Preparation method of durable flame-retardant smoke-suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardant

Abstract

The invention relates to a preparation method of a durable flame-retardant smoke-suppressing cotton fabric based on a phosphorus / nitrogen / silicon flame retardant, which comprises the following steps: dissolving diethylenetriaminepenta (methylene phosphonic acid) and tris (2, 3-epoxypropyl) isocyanurate in a solvent to obtain a mixed solution, dropwise adding (3-glycidoxy) trimethoxysilane into the mixed solution at a rate of 0.5-1mL / min, reacting at a temperature of 60-80 DEG C for 1-2 hours, and then adding a catalyst to obtain the flame-retardant smoke-suppressing cotton fabric based on the phosphorus / nitrogen / silicon flame retardant. Reacting to obtain a phosphorus / nitrogen / silicon flame retardant solution; secondly, dicyandiamide is added into the phosphorus / nitrogen / silicon flame retardant solution, then ammonia water is added to adjust the pH to 6-8, and flame-retardant finishing liquid is obtained; and finally, immersing the cotton fabric into the flame-retardant finishing liquid, and preparing the durable flame-retardant smoke-suppressing cotton fabric based on the phosphorus / nitrogen / silicon flame retardant through a rolling and baking process. The product prepared by the method disclosed by the invention has excellent flame-retardant durability and smoke suppression performance.

Description

Technical Field

[0001] The invention belongs to the technical field of flame-retardant and smoke-suppressant cotton fabrics, and relates to a method for preparing a durable flame-retardant and smoke-suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants. Background Art

[0002] Cotton fabrics are widely used in clothing, home furnishing, medical and health care, industrial products and other fields due to their softness, warmth retention, moisture absorption and breathability, easy dyeing and finishing, alkali resistance and light resistance. However, due to the flammable nature of cotton fabrics, especially in high-risk industries such as metallurgy, fire protection, chemical industry and home textile products, there is an increasing demand for flame retardant treatment of cotton fabrics to improve safety and reduce fire risks. With the continuous increase in market demand, durable flame retardant cotton fabrics have become an important research direction. Such products can maintain their flame retardant properties even after multiple washings.

[0003] In response to this demand, some studies have been conducted. Reference 1 (Preparation of durable and efficient phosphorus / nitrogen synergistic flame retardant and its application on cotton fabrics [J]. Journal of Textile Research, 2024, 45(7): 121-129.) An intumescent phosphorus / nitrogen synergistic flame retardant (2-hydroxyethyl) phosphoramide ammonium salt (AHPA) was prepared using phosphorus pentoxide and ethanolamine as raw materials. The flame-retardant cotton fabric still had good flame retardant properties after 50 washes, which is a durable flame retardant finish. However, the smoke release performance of the flame-retardant cotton fabric increased significantly, resulting in a greatly increased fire hazard.

[0004] Reference 2 (Synthesis and flame retardant properties of new flame retardant containing ammonium phosphonate active group for cotton [D]. Chongqing: Southwest University, 2017.) The flame retardant diethylene triamine penta methylene phosphonic acid (ADTPMPA) was synthesized by reaction with diethylene triamine penta methylene phosphonic acid as raw material. The finished cotton fabric can withstand 30 washes and is a semi-durable flame retardant fabric. This is because the degree of crosslinking between diethylene triamine penta methylene phosphonic acid and cotton fiber is limited, and its flame retardant durability needs to be further improved; and the smoke release of flame retardant cotton fabric also increased significantly, because the carbonization of modified cotton fabric is still poor, and more smoke is generated through smoldering.

[0005] It is worth noting that diethylenetriamine penta (methylenephosphonic acid) has been widely used in many fields such as textile printing and dyeing due to its advantages such as chemical stability, high temperature resistance, high solubility and environmental friendliness. This compound meets current environmental protection requirements due to its low toxicity and easy biodegradability, and the market demand continues to grow. Therefore, it is of great significance to develop durable flame-retardant functional cotton fabrics using diethylenetriamine penta (methylenephosphonic acid) to improve the fire safety protection performance of cotton fabrics.

