Phosphorus-sulfur synergistic flame retardant with high gas phase activity, durable flame-retardant nylon fabric and preparation method of durable flame-retardant nylon fabric

Abstract

The invention discloses a phosphorus-sulfur synergistic flame retardant with high gas phase activity, a durable flame-retardant nylon fabric and a preparation method of the flame-retardant nylon fabric, and relates to the technical field of flame-retardant nylon fabric preparation.The preparation method of the phosphorus-sulfur synergistic flame retardant comprises the steps that 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and polyepoxide are mixed and heated to be molten for a reaction, and the phosphorus-sulfur synergistic flame retardant is obtained; obtaining an intermediate after the reaction is finished; the intermediate and a thiophenethiol derivative are subjected to a click chemical reaction, and a 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative containing phosphorus and sulfur is obtained; the preparation method comprises the following steps: dissolving a 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative containing phosphorus and sulfur into a mixed solvent of ethanol and water, so as to obtain the phosphorus-sulfur synergistic flame retardant with high gas phase activity. The raw materials are safe and environmentally friendly, the preparation method is simple, and the prepared flame-retardant nylon fabric is excellent in flame retardance and washing resistance and free of pollution in the using process.

Description

Technical Field

[0001] This invention relates to a phosphorus-sulfur synergistic flame retardant with high gas phase activity, a durable flame-retardant nylon fabric and its preparation method, belonging to the technical field of flame-retardant nylon fabric preparation. Background Technology

[0002] Nylon fabrics, as an indispensable textile material, possess excellent comprehensive properties and are often used in specialized fields such as aerospace, transportation, military supplies, and electronics. However, nylon fabrics pose a high fire hazard, primarily due to their high flammability. During combustion, they release significant amounts of heat and produce a large number of molten droplets, increasing the likelihood of secondary fires. Therefore, to reduce the threat of fire and further expand the application areas of nylon fabrics, it is necessary to improve their flame-retardant and anti-dripping properties.

[0003] However, there are few reports on the flame-retardant and anti-dripping modifications of nylon fabrics. Surface modification methods, such as impregnation-baking, pad-drying-baking, coating, and impregnation, offer advantages in processing nylon fabrics and better meet the needs of factory production. Among surface modifications, improving the wash resistance of flame-retardant nylon fabrics remains a major challenge. Once used for a long time or exposed to open flames, nylon fabrics with low-durability flame-retardant properties are highly susceptible to fire, endangering people's lives, health, and property. To date, balancing the flame-retardant and anti-dripping properties of nylon fabrics, as well as improving their flame-retardant and wash resistance, remains two major hot topics and challenges in academia and industry.

[0004] Halogenated flame retardants, especially brominated compounds, dominate the commercial and industrial flame retardant market for nylon. They primarily enhance the flame retardant properties of nylon by eliminating free radicals such as H• and OH• in the gas phase, thereby hindering further combustion. However, the non-degradability and bioaccumulation of halogenated flame retardants lead to a series of environmental problems. Furthermore, the toxic hydrogen halides released during combustion pose a threat to human health. Therefore, the development of environmentally friendly and sustainable flame retardants has attracted significant attention from researchers.

[0005] Phosphorus plays a vital role in maintaining the life activities of organisms, and it is also a major flame retardant element. Currently, phosphorus-containing flame retardants such as ammonium polyphosphate, aluminum diethylphosphonate, melamine polyphosphate, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) exhibit good environmental protection and safety. Among them, DOPO has high gas-phase activity and possesses reactive pH bonds, allowing it to react with unsaturated double and triple bonds, aldehydes, ketones, epoxy groups, and other functional groups.

[0006] Existing research has developed several DOPO derivatives suitable for PA6 fabrics. For example, patent CN117510545A proposes a method for preparing phosphorus-containing DOPO derivatives and using them for functional modification of nylon materials. However, the limiting oxygen index of the modified nylon is only around 30%, and its flame retardant and wash resistance properties need further improvement. Furthermore, the film formation on the fabric surface significantly affects the physical properties of the fabric. Another example is patent CN116217623B, which proposes a phosphorus / nitrogen / sulfur synergistic DOPO derivative suitable for flame retardant modification of nylon. However, this also has limitations, such as poor limiting oxygen index and wash resistance of the modified nylon fabric.

