Modified pa56 fabric with long-lasting flame retardant effect and preparation method thereof

Abstract

The application relates to a modified PA56 fabric with long-acting flame-retardant effect and a preparation method thereof, wherein hyperbranched polyethylene imine and ammonium polyphosphate are grafted to obtain hyperbranched modified ammonium polyphosphate, the PA56 fabric is dipped in a hyperbranched modified ammonium polyphosphate solution and dried and solidified, dipped in a melamine flame-retardant finishing agent, then dipped in an acetic acid buffer solution, and dried to obtain the modified PA56 fabric with long-acting flame-retardant effect. Different from the prior art, the hyperbranched modified ammonium polyphosphate is loaded on the PA56 fabric to form a crosslinked network structure; the polyethylene imine is loaded on the PA56 fabric; the ammonium polyphosphate is connected with the polyethylene imine through grafting modification; the melamine is connected with the ammonium polyphosphate through weak bonds such as electrostatic interaction, hydrogen bond and P-N bond, and is wrapped in the outer layer of the fabric, so that the durable flame-retardant effect of the modified PA56 fabric is realized, and the strength of the modified PA fabric is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of textiles, in particular to a modified PA56 fabric with long-term flame-retardant effect and a preparation method thereof. BACKGROUND

[0002] Nylon fabric is widely used in various fields due to its excellent mechanical properties and wear resistance, including clothing, industrial manufacturing and military equipment. Nylon fiber, also known as polyamide (PA) fiber, has excellent thermal performance, mechanical properties, processing performance and moisture absorption and dyeing performance. Among them, bio-based nylon 56 (PA56) is obtained by polymerization of bio-based 1,5-pentanediamine and adipic acid. In addition to the advantages of conventional nylon, it also has its own advantages such as environmental protection and sustainable development, and has good application and development prospects.

[0003] However, like ordinary high molecular polymers, PA56 will gradually melt, molecular rupture and pyrolysis as the temperature rises, releasing a large amount of heat to cause flame spread. In recent years, fires caused by high molecular materials have caused huge economic losses and casualties, so flame-retardant modification of PA56 has become an urgent problem to be solved.

[0004] At present, the common flame-retardant modification methods of polyamide products are blending flame-retardant modification, copolymerization flame-retardant modification and flame-retardant finishing. Although the modification method of directly preparing flame-retardant polyamide by directly mixing polyamide masterbatch with flame retardant has the advantages of low cost and easy processing, it is easy to cause strength damage to polyamide products. The copolymerization flame-retardant modification can obtain better flame-retardant performance and maintain the mechanical properties of the product by grafting the reactive flame retardant to the main chain or side chain of polyamide, but the production cost is high and the industrial application is limited. Flame-retardant finishing is a modification method of loading flame-retardant finishing agent onto polyamide fiber or fabric by surface grafting or coating. Compared with copolymerization flame-retardant modification, its cost is relatively low, but the flame-retardant durability is poor and the mechanical properties of the product are easily reduced during the finishing process. SUMMARY

[0005] In view of the above problems, the present application provides a method of flame-retardant finishing to obtain a modified PA56 fabric with long-term flame-retardant effect and mechanical strength.

[0006] The first aspect of the present application provides a preparation method of a modified PA56 fabric with long-term flame-retardant effect, comprising the following steps:

[0007] S1: grafting treatment of hyperbranched polyethyleneimine and ammonium polyphosphate to obtain hyperbranched modified ammonium polyphosphate; S2: adding the hyperbranched modified ammonium polyphosphate into deionized water to obtain a polyelectrolyte solution;

[0008] S3: the PA56 fabric is first padded in the polyelectrolyte solution, dried to obtain a polyelectrolyte-PA56 treated fabric;

[0009] S4: the polyelectrolyte-PA56 treated fabric is secondly padded in a melamine solution to obtain a melamine-polyelectrolyte-PA56 treated fabric;

[0010] S5: the melamine-polyelectrolyte-PA56 treated fabric is thirdly padded in an acetate buffer solution, dried to obtain the modified PA56 fabric with long-lasting flame-retardant effect.