[0006] Therefore, it is of great significance to study a method for preparing a durable flame retardant and smoke-suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardants to solve the problems existing in the prior art. Summary of the invention

[0007] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for preparing a durable flame retardant and smoke suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardants.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] The preparation method of durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant comprises the following steps:

[0010] (1) dissolving diethylenetriamine penta (methylene phosphonic acid) and tri (2,3-epoxypropyl) isocyanurate in a solvent to obtain a mixed solution, and then adding (3-glycidyl propoxy) trimethoxy silane dropwise to the mixed solution at a rate of 0.5-1 mL / min to react to obtain a phosphorus / nitrogen / silicon flame retardant solution;

[0011] (2) adding dicyandiamide to the phosphorus / nitrogen / silicon flame retardant solution obtained in step (1), and then adding ammonia water to adjust the pH to 6-8 to obtain a flame retardant finishing liquid; adjusting the pH to 6-8 so that part of the phosphate groups of diethylenetriaminepenta(methylenephosphonic acid) are converted into ammonium phosphate groups, which is helpful for the subsequent covalent bond grafting reaction;

[0012] (3) The cotton fabric is immersed in a flame retardant finishing liquid and subjected to a rolling and baking process to obtain a durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants.

[0013] As the preferred technical solution:

[0014] In the method for preparing the durable flame retardant and smoke suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardants as described above, the solvent in step (1) is a mixture of water and N,N-dimethylformamide, and the volume proportion of N,N-dimethylformamide in the mixture is 50-60%.

[0015] In the method for preparing a durable flame retardant and smoke-suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardant as described above, in the phosphorus / nitrogen / silicon flame retardant solution of step (1), the content of diethylenetriaminepenta(methylenephosphonic acid) is 75-100 g / L, the content of tri(2,3-epoxypropyl)isocyanurate is 40-60 g / L, and the content of (3-glycidylpropoxy)trimethoxysilane is 20-40 g / L.

[0016] Diethylenetriaminepenta(methylenephosphonic acid) is the main flame retardant component. The higher the dosage, the better the flame retardant performance. However, too high dosage will be a waste.

[0017] (3-Glycidylpropoxy)trimethoxysilane is easily soluble in N,N-dimethylformamide. Gradually adding (3-glycidylpropoxy)trimethoxysilane helps to promote the hydrolysis and condensation reaction of (3-glycidylpropoxy)trimethoxysilane after contacting with water to generate silica sol.

[0018] In the method for preparing the durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants as described above, the reaction temperature in step (1) is 75-85° C., and the reaction time after the (3-glycidylpropoxy)trimethoxysilane solution is added is 2-3 hours.

[0019] In the method for preparing the durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants as described above, the content of dicyandiamide in the flame retardant finishing liquid of step (2) is 30-50 g / L.

[0020] In the method for preparing the durable flame retardant and smoke suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardants as described above, the rolling and baking process in step (3) is specifically as follows: a two-immersion and two-rolling method is adopted, and the rolling rate is 90-110%; the pre-baking temperature is 75-85°C, and the time is 2-3 minutes; the baking temperature is 165-175°C, and the time is 2-3 minutes.

[0021] The preparation method of the durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant as described above, the durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant has a limiting oxygen index of not less than 31.0%, a damaged length of not more than 8.7 cm, and a total smoke release of not more than 0.10 m 2 After 50 washes, the damaged length is still no more than 14.0 cm (the limiting oxygen index of unmodified cotton fabric is 18.2%, the damaged length is 30 cm, and the total smoke release is 0.15 m 2 ).

[0022] The principle of the present invention is:

[0023] The phosphate group of diethylenetriamine penta(methylenephosphonic acid) can undergo an esterification cross-linking reaction with the hydroxyl group of cotton fiber under the catalysis of dicyandiamide, thereby grafting the phosphorus-containing flame retardant group onto the cotton fiber. However, the degree of this reaction is limited, and it is difficult to graft a sufficient amount of phosphorus-containing flame retardant onto cotton fabrics, and it is difficult to provide long-lasting flame retardant properties. In addition, the phosphorus-containing flame retardant alone causes the smoke release of cotton fabrics to increase, thereby increasing the fire hazard.