[0007] Sulfur has been proven to be a synergist for phosphorus. The pyrolysis of sulfur-based flame retardants produces sulfur-containing gases, which act as fuel diluents and free radical scavengers in the gas phase, hindering the combustion reaction. Thiophene mercaptans and their derivatives are environmentally friendly sulfur-containing heterocyclic compounds commonly used in the preparation and processing of food, meat, vegetables, instant coffee, seasonings, breakfast cereals, and various other products. Studies have shown that thiophene derivatives are naturally found in various foods, including coffee, beef, pork, shrimp, papaya, and whiskey.

[0008] Currently, thiophene mercaptan derivatives are commonly used in the dyeing and processing of nylon fabrics, but flame retardant modification has not yet been applied. Furthermore, thiophene mercaptans are insoluble in water and typically have a pungent odor, limiting their application in the textile processing industry.

[0009] Patent CN119020998B proposes a method for preparing durable flame-retardant nylon 6 fabric based on reactive phosphorus-sulfur flame retardants. The method prepares phosphorus-sulfur flame retardants through the reaction of thiourea, p-hydroxybenzaldehyde and 3-bromopropene. However, since both bromine and aldehyde groups can react with amino groups, and the PH bond can react with C=C and C=N simultaneously, and there is a large steric hindrance in the reaction, the reaction is prone to producing a large number of byproducts, making purification difficult.

[0010] Therefore, there is an urgent need to develop a modifier that can significantly improve the limiting oxygen index, flame retardancy, and washability of nylon fabrics after modification. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a phosphorus-sulfur synergistic flame retardant with high gas-phase activity, durable flame-retardant nylon fabric, and its preparation method. The raw materials used are safe and environmentally friendly, and the preparation method is simple. This phosphorus-sulfur synergistic flame retardant exhibits extremely high gas-phase activity, and the modified nylon fabric possesses excellent flame-retardant and anti-dripping properties. Furthermore, the prepared flame retardant is reactive and can react with the terminal amino and carboxyl groups of nylon, compensating for the limited number of reaction sites in nylon. The prepared flame-retardant nylon fabric exhibits excellent washability.

[0012] To achieve the above objectives, the present invention is implemented using the following technical solution: In a first aspect, the present invention provides a method for preparing a phosphorus-sulfur synergistic flame retardant with high gas-phase activity, comprising: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and polycyclic oxide were mixed, heated to melt and reacted, and an intermediate was obtained after the reaction was completed. The intermediate was reacted with a thiophene thiol derivative by click chemistry to obtain a phosphorus-sulfur-containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative. A phosphorus-sulfur synergistic flame retardant with high gas-phase activity was obtained by dissolving a phosphorus-sulfur-containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative in a mixed solvent of ethanol and water.

[0013] Furthermore, the polyepoxide is a compound having at least three epoxy groups; And / or, the molar ratio of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the polyepoxide is (1~2):1; And / or, the heating and melting conditions include reacting at 140~160°C for 5~8 hours.

[0014] Furthermore, the polyepoxide is glycerol triglycidyl ether or pentaerythritol tetraglycidyl ether.

[0015] Furthermore, the thiophene thiol derivative is a compound having a thiophene group and a thiol group; And / or, the molar ratio of the intermediate to the thiophene thiol derivative is 1:(1~2); And / or, the reaction process of the click chemical reaction includes: At room temperature, the intermediate is dissolved in an organic solvent to obtain solution A; Solution B is obtained by dissolving a thiophene thiol derivative and a catalyst in an organic solvent, wherein the catalyst is 1,8-diazabicyclo[5.4.0]undec-7-ene; Mix solutions A and B and react for 0.5 to 2 hours.

[0016] Furthermore, the thiophene thiol derivative is one or more of 2-thiophene thiol, 5-phenylthiopheno[2,3-d]pyrimidine-4-thiol, 2-thiophene methylthiol, and thiophene-3-thiol.

[0017] Furthermore, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is in the range of 1:(1~2).

