Lignin-based reactive flame retardant, preparation method and application of lignin-based reactive flame retardant in flame-retardant styrene resin

Abstract

The invention provides a lignin-based reactive flame retardant, a preparation method and application of the lignin-based reactive flame retardant in flame-retardant styrene resin, and belongs to the technical field of flame-retardant polystyrene. The preparation method comprises the following steps: firstly, by taking renewable resources as raw materials, quantitatively converting a lignin phenolic compound into a lignin vinyl phenol monomer through decarboxylation, then carrying out phosphorylation reaction on the lignin vinyl phenol monomer and a phosphoryl chloride monomer to synthesize a lignin-based reactive flame retardant containing a vinyl benzene structure, and applying the lignin-based reactive flame retardant to preparation of lignin-based intrinsic flame-retardant styrene resin. The flame retardant has excellent biocompatibility, stable flame-retardant effect and environmental friendliness, the flame-retardant mechanism of the flame retardant is derived from phosphate groups introduced into molecules, and the dual flame-retardant mechanism is realized in a condensed phase and a gas phase; the flame retardant has modular characteristics, can be used for flexible design and structural regulation of flame-retardant molecules, and has reliable application value in the field of flame-retardant modified styrene materials; the problem of base performance degradation caused by a traditional flame retardant can be effectively avoided under the condition that the basic performance of the material is kept.

Description

Technical Field

[0001] This invention belongs to the field of flame-retardant polystyrene technology, and relates to a class of lignin-based reactive flame retardants, their preparation methods, and their applications in flame-retardant styrene resins. Background Technology

[0002] Polystyrene (PS) is one of the world's five most widely used general-purpose plastics, with applications covering key sectors of the national economy such as food packaging, building materials, electronic devices, and medical equipment. However, because the molecular chain structure of styrene resins is mainly composed of C and H elements, its limiting oxygen index is only 18%. The material is highly flammable under external heat or fire sources, and releases large amounts of toxic and harmful gases during combustion, posing a serious threat to human life and environmental protection.

[0003] Improving the flame retardant properties of styrene-based resins is mainly achieved by blending halogenated flame retardants with styrene-based resins or by introducing flame-retardant groups onto the polystyrene macromolecular chain through chemical reactions. However, these halogenated flame retardants have been banned or phased out due to their potential for persistent environmental pollution, bioaccumulation, recalcitrant degradation, and biotoxicity. Driven by increasingly stringent global environmental policies, halogen-free flame retardants have become the mainstream of industry development, with environmentally friendly biomass flame retardants derived from renewable resources being a current research hotspot and an important future development direction.

[0004] Lignin, a high-value-added material derived from renewable biomass resources in nature, has been extensively studied. The various phenolic derivatives obtained through depolymerization exhibit structural characteristics highly similar to petroleum-based styrene. Its high chemical reactivity and ease of derivatization with phenolic hydroxyl groups make it an ideal site for functional modification, endowing polymers with multiple properties to meet application requirements. Furthermore, it can effectively reduce petroleum resource consumption and mitigate environmental pollution. In recent years, lignin's unique aromatic structure and high charring ability have demonstrated significant flame-retardant potential in polymer material applications.

[0005] Chinese invention patent CN202111452437.5 discloses a halogen-free, high-gloss, flame-retardant polystyrene material, its preparation method, and its applications. The disclosed polymerization formulation containing phosphorus- and nitrogen-based synergistic flame retardants exhibits good flame retardancy, gloss, and toughness. However, this flame-retardant system is introduced only through physical blending, and its poor compatibility significantly limits its durability. Chinese invention patent CN202411968075.9 discloses a method for preparing an inherently flame-retardant and toughened polystyrene copolymer. It discloses a four-step modification of a bio-based compound, cashew nut shell powder, with integrated phosphorus and nitrogen, resulting in a highly flexible flame-retardant monomer that reacts with styrene to obtain an inherently flame-retardant and toughened polystyrene copolymer, exhibiting good flame retardancy and impact resistance. However, this synthesis method is cumbersome and complex. Chinese invention patent CN201811518143.6 discloses a flame retardant for ABS plastic, flame-retardant ABS plastic, and a method for preparing the same. The disclosed phosphorus-nitrogen synergistic flame retardant containing modified lignin exhibits good flame retardancy and impact resistance in ABS plastic samples. However, this flame retardant system is introduced only through physical blending, and its poor compatibility significantly limits its durability.

[0006] In order to meet the urgent needs of green sustainable development and industrialized production, it is necessary to develop reactive flame retardants with simpler synthesis strategies, halogen-free environmentally friendly properties and high flame retardant performance, so as to continuously promote the innovation and application level of styrene resin flame retardant technology. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a class of lignin-based reactive flame retardants, their preparation method, and their application in flame-retardant styrene-based resins. This class of lignin-based reactive flame retardants is synthesized from lignin phenolic compounds through a simple two-step process. It possesses a structure and polymerization characteristics highly similar to petroleum-based styrene, and can meet the requirements for long-term stability.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides a class of lignin-based reactive flame retardants, the general structural formula of which is:

[0010]

[0011] R1 is selected from H and OMe. R2 is selected from H, OMe, and OH. R3 is a highly reactive phosphoryl chloride functional monomer selected from any one of the structures shown in Formulas 1 to 25.

[0012]

[0013] Secondly, this invention provides a method for preparing a class of lignin-based reactive flame retardants. First, lignin phenolic compounds are quantitatively converted into lignin vinylphenol monomers through decarboxylation, and then phosphorylated with phosphoryl chloride monomers to synthesize the lignin-based reactive flame retardant containing a vinylphenol structure. The method includes the following steps:

[0014] Step S1: Add lignin phenolic compounds, the first organic solvent and the acid-binding agent to the reaction apparatus, reflux at 80~150°C for 6~12 h, extract by organic phase extraction and rotary evaporation, and purify by column chromatography to obtain lignin vinylphenol monomers with a structure similar to petroleum-based styrene.

[0015] Step S2: The lignin-derived vinylphenol monomer prepared in step S1, the second organic solvent, and the acid-binding agent are slowly added dropwise with phosphoryl chloride monomer at -10 to 10°C for 1 to 3 hours. Then, the temperature is raised to 50 to 80°C and the reaction continues for 12 to 24 hours. The product is purified by organic phase extraction, rotary evaporation, and column chromatography to obtain the lignin-based reactive flame retardant.