[0011] Different from the prior art, the hyperbranched modified ammonium polyphosphate is loaded on the PA56 fabric to form a crosslinked network structure; the polyethyleneimine is loaded on the PA56 fabric; the ammonium polyphosphate is connected to the polyethyleneimine through graft modification; the melamine is connected to the ammonium polyphosphate through electrostatic interaction, hydrogen bond, P-N bond and other weak bonds, and is wrapped on the outer layer of the fabric, so as to realize the durable flame-retardant effect of the modified PA56 fabric. At the same time, a large number of amine groups in the polyethyleneimine are hydroxylated, and a crosslinked network structure is formed between the PA56 fiber and the polyethyleneimine through hydrogen bond and other forces, so as to improve the cohesive strength of the PA56 fabric fiber, and further improve the strength of the modified PA fabric.

[0012] Further, in the S1 step, the mass ratio of the hyperbranched polyethyleneimine ethanol to the ammonium polyphosphate is 30-40:100-120.

[0013] Further, in the S1 step, 30-40 g / L of the hyperbranched polyethyleneimine ethanol solution is added to 100-120 g / L of the ammonium polyphosphate, and the hyperbranched polyethyleneimine and the ammonium polyphosphate are grafted by stirring at 20-50℃ for 60-80 min to obtain a first mixed solution; the first mixed solution is heated to 70-80℃ to evaporate the ethanol solvent to obtain a white solid; and the white solid is dried at 50-60℃ to obtain the hyperbranched modified ammonium polyphosphate.

[0014] Further, in the S2 step, the mass percentage concentration of the polyelectrolyte solution is 5-15wt%.

[0015] Further, in the S3 step, the first padding time is 30-120 s, the drying temperature is 60-70℃, and the drying time is 20-30 min.

[0016] Further, in the S4 step, the preparation method of the melamine solution is as follows: the melamine is dissolved in 0.5-2wt% of an acetic acid solution to obtain the melamine solution; and the mass percentage concentration of the melamine solution is 1-4wt%.

[0017] Further, in the S4 step, the time of the secondary padding is 30-60s, and the padding temperature is 40-60℃.

[0018] Further, in the S5 step, the pH of the acetate buffer is 3-6.

[0019] Further, in the S5 step, the time of the third padding is 5-8min, the drying temperature is 70-80℃, and the drying time is 20-30min.

[0020] The second aspect of the present application provides a modified PA56 fabric with long-term flame retardant effect, which is prepared by the preparation method of the first aspect of the present application.

[0021] The above summary is only a summary of the technical scheme of the present application, in order to enable those skilled in the art to more clearly understand the technical scheme of the present application, and then can be implemented according to the content of the description of the text, and in order to let the above-mentioned purpose and other purposes, characteristics and advantages of the present application can be more easily understood, the following is described in combination with the specific embodiment of the present application and the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings are only used to show the principles, implementation manners, applications, characteristics and effects of the specific embodiments of the present application and other related contents, and cannot be considered as the limitation of the present application.

[0023] In the drawings of the specification:

[0024] Figure 1 It is the synthesis route map of hyperbranched modified ammonium polyphosphate.

[0025] Figure 2 It is the performance comparison chart of different amounts of hyperbranched modified ammonium polyphosphate in examples 1-5.

[0026] Figure 3 It is the performance comparison chart of different amounts of melamine in examples 1, 6-9.

[0027] Figure 4 It is the performance comparison chart of different amounts of polyphosphate in comparative examples 1-5.

[0028] Figure 5 It is the performance comparison chart of different amounts of hyperbranched polyethyleneimine in comparative examples 6-10. DETAILED DESCRIPTION

[0029] To explain possible application scenarios, technical principles, specific implementation schemes, and the purposes and effects of the present application in detail, the following embodiments are described in conjunction with the accompanying drawings. The embodiments described herein are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0030] In this paper, the term "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The term "embodiment" appearing at various places in the specification does not necessarily refer to the same embodiment, and does not particularly limit its independence or association with other embodiments. In principle, in the present application, as long as there is no technical contradiction or conflict, each technical feature mentioned in each embodiment can be combined in any way to form a corresponding implementable technical solution.

[0031] Unless otherwise defined, the meaning of the technical terms used herein is the same as that generally understood by those skilled in the art to which the present application belongs; the use of related terms herein is only for the purpose of describing specific embodiments, and is not intended to limit the present application.

[0032] In the description of the present application, the phrase "and / or" is a description of the logical relationship between the objects, which means that there can be three relationships, for example, A and / or B, which means that there are three cases: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this paper generally represents that the associated objects before and after are a "or" logical relationship.

[0033] In the present application, terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual quantity, primary and secondary or order relationship between the entities or operations.

