Bio-based spiral macromolecular flame retardant as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of high polymer materials, and discloses a bio-based spiral macromolecular flame retardant as well as a preparation method and application thereof. The novel bio-based spiral macromolecular flame retardant PDVPA is successfully prepared on the basis of common industrial raw materials in combination with bio-based renewable vanillin, and the novel bio-based spiral macromolecular flame retardant PDVPA is applied to preparation of a flame-retardant TPEE composite material by adopting a melt blending process. The phosphorus element in the PDVPA molecular structure is used as a main flame-retardant functional group, and can promote the charring of the spiral structure of the PDVPA molecular structure; meanwhile, an imine bond can be subjected to a trimerization reaction under a high-temperature condition to form a cross-linked network structure, so that the molten drop phenomenon during TPEE combustion is effectively inhibited. The invention provides a new way for improving the safety performance of the high polymer material and reducing the dependence on fossil resources.

Description

Technical Field

[0001] This invention relates to the field of polymer technology, specifically to a bio-based helical macromolecular flame retardant, its preparation method, and its application in thermoplastic polyester elastomers. Background Technology

[0002] Thermoplastic polyester elastomer (TPEE) is a block copolymer with a microphase-separated structure. Its molecular chain consists of hard segments (crystalline polyester segments) and soft segments, combining the processing properties of thermoplastics with the high elasticity of rubber materials. TPEE exhibits excellent mechanical properties, a wide operating temperature range, and good chemical stability, showing high resistance to oils, solvents, and UV / ozone aging. In terms of processing, TPEE can be molded using conventional thermoplastic processing methods such as injection molding and extrusion, and it has good recyclability. However, TPEE materials face significant fire risks in various application scenarios. Its limiting oxygen index (LOI) is only 17.9%, classifying it as an extremely flammable material. During combustion, it releases a large amount of heat and toxic gases, accompanied by severe dripping, easily igniting surrounding combustibles and exacerbating the spread of fire. Given these characteristics, ordinary TPEE materials pose a high fire hazard in practical use. Therefore, flame-retardant treatment of TPEE is of significant practical importance for improving its application safety and reducing fire risks.

[0003] Phosphorus oxychloride (POCl3) and phosphorus trichloride (PCl3) are frequently used in flame retardants due to their tendency to undergo nucleophilic substitution reactions with alcohols to form phosphate esters. Among these, the symmetric spirocyclic pentaerythritol diphosphate dichloro ester (SPDPC), synthesized from phosphorus oxychloride and pentaerythritol via a condensation reaction, possesses a unique molecular structure. This compound combines an acid source (phosphate ester structure) and a carbon source (pentaerythritol skeleton), and its active P-Cl bonds at both ends provide ideal reaction sites for constructing macromolecular flame retardants. In recent years, with increasingly stringent global environmental regulations and the continuous depletion of fossil fuel reserves, traditional flame retardants face severe challenges in terms of production costs, energy consumption, and environmental impact. This has prompted academia and industry to accelerate the development of bio-based flame retardant alternatives based on renewable resources. Among numerous bio-based compounds, vanillin, currently the only bio-based aromatic monomer that has achieved industrial-scale production, has become an ideal precursor for constructing high-performance macromolecular flame retardants due to the modifiability of its molecular structure. Therefore, molecular synergistic design of vanillin and SPDPC not only aligns with the concepts of green chemistry and sustainable development, but also fully leverages the characteristics of vanillin's aromatic ring structure, thereby improving the efficiency of the flame retardant system.

[0004] Schiff bases, or imine bonds, are formed by the condensation reaction of primary amines with aldehydes or ketones. Their dynamic and reversible nature makes them highly promising for the design of self-healing and recyclable crosslinked polymers. Recent studies have shown that imine bonds can undergo intramolecular crosslinking reactions under high-temperature conditions to form stable CN six-membered ring structures, thereby significantly enhancing the thermal stability and density of the char layer during combustion. Based on this mechanism, combining the high-temperature self-crosslinking properties of Schiff bases with the char-forming effect of macromolecular flame retardants holds promise for synergistically improving the efficiency of flame-retardant systems. Summary of the Invention

