Flame-retardant polyamide fabric and method for producing the same

Abstract

The application discloses a kind of flame-retardant polyamide fabrics and preparation method thereof, comprising the following steps: DOPO and 1,3-dihydroxy acetone are mixed, heated melt is reacted, after reaction, purification and drying, obtain binary DOPO derivative flame retardant;Binary DOPO derivative flame retardant is dissolved in the mixed solvent of ethanol and water, to obtain flame retardant solution;The pH of flame retardant solution is adjusted, then the polyamide fabric is treated using two-dip two-pad method, and baking is obtained to obtain flame-retardant polyamide fabric.The raw material used in the application is safe and environmentally friendly, the preparation method is simple, the flame-retardant polyamide fabric prepared has excellent flame-retardant performance and wash resistance, and there is no pollution during use.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of flame retardants, and particularly relates to a flame-retardant polyamide fabric and a preparation method thereof. BACKGROUND

[0002] With the continuous development of social economy, the types of textiles are gradually increasing. The potential fire hazard caused by some textiles without flame-retardant properties is also increasing. How to solve the shortcomings of textile flammability and melt dripping, reduce the risk of textile combustion, and reduce the generation of toxic gases during textile combustion to protect personal and property safety has become an important research topic in the field of textile production at the present stage. The current flame retardation of textiles is mainly through two ways of flame-retardant treatment of fibers and flame-retardant finishing of fabrics: the former is to add flame retardants to flammable raw silk such as polyester, cotton, and acrylic, to achieve flame retardation by inhibiting free radicals in the combustion process, changing the thermal decomposition process of the fiber, promoting dehydration and carbonization, releasing non-combustible gases on the surface of the fiber to isolate air, etc.; the latter is mainly through spraying, padding, soaking, coating, etc. in the finishing process of textiles to obtain flame-retardant properties. Compared with the former, the latter has the advantages of simple operation and mass production, and is more suitable for enterprise processing and production.

[0003] The key to flame retardation is flame retardant, which is an additive that can prevent textiles from igniting or inhibit the spread of flames. It plays a flame-retardant role through mechanisms such as heat absorption, covering, chain inhibition, and suffocation of non-combustible gases. According to the different flame-retardant elements contained, flame retardants can be divided into halogen-based, phosphorus-based, nitrogen-based, phosphorus-halogen-based, and phosphorus-nitrogen-based. In the past, they have been widely used to improve their flame retardancy. Halogenated flame retardants were widely used in polymers due to their high efficiency and low price, effectively improving the flame retardant properties. However, they produce toxic and corrosive smoke during combustion, pollute the environment, and pose problems to human health, and have been banned in many fields. To solve the problems of halogenated flame retardants, the development of phosphorus-based flame retardants can evaporate into the gas phase to form PO2, PO, and other phosphorus radicals, which can capture free radicals for combustion, thereby reducing or even stopping the combustion reaction. On the other hand, it can catalyze the carbonization of polymers to form a foamed carbon layer under fire hazards, limiting the transmission of oxygen and heat, and ultimately improving the flame-retardant properties in a synergistic manner. In addition, nitrogen-based flame retardants do not contain halogens and have no corrosive effect, good electrical properties, and good flame-retardant effect, with obvious advantages in electronic products. However, most phosphorus-based flame retardants come from petroleum-based resources, and their preparation is complicated and requires the consumption of large amounts of organic solvents, resulting in high production costs and potential environmental problems. In addition, phosphorus-based flame retardants may release toxic gases such as formaldehyde and phosphine during combustion, and also exacerbate the release of smoke, limiting their practical application in industry. Therefore, it is necessary to develop cleaner and more environmentally friendly phosphorus-based flame retardants to solve the above problems.

[0004] DOPO is an environmentally friendly phosphorus-containing flame retardant that has been proven harmless to humans and the environment. However, due to its low thermal stability and low flame retardant efficiency, DOPO is rarely used directly for flame retardant finishing of materials. There are two main methods to improve the flame retardant efficiency of DOPO: (1) Increase the phosphorus content. Phosphorus is the main flame retardant element, and increasing its content can significantly improve the flame retardant efficiency. (2) Introduce other flame retardant elements, such as nitrogen, silicon, and sulfur, and improve their flame retardant efficiency through synergistic effects. Currently, most studies use synergistic methods to improve its flame retardant efficiency, while there are few studies on increasing the phosphorus content alone and exploring its flame retardant efficiency.

