A modified lignin-coated red phosphorus flame retardant and its preparation method and application

Abstract

The present invention relates to a modified lignin-coated red phosphorus flame retardant, its preparation method and application. Lignin is dissolved in an organic solvent, and cyanuric chloride, aluminum chloride and an acid-binding agent are added for reaction; after the reaction is completed, red phosphorus and a dispersant are added and stirred for reaction, the solvent is distilled off by reduced pressure distillation, the residue is washed, dried, pulverized and sieved to obtain the modified lignin-coated red phosphorus flame retardant. The flame retardant prepared by the present invention is used for modifying and processing high molecular polymers such as polypropylene and ABS, and has the advantages of good compatibility with the matrix, not being prone to leakage after combustion, and good flame retardancy.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass utilization, and particularly relates to a modified lignin-coated red phosphorus flame retardant, a preparation method thereof, and an application thereof. Background Art

[0002] Polymers such as polypropylene and ABS are widely used due to their good chemical stability, easy processing, and excellent mechanical properties. However, most polymers have a fatal weakness, that is, they are extremely flammable in a fire and will release a large amount of thick smoke or toxic smoke during combustion, seriously threatening people's safety. Therefore, it is crucial to research and develop high-performance flame retardants to reduce flammability and inhibit the thick smoke or toxic smoke generated by polymers after ignition.

[0003] Red phosphorus flame retardant is a halogen-free flame retardant, which has advantages such as good flame retardant effect, thermal stability, non-volatility, non-generation of corrosive and irritating gases, insolubility during use, high melting point, low toxicity, low addition amount, and high flame retardant efficiency. However, red phosphorus will generate highly toxic phosphine in a high-temperature environment and has poor compatibility with polymer materials, which greatly limits the application of red phosphorus.

[0004] CN201711100084.6 discloses a red phosphorus flame retardant masterbatch, comprising: 70-300 parts of red phosphorus, 4-6 parts of magnesium hydroxide, 9-11 parts of aluminum hydroxide, 0.3 part of dispersant, 8-12 parts of carrier agent, 10-20 parts of talcum powder, and 5-10 parts of phenol resin. The proportion of the flame retardant material added to the flame retardant plastic reduces the influence of the components of the flame retardant masterbatch material on the performance of the flame retardant plastic. The invention also discloses a manufacturing method of the red phosphorus flame retardant masterbatch, adding POE, EVA, and coupling agent to a mixer for premixing treatment; adding to a screw extruder for mixing, heating, and extruding to make a carrier agent; wet-treating red phosphorus; mixing red phosphorus, magnesium hydroxide, aluminum hydroxide, talcum powder, dispersant, and carrier agent; processing with a screw extruder, and then hot-cutting, throwing out, air-cooling, and granulating the extruded material with a hot-cut air-cooling granulator to make a red phosphorus flame retardant masterbatch. The manufacturing method of this red phosphorus flame retardant masterbatch makes a flaky oval or flaky melon-seed-shaped red phosphorus flame retardant masterbatch, and the red phosphorus content in the red phosphorus flame retardant masterbatch is between 60% and 90%. This method uses simple physical blending method and inorganic materials such as red phosphorus and magnesium hydroxide, reducing the compatibility with the polymer matrix and the mechanical properties of the material.

[0005] Lignin has a three-dimensional network structure and a dense carbon layer will be formed during the combustion process. CN201810899984.X discloses a melamine-modified lignin-coated red phosphorus flame retardant and its application in ABS resin. It mainly uses lignin, aldehyde, melamine, red phosphorus, dispersant, etc. as raw materials, and combines the Mannich reaction and the chemical co-precipitation method to prepare the melamine-modified lignin-coated red phosphorus flame retardant. The melamine-modified lignin-coated red phosphorus flame retardant of this invention can significantly improve the surface properties and instability of red phosphorus, and enhance its compatibility with polymer materials. When this flame retardant is applied in ABS resin, it has a good flame retardant effect, and the lignin used is a renewable biomass material, which is cheap and easily available. However, in the process of lignin modification in this invention, it is necessary to hydroxymethylate lignin with alkali and aldehyde and then react with melamine, and the reaction process is complex. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a modified lignin-coated red phosphorus flame retardant, its preparation method and application. The flame retardant prepared by the present invention has the advantages of good compatibility with the matrix, good flame retardancy and good thermal stability.

