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

Abstract

The invention belongs to the technical field of fabric flame-retardant modification, and discloses a preparation method of a durable flame-retardant brocade / cotton blended fabric, which comprises the following steps: dissolving an amino-modified cyclotriphosphazene flame retardant and tetrakis hydroxymethyl phosphonium sulfate in an organic solvent to obtain a flame-retardant solution, immersing the brocade / cotton blended fabric in the flame-retardant solution for immersion treatment, and drying to obtain the durable flame-retardant brocade / cotton blended fabric. The durable flame-retardant brocade / cotton blended fabric is prepared. The flame-retardant performance of the brocade / cotton blended fabric is improved through the phosphorus / nitrogen synergistic flame-retardant effect, the flame-retardant effect is better, flame retardant molecules of the prepared durable flame-retardant brocade / cotton blended fabric are difficult to diffuse to the outside of fibers even in the washing process, and therefore the durable flame-retardant function is provided.

Description

Technical Field

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

[0002] Nylon / cotton blended fabrics have shown wide application value in many fields due to their excellent performance characteristics. This fabric not only has excellent hand feel, high strength, and light specific gravity, but also has high wear resistance, mildew resistance, and moth resistance. Therefore, it is very popular in industry, civil, national defense, sports and outdoor equipment, fashion clothing, home textile products, and even industrial uses. However, for nylon / cotton blended fabrics, there is a special "bracket effect" that shows extremely high flammability. Therefore, it is of great research value to flame retard nylon / cotton blended fabrics to improve their safety.

[0003] For example, reference 1 (Flame-retardant coating finishing of nylon / cotton blended fabrics [J]. Printing and Dyeing, 2022, 48(3):12-15.) uses water-based polyurethane and phosphate flame retardant FR-8526 to apply flame retardant coating to nylon / cotton blended fabrics. However, although this method improves the flame retardancy of the fabric to a certain extent, it has a significant impact on the physical properties of the fabric, especially its air permeability.

[0004] Hexachlorocyclotrimer phosphazene (HCCP), as a cyclic compound with alternating phosphorus and nitrogen, has attracted much attention due to its synergistic effect of phosphorus and nitrogen in flame retardancy. However, HCCP is highly active and exhibits certain instability in practical applications, which greatly limits its direct use in flame retardant treatment of textile materials. Therefore, in order to give full play to 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] For example, Reference 2 (Study on the flame retardancy of hexa(4-aminophenoxy)cyclotriphosphazene for wool fabrics [J]. Printing and Dyeing Auxiliary Agents, 2016(12):49-53.) used hexa(4-aminophenoxy)cyclotriphosphazene, a derivative of hexachlorocyclotriphosphazene, for flame retardant finishing of wool fabrics by dip-pad-drying method. Since wool fiber has a high amino content, hexa(4-aminophenoxy)cyclotriphosphazene and wool can be bonded through ionic bonds. However, the amino content on nylon / cotton blended fabrics is low, making it difficult to adsorb a sufficient amount of flame retardant on nylon / cotton blended fabrics and provide durable flame retardant properties.

[0006] In order to improve the durable flame retardant properties of nylon / cotton blended fabrics, patent CN118547504A discloses a durable flame retardant nylon / cotton blended fabric and an in-situ deposition cross-linking preparation method, which uses a Schiff base between tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensation product and terephthalaldehyde to form an insoluble precipitate inside the fiber, thereby providing durable flame retardant properties. However, the phosphorus content in the entire flame retardant system is low, so the flame retardant effect is poor, the amount of flame retardant used is high, and the physical properties of the fabric (such as feel) are seriously affected.

[0007] Therefore, it is of great significance to study a method for preparing a durable flame retardant nylon / cotton blended fabric 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 method for preparing a durable flame-retardant nylon / cotton blended fabric.

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

[0010] A method for preparing a durable flame-retardant nylon / cotton blended fabric comprises dissolving an amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate in an organic solvent to obtain a flame-retardant liquid, immersing the nylon / cotton blended fabric in the flame-retardant liquid for impregnation treatment, and air-drying or baking at room temperature to obtain the durable flame-retardant nylon / cotton blended fabric;

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

[0012] As the preferred technical solution:

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

[0014] According to the preparation method of a 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 damaged 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 damaged length is not higher than 10.6 cm. After 50 washes, it can still pass the vertical burning test, and the damaged length is not higher than 14.3 cm, which shows that the present invention has good flame retardant properties and water washability.

