Vanillin-derived nitrogen-phosphorus synergistic flame retardant as well as preparation method and application thereof

Abstract

The invention relates to the technical field of flame-retardant materials, in particular to a vanillin-derived nitrogen-phosphorus synergistic flame retardant as well as a preparation method and application thereof. The preparation method comprises the following steps: carrying out aldehyde-amine condensation reaction on vanillin and p-phenylenediamine to generate a Schiff base intermediate with a characteristic group-C = N-; and carrying out addition reaction on the intermediate and reactive hydrogen connected with a phosphorus atom on 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, so as to obtain the vanillin-derived nitrogen-phosphorus synergistic flame retardant. The flame retardant obviously improves the flame retardant grade of the high polymer material under the condition of lower addition amount, does not release toxic and harmful gases in the combustion process, and meets the requirements of greenness and environmental protection. The flame retardant has good compatibility with high polymer materials such as thermoplastic polyurethane and the like. The preparation method of the flame retardant is controllable in reaction process, large-scale production is easy to realize, an innovative and feasible solution is provided for flame retardance of high polymer materials, and the flame retardant is expected to be widely applied to the fields of electronics, automobiles, buildings and the like.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant materials, and in particular to a vanillin-derived nitrogen-phosphorus synergistic flame retardant and a preparation method and application thereof. Background Art

[0002] With the rapid development of modern industry and the continuous improvement of people's safety awareness, the demand for materials with good flame retardant properties is growing. Thermoplastic polyurethane (TPU) is widely used in many fields, such as footwear, clothing, pipes, films and sheets, cables, automobiles, construction, medicine and health, national defense, sports and leisure, etc. It has excellent comprehensive properties such as high strength, high toughness, wear resistance, and oil resistance. However, TPU is flammable and will release a large amount of smoke and toxic gases such as HCN and CO when burning. These toxic gases and large amounts of smoke can suffocate people and cause irreversible damage to the human respiratory tract. At the same time, it is very easy for molten droplets to occur during the combustion process, causing the fire to spread, which has limited the application of its composite materials in related fields. Therefore, the development of efficient flame retardants has become a top priority.

[0003] Traditional flame retardants often have some disadvantages. For example, halogen-containing flame retardants release toxic hydrogen halide gas when burning, which is harmful to the environment and human health; inorganic flame retardants usually require high addition amounts to achieve a good flame retardant effect, which may affect the mechanical properties and processing properties of the material. Nitrogen-phosphorus synergistic flame retardants have many advantages. On the one hand, nitrogen and phosphorus elements can interact with each other during the combustion process to exert a synergistic flame retardant effect. Phosphorus can promote the formation of a carbon layer when the material burns, play a role in heat insulation and oxygen isolation, and prevent the spread of flames; nitrogen can release non-combustible gases, dilute the concentration of combustible gases and oxygen, and thus inhibit combustion. On the other hand, vanillin, as a raw material derived from natural products, has the characteristics of wide sources and green environmental protection, which meets the current requirements of sustainable development.

[0004] Vanillin is a compound extracted from natural plants such as vanilla beans, with unique chemical structure and properties. Flame retardants with specific functions can be synthesized by chemically modifying vanillin. The nitrogen-phosphorus synergistic flame retardant synthesized based on vanillin can not only take advantage of the natural source of vanillin to reduce dependence on non-renewable resources such as petroleum, but also optimize flame retardant properties by adjusting the molecular structure. For example, nitrogen- and phosphorus-containing functional groups can be introduced into the vanillin molecule to give it good thermal stability and flame retardant effect. At the same time, this flame retardant can also be well compatible with polymer materials, while improving the flame retardant properties of the material, it minimizes the impact on the mechanical properties and processing properties of the material.

