Ionic liquid based on lignin, as well as a manufacturing process and an application thereof

Description

2. Ionic liquid based on lignin. This ionic liquid can support APP in improving the flame retardancy of composite materials. Technical solution: a process for the production of an ionic liquid based on lignin, comprising the following steps: (1) Production of ligninamine: Synthesizing lignin or degraded lignin to ligninamine via the Mannich reaction, whereby a solution of potassium ferrocyanide (K₃Fe₈(CN)₆) is added to the ligninamine solution, causing the ligninamine to precipitate completely and being dried after suction filtration and washing with water; (2) Production of lignin quaternary ammonium salt: using a mixture of isopropanol and water as a dispersant, a reflux reaction of ligninamine with 2,3-epoxypropyltrimethylammonium chloride is carried out, and after completion of the reaction, washing with ethanol and suction filtration are carried out several times on the reaction mixture to obtain solids, which is then vacuum dried.to obtain lignin quaternary ammonium salt; (3) Preparation of lignin-based ionic liquid: the lignin quaternary ammonium salt is mechanically stirred with sodium trifluoromethanesulfonate or sodium fluoroboratina ionized water; after completion of the ion exchange reaction, the mixture is repeatedly washed with ionized water, suction filtered, and vacuum dried to obtain the lignin-based ionic liquid. The aforementioned lignin may be alkali lignin, lignosulfonate, biobutano lignin, or bioethanol lignin. Degradation processes used to degrade lignin include degradation by hydrogen peroxide oxidation, degradation by ozone oxidation, acid hydrolysis, alkaline hydrolysis, degradation by hydrogenation reduction, and high-temperature pyrolysis. The Mannich reaction used aminos, specifically linear diamine, in particular ethylenediamine, 1,3-propanediamine, triethylenetetramine, or tetraethylenepentamine. The preparation method for ligninamine is as follows: Add 5–15 mL of water and 2–8 mL of 0.5 mol / LNaOH solution to 1–5 g lignin in the ratio; stirring at 40–80°C to ensure complete dissolution of the lignin; subsequent addition of 2–6 mL formaldehyde and 1–8 mL diamine, stirring under reflux for 2–4 hours to synthesize the ligninamine; adding a sufficient amount of 5–15% potassium ferrocyanide (K₃Fe₈(CN)₆) solution to the ligninamine solution so that the ligninamine is completely precipitated, and drying after suction filtration and washing with water.30 The preparation procedure for the ligninamine is as follows: Adding 8 mL water and 5 mL 0.5 mol / LNaOH solution to 3 g lignin in the ratio; stirring at 75°C to ensure to ensure complete dissolution of the lignin; subsequently adding 3 mL of formaldehyde and 4 mL of diamine, stirring under reflux for 3 hours to synthesize the ligninamine; adding a sufficient amount of 10% potassium ferrocyanide solution (K₃Fe₈(CN)₆) to the ligninamine solution so that the ligninamine is completely precipitated,and drying after suction filtration and washing with water. BE2025 / 7051 3 The manufacturing process for the lignin quaternary ammonium salt is as follows: Weighing out 0.5–2 g of ligninamine and 1–4 g of 2,3-epoxypropyltrimethylammonium chloride in the ratio, and adding 100 mL of water-isopropanol (mass ratio = (1–3) / (2–6)) as a dispersant, stirring the mixture for 5–10 hours at 60–90°C, whereby after completion of the reaction the reaction mixture is washed several times with ethanol and suction filtration to obtain solids; finally vacuum drying at 40°C to obtain the lignin quaternary ammonium salt. The manufacturing process for the lignin quaternary ammonium salt is as follows: Weighing out 1 g of ligninamine and 3 g of 2,3-epoxypropyltrimethylammonium chloride in the ratio, and adding 100 mL of water-isopropanol (mass ratio = 2 / 5) as a dispersant, stirring the mixture for 10 hours at 80°C, whereby after completion of the reaction the reaction mixture is washed several times with ethanol and filtered by suction.to obtain solids; finally, vacuum drying at 40°C to obtain the lignin quaternary ammonium salt. Preparation of the lignin-based ionic liquid: Mix 1–5 g of lignin quaternary ammonium salt, 2–10 g of sodium trifluoromethanesulfonate or sodium fluoroborate, and 100–300 g of deionized water in the ratio until a uniform state is achieved and stir mechanically; repeated washing and absorbent filtration with deionized water after 24 hours, vacuum drying at 40°C to obtain the lignin-based ionic liquid. Preparation of the lignin-based ionic liquid: Mix 2 g of lignin quaternary ammonium salt, 6 g of sodium trifluoromethanesulfonate or sodium fluoroborate, and 200 ml of ionized water in the ratio required to achieve a uniform consistency and stir mechanically; repeat washing and absorbent filtration with ionized water after 24 hours, vacuum drying at 40°C to obtain the lignin-based ionic liquid.which is produced by the above process.25 An application of the ionic liquid based on lignin in the manufacture of flame-retardant plastics. Advantages: 1. Lignin has a high carbon residue; the present invention uses industrial lignin as a starting material for the production of ionic liquids as flame retardants and thus opens up a new application route for industrial lignin in the field of flame retardants. 2. The production of the ionic liquids as flame retardants is carried out by an ion exchange process; this production method is simple, and in the production of the lignin quaternary ammonium salt, the establishment of a weakly acidic environment promotes the ring opening of the epoxy group and its reaction with the amino group. Since 2,3-epoxypropyltrimethylammonium chloride is water-soluble, the two-phase reaction also facilitates the simple separation of the product. Furthermore, in conventional technologies, lignin is produced as ligninamine after a Mannich reaction by acidification to pH 2-3. BE2025 / 7051 4 failed,Under these conditions, however, the primary amino groups are mostly also present in salt-like form. In contrast, the present invention precipitates the ligninamine by adding potassium ferrocyanide at pH 8-9. In this way, the amino groups are not present in salt-like form, which facilitates the subsequent reaction step with the epoxy group. This process has low energy consumption and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWING Figure 1 shows the thermogravimetric analyses (TGA) of APP, lignin-APP, and ionic liquid-based APP (atmosphere: nitrogen, using alkali lignin as an example after oxidative degradation with hydrogen peroxide). The three curves in the