Layer-by-layer assembly preparation method of organic-inorganic hybrid flame-retardant coating polyester fabric

Abstract

The invention belongs to the technical field of flame-retardant functional textiles, and particularly relates to a layer-by-layer assembly preparation method of an organic-inorganic hybrid flame-retardant coating polyester fabric. The method comprises the following steps: dipping a polyester fabric in a sodium hydroxide aqueous solution, washing with water, drying, dipping in a polyethyleneimine aqueous solution, drying, dipping in a hectorite and chitosan composite aqueous solution, drying, dipping in a polyethyleneimine aqueous solution, drying, dipping in a phytic acid aqueous solution, and drying. And dipping in a citric acid / sodium citrate buffer solution, washing with water, pre-drying and curing. The hectorite, the chitosan, the phytic acid and the polyethyleneimine are used for synergic flame retardance, the prepared flame-retardant coating polyester fabric is excellent in flame retardance, washable and durable, the limit oxygen index can reach 29%, the damaged length is not larger than 5 cm, the limit oxygen index of the flame-retardant coating polyester blended fabric is almost not reduced after the flame-retardant coating polyester blended fabric is washed five times, and the effects that the number of assembly layers is small, and the flame retardance is good are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of flame-retardant functional textiles, and particularly relates to a layer-by-layer assembly preparation method of an organic-inorganic hybrid flame-retardant coated polyester fabric. Background Art

[0002] Polyester (polyester fiber) is widely used in clothing, home furnishings and industrial fields due to its high strength, wear resistance and easy processing. However, polyester is a thermoplastic fiber that easily melts and drips when exposed to fire and accelerates combustion, posing a serious fire hazard. Traditional flame retardant modification methods (such as blending modification or post-finishing coating) often face problems such as easy migration of flame retardants, poor water washability, and environmental unfriendliness. For example, halogen-based flame retardants are highly effective but toxic, while phosphorus-nitrogen-based flame retardants are easily washed away by water and are difficult to meet long-term use requirements.

[0003] In recent years, layer-by-layer self-assembly technology has become a research hotspot for flame retardant modification due to its ability to construct nanoscale coatings through intermolecular forces. However, the polyester surface is highly chemically inert, the coating has weak bonding strength, and a single organic or inorganic flame retardant system is difficult to achieve both flame retardant efficiency and durability. For example, the literature (Application of electrostatic layer-by-layer self-assembly in flame retardant finishing of cotton fabrics [J]. Printing and Dyeing, 2018, 44(7): 40-44.) successfully assembled ammonium polyphosphate and chitosan onto the surface of cotton fabric for flame retardant finishing using the electrostatic layer-by-layer self-assembly method. After 20 layers of assembly, the flame retardant properties of the cotton fabric were improved. However, the coating was unable to bond with the cotton fabric and was deposited on the surface of the cotton fabric only by the ionic bond between the two, resulting in poor durability.

[0004] CN117488551A provides a controllable preparation method for a nano-composite flame-retardant coating based on silicon-containing inorganic particles. Silicon-containing inorganic particles, polyethyleneimine (PEI) and phytic acid (PA) flame retardant are assembled layer by layer on the surface of cotton fabric through a layer-by-layer assembly method. The silicon-containing inorganic particles can be silicon dioxide (SiO2), attapulgite (ATTA) or montmorillonite (MMT). By adjusting the preparation process conditions, the cotton fabric has good flame retardant properties after assembling multiple layers.

[0005] CN105951419B uses phosphazene compounds as positively charged electrolytes and hypophosphorous acid compounds containing DOPO structures as negatively charged electrolytes, and flame-retards polyester fabrics through layer-by-layer self-assembly, giving the fabric certain flame retardant properties with 5 to 30 flame retardant layers.

[0006] Existing flame-retardant finishing methods for fabrics are complex and tedious, and methods using layer-by-layer self-assembly require a large number of layers to achieve the desired flame-retardant effect. Therefore, developing a simple, environmentally friendly, washable, and highly flame-retardant organic-inorganic hybrid coating technology is of great significance for the functionalization of polyester fabrics. Summary of the Invention

[0007]

Technical Issues

[0008] The layer-by-layer self-assembly flame-retardant finishing method is complex and tedious, and its flame retardant performance and washability are poor. It is necessary to develop a simple, environmentally friendly, washable, and highly flame-retardant single-layer self-assembly flame-retardant finishing method for polyester.