[0005] To address the problems of existing thermoplastic polyester elastomers (TPEE) being extremely flammable (LOI < 18%), generating a large number of molten droplets during combustion, and the tendency of traditional small-molecule flame retardants to migrate and cause a decline in flame retardant performance, this invention provides a flame-retardant modification strategy for TPEE based on macromolecular flame retardants. Using pentaerythritol and phosphorus oxychloride as starting materials, and utilizing the bio-based monomer vanillin, this invention prepares a bio-based flame retardant with a macromolecular structure through a series of reactions. This flame retardant molecule simultaneously contains phosphorus (flame-retardant functional group), a helical structure (char-forming group), and imine bonds (molten droplet-inhibiting functional group), and meets the processing requirements of TPEE. This invention uses bio-based renewable compounds as raw materials to prepare a highly efficient and environmentally friendly macromolecular flame retardant through simple chemical reactions, and uses it to prepare TPEE composite materials with flame-retardant and comprehensive properties, demonstrating broad application prospects.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for preparing a bio-based helical macromolecular flame retardant and its application in thermoplastic polyester elastomers, characterized by comprising the following steps:

[0008] (1) Under nitrogen protection, pentaerythritol and a certain amount of phosphorus oxychloride were added to a round-bottom flask equipped with a reflux device and a magnetic stirrer. First, the temperature was raised to 70-90℃ and the reaction was maintained at this temperature. Then, the temperature was raised to 100-120℃ and the reaction was continued for about 6-10 hours until no HCl gas was released. After the reaction was completed, the system was cooled to room temperature, the precipitate was collected by filtration, and washed three times with chloroform and diethyl ether. Finally, the obtained white solid was dried in a vacuum drying oven at 60℃ for 24 hours to obtain the target intermediate SPDPC.

[0009] (2) Under nitrogen protection, SPDPC, hydroxy aldehyde compounds, and reaction solvent were added to a three-necked round-bottom flask equipped with a magnetic stirrer. After stirring at room temperature for 30 min, the acid-binding agent was added to the mixture over 60 min, followed by stirring at room temperature for 6 h. After the reaction was completed, the mixture was filtered to obtain a white solid, which was washed three times with deionized water and then dried in a vacuum drying oven at 60 °C for 12 h to obtain the target intermediate PDV.

[0010] (3) Under a nitrogen atmosphere, PDV, diamine compounds, and reaction solvent were added to a three-necked round-bottom flask equipped with a reflux condenser and a magnetic stirrer, and heated until dissolved. The temperature was then raised to 90-110℃, and the reaction was carried out for 5-8 hours, followed by cooling to room temperature. The yellow solid was filtered, washed three times with DMF, and then dried in a vacuum drying oven at 70℃ to constant weight to obtain the target product PDVPA.

[0011] (4) The thermoplastic polyester elastomer (TPEE) and the flame retardant PDVPA prepared in step (3) were dried in a vacuum oven at 100°C for 12 hours before use. TPEE and PDVPA were melt-mixed in a torque rheometer at 190-210°C at a mixing speed of 40 rpm. The sample was named TPEE / XPDVPA, where X represents m(PDVPA) / m[(PDVPA)+(TPEE)].

[0012] Preferably, in step (1), the weight of phosphorus oxychloride added is 5-7 times the weight of pentaerythritol.

[0013] Preferably, in step (1), the reaction time of the heating reaction stage at 70-90°C is 3-5 hours.

[0014] Preferably, in step (2), the bio-based hydroxy aldehyde compound is at least one of vanillin, eugenol, p-hydroxycinnamaldehyde, dihydrosinic aldehyde, and 5-hydroxymethylfurfural.

[0015] Preferably, in step (2), the acid-binding agent is at least one of pyridine, triethylamine, sodium carbonate, potassium carbonate and sodium acetate.

[0016] Preferably, in step (2), the reaction solvent is at least one of acetone, tetrahydrofuran, acetonitrile, and N,N-dimethylformamide.

[0017] Preferably, in step (2), the amount of reaction solvent added is 8-12 times the weight of the SPDPC monomer.

[0018] Preferably, in step (3), the diamine compound is at least one of ethylenediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine and p-phenylenediamine.

[0019] Preferably, in step (3), the reaction solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, toluene, and xylene.

[0020] Preferably, in step (4), the temperature of the torque rheometer is set to 190-210°C.

[0021] In one embodiment, this application provides a bio-based helical macromolecular flame retardant prepared by the method described above.

