Method for preparing lignin-based flame retardant containing nitrogen and phosphorus by one-pot method and application of lignin-based flame retardant in polyamide

Abstract

The invention relates to a lignin-based flame retardant, in particular to a method for preparing a lignin-based flame retardant containing nitrogen and phosphorus through a one-pot method, the flame retardant and application of the flame retardant in polyamide, and the method comprises the steps that cyanuric chloride and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide react in an N, N-dimethylformamide solution, and an intermediate TD is obtained; and reacting the intermediate TD with hydroxyl-containing lignin in an N, N-dimethylformamide solution to prepare the lignin-based flame retardant containing nitrogen and phosphorus. Under the synergistic effect of the three components, the optimal flame-retardant effect is achieved. Compared with a traditional flame retardant, the cost of the flame retardant is greatly reduced due to the addition of lignin. When the lignin-based flame retardant prepared by the method is applied to polyamide, a low-cost flame-retardant polyamide material with excellent performance can be obtained.

Description

Technical Field

[0001] The invention relates to a lignin-based flame retardant, in particular to a one-pot method for preparing a nitrogen- and phosphorus-containing lignin-based flame retardant and application thereof in polyamide. Background Art

[0002] Lignin is a biodegradable natural polymer with abundant reserves and high yield, but low utilization rate. Industrial lignin mainly comes from papermaking waste liquid and biorefining industry, but only 2% of lignin is commercially used in plastics and rubber. The rest of lignin is mostly discharged into rivers in the form of waste liquid or burned after concentration, resulting in waste of resources and serious pollution to the environment. Through the comprehensive utilization of this part of lignin, the damage to the ecological environment can be eliminated, environmental friendliness can be created, and lignin can be highly valued, thereby creating economic benefits.

[0003] Polyamide, also known as nylon, is a heterochain polymer with an amide group in the main chain. Polyamide materials are used in the field of engineering plastics due to their excellent performance to replace some traditional metal materials. Due to the extensive use of polyamide materials in social production and life, the fire safety hazards inherent in polyamide materials have gradually attracted attention, and it is very necessary to modify them to be flame retardant.

[0004] Intumescent flame retardant (IFR) is mainly composed of three parts, namely acid source (mainly phosphorus-containing compounds), gas source (mainly nitrogen-containing compounds) and carbon source (mainly polyhydroxy compounds). Its mechanism of action is: during the heating process of IFR, the carbonizing agent is dehydrated under the action of the acid source to generate ester compounds; then the ester compounds are dehydrated and cross-linked to form carbon, and the carbonized products form a dense carbon layer with a fluffy closed foaming structure under the action of the gas decomposition gas of the gas source. The carbon layer is an amorphous structure. Once formed, it is non-flammable by itself, and can prevent heat conduction between the polymer and the heat source, thereby increasing the thermal degradation temperature of the polymer. In addition, the porous carbon layer can prevent the diffusion of gases produced by pyrolysis, and can also prevent external oxygen from diffusing to the surface of the uncracked polymer. When there is a lack of sufficient oxygen and heat energy during the combustion process, the burning polymer will self-extinguish.

[0005] The various functional groups contained in lignin itself lay the theoretical foundation for its modification. In addition, since lignin contains a large number of aromatic rings and non-polar groups in its chemical structure, it has high thermal stability and excellent carbonization ability, making it a good carbonizing agent.

[0006] Therefore, how to use the above-mentioned lignin in the flame retardant system and further improve the flame retardant properties of polyamide has become an urgent problem to be solved by manufacturers in the industry. Summary of the invention

[0007] The purpose of the present invention is to solve the defects mentioned in the above background technology by proposing a one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants and their application in polyamide.

[0008] The technical solution adopted by the present invention is as follows:

[0009] A one-pot method for preparing a nitrogen- and phosphorus-containing lignin-based flame retardant is provided, comprising the following steps:

[0010] Step 1: react cyanuric chloride with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in N,N-dimethylformamide solution to obtain intermediate TD;

[0011] Step 2: react the intermediate TD with hydroxyl-containing lignin in an N,N-dimethylformamide solution to prepare a nitrogen- and phosphorus-containing lignin-based flame retardant.

[0012] As a preferred technical solution of the present invention: the intermediate TD is obtained by reacting part of the C-Cl bonds in cyanuric chloride with the PH bonds of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

[0013] As a preferred technical solution of the present invention: in the step 1, the N,N-dimethylformamide solution of cyanuric chloride is stirred uniformly at 0-5°C and in an inert gas atmosphere, and then 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added, and then a certain amount of triethylamine is added, and the reaction is carried out at 0-5°C for 3-6 hours, and then the temperature is raised to 30-50°C and the reaction is continued for 3-6 hours.

[0014] As a preferred technical solution of the present invention: in the step 2, after adding the N,N-dimethylformamide solution of lignin containing hydroxyl groups, stir evenly, then add a certain amount of triethylamine, and then heat to 70-100°C and continue to react for 4-9 hours to obtain the product LTD, and then elute the product LTD with ethanol, dry and crush to obtain the nitrogen- and phosphorus-containing lignin-based flame retardant.