[0009]

Technical solution

[0010] The present invention addresses the problems of weak coating adhesion, poor water resistance, insufficient flame retardant efficiency, and complicated and tedious procedures in the flame retardant modification of polyester in the prior art, and provides a layer-by-layer self-assembly preparation method for organic-inorganic hybrid flame retardant coated polyester fabric. The fiber surface is activated by sodium hydroxide pretreatment, and the synergistic flame retardant design of inorganic nanosheets and bio-based polymers is combined. A citric acid / sodium citrate buffer solution is impregnated to produce a water-insoluble coating on the fabric surface to achieve efficient and durable flame retardancy. The interfacial bonding between the fiber and the coating is enhanced by surface activation pretreatment, and the physical barrier effect of the inorganic nanosheets and the catalytic carbonization effect of the organic components are combined to achieve efficient synergistic flame retardancy.

[0011] The first object of the present invention is to provide a layer-by-layer self-assembly preparation method of an organic-inorganic hybrid flame-retardant coated polyester fabric, comprising the steps of:

[0012] (1) Dipping the polyester fabric in a sodium hydroxide aqueous solution, taking it out, washing it with water, and drying it;

[0013] (2) immersing the polyester fabric obtained in step (1) in a polyethyleneimine aqueous solution, taking it out and drying it;

[0014] (3) immersing the polyester fabric obtained in step (2) in a composite aqueous solution of hectorite (lithium magnesium silicate) and chitosan, taking it out and drying it;

[0015] (4) immersing the polyester fabric obtained in step (3) in a polyethyleneimine aqueous solution, taking it out and drying it;

[0016] (5) immersing the polyester fabric obtained in step (4) in a phytic acid aqueous solution, taking it out and drying it;

[0017] (6) Immersing the polyester fabric obtained in step (5) in a citric acid / sodium citrate buffer solution, taking it out, washing it with water, pre-drying it, and curing it.

[0018] In one embodiment of the present invention, in step (1), the concentration of the sodium hydroxide aqueous solution is 15 to 25 g / L; the immersion temperature is 55 to 65° C.; and the immersion time is 40 to 80 minutes. Alkaline hydrolysis introduces carboxyl and hydroxyl groups onto the polyester fiber surface, improving the activity of the fabric surface and forming a micron-scale rough structure, which helps enhance the adhesion of subsequent coatings.

[0019] In one embodiment of the present invention, in step (2), the concentration of the polyethyleneimine aqueous solution is 0.5-1.5 wt %, the immersion temperature is 10-40° C., and the immersion time is 5-20 min.

[0020] In one embodiment of the present invention, in step (3), the hectorite concentration of the composite aqueous solution is 1.5-2.5 wt%; the chitosan concentration of the composite aqueous solution is 0.05-0.2 wt%; the immersion temperature is 10-40° C.; and the immersion time is 5-20 min.

[0021] In one embodiment of the present invention, in step (4), the concentration of the polyethyleneimine aqueous solution is 4 to 10 wt %; the immersion temperature is 10 to 40° C.; and the immersion time is 5 to 20 min.

[0022] In one embodiment of the present invention, in step (5), the concentration of the phytic acid aqueous solution is 4 to 10 wt %; the immersion temperature is 10 to 40° C.; and the immersion time is 5 to 20 min.

[0023] In one embodiment of the present invention, in step (6), the pH value of the citric acid / sodium citrate buffer solution is 3.8-4.2, the immersion temperature is 10-40°C; the immersion time is 3-10 minutes; the pre-drying temperature is 60-80 minutes; the pre-drying time is 1-5 minutes; the curing temperature is 130-155°C; and the curing time is 1-5 minutes.

[0024] In one embodiment of the present invention, in steps (1) to (5), drying is performed to a constant weight.

[0025] In one embodiment of the present invention, in steps (1) to (5), the drying temperature is 40 to 80°C.

[0026] The second object of the present invention is to provide an organic-inorganic hybrid flame-retardant coated polyester fabric prepared by the above-mentioned layer-by-layer self-assembly preparation method.

[0027] The third object of the present invention is to provide the application of the organic-inorganic hybrid flame retardant coated polyester fabric in the field of textiles.