[0022] In another embodiment, this application provides a thermoplastic elastomer composition comprising a thermoplastic polyester elastomer (TPEE) and the flame retardant PDVPA as described in claim 7.

[0023] Compared with the prior art, the present invention has the following obvious and prominent substantive features and significant advantages:

[0024] 1. This invention provides a method for synthesizing a bio-based macromolecular helical flame retardant, which can effectively solve the problem of easy migration of traditional small molecule flame retardants leading to the degradation of flame retardant performance, and can be used to prepare flame-retardant TPEE, thus broadening its application field;

[0025] 2. The raw materials used in this invention are widely available, and the use of renewable vanillin helps to reduce the use of large amounts of fossil raw materials;

[0026] 3. The synthesis process used in this invention has mild reaction conditions, is simple, safe, green and environmentally friendly, and conforms to the concept of green chemistry. Attached Figure Description

[0027] Figure 1 The PDVPA synthesis route;

[0028] Figure 2 The FTIR spectrum of PDVPA;

[0029] Figure 3 For PDVPA 1 H NMR, 13 C NMR and 31 P NMR spectrum;

[0030] Figure 4 For TPEE / PDVPA self-extinguishing test. Detailed Implementation

[0031] Unless otherwise stated, implied from the context, or as is customary in the art, all parts and percentages in this application are based on weight, and all testing and characterization methods used are concurrent with the filing date of this application. Where applicable, any patent, patent application, or disclosure relating to this application is incorporated herein by reference in its entirety, and its equivalent patent families are also incorporated herein by reference, particularly the definitions disclosed in these documents concerning synthetic techniques, product and processing design, polymers, comonomers, initiators, or catalysts in the art. If any definition of a specific term disclosed in the prior art is inconsistent with any definition provided in this application, the definition provided in this application shall prevail.

[0032] The numerical ranges in this application are approximate values ​​and therefore may include values ​​outside the range unless otherwise stated. A numerical range includes all values ​​from the lower limit to the upper limit, increasing by one unit, provided there is an interval of at least two units between any lower and any higher value. For example, if a component, physical, or other property (such as molecular weight, melt index, etc.) is described as 100 to 1000, this means that all individual values, such as 100, 101, 102, etc., are explicitly listed, as well as all subranges, such as 100 to 166, 155 to 170, 198 to 200, etc. For ranges containing values ​​less than 1 or fractions greater than 1 (e.g., 1.1, 1.5, etc.), one unit is appropriately considered as 0.0001, 0.001, 0.01, or 0.1. For ranges containing single digits less than 10 (e.g., 1 to 5), one unit is generally considered as 0.1. These are merely specific examples of what is intended to be expressed, and all possible combinations of values ​​between the listed minimum and maximum values ​​are considered to be clearly stated in this application. It should also be noted that the terms "first," "second," etc., used herein are not intended to specify a particular order, but are merely used to distinguish substances with different structures.

[0033] When referring to chemical compounds, unless explicitly stated otherwise, the singular includes all isomers and vice versa (e.g., "hexane" includes all isomers of hexane, individually or collectively). Additionally, unless explicitly stated otherwise, nouns described with "an," "a," or "the" also include their plural forms.

[0034] The terms “comprising,” “including,” “having,” and their derivatives do not exclude the presence of any other components, steps, or processes, regardless of whether such other components, steps, or processes are disclosed in this application. To eliminate any doubt, unless expressly stated otherwise, all compositions using the terms “comprising,” “including,” or “having” in this application may contain any additional additives, excipients, or compounds. Conversely, except for those necessary for operational performance, the term “substantially constitutes…” excludes any other components, steps, or processes described below with respect to that term. The term “consisting of…” does not include any components, steps, or processes not specifically described or listed. Unless expressly stated otherwise, the term “or” refers to the individual members listed or any combination thereof.

[0035] In one specific embodiment, this application provides a method for preparing a bio-based helical macromolecular flame retardant and its application in thermoplastic polyester elastomers, characterized by comprising the following steps:

[0036] (1) Under nitrogen protection, pentaerythritol and a certain amount of phosphorus oxychloride were added to a round-bottom flask equipped with a reflux device and a magnetic stirrer. First, the temperature was raised to 70-90℃ and the reaction was maintained at this temperature. Then, the temperature was raised to 100-120℃ and the reaction was continued for about 6-10 hours until no HCl gas was released. After the reaction was completed, the system was cooled to room temperature, the precipitate was collected by filtration, and washed three times with chloroform and diethyl ether. Finally, the obtained white solid was dried in a vacuum drying oven at 60℃ for 24 hours to obtain the target intermediate SPDPC.

