A method for preparing phosphorus-nitrogen synergistic flame-retardant polyester-cotton fabric

Abstract

The present application relates to a method for preparing phosphorus-nitrogen synergistic flame-retardant polyester-cotton fabric, and belongs to the field of flame-retardant fabric research. The method realizes the synergistic effect between two kinds of flame retardants by designing and synthesizing phosphorus-based flame retardants and using them in combination with nitrogen-containing flame retardants. First, a phosphorus-containing flame retardant is prepared through a specific synthesis procedure. Then, the phosphorus-containing flame retardant is prepared into a solution with a nitrogen-containing flame retardant. Next, the polyester-cotton fabric is sequentially immersed in a polydopamine-polyethyleneimine co-deposition solution and a phosphorus-containing flame retardant solution, so that they are fully combined with each other, and a phosphorus-nitrogen synergistic flame-retardant polyester-cotton fabric with excellent flame-retardant performance is prepared. The thermal degradation and carbonization process of cotton fibers are promoted, a carbon layer that insulates heat is formed, the synergistic effect between the phosphorus-based and nitrogen-based flame retardants delays the melting and dripping of polyester fibers, and the flame-retardant effect of the fabric is improved. This preparation method is simple and easy to implement, and can provide an effective and efficient solution for the flame-retardant treatment of polyester-cotton fabric.

Description

Technical Field

[0001] This invention relates to a method for preparing phosphorus and nitrogen synergistic flame-retardant polyester-cotton fabrics, belonging to the field of flame-retardant fabric research. Background Technology

[0002] Polyester-cotton fabrics possess good durability, withstanding daily wear and tear and washing without easily becoming worn or deformed. They also exhibit high colorfastness, meaning good colorfastness and resistance to fading. Furthermore, they have good wrinkle resistance, are not prone to wrinkling, and are easy to iron. They absorb sweat and moisture, keeping skin relatively dry and offering some quick-drying properties. Combining the advantages of both cotton and polyester fabrics, polyester-cotton fabrics have been widely used in clothing, home furnishings, and interior decoration. However, a unique "wick effect" phenomenon occurs during the combustion of polyester-cotton fabrics. Specifically, cotton fibers decompose at lower temperatures, providing the initial source of fuel; as the temperature rises, molten polyester fibers adhere to the charred cotton fiber skeleton, further providing more energy and fuel for the combustion process, making the combustion more intense. This phenomenon can increase the risk of fire. Therefore, effective flame-retardant treatment of polyester-cotton fabrics is crucial, but it also presents considerable challenges.

[0003] Polydopamine (PDA) is a simple and versatile functional material that can be deposited on various substrate surfaces due to its excellent bioadhesion. Furthermore, PDA possesses strong free radical scavenging and char-forming capabilities, making it a promising candidate for flame retardancy in fabrics. However, PDA is typically not used alone as a flame retardant and requires synergistic use with other flame retardants. Polyethyleneimine (PEI), as a polyelectrolyte, has amino groups in its molecular structure that can chemically react with PDA to form stable chemical bonds. Phosphorus-based flame retardants are ideal alternatives to halogenated flame retardants, offering advantages such as high efficiency, low smoke, low toxicity, and low volatility. In the presence of nitrogen, they not only exert gas-phase flame retardant effects but also promote the condensed-phase flame retardancy of phosphorus-based flame retardants. Therefore, this invention achieves synergistic phosphorus-nitrogen flame retardancy in polyester-cotton fabrics by designing a novel combination of a phosphorus-based flame retardant and a nitrogen-containing flame retardant. Summary of the Invention