[0015] 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: dissolving hexachlorocyclotriphosphazene and ethylenediamine in chloroform, using triethylamine as an acid binding agent, reacting at 20-30°C for 4-5h, and then obtaining the amino-modified cyclotriphosphazene flame retardant through reduced pressure distillation and ethanol washing.

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

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

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

[0019] In the preparation method of a durable flame-retardant nylon / cotton blended fabric as described above, the content of amino-modified cyclotriphosphazene flame retardant in the flame retardant liquid is 40-60 g / L, and the content of tetrakis(hydroxymethyl)phosphonium sulfate is 50-70 g / L. The higher the amount of flame retardant used, the more helpful it is to improve the flame retardant properties of the nylon / cotton blended fabric, but too high an amount is wasteful.

[0020] In the method for preparing a durable flame-retardant nylon / cotton blended fabric as described above, the bath ratio of the impregnation is 1:30-40; after the impregnation, the fabric is shaken at 85-95° C. for 60-90 minutes.

[0021] The principle of the present invention is:

[0022] Hexachlorocyclotriphosphazene has high phosphorus and nitrogen contents. However, hexachlorocyclotriphosphazene is highly active and unstable during use, making it difficult to directly apply it to the flame retardant modification of nylon / cotton blended fabrics. The hydroxymethyl group of tetrakishydroxymethylphosphonium sulfate cannot react with the hydroxyl group of cotton fibers, and the amino content of nylon fibers is low, making it difficult to graft onto nylon / cotton blended fabrics.

[0023] The active chlorine of hexachlorocyclotriphosphazene can react with the amino group of ethylenediamine by nucleophilic substitution reaction, thereby obtaining amino-modified cyclotriphosphazene flame retardant. On the one hand, the surface of amino-modified cyclotriphosphazene flame retardant is rich in amino groups, which can react with the hydroxymethyl groups of tetrakis hydroxymethyl phosphonium sulfate to form flame-retardant polymers in situ on nylon / cotton blended fabrics; on the other hand, the excess hydroxymethyl groups of tetrakis hydroxymethyl phosphonium sulfate can react with the amino groups of nylon fibers to graft the flame-retardant polymers on nylon / cotton blended fabrics through covalent bonds. Even if the content of active amino groups on nylon / cotton blended fabrics is low, tetrakis hydroxymethyl phosphonium sulfate has high reaction activity with amino-modified cyclotriphosphazene flame retardant, and it is very easy to form cross-linked network insoluble precipitation inside the fiber, which is difficult to diffuse to the outside of the fiber during washing, thereby providing durable flame retardant function.

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

[0025] Beneficial effects:

[0026] (1) The present invention generates a flame retardant polymer in situ on a nylon / cotton blended fabric by cross-linking the amino groups rich in the surface of an amino-modified cyclotriphosphazene flame retardant with the hydroxymethyl groups of tetrakis(hydroxymethyl)phosphonium sulfate. The excess hydroxymethyl groups of the tetrakis(hydroxymethyl)phosphonium sulfate can also cross-link with the amino groups of nylon fibers, so that the flame retardant polymer is grafted onto the nylon / cotton blended fabric through covalent bonds, thereby improving the flame retardant properties and flame retardant durability of the nylon / cotton blended fabric.

[0027] (2) The tetrakis(hydroxymethyl)phosphonium sulfate of the present invention has high reactivity with the amino-modified cyclotriphosphazene flame retardant and can easily form a cross-linked network insoluble precipitate inside the fiber. Even during the water washing process, it is difficult to diffuse to the outside of the fiber, thereby providing a durable flame retardant function.