[0037] (2) Under nitrogen protection, SPDPC, hydroxy aldehydes, and reaction solvent were added to a three-necked round-bottom flask equipped with a magnetic stirrer. After stirring at room temperature for 30 min, the acid-binding agent was added dropwise to the mixture over 60 min, followed by stirring at room temperature for 6 h. After the reaction was completed, the mixture was filtered to obtain a white solid, which was washed three times with deionized water and then dried in a vacuum drying oven at 60 °C for 12 h to obtain the target intermediate PDV.

[0038] (3) Under a nitrogen atmosphere, PDV, diamine compounds, and reaction solvent were added to a three-necked round-bottom flask equipped with a reflux condenser and a magnetic stirrer, and heated until dissolved. The temperature was then raised to 90-110℃, and the reaction was carried out for 5-8 hours, followed by cooling to room temperature. The yellow solid was filtered, washed three times with DMF, and then dried in a vacuum drying oven at 70℃ to constant weight to obtain the target product PDVPA.

[0039] (4) The thermoplastic polyester elastomer (TPEE) and the flame retardant PDVPA prepared in step (3) were dried in a vacuum oven at 100°C for 12 hours before use. TPEE and PDVPA were melt-mixed in a torque rheometer at 190-210°C at a mixing speed of 40 rpm. The sample was named TPEE / XPDVPA, where X represents m(PDVPA) / m[(PDVPA)+(TPEE)].

[0040] In step (1), the weight of phosphorus oxychloride added is 5-7 times the weight of pentaerythritol. In a specific embodiment, the weight of phosphorus oxychloride added is 6 times the weight of pentaerythritol.

[0041] In step (1), the low-temperature reaction stage lasts for 3-5 hours. In a specific embodiment, the 70-90°C heating reaction stage lasts for 4 hours.

[0042] In step (2), the bio-based hydroxy aldehyde compound is at least one of vanillin, syringaldehyde, p-hydroxycinnamaldehyde, dihydrosinic aldehyde, and 5-hydroxymethylfurfural. In a specific embodiment, vanillin is selected as the bio-based hydroxy aldehyde compound.

[0043] In step (2), the acid-binding agent is at least one selected from pyridine, triethylamine, sodium carbonate, potassium carbonate, and sodium acetate. In a specific embodiment, triethylamine is selected as the acid-binding agent.

[0044] In step (2), the reaction solvent is at least one of acetone, tetrahydrofuran, acetonitrile, and N,N-dimethylformamide. In a specific embodiment, acetonitrile is selected as the reaction solvent.

[0045] In step (2), the amount of reaction solvent added is 8-12 times the weight of the SPDPC monomer. In a specific embodiment, the amount of reaction solvent added is 10 times the weight of the SPDPC monomer.

[0046] In step (3), the diamine compound is at least one selected from ethylenediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine, and p-phenylenediamine. In a specific embodiment, p-phenylenediamine is used as the diamine compound.

[0047] In step (3), the reaction solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, toluene, and xylene. In a specific embodiment, N,N-dimethylformamide is used as the reaction solvent.

[0048] In step (4), the temperature of the torque rheometer is set to 190-210°C. In a specific embodiment, the temperature of the torque rheometer is set to 200°C.

[0049] The above solution will be further described below with reference to specific embodiments. The preferred embodiments of the present invention are described in detail below:

[0050] Example 1

[0051] In this embodiment, a method for preparing a bio-based helical macromolecular flame retardant and its application in thermoplastic polyester elastomers includes the following steps:

[0052] Step 1: Under nitrogen protection, 20.0 g of pentaerythritol and 120.0 g of phosphorus oxychloride were added to a 250 ml three-necked round-bottom flask equipped with a reflux apparatus and a magnetic stirrer. First, the mixture was heated to 80 °C and stirred for 4 h. Then, the temperature was increased to 110 °C and the reaction was continued for approximately 7 h until no more HCl gas was released. After the reaction was complete, the system was cooled to room temperature, the precipitate was collected by filtration, and washed three times with chloroform and diethyl ether. Finally, the resulting white solid was dried in a vacuum drying oven at 60 °C for 24 h to obtain the target intermediate SPDPC.

