Preparation method of durable flame-retardant cotton fabric based on reactive cyclotriphosphine flame retardant

Abstract

The invention belongs to the technical field of flame retardant modification of fabrics, and discloses a method for preparing a durable flame retardant cotton fabric based on a reactive cyclotriphosphazene flame retardant, wherein the method comprises: dissolving a reactive cyclotriphosphazene flame retardant, ammonium polyphosphate and dicyandiamide in an organic solvent to obtain a flame retardant liquid, immersing the cotton fabric in the flame retardant liquid for padding treatment, and then sequentially pre-baking and baking to obtain a durable flame retardant cotton fabric; the method for preparing the reactive cyclotriphosphazene flame retardant comprises: dissolving hexachlorocyclotriphosphazene and triethanolamine in chloroform, using triethylamine as an acid binding agent, first reacting for a certain time, and then adding methanol to continue reacting for a certain time to obtain a reactive cyclotriphosphazene flame retardant. The present invention can graft ammonium phosphate and a reactive cyclotriphosphazene flame retardant onto cotton fabrics, thereby providing an efficient and durable flame retardant function, and having a good flame retardant effect.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant modification of fabrics and relates to a method for preparing durable flame retardant cotton fabric based on a reactive cyclotriphosphine flame retardant. Background Art

[0002] Proban is a commercialized durable flame retardant technology for cotton fabrics. Its process first uses tetrakis(hydroxymethyl)phosphonium chloride to react with urea to form a condensation reaction, and uses the condensation product as a flame retardant for cotton fabrics. Then, ammonia fumigation is used to deposit the flame retardant inside the fiber, thereby achieving a durable flame retardant effect on cotton fabrics. However, this technology has two significant drawbacks: first, the ammonia fumigation equipment is expensive, and second, the ammonia fumigation treatment will cause great pollution to the environment. In addition, cotton fabrics treated with Proban flame retardant have serious formaldehyde release during use, which further limits its scope of application.

[0003] Hexachlorocyclotriphosphazene (HCCP) as a flame retardant material has shown unique advantages. Its structure contains rich nitrogen and phosphorus heterogeneous elements, and it has high reactivity, high flame retardancy and excellent thermal stability. In addition, HCCP has a wide variety of derivatives, which have many outstanding properties of both organic and inorganic substances. Therefore, it has received widespread attention in the field of flame retardancy and has achieved many research results. However, although HCCP has excellent flame retardant properties, its high activity and instability during the application process make it difficult to directly use it for flame retardant modification of cotton fabrics.

[0004] Reference 1 (Study on the flame retardant properties of modified hexachlorocyclotrimer phosphazene in polyester [J]. Engineering Plastics Application, 2014(3):94-98.) uses pentaerythritol to modify hexachlorocyclotrimer phosphazene and then use it to improve the flame retardant properties of polyethylene terephthalate (PET). Hexachlorocyclotrimer phosphazene modified with pentaerythritol is rich in hydroxyl groups and has good compatibility with polyester. However, the hydroxyl groups of hexachlorocyclotrimer phosphazene modified with pentaerythritol cannot form covalent bonds with cotton fibers during the reaction, making it difficult to use it for durable flame retardant modification of cotton fabrics through post-finishing technology. It can only be deposited on cotton fabrics, which cannot improve the flame retardant effect of cotton fabrics and has poor flame retardant durability.

[0005] As a phosphorus-based halogen-free flame retardant, ammonium polyphosphate has the advantages of low smoke, low toxicity, low cost, and little environmental harm. It is widely used in flame retardant modification of textiles. However, there are major problems when ammonium polyphosphate is used for durable flame retardant modification of cotton fabrics. For example, Reference 2 (Ammonium polyphosphate / phosphorus-containing polyacrylate adhesive flame retardant finishing of cotton fabrics [J]. Printing and Dyeing, 2022, 48(7): 37-40, 64.) uses phosphorus-containing polyacrylate adhesive to fix ammonium polyphosphate (APP) to cotton fabric to improve the flame retardant properties of cotton fabric. However, there is no covalent bond between ammonium polyphosphate and cotton fabric, resulting in poor water washability and a significant impact on the feel and air permeability of cotton fabric.