[0024] In the present invention, tri(2,3-epoxypropyl)isocyanurate contains three epoxy groups, which can undergo a ring-opening addition reaction with the phosphate of diethylenetriaminepenta(methylenephosphonic acid), and the silanol groups hydrolyzed from (3-glycidylpropoxy)trimethoxysilane undergo a hydrolysis condensation reaction in an aqueous solution to generate a network-like silica sol. The epoxy groups and silanol groups of (3-glycidylpropoxy)trimethoxysilane can react with the phosphate of diethylenetriaminepenta(methylenephosphonic acid) after hydrolysis, so that a new network-like phosphorus / nitrogen / silicon flame retardant is formed between the silicon-containing network, diethylenetriaminepenta(methylenephosphonic acid) and tri(2,3-epoxypropyl)isocyanurate.

[0025] like Figure 1 As shown, under the catalysis of dicyandiamide, the phosphate group in the network phosphorus / nitrogen / silicon flame retardant can undergo an esterification cross-linking reaction with the hydroxyl group of the cotton fiber, and the epoxy group of tri(2,3-epoxypropyl)isocyanurate in the network phosphorus / nitrogen / silicon flame retardant can also undergo an esterification cross-linking reaction with the hydroxyl group of the cotton fiber. Therefore, the network phosphorus / nitrogen / silicon flame retardant can react with the cotton fiber through two covalent bonds. Compared with a single phosphate covalent bond, the cross-linking reaction described in the present invention has a high degree of cross-linking and a high grafting amount, which helps to further improve the water wash resistance;

[0026] In addition, the phosphate group in the network phosphorus / nitrogen / silicon flame retardant acts as an acid source, the nitrogen-containing group of tri(2,3-epoxypropyl)isocyanurate acts as a gas source, and the polycyclic structure of tri(2,3-epoxypropyl)isocyanurate acts as a carbon source, which are organically combined to construct an intumescent flame retardant system with high flame retardant efficiency. The silicon-containing flame retardant group helps to further improve the flame retardant properties and plays a role in suppressing the release of smoke. Therefore, the cotton fabric modified by the coating has excellent flame retardant and smoke suppression properties.

[0027] Beneficial effects:

[0028] (1) A method for preparing a durable flame-retardant and smoke-suppressing cotton fabric based on a phosphorus / nitrogen / silicon flame retardant of the present invention, wherein a network-like phosphorus / nitrogen / silicon flame retardant is formed by reacting tri(2,3-epoxypropyl)isocyanurate, (3-glycidylpropoxy)trimethoxysilane and diethylenetriaminepenta(methylenephosphonic acid), and the flame retardant is highly cross-linked with cotton fibers under the catalysis of dicyandiamide to improve the water-washing resistance;

[0029] (2) The present invention provides a method for preparing a durable flame retardant and smoke suppressant cotton fabric based on a phosphorus / nitrogen / silicon flame retardant. The phosphate group in the network phosphorus / nitrogen / silicon flame retardant acts as an acid source, the nitrogen-containing group of tri(2,3-epoxypropyl)isocyanurate acts as a gas source, and the polycyclic structure of tri(2,3-epoxypropyl)isocyanurate acts as a carbon source. They are organically combined to construct an intumescent flame retardant system with high flame retardant efficiency. The silicon-containing flame retardant group helps to further improve the flame retardant performance and has the ability to suppress smoke release. Therefore, the durable flame retardant and smoke suppressant cotton fabric has excellent flame retardant and smoke suppressant properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the cross-linking mechanism of network phosphorus / nitrogen / silicon flame retardant and cotton fabric. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0032] The test methods involved in the performance indicators in the embodiments and comparative examples of the present invention are as follows:

[0033] Limiting oxygen index: Tested in accordance with GB / T 5454-1997 "Oxygen Index Method for Textile Combustion Performance Test".

[0034] Damage length: measured in accordance with GB / T 5455-2014 "Determination of smoldering and afterflaming time of damage length in vertical direction of burning performance of textiles".

