A method for preparing durable flame-retardant nylon 6 fabric based on reactive phosphorus-sulfur flame retardant

Abstract

The present invention belongs to the technical field of flame-retardant fabrics, and relates to a method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant, specifically: after adding nylon 6 fabric to a finishing solution containing a reactive phosphorus-sulfur flame retardant, a free radical initiator and a solvent a, reacting at 75-85°C for 6-8h to obtain a durable flame-retardant nylon 6 fabric; the limiting oxygen index of the durable flame-retardant nylon 6 fabric is higher than 29.3%, the damaged length is lower than 10.5cm, no molten droplets are generated, and after 40 washes, it can still pass the vertical burning test, the damaged length is lower than 14.4cm, and no molten droplets are generated. The flame-retardant nylon 6 fabric prepared by the method of the present invention has good flame retardant effect and excellent water-washing resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of flame-retardant fabrics, and in particular relates to a method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant. Background Art

[0002] Nylon 6 fiber has excellent mechanical strength and wear resistance, low density, good moisture absorption and other characteristics, and is widely used in clothing, home textiles and industrial fields. However, the limiting oxygen index of nylon 6 fiber is about 20%, which is a flammable fiber. Moreover, due to the thinness and large specific surface area of ​​fiber products, the burning speed is fast and accompanied by serious dripping behavior, and the fire caused by ignition or combustion is seriously endangering the safety of life and property. It is of great significance to improve the flame retardant and dripping resistance of nylon 6 fabrics.

[0003] 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is a highly efficient and environmentally friendly phosphorus-based flame retardant. Due to its high thermal stability and excellent flame retardant properties, it is widely used in a variety of polymer materials. However, how to improve the adhesion of DOPO-based flame retardants on fabrics and improve the durability of flame-retardant fabrics is a current difficulty.

[0004] Patent application CN117364479A discloses a flame-retardant polyamide fabric and a preparation method thereof, wherein DOPO and 1,3-dihydroxyacetone are mixed, heated and melted to react, 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 prepare a flame-retardant finishing liquid, and a flame-retardant polyamide fabric is prepared, which can withstand 25 washes. However, the flame retardant still only relies on weak interactions such as van der Waals forces and hydrogen bonds to bind to the polyamide fabric, and cannot produce covalent bonds and other bonds. The washability of the flame-retardant nylon fabric still needs to be further improved.

[0005] Patent application CN116516679A discloses a durable flame retardant and drip-proof coating nylon 6 fabric and a preparation method thereof, wherein polyacrylamide, terephthalaldehyde and DOPO are dissolved in a mixed solution of ethanol and water for reaction to obtain modified polyacrylamide; the modified polyacrylamide is dissolved in a solvent, and the nylon 6 fabric is immersed in the solvent, and the durable flame retardant and drip-proof coating nylon 6 fabric is prepared by a padding-baking process. However, polyacrylamide and modified polyacrylamide have a high viscosity after being dissolved, and the viscous liquid weakens its fluidity, making it difficult to apply to textiles, and a lower amount of modified polyacrylamide cannot provide good flame retardant properties and water washability.

[0006] Patent application CN116217623A discloses a bio-based flame retardant and its preparation method and application. The bio-based flame retardant is synthesized by using DOPO and allylthiourea, and then dialdehyde is used as a cross-linking agent to improve the fixation of the bio-based flame retardant on polyamide 56 fabric, which can withstand 25 washes. However, the active amino groups on polyamide 56 fabric are limited, and the content of bio-based flame retardant that can be grafted is limited. The water washability of flame-retardant polyamide fabric still needs to be further improved.

[0007] Therefore, it is necessary to develop a method for preparing a durable flame retardant nylon 6 fabric to improve the flame retardancy and durability of the nylon 6 fabric. Summary of the invention

[0008] The purpose of the present invention is to solve the problems existing in the prior art and provide a method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant, comprising adding nylon 6 fabric to a finishing solution containing a reactive phosphorus-sulfur flame retardant, a free radical initiator and a solvent a (a mixed solution of N,N-dimethylformamide and water, wherein the volume proportion of water is 30-40%), and reacting at 75-85° C. (a higher reaction temperature helps to promote the polymerization reaction, but too high a reaction temperature is wasteful) for 6-8 hours to obtain a durable flame-retardant nylon 6 fabric, wherein the reactive phosphorus-sulfur flame retardant has the following structural formula:

[0011] ;

[0012] On the one hand, under the initiation of free radical initiators, the vinyl double bonds of the reactive phosphorus-sulfur flame retardant can undergo polymerization reaction. Both ends of the reactive phosphorus-sulfur flame retardant contain vinyl groups, so the polymerization reaction efficiency is high and the polymer tends to a network structure, thereby polymerizing on the surface of nylon 6 fabric; on the other hand, the unreacted vinyl groups in the polymerization product can undergo nucleophilic addition reaction with the amino groups on the surface of nylon 6 fabric, and are combined through covalent bonds, thereby grafting the polymer onto the nylon 6 fabric, thereby providing durable flame retardant properties.

[0013] As the preferred technical solution:

[0014] In the method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant as described above, the free radical initiator is ammonium persulfate, which initiates the free radicals of the reactive phosphorus-sulfur flame retardant to undergo self-polymerization and copolymerize with the free radicals of the nylon 6 fiber.

[0015] As described above, in the method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant, the concentration of the reactive phosphorus-sulfur flame retardant in the finishing liquid is 40-70 g / L. The higher the concentration of the flame retardant, the higher the flame retardant effect, but too high a concentration is wasteful. The concentration of the free radical initiator is 10-20 g / L.

[0016] In the method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant as described above, the pH value of the finishing liquid is 4-5, and acetic acid is used for adjustment. The weakly acidic condition is conducive to the polymerization reaction of vinyl.

[0017] In the method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant as described above, the mass ratio of the nylon 6 fabric to the finishing liquid is 1:30-40.

[0018] The method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant as described above, the preparation steps of the reactive phosphorus-sulfur flame retardant are as follows:

[0019] (a) mixing p-hydroxybenzaldehyde, 3-bromopropylene, an acid absorber (e.g., potassium carbonate; p-hydroxybenzaldehyde and 3-bromopropylene react to generate hydrogen bromide; adding potassium carbonate as an acid absorber helps to promote the reaction) and solvent b (e.g., acetone) and reacting the mixture, cooling, filtering and removing precipitates;

[0020] (b) adding thiourea to the system of step (a), continuing the reaction, and removing the solvent by filtering and distilling under reduced pressure to obtain an intermediate product;

[0021] (c) The intermediate product, DOPO (the PH bond of DOPO is relatively active and can undergo a Pudovik addition reaction with the Schiff base structure of the intermediate product) and solvent c (such as tetrahydrofuran) are mixed and reacted to obtain a reactive phosphorus-sulfur flame retardant.

[0022] The method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant as described above, in step (a), the molar ratio of p-hydroxybenzaldehyde to 3-bromopropylene is 1:1-1.2, theoretically, one mole of hydroxyl groups of p-hydroxybenzaldehyde and one mole of bromine active groups of 3-bromopropylene undergo nucleophilic substitution reaction, and a slight excess of 3-bromopropylene helps to promote the complete reaction, the molar ratio of the acid absorber to p-hydroxybenzaldehyde is 1:1-1.1, the mass ratio of p-hydroxybenzaldehyde to solvent b is 1:30-40, the reaction temperature is 60-65°C, the reaction time is 10-12h, and the reaction is carried out in a reflux manner.

[0023] In the method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant as described above, the molar ratio of p-hydroxybenzaldehyde in step (a) to thiourea in step (b) is 2:1-1.2. Theoretically, each mole of thiourea contains two moles of amino groups, which can react with two moles of aldehyde groups of p-hydroxybenzaldehyde to produce a Schiff base reaction. A slight excess of thiourea helps to promote the complete reaction. In step (b), the reaction is continued for 5-7 hours.

[0024] In the method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant as described above, the molar ratio of p-hydroxybenzaldehyde in step (a) to DOPO in step (c) is 1:1-1.2, and in step (c), the reaction temperature is 65-70°C, the reaction time is 4-6h, and the reaction is carried out in a reflux manner.

[0025] A method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant as described in any of the above items, wherein the durable flame retardant nylon 6 fabric has a limiting oxygen index higher than 29.3%, a damaged length lower than 10.5 cm, no molten droplets are generated, and can still pass a vertical burning test after 40 washes, with a damaged length lower than 14.4 cm, no molten droplets are generated, and has good flame retardant properties and water washability.

