Durable flame-retardant cotton fabric and in-situ deposition cross-linking preparation method

Abstract

The invention belongs to the technical field of cotton fabric modification, and relates to a durable flame-retardant cotton fabric and an in-situ deposition cross-linking preparation method. The durable flame-retardant cotton fabric is mainly composed of cotton fabric and insoluble precipitates dispersed on the surface and inside of the cotton fiber at the same time. The insoluble precipitate is generated by combining ammonium polyphosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensation product by electrostatic attraction, and the insoluble precipitate is covalently bonded to the cotton fiber. The in-situ deposition cross-linking preparation method is: after tetrakis(hydroxymethyl)phosphonium chloride, ammonium polyphosphate and cotton fabric are simultaneously added to the aqueous solution of dicyandiamide to obtain a system consisting of a flame retardant liquid and cotton fabric, after oscillating at 60-70°C, pre-baking at 70-80°C and baking at 165-175°C in sequence, a durable flame-retardant cotton fabric is obtained. The durable flame-retardant cotton fabric of the present invention has excellent flame retardant properties and water washability, and the preparation conditions are mild, the process is simple, and it is suitable for large-scale industrial applications.

Description

Technical Field

[0001] The invention belongs to the technical field of cotton fabric modification, and in particular relates to a durable flame-retardant cotton fabric and an in-situ deposition cross-linking preparation method. Background Art

[0002] Cotton fabric is one of the most popular natural textiles. It is widely used in clothing, packaging and other fields due to its excellent moisture absorption and breathability, skin-friendliness and softness. However, the extremely flammable nature of cotton fabric limits its application, so it is of great significance to modify cotton fabric to be flame retardant.

[0003] At present, tetrakis hydroxymethyl phosphonium salt is widely used in flame retardant finishing of cotton fabrics. There are two main methods:

[0004] The first method is to react tetrakis(hydroxymethyl)phosphonium chloride with urea to react, and use the condensation product as a flame retardant for cotton fabrics. Since the condensation product has a certain water solubility, it is necessary to use ammonia fumigation to reduce the water solubility of the condensation product and deposit it inside the cotton fiber when treating the cotton fabric. However, the ammonia fumigation treatment not only has high equipment prices, but also has great pollution during the treatment process. At the same time, since the condensation product cannot be combined with the cotton fiber through covalent bonds, the flame retardant durability of the final cotton fabric is also poor.

[0005] The second method is to use tetrakis(hydroxymethyl)phosphonium sulfate and melamine as raw materials to flame retardant finish the cotton fabric. For example, the literature ("Research on Flame Retardant Properties of Cotton Fabrics Loaded with RGO / MTHPS", Lin Jiayao et al., Industrial Textiles, 2020, 38(6):34-39) uses tetrakis(hydroxymethyl)phosphonium sulfate and melamine as raw materials to synthesize the phosphorus-nitrogen synergistic intumescent flame retardant melamine tetrakis(hydroxymethyl)phosphonium sulfate, and loads reduced graphene oxide and melamine tetrakis(hydroxymethyl)phosphonium sulfate onto cotton fabric. Reduced graphene oxide and melamine tetrakis(hydroxymethyl)phosphonium sulfate are insoluble in water. They are dispersed in an aqueous solution to flame retardant finish the cotton fabric. The obtained cotton fabric has good flame retardant properties; however, since the flame retardant system cannot be well combined with cotton fabric, the flame retardant durability of the flame retardant cotton fabric is very poor.

[0006] In addition, there are cases in the prior art where the condensation product of tetrakis(hydroxymethyl)phosphonium chloride and dicyandiamide is used as a flame retardant to treat goat leather ("Study on in situ combined tanning of THP salt and dicyandiamide", Li Ya et al., Fine Chemicals, 2006, 23(8):797-800). However, it has been found through research that the condensation product has a high water solubility and cannot be firmly combined with cotton fabrics. If it is used to perform flame retardant treatment on cotton fabrics, the flame retardant durability of the resulting cotton fabrics will obviously be poor.

[0007] Therefore, there is an urgent need to develop a cotton fabric with good flame retardancy and durability. Summary of the invention

[0008] The purpose of the present invention is to solve the problems existing in the prior art and provide a durable flame-retardant cotton fabric and an in-situ deposition cross-linking preparation method.