[0034] Without more limitations, in the present application, the phrases "include", "contain", "have" or other similar expressions used in the sentence are intended to cover non-exclusive inclusion, and these expressions do not exclude the presence of other elements in the process, method or product including the described elements, so that the process, method or product including a series of elements can not only include those limited elements, but also include other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0035] As the same as the understanding in the "Examination Guidelines", in the present application, "greater than", "less than", "exceed" and the like are understood as not including the number; "above", "below", "within" and the like are understood as including the number. In addition, in the description of the embodiments of the present application, the meaning of "multiple" is two or more (including two), and similar expressions related to "multiple" are also understood in this way, for example, "multiple groups", "multiple times" and the like, unless otherwise explicitly and specifically limited.

[0036] The first aspect of the present application provides a preparation method of a modified PA56 fabric with long-acting flame-retardant effect, comprising the following steps:

[0037] S1: grafting treatment of hyperbranched polyethyleneimine and ammonium polyphosphate to obtain hyperbranched modified ammonium polyphosphate; S2: adding the hyperbranched modified ammonium polyphosphate into deionized water to obtain a polyelectrolyte solution;

[0038] S3: first padding of PA56 fabric in the polyelectrolyte solution, drying to obtain a polyelectrolyte-PA56 treated fabric;

[0039] S4: second padding of the polyelectrolyte-PA56 treated fabric in a melamine solution to obtain a melamine-polyelectrolyte-PA56 treated fabric;

[0040] S5: third padding of the melamine-polyelectrolyte-PA56 treated fabric in an acetate buffer solution, drying to obtain the modified PA56 fabric with long-acting flame-retardant effect.

[0041] The synthesis route of the hyperbranched modified ammonium polyphosphate is as shown in Figure 1 .

[0042] Ammonium polyphosphate and polyethyleneimine can accelerate the decomposition of PA56, reduce the existence of melt macromolecules, thereby effectively preventing the generation of melt dripping of PA56 in the combustion process. The hyperbranched modified ammonium polyphosphate is loaded on the PA56 fabric to form a cross-linked network structure, which can form a carbonized layer on the surface of the fabric to protect the fabric during combustion. Melamine decomposes at high temperature to release non-combustible gas, reduces the temperature and delays combustion, and reduces the heat release rate.

[0043] Different from the prior art, the hyperbranched modified ammonium polyphosphate is loaded on the PA56 fabric to form a crosslinked network structure; the polyethyleneimine is loaded on the PA56 fabric; the ammonium polyphosphate is connected with the polyethyleneimine through graft modification; the melamine is connected with the ammonium polyphosphate through weak bonds such as electrostatic interaction, hydrogen bond and P-N bond, and is wrapped on the outer layer of the fabric, so that the durable flame-retardant effect of the modified PA56 fabric is realized. Since a large number of amine groups in the polyethyleneimine are hydroxylated and form a crosslinked network structure with the PA56 fiber through hydrogen bonds and other forces, the cohesive strength of the PA56 fabric fiber is also improved, and the strength of the modified PA fabric is further improved.

[0044] Further, in the S1 step, the mass ratio of the hyperbranched polyethyleneimine ethanol to the ammonium polyphosphate is 30-40:100-120.

[0045] Further, in the S1 step, 30-40 g / L of the hyperbranched polyethyleneimine ethanol solution is added to 100-120 g / L of the ammonium polyphosphate, and the hyperbranched polyethyleneimine and the ammonium polyphosphate are stirred at 20-50℃ for 60-80 min to perform grafting, to obtain a first mixed solution; the first mixed solution is heated to 70-80℃ to evaporate the ethanol solvent, to obtain a white solid; and the white solid is dried at 50-60℃, to obtain the hyperbranched modified ammonium polyphosphate.

[0046] Further, in the S2 step, the mass percentage concentration of the polyelectrolyte solution is 5-15 wt%.

[0047] Further, in the S3 step, the first padding time is 30-120 s, the drying temperature is 60-70℃, and the drying time is 20-30 min.

[0048] Further, in the S4 step, the preparation method of the melamine solution is as follows: the melamine is dissolved in 0.5-2 wt% of acetic acid solution to obtain the melamine solution; and the mass percentage concentration of the melamine solution is 1-4 wt%.

[0049] Further, in the S4 step, the second padding time is 30-60 s, and the padding temperature is 40-60℃.

[0050] Further, in the S5 step, the pH of the acetate buffer solution is 3-6.