[0015] As a preferred technical solution of the present invention: the drying is carried out at a temperature of 60-80° C. for 12-24 hours.

[0016] As a preferred technical solution of the present invention: the molar ratio of the hydroxyl group, cyanuric chloride and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is 1:1:(1-2), and the reaction equation is as follows:

[0017] .

[0018] On the other hand, the present invention also provides a flame retardant prepared by the one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardant, and an application of the flame retardant in polyamide.

[0019] The steps include:

[0020] The nitrogen-containing and phosphorus-containing lignin-based flame retardant and nylon 12 are mixed and then kneaded, and then the kneaded materials are pressed and formed under a certain temperature and pressure.

[0021] The mixing temperature is 190-230°C.

[0022] The pressing molding temperature is 200-230° C. and the pressure is 5-10 MPa.

[0023] The nitrogen-containing and phosphorus-lignin-based flame retardant / nylon 12 flame retardant composite material comprises the following components in parts by weight: 5-30 parts of nitrogen-containing and phosphorus-lignin-based flame retardant and 70-95 parts of nylon 12.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The present invention provides a one-pot method for preparing a nitrogen-containing, phosphorus-containing lignin-based flame retardant and the application of the flame retardant in polyamide, wherein the flame retardant is an intumescent flame retardant. The lignin-based flame retardant of the present invention contains nitrogen and phosphorus, does not contain halogen, and is a halogen-free flame retardant. The phosphorus and nitrogen elements used are environmentally friendly compared to halogen flame retardants. The present invention utilizes -C-Cl on cyanuric chloride (TCT) to react with -PH of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and then utilizes the hydroxyl in lignin (Lignin) to react with -C-Cl on cyanuric chloride (TCT), and finally obtains a halogen-free lignin-based flame retardant containing nitrogen and phosphorus. Because lignin is a very good carbonizing agent, it has a good effect on synergistic flame retardancy, thereby forming an intumescent flame retardant carbonizing agent, and TCT and DOPO provide a phosphorus source and a nitrogen source for the system, and under the synergistic effect of the three, the optimal flame retardant effect is obtained. Compared with traditional flame retardants, the addition of lignin significantly reduces the cost of flame retardants. The lignin-based flame retardant prepared by the present invention is applied to polyamide to obtain a low-cost flame retardant polyamide material with excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a reaction synthesis route for nitrogen- and phosphorus-containing lignin-based flame retardants.

[0027] Figure 2 This is the infrared spectrum of the nitrogen- and phosphorus-containing lignin-based flame retardant prepared in Example 1. DETAILED DESCRIPTION

[0028] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of this embodiment can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] Embodiment 1:

[0030] Weigh 9.23g of cyanuric chloride (TCT) and dissolve it in 100ml of N,N-dimethylformamide at 0~5℃ and argon atmosphere, then add 21.60g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and stir to mix evenly, then add 5.10g of triethylamine and react at 0~5℃ for 3~6 hours. Then heat to 30~50℃ and continue to react for 3~6 hours. Weigh 3.30g of lignin and dissolve it in 80ml of N,N-dimethylformamide, stir and dissolve thoroughly, then add it to the above reaction system, then add 5.10g of triethylamine, heat to 70~100℃ and react for 4~9 hours, and elute with ethanol. After vacuum drying at 60-80°C for 12-24h, the mixture was crushed to obtain nitrogen-containing and phosphorus-containing lignin-based flame retardant LTD1. The infrared characterization of the synthesized nitrogen-containing and phosphorus-containing lignin-based flame retardant is as follows: Figure 2 shown.

[0031] Embodiment 2:

[0032] Weigh 10.46g of cyanuric chloride (TCT) and dissolve it in 100ml of N,N-dimethylformamide at 0~5℃ and argon atmosphere, then add 21.60g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and stir to mix evenly, then add 6.10g of triethylamine and react at 0~5℃ for 3~6 hours. Then heat to 30~50℃ and continue to react for 3~6 hours. Weigh 7.72g of lignin (Lignin) and dissolve it in 80ml of N,N-dimethylformamide, stir and dissolve it thoroughly, then add it to the above reaction system, then add 10.10g of triethylamine, heat to 70~100℃ and react for 4~9 hours, and elute with ethanol. After vacuum drying at 60~80℃ for 12~24h, crush it to obtain nitrogen-containing and phosphorus-containing lignin-based flame retardant LTD2.

[0033] Comparative Example 1:

[0034] 100g of nylon 12 (PA12) was weighed, pressed at 200-230℃ and 5-10MPa, and then cut to obtain test strips for mechanical properties and flame retardancy. The test results of the test strips are shown in Table 1.

[0035] Embodiment 3:

[0036] Weigh 90g of nylon 12 and 10.0g of nitrogen- and phosphorus-containing lignin-based flame retardant (LTD1), mix them evenly, add them to an internal mixer for internal mixing, and then press them at 200-230℃ and 5-10MPa to form the test strips for mechanical properties and flame retardancy. The test results of the test strips are shown in Table 1.