[0035] Total smoke release: The total smoke release of the sample was tested and characterized using a VOUCH 6810 cone calorimeter in accordance with ISO 5660-1 standard.

[0036] Damage length after 50 washes: First wash the fabric 50 times with water according to AATCC 61-2013 "Accelerated test for color fastness to household and commercial washing" standard, and then test the damage length of the fabric with reference to GB / T 5455-2014 "Determination of damage length in vertical direction, smoldering and afterflaming time of textile combustion performance" standard.

[0037] Example 1

[0038] The preparation method of durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant, the specific steps are as follows:

[0039] (1) dissolving diethylenetriaminepenta(methylenephosphonic acid) and tri(2,3-epoxypropyl)isocyanurate in a solvent to obtain a mixed solution, then adding (3-glycidylpropoxy)trimethoxysilane dropwise to the mixed solution at a rate of 0.5 mL / min, and reacting at a temperature of 85°C for 3 h to obtain a phosphorus / nitrogen / silicon flame retardant solution;

[0040] The solvent is a mixture of water and N,N-dimethylformamide, and the volume proportion of N,N-dimethylformamide in the mixture is 50%; in the phosphorus / nitrogen / silicon flame retardant solution, the content of diethylenetriamine penta (methylene phosphonic acid) is 75 g / L, the content of tris (2,3-epoxypropyl) isocyanurate is 40 g / L, and the content of (3-glycidyl propoxy) trimethoxy silane is 20 g / L;

[0041] (2) adding dicyandiamide to the phosphorus / nitrogen / silicon flame retardant solution obtained in step (1), and then adding ammonia water to adjust the pH to 6 to obtain a flame retardant finishing liquid with a dicyandiamide content of 30 g / L;

[0042] (3) immersing the cotton fabric in a flame retardant finishing liquid, performing a double immersion and double rolling treatment, controlling the rolling rate to be 90%, and then performing a baking treatment to obtain a durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant;

[0043] The specific baking process is as follows: pre-baking temperature is 85°C, time is 2 minutes; baking temperature is 165°C, time is 3 minutes.

[0044] The resulting durable flame retardant and smoke-suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardants has a limiting oxygen index of 31%, a damage length of 8.7 cm, and a total smoke release of 0.1 m 2 After 50 washes, the damaged length was 14 cm.

[0045] Comparative Example 1

[0046] A method for preparing a modified cotton fabric is basically the same as that of Example 1, except that tri(2,3-epoxypropyl)isocyanurate is not added in step (1).

[0047] The final modified cotton fabric had a limiting oxygen index of 29.9%, a damaged length of 9.8 cm, and a total smoke release of 0.12 m 2 After 40 washes, the damaged length was 30cm.

[0048] By comparing Comparative Example 1 with Example 1, it can be found that when tri(2,3-epoxypropyl)isocyanurate is not added, the flame retardant properties, smoke suppression properties and water washing resistance of the modified cotton fabric are reduced. This is because tri(2,3-epoxypropyl)isocyanurate plays a cross-linking role, and its polycyclic structure acts as a carbon source. When tri(2,3-epoxypropyl)isocyanurate is not added, firstly, the flame retardant properties are deteriorated due to the inability to play a synergistic flame retardant effect, and secondly, cross-linking cannot be generated, which leads to easy loss during the washing process, resulting in reduced water washing resistance.

[0049] Comparative Example 2

[0050] A method for preparing a durable flame retardant and smoke suppressant cotton fabric is basically the same as that of Example 1, except that (3-glycidylpropoxy)trimethoxysilane is not added.

[0051] The resulting durable flame retardant and smoke suppression cotton fabric has a limiting oxygen index of 29.1%, a damaged length of 10.3 cm, and a total smoke release of 0.17 m 2 After 40 washes, the damaged length was 30cm.

[0052] By comparing Comparative Example 2 with Example 1, it can be found that when (3-glycidylpropoxy)trimethoxysilane is not added, the flame retardant properties, smoke suppression properties and water washability of the durable flame retardant and smoke suppression cotton fabric are reduced. This is because the silicon-containing flame retardant group helps to further improve the flame retardant properties and has the ability to suppress smoke release.

