Intumescent bio-based flame retardant, flame-retardant silk fabric and preparation method thereof

Abstract

The present invention discloses an intumescent bio-based flame retardant, a flame-retardant silk fabric, and a preparation method thereof, relating to the technical field of flame retardants. The method comprises preparing ethanolamine phytate; dissolving cyanuric chloride in tetrahydrofuran to obtain a cyanuric chloride solution, dissolving ethanolamine phytate in water, and adding a pH regulator to obtain an ethanolamine phytate aqueous solution; adding the ethanolamine phytate aqueous solution dropwise to the cyanuric chloride solution under a nitrogen atmosphere, reacting while stirring, adding an acid-binding agent, allowing the mixture to stand for separation and extraction, collecting the upper aqueous phase, and freeze-drying to obtain a crude product; washing the crude product and vacuum drying to obtain the intumescent bio-based flame retardant. The intumescent bio-based flame retardant of the present invention has a good sustainable flame retardant effect and exhibits an intumescent carbon residue at high temperatures, thereby protecting silk fabrics from high-temperature damage.

Description

Technical Field

[0001] The invention relates to an intumescent bio-based flame retardant, a flame-retardant silk fabric and a preparation method thereof, and belongs to the technical field of flame retardants. Background Art

[0002] Silk, prized for its soft texture, elegant sheen, and exceptional comfort, is widely used in high-end apparel, home decor, and wall coverings. However, despite its many advantages, silk, as a protein fiber, suffers from poor flame retardancy. When exposed to fire, silk fabrics tend to burn rapidly and produce large amounts of smoke, a concern in applications such as clothing and everyday items. Therefore, research on flame-retardant finishing of silk fabrics is essential. This research not only aims to impart superior flame retardancy without compromising their inherent properties, but also effectively enhances their potential for application in various fields.

[0003] With the continuous deepening of the concept of sustainable development, the development of green and environmentally friendly flame retardant materials has become an important direction of current research. Phytic acid, as an organic phosphate compound naturally present in plants, is rich in phosphorus and has the ability to catalyze the dehydration of textiles into carbon. It has been widely used in the field of flame retardant materials in recent years. Existing studies use phytic acid and chitosan to flame retardant finish silk fabrics through a layer-by-layer self-assembly method. Although this method effectively gives silk fabrics excellent flame retardant properties, the flame retardant durability of the finished fabric is still not ideal. This may be because phytic acid and silk fibers are mainly bonded through electrostatic effects, and it is difficult to form a stable covalent bond connection, resulting in poor water washing resistance of silk fabrics treated with phytic acid, which is difficult to meet the needs of actual applications.

[0004] Intumescent flame retardants (IFRs) have been widely researched and applied as environmentally friendly and efficient flame retardant systems. IFRs primarily consist of an acid source, a gas source, and a carbon source. Among these, phosphorus-nitrogen (PN)-containing intumescent flame retardants have become a research hotspot due to their excellent synergistic flame retardancy, low smoke, and low toxicity. PN intumescent flame retardants promote the rapid formation of a char layer when heated, forming a dense and thermally stable protective barrier that effectively isolates heat and combustible gases, significantly improving the flame retardancy of the material. Existing studies have synthesized reactive intumescent flame retardants using an esterification reaction between phytic acid, triethanolamine, and citric acid. These flame-retardant treatments require curing silk fabrics at 160°C. While the treated silk fabrics exhibit good flame retardancy, the high temperature damages the fabric. Others have used a layer-by-layer (LBL) assembly technique to create an intumescent coating composed of chitosan, phytic acid, and sodium alginate on PA66 fabric, significantly enhancing its flame retardancy and anti-drip properties. However, this technology has a complicated process and seriously damages the physical properties of the fabric, such as feel and strength.

[0005] Therefore, how to develop new phytic acid-based intumescent flame retardants and prepare flame-retardant silk fabrics under mild conditions is of great significance and still faces great challenges. Summary of the Invention

[0006] The present invention aims to overcome the deficiencies in the prior art by providing an intumescent bio-based flame retardant, a flame-retardant silk fabric, and a method for preparing the same. The intumescent bio-based flame retardant exhibits a good sustainable flame retardant effect and exhibits intumescent carbon residue at high temperatures, thereby protecting the substrate (silk fabric) from high-temperature attack. Furthermore, the preparation method is simple and operates under mild reaction conditions.

[0007] To achieve the above object, the present invention is implemented by adopting the following technical solutions:

[0008] In a first aspect, the present invention provides an intumescent bio-based flame retardant having the chemical formula:

[0009] .