[0007] A preparation method of a modified lignin-coated red phosphorus flame retardant provided by the present invention includes the following steps:

[0008] (1) Dissolve lignin in an organic solvent, add cyanuric chloride, aluminum chloride and a deacidifying agent for reaction;

[0009] (2) After the reaction is completed, add red phosphorus and a dispersant and stir for reaction. Evaporate the solvent by reduced pressure distillation, wash, dry the residue, crush and sieve to obtain the modified lignin-coated red phosphorus flame retardant.

[0010] In the above method, the lignin in step (1) is at least one of alkali lignin, enzymatically hydrolyzed lignin, lignin sulfonate, etc., and alkali lignin is preferred.

[0011] In the above method, the organic solvent in step (1) is at least one of aprotic polar solvents, specifically it can be at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, acetonitrile, etc., and N,N-dimethylformamide is preferred.

[0012] In the above method, the solid-liquid ratio of the lignin to the organic solvent in step (1) is 1g:1-5mL, and 1g:1.5-3mL is preferred.

[0013] In the above method, the mass ratio of the lignin, aluminum chloride and cyanuric chloride in step (1) is 1:0.01-0.1:0.5-1.5.

[0014] In the above method, the acid-binding agent in step (1) is at least one of triethanolamine, sodium carbonate, potassium carbonate, etc., and triethanolamine is preferred.

[0015] In the above method, the mass ratio of the acid-binding agent to cyanuric chloride in step (1) is 0.4 - 1:1.

[0016] In the above method, the reaction temperature in step (1) is 60 - 120 °C, preferably 80 - 100 °C, and the reaction time is 1 - 8 h, preferably 2 - 5 h.

[0017] In the above method, the mass ratio of red phosphorus to lignin in step (2) is 1:0.2 - 1, preferably 1:0.4 - 0.8.

[0018] In the above method, the dispersant in step (2) is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl phosphate, etc., and sodium dodecylbenzenesulfonate is preferred.

[0019] In the above method, the mass ratio of red phosphorus to the dispersant in step (2) is 1:0.01 - 0.08, preferably 1:0.05 - 0.06.

[0020] In the above method, the stirring reaction time at room temperature in step (2) is 0.5 - 1 h, and the stirring speed is 200 - 400 rpm.

[0021] In the above method, the pressure of the vacuum distillation in step (2) is 5 - 20 kPa, and the temperature is 50 - 70 °C.

[0022] In the above method, the washing in step (2) is to wash with water until the pH value is 6 - 7, and then dry at 60 - 80 °C for 8 - 12 h.

[0023] In the above method, the crushing and sieving in step (2) is to crush to 200 - 250 mesh, and conventional methods such as mechanical crushing can be used.

[0024] The modified lignin-coated red phosphorus flame retardant described in the present invention is prepared by the above method of the present invention. After testing, the red phosphorus coating rate can reach more than 95%.

[0025] The flame retardant prepared by the present invention is used for modifying and processing high molecular polymers such as polypropylene and ABS, and the dosage of the flame retardant is 10% - 25% of the mass of the polymer.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1)In the presence of an organic solvent, aluminum chloride, and a base, cyanuric chloride is used to modify lignin, and the two form a cross-linked network structure, which can better coat red phosphorus. The prepared flame retardant has the advantages of good compatibility with the matrix, good mechanical properties, no leakage after combustion, and good flame retardancy.

[0028] (2)The cyanuric chloride-modified lignin introduces a triazine ring structure. The triazine ring structure has excellent thermodynamic properties and stability, and a high nitrogen element content. After modification, the molecular thermodynamic properties are improved.

[0029] (3)When cyanuric chloride is used to modify lignin, an aprotic polar solvent is used, which is easy to form a stable cross-linked network structure, so as to maintain good mechanical properties and avoid leakage and dripping during combustion.

[0030] (4)The present invention has the advantages of simple preparation process, low cost, stable performance, and environmental friendliness. Detailed Embodiments

[0031] The method of the present invention and its effects will be further described below through examples. The examples are implemented on the premise of the technical solution of the present invention, and the detailed implementation methods and specific operation processes are given. However, the protection scope of the present invention is not limited to the following examples.

[0032] The experimental methods in the following examples are all conventional methods in the art unless otherwise specified. The experimental materials used in the following examples can be obtained from biochemical reagent stores unless otherwise specified.

[0033] In the present invention, the limiting oxygen index is measured by an HC-2 oxygen index tester of Nanjing Jiangning Analytical Instrument Factory in accordance with GB / T 2406. The tensile strength is tested by a CMT4304 microcomputer-controlled electronic universal testing machine of MTS Industrial Systems Co., Ltd. The surface coating rate of red phosphorus is calculated through the sensitivity factor of the XPS spectrum. The thermal performance analysis is carried out using a NETZSCH STA 449F3 TGA thermogravimetric analyzer, NETZSCH, Germany.

