Preparation method of durable flame-retardant nylon / cotton blended fabric

Abstract

The present invention belongs to the technical field of fabric flame retardant modification, and discloses a preparation method of a durable flame retardant nylon / cotton blended fabric. The preparation method is as follows: An amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate are dissolved in an organic solvent to obtain a flame retardant solution, and the nylon / cotton blended fabric is immersed in the flame retardant solution for impregnation treatment to obtain the durable flame retardant nylon / cotton blended fabric. The present invention improves the flame retardant performance of the nylon / cotton blended fabric through the phosphorus / nitrogen synergistic flame retardant effect, and has a better flame retardant effect. Moreover, the durable flame retardant nylon / cotton blended fabric prepared has the property that even during the water washing process, the flame retardant molecules are difficult to diffuse to the outside of the fiber, thereby providing a durable flame retardant function.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardant modification of fabrics, and relates to a preparation method of a durable flame retardant nylon / cotton blended fabric. Background Art

[0002] Due to its excellent performance characteristics, nylon / cotton blended fabric has shown extensive application value in multiple fields. This fabric not only has good hand feeling, high strength, and light weight, but also has high abrasion resistance, mildew resistance, and moth resistance. Therefore, it is very popular in industrial, civil, national defense, sports and outdoor equipment, fashion clothing, home textile products, and even industrial applications. However, for nylon / cotton blended fabric, there is a special "scaffold effect", showing extremely high flammability. Therefore, it is of great research value to flame retard the nylon / cotton blended fabric to improve its safety.

[0003] As described in Document 1 (Flame Retardant Coating Finishing of Nylon / Cotton Blended Fabric [J]. Dyeing & Finishing, 2022, 48(3): 12 - 15.), a waterborne polyurethane and a phosphate flame retardant FR - 8526 were used to conduct flame retardant coating on nylon / cotton blended fabric. However, although this method improved the flame retardancy of the fabric to a certain extent, it had a greater impact on the physical properties of the fabric, especially the air permeability.

[0004] Hexachlorocyclotriphosphazene (HCCP), as a cyclic compound with alternating phosphorus and nitrogen, has attracted much attention due to its phosphorus - nitrogen synergistic effect in flame retardancy. However, HCCP has strong activity and shows certain instability in practical applications, which greatly limits its direct use in flame retardant treatment of textile materials. Therefore, in order to fully exert the potential of HCCP in flame retardancy and improve its stability and applicability, the industry still needs to conduct more in - depth research and improvement.

[0005] As described in Document 2 (Study on Flame Retardancy of Wool Fabric with Hexakis(4 - aminophenoxy)cyclotriphosphazene [J]. Textile Auxiliaries, 2016(12): 49 - 53.), a derivative of hexachlorocyclotriphosphazene, hexakis(4 - aminophenoxy)cyclotriphosphazene, was used for flame retardant finishing of wool fabric by the pad - dry - cure method. Since the amino content on wool fibers is relatively high, hexakis(4 - aminophenoxy)cyclotriphosphazene and wool can be combined through ionic bonds. However, the amino content on nylon / cotton blended fabric is less, making it difficult to adsorb a sufficient amount of flame retardant on the nylon / cotton blended fabric and difficult to provide durable flame retardant performance.

[0006] In order to improve the durable flame retardant performance of nylon / cotton blended fabrics, Patent CN118547504A discloses a durable flame retardant nylon / cotton blended fabric and an in-situ deposition crosslinking preparation method. By using the Schiff base combination between tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate and terephthalaldehyde, insoluble precipitates are generated inside the fibers, thereby providing durable flame retardant performance. However, the phosphorus content in the entire flame retardant system is relatively low, so the flame retardant effect is poor, the dosage of the flame retardant is high, and the physical properties of the fabric (such as hand feeling) are affected more seriously.

[0007] Therefore, it is of great significance to study a preparation method of durable flame retardant nylon / cotton blended fabrics to solve the above problems. Summary of the Invention

[0008] The purpose of the present invention is to solve the problems existing in the prior art and provide a preparation method of durable flame retardant nylon / cotton blended fabrics.