[0053] Step 2: Under nitrogen protection, 20.2 g of SPDPC, 21.7 g of vanillin, and 200 mL of acetonitrile were added to a 250 mL three-necked round-bottom flask equipped with a magnetic stirrer. After stirring at room temperature for 30 min, 14.3 g of triethylamine was added dropwise to the mixture over 60 min, followed by stirring at room temperature for 6 h. After the reaction was complete, the mixture was filtered to obtain a white solid, which was washed three times with deionized water and then dried in a vacuum drying oven at 60 °C for 12 h to obtain the target intermediate PDV.

[0054] Step 3: Under a nitrogen atmosphere, 25.2 g of PDV, 5.3 g of p-phenylenediamine, and 100 mL of DMF were added to a 250 mL three-necked round-bottom flask equipped with a reflux condenser and a magnetic stirrer, and heated until dissolved. The temperature was then raised to 100 °C, and the reaction was carried out for 6 hours, followed by cooling to room temperature. The yellow solid was filtered, washed three times with DMF, and then dried in a vacuum drying oven at 70 °C to constant weight to obtain the target product PDVPA.

[0055] Step 4: Dry TPEE and flame retardant PDVPA in a vacuum oven at 100°C for 12 hours before use. Melt and mix TPEE and PDVPA in a torque rheometer at 200°C at a mixing speed of 40 rpm. Name the sample TPEE / XPDVPA, where X represents (mPDVPA) / m[(PDVPA)+(TPEE)].

[0056] Example 2

[0057] This embodiment is basically the same as Embodiment 1, except that:

[0058] In this embodiment, a method for preparing a bio-based helical macromolecular flame retardant and its application in thermoplastic polyester elastomers includes the following steps:

[0059] Step 1: Under nitrogen protection, 20.0 g of pentaerythritol and 120.0 g of phosphorus oxychloride were added to a 250 ml three-necked round-bottom flask equipped with a reflux apparatus and a magnetic stirrer. First, the mixture was heated to 80 °C and stirred for 4 h. Then, the temperature was increased to 110 °C and the reaction was continued for approximately 7 h until no more HCl gas was released. After the reaction was complete, the system was cooled to room temperature, the precipitate was collected by filtration, and washed three times with chloroform and diethyl ether. Finally, the resulting white solid was dried in a vacuum drying oven at 60 °C for 24 h to obtain the target intermediate SPDPC.

[0060] Step 2: Under nitrogen protection, 20.2 g of SPDPC, 21.7 g of vanillin, and 200 mL of acetonitrile were added to a 250 mL three-necked round-bottom flask equipped with a magnetic stirrer. After stirring at room temperature for 30 min, 14.3 g of triethylamine was added dropwise to the mixture over 60 min, followed by stirring at room temperature for 6 h. After the reaction was complete, the mixture was filtered to obtain a white solid, which was washed three times with deionized water and then dried in a vacuum drying oven at 60 °C for 12 h to obtain the target intermediate PDV.

[0061] Step 3: Under a nitrogen atmosphere, 25.2 g of PDV, 5.3 g of p-phenylenediamine, and 100 mL of DMF were added to a 250 mL three-necked round-bottom flask equipped with a reflux condenser and a magnetic stirrer, and heated until dissolved. The temperature was then raised to 100 °C, and the reaction was carried out for 6 hours, followed by cooling to room temperature. The yellow solid was filtered, washed three times with DMF, and then dried in a vacuum drying oven at 70 °C to constant weight to obtain the target product PDVPA.

[0062] Step 4: Dry TPEE and PDVPA in a vacuum oven at 100℃ for 12 hours before use. Melt and mix 45.0g TPEE and 5.0g PDVPA in a torque rheometer at 200℃ at a mixing speed of 40rpm. Name the sample TPEE / 10PDVPA.