[0006] Reference 3 (Industrial Crops & Products 214 (2024) 118454) uses ammonium polyphosphate to covalently graft modify cotton fabrics. The ammonium phosphate group of ammonium polyphosphate can undergo covalent cross-linking reaction with the hydroxyl group of cotton fabric under the catalysis of dicyandiamide. However, its cross-linking degree is limited and the flame retardant durability needs to be further improved. The modified cotton fabric can withstand 20 washes, and a high amount of ammonium polyphosphate acts as a cross-linking agent between cotton fibers, making the movement of cotton fibers difficult, which can easily lead to damage to the strength properties of cotton fabrics.

[0007] Therefore, it is of great significance to study a method for preparing a durable flame-retardant cotton fabric to solve the above problems. Summary of the invention

[0008] The purpose of the invention is to solve the problems existing in the prior art and provide a method for preparing a durable flame-retardant cotton 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 cotton fabric comprises dissolving a reactive cyclotriphosphazene flame retardant, ammonium polyphosphate and dicyandiamide in an organic solvent to obtain a flame-retardant liquid, wherein dicyandiamide is used as a catalyst to promote the covalent bond reaction between the ammonium phosphate group of the ammonium polyphosphate and the hydroxyl group of the cotton fabric and the active hydroxyl group of the reactive cyclotriphosphazene flame retardant, thereby grafting the flame retardant onto the cotton fabric through covalent bonds, immersing the cotton fabric in the flame-retardant liquid for padding treatment, and then pre-baking and baking in sequence to obtain the durable flame-retardant cotton fabric;

[0011] The chemical formula of reactive cyclotriphosphazene flame retardant is .

[0012] As the preferred technical solution:

[0013] The method for preparing a durable flame-retardant cotton fabric as described above, the method for preparing a reactive cyclotriphosphazene flame retardant is as follows: dissolving hexachlorocyclotriphosphazene and triethanolamine in chloroform, using triethylamine as an acid-binding agent, first reacting for a certain time, then adding methanol to continue reacting for a certain time, and finally distilling under reduced pressure and washing with ethanol to obtain the reactive cyclotriphosphazene flame retardant;

[0014] The reaction temperature is 20~30°C, the reaction is carried out for 4~5 hours before adding methanol, and the reaction is continued for 4~5 hours after adding methanol.

[0015] According to the method for preparing a durable flame-retardant cotton fabric, the molar ratio of hexachlorocyclotriphosphazene to triethanolamine is 1:3-3.3. Due to the steric hindrance effect, each mole of hexachlorocyclotriphosphazene reacts with three moles of triethanolamine to undergo a nucleophilic substitution reaction. The molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:6-8, and the molar ratio of hexachlorocyclotriphosphazene to methanol is 1:3-3.3, so that the remaining active chlorine groups can be reacted.

[0016] In the method for preparing a durable flame-retardant cotton fabric as described above, the organic solvent is a mixture of N,N-dimethylformamide and distilled water, and N,N-dimethylformamide accounts for 20-30% of the total volume of the organic solvent.

[0017] According to the method for preparing a durable flame-retardant cotton fabric as described above, the content of the reactive cyclotriphosphazene flame retardant in the flame retardant liquid is 30-50 g / L, and the content of ammonium polyphosphate is 70-100 g / L. The higher the amount of the flame retardant, the more helpful it is to improve the flame retardant properties of the cotton fabric, but too high an amount is wasteful. The content of dicyandiamide is 40-50 g / L.

[0018] According to the method for preparing a durable flame retardant cotton fabric, the cotton fabric is immersed in a flame retardant liquid with a bath ratio of 1:30-40, first oscillated at 50-55° C. for 20-30 minutes, and then subjected to padding treatment.

[0019] In the method for preparing a durable flame-retardant cotton fabric as described above, the padding rate of the padding treatment is 90-100%.

[0020] In the method for preparing a durable flame-retardant cotton fabric as described above, the pre-baking temperature is 80-90°C for 2-3 minutes; the baking temperature is 160-170°C for 4-5 minutes.