[0016] Furthermore, the lignin phenolic compound mentioned in step S1 is any one of coumaric acid, ferulic acid, caffeic acid, and sinapic acid.

[0017] Further, the first organic solvent mentioned in step S1 is at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile, and 1,4-dioxane, preferably N,N-dimethylformamide or N-methylpyrrolidone.

[0018] Further, the acid-binding agent in step S1 is selected from at least one of triethylamine and pyridine. The acid-binding agent in step S2 is selected from at least one of triethylamine and pyridine.

[0019] Furthermore, the reaction apparatus described in step S1 is in a high-purity nitrogen or high-purity argon atmosphere. The reaction apparatus described in step S2 is in a high-purity nitrogen or high-purity argon atmosphere.

[0020] Further, the molar ratio of the lignin phenolic compound, the first organic solvent, and the acid-binding agent in step S1 is 1:(3~5):(1.8~2.2).

[0021] Further, the second organic solvent mentioned in step S2 is at least one of acetone, dichloromethane, chloroform, tetrahydrofuran, acetonitrile, methyl tert-butyl ether, and 1,4-dioxane, preferably acetone or tetrahydrofuran.

[0022] Furthermore, the phosphoryl chloride monomer mentioned in step S2 is any one of the structures shown in Formula 1 to Formula 25.

[0023]

[0024] Further, the molar ratio of the phenolic monomer, the second organic solvent, the acid-binding agent, and the phosphoryl chloride monomer in step S2 is 1:(3~5):(1.8-2.2):(1.2-2.0).

[0025] Thirdly, this invention provides the application of a class of lignin-based reactive flame retardants containing vinylbenzene structures, which are used to prepare lignin-based flame-retardant styrene resins, wherein the structural formula of the lignin-based flame-retardant styrene resin is:

[0026]

[0027] Wherein, m>0, n>0, and m+n=100. R1 is selected from H and OMe. R2 is selected from H, OMe, and OH. R3 is a highly reactive phosphoryl chloride functional monomer, selected from any one of the structures shown in Formulas 1 to 25, specifically as follows:

[0028]

[0029] Fourthly, the present invention provides a method for preparing a type of lignin-based flame-retardant polystyrene resin, comprising the following steps:

[0030] Step S1: Add lignin-based reactive flame retardant, styrene, a small amount of solvent and free radical initiator to the reaction apparatus, polymerize at 90 ~ 150 °C for 5 ~ 10 h, stirring at 150 ~ 300 rpm, and dissolve the product in the first organic solution to obtain a high concentration product solution.

[0031] Step S2: The high-concentration product solution obtained in S1 is dispersed in a large amount of second organic solution and allowed to settle, initially precipitating the polymer.

[0032] Step S3: Repeat the above "dissolve-sedimentation" steps multiple times for further purification. The final product is collected by vacuum filtration and dried under high vacuum to obtain the lignin-based flame-retardant polystyrene resin.

[0033] Furthermore, the small amount of solvent in step S1 is either toluene or ethylbenzene.

[0034] Further, in step S1, the free radical initiator is any one of benzoyl peroxide, di-o-methylbenzoyl peroxide, acetyl isobutyryl peroxide, di-tert-butyl peroxide, 1,1-di(tert-butylperoxide)cyclohexane, and azobisisobutyronitrile.

[0035] Further, in step S1, the lignin-based reactive flame retardant and styrene constitute a styrene phase, and are fed in a molar ratio, wherein the lignin-based reactive flame retardant is 10-50 parts and the styrene is 50-90 parts. The mass ratio of the styrene phase, a small amount of solvent, and free radical initiator is 100:(10-30):(0.01-0.4).

[0036] Furthermore, in step S1, the reaction apparatus is in a high-purity nitrogen or high-purity argon atmosphere.

[0037] Further, in step S1, the first organic solution is at least one of dichloromethane, chloroform, and tetrahydrofuran. Specifically, each 50 mL of the first organic solution contains 30-50 g of the lignin-based flame-retardant polystyrene resin to be purified.

[0038] Further, in step S2, the second organic solution is at least one of methanol and ethanol. Specifically, 20-50 mL of a high-concentration product solution is added to every 500 mL of the second organic solution.

[0039] Furthermore, in step S2, the vacuum drying temperature is 40 ~ 80 °C, and the drying time is 12 ~ 48 h.

[0040] The beneficial effects of this invention are as follows:

[0041] (1) The reactive flame retardant provided by the present invention uses lignin derivatives, which are renewable resources, as raw materials. It belongs to the category of bio-based flame retardants. The synthesis process is simple and the toxicity is low. It can significantly reduce dependence on petroleum resources and reduce pollution to the environment.

[0042] (2) The lignin-based reactive flame retardant provided by the present invention is a copolymerizable monomer that can impart inherent flame retardancy to the material through chemical bonding, thereby achieving a highly efficient, stable and halogen-free environmentally friendly flame retardant effect.

[0043] (3) The lignin-based reactive flame retardant provided by the present invention has a structural feature that is highly similar to that of traditional petroleum-based styrene. Compared with conventional additive flame retardants, it has better biocompatibility and can ensure that the material meets the long-term stability requirements.

[0044] (4) The lignin-based reactive flame retardant provided by this invention has a flame retardant effect mainly due to the phosphate ester group introduced into the molecule. This group can exert a flame retardant effect through a dual mechanism of condensed phase and gas phase. Phosphorus-based flame retardants have the characteristics of high flame retardancy, low toxicity, environmental friendliness and low smoke generation, and are widely regarded as one of the most promising alternatives to halogen flame retardants.

[0045] (5) The lignin-based reactive flame retardant provided by this invention has a modular preparation strategy, which allows for flexible design and control of the flame retardant molecular structure according to actual application requirements. The synthesis method is simple, the conditions are mild, and it is easy to scale up and achieve large-scale industrial preparation, showing good industrialization potential and practical application value.

