Vanillin-based flame retardant as well as preparation method and application thereof

Abstract

The invention discloses a vanillin-based flame retardant as well as a preparation method and application thereof, and belongs to the technical field of flame retardance. In the preparation process of the vanillin-based flame retardant, due to the fact that biomass raw material vanillin is selected to react with hexachlorocyclotriphosphazene containing nitrogen and phosphorus, nitrogen and phosphorus elements are introduced, PLA can be rapidly dehydrated and carbonized, oxygen and heat can be isolated, release of combustible gas and toxic smoke can be effectively reduced, and the flame retardant has the advantages of being high in flame retardant property, good in flame retardant property and the like. The flame retardant property of the PLA is improved. Meanwhile, benzoyl hydrazine is introduced, so that the flame retardant and the PLA can form an intermolecular force, and the mechanical property of the PLA is improved. In addition, dipole-dipole interaction is generated between imino groups in the flame retardant and carbonyl groups in PLA molecules, so that the crystallinity of PLA is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardancy and relates to a flame retardant applied to polymer materials, in particular to a vanillin-based flame retardant and a preparation method and application thereof. Background Art

[0002] Polymer materials have significantly promoted the convenience of daily life due to their wide range of applications. However, the flammable properties of these materials generally pose a major potential threat to human life and property safety. In order to improve the flame retardant properties of polymer materials, adding flame retardants has been proven to be the most effective strategy. However, the flame retardants currently used in polymer materials on the market often release a large amount of toxic smoke when burned, causing far-reaching adverse effects on the ecological environment. Some flame retardants even produce carcinogenic compounds during the combustion process. Based on this, the development of flame retardants with green, safe and environmentally friendly characteristics has become the mainstream trend of flame retardant scientific research and technology development at home and abroad.

[0003] Compared with flame retardants that rely on fossil raw materials for synthesis, flame retardants prepared using biomass materials as a matrix have shown more significant appeal. Bio-based flame retardants have attracted widespread attention and high attention from academia and industry due to their inherent sustainability, significant environmental friendliness and excellent flame retardant properties, and are considered to be one of the most promising and promising directions in the field of flame retardant research. Chinese patent CN 118460000A designs a polymer synergistic biomass flame retardant material, which contains: ammonium polyphosphate, pentaerythritol and keratin phytic acid biomass, which can effectively improve the smoke density and oxygen index of epoxy resin flame retardant properties. Chinese patent CN 115403674 A uses agricultural waste peanut shells as raw materials, adds concentrated sulfuric acid to carbonize, dries and grinds them into powder, and then reacts with epichlorohydrin, and then adds aminosiloxane and 9,10-dihydro-9,10-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to obtain a biomass-based multi-element synergistic enhanced flame retardant containing phosphorus, nitrogen and silicon.

[0004] Obviously, using biomass as raw material to prepare flame retardants is in line with the core concepts of safety, environmental protection and sustainable development. However, the current preparation process of biomass flame retardants generally faces the challenge of complexity, and most of the biomass flame retardants produced have shortcomings such as poor mechanical properties and poor flame retardant properties in polymers, which makes it difficult to meet the requirements of flame retardant additives in processing or practical applications. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of existing biomass flame retardants such as complex preparation process, low flame retardant efficiency, poor mechanical properties, etc., and a vanillin-based flame retardant and its preparation method and application are proposed.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] First, the present invention proposes a vanillin-based flame retardant, and its molecular structural formula is:

[0008]

[0009] Secondly, the present invention also proposes a preparation method of the vanillin-based flame retardant, which is divided into two steps: In the first step, vanillin is dissolved in an organic solvent, an organic base and an inorganic base are added, and then hexachlorocyclotriphosphazene is added dropwise. After the addition is completed, the mixture is heated for reaction. After the reaction is completed, the obtained product is filtered and precipitated, the solvent is removed, and the target product 1 with the following molecular structural formula is obtained after purification and drying; In the second step, the target product 1 is dissolved in an organic solvent, benzoyl hydrazide is added, and the mixture is heated for reaction. After the reaction is completed, the obtained product is filtered and precipitated, the solvent is removed, and finally the target product 2, that is, the vanillin-based flame retardant, is obtained after purification and drying;