[0010] In a second aspect, the present invention further provides a method for preparing the above-mentioned intumescent bio-based flame retardant, comprising:

[0011] Preparation of ethanolamine phytate;

[0012] dissolving ethanolamine phytate in water, and adding a pH regulator to adjust the pH value to be within the range of 6 to 7 to obtain an ethanolamine phytate aqueous solution;

[0013] The aqueous solution of ethanolamine phytate is added to the cyanuric chloride solution to carry out the first nucleophilic substitution reaction, and the solution is allowed to stand for separation and extraction, and the upper aqueous phase is collected and freeze-dried to obtain a crude product;

[0014] The crude product is washed and vacuum dried to obtain an intumescent bio-based flame retardant;

[0015] Wherein, the first nucleophilic substitution reaction is that the amino group of ethanolamine phytate replaces one chlorine in cyanuric chloride.

[0016] Furthermore, the preparation of ethanolamine phytate comprises:

[0017] Phytic acid and ethanolamine are subjected to esterification reaction, and after the esterification reaction is completed, tetrahydrofuran is added to the reaction system, and the mixture is stirred evenly and allowed to stand, and then liquid separation and extraction are performed to obtain ethanolamine phytate.

[0018] Furthermore, the molar ratio of phytic acid to ethanolamine is 1:(2.3-2.5);

[0019] And / or, the esterification reaction conditions include reacting at 120-130° C. for 2-3 hours, and condensing the reaction system during the reaction.

[0020] Furthermore, at least one of the following conditions must be met:

[0021] The cyanuric chloride solution is obtained by dissolving cyanuric chloride in tetrahydrofuran;

[0022] The molar ratio of the ethanolamine phytate to cyanuric chloride is 1:(2.3-2.5);

[0023] The conditions of the first nucleophilic substitution reaction include reacting at a temperature of 0-5°C for 2-3 hours, and adding an acid-binding agent during the reaction to control the pH value to be within the range of 6-7;

[0024] The pH regulator and the acid binding agent are the same reagent, which is one of a 20-30wt% sodium carbonate aqueous solution, a 3-5wt% sodium hydroxide aqueous solution, and a 20-30wt% sodium bicarbonate aqueous solution;

[0025] The ethanolamine phytate aqueous solution is added to the cyanuric chloride dropwise, and stirring is performed during the dropwise addition process;

[0026] The washing adopts toluene;

[0027] The vacuum drying comprises drying at 110-120° C. for 3-4 hours.

[0028] In a third aspect, the present invention provides a method for preparing a flame-retardant silk fabric, comprising:

[0029] dissolving the intumescent bio-based flame retardant and anhydrous piperazine in water to obtain a mixed solution;

[0030] immersing the silk fabric in the mixed solution, heating and shaking the mixture to cause the mixture to undergo a second nucleophilic substitution reaction, thereby obtaining a flame retardant finishing solution;

[0031] The temperature of the flame retardant finishing liquid is continuously increased while maintaining an oscillation state to allow the third nucleophilic substitution reaction to proceed. After the reaction is completed, the silk fabric is taken out, rinsed, and naturally air-dried to obtain a flame retardant silk fabric.

[0032] Wherein, the second nucleophilic substitution reaction is that the NH group of anhydrous piperazine replaces one chlorine in the intumescent bio-based flame retardant with the amino group and hydroxyl group of the silk fabric;

[0033] The third nucleophilic substitution reaction is that the NH group of anhydrous piperazine replaces another chlorine in the intumescent bio-based flame retardant with the amino group and hydroxyl group of the silk fabric.

[0034] Furthermore, the molar ratio of the intumescent bio-based flame retardant to anhydrous piperazine is 1:(1.3-1.5);

[0035] And / or, the concentration of the intumescent bio-based flame retardant in the mixed solution is 50-100 g / L.

[0036] Furthermore, the condition parameters of the second nucleophilic substitution reaction include shaking at 30-40° C. for 0.5-1 h, and adding an acid binding agent during the shaking process to control the pH value in the range of 6-7;

[0037] And / or, the condition parameters of the third nucleophilic substitution reaction include shaking at 70-80° C. for 1-1.5 hours, and adding an acid binding agent during the shaking process to control the pH value within the range of 7-8.

[0038] Furthermore, the acid binding agent is one of a 20-30 wt% sodium carbonate aqueous solution, a 3-5 wt% sodium hydroxide aqueous solution, and a 20-30 wt% sodium bicarbonate aqueous solution.

