Flame retardant, durable flame resistant nylon fabric, method of making and use thereof

Abstract

The application provides a flame retardant, a durable flame-retardant nylon fabric, a preparation method and application thereof, and belongs to the technical field of flame retardants. The flame retardant comprises the following components: alkyl phosphate, sulfur / nitrogen-based compound, crosslinking agent, catalyst and solvent; the alkyl phosphate is aliphatic or aromatic containing 1-18 carbon atoms; the ester group in the alkyl phosphate is a mono- or poly-ester containing 1-12 carbon atoms; the sulfur / nitrogen-based compound is a compound containing sulfonic acid group and amino group; the crosslinking agent is a polycarboxylic acid; and the catalyst is hypophosphite or hypophosphorous acid salt. The durable flame-retardant nylon fabric prepared by the application has a limiting oxygen index of 33.2-34.9%, reaches the standard of difficult ignition, still has certain flame retardancy after 10 times of washing, has excellent washing resistance, and the melt dripping phenomenon is obviously improved.

Description

Technical Field

[0001] This application belongs to the field of flame retardant technology, and more specifically, relates to a flame retardant, a durable flame-retardant nylon fabric, a preparation method thereof, and its application. Background Technology

[0002] Nylon, the world's first synthetic fiber, is a type of polyamide fiber. Its emergence revolutionized textiles, and its synthesis represented a major breakthrough in the synthetic fiber industry. Nylon fabrics possess advantages such as good abrasion resistance, high tensile strength, and processability, and are widely used in transportation, electronics, military textiles, aerospace, and home decoration. However, synthetic fibers are highly flammable and cannot meet the fire safety regulations of relevant textile industries. Furthermore, the molten droplets produced during combustion can ignite other flammable materials, causing secondary fires with serious consequences. Therefore, improving the flame-retardant properties of nylon fabrics and suppressing their dripping phenomenon is of great significance.

[0003] Flame retardants can be mainly classified into halogenated flame retardants, silicone flame retardants, phosphorus flame retardants, nitrogen flame retardants, and intumescent flame retardants. Halogenated flame retardants produce toxic substances, which is inconsistent with the concept of green and environmentally friendly development, and their use has been banned. Silicone flame retardants have poor flame retardant effects and can affect the softness of fabrics; they are often used in combination with phosphorus and nitrogen flame retardants. Phosphorus flame retardants are widely used in various fabrics due to their high flame retardancy, but they suffer from poor thermal stability and volatility.

[0004] Currently, the main way to improve phosphorus-based flame retardants is through the synergistic use of nitrogen-phosphorus flame retardants, achieving a phosphorus-nitrogen flame retardant with a synergistic flame-retardant effect. For example, Chinese patent CN103898744A discloses a method for preparing halogen-free flame-retardant non-melting nylon 66 fabric. First, the fabric is pretreated, then it is thoroughly impregnated with a nitrogen-phosphorus flame retardant containing PNF, AS, and HEDP through a conventional impregnation and pressing process. Finally, baking is used to firmly bond the flame retardant to the fabric, thereby achieving the purpose of flame retardancy and preventing dripping. After treatment, the oxygen index of the nylon sample increased from 21.1% to 26.0%. The flame-retardant effect of the nylon 66 fabric in this patent still needs further improvement. Furthermore, most current flame-retardant modified fabrics suffer from poor washability. Summary of the Invention

[0005] The purpose of this application is to provide a flame retardant, a durable flame retardant nylon fabric, a preparation method and its application. The flame retardant modified fabric provided by this application has good flame retardant effect and good water washability.

[0006] To achieve the above objectives, a first aspect of this application provides a flame retardant comprising the following components: alkyl phosphate esters, sulfur / nitrogen compounds, crosslinking agents, catalysts, and solvents;

[0007] The alkyl phosphates are aliphatic or aromatic esters containing 1 to 18 carbon atoms, and the ester group in the alkyl phosphates is a mono- or poly-ester containing 1 to 12 carbon atoms.