[0053] Example 2

[0054] The preparation method of durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant, the specific steps are as follows:

[0055] (1) dissolving diethylenetriaminepenta(methylenephosphonic acid) and tri(2,3-epoxypropyl)isocyanurate in a solvent to obtain a mixed solution, then adding (3-glycidylpropoxy)trimethoxysilane dropwise to the mixed solution at a rate of 0.7 mL / min, and reacting at a temperature of 80° C. for 2.85 h to obtain a phosphorus / nitrogen / silicon flame retardant solution;

[0056] The solvent is a mixture of water and N,N-dimethylformamide, and the volume proportion of N,N-dimethylformamide in the mixture is 55%; in the phosphorus / nitrogen / silicon flame retardant solution, the content of diethylenetriamine penta (methylene phosphonic acid) is 85 g / L, the content of tris (2,3-epoxypropyl) isocyanurate is 45 g / L, and the content of (3-glycidyl propoxy) trimethoxy silane is 25 g / L;

[0057] (2) adding dicyandiamide to the phosphorus / nitrogen / silicon flame retardant solution obtained in step (1), and then adding ammonia water to adjust the pH to 6.5 to obtain a flame retardant finishing liquid with a dicyandiamide content of 35 g / L;

[0058] (3) immersing the cotton fabric in a flame retardant finishing liquid, performing a double immersion and double rolling treatment, controlling the rolling rate to be 95%, and then performing a baking treatment to obtain a durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant;

[0059] The specific baking process is as follows: pre-baking temperature is 80°C, time is 2.5 minutes; baking temperature is 168°C, time is 2.75 minutes.

[0060] The final durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardants has a limiting oxygen index of 31.6%, a damaged length of 8.3 cm, and a total smoke release of 0.08 m 2 After 50 washes, the damaged length was 13.5 cm.

[0061] Example 3

[0062] The preparation method of durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant, the specific steps are as follows:

[0063] (1) dissolving diethylenetriaminepenta(methylenephosphonic acid) and tri(2,3-epoxypropyl)isocyanurate in a solvent to obtain a mixed solution, then adding (3-glycidylpropoxy)trimethoxysilane dropwise to the mixed solution at a rate of 0.9 mL / min, and reacting at a temperature of 78°C for 2.5 h to obtain a phosphorus / nitrogen / silicon flame retardant solution;

[0064] The solvent is a mixture of water and N,N-dimethylformamide, and the volume proportion of N,N-dimethylformamide in the mixture is 58%; in the phosphorus / nitrogen / silicon flame retardant solution, the content of diethylenetriamine penta (methylene phosphonic acid) is 90 g / L, the content of tris (2,3-epoxypropyl) isocyanurate is 50 g / L, and the content of (3-glycidyl propoxy) trimethoxy silane is 30 g / L;

[0065] (2) adding dicyandiamide to the phosphorus / nitrogen / silicon flame retardant solution obtained in step (1), and then adding ammonia water to adjust the pH to 7 to obtain a flame retardant finishing solution with a dicyandiamide content of 40 g / L;

[0066] (3) immersing the cotton fabric in a flame retardant finishing liquid, performing a double immersion and double rolling treatment, controlling the rolling rate to be 100%, and then performing a baking treatment to obtain a durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant;

[0067] The specific baking process is as follows: pre-baking temperature is 78°C, time is 2.85min; baking temperature is 170°C, time is 2.5min.

[0068] The resulting durable flame retardant and smoke-suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardants has a limiting oxygen index of 32.1%, a damage length of 8 cm, and a total smoke release of 0.07 m 2 After 50 washes, the damaged length was 13.2 cm.