[0010]

[0011] As a preferred technical solution of the present invention, in the preparation method:

[0012] In the first-step reaction, the molar ratio of vanillin, hexachlorocyclotriphosphazene, inorganic base, and organic base is 1:6-9:6-9:6-9; in the second-step reaction, the molar ratio of the target product 1 to benzoyl hydrazide is 1:6-9. The inorganic base is anhydrous potassium carbonate, the organic base is triethylamine, and the organic solvent is tetrahydrofuran, dichloromethane or ethyl acetate. The dropwise addition of hexachlorocyclotriphosphazene is carried out at room temperature, and after the addition is completed, the temperature is raised to 60-80 °C and the reaction continues for 24-48 h; the dropwise addition of hexachlorocyclotriphosphazene and the temperature-raising reaction are both carried out under nitrogen protection.

[0013] In the second-step reaction, the reaction temperature is 30-50 °C, and the reaction time is 12-24 h; the addition of benzoyl hydrazide and the temperature-raising reaction are both carried out under nitrogen protection.

[0014] Finally, the present invention also proposes an application of the vanillin-based flame retardant as a flame retardant in polymer materials.

[0015] As a preferred technical solution of the present invention, the polymer material is polylactic acid, and the addition amount of the vanillin-based flame retardant in polylactic acid is 1%-3% by mass percentage.

[0016] Compared with the prior art, the beneficial effects of the present invention are shown in:

[0017] (1) The vanillin-based flame retardant prepared by the present invention is obtained by reacting the biomass raw material vanillin with hexachlorocyclotriphosphazene containing nitrogen and phosphorus. It has a high phosphorus content and many benzene ring structures, enabling the composite material to rapidly promote polymer carbonization during heating or combustion, isolate oxygen and heat, reduce the release of combustible gases and toxic fumes, and improve the flame retardancy of the composite material.

[0018] (2) During the preparation process of the present invention, benzoyl hydrazide is introduced, enabling the flame retardant to form intermolecular forces with polylactic acid (PLA), thereby improving the mechanical properties of PLA. In addition, a dipole-dipole interaction occurs between the imino group in the flame retardant and the carbonyl group in the PLA molecule, increasing the crystallinity of PLA.

[0019] (3) The vanillin-based flame retardant proposed by the present invention is prepared from biomass resources, conforms to the concept of green and sustainable development, has a simple preparation method, is applicable to most polymer materials, and has broad market application prospects. Description of the Drawings

[0020] Figure 1 1H NMR spectra of target product 1(a) and target product 2(b) prepared in Example 1.

[0021] Figure 2 13C NMR spectra of target product 1(a) and target product 2(b) prepared in Example 1.

[0022] Figure 3 31P NMR spectra of target product 1(a) and target product 2(b) prepared in Example 1.

[0023] Figure 4 Mechanical property diagrams of various PLA composite materials obtained based on target product 2 prepared in Example 1.

[0024] Figure 5 Combustion test diagrams of various PLA composite materials obtained based on target product 2 prepared in Example 1. Detailed Description of the Invention

[0025] The following further details the present invention in combination with examples and drawings.

[0026] Example 1

[0027] In the first-step reaction, vanillin (19.7 g), anhydrous potassium carbonate (17.89 g) and 20 mL of triethylamine (TEA) were dissolved in 300 mL of tetrahydrofuran (THF), and then hexachlorocyclotriphosphazene (5 g) was dissolved in 50 mL of tetrahydrofuran (THF) and added dropwise under a nitrogen atmosphere. After the addition was completed, the solution was transferred to an oil bath at 70 °C and reacted for 48 h. Finally, the solution was filtered, the solvent was removed by a rotary evaporator, purified and dried to obtain a white powder, which was the target product 1 with a yield of 80%.