[0005] Chinese patent CN116479541A proposes a polyamide 6 composite fiber with flame retardant and antibacterial properties, which is made of copper-zinc bimetallic organic framework material (Cu-Zn-ZIF) and matrix (nylon 6). This patent mainly prepares polyamide 6 composite fibers with flame retardant and antibacterial properties through a blending method, and the preparation process is complex and cumbersome.

[0006] Reference 1 (Polymer Degradation and Stability 166(2019)344-352.) describes the preparation of a binary DOPO derivative via the pH reaction of DOPO with the -CHO and C=C reactions of acrolein, and the subsequent preparation of a flame-retardant epoxy resin using an additive method. However, acrolein is a Group 3 carcinogen, and the reaction process involves a large amount of tetrahydrofuran, indicating that this technology and method pose certain risks to human health and the environment.

[0007] Reference 2 (Industrial & Engineering Chemistry Research 56 (2017) 5913-5924) prepared a binary DOPO derivative by reacting the PH bond of DOPO with the two -CHO of terephthalaldehyde. However, the reaction temperature was low and a large amount of toluene was used as a solvent, which does not meet the requirements of enterprise production and environmental protection.

[0008] Reference 3 (European Polymer Journal 178(2022)111488) synthesized a binary DOPO derivative by reacting the PH bond of DOPO with the two C=C bonds of magnolol. However, the reaction temperature was high and lasted for 54 hours, which is a long reaction time.

[0009] Reference 4 (Progress in Organic Coatings 72 (2011) 402-409) reports a method for preparing binary derivatives by reacting a pH bond with the ketone group of 4,4′-diaminobenzophenone in a molar ratio of 2:1. However, this method requires high temperature and a large amount of organic solvent, and it also introduces other flame retardant elements. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flame-retardant polyamide fabric and its preparation method. The raw materials used are safe and environmentally friendly, the preparation method is simple, and the prepared flame-retardant polyamide fabric has excellent flame-retardant and water-washing resistance properties, and the use process is pollution-free.

[0011] This invention provides the following technical solution:

[0012] In a first aspect, a method for preparing flame-retardant polyamide fabric is provided, comprising the following steps:

[0013] DOPO and 1,3-dihydroxyacetone were mixed, heated to melt and react. After the reaction was completed, the mixture was purified and dried to obtain a binary DOPO derivative flame retardant.

[0014] The binary DOPO derivative flame retardant was dissolved in a mixed solvent of ethanol and water to obtain a flame retardant solution.

[0015] The pH of the flame retardant solution was adjusted, and then the polyamide fabric was treated with a two-dip and two-nip method and baked to obtain the flame-retardant polyamide fabric.

[0016] Furthermore, the molar ratio of DOPO to 1,3-dihydroxyacetone is 2:1.

[0017] Furthermore, the temperature of the heating and melting reaction is 170–200°C, and the reaction time is 5–8 hours.

[0018] Furthermore, the concentration of the binary DOPO derivative flame retardant in the flame retardant solution is 5–10 g / L.

[0019] Furthermore, the volume ratio of ethanol to water in the mixed solvent of ethanol and water is 1:(1-2).

[0020] Furthermore, the specific method for adjusting the pH of the flame retardant solution is as follows: adjust the pH to 3-5 using acetic acid.

[0021] Furthermore, the specific method of the two-dip and two-roll method includes: immersing the polyamide fabric in a flame retardant solution after adjusting the pH for 10-20 minutes, and rolling it once with a rolling mill; returning it to the flame retardant solution after adjusting the pH and continuing to immerse it for 10-20 minutes, and then rolling it once more with a rolling mill.

[0022] Furthermore, the baking temperature is 160–180°C, and the baking time is 20–30 minutes.

[0023] Furthermore, the polyamide fabric includes one of polyamide 6 fabric, polyamide 66 fabric, and polyamide 56 fabric.

[0024] In a second aspect, a flame-retardant polyamide fabric is provided, which is prepared by the method described in the first aspect.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] (1) The present invention uses DOPO and 1,3-dihydroxyacetone as raw materials to prepare a binary DOPO derivative flame retardant through a nucleophilic substitution reaction. The flame retardant has a high phosphorus content and produces phosphorus-containing fragments such as PO·, PO2· and HPO2 during combustion. These fragments are released into the combustion zone to further capture the free radicals required for combustion and inhibit the chain reaction, thereby obtaining the flame retardant effect.