[0046] (6) The lignin-based reactive flame retardant provided by this invention has reliable application value in the field of flame-retardant styrene-based materials. While maintaining the mechanical and processing properties of the material to the greatest extent, it endows the material with higher heat resistance and stable flame retardancy, effectively avoiding the problem of matrix property degradation caused by traditional flame retardants. Attached Figure Description

[0047] Figure 1 The reactive flame retardant with a ferulic acid group containing a diphenyl phosphate structure in Example 2 1 H NMR;

[0048] Figure 2 The reactive flame retardant with a ferulic acid group containing a diphenyl phosphite structure in Example 6 1 H NMR;

[0049] Figure 3 The ferulic acid-based flame-retardant polystyrene resin (containing diphenyl phosphate) in Example 26 1 H NMR;

[0050] Figure 4 The ferulic acid-based flame-retardant polystyrene resin (containing diphenyl phosphate) in Example 26 31 P NMR;

[0051] Figure 5 For the ferulic acid-based flame-retardant polystyrene resin (containing diphenyl phosphite) in Example 29 1 HNMR;

[0052] Figure 6 For the ferulic acid-based flame-retardant polystyrene resin (containing diphenyl phosphite) in Example 29 31 PNMR. Detailed Implementation

[0053] To more clearly illustrate the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below. It should be noted that, without conflict, the embodiments of the present invention and the features thereof can be combined with each other.

[0054] Test instrument models: The nuclear magnetic resonance spectrometer used was a Bruker AVANCE Ⅲ 500 MHz (Bruker, Switzerland), the critical oxygen index analyzer used was a PX-1005F instrument (Phoenix, China), and the differential scanning calorimeter used was a TA DSC25 model (TA, USA).

[0055] The synthetic routes for the lignin-based reactive flame retardants in Examples 1-25 are as follows:

[0056]

[0057] In the synthetic routes, a is the p-coumaric acid group synthetic route, b is the ferulic acid group synthetic route, c is the caffeic acid group synthetic route, and d is the sinapic acid group reactive flame retardant synthetic route.

[0058] Example 1 (Preparation of coumaric acid-based reactive flame retardant monomers: containing dimethylphosphonate structures):

[0059] Synthesis of p-coumaric acid-based vinylphenol monomer: The lignin phenolic compound p-coumaric acid (1 eq, 10 g) was dissolved in an organic solvent (N,N-dimethylformamide, 3 eq, 13.36 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 10.60 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic solution (methyl tert-butyl ether, 500 ml) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL), and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic solvent, yielding the target product, p-coumaric acid-based vinylphenol monomer.

[0060] Synthesis of p-coumaric acid-based reactive flame retardants: p-coumaric acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (acetone, 3 eq, 14.50 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 14.48 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (dimethylphosphonic chloride, 2.0 eq, 18.72 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a coumaric acid-reactive flame retardant.

[0061] Example 2 (Preparation of ferulic acid-based reactive flame retardant monomers: containing dimethyl phosphate structure):

[0062] Synthesis of ferulic acid-based vinylphenol monomer: Ferulic acid (1 eq, 10 g), a lignin phenolic compound, was dissolved in an organic solvent (dimethyl sulfoxide, 4 eq, 16.09 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.0 eq, 10.42 g) was added. The mixture was refluxed at 115 °C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based vinylphenol monomer.

[0063] Synthesis of Ferulic Acid-Based Reactive Flame Retardant: Ferulic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (dichloromethane, 4 eq, 22.62 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.0 eq, 13.48 g) was added. After cooling the reaction system to 0 °C, phosphoryl chloride monomer (dimethylphosphoryl chloride, 1.6 eq, 15.39 g) was slowly added dropwise under stirring and reacted for 2 h. The temperature was then raised to 65 °C and the reaction was continued for 18 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based reactive flame retardant.

[0064] Example 3 (Preparation of caffeic acid-based reactive flame retardant monomers: containing methyl phosphate structure):

[0065] Synthesis of caffeoylvinylphenol monomer: Caffeic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (N-methylpyrrolidone, 5 eq, 27.51 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 1.8 eq, 7.90 g) was added. The mixture was refluxed at 150 °C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, caffeoylvinylphenol monomer.

[0066] Synthesis of Caffeic Acid-Based Reactive Flame Retardant: Caffeic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (chloroform, 5 eq, 43.84 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 1.8 eq, 10.46 g) was added. After cooling the reaction system to 10 °C, phosphoric acid chloride monomer (methylphosphoric acid, 1.2 eq, 15.39 g) was slowly added dropwise under stirring and reacted for 1 h. The temperature was then raised to 80 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added and washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic solvent, yielding the target product, caffeic acid-based reactive flame retardant.

[0067] Example 4 (Preparation of sinapic acid-based reactive flame retardant monomers: containing dicyclopentylphosphonate structure):

[0068] Synthesis of sinapicoylvinylphenol monomer: Sinapicoic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (acetonitrile, 3 eq, 5.49 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.2 eq, 9.93 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, sinapicoylvinylphenol monomer.

[0069] Synthesis of sinapic acid-based reactive flame retardants: Sinapic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (tetrahydrofuran, 3 eq, 12.00 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.2 eq, 12.35 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (dicyclopentylphosphine chloride, 2.0 eq, 24.49 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based reactive flame retardant.

[0070] Example 5 (Preparation of a coumaric acid-based reactive flame retardant monomer: containing a 1-[(methyl)phosphate]ethane structure):

[0071] Synthesis of p-coumaric acid-based vinylphenol monomer: The lignin phenolic compound p-coumaric acid (1 eq, 10 g) was dissolved in an organic solvent (1,4-dioxane, 4 eq, 21.47 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 9.64 g) was added. The mixture was refluxed at 115 °C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, p-coumaric acid-based vinylphenol monomer.

[0072] Synthesis of p-coumaric acid-based reactive flame retardants: p-Coumaric acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (acetonitrile, 4 eq, 13.67 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 13.17 g) was added. After cooling the reaction system to 0 °C, phosphoryl chloride monomer (1-[chloro(methyl)phosphoryl]ethane, 1.6 eq, 16.85 g) was slowly added dropwise under stirring and reacted for 2 h. The temperature was then raised to 65 °C and the reaction was continued for 18 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 mL) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a coumaric acid-reactive flame retardant.