[0037] Embodiment 4:

[0038] Weigh 80g of nylon 12 and 20.0g of nitrogen- and phosphorus-containing lignin-based flame retardant (LTD1), mix them evenly, add them to an internal mixer for internal mixing, and then press them at 200-230℃ and 5-10MPa to form the test strips for mechanical properties and flame retardancy. The test results of the test strips are shown in Table 1.

[0039] Embodiment 5:

[0040] Weigh 70g of nylon 12 and 30.0g of nitrogen- and phosphorus-containing lignin-based flame retardant (LTD1), mix them evenly, add them to an internal mixer for internal mixing, and then press them at 200-230℃ and 5-10MPa to form the test strips for mechanical properties and flame retardancy. The test results of the test strips are shown in Table 1.

[0041] Embodiment 6:

[0042] Weigh 90g of nylon 12 and 10.0g of nitrogen- and phosphorus-containing lignin-based flame retardant (LTD2), mix them evenly, add them to an internal mixer for internal mixing, and then press them at 200-230℃ and 5-10MPa to form the test strips for mechanical properties and flame retardancy. The test results of the test strips are shown in Table 1.

[0043] Embodiment 7:

[0044] Weigh 80g of nylon 12 and 20.0g of nitrogen- and phosphorus-containing lignin-based flame retardant (LTD2), mix them evenly, add them to an internal mixer for internal mixing, and then press them at 200-230℃ and 5-10MPa to form the test strips for mechanical properties and flame retardancy. The test results of the test strips are shown in Table 1.

[0045] Embodiment 8:

[0046] Weigh 70g of nylon 12 and 30.0g of nitrogen- and phosphorus-containing lignin-based flame retardant (LTD2), mix them evenly, add them to an internal mixer for internal mixing, and then press them at 200-230℃ and 5-10MPa to form the test strips for mechanical properties and flame retardancy. The test results of the test strips are shown in Table 1.

[0047] Embodiment 9:

[0048] Weigh 80g of nylon 12 and 30.0g of lignin, mix them evenly and add them to an internal mixer for internal mixing. Then, press them at 200-230℃ and 5-10MPa, and cut them to obtain test strips for mechanical properties and flame retardancy. The test results of the test strips are shown in Table 1.

[0049] Performance Test:

[0050] (1) Tensile performance test: The test is carried out in accordance with the national standard GB / T 1040.2-2022.

[0051] (2) Oxygen index test: Tested in accordance with the standard GB / T 2406.2-2009.

[0052] Table 1: Flame-retardant polyamides prepared in Comparative Example 1 and Examples 3 to 9, tensile strength, tensile modulus, oxygen index and UL-94.

[0053]

[0054] Note: UL-94 grades increase gradually from NR, V-2, V-1 to V-0.

[0055] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0056] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants, characterized in that: The steps include: Step 1: react cyanuric chloride with 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in N,N-dimethylformamide solution to obtain intermediate TD; Step 2: react the intermediate TD with hydroxyl-containing lignin in an N,N-dimethylformamide solution to prepare a nitrogen- and phosphorus-containing lignin-based flame retardant.

2. The one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants according to claim 1, characterized in that: The intermediate TD is obtained by reacting part of the C-Cl bonds in cyanuric chloride with the PH bonds of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide.

3. The one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants according to claim 1, characterized in that: In the step 1, the N,N-dimethylformamide solution of cyanuric chloride is stirred uniformly at 0-5° C. in an inert gas atmosphere, and then 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added, and then a certain amount of triethylamine is added, and the reaction is carried out at 0-5° C. for 3-6 hours, and then the temperature is raised to 30-50° C. and the reaction is continued for 3-6 hours.

4. The one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants according to claim 1, characterized in that: In the step 2, after adding the N,N-dimethylformamide solution of lignin containing hydroxyl groups, stir evenly, then add a certain amount of triethylamine, and then heat to 70-100° C. and continue to react for 4-9 hours to obtain the product LTD, and then elute the product LTD with ethanol, dry and crush to obtain the nitrogen- and phosphorus-containing lignin-based flame retardant.

5. The one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants according to claim 4, characterized in that: The drying is carried out at a temperature of 60-80° C. for 12-24 hours.

6. The one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants according to claim 1, characterized in that: The molar ratio of the hydroxyl group, cyanuric chloride and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide of the lignin is 1:1:(1-2).

7. The one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants according to claim 1, characterized in that: The lignin is any one of enzymatic lignin, alkali lignin, organic solvent lignin and sulfonate lignin.

8. A flame retardant prepared by the one-pot method for preparing nitrogen- and phosphorus-containing lignin-based flame retardants according to any one of claims 1 to 7.

9. Use of the flame retardant according to claim 8 in polyamide.

10. Use of the flame retardant according to claim 9 in polyamide, the preparation of the polyamide is as follows: The nitrogen-containing and phosphorus lignin-based flame retardant and nylon 12 are mixed and then banburying is performed, and then the banburying material is pressed at a banburying temperature of 190-230° C., a pressing temperature of 200-230° C., and a pressure of 5-10 MPa to obtain polyamide.

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