[0028] Beneficial effects:

[0029] This invention utilizes laponite, chitosan, phytic acid, and polyethyleneimine as synergistic flame retardants. The resulting flame-retardant coated polyester fabric achieves a limiting oxygen index of up to 29% and a damage length of no more than 5 cm. The laponite nanosheets form a dense physical barrier during combustion, inhibiting the diffusion of heat and oxygen. Chitosan and phytic acid catalyze dehydration to form char at high temperatures. Polyethyleneimine acts as a gas source to promote the formation of an expanded char layer, isolating combustible gases.

[0030] Flame-retardant polyester fabrics are prepared through single-layer flame-retardant coating assembly technology, which makes the prepared polyester fabrics have excellent flame retardancy, achieves the effect of few assembly layers and good flame retardant performance, and overcomes the technical difficulties of the current layer-by-layer self-assembly technology that requires repeated deposition of multiple layers.

[0031] The resulting organic-inorganic hybrid flame-retardant coated polyester fabric exhibits excellent washability and a long service life. Sodium hydroxide pretreatment generates active groups on the polyester surface and increases roughness, enhancing the coating's adhesion. Through a combination of electrostatic adsorption, hydrogen bonding, and covalent bonding, the coating forms a water-insoluble coating on the fabric surface after immersion in a buffer solution. This significantly improves the fabric's water resistance, effectively reducing water penetration and extending its service life. After five standard washes (GB / T 3921-2008), the limiting oxygen index (LOI) remains above 28%.

[0032] The invention adopts bio-based chitosan and halogen-free phytic acid to avoid the release of toxic substances, and the preparation method is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Surface morphology of untreated polyester fabric and flame retardant coated polyester fabric prepared in Example 3;

[0034] Figure 2 These are the vertical burning test results of untreated polyester fabric and the flame retardant coated polyester fabric prepared in Example 3. DETAILED DESCRIPTION

[0035] Test Method

[0036] Weight gain rate: The weight gain rate of coated fabric is the percentage of the mass difference between coated fabric and uncoated fabric to the mass of uncoated fabric.

[0037] Limiting oxygen index: GB / T 5454-1997 "Textile combustion performance test oxygen index method" is used to test the limiting oxygen index of durable flame retardant coated polyester textiles. The original polyester fabric and the prepared flame retardant polyester fabric are cut into at least 3 pieces, with a sample size of approximately 10×5 cm. 2 In the oxygen-nitrogen mixed flow, the minimum oxygen concentration required to maintain its combustion is expressed as a percentage.

[0038] Damage length: GB / T 5455-2014 “Fire performance of textiles - Determination of damage length in vertical direction - Smoldering and afterflaming time” is used to test the damage length of durable flame retardant coated polyester fabrics.

[0039] Limiting oxygen index after 5 washes: In the present invention, the durable flame retardant coated polyester textile was washed according to AATCC 61-2013 "Accelerated Test Method for Color Fastness to Laundry Use for Household and Commercial Use" and the limiting oxygen index of the durable flame retardant coated polyester textile was tested using GB / T 5454-1997 "Textiles Burning Behavior Test - Oxygen Index Method";

[0040] Example 1

[0041] A layer-by-layer self-assembly preparation method of an organic-inorganic hybrid flame-retardant coated polyester fabric comprises the following steps:

[0042] (1) 70D*160D / 137*74*105g / m 2 The polyester fabric was immersed in 20g / L sodium hydroxide aqueous solution at 60℃ for 60min, then washed with water and dried at 60-70℃;

[0043] (2) immersing the polyester fabric obtained in step (1) in a 1 wt% aqueous solution of polyethyleneimine at room temperature (25° C.) for 10 minutes, and then drying at 60-70° C.;

[0044] (3) immersing the polyester fabric obtained in step (2) in a composite aqueous solution of hectorite and chitosan at room temperature for 10 minutes, taking it out and drying it at 60-70° C.; the composite aqueous solution has a hectorite concentration of 2 wt% and a chitosan concentration of 0.1 wt%;

[0045] (4) immersing the polyester fabric obtained in step (3) in a 4 wt % aqueous solution of polyethyleneimine at room temperature for 10 min, and drying at 60-70° C. after removal;

[0046] (5) Immersing the polyester fabric obtained in step (4) in a 4 wt% phytic acid aqueous solution at room temperature for 10 min, then drying at 60-70° C.