[0026] Principle of the invention:

[0027] like Figure 1 The schematic diagram of the synthesis route of the reactive phosphorus-sulfur flame retardant shown in the figure shows that the hydroxyl group of p-hydroxybenzaldehyde and the active bromine group of 3-bromopropylene undergo a nucleophilic substitution reaction, the aldehyde group of p-hydroxybenzaldehyde and the amino group of thiourea can undergo a Schiff base reaction, and the PH bond of DOPO is relatively active and can undergo a Pudovik addition reaction with the Schiff base structure of the intermediate product to obtain a reactive phosphorus-sulfur flame retardant;

[0028] Under the initiation of ammonium persulfate, the vinyl double bonds of the reactive phosphorus-sulfur flame retardant can undergo polymerization reaction. Both ends of the reactive phosphorus-sulfur flame retardant contain vinyl groups, so the polymerization reaction efficiency is high, and the polymer tends to have a network structure, thereby polymerizing on the surface of nylon 6 fabric; on the other hand, the unreacted vinyl in the polymerization product can undergo nucleophilic addition reaction with the amino group on the surface of nylon 6 fabric, and the polymer is grafted onto the nylon 6 fabric through covalent bond, thereby providing durable flame retardant performance;

[0029] The polymer is rich in phosphorus-containing groups, sulfur-containing groups and nitrogen-containing groups. All three improve the flame retardant properties of nylon 6 fabric through the gas phase mechanism. Phosphorus-containing free radicals and sulfur-containing free radicals are generated during the combustion process, which can capture the combustible free radicals in the combustion area and play a quenching role. The released non-flammable nitrogen-containing substances such as ammonia play a diluting role, thereby improving the flame retardant properties of nylon 6 fabric through a synergistic flame retardant effect.

[0030] Beneficial effects:

[0031] (1) The reactive phosphorus-sulfur flame retardant synthesized by the present invention improves the flame retardant properties of nylon 6 fabric through the synergistic flame retardant effect of phosphorus-containing groups, sulfur-containing groups and nitrogen-containing groups, and has high flame retardant efficiency;

[0032] (2) The method for preparing durable flame-retardant nylon 6 fabric based on reactive phosphorus-sulfur flame retardant of the present invention utilizes the polymerization reaction of the flame retardant itself and covalent bonding with the amino group of nylon 6 fabric, thereby grafting the flame retardant film onto the nylon 6 fabric, thereby improving the water washability of the flame-retardant nylon 6 fabric. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The schematic diagram of the synthesis route of the reactive phosphorus-sulfur flame retardant of the present invention;

[0034] Figure 2 This is the carbon nuclear magnetic resonance spectrum of the reactive phosphorus-sulfur flame retardant prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0035] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0036] Testing methods for relevant performance indicators:

[0037] Limiting oxygen index: Tested in accordance with GB / T 5454-1997 "Oxygen Index Method for Textile Combustion Performance Test".

[0038] Damage length and the presence of molten droplets: Determine the damage length, smoldering and afterflaming time in the vertical direction of the combustion performance of textiles according to GB / T 5455-2014. Observe the presence of molten droplets during the test.

[0039] Damaged length and presence of droplets after 40 washes: First wash the fabric 40 times with water according to AATCC 61-2013 "Accelerated test for color fastness to household and commercial washing" standard, and then test the damaged length of the fabric with reference to GB / T 5455-2014 "Determination of vertical direction damage length, smoldering and afterflaming time of textile combustion performance" standard, and observe whether there are droplets during the test.

[0040] The structural formula of the reactive phosphorus-sulfur flame retardant prepared in the following examples is as follows:

[0041] .

[0042] Example 1

[0043] A method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant, the specific steps are as follows:

[0044] (1) Raw material preparation:

[0045] Nylon 6 fabric: Limiting oxygen index is 20.1%, and the damaged length is 30cm;

[0046] Free radical initiator: ammonium persulfate;

[0047] p-Hydroxybenzaldehyde;

[0048] 3-bromopropylene;

[0049] Acid absorbent: potassium carbonate;

[0050] Thiourea;

[0051] DOPO;

[0052] Solvent a: a mixed solution of N,N-dimethylformamide and water, wherein the volume proportion of water is 30%;

[0053] Solvent b: acetone;

[0054] Solvent c: tetrahydrofuran;

[0055] acetic acid;