[0009] To achieve the above purpose, the technical scheme adopted by the present invention is as follows:

[0010] A preparation method of durable flame retardant nylon / cotton blended fabrics. Dissolve the amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate in an organic solvent to obtain a flame retardant solution. Immerse the nylon / cotton blended fabric in the flame retardant solution for impregnation treatment, and dry or bake it at room temperature to obtain the durable flame retardant nylon / cotton blended fabric;

[0011] The chemical formula of the amino-modified cyclotriphosphazene flame retardant is .

[0012] As a preferred technical scheme:

[0013] In the preparation method of the durable flame retardant nylon / cotton blended fabric as described above, in the nylon / cotton blended fabric, the content of nylon is 20-50wt%.

[0014] In the preparation method of the durable flame retardant nylon / cotton blended fabric as described above, the limiting oxygen index of the unmodified nylon / cotton blended fabric is 20.3%, and the damage length is 30 cm; the limiting oxygen index of the durable flame retardant nylon / cotton blended fabric is not less than 30.5%, and the damage length is not higher than 10.6 cm. After 50 washes, it can still pass the vertical burning test, and the damage length is not higher than 14.3 cm. This shows that the present invention has good flame retardant performance and washing resistance.

[0015] In the preparation method of the durable flame retardant nylon / cotton blended fabric as described above, the preparation method of the amino-modified cyclotriphosphazene flame retardant is: dissolve hexachlorocyclotriphosphazene and ethylenediamine in chloroform, use triethylamine as an acid-binding agent, react at 20-30 °C for 4-5 h, and then obtain the amino-modified cyclotriphosphazene flame retardant through reduced pressure distillation and ethanol washing.

[0016] A preparation method of a durable flame-retardant nylon / cotton blended fabric as described above, the molar ratio of hexachlorocyclotriphosphazene to ethylenediamine is 1:6 to 6.6. Theoretically, every mole of hexachlorocyclotriphosphazene undergoes a nucleophilic substitution reaction with six moles of ethylenediamine, and the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:6 to 7.

[0017] A preparation method of a durable flame-retardant nylon / cotton blended fabric as described above, the temperature of vacuum distillation is 40 to 50 °C, and the vacuum degree is 1.5 to 2.0 kPa.

[0018] A preparation method of a durable flame-retardant nylon / cotton blended fabric as described above, the organic solvent is a mixed solution of ethanol and distilled water, and ethanol accounts for 15 to 20% of the total volume of the organic solvent.

[0019] A preparation method of a durable flame-retardant nylon / cotton blended fabric as described above, the content of the amino-modified cyclotriphosphazene flame retardant in the flame-retardant liquid is 40 to 60 g / L, and the content of tetrakis(hydroxymethyl)phosphonium sulfate is 50 to 70 g / L. The higher the dosage of the flame retardant, the more conducive it is to improving the flame-retardant performance of the nylon / cotton blended fabric, but too high dosage will cause waste.

[0020] A preparation method of a durable flame-retardant nylon / cotton blended fabric as described above, the bath ratio of impregnation is 1:30 to 40; after impregnation, it is oscillated at 85 to 95 °C for 60 to 90 min.

[0021] The principle of the present invention is:

[0022] Hexachlorocyclotriphosphazene has a relatively high phosphorus content and nitrogen content. However, hexachlorocyclotriphosphazene has high activity and is unstable during application, making it difficult to be directly applied to the flame-retardant modification of nylon / cotton blended fabrics; the hydroxymethyl group of tetrakis(hydroxymethyl)phosphonium sulfate cannot react with the hydroxyl group of cotton fibers, and the amino group content of nylon fibers is relatively small, making it difficult to graft onto nylon / cotton blended fabrics.

[0023] The active chlorine of hexachlorocyclotriphosphazene can undergo a nucleophilic substitution reaction with the amino group of ethylenediamine to obtain an amino-modified cyclotriphosphazene flame retardant. On the one hand, the surface of the amino-modified cyclotriphosphazene flame retardant is rich in amino groups, which can undergo a cross-linking reaction with the hydroxymethyl group of tetrakis(hydroxymethyl)phosphonium sulfate, thereby in-situ generating a flame-retardant polymer on the nylon / cotton blended fabric; on the other hand, the excess hydroxymethyl group of tetrakis(hydroxymethyl)phosphonium sulfate can undergo a cross-linking reaction with the amino group of nylon fibers, thereby grafting the flame-retardant polymer onto the nylon / cotton blended fabric through covalent bonds. Even though the content of active amino groups on the nylon / cotton blended fabric is relatively small, tetrakis(hydroxymethyl)phosphonium sulfate has a high reaction activity with the amino-modified cyclotriphosphazene flame retardant, and it is very easy to generate a cross-linked network of insoluble precipitates inside the fibers, which is difficult to diffuse to the outside of the fibers during the washing process, thereby providing a durable flame-retardant function.