[0008] The sulfur / nitrogen compound is a compound that contains both sulfonic acid groups and amino groups;

[0009] The crosslinking agent is a polycarboxylic acid;

[0010] The catalyst is a hypophosphite or hypophosphite.

[0011] Further, the alkyl phosphate esters are one or more selected from the following: diethyl dodecyl phosphate, didecyl naphthyl phosphate, diheptyl cyclohexyl phosphate, diethyl phosphate, diethyl propyl phosphate, dimethyl methylphosphonate, diethyl methyl phosphate, dimethyl phosphate, and diethyl phosphate.

[0012] Further, the sulfur / nitrogen compound is one or more of guanidine aminosulfonate, ammonium aminosulfonate, aminosulfonic acid, thiourea, ammonium sulfate, and sulfonamide.

[0013] Further, the crosslinking agent is one or more of citric acid, 1,2,3,4-butanetetracarboxylic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid.

[0014] Furthermore, the catalyst is one or more of sodium hypophosphite, sodium hypophosphite, and aluminum hypophosphite.

[0015] Further, the molar concentration of the alkyl phosphate ester is 0.8–1.5 mol / L, the molar concentration of the sulfur / nitrogen compound is 0.6–1.0 mol / L, the molar concentration of the crosslinking agent is 0.6–1.0 mol / L, and the mass concentration of the catalyst is 1%–6%. If the concentrations of the phosphate ester and the sulfur / nitrogen compound are too low, the flame retardant properties of the fabric will be affected; if the concentrations are too high, the fabric will stiffen, affecting its mechanical properties. The molar ratio of the phosphate ester to the sulfur / nitrogen compound needs to be controlled at approximately 3:2 to ensure sufficient phosphate groups to crosslink with the crosslinking agent after the phosphate ester hydrolysis.

[0016] A second aspect of this application provides a method for preparing a flame retardant, comprising the following steps: dissolving alkyl phosphates and sulfur / nitrogen compounds in deionized water; after complete dissolution, adding a crosslinking agent and a catalyst; and stirring until homogeneous to form a mixture system.

[0017] A third aspect of this application provides the use of a flame retardant in the preparation of flame-retardant fabrics.

[0018] In a fourth aspect of this application, a durable flame-retardant nylon fabric is provided, which is prepared by the following method: pretreating the nylon fabric; impregnating the pretreated nylon fabric in the flame retardant described above, and then drying and curing it to obtain the durable flame-retardant nylon fabric.

[0019] Furthermore, the process of impregnating the pretreated nylon fabric in the flame retardant described above adopts a step-by-step impregnation method: first, the pretreated nylon fabric is impregnated in a system containing sulfur / nitrogen-based compounds, crosslinking agents, and catalysts, and then dried; then, the nylon fabric that has undergone one impregnation treatment is impregnated in a system containing alkyl phosphate esters, and then cured.

[0020] Furthermore, the drying process is performed at 80°C for 10–20 minutes, and the curing process is performed at 180°C for 5–10 minutes.

[0021] Furthermore, the immersion treatment time is 2 to 4 hours.

[0022] Further, the pretreatment involves immersing the nylon fabric in a 1-5 wt% sodium hydroxide or sodium carbonate solution for 20-24 hours, then washing it with water until it is nearly neutral, and drying it at 70-80°C.

[0023] Furthermore, the nylon fabric is polyamide 6 or polyamide 66.

[0024] Compared with the prior art, this application has the following technical effects:

[0025] This application discloses a novel phosphorus / nitrogen / sulfur flame retardant prepared by in-situ polymerization using alkyl phosphate esters and sulfur / nitrogen compounds as raw materials, polycarboxylic acids as crosslinking agents, and hypophosphite or hypophosphite as catalysts. After hydrolysis of the phosphate ester groups, phosphate groups are formed, which crosslink with amino groups and carboxyl groups in the crosslinking agent under the action of the catalyst, forming a macromolecular chain network structure on the surface of nylon fibers. At the same time, the crosslinking agent can also crosslink with the amino groups at the ends of the nylon fiber molecular chains, which is beneficial to improving the bonding force between the flame retardant and the nylon fibers, thereby providing certain water-washing resistance.