[0021] A method for preparing a durable flame-retardant cotton fabric as described in any of the above items, wherein the unmodified cotton fabric has a breaking strength of 520N, a damaged length of 30cm, and a limiting oxygen index of 18.5%; the durable flame-retardant cotton fabric has a breaking strength of not less than 470N, a limiting oxygen index of not less than 29.5%, a damaged length of not more than 9.8cm, and can still pass the vertical burning test after 50 washes, and the damaged length is not more than 14.6cm, which indicates that the durable flame-retardant cotton fabric prepared by the present invention has good flame retardant properties and water washability, and less damage to mechanical properties.

[0022] The principle of the present invention is:

[0023] Hexachlorocyclotriphosphazene has high phosphorus and nitrogen contents. However, hexachlorocyclotriphosphazene is highly active and unstable during use, making it difficult to directly apply to the flame retardant modification of cotton fabrics. The ammonium phosphate group of ammonium polyphosphate can undergo a covalent cross-linking reaction with the hydroxyl group of cotton fabrics under the catalysis of dicyandiamide. However, its degree of cross-linking is limited, and the flame retardant durability needs to be further improved. In addition, a high amount of ammonium polyphosphate acts as a cross-linking agent between cotton fibers, making it difficult for cotton fibers to move, which can easily lead to damage to the strength properties of cotton fabrics.

[0024] The invention utilizes the active chlorine of hexachlorocyclotriphosphazene to react with the hydroxyl groups of triethanolamine and methanol to undergo nucleophilic substitution reaction, thereby preparing a reactive cyclotriphosphazene flame retardant. On one hand, the ammonium phosphate radical of ammonium polyphosphate can react with the hydroxyl groups of cotton fabric under the catalysis of dicyandiamide to produce a covalent bond cross-linking reaction, thereby grafting the ammonium phosphate onto the cotton fabric; on the other hand, the ammonium phosphate radical of ammonium polyphosphate can react with the hydroxyl groups of the reactive cyclotriphosphazene flame retardant to graft the reactive cyclotriphosphazene flame retardant onto the cotton fabric, thereby providing a highly efficient and durable flame retardant function.

[0025] Under the process conditions of the present invention, ammonium polyphosphate not only acts as a flame retardant, but also acts as a cross-linking agent between the reactive cyclotriphosphazene flame retardant and the cotton fabric; in the process of grafting ammonium polyphosphate and the cotton fabric, due to the characteristics of the molecular structure of ammonium polyphosphate, its active ammonium phosphate groups are difficult to fully react with the cotton fabric due to steric hindrance, resulting in a limited degree of grafting, and the excess active ammonium phosphate groups of ammonium polyphosphate can react with the reactive cyclotriphosphazene flame retardant, and the active groups of ammonium polyphosphate can be effectively utilized. Therefore, by introducing the reactive cyclotriphosphazene flame retardant and reacting with ammonium polyphosphate, the amount of ammonium polyphosphate grafted on the cotton fabric can be reduced without affecting the flame retardant properties of the modified cotton fabric, thereby playing a role in protecting the strength of the cotton fabric.

[0026] In addition, the phosphate groups of ammonium polyphosphate and reactive cyclotriphosphazene flame retardant act as acid sources, the nitrogen-containing groups of the two flame retardants act as gas sources, and the hydroxyl group of triethanolamine acts as a carbon source, organically constructing an intumescent flame retardant system with good flame retardant effect, which can effectively improve the flame retardant properties of cotton fabrics.

[0027] Beneficial effects:

[0028] (1) The ammonium phosphate radical of the ammonium polyphosphate in the present invention can produce a covalent cross-linking reaction with the hydroxyl group of the cotton fabric under the catalysis of dicyandiamide, and then the ammonium phosphate radical of the ammonium polyphosphate can produce a covalent bond reaction with the hydroxyl group of the reactive cyclotriphosphazene flame retardant, thereby grafting both the ammonium phosphate and the reactive cyclotriphosphazene flame retardant onto the cotton fabric, providing a highly efficient and durable flame retardant function.

[0029] (2) The present invention utilizes the phosphate groups of ammonium polyphosphate and reactive cyclotriphosphazene flame retardant as acid sources, the nitrogen-containing groups of the two flame retardants as gas sources, and the hydroxyl group of triethanolamine as carbon source to organically construct an intumescent flame retardant system with good flame retardant effect, which can effectively improve the flame retardant properties of cotton fabrics. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The carbon nuclear magnetic resonance spectrum of the reactive cyclotriphosphazene flame retardant of the present invention is shown in FIG. 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 testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0033] Breaking strength: GB / T 3923.1-2013 "Tensile properties of textile fabrics - Part 1: Determination of breaking strength and elongation at break - Strip method" was used to measure the breaking strength of the durable flame retardant cotton fabrics prepared in the following examples and the flame retardant cotton fabrics prepared in the comparative examples.