[0056] (2) Preparation of reactive phosphorus-sulfur flame retardant:

[0057] (2.1) After mixing p-hydroxybenzaldehyde, 3-bromopropylene, an acid absorbent and solvent b, react at 60°C for 12 h by reflux, cool down and filter to remove the precipitate;

[0058] Wherein, the molar ratio of p-hydroxybenzaldehyde to 3-bromopropylene is 1:1, the molar ratio of the acid scavenger to p-hydroxybenzaldehyde is 1:1, and the mass ratio of p-hydroxybenzaldehyde to solvent b is 1:30;

[0059] (2.2) Add thiourea to the system of step (2.1) and continue the reaction for 7 hours. Remove the solvent by filtering and distilling under reduced pressure to obtain an intermediate product.

[0060] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to thiourea in step (2.2) is 2:1;

[0061] (2.3) After mixing the intermediate product, DOPO and solvent c, the mixture is reacted at 65°C for 6 hours by reflux to obtain a reactive phosphorus-sulfur flame retardant;

[0062] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to DOPO in step (2.3) is 1:1;

[0063] The carbon NMR spectrum of the prepared reactive phosphorus-sulfur flame retardant is as follows: Figure 2 As shown in the figure, it can be seen that the chemical shift at 182.5ppm in the NMR carbon spectrum of the reactive phosphorus-sulfur flame retardant is caused by the carbon element in the thiourea structure C=S, the chemical shifts at 158.3 and 114.3ppm are caused by the carbon element in the benzene ring of the p-hydroxybenzaldehyde structure, the chemical shift at 55.4ppm is caused by the carbon element in the side chain of the p-hydroxybenzaldehyde structure, the chemical shifts at 150.9, 133.2, 128.0, 122.3, ppm are caused by the carbon element in the p-DOPO structure, and the chemical shifts at 116.9 and 72.5ppm are caused by the carbon element in the p-propylene structure. The above results show that the reactive phosphorus-sulfur flame retardant was successfully synthesized;

[0064] (3) Flame retardant finishing:

[0065] After adding nylon 6 fabric into a finishing solution composed of a reactive phosphorus-sulfur flame retardant, a free radical initiator and a solvent a, acetic acid is used to adjust the pH of the system to 4, and the reaction is carried out at 75°C for 8 hours to obtain a durable flame-retardant nylon 6 fabric;

[0066] In the finishing liquid, the concentration of the reactive phosphorus-sulfur flame retardant is 40 g / L, the concentration of the free radical initiator is 10 g / L, and the mass ratio of nylon 6 fabric to the finishing liquid is 1:30.

[0067] The final durable flame-retardant nylon 6 fabric has a limiting oxygen index of 29.3%, a damaged length of 10.5 cm, and no molten droplets are produced. After 40 washes, it can still pass the vertical burning test with a damaged length of 14.4 cm and no molten droplets.

[0068] Comparative Example 1

[0069] A method for preparing a flame-retardant nylon 6 fabric is basically the same as that in Example 1, except that: in the finishing liquid of this comparative example, flame retardant a is used to replace the reactive phosphorus-sulfur flame retardant in the original Example 1, and the synthesis step of flame retardant a is basically the same as step (2) in Example 1, except that 3-bromopropylene is not added.

[0070] The final flame-retardant nylon 6 fabric had a limiting oxygen index of 28.5%, a damaged length of 12.1 cm, no molten droplets were produced, and after 40 washes, it could still pass the vertical burning test with a damaged length of 30 cm and molten droplets produced.

[0071] Compared with Example 1, the flame retardant performance of the flame retardant nylon 6 fabric of Comparative Example 1 is reduced, and the water washing resistance is poor. This is because the flame retardant a of Comparative Example 1 has no vinyl double bonds at both ends, cannot be polymerized on the surface of the nylon 6 fabric, and cannot react with the nylon 6 fabric. It is simply deposited on the surface of the nylon 6 fabric. Therefore, the flame retardant nylon 6 fabric of Comparative Example 1 has poor flame retardant performance and water washing resistance.

[0072] Comparative Example 2

[0073] A method for preparing a flame retardant nylon 6 fabric is basically the same as that of Example 1, except that the finishing liquid of this comparative example does not contain a free radical initiator.