[0073] Example 6 (Preparation of ferulic acid-based reactive flame retardant monomers: containing diphenyl phosphate structures):

[0074] Synthesis of ferulic acid-based vinylphenol monomer: Ferulic acid (1 eq, 10 g), a lignin phenolic compound, was dissolved in an organic solvent (N,N-dimethylformamide, 5 eq, 18.82 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 1.8 eq, 9.38 g) was added. The mixture was refluxed at 150 °C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based vinylphenol monomer.

[0075] Synthesis of Ferulic Acid-Based Reactive Flame Retardant: Ferulic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (methyl tert-butyl ether, 5 eq, 29.35 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 1.8 eq, 12.13 g) was added. After cooling the reaction system to 10 °C, phosphoryl chloride monomer (diphenyl chlorophosphate, 1.2 eq, 21.46 g) was slowly added dropwise under stirring and reacted for 1 h. The temperature was then raised to 80 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based reactive flame retardant.

[0076] Example 7 (Preparation of caffeic acid-based reactive flame retardant monomers: containing diisopropyl phosphate structure):

[0077] Synthesis of caffeoylvinylphenol monomer: Caffeic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (dimethyl sulfoxide, 3 eq, 13.01 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 9.66 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, caffeoylvinylphenol monomer.

[0078] Synthesis of caffeic acid-based reactive flame retardants: Caffeic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (1,4-dioxane, 3 eq, 19.41 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 12.78 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (diisopropyl chlorophosphate, 2.0 eq, 29.47 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a caffeic acid-based reactive flame retardant.

[0079] Example 8 (Preparation of sinapic acid-based reactive flame retardant monomers: containing ethyl (phenyl) hypophosphite structures):

[0080] Synthesis of sinapicoylvinylphenol monomer: Sinapicoic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (N-methylpyrrolidone, 4 eq, 17.69 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.0 eq, 9.03 g) was added. The mixture was refluxed at 115 °C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, sinapicoylvinylphenol monomer.

[0081] Synthesis of sinapic acid-based reactive flame retardants: Sinapic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (acetone, 4 eq, 12.89 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.0 eq, 11.23 g) was added. After cooling the reaction system to 0 °C, phosphoryl chloride monomer (ethyl(phenyl)phosphine chloride, 1.6 eq, 16.74 g) was slowly added dropwise under stirring and reacted for 2 h. The temperature was then raised to 65 °C and the reaction was continued for 18 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a sinapic acid-based reactive flame retardant.

[0082] Example 9 (Preparation of coumaric acid-based reactive flame retardant monomers: containing dicyclohexyl phosphate structure):

[0083] Synthesis of p-coumaric acid-based vinylphenol monomer: The lignin phenolic compound p-coumaric acid (1 eq, 10 g) was dissolved in an organic solvent (acetonitrile, 5 eq, 12.50 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 1.8 eq, 8.67 g) was added. The mixture was refluxed at 150 °C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, p-coumaric acid-based vinylphenol monomer.

[0084] Synthesis of p-coumaric acid-based reactive flame retardants: p-Coumaric acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (dichloromethane, 5 eq, 35.34 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 1.8 eq, 11.85 g) was added. After cooling the reaction system to 10 °C, phosphoryl chloride monomer (dicyclohexylphosphoryl chloride, 1.2 eq, 24.84 g) was slowly added dropwise under stirring and reacted for 1 h. The temperature was then raised to 80 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a coumaric acid-reactive flame retardant.

[0085] Example 10 (Preparation of ferulic acid-based reactive flame retardant monomers: containing o-tolyl phosphate structure):

[0086] Synthesis of ferulic acid-based vinylphenol monomer: Ferulic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (1,4-dioxane, 3 eq, 13.61 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.2 eq, 11.46 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based vinylphenol monomer.

[0087] Synthesis of Ferulic Acid-Based Reactive Flame Retardant: Ferulic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (chloroform, 3 eq, 23.85 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.2 eq, 14.82 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (o-tolyl chlorophosphate, 2.0 eq, 39.51 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based reactive flame retardant.

[0088] Example 11 (Preparation of caffeic acid-based reactive flame retardant monomers: containing diethylphosphonate structure):

[0089] Synthesis of caffeoylvinylphenol monomer: Caffeic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (N,N-dimethylformamide, 4 eq, 16.23 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 8.78 g) was added. The mixture was refluxed at 115 °C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, caffeoylvinylphenol monomer.

[0090] Synthesis of caffeic acid-based reactive flame retardants: Caffeic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (tetrahydrofuran, 4 eq, 21.19 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 11.62 g) was added. After cooling the reaction system to 0 °C, phosphoryl chloride monomer (diethylphosphonic chloride, 1.6 eq, 16.52 g) was slowly added dropwise under stirring and reacted for 2 h. The temperature was then raised to 65 °C and the reaction was continued for 18 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a caffeic acid-based reactive flame retardant.

[0091] Example 12 (Preparation of sinapic acid-based reactive flame retardant monomers: containing di-n-propyl phosphate structure):

[0092] Synthesis of sinapicolate-based vinylphenol monomer: Sinapicolate (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (dimethyl sulfoxide, 5 eq, 17.42 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 1.8 eq, 8.12 g) was added. The mixture was refluxed at 150 °C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL), and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, sinapicolate-based vinylphenol monomer.

[0093] Synthesis of sinapic acid-based reactive flame retardants: Sinapic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (acetonitrile, 5 eq, 11.39 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 1.8 eq, 10.11 g) was added. After cooling the reaction system to 10 °C, phosphoryl chloride monomer (di-n-propyl chlorophosphate, 1.2 eq, 13.36 g) was slowly added dropwise under stirring and reacted for 1 h. The temperature was then raised to 80 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a sinapic acid-based reactive flame retardant.

[0094] Example 13 (Preparation of coumaric acid-based reactive flame retardant monomers: containing isopropyl (phenyl) hypophosphite structures):

[0095] Synthesis of p-coumaric acid-based vinylphenol monomer: The lignin phenolic compound p-coumaric acid (1 eq, 10 g) was dissolved in an organic solvent (N-methylpyrrolidone, 3 eq, 18.12 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 10.60 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 ml) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL), and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, p-coumaric acid-based vinylphenol monomer.