[0027] (2) In this invention, the polyamide fabric is placed in a flame retardant solution after pH adjustment, and the polyamide fabric is treated by a two-dip and two-nip method, and then baked, so that the hydroxyl groups of the binary DOPO derivative can covalently bond with the carboxyl groups of the polyamide, thereby further improving the flame retardant properties and water-washing resistance of the polyamide fabric.

[0028] (3) The flame retardant properties of the flame retardant polyamide fabric prepared by the present invention are: damaged length 12.0-13.5cm, limiting oxygen index 28.5-29.7%, no molten dripping during the burning process, and no molten dripping during the burning process after 20-25 water washings;

[0029] (4) The DOPO used in this invention is an environmentally friendly reagent, and 1,3-dihydroxyacetone is a natural product. Therefore, the prepared flame retardant is an environmentally friendly flame retardant and will not cause pollution during use. Attached Figure Description

[0030] Figure 1 This is a synthetic route diagram of the binary DOPO derivative in Example 1 of the present invention;

[0031] Figure 2 The binary DOPO derivative in Example 1 of this invention 31 C NMR spectrum;

[0032] Figure 3 The binary DOPO derivative in Example 1 of this invention 1 H NMR spectrum;

[0033] Figure 4 The binary DOPO derivative in Example 2 of this invention31 P NMR spectrum;

[0034] Figure 5 This is a graph showing the flame retardant performance test results of the original polyamide 6 fabric in Example 3 of the present invention;

[0035] Figure 6 The image shows the test results of the flame retardant performance of the polyamide 6 fabric treated with flame retardant solution in Example 3 of the present invention. Detailed Implementation

[0036] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0037] The test methods for the performance indicators involved in the following embodiments and comparative examples are as follows:

[0038] (1) Damage length: The damage length of polyamide fabrics was tested using ASTM D6413-15;

[0039] (2) Anti-dripping performance: The dripping performance of polyamide fabrics was tested using ASTM D6413-15;

[0040] (3) Limiting oxygen index: The limiting oxygen index of polyamide fabrics was tested using ASTM D2863-17.

[0041] (4) Washing resistance: The polyamide fabric was washed according to the AATCC 61-2013 washing standard.

[0042] (5) Phosphorus content: measured using an ICAP 6300DUO inductively coupled plasma optical emission spectrometer.

[0043] Example 1

[0044] This embodiment provides a method for preparing flame-retardant polyamide fabric, the specific steps of which are as follows:

[0045] (1) Place 0.1 mol DOPO (21.6 g) and 0.05 mol 1,3-dihydroxyacetone (4.5 g) in a three-necked flask, heat to 170 °C under nitrogen protection to melt it, and continue to stir the reaction at 170 °C for 5 h. After the reaction is completed, recrystallize the reaction product with ethanol to obtain a binary DOPO derivative flame retardant.

[0046] (2) Dissolve the binary DOPO derivative flame retardant in a mixed solvent of ethanol and water (volume ratio of ethanol to water is 1:2), adjust the pH with acetic acid, and prepare a flame retardant solution with a concentration of 5 g / L and a pH value of 4.

[0047] (3) Flame-retardant polyamide 66 fabric was prepared by a two-dip two-roll method. The polyamide 66 fabric was immersed in the flame retardant solution obtained in step (2) for 15 min, rolled once with a rolling mill, returned to the original solution and continued to be immersed for 15 min, and rolled once more. After the reaction was completed, it was taken out and baked at 160℃ for 20 min to finally obtain the flame-retardant polyamide 66 fabric.

[0048] Figure 1 The diagram shows the synthetic route of the binary DOPO derivative in step (1).

[0049] Figure 2 The carbon spectrum of the binary DOPO derivative in step (1) shows a vibrational peak at 192.0 ppm for the ketone group of 1,3-dihydroxyacetone, but this vibrational peak does not appear in the image. Figure 2 The results show that the ketone group has been completely reacted. Figure 3 The 1H NMR spectrum of the binary DOPO derivative in step (1) shows a vibrational peak at 8.9 ppm for the DOPO pH bond, but this peak did not appear, indicating that the DOPO pH bond reacted completely. In summary, the ketone group and the pH bond reacted completely in a molar ratio of 1:2.

[0050] The flame-retardant polyamide 66 prepared in this embodiment exhibits the following flame-retardant properties: damaged length 13.5 cm, limiting oxygen index 28.5%, no molten dripping during combustion, and no molten dripping even after 20 washes. The measured phosphorus content of the flame-retardant polyamide 66 fabric is 1.63 mg / g.