[0034] 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 cotton fabrics prepared in the following examples and the flame retardant cotton fabrics prepared in the comparative examples.

[0035] Damage length: GB / T 5455-2014 “Determination of damage length in vertical direction, smoldering and afterflaming time of textile combustion performance” was used to measure the damage length of the durable flame retardant cotton fabrics prepared in the following examples and the flame retardant cotton fabrics prepared in the comparative examples.

[0036] Damaged length after 50 washings: The durable flame retardant cotton fabrics prepared in the following examples and the flame retardant cotton fabrics prepared in the comparative examples were first washed 50 times using the AATCC 61-2013 "Accelerated test for color fastness to washing for household and commercial use" standard, and then the GB / T 5455-2014 "Determination of damage length in vertical direction, smoldering and afterflaming time of textile combustion performance" standard was used to test the damaged length of the durable flame retardant cotton fabric and the flame retardant cotton fabric after washing.

[0037] Example 1

[0038] A method for preparing a durable flame-retardant cotton fabric comprises the following steps:

[0039] (1) Preparation of reactive cyclotriphosphazene flame retardant;

[0040] Dissolve hexachlorocyclotriphosphazene and triethanolamine in chloroform, use triethylamine as an acid-binding agent, react at 20°C for 5 hours, then add methanol and continue to react at 20°C for 5 hours, and finally obtain a reactive cyclotriphosphazene flame retardant after vacuum distillation and ethanol washing; wherein the molar ratio of hexachlorocyclotriphosphazene to triethanolamine is 1:3, the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:6, the mass ratio of chloroform to hexachlorocyclotriphosphazene is 30:1, the molar ratio of hexachlorocyclotriphosphazene to methanol is 1:3.3, the temperature of vacuum distillation is 40°C, and the vacuum degree is 2kPa;

[0041] The chemical formula of the prepared reactive 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 59.7ppm, 57.8ppm, 56.8ppm and 52.5ppm are caused by the carbon elements of the triethanolamine structure, and the chemical shift at 39.7ppm is caused by the carbon element of the methyl group in the benzyl alcohol structure. The results show that the reactive cyclotriphosphazene flame retardant is successfully synthesized in this embodiment;

[0042] (2) dissolving the reactive cyclotriphosphazene flame retardant, ammonium polyphosphate (manufacturer: Aike Reagent, product number: 147064) and dicyandiamide prepared in step (1) in a mixture of N,N-dimethylformamide and distilled water to obtain a flame retardant liquid; wherein the N,N-dimethylformamide accounts for 20% of the total volume of the mixture of N,N-dimethylformamide and distilled water; the content of the reactive cyclotriphosphazene flame retardant in the flame retardant liquid is 30 g / L, the content of ammonium polyphosphate is 70 g / L, and the content of dicyandiamide is 40 g / L;

[0043] (3) Cotton fabric (manufacturer: Guangdong Dongguan Weiman Baida Textile Co., Ltd., with a surface density of 100 g / m 2) is immersed in the flame retardant liquid obtained in step (2), and then oscillated at 50°C for 30 minutes and then padded with a padding rate of 90%, followed by pre-baking at 80°C for 3 minutes and finally baking at 160°C for 5 minutes to obtain a durable flame retardant cotton fabric.

[0044] The final durable flame-retardant cotton fabric has a breaking strength of 508N, a limiting oxygen index of 29.5%, a damage length of 9.8cm, and can still pass the vertical burning test after 50 washes with a damage length of 14.6cm.

[0045] Comparative Example 1

[0046] A method for preparing a flame-retardant cotton fabric is basically the same as that in Example 1, except that: step (1) is not performed, and the reactive cyclotriphosphazene flame retardant in step (2) is replaced by an equal mass of a 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, 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, 20 mL of triethylamine is added, and after reacting for 6 hours, water is poured therein to precipitate a large amount of solids, and the novel polyphosphazene flame retardant is obtained after filtration.