[0004] The purpose of this invention is to address the challenge of improving the flame retardancy of polyester-cotton fabrics by providing a method for preparing phosphorus-nitrogen (PN) polyester-cotton fabrics with synergistic flame-retardant properties. This method achieves a synergistic effect between two flame retardants by designing and synthesizing a phosphorus-based flame retardant and combining it with a nitrogen-based flame retardant. First, a phosphorus-based flame retardant is prepared through specific synthesis steps. Then, the phosphorus-based and nitrogen-based flame retardants are formulated into a solution. Next, the polyester-cotton fabric is sequentially immersed in a polydopamine-polyethyleneimine co-deposition solution and a phosphorus-based flame retardant solution, allowing them to fully bond together. Finally, after drying, a PN polyester-cotton fabric with excellent flame-retardant properties is obtained. The advantage of this method lies in promoting the thermal degradation and carbonization process of cotton fibers, forming a heat-insulating char layer. The synergistic effect between the phosphorus-based and nitrogen-based flame retardants delays the dripping of polyester fibers, improving the flame-retardant effect of the fabric. This preparation method is simple and easy to implement, providing an effective and efficient solution for the flame-retardant treatment of polyester-cotton fabrics.

[0005] The objective of this invention is achieved through the following technical solution.

[0006] A method for preparing phosphorus and nitrogen synergistic flame-retardant polyester-cotton fabric includes the following steps:

[0007] (1) Pretreatment of polyester-cotton fabrics

[0008] The polyester-cotton fabric is pretreated to neutral and then dried for later use.

[0009] (2) Preparation of phosphorus-containing flame retardants

[0010] Under room temperature and stirring conditions, the same molar amount of phosphorus oxychloride was added dropwise to neopentyl glycol; the product obtained after continuous reaction at 80°C was neopentyl glycol phosphoryl chloride, which is the phosphorus-containing flame retardant DPPC. The phosphorus-containing flame retardant DPPC was washed and dried, and then DPPC was prepared into a DPPC solution for later use.

[0011] (3) Preparation of polydopamine-polyethyleneimine (PDA-PEI) co-deposition solution

[0012] Prepare a tris(hydroxymethyl)aminomethane (Tris) buffer solution and adjust its pH to 8.5 with HCl solution; dissolve dopamine hydrochloride (DA) and PEI uniformly in the Tris buffer solution to obtain a PDA-PEI co-precipitation solution; wherein the mass ratio of Tris:DA:PEI is 1-2:1:1.

[0013] (4) Preparation of phosphorus-nitrogen synergistic flame retardant coating

[0014] The pretreated polyester-cotton fabric from step one is immersed in a PDA-PEI co-deposition solution for a certain period of time. After immersion, excess solution is squeezed out and then rinsed with deionized water to remove physically bound solutes from the surface. The fabric is then immersed in a DPPC solution for a certain period of time, and after immersion, excess liquid is squeezed out and rinsed with deionized water to remove unbound substances from the surface. Finally, the flame-retardant polyester-cotton fabric is dried in a forced-air drying oven to obtain a phosphorus-nitrogen synergistic flame-retardant polyester-cotton fabric.

[0015] Preferably, the drying temperature in step (1) is 60-80℃ and the drying time is 1.5h.

[0016] Preferably, in step (2), the initial reaction temperature is room temperature, the temperature is raised to 80°C after the addition is completed, and the reaction time is extended to 4 hours. The concentrations of DPPC are 0, 35 g / L, and 70 g / L, respectively.

[0017] Preferably, in step (3), the concentrations of DA and PEI are both 2 g / L.

[0018] Preferably, in step (4), the soaking time of the co-deposition solution is 2 hours, the soaking time of the DPPC solution is 1 hour, the drying temperature is 60°C, and the drying time is 1 hour.

[0019] Beneficial effects

[0020] 1. The phosphorus-containing flame retardant DPPC in this invention produces acidic substances such as phosphoric acid during thermal degradation. These substances act as catalysts, accelerating the thermal degradation and eventual dehydration and carbonization of cotton fibers in polyester-cotton fabrics, promoting the formation of a char layer, and achieving a flame-retardant effect in the condensed phase. Simultaneously, it helps to block flammable gases and external oxygen. Furthermore, the reaction between the phosphorus-containing flame retardant and the polyester-cotton fibers allows them to form char and adhere to the cotton fibers, preventing dripping.