[0028] In the second-step reaction, the target product 1 (2 g) and benzoyl hydrazide (2.35 g) were dissolved in 100 mL of tetrahydrofuran (THF). Under a nitrogen atmosphere, the temperature was 45 °C and the reaction time was 24 h. After the reaction was completed, the solution was filtered and the solvent was removed by a rotary evaporator. Finally, it was washed three times with dichloromethane and vacuum dried at 60 °C for 24 h to obtain a white powder, which was the target product 2 - vanillin-based flame retardant, named HVB, with a yield of 80%.

[0029] Figure 1 (a) is the 1H NMR spectrum of the target product 1 prepared in Example 1 1 1H NMR (400 MHz, CDCl 3 , ppm), and the specific analysis is as follows: δ = 3.76 (s, 18H), 7.23 (dd, 6H), 7.32 (d, 12H), 9.84 (s, 6H). Figure 1 (b) is the 1H NMR spectrum of the target product 2 prepared in Example 1 1 1H NMR (400 MHz, DMSO, ppm), and the specific analysis is as follows: δ = 3.79 (s, 18H), 7.09 - 7.91 (m, 48H), 8.47 (s, 6H), 11.92 (s, 6H).

[0030] Figure 2 (a) is the 13C NMR spectrum of the target product 1 prepared in Example 1 13 13C NMR (100 MHz, CDCl 3 , ppm), and the specific analysis is as follows: δ = 190.8, 151.42, 144.69, 133.88, 124.2, 121.66, 110.81, 55.88. Figure 2 (b) is the 13C NMR spectrum of the target product 2 prepared in Example 1 13 13C NMR (100 MHz, DMSO, ppm), and the specific analysis is as follows: δ = 163.36, 150.65, 147.6, 140.7, 133.39, 132.02, 131.87, 128.51, 127.76, 120.94, 120.48, 110.03, 55.8.

[0031] Figure 3 (a) \(^{31}\)P NMR spectrum of the target product 1 prepared in Example 1 31 \(^{31}\)P NMR (162 MHz, CDCl 3 , ppm), and the specific analysis is as follows: δ = 7.71. Figure 3 (b) \(^{31}\)P NMR spectrum of the target product 2 prepared in Example 1 31 \(^{31}\)P NMR (162 MHz, CDCl 3 , ppm), and the specific analysis is as follows: δ = 8.74.

[0032] Example 2

[0033] In the first step of the reaction, first dissolve vanillin (17.51 g), anhydrous potassium carbonate (15.9 g) and 20 mL of triethylamine (TEA) in 300 mL of tetrahydrofuran (THF), then dissolve hexachlorocyclotriphosphazene (5 g) in 50 mL of tetrahydrofuran (THF) and add it dropwise under a nitrogen atmosphere. After the dropwise addition is completed, transfer the solution to an oil bath at 60 °C and react for 36 h. Finally, filter the solution, remove the solvent with a rotary evaporator, purify and dry it to obtain a white powder, which is the target product 1 with a yield of 78%.

[0034] In the second step of the reaction, dissolve the target product 1 (2 g) and benzoyl hydrazide (2.09 g) in 100 mL of tetrahydrofuran (THF), and react at 40 °C for 12 h under a nitrogen atmosphere. After the reaction is completed, filter the solution and remove the solvent with a rotary evaporator. Finally, wash it three times with dichloromethane and dry it in vacuo at 60 °C for 24 h to obtain a white powder, which is the target product 2 - vanillin-based flame retardant, named HVB, with a yield of 78%.