[0039] In a fourth aspect, the present invention further provides a flame-retardant silk fabric prepared by the method for preparing the flame-retardant silk fabric as described in the third aspect.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention utilizes phytic acid, a biomass raw material, to produce a phosphorus / nitrogen compound, ethanolamine phytate, through an esterification reaction between the phosphate group of phytic acid and the hydroxyl group of ethanolamine. Furthermore, the phosphorus / nitrogen compound is introduced into the triazine ring structure by utilizing the gradual reaction characteristics of the three active chlorine atoms in the cyanuric chloride molecule at different temperatures. Specifically, the three chlorine atoms in the cyanuric chloride molecule are located in symmetrical positions on the triazine ring, and their nucleophilic substitution activity decreases in sequence, exhibiting a clear reaction sequence: the first chlorine atom can be replaced by a nucleophile at a relatively low temperature (0-5°C), the second chlorine atom requires reaction at a moderate temperature (30-40°C), and the third chlorine atom generally requires replacement at a higher temperature (70-80°C). Therefore, by distributing and regulating the reaction temperature, the phosphorus / nitrogen compound is introduced into the triazine ring structure, effectively improving the superior flame retardancy and durability. The resulting intumescent bio-based flame retardant has the advantages of being low-carbon and environmentally friendly, easily adjustable in the ratio of the "three sources", minimal impact on other material properties, and high flame retardancy efficiency.

[0042] The method for preparing flame-retardant silk fabric provided by the present invention uses phytic acid as an acid source and a carbon source, ethanolamine as a gas source, cyanuric chloride as a gas source and a carbon source, and piperazine and a silk fabric substrate as gas sources to synergistically construct an intumescent flame retardant system, significantly improving the flame retardant efficiency. The preparation process is simple, the reaction conditions are mild, and the method has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1This is an infrared spectrum of phytic acid, ethanolamine, cyanuric chloride and dichloro-s-triazine phytate in the preparation method of an intumescent bio-based flame retardant in one embodiment of the present invention;

[0044] Figure 2 Schematic diagram comparing vertical burning results of the flame-retardant silk fabric prepared in Example 1 of the present invention and the non-flame-retardant silk fabric of Comparative Example 1. DETAILED DESCRIPTION

[0045] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0046] The present invention provides a method for preparing an intumescent bio-based flame retardant, comprising the following steps:

[0047] First, phytic acid and ethanolamine undergo an esterification reaction at a high temperature of 120-130°C for 2-3 hours, producing a golden, viscous liquid. Since both phytic acid and ethanolamine are liquids, a condenser is required to prevent volatilization of the high-temperature reaction liquid. Increasing the reaction temperature and time facilitates the esterification reaction, but excessively high temperatures or prolonged reaction times can lead to waste of raw materials. The molar ratio of phytic acid to ethanolamine is 1:2.3-2.5, so a slight excess of ethanolamine is used to ensure complete reaction of the phytic acid.

[0048] After the esterification reaction is completed, an appropriate amount of tetrahydrofuran is added to the reaction system, stirred evenly, and allowed to stand. Since the phytic acid reaction is complete, only ethanolamine and ethanolamine phytate remain in the reaction system. Taking advantage of the fact that ethanolamine is soluble in tetrahydrofuran while ethanolamine phytate is insoluble in tetrahydrofuran, pure ethanolamine phytate is obtained by separation extraction.

[0049] In some embodiments, tetrahydrofuran can be replaced by acetonitrile, acetone, etc.

[0050] Then, cyanuric chloride is dissolved in tetrahydrofuran to obtain a cyanuric chloride solution, and ethanolamine phytate is dissolved in deionized water. A pH adjuster is used to adjust the pH value of the solution to 6-7 to obtain an ethanolamine phytate aqueous solution.

[0051] Under a nitrogen atmosphere, slowly add an aqueous solution of ethanolamine phytate dropwise to a cyanuric chloride solution at 0-5°C to allow a primary nucleophilic substitution reaction between the amino group of ethanolamine phytate and a chlorine in the cyanuric chloride. Magnetic stirring is performed while the reaction is continued for 2-3 hours, during which an acid-binding agent is slowly added. After completion of the reaction, the mixture is allowed to stand and then subjected to separation and extraction. The upper aqueous phase is collected and freeze-dried to yield a crude, pale yellow powder.

[0052] Among them, the pH regulator and the acid binding agent are both sodium carbonate aqueous solution with a concentration of 20-30wt%. The pH regulator is used to adjust the pH value of the solution to 6-7 to ensure that the subsequent first nucleophilic substitution reaction proceeds smoothly. The role of the acid binding agent is to remove HCl generated by the nucleophilic substitution reaction to ensure the forward direction of the first nucleophilic substitution reaction. In some embodiments, sodium hydroxide and sodium bicarbonate are also acceptable.