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

[0010] A method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking comprises the following steps: adding tetrakis(hydroxymethyl)phosphonium chloride, ammonium polyphosphate and cotton fabric to an aqueous solution of dicyandiamide to obtain a system consisting of a flame-retardant liquid and cotton fabric, shaking the system at 60-70°C, pre-baking the system at 70-80°C and baking the system at 165-175°C to obtain the durable flame-retardant cotton fabric.

[0011] The following changes occur during the above “oscillation” process:

[0012] ① Dicyandiamide, tetrakis(hydroxymethyl)phosphonium chloride and ammonium polyphosphate adhere to the surface of cotton fibers and diffuse into the interior of cotton fibers;

[0013] ② On the surface or inside of cotton fiber, the hydroxymethyl group of tetrakis(hydroxymethyl)phosphonium chloride reacts with the amino group and cyano group of dicyandiamide to generate a tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate rich in cationic amino groups;

[0014] ③ On the surface or inside of cotton fibers, ammonium polyphosphate rich in anionic phosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate combine through electrostatic attraction to form insoluble precipitates;

[0015] ④ The ammonium phosphate structure in the insoluble precipitate undergoes esterification reaction with the hydroxyl group of the cotton fiber;

[0016] The following changes will occur during the above-mentioned "pre-baking" and "baking" processes:

[0017] ① Dicyandiamide, tetrakis(hydroxymethyl)phosphonium chloride and ammonium polyphosphate attached to the surface of cotton fibers diffuse into the interior of cotton fibers;

[0018] ② On the surface or inside of cotton fiber, the hydroxymethyl group of tetrakis(hydroxymethyl)phosphonium chloride reacts with the amino group and cyano group of dicyandiamide to generate a tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate rich in cationic amino groups;

[0019] ③ On the surface or inside of cotton fibers, ammonium polyphosphate rich in anionic phosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate combine through electrostatic attraction to form insoluble precipitates;

[0020] ④ The ammonium phosphate structure in the insoluble precipitate undergoes esterification reaction with the hydroxyl group of the cotton fiber;

[0021] Therefore, in the durable flame-retardant cotton fabric finally obtained, insoluble precipitates are dispersed on the surface and inside of the cotton fibers. The insoluble precipitates located inside the cotton fibers are difficult to separate from the fibers due to their size. At the same time, they can also form covalent bonds with the cotton fibers, so they are even more difficult to separate from the fibers. Although the insoluble precipitates located outside the cotton fibers are exposed to the outside, they can form covalent bonds with the cotton fibers, so they will not be easily separated from the fibers after multiple washings. At the same time, the phosphate structure and the dicyandiamide nitrogen-containing structure in the insoluble precipitates can produce a synergistic flame retardant effect, and the flame retardant effect is better. Therefore, the durable flame retardant cotton fabric has excellent flame retardant properties and water washability.

[0022] As the preferred technical solution:

[0023] In the method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking as described above, in the flame-retardant liquid, the concentration of tetrakis(hydroxymethyl)phosphonium chloride is 80-150 g / L, the concentration of dicyandiamide is 50-70 g / L, and the concentration of ammonium polyphosphate is 50-70 g / L.

[0024] In the above-mentioned method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the degree of polymerization of ammonium polyphosphate is less than 20 (the product is purchased from: McLean, item number A875114).

[0025] In the above-mentioned method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the ratio of cotton fabric to flame-retardant liquid is 1g:30-40mL. The larger the bath ratio, the more conducive it is to uniformly treat the cotton fabric, but too high a bath ratio will result in waste.

[0026] In the above-mentioned method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the oscillation treatment adopts XW-ZDR oscillating dyeing machine (Jingjiang Xinwang), the oscillation treatment time is 30-50 minutes, and the oscillation treatment frequency is 80-100 times / minute.

[0027] In the above-mentioned method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the pre-baking time is 2-3 minutes.

[0028] In the above-mentioned method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the baking time is 3-5 minutes.

[0029] The present invention also provides a durable flame-retardant cotton fabric prepared by the method for preparing a durable flame-retardant cotton fabric by in-situ deposition cross-linking as described in any of the above items, which mainly consists of cotton fabric and insoluble precipitates dispersed on the surface and inside of cotton fibers at the same time, wherein the insoluble precipitates are generated by combining ammonium polyphosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensation product through electrostatic attraction, and the insoluble precipitates are bonded to the cotton fibers through covalent bonds.

[0030] As the preferred technical solution:

[0031] The durable flame retardant cotton fabric as described above has a limiting oxygen index of not less than 29.7% (the limiting oxygen index of the unmodified cotton fabric is 18.2%), a damaged length of not more than 10.9 cm (the damaged length of the unmodified cotton fabric is 30 cm), and after 50 times of washing, the damaged length is still less than 14.6 cm, and has excellent flame retardant properties and washability.

