Modified PA56 fabric with long-acting flame-retardant effect and preparation method thereof

Abstract

The invention relates to a modified PA56 fabric with a long-acting flame-retardant effect and a preparation method thereof.The preparation method comprises the steps that hyperbranched polyethyleneimine and ammonium polyphosphate are subjected to grafting treatment to obtain hyperbranched modified ammonium polyphosphate, the PA56 fabric is padded in a hyperbranched modified ammonium polyphosphate solution, dried and cured, padded in a melamine flame-retardant finishing agent, then padded in an acetic acid buffer solution and dried, and the modified PA56 fabric with the long-acting flame-retardant effect is obtained. The modified PA56 fabric with the long-acting flame retardant effect is obtained. Different from the prior art, hyperbranched modified ammonium polyphosphate is loaded on the PA56 fabric to form a cross-linked network structure; the polyethyleneimine is loaded on the PA56 fabric; ammonium polyphosphate is connected with polyethyleneimine through grafting modification; melamine is connected with ammonium polyphosphate through electrostatic interaction, hydrogen bonds, P-N bonds and other weak bonds and wraps the outer layer of the fabric, so that the durable flame-retardant effect of the modified PA56 fabric is achieved, and the strength of the modified PA fabric is improved.

Description

Technical Field

[0001] The invention relates to the field of textiles, and in particular to a modified PA56 fabric with a long-lasting flame retardant effect and a preparation method thereof. Background Art

[0002] Nylon fabrics are widely used in various fields, including clothing, industrial manufacturing and military equipment, due to their excellent mechanical properties and wear resistance. Nylon fiber, also known as polyamide (PA) fiber, has excellent thermal properties, mechanical properties, processing properties, moisture absorption and dyeing properties. Among them, bio-based nylon 56 (PA56) is obtained by polymerizing 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 development prospects.

[0003] However, like ordinary polymers, PA56 will gradually melt, break molecules, and pyrolyze as the temperature rises, releasing a large amount of heat and causing the flame to spread. In recent years, fires caused by polymer materials have caused huge economic losses and casualties, so the flame retardant modification of PA56 has become an urgent issue to be solved.

[0004] At present, the common flame retardant modification methods for polyamide products are blending flame retardant modification, copolymerization flame retardant modification and flame retardant finishing. Although the blending flame retardant finishing method of preparing flame retardant polyamide by directly mixing polyamide masterbatch with flame retardant has the advantages of low cost and easy processing, it is very easy to cause strong damage to polyamide products. Copolymerization flame retardant modification can obtain better flame retardant properties and maintain product mechanical properties by grafting reactive flame retardants onto the main chain or side chain of polyamide molecules through copolymerization, but the production cost is high and industrial application is limited. Flame retardant finishing is a modification method in which the flame retardant finishing agent is loaded onto polyamide fibers or fabrics 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 of the invention

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

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

[0007] 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;

[0008] S3: padding the PA56 fabric in the polyelectrolyte solution for the first time and drying it to obtain a polyelectrolyte-PA56 treated fabric;

[0009] S4: performing secondary padding on the polyelectrolyte-PA56 treated fabric in a melamine solution to obtain a melamine-polyelectrolyte-PA56 treated fabric;

[0010] S5: The melamine-polyelectrolyte-PA56 treated fabric is dipped three times in an acetate buffer solution, and then dried to obtain the modified PA56 fabric with a long-lasting flame retardant effect.

[0011] Different from the existing technology, hyperbranched modified ammonium polyphosphate is loaded on PA56 fabric to form a cross-linked network structure; polyethyleneimine is loaded on PA56 fabric; ammonium polyphosphate is connected to polyethyleneimine through grafting modification; melamine is connected to ammonium polyphosphate through weak bonds such as electrostatic interaction, hydrogen bonds, and PN bonds, and wrapped in the outer layer of the fabric to achieve a durable flame retardant effect of the modified PA56 fabric. At the same time, since a large number of amine groups in polyethyleneimine are hydroxylated and form a cross-linked network structure with PA56 fibers through hydrogen bonds and other forces, the cohesive strength of the PA56 fabric fibers is improved, thereby improving the strength of the modified PA fabric.