[0026] The flame retardant prepared in this application is used to impregnate nylon fabrics. During combustion, the phosphate groups, sulfonic acid groups, and amino groups in the flame retardant decompose upon heating, producing a non-volatile phosphate layer that covers the fabric surface, isolating oxygen and heat transfer, thus acting as a shield and achieving a condensed-phase flame retardant effect. Simultaneously, the amino groups decompose upon heating, producing a large amount of non-flammable gas, reducing the oxygen concentration and hindering the fabric's combustion, thus achieving a gas-phase flame retardant effect. The sulfonic acid groups decompose upon heating, producing sulfur dioxide, which captures active free radicals, inhibits the combustion chain reaction, and generates non-flammable gas, thereby diluting oxygen and flammable gas to exert a flame retardant effect, primarily functioning as a gas-phase flame retardant mechanism.

[0027] The flame retardant prepared in this application mainly achieves the flame retardant effect on nylon fabric through the synergistic action of condensed phase flame retardancy and gas phase flame retardancy. The limiting oxygen index of the prepared durable flame retardant nylon fabric is 33.2-34.9%, which meets the flame retardant standard. It still has a certain flame retardancy after 10 washes and has excellent water wash resistance. The melting and dripping phenomenon is significantly improved.

[0028] The flame retardant and durable flame-retardant nylon fabric of this application have simple preparation processes and can be mass-produced. Detailed Implementation

[0029] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0031] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0032] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a well-known unit of mass in the biochemical field, such as μg, mg, g, or kg.

[0033] Example 1

[0034] Example 1 of this application provides a flame retardant, a flame retardant nylon fabric, and a method for preparing the same, including the following steps:

[0035] (1) Pretreatment of Nylon 6 fabric

[0036] Prepare a 4wt% NaOH solution, immerse the nylon 6 fabric in the solution for 24 hours, then rinse it several times with deionized water until the nylon 6 fabric is nearly neutral, and dry it at 80℃ for later use.

[0037] (2) Preparation of flame retardants

[0038] Dissolve 6.09 g of thiourea in 100 mL of deionized water and stir until completely dissolved. The molar concentration of thiourea is 0.80 mol / L.

[0039] (3) Preparation of durable flame-retardant nylon 6 fabric

[0040] The nylon 6 fabric pretreated in step (1) was immersed in the solution in step (2) for 3 hours; the nylon fabric after immersion was dried and cured by baking at 80°C for 15 minutes and curing at 180°C for 5 minutes.

[0041] Example 2

[0042] Example 2 of this application provides a flame retardant, a flame retardant nylon fabric, and a method for preparing the same, including the following steps:

[0043] (1) Pretreatment of Nylon 6 fabric

[0044] Prepare a 4wt% NaOH solution, immerse the nylon 6 fabric in the solution for 24 hours, then rinse it several times with deionized water until the nylon 6 fabric is nearly neutral, and dry it at 80℃ for later use.

[0045] (2) Preparation of flame retardants

[0046] Add 14 mL of dimethyl methylphosphonate to 86 mL of deionized water and stir until homogeneous. The molar concentration of dimethyl methylphosphonate is 1.29 mol / L.

[0047] (3) Preparation of durable flame-retardant nylon 6 fabric

[0048] The nylon 6 fabric pretreated in step (1) was immersed in the solution in step (2) for 3 hours; the nylon fabric after immersion was dried and cured by baking at 80°C for 15 minutes and curing at 180°C for 5 minutes.

[0049] Example 3

[0050] Example 3 of this application provides a flame retardant, a flame retardant nylon fabric, and a method for preparing the same, including the following steps:

[0051] (1) Pretreatment of Nylon 6 fabric

[0052] Prepare a 4wt% NaOH solution, immerse the nylon 6 fabric in the solution for 24 hours, then rinse it several times with deionized water until the nylon 6 fabric is nearly neutral, and dry it at 80℃ for later use.