[0021] 2. The PDA-PEI co-deposition system can achieve bio-adhesion on polyester-cotton fabrics, forming a cross-linked network structure and providing a platform for secondary reactions. DPPC can then react with PDA and PEI, resulting in a stronger binding effect. Simultaneously, the nitrogen-containing flame retardant produces inert gases during thermal decomposition, which can dilute the concentration of oxygen and combustible gases, achieving gas-phase flame retardancy. Furthermore, PDA possesses free radical scavenging and char-forming capabilities, allowing it to work in conjunction with phosphorus-containing flame retardants to effectively suppress the melting effect of nylon fibers.

[0022] 3. The finishing technology for polyester-cotton fabrics in this invention is simple and the conditions are mild and controllable. This invention uses a step-by-step impregnation coating assembly method to apply PEI, PDA, and DPPC onto polyester-cotton fabrics to construct a flame-retardant coating. Nitrogen- and phosphorus-containing flame retardants exert a synergistic flame-retardant effect. Furthermore, as the concentration of DPPC increases, the peak heat release value gradually decreases in cone calorimeter testing, and the total heat release also decreases, demonstrating a good flame-retardant effect.

[0023] 4. This invention synthesizes phosphorus-containing flame retardants in neopentyl glycol by adding phosphorus oxychloride dropwise. The resulting phosphorus-containing flame retardant is washed, dried, and then prepared into a solution of a certain concentration. Then, a polydopamine-polyethyleneimine (PDA-PEI) co-deposition solution is applied. This simple two-step impregnation method easily achieves the preparation of phosphorus-nitrogen synergistic flame-retardant polyester-cotton fabrics. In this invention, the phosphorus-containing flame retardant accelerates the thermal degradation and dehydration carbonization of cotton fibers in polyester-cotton fabrics, forming a char layer and blocking flammable gases and external oxygen. The PDA-PEI co-deposition system forms a cross-linked network structure and works synergistically with the phosphorus-containing flame retardant to effectively inhibit the melting effect of nylon fibers. This invention has a simple preparation process, good flame-retardant effect, and can be applied to the flame-retardant treatment of polyester-cotton fabrics, improving their flame-retardant performance and reducing fire risk. Compared to untreated polyester-cotton fabrics, flame-retardant polyester-cotton fabrics (PDA-PEI / DPPC-70) showed a 57.8% reduction in peak heat release and a 32.6% reduction in total heat release, demonstrating a significant improvement in heat release and exhibiting excellent phosphorus-nitrogen synergistic flame-retardant effect. Detailed Implementation

[0024] The present invention will now be described in detail with reference to embodiments, which are intended to explain rather than limit the invention.

[0025] Comparative Example 1

[0026] A method for preparing phosphorus and nitrogen synergistic flame-retardant polyester-cotton fabric, wherein the preparation method of the flame-retardant polyester-cotton fabric is as follows:

[0027] (1) Pretreatment of polyester-cotton fabrics

[0028] Place the original polyester-cotton fabric in deionized water and sonicate at 40-50℃ for 30 minutes; remove the fabric and place it in a prepared 0.1wt% sodium hydroxide solution and sonicate at 60-70℃ for 30 minutes; remove the fabric and sonicate it with deionized water until the pH of the solution is 7; remove the washed fabric and place it in an oven and dry at 60-80℃ for 1.5 hours.

[0029] (2) Preparation of phosphorus-containing flame retardants

[0030] Phosphorus oxychloride was added dropwise to neopentyl glycol under mechanical stirring and at room temperature. After the addition was complete, the reaction temperature was raised to 80°C and the reaction was continued for 4 hours. The crude product obtained was neopentyl glycol phosphoric acid chloride (DPPC), which was then washed and dried for later use. A certain mass of DPPC was weighed and completely dissolved by ultrasonic treatment to prepare a 70 g / L DPPC solution.

[0031] (3) Preparation of phosphorus-containing flame-retardant coating

[0032] The removed fabric was immersed in DPPC solution for 1 hour, then squeezed to remove excess liquid and rinsed with deionized water to remove unbound substances from the surface. Finally, the flame-retardant polyester-cotton fabric was dried in a 60℃ forced-air drying oven for 1 hour, and then placed in a constant temperature and humidity chamber at 20±2℃ and 65±5% for 48 hours.