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

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

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

[0015] Furthermore, in the step S3, the time of the first padding is 30-120 seconds, the drying temperature is 60-70° C., and the drying time is 20-30 minutes.

[0016] Furthermore, in the step S4, the preparation method of the melamine solution is: dissolving melamine in a 0.5-2wt% acetic acid solution to obtain the melamine solution; the mass percentage concentration of the melamine solution is 1-4wt%.

[0017] Furthermore, in the step S4, the secondary padding time is 30-60s, and the padding temperature is 40-60°C.

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

[0019] Furthermore, in the step S5, the time for the three padding steps is 5-8 minutes; the drying temperature is 70-80° C., and the drying time is 20-30 minutes.

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

[0021] The above-mentioned records related to the invention content are only an overview of the technical solution of the present application. In order to enable ordinary technicians in the field to more clearly understand the technical solution of the present application, and then implement it according to the written contents of the specification, and to make the above-mentioned purpose and other purposes, features and advantages of the present application easier to understand, the specific implementation mode and drawings of the present application are explained below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings are only used to illustrate the principles, implementation methods, applications, characteristics and effects of the specific embodiments of the present application and other related contents, and shall not be considered as limitations of the present application.

[0023] In the drawings of the specification:

[0024] Figure 1 This is the synthetic route of hyperbranched modified ammonium polyphosphate.

[0025] Figure 2 The performance comparison chart of hyperbranched modified ammonium polyphosphate with different dosages in Examples 1-5 is shown.

[0026] Figure 3 The performance comparison chart of different amounts of melamine used in Examples 1, 6-9 is shown.

[0027] Figure 4 It is a performance comparison chart of different ammonium polyphosphate dosages for comparative examples 1-5.

[0028] Figure 5 This is a performance comparison chart of different amounts of hyperbranched polyethyleneimine used in Comparative Examples 6-10. DETAILED DESCRIPTION

[0029] In order to explain in detail the possible application scenarios, technical principles, specific schemes that can be implemented, and the purposes and effects that can be achieved, the following is a detailed description of the specific embodiments listed 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 are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0030] Reference to "embodiment" herein means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The term "embodiment" appearing in various places in the specification does not necessarily refer to the same embodiment, nor does it 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, the various technical features mentioned in the embodiments can be combined in any way to form a corresponding implementable technical solution.

[0031] Unless otherwise defined, the technical terms used in this document have the same meanings as those generally understood by those skilled in the art to which this application belongs; the use of relevant terms in this document is only for describing specific embodiments and is not intended to limit this application.

[0032] In the description of this application, the term "and / or" is an expression used to describe the logical relationship between objects, indicating that three relationships may exist, for example, A and / or B, which means: A exists, B exists, and A and B exist at the same time. In addition, the character " / " in this article generally indicates that the objects before and after are in an "or" logical relationship.

[0033] In the present application, terms such as “first” and “second” are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship of quantity, priority or sequence between these entities or operations.

[0034] Without further limitations, in this application, the words "include", "comprises", "has" or other similar expressions used in the sentences are intended to cover non-exclusive inclusion. These expressions do not exclude the presence of additional elements in the process, method or product including the elements, so that the process, method or product including a series of elements may include not only those limited elements, but also other elements not explicitly listed, or also include elements inherent to such process, method or product.

[0035] Similar to the understanding in the Examination Guidelines, in this application, expressions such as "greater than", "less than", "exceed" and the like are understood to exclude the number itself; expressions such as "above", "below", "within" and the like are understood to include the number itself. In addition, in the description of the embodiments of this application, "multiple" means more than two (including two), and similar expressions related to "multiple" are also understood in this way, such as "multiple groups", "multiple times", etc., unless otherwise clearly and specifically limited.