[0053] The crude product was washed with toluene and then vacuum dried at 110-120°C for 3-4 hours to obtain pure dichloro-s-triazine phytate, i.e., an intumescent bio-based flame retardant.

[0054] The structural formula of dichloro-s-triazine phytate is:

[0055] ;

[0056] The infrared spectra of phytic acid, ethanolamine, cyanuric chloride and dichloro-2-triazine phytate are shown in Figure 2. Figure 1 As shown in the infrared spectrum of dichloro-2-triazine phytate, 956 cm -1 and 1061 cm -1 The absorption peaks at 3132 cm are caused by the stretching vibrations of PO and P=O groups in phytic acid. -1 The characteristic absorption peak of alcoholic hydroxyl group at 1151 cm is significantly reduced after esterification reaction. -1 A new absorption peak appeared at 1401 cm, which was caused by the stretching vibration of the POC group and corresponded to the ester bond formed after the esterification reaction between phytic acid and ethanolamine. -1 The characteristic peaks at 1493 cm-1 and 1493 cm-2 also appear in the spectrum of dichloro-2-triazine phytate. The characteristic peaks of C=N and CN groups on the triazine ring also appear at 1493 cm-1. -1 and 1273 cm -1 In addition, after the single nucleophilic substitution reaction, the -1 The C-Cl absorption peak at 37° underwent an obvious low wavenumber shift. The above analysis proved that dichloro-2-triazine phytate was successfully prepared through esterification and nucleophilic substitution reactions.

[0057] The present invention also provides a method for preparing a flame-retardant silk fabric, comprising the following steps:

[0058] Dichloro-s-triazine phytate and anhydrous piperazine are dissolved in water to obtain a mixed solution, wherein the molar ratio of dichloro-s-triazine phytate to anhydrous piperazine is 1:(1.3-1.5). A silk fabric is immersed in the mixed solution, and the solution system is shaken for a first time at 30-40°C for 0.5-1 hour to allow the NH group of the anhydrous piperazine to undergo a second nucleophilic substitution reaction with the amino group and hydroxyl group of the silk fabric and a chlorine group in the dichloro-s-triazine phytate. During this reaction, an acid-binding agent is slowly added to adjust the pH of the reaction system to 6-7, thereby promoting the substitution reaction between piperazine, silk fabric, and dichloro-s-triazine phytate, thereby obtaining a flame-retardant finishing solution. The silk fabric is then modified into a monochlorine-modified flame-retardant silk fabric.

[0059] The concentration of dichloro-s-triazine phytate in the mixed solution is 50-100 g / L. The higher the amount of dichloro-s-triazine phytate used, the higher the amount of piperazine required, the higher the concentration of the flame retardant in the prepared finishing solution, and the better the flame retardant effect.

[0060] The system temperature was raised and the mixture was shaken for a second time at 70-80°C for 1-1.5 hours to ensure a third nucleophilic substitution reaction between the NH groups of piperazine and the amino, hydroxyl, and chlorine groups of dichloro-s-triazine phytate on the silk fabric. During this reaction, an acid-binding agent was slowly added to maintain the pH of the mixture between 7 and 8. After impregnation, the silk fabric was rinsed with water and then air-dried to obtain a flame-retardant silk fabric.

[0061] The role of the acid-binding agent added in the second nucleophilic substitution reaction is to remove HCl generated by the nucleophilic substitution reaction, thereby ensuring that the second nucleophilic substitution reaction proceeds in the forward direction.

[0062] The role of the acid-binding agent added in the third nucleophilic substitution reaction is, on the one hand, to act as an alkaline agent to maintain the pH of the mixed solution at 7-8, thereby preventing the silk fabric from being severely damaged due to a decrease in strength during the immersion process under acidic conditions; and on the other hand, to act as an acid-binding agent to neutralize the HCl generated in the substitution reaction, thereby promoting the smooth progress of the third nucleophilic substitution reaction.

[0063] After the final reaction, unreacted piperazine in the mixture does not need to be removed. It can be adsorbed onto the surface of the silk fabric, helping to build an intumescent flame retardant system and further improving flame retardant efficiency. The acid-binding agent must be consistent with the pH regulator and acid-binding agent used in the preparation of the intumescent bio-based flame retardant.

[0064] The properties of flame retardant silk fabrics are analyzed below with reference to specific examples.