[0028] (3) The amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate of the present invention are rich in phosphate groups, and the amino-modified cyclotriphosphazene flame retardant is rich in amino groups. Both improve the flame retardant properties of nylon / cotton blended fabrics through the synergistic flame retardant effect of phosphorus / nitrogen, and have good flame retardant effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The carbon nuclear magnetic resonance spectrum of the amino-modified cyclotriphosphazene flame retardant of the present invention is shown in FIG. DETAILED DESCRIPTION

[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 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.

[0031] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0032] Limiting oxygen index: GB / T 5454-1997 "Oxygen index method for textile combustion performance test" was used to measure the limiting oxygen index 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.

[0033] Damage length: GB / T 5455-2014 “Determination of damage length, smoldering and afterflaming time in vertical direction of combustion performance of textiles” was used to measure the damage length 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.

[0034] Damaged length after 50 washes: The durable flame retardant nylon / cotton blended fabrics prepared in each embodiment and the flame retardant nylon / cotton blended fabrics prepared in the comparative example were washed 50 times with reference to AATCC 61-2013 "Accelerated test for color fastness to washing for household and commercial use", and then the damaged lengths of the durable flame retardant nylon / cotton blended fabrics and the flame retardant nylon / cotton blended fabrics after washing were tested with reference to GB / T 5455-2014 "Determination of damage length in vertical direction of burning performance of textiles - smoldering and afterflaming time" standard.

[0035] Example 1

[0036] A method for preparing a durable flame-retardant nylon / cotton blended fabric, comprising the following steps:

[0037] (1) Preparation of amino-modified cyclotriphosphazene flame retardant;

[0038] Hexachlorocyclotriphosphazene and ethylenediamine are dissolved in chloroform, triethylamine is used as an acid-binding agent, the mixture is reacted at 20°C for 5 hours, and then the amino-modified cyclotriphosphazene flame retardant is prepared by vacuum distillation and ethanol washing; wherein the molar ratio of hexachlorocyclotriphosphazene to ethylenediamine is 1:6, the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:6, and the mass ratio of chloroform to hexachlorocyclotriphosphazene is 30:1; the temperature of the vacuum distillation is 40°C, and the vacuum degree is 2kPa;

[0039] The chemical formula of the prepared amino-modified cyclotriphosphazene flame retardant is Its carbon NMR spectrum is as follows Figure 1 As shown in the figure, it can be seen that the chemical shifts at 42.0ppm and 40.1ppm are caused by the carbon elements connected to the unreacted amino group and the reactive amino group, indicating that the amino-modified cyclotriphosphazene flame retardant is successfully synthesized in this embodiment;

[0040] (2) The amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate prepared in step (1) were dissolved in a mixture of ethanol and distilled water to obtain a flame retardant liquid, and then a nylon / cotton blended fabric (manufacturer: Suzhou Zhaohai Textile Technology Co., Ltd., weight: 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, triethylamine was used as an acid-binding agent, the mixture was reacted at 25°C for 4.7 hours, and then the amino-modified cyclotriphosphazene flame retardant was prepared by vacuum distillation and ethanol washing; wherein 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 the 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) are dissolved in a mixture of ethanol and distilled water to obtain a flame retardant liquid, and then a nylon / cotton blended fabric (manufacturer: Suzhou Zhaohai Textile Technology Co., Ltd., weight: 150 g / m 2 , nylon content is 35wt%), immersed in a flame retardant liquid and shaken at 90°C for 80min, and finally dried at room temperature to obtain a durable flame retardant nylon / cotton blended fabric; wherein ethanol accounts for 17% 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 45g / L, and the content of tetrakishydroxymethylphosphonium sulfate is 55g / L.

[0052] The final durable flame-retardant nylon / cotton blended fabric has a limiting oxygen index of 31.7% and a damaged length of 9.2 cm. After 50 washes, it can still pass the vertical burning test with a damaged length of 13.2 cm.