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

[0037] 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;

[0038] S3: padding the PA56 fabric in the polyelectrolyte solution for the first time and drying it to obtain a polyelectrolyte-PA56 treated fabric;

[0039] S4: performing secondary padding on the polyelectrolyte-PA56 treated fabric in a melamine solution to obtain a melamine-polyelectrolyte-PA56 treated fabric;

[0040] S5: The melamine-polyelectrolyte-PA56 treated fabric is dipped three times in an acetate buffer solution, and then dried to obtain the modified PA56 fabric with a long-lasting flame retardant effect.

[0041] The synthetic route of hyperbranched modified ammonium polyphosphate is as follows Figure 1 shown.

[0042] Ammonium polyphosphate and polyethyleneimine can accelerate the decomposition of PA56 and reduce the presence of molten macromolecules, thereby effectively preventing the generation of molten droplets of PA56 during combustion. Hyperbranched modified ammonium polyphosphate is loaded on PA56 fabric to form a cross-linked network structure, which can form a carbonized layer on the fabric surface to protect the fabric during combustion. Melamine decomposes at high temperatures to release non-combustible gases, which lowers the temperature and delays combustion, reducing the heat release rate.

[0043] Different from the existing technology, hyperbranched modified ammonium polyphosphate is loaded on PA56 fabric to form a cross-linked network structure; polyethyleneimine is loaded on PA56 fabric; ammonium polyphosphate is connected to polyethyleneimine through grafting modification; melamine is connected to ammonium polyphosphate through weak bonds such as electrostatic interaction, hydrogen bonds, and PN bonds, and wrapped in the outer layer of the fabric to achieve a durable flame retardant effect of the modified PA56 fabric. Since a large number of amine groups in polyethyleneimine are hydroxylated and form a cross-linked network structure with PA56 fibers through hydrogen bonds and other forces, the cohesive strength of PA56 fabric fibers is also improved, thereby improving the strength of the modified PA fabric.

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

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

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

[0047] Furthermore, in the step S3, the time of the first padding is 30-120 seconds, the drying temperature is 60-70° C., and the drying time is 20-30 minutes.

[0048] Furthermore, in the step S4, the preparation method of the melamine solution is: dissolving melamine in a 0.5-2wt% acetic acid solution to obtain the melamine solution; the mass percentage concentration of the melamine solution is 1-4wt%.

[0049] Furthermore, in the step S4, the secondary padding time is 30-60s, and the padding temperature is 40-60°C.

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

[0051] Furthermore, in the step S5, the time for the three padding steps is 5-8 minutes; the drying temperature is 70-80° C., and the drying time is 20-30 minutes.

[0052] The second aspect of the present application provides a modified PA56 fabric with a long-lasting flame retardant effect, wherein the modified PA56 fabric is prepared by the preparation method described in 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 stirred at 20 ° C for 10 min to obtain a clear and uniform solution, and then 42 g of ammonium polyphosphate was added thereto and stirred for 90 min to complete the grafting modification. After that, the reaction solution was heated to 60 ° C to evaporate and remove the ethanol solvent to obtain a hyperbranched modified ammonium polyphosphate white solid. Finally, the obtained white solid was placed in a 60 ° C oven to dry, and ground and crushed to obtain a hyperbranched modified ammonium polyphosphate powder.

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

[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 (2wt%):

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

[0059] 4. Preparation of acetate buffer:

[0060] 2.5 g of acetic acid and 1.5 g of sodium acetate were added to 94.6 g of deionized water, and after sodium hydroxide solution / dilute sulfuric acid solution was added dropwise to adjust the solution pH to 3, 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 dipped and rolled in a polyelectrolyte solution for 30 seconds, and dried at 60°C for 20 minutes to obtain a polyelectrolyte-PA56 treated fabric; the polyelectrolyte-PA56 treated fabric was dipped and rolled in a melamine solution for 30 seconds to obtain a melamine-polyelectrolyte-nylon treated fabric; the melamine-polyelectrolyte-nylon treated fabric was dipped and rolled in an acetate buffer solution for 5 minutes, and after rolling off the excess solution, it was dried at 70°C for 20 minutes to obtain a durable flame retardant nylon.