[0063] Example 3

[0064] This embodiment is basically the same as Embodiment 1, except that:

[0065] In this embodiment, a method for preparing a bio-based helical macromolecular flame retardant and its application in thermoplastic polyester elastomers includes the following steps:

[0066] Step 1: Under nitrogen protection, 20.0 g of pentaerythritol and 120.0 g of phosphorus oxychloride were added to a 250 ml three-necked round-bottom flask equipped with a reflux apparatus and a magnetic stirrer. First, the mixture was heated to 80 °C and stirred for 4 h. Then, the temperature was increased to 110 °C and the reaction was continued for approximately 7 h until no more HCl gas was released. After the reaction was complete, the system was cooled to room temperature, the precipitate was collected by filtration, and washed three times with chloroform and diethyl ether. Finally, the resulting white solid was dried in a vacuum drying oven at 60 °C for 24 h to obtain the target intermediate SPDPC.

[0067] Step 2: Under nitrogen protection, 20.2 g of SPDPC, 21.7 g of vanillin, and 200 mL of acetonitrile were added to a 250 mL three-necked round-bottom flask equipped with a magnetic stirrer. After stirring at room temperature for 30 min, 14.3 g of triethylamine was added dropwise to the mixture over 60 min, followed by stirring at room temperature for 6 h. After the reaction was complete, the mixture was filtered to obtain a white solid, which was washed three times with deionized water and then dried in a vacuum drying oven at 60 °C for 12 h to obtain the target intermediate PDV.

[0068] Step 3: Under a nitrogen atmosphere, 25.2 g of PDV, 5.3 g of p-phenylenediamine, and 100 mL of DMF were added to a 250 mL three-necked round-bottom flask equipped with a reflux condenser and a magnetic stirrer, and heated until dissolved. The temperature was then raised to 100 °C, and the reaction was carried out for 6 hours, followed by cooling to room temperature. The yellow solid was filtered, washed three times with DMF, and then dried in a vacuum drying oven at 70 °C to constant weight to obtain the target product PDVPA.

[0069] Step 4: Dry TPEE and PDVPA in a vacuum oven at 100℃ for 12 hours before use. Melt and mix 42.5g TPEE and 7.5g PDVPA in a torque rheometer at 200℃ at a mixing speed of 40rpm. Name the sample TPEE / 15PDVPA.

[0070] Example 4

[0071] This embodiment is basically the same as Embodiment 1, except that:

[0072] In this embodiment, a method for preparing a bio-based helical macromolecular flame retardant and its application in thermoplastic polyester elastomers includes the following steps:

[0073] Step 1: Under nitrogen protection, 20.0 g of pentaerythritol and 120.0 g of phosphorus oxychloride were added to a 250 ml three-necked round-bottom flask equipped with a reflux apparatus and a magnetic stirrer. First, the mixture was heated to 80 °C and stirred for 4 h. Then, the temperature was increased to 110 °C and the reaction was continued for approximately 7 h until no more HCl gas was released. After the reaction was complete, the system was cooled to room temperature, the precipitate was collected by filtration, and washed three times with chloroform and diethyl ether. Finally, the resulting white solid was dried in a vacuum drying oven at 60 °C for 24 h to obtain the target intermediate SPDPC.

[0074] Step 2: Under nitrogen protection, 20.2 g of SPDPC, 21.7 g of vanillin, and 200 mL of acetonitrile were added to a 250 mL three-necked round-bottom flask equipped with a magnetic stirrer. After stirring at room temperature for 30 min, 14.3 g of triethylamine was added dropwise to the mixture over 60 min, followed by stirring at room temperature for 6 h. After the reaction was complete, the mixture was filtered to obtain a white solid, which was washed three times with deionized water and then dried in a vacuum drying oven at 60 °C for 12 h to obtain the target intermediate PDV.

[0075] Step 3: Under a nitrogen atmosphere, 25.2 g of PDV, 5.3 g of p-phenylenediamine, and 100 mL of DMF were added to a 250 mL three-necked round-bottom flask equipped with a reflux condenser and a magnetic stirrer, and heated until dissolved. The temperature was then raised to 100 °C, and the reaction was carried out for 6 hours, followed by cooling to room temperature. The yellow solid was filtered, washed three times with DMF, and then dried in a vacuum drying oven at 70 °C to constant weight to obtain the target product PDVPA.

[0076] Step 4: Dry TPEE and PDVPA in a vacuum oven at 100℃ for 12 hours before use. Melt and mix 40.0g TPEE and 10.0g PDVPA in a torque rheometer at 200℃ at a mixing speed of 40rpm. Name the sample TPEE / 20PDVPA.