[0096] Synthesis of p-coumaric acid-based reactive flame retardants: p-coumaric acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (methyl tert-butyl ether, 3 eq, 22.01 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 14.48 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (isopropyl(phenyl)phosphine chloride, 2.0 eq, 33.73 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a coumaric acid-reactive flame retardant.

[0097] Example 14 (Preparation of ferulic acid-based reactive flame retardant monomers: containing bis(cyclohexylmethyl)phosphonate structures):

[0098] Synthesis of ferulic acid-based vinylphenol monomer: Ferulic acid (1 eq, 10 g), a lignin phenolic compound, was dissolved in an organic solvent (acetonitrile, 4 eq, 8.46 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.0 eq, 10.42 g) was added. The mixture was refluxed at 115 °C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based vinylphenol monomer.

[0099] Synthesis of Ferulic Acid-Based Reactive Flame Retardant: Ferulic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (1,4-dioxane, 4 eq, 23.47 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.0 eq, 13.48 g) was added. After cooling the reaction system to 0 °C, phosphoryl chloride monomer (bis(cyclohexylmethyl)phosphine chloride, 1.6 eq, 29.49 g) was slowly added dropwise under stirring and reacted for 2 h. The temperature was then raised to 65 °C and the reaction was continued for 18 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based reactive flame retardant.

[0100] Example 15 (Preparation of caffeic acid-based reactive flame retardant monomers: containing bis(2,6-dimethylyl)phosphate structure):

[0101] Synthesis of caffeoylvinylphenol monomer: Caffeic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (1,4-dioxane, 5 eq, 24.45 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 7.90 g) was added. The mixture was refluxed at 150 °C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, caffeoylvinylphenol monomer.

[0102] Synthesis of caffeic acid-based reactive flame retardants: Caffeic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (acetone, 5 eq, 21.33 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 10.46 g) was added. After cooling the reaction system to 10 °C, phosphoryl chloride monomer (bis(2,6-xylyl)phosphoryl chloride, 1.2 eq, 28.62 g) was slowly added dropwise under stirring and reacted for 1 h. The temperature was then raised to 80 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a caffeic acid-based reactive flame retardant.

[0103] Example 16 (Preparation of sinapic acid-based reactive flame retardant monomers: containing 2-[(isopropyl)phosphate]propane structure):

[0104] Synthesis of sinapicoylvinylphenol monomer: Sinapicoic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (N,N-dimethylformamide, 3 eq, 9.78 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.2 eq, 9.93 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, sinapicoylvinylphenol monomer.

[0105] Synthesis of sinapic acid-based reactive flame retardants: Sinapic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (dichloromethane, 3 eq, 14.14 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.2 eq, 12.35 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (2-[chloro(isopropyl)phosphoryl]propane, 2.0 eq, 18.71 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a sinapic acid-based reactive flame retardant.

[0106] Example 17 (Preparation of a coumaric acid-based reactive flame retardant monomer containing a 1-((2-methylpropoxy)phosphate)oxy-2-methyl-propane structure):

[0107] Synthesis of p-coumaric acid-based vinylphenol monomer: The lignin phenolic compound p-coumaric acid (1 eq, 10 g) was dissolved in an organic solvent (dimethyl sulfoxide, 4 eq, 19.04 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 9.64 g) was added. The mixture was refluxed at 115 °C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, p-coumaric acid-based vinylphenol monomer.

[0108] Synthesis of p-coumaric acid-based reactive flame retardants: p-coumaric acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (chloroform, 4 eq, 39.74 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 13.17 g) was added. After cooling the reaction system to 0 °C, phosphoryl chloride monomer (1-(chloro-(2-methylpropoxy)phosphoryl)oxy-2-methyl-propane, 1.6 eq, 30.45 g) was slowly added dropwise under stirring and reacted for 2 h. The temperature was then raised to 65 °C and the reaction was continued for 18 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a coumaric acid-reactive flame retardant.

[0109] Example 18 (Preparation of ferulic acid-based reactive flame retardant monomers: containing dimethyl hypophosphite structure):

[0110] Synthesis of ferulic acid-based vinylphenol monomer: Ferulic acid (1 eq, 10 g), a lignin phenolic compound, was dissolved in an organic solvent (N-methylpyrrolidone, 5 eq, 25.52 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 1.8 eq, 9.38 g) was added. The mixture was refluxed at 150 °C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based vinylphenol monomer.

[0111] Synthesis of Ferulic Acid-Based Reactive Flame Retardant: Ferulic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (tetrahydrofuran, 5 eq, 24.01 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 1.8 eq, 12.13 g) was added. After cooling the reaction system to 10 °C, phosphoryl chloride monomer (dimethylphosphine chloride, 1.2 eq, 18.91 g) was slowly added dropwise under stirring and reacted for 1 h. The temperature was then raised to 80 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based reactive flame retardant.

[0112] Example 19 (Preparation of caffeic acid-based reactive flame retardant monomers: containing dibenzyl phosphonate structures):

[0113] Synthesis of caffeoylvinylphenol monomer: Caffeic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (acetonitrile, 3 eq, 6.84 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 9.66 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, caffeoylvinylphenol monomer.

[0114] Synthesis of caffeic acid-based reactive flame retardants: Caffeic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (acetonitrile, 3 eq, 9.05 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 12.78 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (dibenzylphosphine chloride, 2.0 eq, 38.88 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a caffeic acid-based reactive flame retardant.

[0115] Example 20 (Preparation of sinapic acid-based reactive flame retardant monomers: containing bis(4-methylphenyl)phosphate structure):

[0116] Synthesis of sinapicoylvinylphenol monomer: Sinapicoic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (methyl tert-butyl ether, 4 eq, 15.72 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.0 eq, 9.03 g) was added. The mixture was refluxed at 115 °C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, sinapicoylvinylphenol monomer.

[0117] Synthesis of sinapic acid-based reactive flame retardants: Sinapic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (methyl tert-butyl ether, 4 eq, 19.57 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.0 eq, 11.23 g) was added. After cooling the reaction system to 0 °C, phosphoryl chloride monomer (bis(4-methylphenyl)chlorinated phosphate, 1.6 eq, 26.34 g) was slowly added dropwise under stirring and reacted for 2 h. The temperature was then raised to 65 °C and the reaction was continued for 18 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a sinapic acid-based reactive flame retardant.