[0018] In a second aspect, the present invention also provides a phosphorus-sulfur synergistic flame retardant with high gas-phase activity, which is prepared by the preparation method of a phosphorus-sulfur synergistic flame retardant with high gas-phase activity as described in any one of the first aspects.

[0019] Thirdly, the present invention also provides a method for preparing durable flame-retardant nylon fabric, comprising: Adjust the pH value of the phosphorus-sulfur synergistic flame retardant with high gas phase activity as described in claim 7, immerse the nylon fabric in the phosphorus-sulfur synergistic flame retardant with high gas phase activity, and then bake it to obtain a durable flame-retardant nylon fabric.

[0020] Furthermore, the concentration of the highly gas-phase active phosphorus-sulfur synergistic flame retardant is 60-80 g / L; And / or, the pH value of the highly gas-phase active phosphorus-sulfur synergistic flame retardant is 3-5; And / or, the nylon fabric is one of nylon 6 fabric, nylon 66 fabric, and nylon 56 fabric; And / or, the immersion conditions include immersion at 70-80°C for 50-60 minutes; And / or, the baking conditions include baking at 140~160℃ for 10~20 minutes.

[0021] Fourthly, the present invention also provides a durable flame-retardant nylon fabric, which is prepared by the method for preparing durable flame-retardant nylon fabric as described in the third aspect.

[0022] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: This invention uses 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), polyepoxy compounds, and thiophene mercaptan derivatives as raw materials to prepare a highly gas-phase active phosphorus-sulfur synergistic flame retardant through nucleophilic addition reaction and click chemistry. This flame retardant exhibits high gas-phase activity, generating phosphorus-containing fragments such as PO•, PO2•, and HPO2, as well as SO2, during combustion. These fragments are released into the combustion zone, further capturing free radicals required for combustion and inhibiting chain reactions. Simultaneously, SO2 can dilute the concentration of oxygen and combustible gases required for combustion, hindering combustion and thus achieving a flame-retardant effect. The flame retardant prepared by this invention has reactive epoxy groups. During the baking process, the epoxy groups can covalently bond with the carboxyl and amino groups of nylon, making full use of the limited active sites on nylon, thereby improving the flame retardant and washability of nylon fabrics. The flame-retardant properties of the flame-retardant nylon fabric prepared by this invention are as follows: damaged length 10.0~12.5cm, limiting oxygen index up to 40.0%, average effective heat of combustion reduced by up to 67%, no molten dripping during combustion, and no molten dripping even after 45~55 water washes. The DOPO used in this invention is an environmentally friendly reagent, and the thiophene mercaptan derivative is a natural product without the pungent odor of thiophene mercaptan. Therefore, the prepared flame retardant is an environmentally friendly flame retardant. Attached Figure Description

[0023] Figure 1 This is a schematic flowchart of a method for preparing a phosphorus-sulfur synergistic flame retardant with high gas-phase activity, as shown in one embodiment of the present invention. Figure 2 The intermediate prepared in Example 1 of the present invention 1 Schematic diagram of H NMR spectrum; Figure 3 The phosphorus-sulfur synergistic flame retardant with high gas-phase activity prepared in Example 1 of this invention... 1 Schematic diagram of H NMR spectrum; Figure 4 The phosphorus-sulfur synergistic flame retardant with high gas-phase activity prepared in Example 2 of this invention 31 Schematic diagram of P NMR spectrum; Figure 5 A schematic diagram of the residual char morphology of the original nylon 66 fabric provided in Comparative Example 1 of the present invention; Figure 6 This is a schematic diagram of the residual char morphology of the durable flame-retardant nylon 66 fabric prepared in Example 3 of the present invention. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention. Example 1

[0025] This invention provides a method for preparing durable flame-retardant nylon 56 fabric, comprising the following steps: Step 1: Preparation of the intermediate via a nucleophilic addition reaction between glycerol triglycidyl ether and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO): Combination Figure 10.1 mol of glycerol triglycidyl ether was added to a three-necked flask equipped with a condenser and a nitrogen valve. When the system temperature was raised to 160 °C, 0.1 mol of DOPO powder was added in small amounts several times. The reaction was continued for 6 h under constant stirring and nitrogen protection to obtain a transparent colloidal intermediate with a yield of 95.8%.