[0034] Example 1

[0035] (1)Add 5 g of alkali lignin to a reaction flask, add 7.5 mL of N,N-dimethylformamide, and stir until completely dissolved. Add 0.1 g of aluminum chloride, 4 g of cyanuric chloride, and 2.4 g of triethanolamine, and react at 100 °C for 3 hours.

[0036] (2) Add 8.3 g of red phosphorus and 0.4 g of sodium dodecyl sulfonate into the reaction flask, stir and react at room temperature for 30 min, with a stirring speed of 300 rpm. After the reaction, distill off the solvent under reduced pressure at 10 kPa and 55 °C for recovery. Wash the residue with water until the pH reaches 6.5, dry it at 70 °C for 10 h, and pulverize it to 200 mesh to obtain the modified lignin-coated red phosphorus flame retardant. The generated crosslinked network structure is shown as follows. The surface coating rate of red phosphorus is shown in Table 1.

[0037]

[0038] Blend the above-prepared modified lignin-coated red phosphorus flame retardant with polypropylene masterbatch at a mass ratio of 20% and 80%, and extrude to prepare flame-retardant polypropylene. The performance test results of the prepared flame-retardant polypropylene are shown in Table 1.

[0039] Example 2

[0040] (1) Add 5 g of alkali lignin into the reaction flask, add 5 mL of N,N-dimethylformamide, and stir until completely dissolved. Add 0.05 g of aluminum chloride, 2.5 g of cyanuric chloride, and 0.1 g of triethanolamine, and react at 60 °C for 5 h.

[0041] (2) Add 5 g of red phosphorus and 0.1 g of sodium dodecyl sulfonate into the reaction flask, stir and react at room temperature for 30 min, with a stirring speed of 200 rpm. After the reaction, distill off the solvent under reduced pressure at 10 kPa and 55 °C for recovery. Wash the residue with water until the pH reaches 6.5, dry it at 70 °C for 10 h, and pulverize it to 200 mesh to obtain the modified lignin-coated red phosphorus flame retardant. The generated crosslinked network structure is shown as follows. The surface coating rate of red phosphorus is shown in Table 1.

[0042] Blend the above-prepared modified lignin-coated red phosphorus flame retardant with polypropylene masterbatch at a mass ratio of 20% and 80%, and extrude to prepare flame-retardant polypropylene. The performance test results of the prepared flame-retardant polypropylene are shown in Table 1.

[0043] Example 3

[0044] (1) Add 5 g of alkali lignin into the reaction flask, add 25 mL of N,N-dimethylformamide, and stir until completely dissolved. Add 0.5 g of aluminum chloride, 5 g of cyanuric chloride, and 5 g of triethanolamine, and react at 120 °C for 2 h.

[0045] (2) Add 5 g of red phosphorus and 0.4 g of sodium dodecyl sulfonate into the reaction flask, stir and react at room temperature for 1 h with a stirring speed of 400 rpm. After the reaction, distill off the solvent under reduced pressure at 10 kPa and 55 °C for recovery. Wash the residue with water until the pH reaches 7.0, dry it at 70 °C for 10 h, and pulverize it to 250 mesh to obtain the modified lignin-coated red phosphorus flame retardant. The generated cross-linked network structure is shown in the figure below. The surface coating rate of red phosphorus is shown in Table 1.

[0046] Mix the above-prepared modified lignin-coated red phosphorus flame retardant with polypropylene masterbatch at a mass ratio of 20% and 80%, and extrude to prepare flame-retardant polypropylene. The performance test results of the prepared flame-retardant polypropylene are shown in Table 1.

[0047] Example 4

[0048] Same as Example 1, except that: lignin is sodium lignosulfonate. The test results are shown in Table 1.

[0049] Example 5

[0050] Same as Example 1, except that: the organic solvent is dimethyl sulfoxide. The test results are shown in Table 1.

[0051] Example 6

[0052] Same as Example 1, except that: the organic solvent is acetone. The test results are shown in Table 1.

[0053] Example 7

[0054] Same as Example 1, except that: the acid-binding agent is sodium carbonate. The test results are shown in Table 1.

[0055] Example 8

[0056] Same as Example 1, except that: the dispersant is sodium dodecyl sulfate. The test results are shown in Table 1.

[0057] Comparative Example 1

[0058] Same as Example 1, except that: the organic solvent is diethyl ether. The test results are shown in Table 1.

[0059] Comparative Example 2

[0060] Same as Example 1, except that: the organic solvent is ethanol. The test results are shown in Table 1.