[0118] Example 21 (Preparation of coumaric acid-based reactive flame retardant monomers: containing 2-(tert-butyl phosphate)-2-methylpropane structure):

[0119] Synthesis of p-coumaric acid-based vinylphenol monomer: The lignin phenolic compound p-coumaric acid (1 eq, 10 g) was dissolved in an organic solvent (N,N-dimethylformamide, 5 eq, 22.26 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 1.8 eq, 8.67 g) was added. The mixture was refluxed at 150 °C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, p-coumaric acid-based vinylphenol monomer.

[0120] Synthesis of p-coumaric acid-based reactive flame retardants: p-coumaric acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (1,4-dioxane, 5 eq, 36.67 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 1.8 eq, 11.85 g) was added. After cooling the reaction system to 10 °C, phosphoryl chloride monomer (2-[tert-butyl(chloro)phosphoryl]-2-methylpropane, 1.2 eq, 19.64 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 80 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a coumaric acid-reactive flame retardant.

[0121] Example 22 (Preparation of ferulic acid-based reactive flame retardant monomers: containing di-n-butyl phosphate structure):

[0122] Synthesis of ferulic acid-based vinylphenol monomer: Ferulic acid (1 eq, 10 g), a lignin phenolic compound, was dissolved in an organic solvent (dimethyl sulfoxide, 3 eq, 12.07 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.2 eq, 11.46 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based vinylphenol monomer.

[0123] Synthesis of Ferulic Acid-Based Reactive Flame Retardant: Ferulic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (acetone, 3 eq, 11.60 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 2.2 eq, 14.82 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (di-n-butyl chlorophosphate, 2.0 eq, 30.45 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, ferulic acid-based reactive flame retardant.

[0124] Example 23 (Preparation of caffeic acid-based reactive flame retardant monomers: containing bis(2-methylphenyl)-phosphinic acid ester structures):

[0125] Synthesis of caffeoylvinylphenol monomer: Caffeic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (N-methylpyrrolidone, 4 eq, 22.01 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 8.78 g) was added. The mixture was refluxed at 115 °C for 9 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, caffeoylvinylphenol monomer.

[0126] Synthesis of caffeic acid-based reactive flame retardants: Caffeic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (dichloromethane, 4 eq, 24.95 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.0 eq, 11.62 g) was added. After cooling the reaction system to 0 °C, phosphoryl chloride monomer (bis(2-methylphenyl)-phosphine hypochlorite, 1.6 eq, 31.11 g) was slowly added dropwise under stirring and reacted for 2 h. The temperature was then raised to 65 °C and the reaction was continued for 18 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a caffeic acid-based reactive flame retardant.

[0127] Example 24 (Preparation of sinapic acid-based reactive flame retardant monomers: containing 1-(butyl hypophosphite)butane structure):

[0128] Synthesis of sinapicoylvinylphenol monomer: Sinapicoic acid (1 eq, 10 g), a lignin-based phenolic compound, was dissolved in an organic solvent (acetonitrile, 5 eq, 9.15 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 1.8 eq, 8.12 g) was added. The mixture was refluxed at 150 °C for 6 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, sinapicoylvinylphenol monomer.

[0129] Synthesis of sinapic acid-based reactive flame retardants: Sinapic acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (chloroform, 5 eq, 33.12 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (triethylamine, 1.8 eq, 10.11 g) was added. After cooling the reaction system to 10 °C, phosphoryl chloride monomer (1-[butyl(chloro)phospho]butane, 2.0 eq, 13.10 g) was slowly added dropwise under stirring and reacted for 1 h. The temperature was then raised to 80 °C and the reaction was continued for 12 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a sinapic acid-based reactive flame retardant.

[0130] Example 25 (Preparation of coumaric acid-based reactive flame retardant monomers: containing dibenzyl phosphate structure):

[0131] Synthesis of p-coumaric acid-based vinylphenol monomer: The lignin phenolic compound p-coumaric acid (1 eq, 10 g) was dissolved in an organic solvent (N,N-dimethylformamide, 3 eq, 13.36 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 10.60 g) was added. The mixture was refluxed at 80 °C for 12 hours. After the reaction was completed, the mixture was cooled to room temperature, transferred to a separatory funnel, and an organic phase solution (methyl tert-butyl ether, 500 mL) was added. The mixture was then extracted three times with dilute hydrochloric acid solution (1 M, 100 mL) and washed once with saturated saline solution (100 mL). The organic phase was dried over anhydrous magnesium sulfate (2 g) with stirring, filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, p-coumaric acid-based vinylphenol monomer.

[0132] Synthesis of p-coumaric acid-based reactive flame retardants: p-Coumaric acid-based vinylphenol monomer (1 eq, 10 g) was dissolved in an organic solvent (tetrahydrofuran, 3 eq, 18.00 g) and stirred until completely dissolved. The resulting solution was transferred to a reaction flask under argon protection, and an acid-binding agent (pyridine, 2.2 eq, 14.48 g) was added. After cooling the reaction system to -10 °C, phosphoryl chloride monomer (dibenzylphosphochloride, 1.6 eq, 49.39 g) was slowly added dropwise under stirring and reacted for 3 h. The temperature was then raised to 50 °C and the reaction was continued for 24 h. After the reaction was completed, the mixture was filtered and concentrated under reduced pressure to remove the organic solvent. Then, an organic solution (chloroform, 500 ml) was added, and the mixture was washed three times successively with dilute hydrochloric acid solution (1 M, 100 mL), saturated sodium bicarbonate aqueous solution (100 mL), and saturated saline solution (100 mL). The organic phase was dried by stirring with anhydrous magnesium sulfate (2 g), filtered, and concentrated under reduced pressure to remove the organic phase solvent, yielding the target product, a coumaric acid-reactive flame retardant.