[0026] The proton spectrum of the intermediate is as follows Figure 2 As shown, the peaks at 7.3-8.2 ppm correspond to protons in the aromatic ring structure, while the peaks at 5.3 and 4.0 ppm correspond to protons in the -CH bond. The characteristic peak at 4.1 ppm corresponds to a proton in the p-CH2 bond, obtained from the reaction of the PH bond and the epoxy group. The proton peak in the -OH bond formed by ring opening of the epoxy group is located at 2.2 ppm. The peaks at 3.5 and 3.1 ppm are caused by the -CH bond in the epoxy group, and the peaks at 2.7 and 2.4 ppm correspond to the -CH2 bond in the epoxy group, indicating the presence of unreacted epoxy groups in the intermediate.

[0027] Step 2: Prepare the target flame retardant via thiol-epoxy click chemistry: 0.02 mol of the intermediate and 15 mL of tetrahydrofuran (THF) were added to a round-bottom flask equipped with a mechanical stirrer and stirred at room temperature. Simultaneously, 0.04 mol of 2-thiophenethiol and 5% mol of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) were mixed in 10 mL of THF. When the intermediate and THF were completely miscible, the above mixture was added, and stirring continued for 2 h. After the reaction was complete, THF was removed by rotary evaporation, and the target flame retardant was further obtained by ethanol dialyze and vacuum drying, yielding a dark green gel-like substance with a yield of approximately 99.6%.

[0028] The hydrogen spectrum of the target flame retardant is as follows: Figure 3 As shown, due to the introduction of 2-thiophene mercaptan, the phosphorus-sulfur synergistic flame retardant with high gas-phase activity... 1 Several new signal peaks appeared in the H spectrum. The signal peak at 7.2-7.1 ppm corresponds to the proton in the =CH-CH= bond of the thiophene group; while the signal peak at 7.8 ppm corresponds to the proton in the S-CH=C structure of thiophene. In addition, the signal peaks at 1.6 and 1.1 ppm are caused by the CH-OH group, and the signal peak at 2.9 ppm corresponds to the proton in the S-CH structure, indicating that a click chemistry reaction occurred in the thiol-epoxy group.

[0029] The third step is to dissolve the target flame retardant in a mixed solvent of ethanol and water (volume ratio of ethanol to water is 2:3), adjust the pH with acetic acid, and prepare a flame retardant solution with a concentration of 60 g / L and a pH value of 4.5.

[0030] Step 4: Prepare flame-retardant nylon 56 fabric using the impregnation-baking method: The nylon 56 fabric was immersed in the flame retardant solution obtained in step (2) for 50 min at an immersion temperature of 80 °C. After the reaction was completed, the fabric was removed and baked at 150 °C for 20 min to obtain a durable flame retardant nylon 56 fabric.

[0031] The following tests were conducted on the performance of the durable flame-retardant nylon 56 fabric prepared in Example 1. The specific test methods included testing the damaged length of the nylon fabric using ASTM D6413-15, testing the dripping behavior of the nylon fabric using ASTM D6413-15 to obtain the anti-drip performance, testing the limiting oxygen index of the nylon fabric using ASTM D2863-17, washing the nylon fabric using the AATCC 61-2013 washing standard to obtain the wash resistance, and testing the average effective heat of combustion of the nylon fabric using ISO 5660-1 to obtain the fire safety.

[0032] The performance test results of the durable flame-retardant nylon 56 fabric prepared in this embodiment are as follows: damaged length 12.5 cm, limiting oxygen index 35.5%, no molten dripping during combustion, and no molten dripping after 45 washes. Furthermore, the average effective heat of combustion is related to the gas-phase activity of the flame retardant; the lower the average effective heat of combustion, the stronger the gas-phase activity. The average effective heat of combustion of flame-retardant nylon 56 is 18.4 MJ / kg, which is about 46.4% lower than that of unmodified nylon 56, indicating that the flame retardant has high gas-phase activity. Example 2

[0033] This invention provides a method for preparing durable flame-retardant nylon 6 fabric, comprising the following steps: Step 1: Preparation of the intermediate via nucleophilic addition reaction between pentaerythritol tetraglycidyl ether and DOPO: 0.1 mol pentaerythritol tetraglycidyl ether was added to a three-necked flask equipped with a condenser and a nitrogen valve. When the system temperature reached 140 °C, 0.1 mol DOPO powder was added in small, repeated additions, and the reaction was continued for 8 h under constant stirring and nitrogen protection to obtain a transparent colloidal intermediate with a yield of 96.5%.