[0077] Table 1 Vertical Combustion Test and Oxygen Index Test

[0078]

[0079] Experimental test analysis

[0080] like Figure 2 As shown in the FTIR spectrum of PDVPA, 1280, 1200, and 547 cm⁻¹ -1 The characteristic absorption peaks at 3200 cm⁻¹ are attributed to the P=O, POC, and P-Cl functional groups in the phosphoryl chloride structure of SPDPC, respectively. Meanwhile, at 3200 cm⁻¹... -1 and 1690cm -1 The broad absorption peaks at 1670 cm⁻¹ correspond to the -OH and C=O groups in the CHO group of V-CHO, respectively. In the FTIR spectrum of PDV, the characteristic absorption peaks of the P-Cl group in the SPDPC structure and the -OH group in the V-CHO structure disappear, while the characteristic absorption peaks of -CHO (1670 cm⁻¹) are... -1 P = O (1280cm) -1 ) and POC (1200cm -1The retention of the absorption peak indicates a nucleophilic substitution reaction between V-CHO and SPDPC. Finally, PDV and PDA were synthesized via an aldehyde-amine condensation reaction. In the FTIR spectrum of PDVPA, the C=O (1670 cm⁻¹) value in the PDV molecule is attributed to this peak. -1 The absorption peak disappeared, and at 1622 cm⁻¹ -1 The appearance of a new absorption peak belonging to C=N at this point proves the successful preparation of PDVPA with the target structure.

[0081] like Figure 3 As shown, in PDVPA 1 H NMR spectrum ( Figure 3 (ab) Chemical shift peaks of all hydrogen atoms corresponding to the imine bond, benzene ring, and helical ring structures in the PDVPA molecular structure were observed. PDVPA's 13 In the C NMR spectrum ( Figure 3 c) All characteristic carbon resonance peaks belonging to PDVPA can be found. Furthermore, in 31 In the P NMR spectrum ( Figure 3 d) Multiple resonance peaks appeared near 13.4 ppm, a feature that indicates the presence of phosphorus atoms in multiple chemical environments in the molecule.

[0082] like Figure 4 As shown, in the UL-94 test, pure TPEE is easily ignited, producing a large number of molten droplets during combustion and failing to self-extinguish, with an LOI value of only 17.9%. The addition of PDVPA significantly improves the flame retardant properties of TPEE materials. When 10 wt% PDVPA is added to the TPEE matrix, the TPEE / 10 PDVPA composite material can self-extinguish after the first ignition, but after the second ignition, a small amount of molten droplets are still produced, igniting the underlying absorbent cotton, achieving only a V-2 rating. When the PDVPA content is increased to 20 wt%, the LOI value of the TPEE / 20 PDVPA composite material increases to 30.2%, while producing only a small amount of molten droplets during combustion and exhibiting good self-extinguishing characteristics, achieving a V-0 rating.

[0083] In summary, in this embodiment of the invention, a novel bio-based macromolecular helical flame retardant was prepared through a series of reactions using pentaerythritol and phosphorus oxychloride as raw materials, combined with bio-based renewable vanillin. This flame retardant was then applied to the preparation of flame-retardant TPEE. Experimental results show that the synthesized flame retardant PDVPA can be uniformly dispersed in the TPEE matrix and exhibits good interfacial compatibility. When the PDVPA addition amount is 20 wt%, the LOI of the TPEE / PDVPA composite material reaches 29.2%, demonstrating excellent self-extinguishing performance and achieving a UL-94V-0 rating. Furthermore, this composite material can effectively suppress dripping and exhibits good flame retardant durability; after one week of boiling in water, its flame retardant performance did not show a significant decrease.

[0084] The above embodiments provide a method for preparing a bio-based helical macromolecular flame retardant and its application in thermoplastic polyester elastomers. This method, based on common raw materials and combined with bio-based renewable vanillin, successfully prepared a novel bio-based macromolecular helical flame retardant, PDVPA. In this molecular structure, phosphorus acts as the main flame-retardant functional group, which helps promote the char formation process of the helical structure; simultaneously, the imine bonds can undergo trimerization under high-temperature conditions to form a cross-linked network structure, thereby effectively inhibiting the dripping phenomenon of TPEE during combustion. The preparation process of PDVPA has mild reaction conditions and is simple to operate, showing good application prospects and practical value. This research provides a new approach to improving the safety performance of polymer materials and reducing dependence on fossil fuels.