[0065] Example 1

[0066] This embodiment provides a method for preparing a flame-retardant silk fabric, comprising the following steps:

[0067] (1) Phytic acid (0.025 mol, 23 g) and ethanolamine (0.0625 mol, 3.8 g) were added to a single-necked flask and placed in a magnetic stirrer. The mixture was refluxed at 130 °C for 2 h. After the reaction, a golden viscous liquid was obtained. Then, an appropriate amount of tetrahydrofuran was added, stirred, and allowed to stand for separation and extraction to obtain pure ethanolamine phytate.

[0068] Cyanuric chloride (0.0625 mol, 11.5 g) was then dissolved in tetrahydrofuran and transferred to a three-necked flask. Ethanolamine phytate was dissolved in deionized water, adjusted to pH 6 with 20% sodium carbonate solution, and slowly added dropwise to the cyanuric chloride solution in the three-necked flask.

[0069] Under a nitrogen atmosphere, the temperature was maintained at 2°C and magnetic stirring was applied for 2.5 hours. During the stirring process, a 20% sodium carbonate aqueous solution was slowly added to maintain a pH of 6.5. Finally, the mixture was allowed to stand for separation and extraction. The upper aqueous solution was collected and freeze-dried to obtain a crude light yellow powder product.

[0070] After washing with toluene, the product was dried in a vacuum oven at 110°C for 4 hours to obtain pure dichloro-2-triazine phytate powder. Although the para structure was primarily formed due to steric hindrance, some meta structures were still formed, resulting in a non-unique flame retardant structure. The final yield was 77%.

[0071] (2) Dissolve 0.0048 mol of dichloro-s-triazine phytate (5 g) in deionized water to prepare a solution with a concentration of 50 g / L. Then, add 0.0062 mol of anhydrous piperazine (0.54 g) to obtain a mixed solution, and immerse the silk fabric in the mixed solution. The resulting mixed solution is then placed in a shaking water bath at 40°C for 45 min. Simultaneously, a 20% by mass sodium carbonate solution is slowly added dropwise, and the pH value of the system is adjusted and maintained at approximately 6.5. Finally, a flame retardant finishing solution is prepared.

[0072] (3) Then, the oscillating water bath was heated to 80°C and oscillated for 1 hour, during which a 20% by mass sodium carbonate aqueous solution was slowly added to maintain the pH of the finishing solution at 7. The flame-retardant silk fabric was prepared by constructing an intumescent flame-retardant system on the silk fabric.

[0073] Example 2

[0074] This embodiment provides a method for preparing a flame-retardant silk fabric, comprising the following steps:

[0075] (1) Phytic acid (0.025 mol, 23 g) and ethanolamine (0.0575 mol, 3.5 g) were added to a single-necked flask and placed in a magnetic stirrer. The mixture was refluxed at 120°C for 3 h. After the reaction, a golden viscous liquid was obtained. Then, an appropriate amount of tetrahydrofuran was added, stirred, and allowed to stand for separation and extraction to obtain pure ethanolamine phytate.

[0076] Cyanuric chloride (0.0575 mol, 10.6 g) was then dissolved in tetrahydrofuran and transferred to a three-necked flask. Ethanolamine phytate was dissolved in deionized water, adjusted to pH 7 with 25% sodium carbonate solution, and slowly added dropwise to the cyanuric chloride solution in the three-necked flask.

[0077] Under a nitrogen atmosphere, the temperature was maintained at 3°C ​​and magnetic stirring was applied for 3 h. During the stirring process, a 25% sodium carbonate aqueous solution was slowly added to maintain the pH value at 7. Finally, the mixture was allowed to stand for separation and extraction. The upper aqueous solution was collected and freeze-dried to obtain a light yellow powder crude product.

[0078] After washing with toluene, the product was dried in a vacuum oven at 120°C for 3 hours to obtain pure dichloro-s-triazine phytate powder. Although the para structure was primarily formed due to steric hindrance, some meta structures were still formed, resulting in a non-unique flame retardant structure. The final yield was 73%.

[0079] (2) Dissolve 0.0072 mol of dichloro-s-triazine phytate (7.5 g) in deionized water to prepare a solution with a concentration of 75 g / L. Then, add 0.017 mol of anhydrous piperazine (0.87 g) to obtain a mixed solution, and immerse the silk fabric in the mixed solution. The resulting mixed solution is then placed in a shaking water bath at 35°C for 1 h. Simultaneously, a 25% sodium carbonate solution is slowly added dropwise to adjust and maintain the pH value of the system at around 7. Finally, a flame retardant finishing solution is prepared.