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

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

[0065] According to GB / T 5455-2014 standard, a vertical flame test was performed using a vertical burner device. The vertical burning test results of the finished fabric and the fabric after 20 washes were obtained.

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

[0067] Table 1 Comparison results

[0068]

[0069] Embodiment 2-5

[0070] The difference between Examples 2-5 and Example 1 is that: keeping other conditions unchanged, only changing the amount of hyperbranched modified ammonium polyphosphate, the mass percentage of the hyperbranched modified ammonium polyphosphate solution is 0wt%, 2wt%, 5wt%, 15wt%. After the subsequent processes are completed, the tensile breaking strength, limiting oxygen index, tensile breaking strength and limiting oxygen index of the nylon fabric after 20 washes are tested respectively.

[0071] The results are as follows Figure 2 As shown in the figure, with the increase of the concentration of hyperbranched modified ammonium polyphosphate, 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 tending to be flat. Therefore, from the perspective of the best overall effect and the most economical, 10wt% is the preferred amount of the hyperbranched modified ammonium polyphosphate solution.

[0072] Embodiment 6-9

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

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

[0075] Comparative Examples 1-5

[0076] The difference between Comparative Example 1-5 and Example 1-5 is that: keeping other conditions unchanged, the hyperbranched ammonium polyphosphate solution is replaced by an ammonium polyphosphate solution, and the mass percentage of the ammonium polyphosphate solution is 0wt%, 2wt%, 5wt%, 10wt%, and 15wt%. After the subsequent processes are completed, the tensile breaking strength, limiting oxygen index, tensile breaking strength and limiting oxygen index of the nylon fabric after 20 washes are tested respectively.

[0077] The results are as follows Figure 4 As shown in the figure, in Comparative Examples 1-5, the breaking strength of the PA56 fabric treated with ammonium polyphosphate without hyperbranching modification is relatively low overall, and the breaking strength of the finished fabric gradually decreases with the increase of the concentration of ammonium polyphosphate. In addition, the difference between the limiting oxygen index before and after washing is large, indicating that the hyperbranching modification of ammonium polyphosphate in Examples 1-5 can greatly improve the mechanical strength of the treated fabric while maintaining the flame retardant properties of the treated fabric.

[0078] The present application utilizes hyperbranched polyethyleneimine to modify ammonium polyphosphate to finish PA56 fabric, thereby overcoming the defect that the simple compound of hyperbranched polyethyleneimine and melamine has poor flame retardancy. At the same time, the hyperbranched structure loads and fixes melamine and ammonium polyphosphate on the fabric surface through electrostatic interaction, hydrogen bonds, PN bonds, etc., thereby improving the durability of the flame retardant effect of the finished fabric.

[0079] The rich amine groups in the structure of hyperbranched polyethyleneimine can improve the cohesive strength of fabric fibers through hydroxylation and weak bonds such as hydrogen bonds, making up for the damage of ammonium polyphosphate and melamine to the mechanical properties of fabrics and maintaining the good mechanical properties of PA56 fabrics.

[0080] Comparative Examples 6-10

[0081] The difference between Comparative Examples 6-10 and Examples 1-5 is that: keeping other conditions unchanged, the hyperbranched polyethyleneimine solution is used to replace the hyperbranched ammonium polyphosphate solution, and the mass percentage of the hyperbranched polyethyleneimine solution is 0wt%, 2wt%, 5wt%, 10wt%, and 15wt%. After the subsequent processes are completed, the tensile breaking strength, limiting oxygen index, tensile breaking strength and limiting oxygen index of the PA56 fabric after finishing are tested respectively.