[0024] In addition, the amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate are rich in phosphate groups, and the amino-modified cyclotriphosphazene flame retardant is also rich in amino groups. The flame retardant performance of the nylon / cotton blended fabric is improved through the phosphorus / nitrogen synergistic flame retardant effect, and the flame retardant effect is good.

[0025] Beneficial effects:

[0026] (1) In the present invention, the amino groups rich on the surface of the amino-modified cyclotriphosphazene flame retardant react with the hydroxymethyl groups of tetrakis(hydroxymethyl)phosphonium sulfate, thereby in-situ generating a flame retardant polymer on the nylon / cotton blended fabric. Moreover, the excess hydroxymethyl groups of tetrakis(hydroxymethyl)phosphonium sulfate can also react with the amino groups of nylon fibers, enabling the flame retardant polymer to be grafted onto the nylon / cotton blended fabric through covalent bonds, so as to improve the flame retardant performance and flame retardant durability of the nylon / cotton blended fabric.

[0027] (2) The reaction activity of tetrakis(hydroxymethyl)phosphonium sulfate and the amino-modified cyclotriphosphazene flame retardant in the present invention is high, and it is extremely easy to generate a cross-linked network of insoluble precipitates inside the fibers, which is difficult to diffuse to the outside of the fibers even during the washing process, thereby providing a durable flame retardant function.

[0028] (3) The amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate in the present invention are rich in phosphate groups, and the amino-modified cyclotriphosphazene flame retardant is rich in amino groups. The flame retardant performance of the nylon / cotton blended fabric is improved through the phosphorus / nitrogen synergistic flame retardant effect, and the flame retardant effect is good. Description of the drawings

[0029] Figure 1 It is the nuclear magnetic resonance carbon spectrum of the amino-modified cyclotriphosphazene flame retardant of the present invention. Specific embodiments

[0030] 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 not 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 also fall within the scope defined by the appended claims of this application.

[0031] The test methods for relevant performance indicators in the following examples and comparative examples are as follows:

[0032] Limiting oxygen index: The limiting oxygen index of the durable flame retardant nylon / cotton blended fabric prepared in the following examples and the flame retardant nylon / cotton blended fabric prepared in the comparative examples was measured using GB / T 5454-1997 "Textiles - Burning performance - Oxygen index method".

[0033] Damaged length: The damaged lengths of the durable flame-retardant nylon / cotton blended fabrics prepared in the following examples and the flame-retardant nylon / cotton blended fabrics prepared in the comparative examples were determined using GB / T 5455-2014 Textiles - Burning behaviour - Determination of the length of charred areas, afterflame and afterglow times in the vertical direction.

[0034] Damaged length after 50 washes: First, the durable flame-retardant nylon / cotton blended fabrics prepared in the examples and the flame-retardant nylon / cotton blended fabrics prepared in the comparative examples were washed 50 times with reference to the standard of AATCC 61-2013 Accelerated Test for Colorfastness to Home and Commercial Laundering. Then, the damaged lengths of the washed durable flame-retardant nylon / cotton blended fabrics and flame-retardant nylon / cotton blended fabrics were tested with reference to the standard of GB / T 5455-2014 Textiles - Burning behaviour - Determination of the length of charred areas, afterflame and afterglow times in the vertical direction.

