of the spray gun for flame sealing. The sealed ampoule was transferred to a flask equipped with a magnetic stirrer, an electric fan, and a blue LED light (λmax = 460 nm, 15 mW cm -2 ) for photoinduced polymerization. After 10 hours of reaction, the ampoule was transferred to a dark location and the tube was broken. An appropriate amount of THF was added to the polymerization system to dissolve the resulting polymer. The mixture was then poured into petroleum ether to precipitate the polymer. Finally, the purified polymer was dried in a vacuum oven at 30°C until constant weight was achieved.

[0106] As shown in Table 2, R represents the molar ratio of acrylate monomer: flame retardant monomer II: BTPA: 4CzIPN. At the same molar ratio, the copolymer synthesized with isooctyl acrylate has a lower glass transition temperature. Therefore, isooctyl acrylate was selected in the following examples to study the preparation of polymers with low glass transition temperatures.

[0107] Table 2

[0108]

[0109] Example 6

[0110] This example relates to the preparation of a flame-retardant copolymer of a vanillin-based acrylate. In this example, 2-(butylmercaptosulfonyl) propionic acid (BTPA) is used as a chain transfer agent, carbazolyl dicyanophenyl fluorescein 4CzIPN is used as an initiator, and a blue light-induced RAFT polymerization reaction is performed in DMF to synthesize a flame-retardant acrylate-based copolymer.

[0111] Taking the molar ratio of isooctyl acrylate:flame retardant monomer II:BTPA:4CzIPN=300:50:1:0.05 as an example, the specific preparation method is the same as that in Example 5.

[0112] Table 3

[0113]

[0114]

[0115] Table 3 shows the performance measurement results of copolymers synthesized with different monomer ratios. Wherein, R represents the molar ratio, a represents the conversion rate calculated by H NMR spectrum, b M n,GPC Indicates molecular weight, Represents molecular weight distribution.

[0116] Example 7

[0117] This example involves microcalorimetry (MCC) testing of the flame-retardant acrylate copolymer synthesized in Example 6 and a homopolymer of isooctyl acrylate (P(2-EHA)) to determine the heat release rate, peak heat release rate, total heat released, and temperature corresponding to the maximum heat release rate of the flame-retardant polymer. P(2-EHA) was prepared by bulk polymerization of 2.0 g of isooctyl acrylate and 0.01 g of AIBN at 70°C for 12 hours.

[0118] Table 4

[0119]

[0120] The test results are shown in Table 4. Comparing the heat release rates of acrylic resin and acrylate copolymers containing flame-retardant monomers over time and temperature, the heat release rates of both were lower than those of the unflame-retardant acrylic resin. Both the heat release rate and the total heat release rate decreased with increasing flame-retardant monomer content. When the flame-retardant monomer content in the copolymer reached 53.8 mol%, the heat release rate dropped from 24.9 kJ / g to 17.6 kJ / g, a 29.3% decrease.

[0121] Example 8

[0122] This example involves DSC testing of the flame-retardant acrylate copolymer synthesized in Example 6. All experiments were conducted in a nitrogen atmosphere, with a sample mass of 5-8 mg and a heating and cooling rate of 5 K / min. The test results are shown in Table 5.

[0123] Table 5

[0124]

[0125] By adjusting the molar ratio of the flame-retardant monomer to isooctyl acrylate, a series of flame-retardant acrylate copolymers with varying Tg values were obtained, all exhibiting flame-retardant properties. Due to the rigid structure of the designed flame-retardant monomer, the Tg of the copolymers gradually increases with increasing flame-retardant monomer content.

[0126] In summary, the present invention has designed and synthesized a new type of nitrogen-phosphorus synergistic vanillin-based flame-retardant monomer, which is introduced into the polymer chain in the form of copolymerization, which can effectively reduce the flammability of acrylic polymers and avoid the changes in material performance and the influence of poor flame retardant effect caused by the addition of flame retardants. A transparent flame-retardant copolymer coating was prepared by photo-RAFT polymerization. A series of flame-retardant acrylic polymers with different glass transition temperatures, controllable molecular weights and narrow distributions were obtained. Compared with traditional free radical initiation, the polymerization speed is fast and the distribution of the synthesized polymer chain is narrow. The obtained polymer can not only obtain a specific molecular weight, but also achieve performance changes by adjusting the polymerization ratio.

[0127] The above embodiments are merely preferred embodiments for the purpose of fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

Claims

1. A vanillin-modified nitrogen-phosphorus flame retardant monomer, characterized in that: It has the following structural formula: Among them, R1 is R 11 is —H or —CH3; R2 is R3 is or—H; n is an integer ≥1.

2. A method for preparing the vanillin-modified nitrogen-phosphorus flame-retardant monomer according to claim 1, characterized in that: The following steps are involved: (1) dissolving a vanillin compound, an amine compound, and a phosphate diester in an organic solvent and heating the mixture to react to obtain a vanillin flame retardant monomer intermediate; (2) dissolving the vanillin flame retardant monomer intermediate in an organic solvent, adding an acylating agent to react, and obtaining the vanillin-modified nitrogen-phosphorus flame retardant monomer; The structural formula of the vanillin compound is as follows: Here, n is an integer ≥1.

3. The preparation method according to claim 2, wherein The molar ratio of the vanillin compound, the amine compound and the phosphodiester compound is (0.5-1):1:(1-1.5).

4. A flame retardant polymer based on vanillin acrylate, characterized in that: The structural formula of the flame retardant polymer is as follows: Among them, R 11 is -H or -CH3; R2 is R3 is or—H; n is an integer ≥1, and m is an integer ≥1.

5. A flame retardant copolymer based on vanillin acrylate, characterized in that: The structural formula of the flame retardant copolymer is as follows: Among them, R 11 is -H or -CH3; R2 is R3 is or -H; R4 is n is an integer ≥1, p is an integer ≥1, and t is an integer ≥1.

6. A method for preparing a flame-retardant polymer of vanillin acrylate according to claim 4, characterized in that The following steps are involved: S1. Dissolving a vanillin-modified nitrogen-phosphorus flame retardant monomer, BTPA, and a photoinitiator in an organic solvent and mixing them uniformly to obtain a mixed solution; wherein the molar ratio of the vanillin-modified nitrogen-phosphorus flame retardant monomer: BTPA: photoinitiator is (50-300):1:0.05; The structural formula of the BTPA is: S2. subjecting the mixed solution to a photoinduced polymerization reaction to obtain the polymer.

7. A method for preparing the flame-retardant copolymer of vanillin acrylate according to claim 5, characterized in that The following steps are involved: F1, dissolving the vanillin-modified nitrogen-phosphorus flame retardant monomer, the acrylate compound, BTPA and the photoinitiator in an organic solvent and mixing them uniformly to obtain a mixed solution; The structural formula of the BTPA is: F2. Subjecting the mixed solution to a photoinduced polymerization reaction to obtain the copolymer.

8. The preparation method according to claim 7, wherein The molar ratio of the acrylic acid ester compound: the vanillin-modified nitrogen-phosphorus flame-retardant monomer: BTPA: the photoinitiator is (100-400): (50-250): 1: 0.

05.

9. Use of the flame retardant polymer according to claim 4 in flame retardant coatings.

10. Use of the flame retardant copolymer according to claim 5 in flame retardant coatings.

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