[0133] Example 26 (Preparation of a flame-retardant polystyrene polymer with ferulic acid as its basic characteristic: containing 10 parts of diphenyl phosphate structure):

[0134] The ferulic acid-based reactive flame retardant (10.00 g), styrene (24.52 g), and ethylbenzene (6.90 g) prepared in Example 6 were mixed and stirred until a homogeneous solution was formed. This solution was transferred to a reaction flask under argon protection. The reaction system was heated to 90°C, and a free radical initiator (1,1-di(tert-butylperoxy)cyclohexane, 0.0035 g) was added. The reaction was continued at this temperature at 150 rpm for 10 h. After the reaction was complete, the product was rapidly dissolved in an organic solvent (dichloromethane, 30 ml), then dispersed in a second organic solvent (ethanol, 500 ml) and precipitated, initially precipitating the polymer. Subsequently, the above "dissolution-precipitation" steps were repeated three times for further purification. The final product was collected by filtration and dried under high vacuum at 40°C for 48 h to obtain the bio-based flame-retardant polystyrene resin.

[0135] Example 27 (Preparation of flame-retardant polystyrene with ferulic acid as the basic characteristic: containing 30 parts of diphenyl phosphate structure):

[0136] The ferulic acid-based reactive flame retardant (10.00 g), styrene (6.36 g), and toluene (3.27 g) prepared in Example 6 were mixed and stirred until a homogeneous solution was formed. This solution was transferred to a reaction flask under argon protection. The reaction system was heated to 120°C, and a free radical initiator (azobisisobutyronitrile, 0.0654 g) was added. The reaction was continued at this temperature and 225 rpm for 7.5 h. After the reaction was complete, the product was rapidly dissolved in an organic solvent (chloroform, 40 ml), then dispersed in a second organic solvent (methanol, 1000 ml) and allowed to settle, initially precipitating the polymer. Subsequently, the above "dissolution-precipitation" steps were repeated three times for further purification. The final product was collected by filtration and dried under high vacuum at 50°C for 30 h to obtain the bio-based flame-retardant polystyrene resin.

[0137] Example 28 (Preparation of flame-retardant polystyrene with ferulic acid basic characteristics: containing 50 parts of diphenyl phosphate structure):

[0138] The ferulic acid-based reactive flame retardant (10.00 g), styrene (2.72 g), and ethylbenzene (7.6 g) prepared in Example 6 were mixed and stirred until a homogeneous solution was formed. This solution was transferred to a reaction flask under argon protection. The reaction system was heated to 150 °C, and a free radical initiator (benzoyl peroxide, 0.0254 g) was added. The reaction was continued at this temperature at 300 rpm for 5 h. After the reaction was complete, the product was rapidly dissolved in an organic solvent (tetrahydrofuran, 50 ml), then dispersed in a second organic solvent (ethanol, 1000 ml) and allowed to precipitate, initially precipitating the polymer. Subsequently, the above "dissolution-precipitation" steps were repeated three times for further purification. The final product was collected by filtration and dried under high vacuum at 60 °C for 12 h to obtain the bio-based flame-retardant polystyrene resin.

[0139] Example 29 (Preparation of flame-retardant polystyrene with ferulic acid basic characteristics: containing 10 parts of diphenyl phosphite structure):

[0140] The ferulic acid-based reactive flame retardant (10.00 g), styrene (26.75 g), and toluene (7.35 g) prepared in Example 18 were mixed and stirred until a homogeneous solution was formed. This solution was transferred to a reaction flask under argon protection. The reaction system was heated to 90°C, and a free radical initiator (di-o-methylbenzoyl peroxide, 0.0017 g) was added. The reaction was continued at this temperature at 150 rpm for 10 h. After the reaction was complete, the product was rapidly dissolved in an organic solvent (dichloromethane, 30 ml), then dispersed in a second organic solvent (methanol, 500 ml), and precipitated to initially precipitate the polymer. Subsequently, the above "dissolution-precipitation" steps were repeated three times for further purification. The final product was collected by vacuum filtration and dried under high vacuum at 40°C for 48 h to obtain the bio-based flame-retardant polystyrene resin.

[0141] Example 30 (Preparation of flame-retardant polystyrene with ferulic acid as the basic characteristic: containing 30 parts of diphenyl phosphite structure):

[0142] The ferulic acid-based reactive flame retardant (10.00 g), styrene (6.94 g), and ethylbenzene (3.39 g) prepared in Example 18 were mixed and stirred until a homogeneous solution was formed. This solution was transferred to a reaction flask under argon protection. The reaction system was heated to 120°C, and a free radical initiator (acetyl isobutyryl peroxide, 0.0017 g) was added. The reaction was continued at this temperature at 225 rpm for 7.5 h. After the reaction was complete, the product was rapidly dissolved in an organic solvent (chloroform, 40 ml), then dispersed in a second organic solvent (ethanol, 500 ml) and precipitated, initially precipitating the polymer. Subsequently, the above "dissolution-precipitation" steps were repeated three times for further purification. The final product was collected by vacuum filtration and dried under high vacuum at 50°C for 30 h to obtain the bio-based flame-retardant polystyrene resin.

[0143] Example 31 (Preparation of flame-retardant polystyrene with ferulic acid as the basic characteristic: containing 50 parts of diphenyl phosphite structure):

[0144] The ferulic acid-based reactive flame retardant (10.00 g), styrene (2.97 g), and toluene (2.59 g) prepared in Example 18 were mixed and stirred until a homogeneous solution was formed. This solution was transferred to a reaction flask under argon protection. The reaction system was heated to 150 °C, and a free radical initiator (di-tert-butyl peroxide, 0.0519 g) was added. The reaction was continued at 300 rpm for 5 h at this temperature. After the reaction was complete, the product was rapidly dissolved in an organic solvent (tetrahydrofuran, 50 ml), then dispersed in a second organic solvent (methanol, 500 ml), and precipitated to initially precipitate the polymer. Subsequently, the above "dissolution-precipitation" steps were repeated three times for further purification. The final product was collected by vacuum filtration and dried under high vacuum at 60 °C for 12 h to obtain the bio-based flame-retardant polystyrene resin.

[0145] Example data testing:

[0146] The samples prepared in Examples 12-15 were subjected to DSC and limiting oxygen index tests, and the test results are shown in Table 1.

[0147] Table 1. Performance comparison of Examples 12-15 using commercial PS.