[0035] Example 1

[0036] A preparation method of a durable flame-retardant nylon / cotton blended fabric comprises the following steps:

[0037] (1) Prepare an amino-modified cyclotriphosphazene flame retardant;

[0038] Hexachlorocyclotriphosphazene and ethylenediamine were dissolved in chloroform, and triethylamine was used as an acid-binding agent. The reaction was carried out at 20 °C for 5 h, and then the amino-modified cyclotriphosphazene flame retardant was obtained through reduced-pressure distillation and ethanol washing. Among them, the molar ratio of hexachlorocyclotriphosphazene to ethylenediamine was 1:6, the molar ratio of hexachlorocyclotriphosphazene to triethylamine was 1:6, and the mass ratio of chloroform to hexachlorocyclotriphosphazene was 30:1. The temperature of the reduced-pressure distillation was 40 °C, and the vacuum degree was 2 kPa;

[0039] The chemical formula of the prepared amino-modified cyclotriphosphazene flame retardant is , and its nuclear magnetic resonance carbon spectrum is as shown in Figure 1 . It can be seen from the figure that the chemical shifts at 42.0 ppm and 40.1 ppm are caused by the carbon elements connected to the unreacted amino group and the reacted amino group, indicating that the amino-modified cyclotriphosphazene flame retardant was successfully synthesized in this example;

[0040] (2) The amino-modified cyclotriphosphazene flame retardant prepared in step (1) and tetrakis(hydroxymethyl)phosphonium sulfate were dissolved in a mixed solution of ethanol and distilled water to obtain a flame-retardant solution. Then, according to a bath ratio of 1:30, the nylon / cotton blended fabric (manufactured by Suzhou Zhaohai Textile Technology Co., Ltd., with a gram weight of 150 g / m 2, the nylon content is 20wt%), immersed in a flame retardant liquid, shaken at 85°C for 90 minutes, and finally dried at room temperature to obtain a durable flame retardant nylon / cotton blended fabric; wherein ethanol accounts for 15% of the total volume of the mixed liquid of ethanol and distilled water, the content of amino-modified cyclotriphosphazene flame retardant in the flame retardant liquid is 40g / L, and the content of tetrakishydroxymethylphosphonium sulfate is 50g / L.

[0041] The final durable flame-retardant nylon / cotton blended fabric has a limiting oxygen index of 30.5% and a damaged length of 10.6 cm. After 50 washes, it can still pass the vertical burning test with a damaged length of 14.3 cm.

[0042] Comparative Example 1

[0043] A method for preparing a flame-retardant nylon / cotton blended fabric is basically the same as that in Example 1, except that: step (1) is not performed, and the amino-modified cyclotriphosphazene flame retardant in step (2) is replaced by an equal amount of the novel polyphosphazene flame retardant prepared in document 4 (Preparation and flame retardant properties of modified hexachlorocyclotriphosphazene [J]. Shandong Chemical Industry, 2021, 50(1): 17-19). The preparation process of the novel polyphosphazene flame retardant is as follows: 1 g of hexachlorocyclotriphosphazene and 20 mL of toluene are added to a 250 mL three-necked flask and fully dissolved, then 3.4 g of rhodamine B-amide prepared in document 4 is added thereto and stirred evenly, then N2 is introduced for protection and the temperature is raised to 70°C, and then 20 mL of triethylamine is added. After reacting for 6 hours, water is poured into the mixture to precipitate a large amount of solid, and the novel polyphosphazene flame retardant is obtained after filtration.

[0044] The final flame-retardant nylon / cotton blended fabric had a limiting oxygen index of 29.1% and a damaged length of 12.2 cm. It could not pass the vertical burning test after 50 washes and could only withstand 10 washes to pass the vertical burning test.

[0045] By comparing Comparative Example 1 with Example 1, it can be seen that the flame retardant properties of the flame retardant nylon / cotton blended fabric prepared in Comparative Example 1 are reduced, and the water washing resistance is reduced. This is because the new polyphosphazene flame retardant is not reactive and cannot react with tetrakis(hydroxymethyl)phosphonium sulfate, and can only be deposited on the surface of the nylon / cotton blended fabric through physical action, resulting in the flame retardant properties and flame retardant durability of the flame retardant nylon / cotton blended fabric prepared in Comparative Example 1 being poor.