[0053] (2) Preparation of flame retardants

[0054] Add 6.09 g of thiourea and 14 mL of dimethyl methylphosphonate to 86 mL of deionized water and stir until completely dissolved. The molar concentration of thiourea is 0.80 mol / L and the molar concentration of dimethyl methylphosphonate is 1.29 mol / L.

[0055] (3) Preparation of durable flame-retardant nylon 6 fabric

[0056] The nylon 6 fabric pretreated in step (1) was immersed in the solution in step (2) for 3 hours; the nylon fabric after immersion was dried and cured by baking at 80°C for 15 minutes and curing at 180°C for 5 minutes.

[0057] Example 4

[0058] Example 4 of this application provides a flame retardant, a durable flame-retardant nylon fabric, and a method for preparing the same, including the following steps:

[0059] (1) Pretreatment of Nylon 6 fabric

[0060] Prepare a 4wt% NaOH solution, immerse the nylon 6 fabric in the solution for 24 hours, then rinse it several times with deionized water until the nylon 6 fabric is nearly neutral, and dry it at 80℃ for later use.

[0061] (2) Preparation of flame retardants

[0062] 6.09 g of thiourea and 14 mL of dimethyl methylphosphonate were dissolved in 86 mL of deionized water. After complete dissolution, 2-phosphonobutane-1,2,4-tricarboxylic acid and sodium hypophosphite were added and stirred until homogeneous to form a mixture system. In this system, the molar concentration of thiourea was 0.80 mol / L, the molar concentration of dimethyl methylphosphonate was 1.29 mol / L, the molar concentration of 2-phosphonobutane-1,2,4-tricarboxylic acid was 0.80 mol / L, and the mass concentration of sodium hypophosphite was 5%.

[0063] (3) Preparation of durable flame-retardant nylon 6 fabric

[0064] The nylon 6 fabric pretreated in step (1) was immersed in the phosphorus / nitrogen / sulfur flame retardant solution in step (2) for 3 hours; the nylon fabric after immersion was dried and cured by baking at 80°C for 15 minutes and curing at 180°C for 5 minutes.

[0065] Example 5

[0066] Embodiment 5 of this application provides a flame retardant, a durable flame-retardant nylon fabric, and a method for preparing the same, including the following steps:

[0067] (1) Pretreatment of Nylon 6 fabric

[0068] Prepare a 4wt% NaOH solution, immerse the nylon 6 fabric in the solution for 24 hours, then rinse it repeatedly with deionized water until the nylon fabric is nearly neutral, and dry it at 80℃ for later use.

[0069] (2) Preparation of flame retardants

[0070] 6.09 g of thiourea and 14 mL of dimethyl methylphosphonate were added to a mixed solvent containing 43 mL of deionized water and 43 mL of ethanol. After complete dissolution, 2-phosphonobutane-1,2,4-tricarboxylic acid and sodium hypophosphite were added and stirred until homogeneous to form a mixture system. In this system, the molar concentration of thiourea was 0.80 mol / L, the molar concentration of dimethyl methylphosphonate was 1.29 mol / L, the molar concentration of 2-phosphonobutane-1,2,4-tricarboxylic acid was 0.80 mol / L, and the mass concentration of sodium hypophosphite was 5%.

[0071] (3) Preparation of durable flame-retardant nylon 6 fabric

[0072] The nylon 6 fabric pretreated in step (1) was immersed in the phosphorus / nitrogen / sulfur flame retardant solution in step (2) for 3 hours; the nylon 6 fabric after immersion was dried and cured by baking at 80°C for 15 minutes and curing at 180°C for 10 minutes.

[0073] Example 6

[0074] Embodiment 6 of this application provides a flame retardant, a durable flame-retardant nylon fabric, and a method for preparing the same, including the following steps:

[0075] (1) Pretreatment of Nylon 6 fabric

[0076] Prepare a 4wt% NaOH solution, immerse the nylon 6 fabric in the solution for 24 hours, then rinse it several times with deionized water until the nylon 6 fabric is nearly neutral, and dry it at 80℃ for later use.