[0074] The final flame-retardant nylon 6 fabric had a limiting oxygen index of 28.9%, a damaged length of 11.5 cm, no molten droplets were produced, and after 40 washes, it could still pass the vertical burning test with a damaged length of 30 cm and molten droplets produced.

[0075] Compared with Example 1, the flame retardant properties of the flame retardant nylon 6 fabric in Comparative Example 2 are reduced, and the water washing resistance is reduced. This is because the free radical initiator can initiate the self-polymerization reaction of the free radicals of the reactive phosphorus-sulfur flame retardant and promote the grafting reaction with the nylon 6 fiber, thereby polymerizing on the surface of the nylon 6 fabric. The finishing liquid of Comparative Example 2 does not contain a free radical initiator, so that the reactive phosphorus-sulfur flame retardant cannot be polymerized on the surface of the nylon 6 fabric, and the content of the flame retardant that undergoes a grafting reaction with the nylon 6 fabric is small, and it is mainly deposited on the surface of the nylon 6 fabric by physical means, resulting in the deterioration of the flame retardant properties and water washing resistance of the flame retardant nylon 6 fabric finally obtained.

[0076] Example 2

[0077] A method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant, the specific steps are as follows:

[0078] (1) Raw material preparation:

[0079] Nylon 6 fabric: Limiting oxygen index is 20.1%, and the damaged length is 30cm;

[0080] Free radical initiator: ammonium persulfate;

[0081] p-Hydroxybenzaldehyde;

[0082] 3-bromopropylene;

[0083] Acid absorbent: potassium carbonate;

[0084] Thiourea;

[0085] DOPO;

[0086] Solvent a: a mixed solution of N,N-dimethylformamide and water, wherein the volume proportion of water is 33%;

[0087] Solvent b: acetone;

[0088] Solvent c: tetrahydrofuran;

[0089] acetic acid;

[0090] (2) Preparation of reactive phosphorus-sulfur flame retardant:

[0091] (2.1) After mixing p-hydroxybenzaldehyde, 3-bromopropylene, an acid absorbent and solvent b, the mixture was reacted at 62°C for 11.5 hours by reflux, and the temperature was lowered and filtered to remove the precipitate;

[0092] Wherein, the molar ratio of p-hydroxybenzaldehyde to 3-bromopropylene is 1:1.1, the molar ratio of the acid scavenger to p-hydroxybenzaldehyde is 1:1.1, and the mass ratio of p-hydroxybenzaldehyde to solvent b is 1:32;

[0093] (2.2) Add thiourea to the system of step (2.1) and continue the reaction for 6.5 hours. Remove the solvent by filtration and reduced pressure distillation to obtain an intermediate product.

[0094] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to thiourea in step (2.2) is 2:1.1;

[0095] (2.3) After mixing the intermediate product, DOPO and solvent c, the mixture was reacted at 66°C for 5.5 hours by reflux to obtain a reactive phosphorus-sulfur flame retardant;

[0096] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to DOPO in step (2.3) is 1:1.1;

[0097] (3) Flame retardant finishing:

[0098] After adding nylon 6 fabric into a finishing solution composed of a reactive phosphorus-sulfur flame retardant, a free radical initiator and a solvent a, acetic acid is used to adjust the pH of the system to 4.5, and the reaction is carried out at 78°C for 7.5 hours to obtain a durable flame-retardant nylon 6 fabric;

[0099] In the finishing liquid, the concentration of the reactive phosphorus-sulfur flame retardant is 50 g / L, the concentration of the free radical initiator is 13 g / L, and the mass ratio of nylon 6 fabric to the finishing liquid is 1:35.

[0100] The final durable flame-retardant nylon 6 fabric has a limiting oxygen index of 30.7%, a damaged length of 9.3 cm, and no molten droplets are produced. After 40 washes, it can still pass the vertical burning test with a damaged length of 13.5 cm and no molten droplets.