[0035] Example 3

[0036] In the first step of the reaction, first dissolve vanillin (15.32 g), anhydrous potassium carbonate (13.91 g) and 20 mL of triethylamine (TEA) in 300 mL of tetrahydrofuran (THF), then dissolve hexachlorocyclotriphosphazene (5 g) in 50 mL of tetrahydrofuran (THF) and add it dropwise under a nitrogen atmosphere. After the dropwise addition is completed, transfer the solution to an oil bath at 80 °C and react for 24 h. Finally, filter the solution, remove the solvent with a rotary evaporator, purify and dry it to obtain a white powder, which is the target product 1 with a yield of 79%.

[0037] Second step reaction: Dissolve the target product 1 (2 g) and benzoyl hydrazide (1.83 g) in 100 mL of tetrahydrofuran (THF). Under a nitrogen atmosphere, at a temperature of 50 °C, react for 18 h. After the reaction is completed, filter the solution and remove the solvent using a rotary evaporator. Finally, wash three times with dichloromethane and dry in vacuo at 60 °C for 24 h to obtain a white powder, namely the target product 2 - vanillin-based flame retardant, named HVB, with a yield of 79%.

[0038] Example 4

[0039] First step reaction: First, dissolve vanillin (14.22 g), anhydrous potassium carbonate (12.92 g) and 25 mL of triethylamine (TEA) in 300 mL of tetrahydrofuran (THF). Then dissolve hexachlorocyclotriphosphazene (5 g) in 50 mL of tetrahydrofuran (THF) and add dropwise under a nitrogen atmosphere. After the dropwise addition is completed, transfer the solution to an 80 °C oil bath and react for 24 h. Finally, filter the solution, remove the solvent using a rotary evaporator, purify and dry to obtain a white powder, namely the target product 1, with a yield of 77%.

[0040] Second step reaction: Dissolve the target product 1 (2 g) and benzoyl hydrazide (1.7 g) in 100 mL of tetrahydrofuran (THF). Under a nitrogen atmosphere, at a temperature of 40 °C, react for 24 h. After the reaction is completed, filter the solution and remove the solvent using a rotary evaporator. Finally, wash three times with dichloromethane and dry in vacuo at 60 °C for 24 h to obtain a white powder, namely the target product 2 - vanillin-based flame retardant, named HVB, with a yield of 77%.

[0041] Example 5

[0042] Take 0.3 g of the vanillin-based flame retardant prepared in Example 1 and 29.7 g of polylactic acid, and prepare a biocomposite material by a melt blending process. Blend for about 20 min using a torque rheometer at 190 °C and a rotation speed of 50 r / min. Then use a flat vulcanizing machine to hot press at 190 °C and 30 MPa to prepare samples of different sizes for different performance tests. The prepared composite material is named PLA / 1HVB (the mass percentage of the vanillin-based flame retardant in the composite material is 1%).

[0043] Example 6

[0044] Take 0.6 g of the vanillin-based flame retardant prepared in Example 1 and 29.4 g of polylactic acid, and prepare a biocomposite material by a melt blending process. Blend for about 20 min using a torque rheometer at 190 °C and a rotation speed of 50 r / min. Then use a flat vulcanizing machine to hot press at 190 °C and 30 MPa to prepare samples of different sizes for different performance tests. The prepared composite material is named PLA / 2HVB (the mass percentage of the vanillin-based flame retardant in the composite material is 2%).

[0045] Example 7

[0046] Take 0.9 g of the vanillin-based flame retardant prepared in Example 1 and 29.1 g of polylactic acid, and prepare a biocomposite by melt blending process. Blend for about 20 min at 190 °C and 50 r / min using a torque rheometer. Then, hot press at 190 °C and 30 MPa using a flat vulcanizer to prepare samples of different sizes for different property tests. The prepared composite is named PLA / 3HVB (the mass percentage of the vanillin-based flame retardant in the composite is 3%).

[0047] Comparative Example 1

[0048] Take 30 g of polylactic acid and prepare a biocomposite by melt blending process. Blend for about 20 min at 190 °C and 50 r / min using a torque rheometer. Then, hot press at 190 °C and 30 MPa using a flat vulcanizer to prepare samples of different sizes for different property tests. The prepared composite is named PLA.