[0032] Beneficial effects:

[0033] 1. In the durable flame-retardant cotton fabric prepared by the present invention, the surface and interior of the cotton fiber are bonded with insoluble precipitates through strong covalent bonds, so that the durable flame-retardant cotton fabric has excellent water-washing resistance. At the same time, the insoluble precipitates are generated by combining ammonium polyphosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensation product through electrostatic attraction. The phosphate structure and the dicyandiamide nitrogen-containing structure can produce a synergistic flame-retardant effect, so that the flame-retardant performance of the durable flame-retardant cotton fabric is more excellent.

[0034] 2. The limiting oxygen index of the durable flame-retardant cotton fabric prepared by the present invention is not less than 29.7% (the limiting oxygen index of the unmodified cotton fabric is 18.2%), the damaged length is not higher than 10.9 cm (the damaged length of the unmodified cotton fabric is 30 cm), and the damaged length is still less than 14.6 cm after 50 washings.

[0035] 3. The preparation method provided by the present invention adopts an aqueous solution, does not contain organic solvents and strong acids and bases, has mild preparation conditions, simple processes, and is suitable for large-scale industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a result diagram of a vertical burning test (damage length) of cotton fabric in Example 3 of the present invention;

[0037] Figure 2 This is a result diagram of a vertical burning test (damage length) of the durable flame retardant cotton fabric of Example 3 of the present invention;

[0038] Figure 3 This is the infrared spectrum of the insoluble precipitate of Example 1 of the present invention. DETAILED DESCRIPTION

[0039] 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.

[0040] The following are the test methods for the relevant performance indicators in each embodiment and comparative example:

[0041] Limiting oxygen index: Tested in accordance with GB / T 5454-1997 "Oxygen Index Method for Textile Combustion Performance Test".

[0042] Damage length: Tested in accordance with GB / T 5455-2014 “Determination of vertical damage length, smoldering and afterflaming time of textile combustion performance”.

[0043] Damaged length of fabric after 50 washes: first wash the fabric 50 times with reference to AATCC 61-2013 "Accelerated test for color fastness to household and commercial washing" standard, and then test the damaged 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.

[0044] Example 1

[0045] A method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the specific steps are as follows:

[0046] (1) Preparation of raw materials;

[0047] An aqueous solution of dicyandiamide;

[0048] Tetrakis hydroxymethyl phosphonium chloride;

[0049] Ammonium polyphosphate: degree of polymerization less than 20 (purchased from: McLean, product number A875114);

[0050] Cotton fabric: Limiting oxygen index is 18.2%, and the damaged length is 30cm;

[0051] (2) Tetrakis(hydroxymethyl)phosphonium chloride, ammonium polyphosphate and cotton fabric are simultaneously added to an aqueous solution of dicyandiamide to obtain a system consisting of a flame retardant liquid and cotton fabric, and then the system is subjected to an oscillation treatment at a temperature of 70°C and a frequency of 90 times / min for 30 min, and then pre-baked at 80°C for 2 min and baked at 175°C for 3 min to obtain a durable flame retardant cotton fabric; wherein the concentration of tetrakis(hydroxymethyl)phosphonium chloride in the flame retardant liquid is 120 g / L, the concentration of dicyandiamide is 60 g / L, and the concentration of ammonium polyphosphate is 60 g / L; and the ratio of cotton fabric to flame retardant liquid is 1 g:30 mL.

[0052] The durable flame-retardant cotton fabric finally produced is mainly composed of cotton fabric and insoluble precipitates dispersed on the surface and inside of the cotton fibers. The insoluble precipitates are generated by the combination of ammonium polyphosphate and tetrakishydroxymethylphosphonium chloride-dicyandiamide condensation product through electrostatic attraction, and the insoluble precipitates are bonded to the cotton fibers through covalent bonds; the limiting oxygen index of the durable flame-retardant cotton fabric is 31.5%, and the damaged length is 9.3 cm; the damaged length of the durable flame-retardant cotton fabric after 50 washes is 13.8 cm.