[0061] Comparative Example 3

[0062] Same as Example 1, except that: cyanuric chloride is not used. The test results are shown in Table 1.

[0063] Comparative Example 4

[0064] Same as Example 1, except that: melamine is used instead of cyanuric chloride. The test results are shown in Table 1.

[0065] Comparative Example 5

[0066] Same as Example 1, except that: sodium hydroxide is used as the catalyst. The test results are shown in Table 1.

[0067] Comparative Example 6

[0068] Same as Example 1, except that: no acid-binding agent is used. The test results are shown in Table 1.

[0069] Table 1 Performance test results of flame retardants and polypropylene prepared in each example and comparative example

[0070]

[0071] As can be seen from Table 1, the modified lignin-coated red phosphorus flame retardant prepared by the method of the present invention is used to prepare polypropylene, and the comprehensive performance is better than that of the flame-retardant red phosphorus polypropylene not prepared by the method of the present invention. If a certain substance in the preparation method of the present invention is missing, the comprehensive performance is not ideal.

Claims

1. A preparation method of a modified lignin-coated red phosphorus flame retardant, characterized in that it comprises the following steps: (1) Dissolve lignin in an organic solvent, add cyanuric chloride, aluminum chloride and a deacidifying agent for reaction; the organic solvent is at least one of N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, acetone, and acetonitrile; the mass ratio of the lignin, aluminum chloride and cyanuric chloride is 1:0.01-0.1:0.5-1.5; the deacidifying agent is at least one of triethanolamine, sodium carbonate, and potassium carbonate; the mass ratio of the deacidifying agent and cyanuric chloride is 0.4-1:1; (2) After the reaction is completed, add red phosphorus and a dispersant and stir for reaction. The mass ratio of the red phosphorus to the lignin is 1:0.2-1, and the mass ratio of the red phosphorus to the dispersant is 1:0.01-0.08; Distill off the solvent by vacuum distillation, wash, dry, pulverize and sieve the residue to obtain the modified lignin-coated red phosphorus flame retardant.

2. The method according to claim 1, characterized in that: The lignin in step (1) is at least one of alkali lignin, enzymatically hydrolyzed lignin, and lignin sulfonate.

3. The method according to claim 2, characterized in that: The lignin in step (1) is alkali lignin.

4. The method according to claim 1, characterized in that: The organic solvent in step (1) is N,N-dimethylformamide.

5. The method according to claim 1 or 2 or 3 or 4, characterized in that: The solid-liquid ratio of the lignin to the organic solvent in step (1) is 1 g:1-5 mL.

6. The method according to claim 5, characterized in that: The solid-liquid ratio of the lignin to the organic solvent in step (1) is 1 g:1.5-3 mL.

7. The method according to claim 1, characterized in that: The deacidifying agent in step (1) is triethanolamine.

8. The method according to claim 1, characterized in that: The reaction temperature in step (1) is 60-120 °C, and the reaction time is 1-8 h.

9. The method according to claim 8, characterized in that: The reaction temperature in step (1) is 80-100 °C, and the reaction time is 2-5 hours.

10. The method according to claim 1, characterized in that: The mass ratio of the red phosphorus to the lignin in step (2) is 1:0.4-0.

8.

11. The method according to claim 1, characterized in that: The dispersant in step (2) is at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium dodecyl phosphate.

12. The method according to claim 11, characterized in that: The dispersant in step (2) is sodium dodecylbenzenesulfonate.

13. The method according to claim 1 or 11 or 12, characterized in that: The mass ratio of the red phosphorus to the dispersant in step (2) is 1:0.05-0.

06.

14. The method according to claim 1, characterized in that: In step (2), the stirring reaction time at room temperature is 0.5-1 h, and the stirring speed is 200-400 rpm.

15. The method according to claim 1, characterized in that: the pressure of the vacuum distillation described in step (2) is 5 - 20 kPa, and the temperature is 50 - 70 °C.

16. The method according to claim 1, characterized in that: the washing described in step (2) is water washing until the pH value is 6 - 7, and then drying at 60 - 80 °C for 8 - 12 h.

17. The method according to claim 1, characterized in that: the crushing and sieving described in step (2) is crushing to 200 - 250 mesh.

18. A modified lignin-coated red phosphorus flame retardant, characterized in that: it is prepared by the method according to any one of claims 1 - 17.

19. An application of the flame retardant according to claim 18, characterized in that: it is used for modifying and processing polypropylene and / or ABS polymers, and the dosage of the flame retardant is 10% - 25% of the mass of the polymer.

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