[0069] Example 4

[0070] The preparation method of durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant, the specific steps are as follows:

[0071] (1) dissolving diethylenetriaminepenta(methylenephosphonic acid) and tri(2,3-epoxypropyl)isocyanurate in a solvent to obtain a mixed solution, then adding (3-glycidylpropoxy)trimethoxysilane to the mixed solution at a rate of 1 mL / min, and reacting at a temperature of 75°C for 2 h to obtain a phosphorus / nitrogen / silicon flame retardant solution;

[0072] The solvent is a mixture of water and N,N-dimethylformamide, and the volume proportion of N,N-dimethylformamide in the mixture is 60%; in the phosphorus / nitrogen / silicon flame retardant solution, the content of diethylenetriamine penta (methylene phosphonic acid) is 100 g / L, the content of tris (2,3-epoxypropyl) isocyanurate is 60 g / L, and the content of (3-glycidyl propoxy) trimethoxy silane is 40 g / L;

[0073] (2) adding dicyandiamide to the phosphorus / nitrogen / silicon flame retardant solution obtained in step (1), and then adding ammonia water to adjust the pH to 8 to obtain a flame retardant finishing liquid with a dicyandiamide content of 50 g / L;

[0074] (3) immersing the cotton fabric in a flame retardant finishing liquid, performing a double immersion and double rolling treatment, controlling the rolling ratio to be 110%, and then performing a baking treatment to obtain a durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant;

[0075] The specific baking process is as follows: pre-baking temperature is 75°C, time is 3 minutes; baking temperature is 175°C, time is 2 minutes.

[0076] The final durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardant has a limiting oxygen index of 32.5%, a damage length of 7.8 cm, and a total smoke release of 0.06 m 2 After 50 washes, the damaged length was 13 cm.

Claims

1. A method for preparing a durable flame retardant and smoke-suppressing cotton fabric based on phosphorus / nitrogen / silicon flame retardants, characterized in that The steps include: (1) dissolving diethylenetriamine penta (methylene phosphonic acid) and tri (2,3-epoxypropyl) isocyanurate in a solvent to obtain a mixed solution, and then adding (3-glycidyl propoxy) trimethoxy silane dropwise to the mixed solution at a rate of 0.5-1 mL / min to react to obtain a phosphorus / nitrogen / silicon flame retardant solution; (2) adding dicyandiamide to the phosphorus / nitrogen / silicon flame retardant solution obtained in step (1), and then adding ammonia water to adjust the pH to 6-8 to obtain a flame retardant finishing solution; (3) The cotton fabric is immersed in a flame retardant finishing liquid and subjected to a rolling and baking process to obtain a durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants.

2. The method for preparing a durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants according to claim 1, characterized in that: In step (1), the solvent is a mixture of water and N,N-dimethylformamide, and the volume proportion of N,N-dimethylformamide in the mixture is 50-60%.

3. The method for preparing a durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants according to claim 1, characterized in that: In the phosphorus / nitrogen / silicon flame retardant solution of step (1), the content of diethylenetriaminepenta(methylenephosphonic acid) is 75-100 g / L, the content of tri(2,3-epoxypropyl)isocyanurate is 40-60 g / L, and the content of (3-glycidylpropoxy)trimethoxysilane is 20-40 g / L.

4. The method for preparing a durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants according to claim 1, characterized in that: In step (1), the reaction temperature is 75-85° C., and the reaction time after the (3-glycidylpropoxy)trimethoxysilane solution is added dropwise is 2-3 h.

5. The method for preparing a durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants according to claim 1, characterized in that: The content of dicyandiamide in the flame retardant finishing liquid of step (2) is 30-50 g / L.

6. The method for preparing a durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants according to claim 1, characterized in that: The rolling and baking process in step (3) is as follows: a double-immersion and double-rolling method is adopted, with a rolling rate of 90-110%; a pre-baking temperature of 75-85°C for 2-3 minutes; and a baking temperature of 165-175°C for 2-3 minutes.

7. The method for preparing a durable flame retardant and smoke suppressant cotton fabric based on phosphorus / nitrogen / silicon flame retardants according to claim 1, characterized in that: The limiting oxygen index of the durable flame retardant and smoke suppression cotton fabric based on phosphorus / nitrogen / silicon flame retardants is not less than 31.0%, the damaged length is not higher than 8.7cm, and the total smoke release is not higher than 0.10m 2 After 50 washes, the damaged length is still no more than 14.0cm.

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