[0080] (3) The oscillating water bath was then heated to 75°C and oscillated for 1 hour, during which a 25% by mass sodium carbonate aqueous solution was slowly added to maintain the pH of the finishing solution at 7.5. A flame-retardant silk fabric was prepared by constructing an intumescent flame-retardant system on the silk fabric.

[0081] Example 3

[0082] This embodiment provides a method for preparing a flame-retardant silk fabric, comprising the following steps:

[0083] (1) Phytic acid (0.025 mol, 23 g) and ethanolamine (0.06 mol, 3.66 g) were added to a single-necked flask and placed in a magnetic stirrer. The mixture was refluxed at 125°C for 2.5 h. After the reaction, a golden viscous liquid was obtained. Then, an appropriate amount of tetrahydrofuran was added, stirred, and allowed to stand for separation and extraction to obtain pure ethanolamine phytate.

[0084] Cyanuric chloride (0.06 mol, 11 g) was then dissolved in tetrahydrofuran and transferred to a three-necked flask. Ethanolamine phytate was dissolved in deionized water, adjusted to pH 7 with 30% sodium carbonate solution, and slowly added dropwise to the cyanuric chloride solution in the three-necked flask. Under a nitrogen atmosphere, the temperature was maintained at 2°C and magnetic stirring was applied for 3 h. During stirring, 30% sodium carbonate aqueous solution was slowly added to maintain the pH at 7. Finally, the mixture was allowed to stand and then subjected to separation and extraction. The upper aqueous solution was collected and freeze-dried to obtain a crude, light yellow powder.

[0085] After washing with toluene, the product was dried in a vacuum oven at 115°C for 3 hours to obtain pure dichloro-2-triazine phytate powder. Although the para structure was primarily generated due to steric hindrance, some meta structures were still formed, resulting in a non-unique flame retardant structure. The final yield was 76%.

[0086] (2) 0.0081 mol of dichloro-s-triazine phytate (8.5 g) was dissolved in deionized water to prepare a solution with a concentration of 85 g / L. 0.0194 mol of anhydrous piperazine (0.91 g) was then added to obtain a mixed solution, and the silk fabric was immersed in the mixed solution. The resulting mixed solution was then placed in a 40°C shaking water bath and shaken for 40 min. At the same time, a 30% mass fraction of sodium carbonate solution was slowly added dropwise, and the pH value of the system was adjusted and maintained at around 7. Finally, a flame retardant finishing solution was prepared.

[0087] (3) Then, the oscillating water bath was heated to 70°C and oscillated for 1.5 hours, during which a 30% by mass sodium carbonate aqueous solution was slowly added to maintain the pH of the finishing solution at 8. The flame-retardant silk fabric was prepared by constructing an intumescent flame-retardant system on the silk fabric.

[0088] Example 4

[0089] (1) Phytic acid (0.025 mol, 23 g) and ethanolamine (0.06 mol, 3.66 g) were added to a single-necked flask and placed in a magnetic stirrer. The mixture was refluxed at 125°C for 2.5 h. After the reaction, a golden viscous liquid was obtained. Then, an appropriate amount of tetrahydrofuran was added, stirred, and allowed to stand for separation and extraction to obtain pure ethanolamine phytate.

[0090] Cyanuric chloride (0.06 mol, 11 g) was then dissolved in tetrahydrofuran and transferred to a three-necked flask. Ethanolamine phytate was dissolved in deionized water, adjusted to pH 7 with 30% sodium carbonate solution, and slowly added dropwise to the cyanuric chloride solution in the three-necked flask. Under a nitrogen atmosphere, the temperature was maintained at 2°C and magnetic stirring was applied for 3 hours. During stirring, 30% sodium carbonate aqueous solution was slowly added to maintain the pH at 7. Finally, the mixture was allowed to stand and then subjected to separation and extraction. The upper aqueous solution was collected and freeze-dried to obtain a crude, light yellow powder.

[0091] After washing with toluene, the product was dried in a vacuum oven at 115°C for 3 hours to obtain pure dichloro-2-triazine phytate powder. Although the para structure was primarily generated due to steric hindrance, some meta structures were still formed, resulting in a non-unique flame retardant structure. The final yield was 76%.

[0092] (2) 0.0081 mol of dichloro-s-triazine phytate (8.5 g) was dissolved in deionized water to prepare a solution with a concentration of 85 g / L. 0.0194 mol of anhydrous piperazine (1.04 g) was then added to obtain a mixed solution, and the silk fabric was immersed in the mixed solution. The resulting mixed solution was then placed in a shaking water bath at 40°C and shaken for 40 min. At the same time, a 30% sodium carbonate solution was slowly added dropwise, and the pH value of the system was adjusted and maintained at around 7. Finally, a flame retardant finishing solution was prepared.