[0051] Further, in the S5 step, the third padding time is 5-8 min; the drying temperature is 70-80℃, and the drying time is 20-30 min.

[0052] The second aspect of the present application provides a modified PA56 fabric with long-lasting flame retardant effect, which is prepared by the preparation method of the first aspect of the present application.

[0053] Example 1

[0054] 1. Preparation of hyperbranched modified ammonium polyphosphate: 10 g of hyperbranched polyethyleneimine and 300 g of anhydrous ethanol were added to a 500 mL beaker, and after stirring at 20 ℃ for 10 min to obtain a clear and uniform solution, 42 g of ammonium polyphosphate was added and stirred for 90 min to complete the graft modification. Then the reaction solution was heated to 60 ℃ to evaporate the ethanol solvent, and the hyperbranched modified ammonium polyphosphate white solid was obtained. Finally, the obtained white solid was dried in a 60 ℃ oven, and after grinding and crushing, the hyperbranched modified ammonium polyphosphate powder was obtained.

[0055] 2. Preparation of hyperbranched modified ammonium polyphosphate solution (10 wt%):

[0056] 10 g of modified ammonium polyphosphate was added to 90 g of deionized water to prepare a polyelectrolyte solution.

[0057] 3. Preparation of melamine solution (2 wt%):

[0058] 1 g of acetic acid was added to 97 g of deionized water to obtain an acetic acid solution. Then 2 g of melamine was added to the acetic acid solution and stirred at 50 ℃ for 30 min to obtain a melamine solution.

[0059] 4. Preparation of acetate buffer solution:

[0060] 2.5 g of acetic acid and 1.5 g of sodium acetate were added to 94.6 g of deionized water, and the pH of the solution was adjusted to 3 by adding sodium hydroxide solution / dilute sulfuric acid solution. Then 1.2 g of sodium sulfate was added to the acetate solution to obtain an acetate buffer solution.

[0061] 5. Fabric modification:

[0062] The PA56 fabric was immersed and rolled in the polyelectrolyte solution, the immersion time was 30 s, and the polyelectrolyte-PA56 treated fabric was obtained by drying at 60 ℃ for 20 min. The polyelectrolyte-PA56 treated fabric was immersed and rolled in the melamine solution, the immersion time was 30 s, and the melamine-polyelectrolyte-nylon treated fabric was obtained. The melamine-polyelectrolyte-nylon treated fabric was immersed and rolled in the acetate buffer solution, the immersion time was 5 min, and after removing the excess solution, the durable flame-retardant nylon was obtained by drying at 70 ℃ for 20 min.

[0063] The modified PA56 fabric prepared in Example 1 was compared with the raw material PA56 fabric in terms of performance, and the comparison results are shown in Table 1.

[0064] According to GB / T 5454-1997 standard, the limiting oxygen index of finished fabrics and fabrics after 20 washes was determined using a limiting oxygen index analyzer.

[0065] Vertical flame tests were conducted using a vertical burner according to GB / T 5455-2014 standard. The results of the vertical flame tests on the finished fabric and the fabric after 20 washes were obtained.

[0066] According to GB / T 3923.1-2013 standard, the breaking strength of the finished fabric and the fabric after 20 washes was evaluated using an electronic tensile tester.

[0067] Table 1 Comparison Results Chart

[0068]

[0069] Examples 2-5

[0070] The only difference between Examples 2-5 and Example 1 is that all other conditions remain unchanged, except for the amount of hyperbranched modified ammonium polyphosphate. The mass percentage of the hyperbranched modified ammonium polyphosphate solution is 0 wt%, 2 wt%, 5 wt%, and 15 wt%. After subsequent processes, the tensile breaking strength, limiting oxygen index, and tensile breaking strength and limiting oxygen index of the treated nylon fabrics are tested respectively.

[0071] The results are as follows Figure 2 As shown, with the increase of hyperbranched modified ammonium polyphosphate concentration, the mechanical strength of the modified PA56 fabric shows a trend of first increasing and then slowly decreasing, while the limiting oxygen index of the finished fabric shows a trend of first steadily increasing and then leveling off. Therefore, from the perspective of optimal overall effect and most economy, 10wt% is the preferred amount of hyperbranched modified ammonium polyphosphate solution.