[0077] (2) Preparation of flame retardants

[0078] 6.09 g of thiourea was dissolved in 100 mL of deionized water and heated until completely dissolved. Then, 2-phosphonobutane-1,2,4-tricarboxylic acid and sodium hypophosphite were added and stirred until homogeneous to form mixture system 1. 14 mL of dimethyl methylphosphonate was added to 86 mL of anhydrous ethanol and stirred until homogeneous to form system 2. In system 1, the molar concentration of thiourea was 0.80 mol / L, the molar concentration of 2-phosphonobutane-1,2,4-tricarboxylic acid was 0.80 mol / L, and the mass concentration of sodium hypophosphite was 5%. In system 2, the molar concentration of dimethyl methylphosphonate was 1.29 mol / L.

[0079] (3) Preparation of durable flame-retardant nylon 6 fabric

[0080] The nylon 6 fabric pretreated in step (1) was immersed in system 1 for 2 hours, then dried at 80°C for 15 minutes, then immersed in system 2 for 10 minutes, and cured at 180°C for 5 minutes to obtain durable flame retardant nylon 6 fabric.

[0081] The flame-retardant fabrics prepared in Examples 1-6 of this application were tested for limiting oxygen index (LOI:%), washability, and melt dripping properties. The results are shown in Table 1 below. The test conditions were as follows:

[0082] Limiting oxygen index test: According to the standard GB / T5454 1997 "Determination of Burning Performance of Textiles by Oxygen Index Method", it is a test method in which the sample is placed under vertical test conditions and the lowest oxygen concentration (also known as the limiting oxygen index) that just sustains combustion in a mixed oxygen and nitrogen flow is measured. The sample is clamped in a sample holder and placed vertically in a combustion cylinder. The upper part of the sample is ignited in an upward flow of oxygen, and its combustion characteristics are observed. The afterburning time (not exceeding 2 minutes) or destruction length (not exceeding 40 mm) is compared with the specified limit value. By testing a series of samples in different oxygen concentrations, the lowest oxygen concentration value expressed as the percentage of oxygen that sustains combustion can be measured.

[0083] Washability test: A magnetic stirrer and a beaker were used to conduct the washability test. 500ml of water was added to a 500ml beaker. The prepared flame-retardant cotton fabric was cut into 5cm x 12cm pieces and placed in the beaker for stirring and washing. The magnetic stirrer speed was set to 600 rpm, and each wash lasted 10 minutes.

[0084] Melting drop performance test: The vertical burning method is used. The fabric is ignited with a 4cm flame for 3 seconds. After the flame is removed, the fabric is observed to see if any molten droplets fall off until the burning ends. The results are expressed in words.

[0085] Table 1

[0086]

[0087]

[0088] Based on the test results in Table 1 above, it can be seen that Examples 1 and 2 only added one component to the flame retardant system, while Example 3 combined different components. Compared with Examples 1 and 2, the flame retardancy of Example 3 was significantly improved, indicating that the components can exert a synergistic flame retardant effect. The LOI of the flame-retardant nylon fabrics prepared in Examples 3 to 6 was much higher after impregnation than before impregnation, at 32.9%, 33.2%, 33.8%, and 34.9% respectively, all meeting the flame-retardant standard (flammable: LOI < 20%; combustible: LOI between 20% and 27%; flame-retardant: LOI < 20%). The LOI (OI) is between 27% and 35%; non-flammable: LOI > 35%, indicating that the flame-retardant fabrics prepared in the embodiments of this application have excellent flame-retardant properties. After 10 washes, the LOI values ​​of Examples 4 and 5 are still between 27% and 35%, meeting the flame-retardant standard and exhibiting excellent washability. However, the LOI of Example 3 is 21.4%, indicating that the flame-retardant nylon fabric without crosslinking agent and catalyst does not have washability. The LOI of Example 6 is 26.1%, which is significantly lower than before washing, but still 4.9% higher than the pure sample, and still has a certain degree of washability. No melting drip phenomenon was observed after immersion and washing in Examples 4 to 6, showing a significant improvement compared to before immersion.