[0034] Step 2: Prepare the target flame retardant via thiol-epoxy click chemistry: 0.02 mol of the intermediate and 20 mL of THF were added to a round-bottom flask equipped with a mechanical stirrer and stirred at room temperature. Simultaneously, 0.02 mol of thiophene-3-thiol and 5% mol of DBU were mixed in 10 mL of THF. When the intermediate and THF were completely miscible, the above mixture was added, and stirring continued for 1.5 h. After the reaction was complete, THF was removed by rotary evaporation, and the target flame retardant was further obtained by ethanol dialyze and vacuum drying, yielding a dark green gel-like substance with a yield of approximately 98.4%.

[0035] Target flame retardant 31 p NMR spectrum as shown Figure 4 As shown, Figure 4 The presence of a vibrational peak indicates that phosphorus exists in only one chemical environment, and this peak position is completely inconsistent with that of phosphorus in DOPO. This result strongly confirms the successful preparation of a phosphorus-sulfur synergistic flame retardant with high gas-phase activity.

[0036] The third step is to dissolve the target flame retardant in a mixed solvent of ethanol and water (volume ratio of ethanol to water is 1:2), adjust the pH with acetic acid, and prepare a flame retardant solution with a concentration of 70 g / L and a pH value of 5.0.

[0037] Step 4: Prepare flame-retardant nylon 6 fabric using the impregnation-baking method: The nylon 6 fabric was immersed in the flame retardant solution obtained in step (2) for 60 min at an immersion temperature of 70 °C. After the reaction was completed, it was taken out and baked at 160 °C for 10 min to finally obtain durable flame retardant nylon 6 fabric.

[0038] The performance test results of the durable flame-retardant nylon 6 fabric prepared in this embodiment (test method as described in Example 1) are as follows: damaged length 11.0 cm, limiting oxygen index 38.9%, no molten dripping during combustion, and no molten dripping after 55 washes during combustion. The average effective heat of combustion of flame-retardant nylon 6 is 15.3 MJ / kg, which is about 59.7% lower than that of unmodified nylon 6, indicating that the flame retardant has high gas-phase activity. Example 3

[0039] This embodiment provides a method for preparing durable flame-retardant nylon 66 fabric, including the following steps: Step 1: Preparation of the intermediate via nucleophilic addition reaction between pentaerythritol tetraglycidyl ether and DOPO: 0.1 mol pentaerythritol tetraglycidyl ether was added to a three-necked flask equipped with a condenser and a nitrogen valve. When the system temperature reached 140 °C, 0.2 mol DOPO powder was added in small, repeated additions, and the reaction was continued for 8 h under constant stirring and nitrogen protection to obtain a transparent colloidal intermediate with a yield of 97.4%.

[0040] Step 2: Prepare the target flame retardant via thiol-epoxy click chemistry: 0.02 mol of the intermediate and 15 mL of THF were added to a round-bottom flask equipped with a mechanical stirrer and stirred at room temperature. Simultaneously, 0.02 mol of 2-thiophenemethylthiol and 5% mol of DBU were mixed in 10 mL of THF. When the intermediate and THF were completely miscible, the above mixture was added, and stirring continued for 0.5 h. After the reaction was complete, THF was removed by rotary evaporation, and the target flame retardant was further obtained by ethanol dialyze and vacuum drying, yielding a dark green gel-like substance with a yield of approximately 96.9%.

[0041] The third step is to dissolve the target flame retardant in a mixed solvent of ethanol and water (volume ratio of ethanol to water is 1:1), adjust the pH with acetic acid, and prepare a flame retardant solution with a concentration of 80 g / L and a pH value of 3.0.