[0051] Example 2

[0052] This embodiment provides a method for preparing flame-retardant polyamide fabric, the specific steps of which are as follows:

[0053] (1) Place 0.2 mol DOPO (43.2 g) and 0.1 mol 1,3-dihydroxyacetone (9.0 g) in a three-necked flask, heat to 180 °C under nitrogen protection to melt it, and continue to stir the reaction at 180 °C for 6 h. After the reaction is completed, recrystallize the reaction product with ethanol to obtain a binary DOPO derivative flame retardant.

[0054] (2) The binary DOPO derivative flame retardant was dissolved in a mixed solvent of ethanol and water (volume ratio of ethanol to water is 1:1), and the pH was adjusted with acetic acid to prepare a flame retardant solution with a concentration of 6 g / L and a pH value of 5.

[0055] (3) Flame-retardant polyamide 56 fabric was prepared by a two-dip and two-roll method. The polyamide 56 fabric was immersed in the flame retardant solution obtained in step (2) for 10 min, rolled once with a rolling mill, returned to the original solution and immersed for another 10 min, and rolled once more. After the reaction was completed, it was taken out and baked at 170℃ for 25 min to finally obtain the flame-retardant polyamide 56 fabric.

[0056] Figure 4 This is the phosphorus spectrum of the binary DOPO derivative in this embodiment. Figure 4 The presence of a vibrational peak indicates that phosphorus exists in only one chemical environment, and this peak position is completely different from that of phosphorus in DOPO. This result strongly confirms the successful preparation of the binary DOPO derivative.

[0057] The flame-retardant properties of the prepared flame-retardant polyamide 66 are as follows: damaged length 12.0 cm, limiting oxygen index 28.9%, no molten dripping during combustion, and no molten dripping after 20 washes. The phosphorus content of the flame-retardant polyamide 56 fabric was measured to be 1.81 mg / g.

[0058] Example 3

[0059] This embodiment provides a method for preparing flame-retardant polyamide fabric, the specific steps of which are as follows:

[0060] (1) Place 0.05 mol DOPO (10.8 g) and 0.025 mol 1,3-dihydroxyacetone (2.3 g) in a three-necked flask, heat to 190 °C under nitrogen protection to melt it, and continue to stir the reaction at 190 °C for 7 h. After the reaction is completed, recrystallize the reaction product with ethanol to obtain a binary DOPO derivative flame retardant.

[0061] (2) The binary DOPO derivative flame retardant was dissolved in a mixed solvent of ethanol and water (volume ratio of ethanol and water is 1:1), and the pH was adjusted with acetic acid to prepare a flame retardant solution with a concentration of 10 g / L and a pH value of 3.

[0062] (3) Flame-retardant polyamide 6 fabric was prepared by two dips and two tumblers. The polyamide 6 fabric was immersed in the flame retardant solution obtained in step (2) for 20 min, tumbled once with a tumbler, returned to the original solution and continued to be immersed for 20 min, and then tumbled once more. After the reaction was completed, it was taken out and baked at 180°C for 30 min to finally obtain flame-retardant polyamide 6 fabric.

[0063] Figure 5 and Figure 6The figures show vertical burning diagrams of the original polyamide 6 fabric (untreated with flame retardant solution) and the polyamide 6 fabric treated with flame retardant solution, respectively. As can be seen from the figures, the original polyamide 6 fabric is highly flammable, with a damaged length of 16.3 cm. In contrast, the damaged length of the polyamide 6 fabric treated with flame retardant solution in this embodiment is significantly reduced, demonstrating a better flame retardant effect.

[0064] The flame-retardant properties of the prepared flame-retardant polyamide 6 are as follows: damaged length 12cm, limiting oxygen index 29.7%, no molten dripping during combustion, and no molten dripping after 25 washes. The phosphorus content of the flame-retardant polyamide 6 fabric was measured to be 2.32 mg / g.

[0065] Example 4

[0066] This embodiment provides a method for preparing flame-retardant polyamide fabric, the specific steps of which are as follows:

[0067] (1) Place 0.2 mol DOPO (43.2 g) and 0.1 mol 1,3-dihydroxyacetone (9.0 g) in a three-necked flask, heat to 200 °C under nitrogen protection to melt it, and continue to stir the reaction at 200 °C for 8 h. After the reaction is completed, recrystallize the reaction product with ethanol to obtain a binary DOPO derivative flame retardant.