[0005] In summary, the development of vanillin-derived nitrogen-phosphorus synergistic flame retardants has important technical background and practical significance. Summary of the invention

[0006] In order to solve the above problems, the present invention provides a vanillin-derived nitrogen-phosphorus synergistic flame retardant and a preparation method and application thereof. The present invention uses bio-based vanillin as a raw material to construct a Schiff base derivative containing synergistic nitrogen and phosphorus. The flame retardant has good compatibility with the polymer, has both gas phase and condensed phase dual-phase flame retardant effects, and can give the material excellent flame retardant properties. During the combustion process, in the gas phase, the flame retardant can release water and ammonia, and reduce the concentration of combustible gases through dilution. At the same time, the free radical scavenger produced by decomposition can capture hydrogen radicals and hydroxyl radicals in the combustion process, effectively inhibiting the chain reaction of combustion; in the condensed phase, the flame retardant can cause the polymer to form a denser cross-linked carbon layer. In addition, the phosphoric acid and its derivatives formed will cover the surface of the polymer melt, construct an effective oxygen isolation layer, and hinder the material and energy exchange between the substrate and the burning part.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a vanillin-derived nitrogen-phosphorus synergistic flame retardant, and the structural formula of the vanillin-derived nitrogen-phosphorus synergistic flame retardant is shown in Formula I:

[0009] Formula I.

[0010] The present invention also provides a method for preparing the vanillin-derived nitrogen-phosphorus synergistic flame retardant described in the above technical solution, comprising the following steps:

[0011] 1) Mix vanillin, p-phenylenediamine, an organic solvent, a catalyst and a water absorbent to carry out an aldehyde-amine condensation reaction to obtain a Schiff base intermediate;

[0012] 2) The Schiff base intermediate obtained in step 1) is mixed with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and an organic reagent to carry out an addition reaction to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0013] Preferably, in step 1), the ratio of the mole of vanillin, the mole of p-phenylenediamine, the volume of the organic solvent, the catalyst and the water absorbent is 0.1-0.2 mol: 0.05-0.1 mol: 200-350 ml: 3-4 ml: 2-4 g.

[0014] Preferably, the conditions for the aldehyde-amine condensation reaction in step 1) include: a temperature of 60-80° C. and a time of 6-8 h.

[0015] Preferably, the organic solvent includes one or more of anhydrous ethanol, methanol, formic acid and propanol.

[0016] Preferably, the catalyst in step 1) comprises glacial acetic acid, and the water absorbent comprises anhydrous magnesium sulfate.

[0017] Preferably, in step 2), the volume ratio of the mole of the Schiff base intermediate to the mole of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the organic reagent is 0.05-0.1 mol: 0.1-0.2 mol: 200-350 ml.

[0018] Preferably, the conditions for the addition reaction in step 2) include: a temperature of 80-100° C. and a time of 8-12 h.

[0019] The present invention also provides the use of the vanillin-derived nitrogen-phosphorus synergistic flame retardant described in the above technical solution in improving the flame retardant grade of polymer materials at a lower flame retardant dosage.

[0020] Preferably, the polymer material includes thermoplastic polyurethane and / or epoxy resin.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention synthesizes the flame retardant in two steps through an aldehyde-amine condensation reaction and an addition reaction. The synthesis process is simple, the reaction conditions are easy to control, no harmful products are generated during the reaction process, and large-scale industrial production can be achieved.

[0023] (2) It complies with the current requirements of sustainable development, reduces dependence on non-renewable resources, and provides a green and sustainable solution for the flame retardancy of polymer materials.

[0024] (3) It has a specific chemical structure, in which the characteristic group -C=N- and the phosphaphenanthrene structure cooperate with each other to further enhance the flame retardant effect. Compared with traditional flame retardants, it can achieve good flame retardant properties at a lower addition amount and reduce the impact on other properties of the material.

[0025] (4) Good compatibility allows the flame retardant to improve the flame retardant properties of the material while minimizing the impact on the mechanical properties and processing properties of the material. After adding the flame retardant, the material can still maintain good strength, toughness and processability, meeting the needs of practical applications.