[0053] In order to prove that insoluble precipitates are indeed generated during the above oscillation process, the following experiment is conducted:

[0054] After adding tetrakis(hydroxymethyl)phosphonium chloride and ammonium polyphosphate to an aqueous solution of dicyandiamide to obtain a flame retardant liquid, the solution is first subjected to an oscillation treatment at a temperature of 70°C and a frequency of 90 times / min for 30 minutes, and then subjected to freeze-drying to obtain a precipitate, and then the precipitate is purified and dried to obtain an insoluble precipitate; wherein, in the flame retardant liquid, the concentration of tetrakis(hydroxymethyl)phosphonium chloride is 120 g / L, the concentration of dicyandiamide is 60 g / L, and the concentration of ammonium polyphosphate is 60 g / L;

[0055] The infrared spectrum of the insoluble precipitate obtained above is as follows Figure 3 As shown, it can be seen that the insoluble precipitate is indeed formed by the combination of ammonium polyphosphate rich in anionic phosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate through electrostatic attraction, and does contain ammonium phosphate structure.

[0056] Comparative Example 1

[0057] A method for preparing a flame retardant cotton fabric is basically the same as that in Example 1, except that the temperature of the oscillation treatment in step (2) is 45°C.

[0058] The damaged length of the flame-retardant cotton fabric finally obtained was 10.9 cm, and the damaged length after 50 times of washing was 30 cm.

[0059] Compared with Example 1, the flame retardant durability of the flame retardant cotton fabric in Comparative Example 1 is significantly worse. This is because the temperature of the oscillation treatment in Comparative Example 1 is too low, so that dicyandiamide, tetrakis(hydroxymethyl)phosphonium chloride, and ammonium polyphosphate cannot be fully attached to the surface of the cotton fiber, and it is difficult to diffuse into the fiber. Only insoluble precipitates are generated on the surface of the cotton fabric. In the washing process, the insoluble precipitates are easily taken away by the washing liquid, resulting in the loss of the flame retardant effect; too low a temperature will also cause the condensation reaction rate between the hydroxymethyl of tetrakis(hydroxymethyl)phosphonium chloride and the amino and cyano groups of dicyandiamide to drop significantly, and the amount of the tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate rich in cationic amino groups is significantly reduced; in addition, too low a temperature is not conducive to the ammonium polyphosphate rich in anionic phosphate and the tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate to fully combine through electrostatic attraction to form an insoluble precipitate, which ultimately leads to a significant increase in the damage length of the flame retardant cotton fabric after 50 washings, and a significant decrease in the flame retardant durability.

[0060] Comparative Example 2

[0061] A method for preparing a flame retardant cotton fabric is basically the same as that of Example 1, except that ammonium polyphosphate is replaced by trimethyl phosphate of equal mass.

[0062] The damaged length of the flame-retardant cotton fabric finally obtained was 10.5 cm, and the damaged length after 50 times of washing was 30 cm.

[0063] Compared with Example 1, the flame retardant durability of Comparative Example 2 is significantly deteriorated. This is because trimethyl phosphate does not contain anionic phosphate and cannot combine with tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensation product through electrostatic attraction to form a precipitate, resulting in the inability to deposit a sufficient amount of insoluble flame retardant inside and on the surface of the fiber, resulting in poor flame retardant durability.

[0064] Example 2

[0065] A method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the specific steps are as follows:

[0066] (1) Preparation of raw materials;

[0067] An aqueous solution of dicyandiamide;

[0068] Tetrakis hydroxymethyl phosphonium chloride;

[0069] Ammonium polyphosphate: degree of polymerization less than 20 (purchased from: McLean, product number A875114);

[0070] Cotton fabric: Limiting oxygen index is 18.2%, and the damaged length is 30cm;

[0071] (2) After adding tetrakis(hydroxymethyl)phosphonium chloride, ammonium polyphosphate and cotton fabric to an aqueous solution of dicyandiamide to obtain a system consisting of a flame retardant liquid and cotton fabric, the system was subjected to oscillation treatment at a temperature of 65°C and a frequency of 85 times / min for 40 min, and then pre-baked at 75°C for 2.5 min and baked at 170°C for 4 min to obtain a durable flame retardant cotton fabric; wherein the concentration of tetrakis(hydroxymethyl)phosphonium chloride in the flame retardant liquid was 100 g / L, the concentration of dicyandiamide was 55 g / L, and the concentration of ammonium polyphosphate was 55 g / L; and the ratio of cotton fabric to flame retardant liquid was 1 g:35 mL.