[0033] The treated flame-retardant polyester-cotton fabric (DPPC-70) was tested according to ISO 5660-1:2015, and the peak heat release value (pHRR) and total heat release value (THR) were 178.1 kW / m2 and 5.86 MJ / m2, respectively.

[0034] Comparative Example 2

[0035] A method for preparing phosphorus and nitrogen synergistic flame-retardant polyester-cotton fabric, wherein the preparation method of the flame-retardant polyester-cotton fabric is as follows:

[0036] (1) Pretreatment of polyester-cotton fabrics

[0037] Place the original polyester-cotton fabric in deionized water and sonicate at 40-50℃ for 30 minutes; remove the fabric and place it in a prepared 0.1wt% sodium hydroxide solution and sonicate at 60-70℃ for 30 minutes; remove the fabric and sonicate it with deionized water until the pH of the solution is 7; remove the washed fabric and place it in an oven and dry at 60-80℃ for 1.5 hours.

[0038] (2) Preparation of polydopamine-polyethyleneimine (PDA-PEI) co-deposition solution

[0039] Prepare a 50 mmol / L tris(hydroxymethyl)aminomethane (Tris) buffer solution and adjust its pH to 8.5 with 1 mol / L HCl solution. Weigh out a certain amount of dopamine hydrochloride (DA) and PEI, and dissolve both substances uniformly in the Tris buffer solution to a concentration of 2 g / L, thus obtaining a PDA-PEI co-precipitation solution.

[0040] (3) Preparation of nitrogen-containing flame-retardant coating

[0041] The pretreated polyester-cotton fabric was immersed in a PDA-PEI co-deposition solution for 2 hours. After immersion, excess solution was squeezed out, and the fabric was rinsed with plenty of deionized water. Then, the flame-retardant polyester-cotton fabric was dried in a 60°C forced-air drying oven for 1 hour, and then placed in a constant temperature and humidity chamber at 20±2°C and 65±5% for 48 hours.

[0042] The treated flame-retardant polyester-cotton fabric (PDA-PEI) was tested according to ISO 5660-1:2015, and the peak heat release value (pHRR) and total heat release value (THR) were 288.3 kW / m². 2 and 7.02MJ / m 2 .

[0043] Example 1

[0044] A method for preparing phosphorus and nitrogen synergistic flame-retardant polyester-cotton fabric, wherein the preparation method of the flame-retardant polyester-cotton fabric is as follows:

[0045] (1) Pretreatment of polyester-cotton fabrics

[0046] Place the original polyester-cotton fabric in deionized water and sonicate at 40-50℃ for 30 minutes; remove the fabric and place it in a prepared 0.1wt% sodium hydroxide solution and sonicate at 60-70℃ for 30 minutes; remove the fabric and sonicate it with deionized water until the pH of the solution is 7; remove the washed fabric and place it in an oven and dry at 60-80℃ for 1.5 hours.

[0047] (2) Preparation of phosphorus-containing flame retardants

[0048] Phosphorus oxychloride was added dropwise to neopentyl glycol under mechanical stirring and at room temperature. After the addition was complete, the reaction temperature was raised to 80°C and the reaction was continued for 4 hours. The crude product obtained was neopentyl glycol phosphoric acid chloride (DPPC), which was then washed and dried for later use. A certain mass of DPPC was weighed and completely dissolved by ultrasonic treatment to prepare a DPPC solution with a concentration of 35 g / L.

[0049] (3) Preparation of polydopamine-polyethyleneimine (PDA-PEI) co-deposition solution

[0050] Prepare a 50 mmol / L tris(hydroxymethyl)aminomethane (Tris) buffer solution and adjust its pH to 8.5 with 1 mol / L HCl solution. Weigh out a certain amount of dopamine hydrochloride (DA) and PEI, and dissolve both substances uniformly in the Tris buffer solution to a concentration of 2 g / L, thus obtaining a PDA-PEI co-precipitation solution.