[0068] (2) The binary DOPO derivative flame retardant was dissolved in a mixed solvent of ethanol and water (volume ratio of ethanol to water is 1:1), and the pH was adjusted with acetic acid to prepare a flame retardant solution with a concentration of 8 g / L and a pH value of 4.5.

[0069] (3) Flame-retardant polyamide 66 fabric was prepared by two dips and two treads method. The polyamide 66 fabric was immersed in the flame retardant solution obtained in step (2) for 10 min, treaded once with a treadmill, returned to the original solution and continued to be immersed for 10 min, and then treaded once more. After the reaction was completed, it was taken out and baked at 175°C for 25 min to finally obtain flame-retardant polyamide 66 fabric.

[0070] The flame-retardant polyamide 66 obtained exhibits the following flame-retardant properties: a damaged length of 12.3 cm, a limiting oxygen index of 29.4%, and no molten dripping during combustion. Even after 25 washes, no molten dripping occurred during combustion. The measured phosphorus content of the flame-retardant polyamide 66 fabric is 2.04 mg / g.

[0071] Comparative Example 1

[0072] A method for preparing DOPO flame-retardant polyamide fabric, the specific steps of which are as follows:

[0073] (1) Prepare a 5g / L DOPO finishing solution with an ethanol to water volume ratio of 1:5 and adjust its pH to 4 to obtain a flame retardant solution.

[0074] (2) Flame-retardant polyamide 66 fabric was prepared by two dips and two tumblers. The polyamide 66 fabric was immersed in the flame retardant solution obtained in step (2) for 10 min, tumbled once with a tumbler, returned to the original solution and continued to be immersed for 15 min, and then tumbled once more. After the reaction was completed, it was taken out and baked at 160°C for 20 min to finally obtain flame-retardant polyamide 66 fabric.

[0075] The final flame-retardant polyamide 6 fabric had an LOI of 27.1%, a damaged length of 14.8 cm, and a melt droplet count of 0; after 20 washes, the melt droplet count was 1. The phosphorus content on the flame-retardant polyamide 66 fabric was measured to be 0.78 mg / g, which is significantly lower than the phosphorus content on the flame-retardant polyamide fabrics in Examples 1-4. Therefore, its flame-retardant properties and washability are not as good as those in Examples 1-4.

[0076] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of a flame-retardant polyamide fabric, characterized in that, The method comprises the following steps: DOPO and 1,3-dihydroxyacetone are mixed in a molar ratio of 2:1, heated and melted to react, the reaction temperature is 170-200 DEG C, the reaction time is 5-8h, after the reaction, purification and drying are carried out, and a binary DOPO derivative flame retardant is obtained; The binary DOPO derivative flame retardant is dissolved in a mixed solvent of ethanol and water to obtain a flame retardant solution; The pH of the flame retardant solution is adjusted, then a polyamide fabric is treated by a double-dip double-nip method, and baking is carried out to obtain a flame-retardant polyamide fabric.

2. The process for the preparation of flame retardant polyamide fabric according to claim 1, characterized in that, The concentration of the binary DOPO derivative flame retardant in the flame retardant solution is 5-10g / L.

3. The method of producing a flame retardant polyamide fabric according to claim 1, characterized by, The volume ratio of ethanol to water in the mixed solvent of ethanol and water is 1:(1-2).

4. The method of producing a flame retardant polyamide fabric according to claim 1, characterized by, The specific method for adjusting the pH of the flame retardant solution is that the pH is adjusted to 3-5 by using acetic acid.

5. The method of producing a flame retardant polyamide fabric according to claim 1, characterized by, The specific method of the double-dip double-nip method comprises the following steps: the polyamide fabric is dipped in the flame retardant solution with adjusted pH for 10-20min, and is nipped once by a nip roller; the polyamide fabric is returned to the flame retardant solution with adjusted pH and dipped again for 10-20min, and is nipped once by a nip roller.

6. The method of producing a flame retardant polyamide fabric according to claim 1, characterized by, The baking temperature is 160-180 DEG C, and the baking time is 20-30min.

7. The method of producing a flame retardant polyamide fabric according to claim 1, characterized by, The polyamide fabric comprises one of a polyamide 6 fabric, a polyamide 66 fabric and a polyamide 56 fabric.

8. A flame-retardant polyamide fabric, characterized in that, The method is prepared by any one of claims 1-7.

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