[0072] Examples 6-9

[0073] The only difference between Examples 6-9 and Example 1 is that all other conditions remain unchanged, only the amount of melamine is changed, with the mass percentage of the melamine solution being 0 wt%, 1 wt%, 5 wt%, and 10 wt%. After subsequent processes are completed, the tensile breaking strength, limiting oxygen index, tensile breaking strength after 20 washes, and limiting oxygen index of the finished nylon fabric are tested respectively.

[0074] The results are as follows Figure 3 As shown, with the increase of melamine solution concentration, the mechanical strength and limiting oxygen index of modified PA56 fabric both show a trend of first increasing and then slowly decreasing. Therefore, from the perspective of optimal overall effect and most economy, 2wt% is the preferred amount of melamine solution.

[0075] Comparative Examples 1-5

[0076] Comparative Examples 1-5 and Examples 1-5 differ only in that the remaining conditions remain unchanged, the hyperbranched polyphosphoric acid solution is replaced by a polyphosphoric acid solution, and the mass percentage of the polyphosphoric acid solution is 0wt%, 2wt%, 5wt%, 10wt%, and 15wt%. After the subsequent process is completed, the tensile breaking strength, limiting oxygen index, tensile breaking strength after 20 washes, and limiting oxygen index of the finished PA56 fabric are tested respectively.

[0077] The results are shown in Table 1. Figure 4 As shown in Table 1, in Comparative Examples 1-5, the breaking strength of PA56 fabric treated with polyphosphoric acid without hyperbranched modification is generally low, and the breaking strength of the finished fabric gradually decreases with the increase of the concentration of polyphosphoric acid. In addition, the difference between the limiting oxygen index before washing and after washing is large, indicating that the hyperbranched modification of polyphosphoric acid in Examples 1-5 can greatly improve the mechanical strength of the treated fabric, while maintaining the flame retardant performance of the treated fabric.

[0078] The present application uses hyperbranched polyethyleneimine to modify polyphosphoric acid to finish PA56 fabric, which solves the defect that simple compounding of hyperbranched polyethyleneimine and melamine has poor flame retardation, and the hyperbranched structure loads and fixes melamine and polyphosphoric acid on the surface of the fabric through electrostatic interaction, hydrogen bond, P-N bond, etc., improving the durability of the flame retardant effect of the finished fabric.

[0079] The rich amine groups in the structure of hyperbranched polyethyleneimine can be hydroxylated by means of hydrogen bond and other weak bonds, thereby improving the cohesive strength of the fabric fibers. This makes up for the damage to the mechanical properties of the fabric caused by polyphosphoric acid and melamine, and maintains the good mechanical properties of PA56 fabric.

[0080] Comparative Examples 6-10

[0081] Comparative Examples 6-10 and Examples 1-5 differ only in that the remaining conditions remain unchanged, the hyperbranched polyphosphoric acid solution is replaced by a hyperbranched polyethyleneimine solution, and the mass percentage of the hyperbranched polyethyleneimine solution is 0wt%, 2wt%, 5wt%, 10wt%, and 15wt%. After the subsequent process is completed, the tensile breaking strength, limiting oxygen index, tensile breaking strength after 20 washes, and limiting oxygen index of the finished PA56 fabric are tested respectively.

[0082] The results are shown in Table 2. Figure 5 As shown in Table 2, in Comparative Examples 6-10, the breaking strength of the fabric treated with hyperbranched polyethyleneimine without loading polyphosphoric acid is slightly lower, but the change before and after washing is small, and the limiting oxygen index of the treated fabric is low. This indicates that the loading of polyphosphoric acid in Examples 1-5 can significantly improve the flame retardant performance of the finished fabric.

[0083] The present application mainly grafts and treats hyperbranched polyethylene imine and ammonium polyphosphate to obtain hyperbranched modified ammonium polyphosphate, dips PA56 fabric in the hyperbranched modified ammonium polyphosphate solution, dries and solidifies, then dips in melamine flame-retardant finishing agent, and then dips in acetic acid buffer solution to adjust the overall pH environment of the fabric, dries to solidify the flame-retardant finishing agent into a film, to obtain modified PA56 flame-retardant fabric.

[0084] Ammonium polyphosphate and polyethylene imine can accelerate the decomposition of PA56, reduce the presence of molten macromolecules, thereby effectively preventing the generation of melt dripping of PA56 during combustion. The addition of melamine significantly delays the thermal decomposition time and reduces the heat release rate, thereby achieving self-extinguishing of PA56. The hyperbranched modified ammonium polyphosphate is loaded on the PA56 fabric to form a three-dimensional network structure, which can form a carbonized layer on the surface of the fabric during combustion to protect the fabric, and at the same time, melamine decomposes at high temperature to release non-combustible gas, thereby reducing the temperature and delaying combustion, and the mutual synergistic effect of the flame-retardant components achieves excellent flame-retardant effect.