[0026] (5) It has a gas-phase condensed-phase dual-phase flame retardant effect. The vanillin-derived nitrogen-phosphorus synergistic flame retardant generated by the reaction of the Schiff base intermediate obtained by the reaction of vanillin and p-phenylenediamine with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide fully exerts the synergistic flame retardant effect of nitrogen and phosphorus elements. When burning, phosphorus promotes the formation of a carbon layer in the material, plays a role in heat insulation and oxygen isolation, and prevents the spread of flames; nitrogen releases non-combustible gas, dilutes the concentration of combustible gas and oxygen, and inhibits combustion, thereby significantly improving the flame retardant performance.

[0027] This innovative synthesis method provides new ideas and approaches for the development of new flame retardants, which can be applied to the flame retardant modification of thermoplastic polyurethane or epoxy resin. It is also expected to be applied in more polymer material fields and promote the development of flame retardant technology.

[0028] The invention generates a Schiff base intermediate with a characteristic group -C=N- by an aldehyde-amine condensation reaction between vanillin and p-phenylenediamine. Subsequently, the intermediate undergoes an addition reaction with active hydrogen connected to the phosphorus atom on 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant. In the preparation process, the natural source advantage of vanillin and the reactivity of p-phenylenediamine are fully utilized, and the synergistic flame retardant effect of nitrogen and phosphorus elements is combined, so that the obtained flame retardant has high flame retardant performance. The unique chemical structure of the flame retardant enables it to significantly improve the flame retardant grade of polymer materials at a lower addition amount, and at the same time, no toxic and harmful gases are released during the combustion process, which meets the requirements of green environmental protection. In terms of application, the flame retardant has good compatibility with polymer materials such as thermoplastic polyurethane, and can be evenly dispersed in the material without causing obvious phase separation. After adding the flame retardant, the mechanical properties and processing properties of the material are less affected, and good strength, toughness and processability can still be maintained. In addition, the reaction process of the preparation method of this flame retardant is controllable and easy to achieve large-scale production, providing an innovative and feasible solution for the flame retardancy of polymer materials, and is expected to be widely used in electronics, automobiles, construction and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0030] Figure 1 This is an infrared spectrum of the vanillin-derived nitrogen-phosphorus synergistic flame retardant prepared in Example 1;

[0031] Figure 2 This is the thermal gravimetric curve of the vanillin-derived nitrogen-phosphorus synergistic flame retardant prepared in Example 1;

[0032] Figure 3 The vanillin-derived nitrogen-phosphorus synergistic flame retardant prepared in Example 1 1 H-NMP spectrum;

[0033] Figure 4 The vanillin-derived nitrogen-phosphorus synergistic flame retardant prepared in Example 1 31 P-NMP spectrum. DETAILED DESCRIPTION

[0034] The present invention provides a vanillin-derived nitrogen-phosphorus synergistic flame retardant, and the structural formula of the vanillin-derived nitrogen-phosphorus synergistic flame retardant is shown in Formula I:

[0035] Formula I.

[0036] The present invention also provides a method for preparing the vanillin-derived nitrogen-phosphorus synergistic flame retardant described in the above technical solution, comprising the following steps:

[0037] 1) Mix vanillin, p-phenylenediamine, an organic solvent, a catalyst and a water absorbent to carry out an aldehyde-amine condensation reaction to obtain a Schiff base intermediate;

[0038] 2) The Schiff base intermediate obtained in step 1) is mixed with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and an organic reagent to carry out an addition reaction to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0039] The vanillin, p-phenylenediamine, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and organic solvent in the present invention are all industrial products and can be purchased from the market.