[0093] (3) Then, the oscillating water bath was heated to 70°C and oscillated for 1.5 hours, during which a 30% by mass sodium carbonate aqueous solution was slowly added to maintain the pH of the finishing solution at 8. The flame-retardant silk fabric was prepared by constructing an intumescent flame-retardant system on the silk fabric.

[0094] Comparative Example 1:

[0095] This comparative example provides a non-flame-retardant silk fabric, which is a double crepe with a gram weight of 52 g / L and is purchased from Jiangsu Huajia Silk Co., Ltd.

[0096] Comparative Example 2:

[0097] 0.0075 mol of phytic acid (5.3 g) was dissolved in deionized water to prepare a 50 g / L solution, and silk fabric was immersed in this solution. The solution was then placed in a shaking water bath at 70°C for 60 minutes to produce flame-retardant silk fabric.

[0098] Comparative Example 3:

[0099] 0.0075 mol of phytic acid (5.3 g) was dissolved in deionized water to prepare a 50 g / L solution. Subsequently, 0.0165 mol of ethanolamine (1 g) was added, followed by 0.0165 mol of cyanuric chloride (3 g) dissolved in 10 ml of acetone. This mixture was then added to the solution, and silk fabric was immersed in the solution. The solution was then shaken in a shaking water bath at 75°C for 50 minutes to produce a flame-retardant silk fabric.

[0100] Comparative Example 4:

[0101] The process is basically the same as Example 4, except that anhydrous piperazine is not added in step (2), and a flame-retardant silk fabric is finally obtained.

[0102] The silk fabrics of Examples 1-4 and Comparative Examples 1-4 were tested for damage length according to GB / T 5455-2014, "Fire performance of textiles - Determination of damage length in the vertical direction - Smoldering and afterflame time." The limiting oxygen index (LOI) of the fabrics was measured according to GB / T 5454-1997, "Fire performance of textiles - Oxygen index method." The fabrics' flammability was evaluated according to GB / T 17591-2006, "Flame-retardant fabrics." Washing procedures were performed according to AATCC 61-2006, "Accelerated test for color fastness to washing for household and commercial use." The carbon residue of the flame-retardant and non-flame-retardant silk fabrics was measured using thermal analysis under nitrogen conditions. The results are shown in Table 1.

[0103] Table 1: Performance test results of silk fabrics of Examples 1 to 4 and Comparative Example

[0104]

[0105] Combining the data in Table 1 and Figure 2As can be seen, the silk fabrics of Examples 1-4 outperformed the non-flame-retardant silk fabric of Comparative Example 1 in all indicators. In Examples 1-4, the flame retardancy of the flame-retardant silk fabrics gradually improved with increasing flame retardant dosage. The durable intumescent flame-retardant silk fabric prepared in Example 4 had a damage length of 8.8 cm, achieving flame retardancy B1, and a limiting oxygen index of 32.5% (compared to the damage length of the non-flame-retardant silk fabric of 30 cm and LOI of 23.5%). After 20 washes, the damage length was 12.6 cm, still meeting flame retardancy B1. Furthermore, thermal analysis under nitrogen conditions revealed a char residue of 41% at 700°C (compared to 20% for the non-flame-retardant silk fabric). This effectively demonstrates the excellent and sustainable flame retardancy of the intumescent bio-based flame retardant of the present invention. Furthermore, the formation of intumescent char residue at high temperatures protects the substrate (silk fabric) from high-temperature damage.

[0106] Comparing Comparative Example 2 with Example 1 shows that while phytic acid alone imparts good flame retardancy to silk fabrics, it lacks flame retardancy durability. However, the intumescent flame retardant synthesized using phytic acid facilitates the construction of an intumescent system, significantly improving the flame retardancy and washability of silk fabrics. Comparing Comparative Example 3 with Example 1 demonstrates that the synthetic flame retardant exhibits higher flame retardancy efficiency and superior washability compared to the compounded flame retardant. Comparing Comparative Example 4 with Example 4 demonstrates that the introduction of piperazine further enhances the flame retardancy of the intumescent system, thereby improving the flame retardancy and washability of silk fabrics.