[0047] (6) The polyester fabric obtained in step (5) was immersed in a citric acid / sodium citrate buffer solution with a pH value of 4 at room temperature for 5 minutes, taken out and washed with deionized water, pre-dried at 70°C for 3 minutes, and then cured at 145°C for 3 minutes.

[0048] Example 2

[0049] A layer-by-layer self-assembly preparation method for organic-inorganic hybrid flame-retardant coated polyester fabric, which differs from Example 1 only in that the concentration of the polyethyleneimine aqueous solution in step (4) is 6wt%, and the concentration of the phytic acid aqueous solution in step (5) is 6wt%.

[0050] Example 3

[0051] A layer-by-layer self-assembly preparation method for organic-inorganic hybrid flame-retardant coated polyester fabric is different from Example 1 only in that the concentration of the polyethyleneimine aqueous solution in step (4) is 10wt%, and the concentration of the phytic acid aqueous solution in step (5) is 10wt%.

[0052] Comparative Example 1

[0053] A method for preparing a flame-retardant polyester fabric comprises the following steps:

[0054] (1) 70D*160D / 137*74*105g / m 2 The polyester fabric was immersed in 20g / L sodium hydroxide aqueous solution at 60℃ for 60min, then washed with water and dried at 60-70℃;

[0055] (2) immersing the polyester fabric obtained in step (1) in a 1 wt% aqueous solution of polyethyleneimine at room temperature (25° C.) for 10 minutes, and then drying at 60-70° C.;

[0056] (3) immersing the polyester fabric obtained in step (2) in a composite aqueous solution of hectorite and chitosan at room temperature for 10 minutes, taking it out and drying it at 60-70° C.; the composite aqueous solution has a hectorite concentration of 2 wt% and a chitosan concentration of 0.1 wt%;

[0057] Comparative Example 2

[0058] A method for preparing a flame-retardant polyester fabric comprises the following steps:

[0059] (1) 70D*160D / 137*74*105g / m 2 The polyester fabric was immersed in 20g / L sodium hydroxide aqueous solution at 60℃ for 60min, then washed with water and dried at 60-70℃;

[0060] (2) immersing the polyester fabric obtained in step (1) in a 6 wt % aqueous solution of polyethyleneimine at room temperature (25° C.) for 10 min, and drying at 60-70° C. after removal;

[0061] (3) Immersing the polyester fabric obtained in step (2) in a 6 wt % phytic acid aqueous solution at room temperature for 10 min, and then drying at 60-70° C.;

[0062] The weight gain rate, limiting oxygen index, damaged length and limiting oxygen index after 5 water washings of Examples 1 to 3 and Comparative Examples 1 and 2 were tested, and the results are shown in the following table.

[0063] Table 1

[0064]

[0065] The concentrations of the polyethyleneimine aqueous solution and the phytic acid aqueous solution used in steps (4) and (5) of Examples 1 to 3 increased successively, and the weight gain rate and LOI of the flame-retardant coated polyester fabric increased, indicating that as the concentrations of the polyethyleneimine aqueous solution and the phytic acid aqueous solution increased, more flame-retardant coating was deposited, the oxygen concentration required to maintain combustion was higher, and the flame retardant effect was better. Figure 1 Figures 2 and 3 show the surface morphology of untreated polyester fabric (PET) and the flame-retardant-coated polyester fabric prepared in Example 3. The flame-retardant-coated polyester fabric prepared in Example 3 exhibits a dense coating. As shown in Table 1, the LOI value of the flame-retardant-coated polyester fabric barely decreases after five washes. This demonstrates that the present invention achieves excellent flame retardancy through single-layer self-assembly, achieving excellent flame retardancy with a minimal number of assembled layers. Furthermore, the resulting coating is washable and durable. Figure 2 The vertical burning test results of untreated polyester fabric and the flame-retardant coated polyester fabric prepared in Example 3. After the layer-by-layer self-assembly method of the present invention, the damage length of the flame-retardant coated polyester fabric prepared in Example 3 was less than 5 cm, which was significantly reduced compared with the untreated polyester fabric.