[0085] The polyethylene imine with hyperbranched structure loaded on the PA56 fabric can construct a three-dimensional network framework, and at the same time, the ammonium polyphosphate is modified and loaded on the polyethylene imine three-dimensional network framework, and at the same time, the ammonium polyphosphate acts as a linker to connect melamine to the polyethylene imine framework through electrostatic interaction, hydrogen bond, P-N bond and other weak bonds, achieving durable flame-retardant effect of PA56 fabric. In addition, when the hyperbranched polyethylene imine adheres to the PA56 fiber, the abundant amine groups of the polyethylene imine form a three-dimensional crosslinked structure through hydroxylamination and the action of hydrogen bond and other forces, enhancing the action force of the modified ammonium polyphosphate with the fabric and improving the cohesive strength of the fabric fiber, achieving the effects of durable flame-retardant and improved strength. It makes up for the simple composite flame-retardant finishing of ammonium polyphosphate and melamine. Due to poor compatibility with the fabric, it damages the mechanical properties of the fabric, and maintains the excellent mechanical properties of PA56.

[0086] Finally, it should be noted that although the above embodiments have been described in the specification and drawings of the present application, the patent protection scope of the present application should not be limited. Any technical solutions obtained by replacing or modifying the equivalent structure or equivalent flow based on the essential concept of the present application, using the content described in the specification and drawings of the present application, and directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are all included in the patent protection scope of the present application.

Claims

1. A process for the preparation of a modified PA56 fabric having a long-lasting flame retardant effect, characterized in that, The method comprises the following steps: S1: grafting hyperbranched polyethyleneimine with ammonium polyphosphate to obtain hyperbranched modified ammonium polyphosphate; S2: adding the hyperbranched modified ammonium polyphosphate into deionized water to obtain a polyelectrolyte solution; S3: first padding the PA56 fabric in the polyelectrolyte solution and drying to obtain a polyelectrolyte-PA56 treated fabric; S4: second padding the polyelectrolyte-PA56 treated fabric in a melamine solution to obtain a melamine-polyelectrolyte-PA56 treated fabric; S5: third padding the melamine-polyelectrolyte-PA56 treated fabric in an acetate buffer solution, and drying to obtain the modified PA56 fabric with long-term flame-retardant effect. In the S2 step, the mass percentage concentration of the polyelectrolyte solution is 5-15 wt%.

2. The production method according to claim 1, characterized by, In the S1 step, the mass ratio of hyperbranched polyethyleneimine to ammonium polyphosphate is 30-40:100-120.

3. The preparation method according to claim 1, characterized in that, In the S1 step, 30-40 g / L of hyperbranched polyethyleneimine ethanol solution is added to 100-120 g / L of ammonium polyphosphate, and the mixture is stirred at 20-50℃ for 60-80 min to graft hyperbranched polyethyleneimine with ammonium polyphosphate, to obtain a first mixed solution; the first mixed solution is heated to 70-80℃ to evaporate the ethanol solvent, to obtain a white solid; the white solid is dried at 50-60℃, to obtain the hyperbranched modified ammonium polyphosphate.

4. The production method according to claim 1, characterized by, In the S3 step, the first padding time is 30-120 s, the drying temperature is 60-70℃, and the drying time is 20-30 min.

5. The method of claim 1, wherein, In the S4 step, the preparation method of the melamine solution is as follows: dissolving melamine in 0.5-2 wt% acetic acid solution to obtain the melamine solution; the mass percentage concentration of the melamine solution is 1-4 wt%.

6. The method of claim 1, wherein, In the S4 step, the second padding time is 30-60 s, and the padding temperature is 40-60℃.

7. The preparation method according to claim 1, characterized in that, In the S5 step, the pH of the acetate buffer solution is 3-6.

8. The method of claim 1, wherein, In the S5 step, the third padding time is 5-8 min; the drying temperature is 70-80℃, and the drying time is 20-30 min.

9. A modified PA56 fabric having a long-lasting flame retardant effect, characterized in that, The modified PA56 fabric is prepared by the preparation method of any one of claims 1-8.

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