[0107] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An intumescent bio-based flame retardant, characterized in that: Its chemical structural formula is: 。 2. A method for preparing the intumescent bio-based flame retardant according to claim 1, comprising: Preparation of ethanolamine phytate; dissolving ethanolamine phytate in water, and adding a pH regulator to adjust the pH value to be within the range of 6 to 7 to obtain an ethanolamine phytate aqueous solution; The aqueous solution of ethanolamine phytate is added to cyanuric chloride to carry out the first nucleophilic substitution reaction, and the mixture is allowed to stand for separation and extraction, and the upper aqueous phase is collected and freeze-dried to obtain a crude product; The crude product is washed and vacuum dried to obtain an intumescent bio-based flame retardant; Wherein, the first nucleophilic substitution reaction is that the amino group of ethanolamine phytate replaces one chlorine in cyanuric chloride.

3. The method for preparing an intumescent bio-based flame retardant according to claim 2, wherein: The method for preparing ethanolamine phytate comprises: Phytic acid and ethanolamine are subjected to esterification reaction, and after the esterification reaction is completed, tetrahydrofuran is added to the reaction system, and the mixture is stirred evenly and allowed to stand, and then liquid separation and extraction are performed to obtain ethanolamine phytate.

4. The method for preparing an intumescent bio-based flame retardant according to claim 3, wherein: The molar ratio of phytic acid to ethanolamine is 1:(2.3-2.5); And / or, the esterification reaction conditions include reacting at 120-130° C. for 2-3 hours, and condensing the reaction system during the reaction.

5. The method for preparing an intumescent bio-based flame retardant according to claim 2, wherein: At least one of the following conditions must be met: The cyanuric chloride is dissolved in tetrahydrofuran; The molar ratio of the ethanolamine phytate to cyanuric chloride is 1:(2.3-2.5); The conditions of the first nucleophilic substitution reaction include reacting at a temperature of 0-5°C for 2-3 hours, and adding an acid-binding agent during the reaction to control the pH value to be within the range of 6-7; The pH regulator and the acid binding agent are the same reagent, which is one of a 20-30wt% sodium carbonate aqueous solution, a 3-5wt% sodium hydroxide aqueous solution, and a 20-30wt% sodium bicarbonate aqueous solution; The ethanolamine phytate aqueous solution is added to the cyanuric chloride dropwise, and stirring is performed during the dropwise addition process; The washing adopts toluene; The vacuum drying comprises drying at 110-120° C. for 3-4 hours.

6. A method for preparing a flame retardant silk fabric, characterized in that: include: Dissolving the intumescent bio-based flame retardant according to claim 1 and anhydrous piperazine in water to obtain a mixed solution; immersing the silk fabric in the mixed solution, heating and shaking the mixture to cause the mixture to undergo a second nucleophilic substitution reaction, thereby obtaining a flame retardant finishing solution; The temperature of the flame retardant finishing liquid is continuously increased while maintaining an oscillation state to allow the third nucleophilic substitution reaction to proceed. After the reaction is completed, the silk fabric is taken out, rinsed, and naturally air-dried to obtain a flame retardant silk fabric. Wherein, the second nucleophilic substitution reaction is that the NH group of anhydrous piperazine replaces one chlorine in the intumescent bio-based flame retardant with the amino group and hydroxyl group of the silk fabric; The third nucleophilic substitution reaction is that the NH group of anhydrous piperazine replaces another chlorine in the intumescent bio-based flame retardant with the amino group and hydroxyl group of the silk fabric.

7. The method for preparing the flame-retardant silk fabric according to claim 6, characterized in that: The molar ratio of the intumescent bio-based flame retardant to anhydrous piperazine is 1:(1.3-1.5); And / or, the concentration of the intumescent bio-based flame retardant in the mixed solution is 50-100 g / L.

8. The method for preparing the flame-retardant silk fabric according to claim 6, characterized in that: The condition parameters of the second nucleophilic substitution reaction include shaking at 30-40° C. for 0.5-1 h, and adding an acid binding agent during the shaking process to control the pH value in the range of 6-7; And / or, the condition parameters of the third nucleophilic substitution reaction include shaking at 70-80° C. for 1-1.5 hours, and adding an acid binding agent during the shaking process to control the pH value within the range of 7-8.

9. The method for preparing the flame-retardant silk fabric according to claim 8, characterized in that: The acid binding agent is one of a 20-30 wt% sodium carbonate aqueous solution, a 3-5 wt% sodium hydroxide aqueous solution, and a 20-30 wt% sodium bicarbonate aqueous solution.

10. A flame retardant silk fabric, characterized in that: The flame-retardant silk fabric is prepared by the method for preparing the flame-retardant silk fabric according to any one of claims 6 to 9.

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