[0072] The durable flame-retardant cotton fabric finally produced is mainly composed of cotton fabric and insoluble precipitates dispersed on the surface and inside of the cotton fibers. The insoluble precipitates are generated by the combination of ammonium polyphosphate and tetrakishydroxymethylphosphonium chloride-dicyandiamide condensation product through electrostatic attraction, and the insoluble precipitates are bonded to the cotton fibers through covalent bonds; the limiting oxygen index of the durable flame-retardant cotton fabric is 30.8%, and the damaged length is 10.1 cm; the damaged length of the durable flame-retardant cotton fabric after 50 washings is 14.1 cm.

[0073] Example 3

[0074] A method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the specific steps are as follows:

[0075] (1) Preparation of raw materials;

[0076] An aqueous solution of dicyandiamide;

[0077] Tetrakis hydroxymethyl phosphonium chloride;

[0078] Ammonium polyphosphate: degree of polymerization less than 20 (purchased from: McLean, product number A875114);

[0079] Cotton fabric: Limiting oxygen index is 18.2%, and the damaged length is 30cm;

[0080] (2) After adding tetrakis(hydroxymethyl)phosphonium chloride, ammonium polyphosphate and cotton fabric to an aqueous solution of dicyandiamide to obtain a system consisting of a flame retardant liquid and cotton fabric, the system was subjected to an oscillation treatment at a temperature of 60°C and a frequency of 80 times / min for 50 min, and then pre-baked at 70°C for 3 min and baked at 165°C for 5 min to obtain a durable flame retardant cotton fabric; wherein the concentration of tetrakis(hydroxymethyl)phosphonium chloride in the flame retardant liquid was 80 g / L, the concentration of dicyandiamide was 50 g / L, and the concentration of ammonium polyphosphate was 50 g / L; and the ratio of cotton fabric to flame retardant liquid was 1 g:40 mL.

[0081] The durable flame-retardant cotton fabric finally produced is mainly composed of cotton fabric and insoluble precipitates dispersed on the surface and inside of the cotton fibers. The insoluble precipitates are generated by the electrostatic attraction of ammonium polyphosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensation product, and the insoluble precipitates are bonded to the cotton fibers through covalent bonds. The limiting oxygen index of the durable flame-retardant cotton fabric is 29.7%, and the damaged length is 10.9 cm. The damaged length of the durable flame-retardant cotton fabric after 50 washes is 14.6 cm.

[0082] The vertical burning test results of the raw material (cotton fabric) used in this example are as follows: Figure 1 As shown, the vertical burning test results of the durable flame retardant cotton fabric prepared in this embodiment are as follows Figure 2 As shown, from Figure 1 It can be seen that the raw cotton fabric was completely destroyed after the vertical burning test, while Figure 2 The durable flame-retardant cotton fabric prepared in this embodiment showed good flame-retardant effect in the vertical burning test, and the degree of damage was significantly reduced, which fully demonstrated the effectiveness of the in-situ deposition preparation method adopted in this embodiment in improving the flame-retardant properties of cotton fabrics.

[0083] Example 4

[0084] A method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the specific steps are as follows:

[0085] (1) Preparation of raw materials;

[0086] An aqueous solution of dicyandiamide;

[0087] Tetrakis hydroxymethyl phosphonium chloride;

[0088] Ammonium polyphosphate: degree of polymerization less than 20 (purchased from: McLean, product number A875114);

[0089] Cotton fabric: Limiting oxygen index is 18.2%, and the damaged length is 30cm;

[0090] (2) Tetrakis(hydroxymethyl)phosphonium chloride, ammonium polyphosphate and cotton fabric are simultaneously added to an aqueous solution of dicyandiamide to obtain a system consisting of a flame retardant liquid and cotton fabric, and then the system is subjected to an oscillation treatment at a temperature of 65°C and a frequency of 95 times / min for 45 min, and then pre-baked at 75°C for 2.5 min and baked at 170°C for 3.5 min to obtain a durable flame retardant cotton fabric; wherein the concentration of tetrakis(hydroxymethyl)phosphonium chloride in the flame retardant liquid is 135 g / L, the concentration of dicyandiamide is 65 g / L, and the concentration of ammonium polyphosphate is 65 g / L; and the ratio of cotton fabric to flame retardant liquid is 1 g:35 mL.

[0091] The durable flame-retardant cotton fabric finally produced is mainly composed of cotton fabric and insoluble precipitates dispersed on the surface and inside of the cotton fibers. The insoluble precipitates are generated by the combination of ammonium polyphosphate and tetrakishydroxymethylphosphonium chloride-dicyandiamide condensation product through electrostatic attraction, and the insoluble precipitates are bonded to the cotton fibers through covalent bonds; the limiting oxygen index of the durable flame-retardant cotton fabric is 31.9%, and the damaged length is 8.5 cm; the damaged length of the durable flame-retardant cotton fabric after 50 washes is 13.4 cm.