[0047] The final flame-retardant cotton fabric has a breaking strength of 450N, a limiting oxygen index of 28.3%, and a damaged length of 10.9cm. It cannot pass the vertical burning test after 50 washes. To pass the vertical burning test, it can only withstand 20 washes.

[0048] By comparing Comparative Example 1 with Example 1, it can be seen that the breaking strength of the flame-retardant cotton fabric prepared in Comparative Example 1 is reduced, and the flame retardant performance and water washing resistance are reduced. This is because the new polyphosphazene flame retardant in Comparative Example 1 cannot react with the ammonium phosphate radical of ammonium polyphosphate, and can only be deposited on the surface of the cotton fabric by physical action, which leads to the reduction of the flame retardant performance of the flame-retardant cotton fabric prepared, especially the flame retardant durability will be greatly reduced; in addition, the ammonium phosphate radical of ammonium polyphosphate will cause the breaking strength of the cotton fabric to decrease after the cross-linking reaction between the ammonium phosphate radical of ammonium polyphosphate and the cotton fiber, while in Example 1, since the reactive cyclotriphosphazene flame retardant reacts with the excess active ammonium phosphate groups of ammonium polyphosphate, part of the ammonium phosphate radical will be consumed, which has the effect of protecting the breaking strength of the cotton fabric.

[0049] Comparative Example 2

[0050] A method for preparing a flame-retardant cotton fabric is basically the same as that of Example 1, except that step (1) is not performed, and in step (2), the reactive cyclotriphosphazene flame retardant is replaced by an equal mass of ammonium polyphosphate (manufacturer: Aike Reagent, item number: 147064).

[0051] The final flame-retardant cotton fabric has a breaking strength of 452N, a limiting oxygen index of 27.9%, a damaged length of 12.0cm, and cannot pass the vertical burning test after 50 washes. To pass the vertical burning test, it can only withstand 20 washes.

[0052] Comparing Comparative Example 2 with Example 1, it can be seen that the breaking strength of the flame-retardant cotton fabric prepared in Comparative Example 2 is reduced, and the flame retardant performance and water wash resistance are reduced. This is because only ammonium polyphosphate is used as a flame retardant in Comparative Example 2. Although it can undergo covalent cross-linking reaction with the hydroxyl group of the cotton fabric under the catalysis of dicyandiamide, its cross-linking degree is limited, which leads to a decrease in flame retardant performance and greatly reduces flame retardant durability; in addition, the ammonium phosphate root of ammonium polyphosphate undergoes a cross-linking reaction with cotton fibers, which will cause the breaking strength of the cotton fabric to decrease. In Example 1, since the reactive cyclotriphosphazene flame retardant reacts with the excess active ammonium phosphate groups of ammonium polyphosphate, part of the ammonium phosphate root will be consumed, which has the effect of protecting the breaking strength of the cotton fabric.

[0053] Example 2

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

[0055] (1) Preparation of reactive cyclotriphosphazene flame retardant;

[0056] Dissolve hexachlorocyclotriphosphazene and triethanolamine in chloroform, use triethylamine as an acid-binding agent, react at 25°C for 4.5 hours, then add methanol and continue to react at 25°C for 4 hours, and finally obtain a reactive cyclotriphosphazene flame retardant after reduced pressure distillation and ethanol washing; wherein the molar ratio of hexachlorocyclotriphosphazene to triethanolamine is 1:3.3, the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:8, the mass ratio of chloroform to hexachlorocyclotriphosphazene is 33:1, the molar ratio of hexachlorocyclotriphosphazene to methanol is 1:3.2, the temperature of reduced pressure distillation is 45°C, and the vacuum degree is 1.8 kPa;

[0057] The chemical formula of the prepared reactive cyclotriphosphazene flame retardant is ;

[0058] (2) dissolving the reactive cyclotriphosphazene flame retardant, ammonium polyphosphate (manufacturer: Aike Reagent, product number: 147064) and dicyandiamide prepared in step (1) in a mixture of N,N-dimethylformamide and distilled water to obtain a flame retardant liquid; wherein the N,N-dimethylformamide accounts for 25% of the total volume of the mixture of N,N-dimethylformamide and distilled water; the content of the reactive cyclotriphosphazene flame retardant in the flame retardant liquid is 35 g / L, the content of ammonium polyphosphate is 80 g / L, and the content of dicyandiamide is 45 g / L;

[0059] (3) Cotton fabric (manufacturer: Guangdong Dongguan Weiman Baida Textile Co., Ltd., with a surface density of 100 g / m 2 ) is immersed in the flame retardant liquid obtained in step (2), and then oscillated at 52°C for 26 minutes and then padded, followed by pre-baking at 85°C for 2.6 minutes, and finally baked at 164°C for 4.8 minutes to obtain a durable flame retardant cotton fabric; wherein the padding rate of the padding treatment is 95%.