[0042] Step 4: Prepare flame-retardant nylon 66 fabric using the impregnation-baking method: The nylon 66 fabric was immersed in the flame retardant solution obtained in step (2) for 50 min at an immersion temperature of 80 °C. After the reaction was completed, the fabric was removed and baked at 140 °C for 50 min to obtain a durable flame retardant nylon 66 fabric.

[0043] The performance test results of the durable flame-retardant nylon 66 fabric prepared in this embodiment (test method as described in Example 1) are as follows: The damaged length was 10.0 cm, the limiting oxygen index was 40.0%, and no molten droplets fell during combustion. Even after 50 water washes, no molten droplets fell during combustion. The average effective heat of combustion of flame-retardant nylon 66 was 14.1 MJ / kg, which was reduced by about 66.7% compared with unmodified nylon 66, indicating that the flame retardant has high gas-phase activity. Example 4

[0044] This embodiment provides a method for preparing durable flame-retardant nylon 6 fabric, including the following steps: Step 1: Preparation of the intermediate via nucleophilic addition reaction between glycerol triglycidyl ether and DOPO: 0.2 mol of glycerol triglycidyl ether was added to a three-necked flask equipped with a condenser and a nitrogen valve. Once the system temperature reached 150 °C, 0.2 mol of DOPO powder was added in small, repeated additions, and the reaction was continued for 6 h under constant stirring and nitrogen protection to obtain a transparent colloidal intermediate with a yield of 95.3%.

[0045] Step 2: Prepare the target flame retardant via thiol-epoxy click chemistry: 0.04 mol of the intermediate and 25 mL of THF were added to a round-bottom flask equipped with a mechanical stirrer and stirred at room temperature. Simultaneously, 0.04 mol of 5-phenylthiopheno[2,3-d]pyrimidine-4-thiol and 5% mol of DBU were mixed in 10 mL of THF. When the intermediate and THF were completely miscible, the above mixture was added, and stirring continued for 1 h. After the reaction was complete, THF was removed by rotary evaporation, and the target flame retardant was further obtained by ethanol dialyze and vacuum drying, with a yield of approximately 99.1%.

[0046] The third step is to dissolve the target flame retardant in a mixed solvent of ethanol and water (volume ratio of ethanol to water is 1:2), adjust the pH with acetic acid, and prepare a flame retardant solution with a concentration of 75 g / L and a pH value of 3.5.

[0047] Step 4: Prepare flame-retardant nylon 6 fabric using the impregnation-baking method: The nylon 6 fabric was immersed in the flame retardant solution obtained in step (2) for 55 min at an immersion temperature of 75 °C. After the reaction was completed, it was removed and baked at 155 °C for 15 min to finally obtain durable flame retardant nylon 6 fabric.

[0048] The performance test results of the durable flame-retardant nylon 6 fabric prepared in this embodiment (test method as described in Example 1) are as follows: The damaged length was 10.5 cm, the limiting oxygen index was 39.4%, and no molten droplets fell during combustion. Even after 50 water washes, no molten droplets fell during combustion. The average effective heat of combustion of flame-retardant nylon 6 was 16.8 MJ / kg, which was about 50.7% lower than that of unmodified nylon 6, indicating that the flame retardant has high gas-phase activity.

[0049] Comparative Example 1: This comparative example provides a virgin nylon 66 fabric that has not been treated with the target flame retardant prepared in Example 3.

[0050] The durable flame-retardant nylon 66 fabric prepared in Example 3 and the original nylon 66 fabric prepared in Comparative Example 1 were burned, and the morphologies of the resulting char residues are shown below. Figure 6 , Figure 5As shown in the comparison, the original nylon 66 fabric left only a small amount of residue after burning, and the surface of these residues was relatively intact. The surface of the durable flame-retardant nylon 66 fabric showed numerous small pores, which act as channels for volatile gases to enter the combustion zone. This phenomenon is related to the gas-phase mechanism.