[0046] Example 2

[0047] A method for preparing a durable flame-retardant nylon / cotton blended fabric, comprising the following steps:

[0048] (1) Preparation of amino-modified cyclotriphosphazene flame retardant;

[0049] Hexachlorocyclotriphosphazene and ethylenediamine were dissolved in chloroform, and triethylamine was used as an acid-binding agent. The reaction was carried out at 25 °C for 4.7 h, and then the amino-modified cyclotriphosphazene flame retardant was obtained by vacuum distillation and ethanol washing. Among them, the molar ratio of hexachlorocyclotriphosphazene to ethylenediamine was 1:6.2, the molar ratio of hexachlorocyclotriphosphazene to triethylamine was 1:6.3, and the mass ratio of chloroform to hexachlorocyclotriphosphazene was 33:1. The temperature of vacuum distillation was 43 °C, and the vacuum degree was 1.8 kPa.

[0050] The chemical formula of the prepared amino-modified cyclotriphosphazene flame retardant is ;

[0051] (2) The amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate prepared in step (1) were dissolved in a mixed solution of ethanol and distilled water to obtain a flame retardant solution. Then, the polyamide / cotton blended fabric (manufactured by Suzhou Zhaohai Textile Technology Co., Ltd., with a gram weight of 150 g / m 2 , and the content of polyamide was 35 wt%) was immersed in the flame retardant solution and oscillated at 90 °C for 80 min. Finally, it was air-dried at room temperature to obtain a durable flame-retardant polyamide / cotton blended fabric. Among them, ethanol accounted for 17% of the total volume of the mixed solution of ethanol and distilled water, the content of the amino-modified cyclotriphosphazene flame retardant in the flame retardant solution was 45 g / L, and the content of tetrakis(hydroxymethyl)phosphonium sulfate was 55 g / L.

[0052] The limiting oxygen index of the finally prepared durable flame-retardant polyamide / cotton blended fabric was 31.7%, the damage length was 9.2 cm, and it could still pass the vertical burning test after 50 washes, and the damage length was 13.2 cm.

[0053] Example 3

[0054] A method for preparing a durable flame-retardant polyamide / cotton blended fabric comprises the following steps:

[0055] (1) Prepare an amino-modified cyclotriphosphazene flame retardant;

[0056] Hexachlorocyclotriphosphazene and ethylenediamine were dissolved in chloroform, and triethylamine was used as an acid-binding agent. The reaction was carried out at 28 °C for 4.4 h, and then the amino-modified cyclotriphosphazene flame retardant was obtained by vacuum distillation and ethanol washing. Among them, the molar ratio of hexachlorocyclotriphosphazene to ethylenediamine was 1:6.4, the molar ratio of hexachlorocyclotriphosphazene to triethylamine was 1:6.6, and the mass ratio of chloroform to hexachlorocyclotriphosphazene was 35:1. The temperature of vacuum distillation was 48 °C, and the vacuum degree was 1.6 kPa.

[0057] The chemical formula of the prepared amino-modified cyclotriphosphazene flame retardant is ;

[0058] (2) Dissolve the amino-modified cyclotriphosphazene flame retardant prepared in step (1) and tetrakis(hydroxymethyl)phosphonium sulfate in a mixed solution of ethanol and distilled water to obtain a flame retardant solution. Then, immerse the polyamide / cotton blended fabric (manufactured by Suzhou Zhaohai Textile Technology Co., Ltd., with a gram weight of 150 g / m 2 , and the polyamide content is 40 wt%) in the flame retardant solution, oscillate at 95 °C for 60 min, and finally dry it at room temperature to obtain a durable flame retardant polyamide / cotton blended fabric; among them, ethanol accounts for 18% of the total volume of the mixed solution of ethanol and distilled water, the content of the amino-modified cyclotriphosphazene flame retardant in the flame retardant solution is 50 g / L, and the content of tetrakis(hydroxymethyl)phosphonium sulfate is 60 g / L.

[0059] The limiting oxygen index of the finally obtained durable flame retardant polyamide / cotton blended fabric is 32.5%, the damage length is 8.5 cm, it can still pass the vertical burning test after 50 washes, and the damage length is 12.4 cm.