[0085] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made according to the purpose of the invention. Any changes, modifications, substitutions, combinations or simplifications made based on the spirit and principle of the technical solution of the present invention shall be equivalent substitutions. As long as they meet the purpose of the invention and do not deviate from the technical principle and inventive concept of the present invention, they shall fall within the protection scope of the present invention.

Claims

1. A method for preparing a bio-based helical macromolecular flame retardant, characterized in that, Comprising the following steps: (1) Under nitrogen protection, pentaerythritol and a certain amount of phosphorus oxychloride are added into a round-bottom flask equipped with reflux device and magnetic stirrer. First, the temperature is raised to 70-90℃, and the reaction is kept at this temperature; then, the temperature is raised to 100-120℃, and the reaction is continued for about 6-10h until no HCl gas is released; after the reaction is completed, the system is cooled to room temperature, the precipitate is filtered and collected, and the precipitate is washed with chloroform and diethyl ether three times; finally, the obtained white solid is placed in a 60℃ vacuum drying oven for drying for 24h to obtain the target intermediate SPDPC; (2) Under nitrogen protection, SPDPC, hydroxy aldehyde compound and reaction solvent are added into a three-necked round-bottom flask equipped with magnetic stirrer; after stirring at room temperature for 30min, the acid-binding agent is added into the mixture within 60min, and then the mixture is stirred at room temperature for 6h; after the reaction is completed, the white solid is filtered and washed with deionized water three times, and then placed in a 60℃ vacuum drying oven for drying for 12h to obtain the target intermediate PDV; (3) Under nitrogen atmosphere, PDV, diamine compound and reaction solvent are added into a three-necked round-bottom flask equipped with reflux condenser and magnetic stirrer, and heated to dissolution. Then, the temperature is raised to 90-110℃, and the reaction is continued for 5-8h, and then the yellow solid is cooled to room temperature, filtered, washed with DMF three times, and then placed in a 70℃ vacuum drying oven for drying to constant weight to obtain the target product PDVPA.

2. The production method according to claim 1, wherein In the step (1), the weight of phosphorus oxychloride added is 5-7 times the weight of pentaerythritol.

3. The production method according to claim 1, wherein In the step (1), the reaction time during the heating reaction stage at 70-90℃ is 3-5h.

4. The production method according to claim 1, wherein In the step (2), the bio-based hydroxy aldehyde compound is at least one of vanillin, syringaldehyde, p-hydroxy cinnamaldehyde, dihydro mustard aldehyde and 5-hydroxymethyl furfural; In the step (2), the acid-binding agent is at least one of pyridine, triethylamine, sodium carbonate, potassium carbonate and sodium acetate.

5. The production method according to claim 1, wherein In the step (2), the reaction solvent is at least one of acetone, tetrahydrofuran, acetonitrile and N,N-dimethylformamide; In the step (2), the amount of reaction solvent added is 8-12 times the weight of SPDPC monomer.

6. The production method according to claim 1, wherein In the step (3), the diamine compound is at least one of ethylenediamine, 1,4-butanediamine, 1,5-pentanediamine, 1,6-hexanediamine and p-phenylenediamine; In the step (3), the reaction solvent is at least one of N,N-dimethylformamide, dimethyl sulfoxide, toluene and xylene.

7. A bio-based helical macromolecular flame retardant characterized in that, Prepared by the preparation method of any one of claims 1-6.

8. Use of the bio-based helical macromolecular flame retardant according to claim 7 in thermoplastic polyester elastomers, characterized in that, The thermoplastic polyester elastomer (TPEE) and the flame retardant PDVPA of claim 7 are dried in a 100℃ vacuum oven for 12h before use, and the TPEE and PDVPA are melt-mixed in a torque rheometer at 190-210℃, with a mixing speed of 40rpm, and the sample is named TPEE / XPDVPA, wherein X represents m(PDVPA) / m[(PDVPA)+(TPEE)].

9. Use according to claim 8, characterized in that, In the step (4), the temperature of the torque rheometer is set to 190-210°C.

10. A thermoplastic elastomer composition comprising a thermoplastic polyester elastomer (TPEE) and the flame retardant PDVPA according to claim 7.

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