[0040] The present invention mixes vanillin, p-phenylenediamine, an organic solvent, a catalyst and a water absorbent, and performs an aldehyde-amine condensation reaction to obtain a Schiff base intermediate. In the present invention, the mole of vanillin, the mole of p-phenylenediamine, the volume of the organic solvent, the catalyst and the water absorbent are preferably 0.1-0.2 mol: 0.05-0.1 mol: 200-350 ml: 3-4 ml: 2-4 g. In the present invention, the conditions of the aldehyde-amine condensation reaction preferably include: a temperature of 60-80 ° C and a time of 6-8 h. The present invention preferably disperses the vanillin and p-phenylenediamine in an organic solvent respectively and then mixes them. The present invention preferably performs the aldehyde-amine condensation reaction under nitrogen protection. The present invention preferably filters the obtained precipitate after the aldehyde-amine condensation reaction, washes it with an organic solvent for 3 times, and vacuum dries it at 80-90 ° C to obtain a Schiff base intermediate. In the present invention, the organic solvent preferably includes one or more of anhydrous ethanol, methanol, formic acid and propanol. In the present invention, the catalyst preferably includes glacial acetic acid, and the water absorbent preferably includes anhydrous magnesium sulfate.

[0041] The present invention mixes the obtained Schiff base intermediate with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and an organic reagent, performs an addition reaction, and obtains a vanillin-derived nitrogen-phosphorus synergistic flame retardant. In the present invention, the mole ratio of the Schiff base intermediate to the mole of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the volume ratio of the organic reagent is preferably 0.05-0.1 mol: 0.1-0.2 mol: 200-350 ml. In the present invention, the conditions of the addition reaction preferably include: a temperature of 80-100 ° C and a time of 8-12 h. In the present invention, the mole of the Schiff base intermediate and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide are preferably dispersed in an organic solvent and then mixed. In the present invention, the organic solvent preferably includes one or more of anhydrous ethanol, methanol, formic acid and propanol. In the present invention, the addition reaction is preferably carried out under nitrogen protection.

[0042] The present invention also provides the use of the vanillin-derived nitrogen-phosphorus synergistic flame retardant described in the above technical solution in improving the flame retardancy of polymer materials at a lower flame retardant dosage. In the present invention, the polymer material preferably includes thermoplastic polyurethane and / or epoxy resin.

[0043] In order to further illustrate the present invention, the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0044] Example 1

[0045] A method for preparing a vanillin-derived nitrogen-phosphorus synergistic flame retardant, comprising the following steps:

[0046] 1) First, in a reactor equipped with a stirrer, 30.43 g (0.2 mol) of vanillin was dispersed in 250 ml of anhydrous ethanol, and then 10.8 g (0.1 mol) of p-phenylenediamine dissolved in 100 ml of anhydrous ethanol was added into a constant pressure separation funnel using 3 ml of glacial acetic acid as a catalyst and 4 g of anhydrous magnesium sulfate as a water absorbent. Secondly, under nitrogen protection, the mixture was heated to 80°C, refluxed for 6 h, then cooled, poured into ice deionized water for precipitation, filtered, washed with anhydrous ethanol three times, and finally dried in vacuum at 80°C to obtain the intermediate Schiff base;

[0047] 2) Disperse 18.82 g (0.1 mol) of the intermediate Schiff base obtained in step 1) with 150 ml of anhydrous ethanol and stir mechanically in a three-hole flask; then add 21.6 g (0.2 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide dissolved in 100 ml of anhydrous ethanol. Under nitrogen protection, heat to 80 ° C and reflux for 12 h, cool the mixture, pour it into ice deionized water for precipitation, filter it, wash it with anhydrous ethanol for 3 times, and finally dry it in vacuum at 80 ° C to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0048] The vanillin-derived nitrogen-phosphorus synergistic flame retardant obtained in Example 1 was tested and analyzed using a Fourier transform infrared spectrometer, a thermogravimetric analyzer, and a nuclear magnetic resonance spectrometer, respectively. Figure 1 , Figure 2 , Figure 3 and Figure 4 . Figure 1 This is the infrared spectrum of the vanillin-derived nitrogen-phosphorus synergistic flame retardant obtained in Example 1; Figure 2 This is a thermogravimetric curve of the vanillin-derived nitrogen-phosphorus synergistic flame retardant obtained in Example 1; Figure 3 The vanillin-derived nitrogen-phosphorus synergistic flame retardant obtained in Example 1 1 H-NMP spectrum, Figure 4 The vanillin-derived nitrogen-phosphorus synergistic flame retardant obtained in Example 1 31 P-NMP spectrum.