[0051] (4) Preparation of phosphorus-nitrogen synergistic flame retardant coating

[0052] The pretreated polyester-cotton fabric was immersed in a PDA-PEI co-deposition solution for 2 hours. After removal, excess solution was squeezed out, and then the fabric was rinsed thoroughly with deionized water. The removed fabric was then immersed in a DPPC solution for 1 hour, and after removal, excess liquid was squeezed out and the fabric was rinsed with deionized water to remove unbound substances from the surface. Finally, the flame-retardant polyester-cotton fabric was dried in a 60℃ forced-air drying oven for 1 hour, and then placed in a constant temperature and humidity chamber at 20±2℃ and 65±5% for 48 hours.

[0053] The treated flame-retardant polyester-cotton fabric (PDA-PEI / DPPC-35) was tested according to ISO 5660-1:2015, and the peak heat release value (pHRR) and total heat release value (THR) were 209.5 kW / m2 and 5.66 MJ / m2, respectively.

[0054] Example 2

[0055] A method for preparing phosphorus and nitrogen synergistic flame-retardant polyester-cotton fabric, wherein the preparation method of the flame-retardant polyester-cotton fabric is as follows:

[0056] (1) Pretreatment of polyester-cotton fabrics

[0057] Place the original polyester-cotton fabric in deionized water and sonicate at 40-50℃ for 30 minutes; remove the fabric and place it in a prepared 0.1wt% sodium hydroxide solution and sonicate at 60-70℃ for 30 minutes; remove the fabric and sonicate it with deionized water until the pH of the solution is 7; remove the washed fabric and place it in an oven and dry at 60-80℃ for 1.5 hours.

[0058] (2) Preparation of phosphorus-containing flame retardants

[0059] Phosphorus oxychloride was added dropwise to neopentyl glycol under mechanical stirring and at room temperature. After the addition was complete, the reaction temperature was raised to 80°C and the reaction was continued for 4 hours. The crude product obtained was neopentyl glycol phosphoric acid chloride (DPPC), which was then washed and dried for later use. A certain mass of DPPC was weighed and completely dissolved by ultrasonic treatment to prepare a 70 g / L DPPC solution.

[0060] (3) Preparation of polydopamine-polyethyleneimine (PDA-PEI) co-deposition solution

[0061] Prepare a 50 mmol / L tris(hydroxymethyl)aminomethane (Tris) buffer solution and adjust its pH to 8.5 with 1 mol / L HCl solution. Weigh out a certain amount of dopamine hydrochloride (DA) and PEI, and dissolve both substances uniformly in the Tris buffer solution to a concentration of 2 g / L, thus obtaining a PDA-PEI co-precipitation solution.

[0062] (4) Preparation of phosphorus-nitrogen synergistic flame retardant coating

[0063] The pretreated polyester-cotton fabric was immersed in a PDA-PEI co-deposition solution for 2 hours. After removal, excess solution was squeezed out, and then the fabric was rinsed thoroughly with deionized water. The removed fabric was then immersed in a DPPC solution for 1 hour, and after removal, excess liquid was squeezed out and the fabric was rinsed with deionized water to remove unbound substances from the surface. Finally, the flame-retardant polyester-cotton fabric was dried in a 60℃ forced-air drying oven for 1 hour, and then placed in a constant temperature and humidity chamber at 20±2℃ and 65±5% for 48 hours.

[0064] The treated flame-retardant polyester-cotton fabric (PDA-PEI / DPPC-70) was tested according to ISO 5660-1:2015, and the peak heat release value (pHRR) and total heat release value (THR) were 146.7 kW / m². 2 and 4.82MJ / m 2 .