[0051] This is because the flame retardant decomposes to form SO2, phosphorus-oxygen free radicals, and a large amount of volatile gases, which accumulate internally until they penetrate the surface of the residue and are released into the gas phase. When SO2 and phosphorus-oxygen free radicals enter the combustion zone, the latter can quench combustion by capturing the free radicals required for combustion. The former is a dual-effect molecule; it can both capture the free radicals required for combustion and act as a non-combustible gas to dilute the concentration of oxygen and combustible gases, thereby inhibiting the combustion reaction. Furthermore, the densely packed pores indicate that this flame retardant has extremely high gas-phase activity.

[0052] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a phosphorus-sulfur synergistic flame retardant with high gas-phase activity, characterized in that, include: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and polycyclic oxide were mixed, heated to melt and reacted, and an intermediate was obtained after the reaction was completed. The intermediate was reacted with a thiophene thiol derivative by click chemistry to obtain a phosphorus-sulfur-containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative. A phosphorus-sulfur synergistic flame retardant with high gas-phase activity was obtained by dissolving a phosphorus-sulfur-containing 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide derivative in a mixed solvent of ethanol and water.

2. The method for preparing a highly gas-phase active phosphorus-sulfur synergistic flame retardant according to claim 1, characterized in that, The polyepoxide is a compound having at least three epoxy groups; And / or, the molar ratio of the 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide to the polyepoxide is (1~2):1; And / or, the heating and melting conditions include reacting at 140~160°C for 5~8 hours.

3. The method for preparing a highly gas-phase active phosphorus-sulfur synergistic flame retardant according to claim 2, characterized in that, The polyepoxide is glycerol triglycidyl ether or pentaerythritol tetraglycidyl ether.

4. The method for preparing the highly gas-phase active phosphorus-sulfur synergistic flame retardant according to claim 1, characterized in that, The thiophene thiol derivative is a compound having a thiophene group and a thiol group; And / or, the molar ratio of the intermediate to the thiophene thiol derivative is 1:(1~2); And / or, the reaction process of the click chemical reaction includes: At room temperature, the intermediate is dissolved in an organic solvent to obtain solution A; Solution B is obtained by dissolving a thiophene thiol derivative and a catalyst in an organic solvent, wherein the catalyst is 1,8-diazabicyclo[5.4.0]undec-7-ene; Mix solutions A and B and react for 0.5 to 2 hours.

5. The method for preparing a phosphorus-sulfur synergistic flame retardant with high gas-phase activity according to claim 4, characterized in that, The thiophene thiol derivative is one or more of 2-thiophene thiol, 5-phenylthiopheno[2,3-d]pyrimidine-4-thiol, 2-thiophene methyl thiol and thiophene-3-thiol.

6. The method for preparing a highly gas-phase active phosphorus-sulfur synergistic flame retardant according to claim 1, characterized in that, The volume ratio of ethanol to water in the mixed solvent of ethanol and water is in the range of 1:(1~2).

7. A phosphorus-sulfur synergistic flame retardant with high gas-phase activity, characterized in that, It is prepared by the method for preparing a phosphorus-sulfur synergistic flame retardant with high gas phase activity as described in any one of claims 1 to 6.

8. A method for preparing a durable flame-retardant nylon fabric, characterized in that, include: Adjust the pH value of the phosphorus-sulfur synergistic flame retardant with high gas phase activity as described in claim 7, immerse the nylon fabric in the phosphorus-sulfur synergistic flame retardant with high gas phase activity, and then bake it to obtain a durable flame-retardant nylon fabric.

9. The method for preparing durable flame-retardant nylon fabric according to claim 8, characterized in that, The concentration of the highly gas-phase active phosphorus-sulfur synergistic flame retardant is 60~80g / L; And / or, the pH value of the highly gas-phase active phosphorus-sulfur synergistic flame retardant is 3-5; And / or, the nylon fabric is one of nylon 6 fabric, nylon 66 fabric, and nylon 56 fabric; And / or, the immersion conditions include immersion at 70-80°C for 50-60 minutes; And / or, the baking conditions include baking at 140~160℃ for 10~20 minutes.

10. A durable flame-retardant nylon fabric, characterized in that, It is prepared by the method for preparing durable flame-retardant nylon fabric as described in claim 8 or 9.

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