[0049] Performance tests of the composites prepared in Examples 5 - 7 and Comparative Example 1:

[0050] Figure 4 It is the mechanical property diagram of various PLA composites obtained based on the preparation of Target Product 2 in Example 1. The specific analysis is as follows: The maximum tensile strength and elongation at break of PLA are 59.4 MPa and 9.1% respectively. Compared with PLA, when adding HVB with a mass percentage of 3%, the maximum tensile strength and elongation at break increase by 3.4% and 75.8% respectively.

[0051] Figure 5 It is the UL-94 vertical burning test diagram of various PLA composites obtained based on the preparation of Target Product 2 in Example 1. The specific analysis is as follows: Pure PLA will show obvious dripping phenomenon and ignite the cotton fiber, while after adding HVB with a mass percentage of 3%, the cotton fiber is not ignited and reaches the UL-94 V-0 flame retardant grade.

[0052] Table 1

[0053]

[0054] Table 1 shows the DSC data of various PLA composites obtained based on the preparation of Target Product 2 in Example 1. The specific analysis is as follows: With the addition of HVB, the crystallinity of PLA increases from 4.39% to 17.70% (when adding HVB with a mass percentage of 3%).

[0055] From the mechanical diagrams and combustion tests of Examples 5 to 7 and Comparative Example 1, it can be seen that adding 3% by mass of the vanillin-based flame retardant prepared by the present invention can significantly improve the mechanical properties of polylactic acid, and the flame retardant properties are also significantly improved. That is to say, using the flame retardant of the present invention to modify polylactic acid can endow it with excellent mechanical properties and flame retardant properties.

[0056] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of the present technology can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all fall within the protection scope of the present invention.

Claims

1. A vanillin-based flame retardant, characterized in that Its molecular structure is:

2. A method for preparing the vanillin-based flame retardant according to claim 1, characterized in that: The method is divided into two steps. In the first step, vanillin is dissolved in an organic solvent, an organic base and an inorganic base are added, and then hexachlorocyclotriphosphazene is added dropwise. After the addition is completed, the reaction is heated. After the reaction is completed, the obtained product is filtered and precipitated, the solvent is removed, and the target product 1 with a molecular structure shown in the following formula is obtained through purification and drying. In the second step, the target product 1 is dissolved in an organic solvent, benzoyl hydrazide is added, and the reaction is heated. After the reaction is completed, the obtained product is filtered and precipitated, the solvent is removed, and finally the target product 2, i.e., the vanillin-based flame retardant, is obtained through purification and drying.

3. The method according to claim 2, characterized in that The molar ratio of vanillin, hexachlorocyclotriphosphazene, inorganic base and organic base in the first step reaction is 1:6-9:6-9:6-9; the molar ratio of the target product 1 and benzohydrazide in the second step reaction is 1:6-9.

4. The method according to claim 2 or 3, characterized in that In the first step reaction, the inorganic base is anhydrous potassium carbonate, the organic base is triethylamine, and the organic solvent is tetrahydrofuran, dichloromethane or ethyl acetate.

5. The method according to claim 2, characterized in that In the first step of the reaction, the hexachlorocyclotriphosphazene is added dropwise at room temperature. After the addition is completed, the temperature is raised to 60-80°C and the reaction is continued for 24-48 hours. The hexachlorocyclotriphosphazene is added dropwise and the temperature is raised under nitrogen protection.

6. The method according to claim 2, characterized in that In the second step, the reaction temperature is 30-50°C and the reaction time is 12-24h; the addition of benzoyl hydrazide and the temperature increase reaction are both carried out under nitrogen protection.

7. Use of the vanillin-based flame retardant as claimed in claim 1 as a flame retardant for polymer materials.

8. The use according to claim 7, characterized in that The polymer material is polylactic acid, and the amount of the vanillin-based flame retardant added to the polylactic acid is 1% to 3% by mass.

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