[0065] Table 1 shows that the peak heat release of polyester-cotton fabrics coated with PDA-PEI (nitrogen-containing flame retardant) alone or DPPC (phosphorus-containing flame retardant) alone is lower than that of untreated polyester-cotton fabrics, and the total heat release value also decreases due to the coating. However, compared with polyester-cotton fabrics with phosphorus-nitrogen synergistic flame retardant coatings, nitrogen-containing or phosphorus-containing flame retardant coatings alone do not achieve more efficient flame retardancy. When the two are combined, they can exert a synergistic flame retardant effect. Therefore, the flame retardant effect of Example 2 is better than that of Comparative Examples 1 and 2. At the same time, as the DPPC concentration gradually increases, pHRR and THR also gradually decrease. When the DPPC concentration is 70 g / L, pHRR decreases by 57.8% and THR decreases by 32.6% compared with the original untreated polyester-cotton fabric, demonstrating excellent flame retardant performance. The phosphorus-nitrogen synergistic flame-retardant coating plays a positive role in promoting char formation. DPPC and PDA catalyze char formation, and the rapid formation of the char layer prevents further degradation of the internal fibers. Simultaneously, the char layer isolates external heat and oxygen, preventing further degradation and acting as a physical barrier. Furthermore, the non-combustible gases generated during the thermal degradation of the phosphorus-nitrogen synergistic flame-retardant fabric dilute the concentration of combustible gases, reducing fuel supply and effectively mitigating the spread of fire. In summary, the phosphorus-nitrogen flame-retardant coating works in both the gas and condensed phases, enhancing the flame retardancy of polyester-cotton fabrics.

[0066] Table 1. Cone calorimeter test results of fabrics before and after flame retardant treatment.

[0067]

[0068]

[0069] The above detailed description further illustrates the purpose, technical solution, and beneficial effects of the invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for the preparation of phosphorus-nitrogen synergistic flame retardant polyester-cotton fabric, characterized by: It comprises the following steps: (1) Pretreatment of polyester-cotton fabric The pretreatment of polyester-cotton fabric is neutral, and the fabric is dried for standby; (2) Preparation of phosphorus-containing flame retardant Under the conditions of room temperature and stirring, the same molar amount of phosphorus oxychloride is added dropwise into neopentyl glycol; after the reaction is continuously carried out at 80°C, the obtained product neopentyl glycol phosphorus oxychloride is the phosphorus-containing flame retardant; the phosphorus-containing flame retardant is washed and dried, and then the phosphorus-containing flame retardant is prepared into a phosphorus-containing flame retardant solution for standby; (3) Preparation of PDA-PEI co-deposition solution Tris buffer solution is prepared, and the pH value is adjusted to 8.5 by using HCl solution; dopamine hydrochloride and polyethyleneimine PEI are uniformly dissolved in the Tris buffer solution to obtain a PDA-PEI co-deposition solution; the mass ratio of Tris:dopamine hydrochloride:polyethyleneimine PEI is 1-2:1:1; (4) Preparation of phosphorus-nitrogen synergistic flame-retardant coating The pretreated polyester-cotton fabric in step (1) is immersed in the PDA-PEI co-deposition solution, and after being taken out, the excess solution is squeezed out, then washed with deionized water to remove the physically combined solute on the surface; then immersed in the phosphorus-containing flame retardant solution, and after being taken out, the excess liquid is squeezed out and washed with deionized water to remove the uncombined substances on the surface; finally, the flame-retardant polyester-cotton fabric is placed in a drying oven for drying to obtain a phosphorus-nitrogen synergistic flame-retardant polyester-cotton fabric.

2. A process for preparing phosphorus-nitrogen synergistic flame retardant polyester-cotton fabric as claimed in claim 1 wherein: The drying temperature in step (1) is 60-80°C, and the drying time is 1.5 h.

3. A process for preparing phosphorus-nitrogen synergistic flame retardant polyester-cotton fabric as claimed in claim 1 wherein the process comprises of: In step (2), the initial reaction temperature is room temperature, the temperature is raised to 80°C after the dropwise addition is completed, and the reaction time is extended to 4 h.

4. A process for preparing phosphorus-nitrogen synergistic flame retardant polyester-cotton fabric as claimed in claim 1 wherein the process comprises of: In step (4), the soaking time of the co-deposition solution is 2 h, the soaking time of the phosphorus-containing flame retardant solution is 1 h, the drying temperature is 60°C, and the drying time is 1 h.

5. The method for preparing phosphorus and nitrogen synergistic flame-retardant polyester-cotton fabric as described in claim 1, characterized in that: The concentration of dopamine hydrochloride and polyethyleneimine PEI is both 2 g / L.

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