[0092] Example 5

[0093] A method for preparing durable flame-retardant cotton fabric by in-situ deposition cross-linking, the specific steps are as follows:

[0094] (1) Preparation of raw materials;

[0095] An aqueous solution of dicyandiamide;

[0096] Tetrakis hydroxymethyl phosphonium chloride;

[0097] Ammonium polyphosphate: degree of polymerization less than 20 (purchased from: McLean, product number A875114);

[0098] Cotton fabric: Limiting oxygen index is 18.2%, and the damaged length is 30cm;

[0099] (2) Tetrakis(hydroxymethyl)phosphonium chloride, ammonium polyphosphate and cotton fabric are simultaneously added to an aqueous solution of dicyandiamide to obtain a system consisting of a flame retardant liquid and cotton fabric, and then the system is subjected to an oscillation treatment at a temperature of 70°C and a frequency of 100 times / min for 40 min, and then pre-baked at 70°C for 3 min and baked at 165°C for 5 min to obtain a durable flame retardant cotton fabric; wherein the concentration of tetrakis(hydroxymethyl)phosphonium chloride in the flame retardant liquid is 150 g / L, the concentration of dicyandiamide is 70 g / L, and the concentration of ammonium polyphosphate is 70 g / L; and the ratio of cotton fabric to flame retardant liquid is 1 g:40 mL.

[0100] The durable flame-retardant cotton fabric finally produced is mainly composed of cotton fabric and insoluble precipitates dispersed on the surface and inside of the cotton fibers. The insoluble precipitates are generated by the electrostatic attraction of ammonium polyphosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensation product, and the insoluble precipitates are bonded to the cotton fibers through covalent bonds. The limiting oxygen index of the durable flame-retardant cotton fabric is 32.4%, and the damaged length is 8.1 cm. The damaged length of the durable flame-retardant cotton fabric after 50 washes is 13.1 cm.

Claims

1. A method for preparing durable flame-retardant cotton fabric by in-situ deposition crosslinking, characterized in that: Tetrakis(hydroxymethyl)phosphonium chloride, ammonium polyphosphate and cotton fabric are simultaneously added to an aqueous solution of dicyandiamide to obtain a system consisting of a flame retardant liquid and cotton fabric, and then the system is shaken at 60-70°C, pre-baked at 70-80°C and baked at 165-175°C to obtain a durable flame retardant cotton fabric; wherein the degree of polymerization of the ammonium polyphosphate is less than 20, the shaking treatment time is 30-50 minutes, and the shaking treatment frequency is 80-100 times / minute.

2. The method for preparing durable flame-retardant cotton fabric by in-situ deposition crosslinking according to claim 1, characterized in that: In the flame retardant liquid, the concentration of tetrakis(hydroxymethyl)phosphonium chloride is 80-150 g / L, the concentration of dicyandiamide is 50-70 g / L, and the concentration of ammonium polyphosphate is 50-70 g / L.

3. The method for preparing durable flame-retardant cotton fabric by in-situ deposition crosslinking according to claim 2, characterized in that: The ratio of cotton fabric to flame retardant liquid is 1g:30-40mL.

4. The method for preparing durable flame-retardant cotton fabric by in-situ deposition crosslinking according to claim 1, characterized in that: The pre-baking time is 2-3 minutes.

5. The method for preparing durable flame-retardant cotton fabric by in-situ deposition crosslinking according to claim 1, characterized in that: The baking time is 3-5 minutes.

6. The durable flame retardant cotton fabric prepared by the method for preparing a durable flame retardant cotton fabric by in-situ deposition crosslinking according to any one of claims 1 to 5, characterized in that: It is mainly composed of cotton fabric and insoluble precipitates dispersed on the surface and inside of cotton fibers. The insoluble precipitates are generated by the combination of ammonium polyphosphate and tetrakis(hydroxymethyl)phosphonium chloride-dicyandiamide condensate through electrostatic attraction. The insoluble precipitates are combined with cotton fibers through covalent bonds.

7. The durable flame retardant cotton fabric according to claim 6, characterized in that: The limiting oxygen index of the durable flame-retardant cotton fabric is not less than 29.7%, the damaged length is not higher than 10.9 cm, and after 50 washes, the damaged length is still less than 14.6 cm.

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