[0060] The final durable flame-retardant cotton fabric has a breaking strength of 495N, a limiting oxygen index of 30.9%, a damage length of 9cm, and can still pass the vertical burning test after 50 washes with a damage length of 13.8cm.

[0061] Example 3

[0062] A method for preparing a durable flame-retardant cotton fabric comprises the following steps:

[0063] (1) Preparation of reactive cyclotriphosphazene flame retardant;

[0064] Dissolve hexachlorocyclotriphosphazene and triethanolamine in chloroform, use triethylamine as an acid-binding agent, react at 30°C for 4h, then add methanol and continue to react at 30°C for 4.5h, and finally obtain a reactive cyclotriphosphazene flame retardant after vacuum distillation and ethanol washing; wherein the molar ratio of hexachlorocyclotriphosphazene to triethanolamine is 1:3.2, the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:7, the mass ratio of chloroform to hexachlorocyclotriphosphazene is 35:1, the molar ratio of hexachlorocyclotriphosphazene to methanol is 1:3.1, the temperature of vacuum distillation is 50°C, and the vacuum degree is 1.5kPa;

[0065] The chemical formula of the prepared reactive cyclotriphosphazene flame retardant is ;

[0066] (2) dissolving the reactive cyclotriphosphazene flame retardant, ammonium polyphosphate (manufacturer: Aike Reagent, product number: 147064) and dicyandiamide obtained in step (1) in a mixture of N,N-dimethylformamide and distilled water to obtain a flame retardant liquid; wherein the N,N-dimethylformamide accounts for 30% of the total volume of the mixture of N,N-dimethylformamide and distilled water; the content of the reactive cyclotriphosphazene flame retardant in the flame retardant liquid is 40 g / L, the content of ammonium polyphosphate is 90 g / L, and the content of dicyandiamide is 50 g / L;

[0067] (3) Cotton fabric (manufacturer: Guangdong Dongguan Weiman Baida Textile Co., Ltd., with a surface density of 100 g / m 2 ) is immersed in the flame retardant liquid obtained in step (2), and then oscillated at 54°C for 24 minutes and then padded, followed by pre-baking at 87°C for 2.3 minutes, and finally baked at 167°C for 4.5 minutes to obtain a durable flame retardant cotton fabric; wherein the padding rate of the padding treatment is 100%.

[0068] The final durable flame-retardant cotton fabric has a breaking strength of 486N, a limiting oxygen index of 32.2%, and a damage length of 8.5cm. After 50 washes, it can still pass the vertical burning test with a damage length of 13.1cm.

[0069] Example 4

[0070] A method for preparing a durable flame-retardant cotton fabric comprises the following steps:

[0071] (1) Preparation of reactive cyclotriphosphazene flame retardant;

[0072] Dissolve hexachlorocyclotriphosphazene and triethanolamine in chloroform, use triethylamine as an acid-binding agent, react at 27°C for 4.3 hours, then add methanol and continue to react at 27°C for 4.2 hours, and finally obtain a reactive cyclotriphosphazene flame retardant after vacuum distillation and ethanol washing; wherein the molar ratio of hexachlorocyclotriphosphazene to triethanolamine is 1:3.1, the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:6.5, the mass ratio of chloroform to hexachlorocyclotriphosphazene is 40:1, the molar ratio of hexachlorocyclotriphosphazene to methanol is 1:3, the temperature of vacuum distillation is 45°C, and the vacuum degree is 1.7 kPa;

[0073] The chemical formula of the prepared reactive cyclotriphosphazene flame retardant is ;