[0082] The results are as follows Figure 5 As shown, in Comparative Examples 6-10, the breaking strength of the fabric treated with hyperbranched polyethyleneimine without ammonium polyphosphate loading is slightly lower overall, but the change before and after washing is small, and the limiting oxygen index of the treated fabric is lower. This shows that the loading of ammonium polyphosphate in Examples 1-5 can significantly improve the flame retardant properties of the finished fabric.

[0083] The invention mainly comprises the following steps: performing mixed grafting treatment on hyperbranched polyethyleneimine and ammonium polyphosphate to obtain hyperbranched modified ammonium polyphosphate, dipping PA56 fabric into the hyperbranched modified ammonium polyphosphate solution, drying and curing the mixture, dipping the mixture into a melamine flame retardant finishing agent, dipping the fabric into an acetic acid buffer solution to adjust the overall pH environment of the fabric, drying and curing the flame retardant finishing agent into a film, and obtaining the modified PA56 flame retardant fabric.

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

[0085] The hyperbranched polyethyleneimine loaded on the PA56 fabric can build a three-dimensional network framework. At the same time, ammonium polyphosphate is loaded on the three-dimensional network framework of polyethyleneimine through modification. At the same time, ammonium polyphosphate acts as a connector to connect melamine to the polyethyleneimine framework through weak bonds such as electrostatic interaction, hydrogen bonds, and PN bonds, thereby achieving a durable flame retardant effect on the PA56 fabric. In addition, when the hyperbranched polyethyleneimine is attached to the PA56 fiber, the rich amino groups of the polyethyleneimine are hydroxylated and form a three-dimensional cross-linked structure with the help of hydrogen bonds and other forces, which enhances the interaction between the modified ammonium polyphosphate and the fabric while improving the cohesive strength of the fabric fiber, achieving a durable flame retardant and strength-enhancing effect. This makes up for the simple composite flame retardant finishing of ammonium polyphosphate and melamine. The damage to the mechanical properties of the fabric due to poor compatibility with the fabric 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 this application, this does not limit the scope of patent protection of this application. All technical solutions generated by replacing or modifying equivalent structures or equivalent processes based on the essential concept of this application using the contents recorded in the specification and drawings of this application, as well as directly or indirectly implementing the technical solutions of the above embodiments in other related technical fields, are included in the scope of patent protection of this application.

Claims

1. A method for preparing a modified PA56 fabric with a long-lasting flame retardant effect, characterized in that: The following steps are involved: 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: padding the PA56 fabric in the polyelectrolyte solution for the first time and drying it to obtain a polyelectrolyte-PA56 treated fabric; S4: performing secondary padding on the polyelectrolyte-PA56 treated fabric in a melamine solution to obtain a melamine-polyelectrolyte-PA56 treated fabric; S5: The melamine-polyelectrolyte-PA56 treated fabric is dipped three times in an acetate buffer solution, and then dried to obtain the modified PA56 fabric with a long-lasting flame retardant effect.

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

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

4. The preparation method according to claim 1, characterized in that: In the step S2, the mass percentage concentration of the polyelectrolyte solution is 5-15wt%.

5. The preparation method according to claim 1, characterized in that: In the step S3, the time of the first padding is 30-120 seconds, the drying temperature is 60-70° C., and the drying time is 20-30 minutes.

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

7. The preparation method according to claim 1, characterized in that: In the step S4, the secondary padding time is 30-60s, and the padding temperature is 40-60°C.

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

9. The preparation method according to claim 1, characterized in that: In the step S5, the time for the three padding steps is 5-8 minutes; the drying temperature is 70-80° C., and the drying time is 20-30 minutes.

10. A modified PA56 fabric with long-lasting flame retardant effect, characterized in that: The modified PA56 fabric is prepared by the preparation method according to any one of claims 1 to 9.

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