[0060] Example 4

[0061] A method for preparing a durable flame retardant polyamide / cotton blended fabric, the steps are as follows:

[0062] (1) Prepare an amino-modified cyclotriphosphazene flame retardant;

[0063] Dissolve hexachlorocyclotriphosphazene and ethylenediamine in chloroform, use triethylamine as an acid-binding agent, react at 30 °C for 4 h, and then obtain the amino-modified cyclotriphosphazene flame retardant through vacuum distillation and ethanol washing; among them, the molar ratio of hexachlorocyclotriphosphazene to ethylenediamine is 1:6.6, the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:7, and the mass ratio of chloroform to hexachlorocyclotriphosphazene is 40:1; the temperature of vacuum distillation is 50 °C, and the vacuum degree is 1.5 kPa;

[0064] The chemical formula of the prepared amino-modified cyclotriphosphazene flame retardant is ;

[0065] (2) Dissolve the amino-modified cyclotriphosphazene flame retardant prepared in step (1) and tetrakis(hydroxymethyl)phosphonium sulfate in a mixed solution of ethanol and distilled water to obtain a flame retardant solution. Then, immerse the polyamide / cotton blended fabric (manufactured by Suzhou Zhaohai Textile Technology Co., Ltd., with a gram weight of 150 g / m 2 , and the polyamide content is 50 wt%) in the flame retardant solution, oscillate at 92 °C for 70 min, and finally dry it at room temperature to obtain a durable flame retardant polyamide / cotton blended fabric; among them, ethanol accounts for 20% of the total volume of the mixed solution of ethanol and distilled water, the content of the amino-modified cyclotriphosphazene flame retardant in the flame retardant solution is 60 g / L, and the content of tetrakis(hydroxymethyl)phosphonium sulfate is 70 g / L.

[0066] The limiting oxygen index of the finally obtained durable flame-retardant nylon / cotton blended fabric is 33.1%, the damaged length is 8.1 cm, and it can still pass the vertical burning test after 50 washes, and the damaged length is 12.1 cm.

Claims

1. A method for preparing a durable flame-retardant nylon / cotton blended fabric, characterized in that: Dissolve the amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate in an organic solvent to obtain a flame retardant solution. Immerse the nylon / cotton blended fabric in the flame retardant solution for impregnation treatment to obtain a durable flame retardant nylon / cotton blended fabric; The impregnation treatment means oscillating at 85 - 95 °C for 60 - 90 min after impregnation; The chemical formula of the amino-modified cyclotriphosphazene flame retardant is 2. The preparation method of a durable flame-retardant nylon / cotton blended fabric according to claim 1, characterized in that, In the nylon / cotton blended fabric, the content of nylon is 20 - 50 wt%.

3. The preparation method of a durable flame-retardant nylon / cotton blended fabric according to claim 2, wherein, The limiting oxygen index of the durable flame retardant nylon / cotton blended fabric is not less than 30.5%, the char length is not more than 10.6 cm, and it can still pass the vertical burning test after 50 washes, and the char length is not more than 14.3 cm.

4. The preparation method of a durable flame-retardant nylon / cotton blended fabric according to claim 1, characterized in that, The preparation method of the amino-modified cyclotriphosphazene flame retardant is: dissolve hexachlorocyclotriphosphazene and ethylenediamine in chloroform, use triethylamine as an acid-binding agent, react at 20 - 30 °C for 4 - 5 h, and then obtain the amino-modified cyclotriphosphazene flame retardant by vacuum distillation and ethanol washing.

5. The preparation method of a durable flame-retardant nylon / cotton blended fabric according to claim 4, characterized in that, The molar ratio of hexachlorocyclotriphosphazene to ethylenediamine is 1:6 - 6.6, and the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:6 - 7.

6. The preparation method of a durable flame-retardant nylon / cotton blended fabric according to claim 4, wherein, The temperature of vacuum distillation is 40 - 50 °C, and the vacuum degree is 1.5 - 2.0 kPa.

7. The preparation method of a durable flame-retardant nylon / cotton blended fabric according to claim 1, characterized in that, The organic solvent is a mixed solution of ethanol and distilled water, and ethanol accounts for 15 - 20% of the total volume of the organic solvent.

8. The preparation method of a durable flame-retardant nylon / cotton blended fabric according to claim 1, characterized in that, The content of the amino-modified cyclotriphosphazene flame retardant in the flame retardant solution is 40 - 60 g / L, and the content of tetrakis(hydroxymethyl)phosphonium sulfate is 50 - 70 g / L.

9. The preparation method of a durable flame-retardant nylon / cotton blended fabric according to claim 1, characterized in that, The bath ratio of impregnation is 1:30 - 40.

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