[0049] pass Figure 1 It can be seen that: 1257 cm -1 、752 cm -1 The infrared results show that the addition reaction of DOPO causes the C=N double bond to be opened and an addition reaction to form a CN single bond. No infrared characteristic absorption peak of the PH bond is found in the spectrum. -1 The P-Ph bond is at 1202 cm -1 The characteristic absorption peak of P=O bond is 788 cm -1 The absorption peak is the characteristic absorption peak of PC bond.

[0050] pass Figure 2 It can be seen that the thermal decomposition temperature of the flame retardant is about 200 ℃, the temperature corresponding to 5% mass loss is 248 ℃, and the residual carbon weight is 30 wt.%, indicating that the vanillin-derived nitrogen-phosphorus synergistic flame retardant has good thermal stability and char-forming ability.

[0051] pass Figure 3It can be seen that the peak at 8.84 ppm can be attributed to the chemical shift of active -OH, while 6.27-8.21 ppm corresponds to the chemical shift of aromatic hydrogen. The chemical shift from 4.69 ppm to 5.03 ppm corresponds to CH, while the chemical shift of 3.62 ppm is attributed to -OCH3. The chemical shift of NH is 5.43-5.81 ppm.

[0052] pass Figure 4 It can be seen that due to the steric hindrance of DOPO, 31 The phosphorus peak split into two signals near 28.27 ppm and 32.02 ppm in P-NMR, indicating the presence of phosphorus-containing phenyl groups.

[0053] The above analysis shows that an addition reaction occurs between the Schiff base intermediate and DOPO, and a vanillin-derived nitrogen-phosphorus synergistic flame retardant is successfully synthesized, as shown in Formula I:

[0054] Formula I.

[0055] Example 2

[0056] A method for preparing a vanillin-derived nitrogen-phosphorus synergistic flame retardant, comprising the following steps:

[0057] 1) First, in a reactor equipped with a stirrer, 30.43 g (0.2 mol) of vanillin was dispersed in 250 ml of methanol, and then 10.8 g (0.1 mol) of p-phenylenediamine dissolved in 100 ml of methanol was added into a constant pressure separation funnel with 4 ml of glacial acetic acid as a catalyst and 2 g of anhydrous magnesium sulfate as a water absorbent. Secondly, under nitrogen protection, the mixture was heated to 60 ° C, refluxed for 8 h, then cooled, poured into ice deionized water for precipitation, filtered, washed three times with methanol, and finally dried in vacuum at 80 ° C to obtain the intermediate Schiff base;

[0058] 2) Disperse 18.815 g (0.1 mol) of the intermediate Schiff base obtained in step 1) with 250 ml of methanol and stir mechanically in a three-hole flask; then add 21.6 g (0.2 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide dissolved in 100 ml of methanol. Under nitrogen protection, heat to 100 °C and reflux for 12 h, cool the mixture, pour it into ice deionized water for precipitation, filter it, wash it with methanol three times, and finally dry it in vacuum at 80 °C to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0059] Example 3

[0060] A method for preparing a vanillin-derived nitrogen-phosphorus synergistic flame retardant, comprising the following steps:

[0061] 1) First, in a reactor equipped with a stirrer, 15.22g (0.1 mol) of vanillin was dispersed in 150 ml of anhydrous ethanol, and then 5.4g (0.05 mol) of p-phenylenediamine dissolved in 50 ml of anhydrous ethanol was added into a constant pressure separation funnel using 4 ml of glacial acetic acid as a catalyst and 2 g of anhydrous magnesium sulfate as a water absorbent. Secondly, under nitrogen protection, the mixture was heated to 80°C, refluxed for 6 h, then cooled, poured into ice deionized water for precipitation, filtered, washed three times with methanol, and finally dried in vacuum at 80°C to obtain the intermediate Schiff base;

[0062] 2) 9.41 g (0.05 mol) of the intermediate Schiff base obtained in step 1) was dispersed in 150 ml of anhydrous ethanol and mechanically stirred in a three-hole flask; then 10.8 g (0.1 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide dissolved in 50 ml of anhydrous ethanol was added. Under nitrogen protection, the mixture was heated to 100 °C and refluxed for 8 h, then cooled and poured into ice deionized water for precipitation, filtered and washed with anhydrous ethanol for 3 times, and finally dried in vacuum at 90 °C to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0063] Example 4

[0064] A method for preparing a vanillin-derived nitrogen-phosphorus synergistic flame retardant, comprising the following steps:

[0065] 1) First, in a reactor equipped with a stirrer, 15.22 g (0.1 mol) of vanillin was dispersed with 150 ml of formic acid, and then 5.4 g (0.05 mol) of p-phenylenediamine dissolved in 50 ml of formic acid was added into a constant pressure separation funnel using 3 ml of glacial acetic acid as a catalyst and 2 g of anhydrous magnesium sulfate as a water absorbent. Secondly, under nitrogen protection, the mixture was heated to 60 ° C, refluxed for 8 h, then cooled, poured into ice deionized water for precipitation, filtered, washed three times with methanol, and finally dried in vacuum at 90 ° C to obtain the intermediate Schiff base;

[0066] 2) 9.41 g (0.05 mol) of the intermediate Schiff base obtained in step 1) was dispersed with 150 ml formic acid and mechanically stirred in a three-hole flask; then 10.8 g (0.1 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide dissolved with 50 ml formic acid was added. Under nitrogen protection, the mixture was heated to 80 °C and refluxed for 8 h, then cooled and poured into ice deionized water for precipitation, filtered and washed with formic acid 3 times, and finally dried in vacuum at 90 °C to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0067] Example 5

[0068] A method for preparing a vanillin-derived nitrogen-phosphorus synergistic flame retardant, comprising the following steps:

[0069] 1) First, in a reactor equipped with a stirrer, 30.43 g (0.2 mol) of vanillin was dispersed in 250 ml of anhydrous ethanol, and then 10.8 g (0.1 mol) of p-phenylenediamine dissolved in 100 ml of anhydrous ethanol was added into a constant pressure separation funnel using 3 ml of glacial acetic acid as a catalyst and 4 g of anhydrous magnesium sulfate as a water absorbent. Secondly, under nitrogen protection, the mixture was heated to 80°C, refluxed for 6 h, then cooled, poured into ice deionized water for precipitation, filtered, washed with anhydrous ethanol three times, and finally dried in vacuum at 80°C to obtain the intermediate Schiff base;

[0070] 2) Disperse 18.82 g (0.1 mol) of the intermediate Schiff base obtained in step 1) with 150 ml of anhydrous ethanol and stir mechanically in a three-hole flask; then add 21.6 g (0.2 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide dissolved in 100 ml of anhydrous ethanol. Under nitrogen protection, heat to 80 ° C and reflux for 8 h, cool the mixture, pour it into ice deionized water for precipitation, filter it, wash it with anhydrous ethanol for 3 times, and finally dry it in vacuum at 80 ° C to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0071] Example 6

[0072] A method for preparing a vanillin-derived nitrogen-phosphorus synergistic flame retardant, comprising the following steps:

[0073] 1) First, in a reactor equipped with a stirrer, 15.22 g (0.1 mol) of vanillin was dispersed in 150 ml of methanol, and then 5.4 g (0.05 mol) of p-phenylenediamine dissolved in 50 ml of methanol was added into a constant pressure separation funnel using 4 ml of glacial acetic acid as a catalyst and 4 g of anhydrous magnesium sulfate as a water absorbent. Secondly, under nitrogen protection, the mixture was heated to 60 ° C, refluxed for 6 h, then cooled, poured into ice deionized water for precipitation, filtered, washed three times with methanol, and finally dried in vacuum at 90 ° C to obtain the intermediate Schiff base;

[0074] 2) 9.41 g (0.05 mol) of the intermediate Schiff base obtained in step 1) was dispersed in 150 ml of methanol and mechanically stirred in a three-hole flask; then 10.8 g (0.1 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide dissolved in 50 ml of methanol was added. Under nitrogen protection, the mixture was heated to 80 °C and refluxed for 8 h, then cooled and poured into ice deionized water for precipitation, filtered and washed with methanol for 3 times, and finally dried in vacuum at 90 °C to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0075] Example 7

[0076] A method for preparing a vanillin-derived nitrogen-phosphorus synergistic flame retardant, comprising the following steps:

[0077] 1) First, in a reactor equipped with a stirrer, 30.43 g (0.2 mol) of vanillin was dispersed in 250 ml of propanol, and then 10.8 g (0.1 mol) of p-phenylenediamine dissolved in 100 ml of propanol was added into a constant pressure separation funnel using 4 ml of glacial acetic acid as a catalyst and 2 g of anhydrous magnesium sulfate as a water absorbent. Secondly, under nitrogen protection, the mixture was heated to 60 °C, refluxed for 8 h, then cooled, poured into ice deionized water for precipitation, filtered, washed with anhydrous ethanol three times, and finally dried in vacuum at 80 °C to obtain the intermediate Schiff base;

[0078] 2) Disperse 18.82 g (0.1 mol) of the intermediate Schiff base obtained in step 1) with 150 ml of propanol and stir mechanically in a three-hole flask; then add 21.6 g (0.2 mol) of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide dissolved in 100 ml of propanol. Under nitrogen protection, heat to 80 °C and reflux for 12 h, cool the mixture, pour it into ice deionized water for precipitation, filter it, wash it with propanol three times, and finally dry it in vacuum at 80 °C to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

[0079] The present invention also provides a flame-retardant composite material, which is prepared by compounding a matrix and raw materials of the vanillin-derived nitrogen-phosphorus synergistic flame retardant described in the present invention. The flame retardant prepared by the present invention can be added to the matrix, and the matrix is ​​one or more of TPU, PC, EP, and PET. The flame retardant properties of the matrix material can be improved while its mechanical properties are well maintained.

[0080] Example 8

[0081] A vanillin-derived nitrogen-phosphorus synergistic flame retardant obtained in Example 1-7 was added to TPU. The flame retardant and TPU were first premixed and then melt-blended in a mixer at 175°C and 60 rpm. Subsequently, the composite material was hot-pressed into target shapes of different measurements at 180°C and 10 MPa pressure using a hot press.

[0082] Example 8 is a further detailed description of the application of a vanillin-derived nitrogen-phosphorus synergistic flame retardant provided by the present invention, but the application of the flame retardant is not limited thereto.

[0083] The UL-94 grade of TPU and TPU composites was tested on a JF-3 oxygen index instrument according to GB / T2408-2021 standard, with a sample width of 13 mm and a thickness of 3.2 mm; the limiting oxygen index (LOI) value was tested on a 300,800 LOI instrument according to GB / T2406.2-2009 standard, with a sample width of 6.5 mm and a thickness of 3 mm; the mechanical test was carried out using an E42 universal mechanical testing machine from MTS, USA, in accordance with the requirements of GB / T528-2009.