[0066] Comparative Example 1 only undergoes sodium hydroxide pretreatment, 1wt% polyethyleneimine impregnation, and hectorite chitosan composite aqueous solution impregnation. The weight gain of the polyester fabric prepared increases, but the LOI value decreases, indicating that the organic-inorganic particle coating successfully grows on the coating, but only a layer of hectorite and chitosan is deposited on the polyester fabric, which does not effectively improve its flame retardant properties. It may even slightly reduce the flame retardancy due to the introduction of certain combustible substances or changes in the surface structure of the fabric. Comparative Example 2 only undergoes sodium hydroxide pretreatment, 6wt% polyethyleneimine impregnation, and phytic acid impregnation. The flame retardant coated polyester fabric prepared has a significantly lower weight gain and LOI value than Example 2, and after 5 washes, the LOI value decreases significantly. This shows that the hectorite / chitosan layer is omitted and a higher concentration of PEI and phytic acid is used for impregnation. Although flame retardant components are also introduced, the resulting coating is not as good as the complete layer-by-layer self-assembly system of Example 2 in terms of flame retardant efficiency, bonding strength with the substrate, and durability. The reason is that the hectorite / chitosan layer optimizes the coating structure in the layer-by-layer self-assembled flame retardant system, enhances the synergistic flame retardant effect between the components, and improves the bonding strength and durability between the coating and the substrate. These factors together lead to the fact that Example 2 is superior to Comparative Example 2 in both LOI value and water washability.

[0067] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A layer-by-layer self-assembly preparation method of organic-inorganic hybrid flame-retardant coated polyester fabric, characterized in that: Including steps: (1) Dipping the polyester fabric in a sodium hydroxide aqueous solution, taking it out, washing it with water, and drying it; (2) immersing the polyester fabric obtained in step (1) in a polyethyleneimine aqueous solution, taking it out and drying it; (3) immersing the polyester fabric obtained in step (2) in a composite aqueous solution of hectorite and chitosan, taking it out and drying it; (4) immersing the polyester fabric obtained in step (3) in a polyethyleneimine aqueous solution, taking it out and drying it; (5) immersing the polyester fabric obtained in step (4) in a phytic acid aqueous solution, taking it out and drying it; (6) Immersing the polyester fabric obtained in step (5) in a citric acid / sodium citrate buffer solution, taking it out, washing it with water, pre-drying it, and curing it.

2. The layer-by-layer self-assembly preparation method according to claim 1, characterized in that In step (1), the concentration of the sodium hydroxide aqueous solution is 15 to 25 g / L; the immersion temperature is 55 to 65° C.; and the immersion time is 40 to 80 min.

3. The layer-by-layer self-assembly preparation method according to claim 1, characterized in that In step (2), the concentration of the polyethyleneimine aqueous solution is 0.5-1.5 wt %, the immersion temperature is 10-40° C., and the immersion time is 5-20 min.

4. The layer-by-layer self-assembly preparation method according to claim 1, characterized in that In step (3), the hectorite concentration of the composite aqueous solution is 1.5-2.5 wt %; the chitosan concentration of the composite aqueous solution is 0.05-0.2 wt %; the immersion temperature is 10-40° C.; and the immersion time is 5-20 min.

5. The layer-by-layer self-assembly preparation method according to claim 1, characterized in that: In step (4), the concentration of the polyethyleneimine aqueous solution is 4 to 10 wt %; the immersion temperature is 10 to 40° C.; and the immersion time is 5 to 20 minutes.

6. The layer-by-layer self-assembly preparation method according to claim 1, characterized in that: In step (5), the concentration of the phytic acid aqueous solution is 4 to 10 wt %; the immersion temperature is 10 to 40° C.; and the immersion time is 5 to 20 minutes.

7. The layer-by-layer self-assembly preparation method according to claim 1, characterized in that: In step (6), the pH value of the citric acid / sodium citrate buffer solution is 3.8-4.2, the immersion temperature is 10-40° C., and the immersion time is 3-10 min.

8. The layer-by-layer self-assembly preparation method according to claim 1, characterized in that: In step (6), the pre-drying temperature is 60 to 80 minutes; the pre-drying time is 1 to 5 minutes; the curing temperature is 130 to 155° C.; and the curing time is 1 to 5 minutes.

9. The organic-inorganic hybrid flame-retardant coated polyester fabric prepared according to any one of claims 1 to 8.

10. Use of the organic-inorganic hybrid flame-retardant coated polyester fabric according to claim 9 in the field of textiles.

Images