[0074] (2) dissolving the reactive cyclotriphosphazene flame retardant, ammonium polyphosphate (manufacturer: Aike Reagent, product number: 147064) and dicyandiamide prepared in step (1) in a mixture of N,N-dimethylformamide and distilled water to obtain a flame retardant liquid; wherein the N,N-dimethylformamide accounts for 26% of the total volume of the mixture of N,N-dimethylformamide and distilled water; the content of the reactive cyclotriphosphazene flame retardant in the flame retardant liquid is 50 g / L, the content of ammonium polyphosphate is 100 g / L, and the content of dicyandiamide is 50 g / L;

[0075] (3) Cotton fabric (manufacturer: Guangdong Dongguan Weiman Baida Textile Co., Ltd., with a surface density of 100 g / m 2 ) is immersed in the flame retardant liquid obtained in step (2), and then oscillated at 55°C for 20 minutes and then padded, followed by pre-baking at 90°C for 2 minutes, and finally baked at 170°C for 4 minutes to obtain a durable flame retardant cotton fabric; wherein the padding rate of the padding treatment is 95%.

[0076] The final durable flame-retardant cotton fabric has a breaking strength of 470N, a limiting oxygen index of 33.1%, and a damage length of 8.2cm. After 50 washes, it can still pass the vertical burning test with a damage length of 12.6cm.

Claims

1. A method for preparing a durable flame retardant cotton fabric, characterized in that: The reactive cyclotriphosphazene flame retardant, ammonium polyphosphate and dicyandiamide are dissolved in an organic solvent to obtain a flame retardant liquid, cotton fabric is immersed in the flame retardant liquid for padding treatment, and then pre-baked and baked in sequence to obtain a durable flame retardant cotton fabric; The chemical formula of reactive cyclotriphosphazene flame retardant is .

2. The method for preparing a durable flame retardant cotton fabric according to claim 1, characterized in that: The preparation method of the reactive cyclotriphosphazene flame retardant comprises the following steps: dissolving hexachlorocyclotriphosphazene and triethanolamine in chloroform, using triethylamine as an acid binding agent, reacting for a certain time, then adding methanol to continue the reaction for a certain time, and finally performing reduced pressure distillation and washing with ethanol to obtain the reactive cyclotriphosphazene flame retardant; The reaction temperature is 20~30°C, the reaction is carried out for 4~5 hours before adding methanol, and the reaction is continued for 4~5 hours after adding methanol.

3. The method for preparing a durable flame retardant cotton fabric according to claim 2, characterized in that: The molar ratio of hexachlorocyclotriphosphazene to triethanolamine is 1:3-3.3, the molar ratio of hexachlorocyclotriphosphazene to triethylamine is 1:6-8, and the molar ratio of hexachlorocyclotriphosphazene to methanol is 1:3-3.

3.

4. The method for preparing a durable flame retardant cotton fabric according to claim 1, characterized in that: The organic solvent is a mixture of N,N-dimethylformamide and distilled water, and N,N-dimethylformamide accounts for 20-30% of the total volume of the organic solvent.

5. The method for preparing a durable flame retardant cotton fabric according to claim 1, characterized in that: The content of reactive cyclotriphosphazene flame retardant in the flame retardant liquid is 30-50 g / L, the content of ammonium polyphosphate is 70-100 g / L, and the content of dicyandiamide is 40-50 g / L.

6. The method for preparing a durable flame retardant cotton fabric according to claim 1, characterized in that: The cotton fabric is immersed in the flame retardant liquid with a bath ratio of 1:30~40, first oscillated at 50~55℃ for 20~30min, and then padded.

7. The method for preparing a durable flame retardant cotton fabric according to claim 1, characterized in that: The rolling rate of the padding treatment is 90~100%.

8. The method for preparing a durable flame retardant cotton fabric according to claim 1, characterized in that: The pre-baking temperature is 80~90℃ and the time is 2~3min; the baking temperature is 160~170℃ and the time is 4~5min.

9. The method for preparing a durable flame-retardant cotton fabric according to any one of claims 1 to 8, characterized in that: The breaking strength of the durable flame-retardant cotton fabric is not less than 470N, the limiting oxygen index is not less than 29.5%, the damaged length is not higher than 9.8cm, and it can still pass the vertical burning test after 50 washes, and the damaged length is not higher than 14.6cm.

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