[0084] The limiting oxygen index value, vertical burning test, breaking strength and breaking elongation results of the flame retardant flame retardant TPU material prepared in Example 1 are shown in Table 1.

[0085] Table 1 Test results

[0086]

[0087] It can be seen from Table 1 that when the addition amount of vanillin-derived nitrogen-phosphorus synergistic flame retardant is 2 wt.%, the vertical combustion test of the material can reach UL-94 V-0 level, and the limiting oxygen index increases from 20.2% to 25.1%. At the same time, the LOI values ​​of the flame-retardant modified thermoplastic polyurethane measured with different addition amounts (wt.%) of 2 wt.%, 4 wt.% and 6 wt.% flame retardants are 25.1%, 27.3% and 28.9%, respectively, indicating that the flame retardant effect is good and the LOI value is high. UL-94 can reach V-0 level and can be used as a flame retardant material for industrial production. In addition, the breaking strength of the flame-retardant thermoplastic polyurethane with an addition amount of 2 wt.% reaches 47.1 MPa, which is 12% higher than that of pure thermoplastic polyurethane. At the same time, the elongation at break reaches 1201%, indicating that the flame retardant has good compatibility with polymer materials such as thermoplastic polyurethane, and can still maintain good strength, toughness and processability after adding the flame retardant, which solves the problem of traditional flame retardants affecting the mechanical properties of thermoplastic polyurethane and meets the needs of practical applications.

[0088] The limiting oxygen index values ​​and vertical burning test results of the flame retardant flame retardant TPU materials prepared in Examples 1-7 are shown in Table 2.

[0089] Table 2 Test results

[0090]

[0091] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A vanillin-derived nitrogen-phosphorus synergistic flame retardant, characterized in that: The structural formula of the vanillin-derived nitrogen-phosphorus synergistic flame retardant is shown in Formula I: Formula I.

2. A method for preparing the vanillin-derived nitrogen-phosphorus synergistic flame retardant according to claim 1, characterized in that: The following steps are involved: 1) Mix vanillin, p-phenylenediamine, an organic solvent, a catalyst and a water absorbent to carry out an aldehyde-amine condensation reaction to obtain a Schiff base intermediate; 2) The Schiff base intermediate obtained in step 1) is mixed with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and an organic reagent to carry out an addition reaction to obtain a vanillin-derived nitrogen-phosphorus synergistic flame retardant.

3. The preparation method according to claim 2, characterized in that: In the step 1), the ratio of the mole of vanillin, the mole of p-phenylenediamine, the volume of the organic solvent, the catalyst and the water absorbent is 0.1-0.2 mol: 0.05-0.1 mol: 200-350 ml: 3-4 ml: 2-4 g.

4. The preparation method according to claim 2, characterized in that: The conditions of the step 1) aldehyde-amine condensation reaction include: temperature of 60-80° C. and time of 6-8 h.

5. The preparation method according to claim 2, characterized in that: The organic solvent includes one or more of anhydrous ethanol, methanol, formic acid and propanol.

6. The preparation method according to claim 2, characterized in that: The catalyst in step 1) includes glacial acetic acid, and the water absorbent includes anhydrous magnesium sulfate.

7. The preparation method according to claim 2, characterized in that: In the step 2), the volume ratio of the mole of the Schiff base intermediate to the mole of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and the organic reagent is 0.05-0.1 mol: 0.1-0.2 mol: 200-350 ml.

8. The preparation method according to claim 2, characterized in that: The conditions of the addition reaction in step 2) include: temperature of 80-100° C. and time of 8-12 h.

9. Use of the vanillin-derived nitrogen-phosphorus synergistic flame retardant according to claim 1 in reducing the amount of flame retardant and improving the flame retardant grade of polymer materials.

10. The use according to claim 9, characterized in that: The polymer material includes thermoplastic polyurethane and / or epoxy resin.

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