[0089] The preparation method of the nylon fabric in Example 6 of this application differs from that in Examples 4 and 5. Example 6 uses stepwise impregnation, while Examples 4 and 5 use one-step impregnation. However, Example 6 shows the best limiting oxygen index test results because in the one-step impregnation method, when alkyl phosphate esters are added to the solution, the phosphate ester groups undergo hydrolysis to form phosphate groups, which are not easily reacted with the amino groups in sulfur / nitrogen compounds to form amides. In contrast, the stepwise impregnation method in Example 6 avoids the hydrolysis of phosphate ester groups. Under alkaline and high-temperature conditions, the ester groups react with the amino groups to form amides, which are compatible with nylon fabrics, which also have an amide structure. Under high-temperature conditions, the nylon fibers expand and increase their specific surface area, which is more conducive to the adsorption of flame retardants on nylon fabrics. Therefore, the durable flame-retardant nylon fabric prepared by stepwise impregnation in Example 6 has a better flame-retardant effect than that in Examples 4 and 5. However, after 10 washes, the LOI values ​​of Examples 4 and 5 were higher than those of Example 6. This is because in Examples 4 and 5, the phosphate ester groups were hydrolyzed to form phosphate groups, which then crosslinked with the amino groups and the carboxyl groups in the crosslinking agent under the action of a catalyst, forming a macromolecular chain network structure on the surface of the nylon fiber. At the same time, the crosslinking agent can also crosslink with the amino groups at the ends of the nylon fiber molecular chains, which is beneficial to improving the bonding force between the flame retardant and the nylon fiber, thus giving it a certain degree of water wash resistance.

[0090] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A durable flame-retardant nylon fabric, characterized in that, Pre-treat the nylon fabric; The pretreated nylon fabric is impregnated with a flame retardant and then dried and cured to obtain a durable flame-retardant nylon fabric. The pretreatment involves immersing the nylon fabric in a 1-5 wt% sodium hydroxide or sodium carbonate solution for 20-24 hours, then washing it with water until it is nearly neutral and then drying it. The nylon fabric is polyamide 6 or polyamide 66; Flame retardants include the following components: alkyl phosphates, sulfur / nitrogen compounds, crosslinking agents, catalysts, and solvents; The alkyl phosphate ester is dimethyl methylphosphonate; The sulfur / nitrogen compound is thiourea; The crosslinking agent is 2-phosphonobutane-1,2,4-tricarboxylic acid; The catalyst is a hypophosphite or hypophosphite; After the phosphate ester group is hydrolyzed to form a phosphate group, it crosslinks with the amino group and the carboxyl group in the crosslinking agent under the action of a catalyst, forming a macromolecular chain network structure on the surface of the nylon fiber. At the same time, the crosslinking agent can also crosslink with the amino group at the end of the nylon fiber molecular chain.

2. The durable flame-retardant nylon fabric as described in claim 1, characterized in that, The catalyst is one or more of sodium hypophosphite, sodium hypophosphite, and aluminum hypophosphite.

3. The durable flame-retardant nylon fabric as described in claim 1, characterized in that, The molar concentration of the alkyl phosphate is 0.8~1.5 mol / L, the molar concentration of the sulfur / nitrogen compound is 0.6~1.0 mol / L, the molar concentration of the crosslinking agent is 0.6~1.0 mol / L, and the mass concentration of the catalyst is 1%~6%.

4. The durable flame-retardant nylon fabric as described in claim 1, characterized in that, Includes the following steps: Alkyl phosphates and sulfur / nitrogen compounds are dissolved in deionized water. After complete dissolution, crosslinking agents and catalysts are added and stirred until homogeneous to form a mixture system.

5. The durable flame-retardant nylon fabric as described in claim 1, characterized in that, The drying process is performed at 80°C for 10-20 minutes, and the curing process is performed at 180°C for 5-10 minutes.

6. The durable flame-retardant nylon fabric as described in claim 1, characterized in that, The immersion treatment time is 2-4 hours.

7. The durable flame-retardant nylon fabric as described in claim 1, characterized in that, The drying process is carried out at 70~80℃.

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