[0053] Example 3

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

[0055] (1) Preparation of amino-modified cyclotriphosphazene flame retardant;

[0056] Hexachlorocyclotriphosphazene and ethylenediamine were dissolved in chloroform, triethylamine was used as an acid-binding agent, the mixture was reacted at 28°C for 4.4 hours, and then the amino-modified cyclotriphosphazene flame retardant was prepared by vacuum distillation and ethanol washing; wherein 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 the 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) The amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate prepared in step (1) were dissolved in a mixture of ethanol and distilled water to obtain a flame retardant liquid, and then a nylon / cotton blended fabric (manufacturer: Suzhou Zhaohai Textile Technology Co., Ltd., weight: 150 g / m 2 , the nylon content is 40wt%), immersed in a flame retardant liquid and shaken at 95°C for 60 minutes, and finally dried at room temperature to obtain a durable flame retardant nylon / cotton blended fabric; wherein ethanol accounts for 18% 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 50g / L, and the content of tetrakishydroxymethylphosphonium sulfate is 60g / L.

[0059] The final durable flame-retardant nylon / cotton blended fabric has a limiting oxygen index of 32.5% and a damaged length of 8.5 cm. After 50 washes, it can still pass the vertical burning test with a damaged length of 12.4 cm.

[0060] Example 4

[0061] A method for preparing a durable flame-retardant nylon / cotton blended fabric, comprising the following steps:

[0062] (1) Preparation of amino-modified cyclotriphosphazene flame retardant;

[0063] Hexachlorocyclotriphosphazene and ethylenediamine were dissolved in chloroform, triethylamine was used as an acid binding agent, the mixture was reacted at 30°C for 4 hours, and then the amino-modified cyclotriphosphazene flame retardant was prepared by vacuum distillation and ethanol washing; wherein the molar ratio of hexachlorocyclotriphosphazene to ethylenediamine was 1:6.6, the molar ratio of hexachlorocyclotriphosphazene to triethylamine was 1:7, and the mass ratio of chloroform to hexachlorocyclotriphosphazene was 40:1; the temperature of the vacuum distillation was 50°C, and the vacuum degree was 1.5 kPa;

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

[0065] (2) The amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate prepared in step (1) are dissolved in a mixture of ethanol and distilled water to obtain a flame retardant liquid, and then a nylon / cotton blended fabric (manufacturer: Suzhou Zhaohai Textile Technology Co., Ltd., weight: 150 g / m 2 , nylon content is 50wt%), immersed in a flame retardant liquid, shaken at 92°C for 70min, and finally dried at room temperature to obtain a durable flame retardant nylon / cotton blended fabric; wherein ethanol accounts for 20% 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 60g / L, and the content of tetrakishydroxymethylphosphonium sulfate is 70g / L.

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

Claims

1. A method for preparing a durable flame-retardant nylon / cotton blended fabric, characterized in that: The amino-modified cyclotriphosphazene flame retardant and tetrakis(hydroxymethyl)phosphonium sulfate are dissolved in an organic solvent to obtain a flame retardant liquid, and a nylon / cotton blended fabric is immersed in the flame retardant liquid for impregnation treatment to obtain a durable flame retardant nylon / cotton blended fabric; The chemical formula of amino-modified cyclotriphosphazene flame retardant is .

2. The method for preparing a durable flame-retardant nylon / cotton blended fabric according to claim 1, characterized in that: In nylon / cotton blended fabrics, the nylon content is 20~50wt%.

3. The method for preparing a durable flame-retardant nylon / cotton blended fabric according to claim 2, characterized in that: The limiting oxygen index of the durable flame-retardant nylon / cotton blended fabric is not less than 30.5%, the damaged length is not higher than 10.6cm, and it can still pass the vertical burning test after 50 washes, and the damaged length is not higher than 14.3cm.

4. The method for preparing 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 as follows: hexachlorocyclotriphosphazene and ethylenediamine are dissolved in chloroform, triethylamine is used as an acid-binding agent, the mixture is reacted at 20-30°C for 4-5 hours, and then the amino-modified cyclotriphosphazene flame retardant is obtained by vacuum distillation and ethanol washing.

5. The method for preparing 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 method for preparing a durable flame-retardant nylon / cotton blended fabric according to claim 4, characterized in that: The temperature of reduced pressure distillation is 40~50℃, and the vacuum degree is 1.5~2.0kPa.

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

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

9. The method for preparing a durable flame-retardant nylon / cotton blended fabric according to claim 1, characterized in that: The bath ratio for immersion is 1:30~40; after immersion, oscillate at 85~95℃ for 60~90min.

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