[0148]

[0149] Analysis of Table 1 shows that the lignin-based reactive flame retardant prepared in the embodiments of the present invention has good compatibility with petroleum-based styrene and is reliable in its application in flame-retardant modified styrene materials. This approach significantly improves the heat resistance and flame-retardant stability of the material while maintaining its basic properties, specifically by increasing the glass transition temperature (Tg) by 22% and the limiting oxygen index (LOI) by 44%, demonstrating great application potential.

[0150] Although specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that, based on the technical solutions disclosed in this invention, any modifications or equivalent substitutions that can be made by those skilled in the art without inventive effort should still be considered to fall within the scope of protection of the claims of this invention.

Claims

1. A type of lignin-based reactive flame retardant, characterized in that, The general structural formula of the mass-based reactive flame retardant is: ； Wherein, R1 is selected from one of H and OMe; R2 is selected from one of H, OMe and OH; and R3 is a phosphoryl chloride functional monomer with high reactivity.

2. The lignin-based reactive flame retardant according to claim 1, characterized in that, The phosphoryl chloride functional monomer is selected from any one of the structures shown in Formula 1 to Formula 25; 。 3. A method for preparing a lignin-based reactive flame retardant as described in claim 1 or 2, characterized in that, First, lignin phenolic compounds are quantitatively converted into lignin vinylphenol monomers through decarboxylation, and then phosphorylated with phosphoryl chloride monomers to synthesize lignin-based reactive flame retardants containing vinylbenzene structures; including the following steps: Step S1: Add lignin phenolic compounds, the first organic solvent and the acid-binding agent to the reaction apparatus, and reflux at 80~150°C for 6~12 h to obtain lignin vinylphenol monomer; Step S2: The lignin-derived vinylphenol monomer, the second organic solvent, and the acid-binding agent are slowly added dropwise to phosphoryl chloride monomer at -10 to 10°C for 1 to 3 hours. Then the temperature is raised to 50 to 80°C and the reaction continues for 12 to 24 hours to obtain the lignin-based reactive flame retardant.

4. A method for preparing a type of lignin-based reactive flame retardant according to claim 1 or 2, as described in claim 3, characterized in that, In step S1: The molar ratio of the lignin phenolic compound, the first organic solvent, and the acid-binding agent is 1:(3~5):(1.8~2.2). The lignin phenolic compounds mentioned are any one of p-coumaric acid, ferulic acid, caffeic acid, and sinapic acid; The first organic solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, acetonitrile, and 1,4-dioxane; The acid-binding agent is selected from at least one of triethylamine and pyridine; The reaction apparatus described herein is in a high-purity nitrogen or high-purity argon atmosphere.

5. A method for preparing a type of lignin-based reactive flame retardant according to claim 1 or 2, as described in claim 3, characterized in that, In step S2: The molar ratio of the phenolic monomer, the second organic solvent, the acid-binding agent, and the phosphoryl chloride monomer is 1:(3~5):(1.8-2.2):(1.2-2.0). The acid-binding agent is selected from at least one of triethylamine and pyridine; The second organic solvent is at least one of acetone, dichloromethane, chloroform, tetrahydrofuran, acetonitrile, methyl tert-butyl ether, and 1,4-dioxane; The reaction in step S2 is carried out in a high-purity nitrogen or high-purity argon atmosphere.

6. A method for preparing a type of lignin-based reactive flame retardant according to claim 1 or 2, as described in claim 4 or 5, characterized in that, In step S1, the first organic solvent is preferably N,N-dimethylformamide or N-methylpyrrolidone; in step S2, the second organic solvent is preferably acetone or tetrahydrofuran.

7. The application of a class of reactive flame retardants with a lignin-based vinylbenzene structure as described in claim 1 or 2, characterized in that, It is applied to the preparation of lignin-based flame-retardant styrene resins, the structural formula of which is: ； Wherein, m>0, n>0, m+n=100; R1 is selected from H, OMe; R2 is selected from H, OMe, OH; and R3 is a phosphoryl chloride functional monomer with high reactivity.

8. A method for preparing a lignin-based flame-retardant polystyrene resin as described in claim 7, characterized in that, Includes the following steps: Step S1: Add lignin-based reactive flame retardant, styrene, a small amount of solvent and free radical initiator to the reaction apparatus, polymerize at 90 ~ 150 °C for 5 ~ 10 h, stirring at 150 ~ 300 rpm, and dissolve the product in the first organic solution to obtain a high concentration product solution. Step S2: The high-concentration product solution obtained in S1 is dispersed in the second organic solution and allowed to settle, initially precipitating the polymer; Step S3: Further purification is carried out through multiple "dissolution-precipitation" steps. The final product is collected by vacuum filtration and dried under high vacuum to obtain lignin-based flame-retardant polystyrene resin.

9. The method for preparing lignin-based flame-retardant polystyrene resin according to claim 8, characterized in that, In step S1: The lignin-based reactive flame retardant and styrene constitute a styrene phase, and are fed in a molar ratio of 10-50 parts of lignin-based reactive flame retardant and 50-90 parts of styrene; the mass ratio of the styrene phase, a small amount of solvent, and free radical initiator is 100:(10-30):(0.01-0.4). The first organic solution is at least one of dichloromethane, chloroform, and tetrahydrofuran; wherein, 30-50 g of the lignin-based flame-retardant polystyrene resin to be purified is dissolved in every 50 mL of the first organic solution. The small amount of solvent is either toluene or ethylbenzene; The free radical initiator is any one of benzoyl peroxide, di-o-methylbenzoyl peroxide, acetyl isobutyryl peroxide, di-tert-butyl peroxide, 1,1-di(tert-butylperoxide)cyclohexane, and azobisisobutyronitrile; The reaction apparatus is all in a high-purity nitrogen or high-purity argon atmosphere.

10. The method for preparing the lignin-based flame-retardant polystyrene resin according to claim 9, characterized in that, In step S2: The second organic solution is at least one of methanol and ethanol; wherein, 20 to 50 mL of high-concentration product solution is added to every 500 mL of the second organic solution. The vacuum drying temperature is 40 ~ 80 °C, and the drying time is 12 ~ 48 h.

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