[0101] Example 3

[0102] A method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant, the specific steps are as follows:

[0103] (1) Raw material preparation:

[0104] Nylon 6 fabric: Limiting oxygen index is 20.1%, and the damaged length is 30cm;

[0105] Free radical initiator: ammonium persulfate;

[0106] p-Hydroxybenzaldehyde;

[0107] 3-bromopropylene;

[0108] Acid absorbent: potassium carbonate;

[0109] Thiourea;

[0110] DOPO;

[0111] Solvent a: a mixed solution of N,N-dimethylformamide and water, wherein the volume proportion of water is 35%;

[0112] Solvent b: acetone;

[0113] Solvent c: tetrahydrofuran;

[0114] acetic acid;

[0115] (2) Preparation of reactive phosphorus-sulfur flame retardant:

[0116] (2.1) After mixing p-hydroxybenzaldehyde, 3-bromopropylene, an acid absorbent and solvent b, react at 64°C for 11 hours by reflux, cool down and filter to remove the precipitate;

[0117] Wherein, the molar ratio of p-hydroxybenzaldehyde to 3-bromopropylene is 1:1.2, the molar ratio of the acid scavenger to p-hydroxybenzaldehyde is 1:1, and the mass ratio of p-hydroxybenzaldehyde to solvent b is 1:35;

[0118] (2.2) Add thiourea to the system of step (2.1) and continue the reaction for 5 h. Remove the solvent by filtering and distilling under reduced pressure to obtain an intermediate product.

[0119] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to thiourea in step (2.2) is 2:1.2;

[0120] (2.3) After mixing the intermediate product, DOPO and solvent c, the mixture was reacted at 67°C for 5 h by reflux to obtain a reactive phosphorus-sulfur flame retardant;

[0121] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to DOPO in step (2.3) is 1:1.2;

[0122] (3) Flame retardant finishing:

[0123] After adding nylon 6 fabric into a finishing solution composed of a reactive phosphorus-sulfur flame retardant, a free radical initiator and a solvent a, acetic acid is used to adjust the pH of the system to 5, and the reaction is carried out at 80°C for 7 hours to obtain a durable flame-retardant nylon 6 fabric;

[0124] In the finishing liquid, the concentration of the reactive phosphorus-sulfur flame retardant is 60 g / L, the concentration of the free radical initiator is 15 g / L, and the mass ratio of nylon 6 fabric to the finishing liquid is 1:40.

[0125] The final durable flame-retardant nylon 6 fabric has a limiting oxygen index of 31.9%, a damaged length of 8.6 cm, and no molten droplets are produced. After 40 washes, it can still pass the vertical burning test with a damaged length of 12.9 cm and no molten droplets.

[0126] Example 4

[0127] A method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant, the specific steps are as follows:

[0128] (1) Raw material preparation:

[0129] Nylon 6 fabric: Limiting oxygen index is 20.1%, and the damaged length is 30cm;

[0130] Free radical initiator: ammonium persulfate;

[0131] p-Hydroxybenzaldehyde;

[0132] 3-bromopropylene;

[0133] Acid absorbent: potassium carbonate;

[0134] Thiourea;

[0135] DOPO;

[0136] Solvent a: a mixed solution of N,N-dimethylformamide and water, wherein the volume proportion of water is 38%;

[0137] Solvent b: acetone;

[0138] Solvent c: tetrahydrofuran;

[0139] acetic acid;

[0140] (2) Preparation of reactive phosphorus-sulfur flame retardant:

[0141] (2.1) After mixing p-hydroxybenzaldehyde, 3-bromopropylene, an acid absorbent and solvent b, the mixture was reacted at 65°C for 10.5 hours by reflux, and the temperature was lowered and filtered to remove the precipitate;

[0142] Wherein, the molar ratio of p-hydroxybenzaldehyde to 3-bromopropylene is 1:1.1, the molar ratio of the acid scavenger to p-hydroxybenzaldehyde is 1:1.1, and the mass ratio of p-hydroxybenzaldehyde to solvent b is 1:37;

[0143] (2.2) Add thiourea to the system of step (2.1) and continue the reaction for 5.5 hours. Remove the solvent by filtration and reduced pressure distillation to obtain an intermediate product.

[0144] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to thiourea in step (2.2) is 2:1.1;

[0145] (2.3) After mixing the intermediate product, DOPO and solvent c, the mixture was reacted at 69°C for 4.5 hours by reflux to obtain a reactive phosphorus-sulfur flame retardant;

[0146] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to DOPO in step (2.3) is 1:1.1;

[0147] (3) Flame retardant finishing:

[0148] After adding nylon 6 fabric into a finishing solution composed of a reactive phosphorus-sulfur flame retardant, a free radical initiator and a solvent a, acetic acid was used to adjust the pH of the system to 4.5, and the reaction was carried out at 82°C for 6.5 hours to obtain a durable flame-retardant nylon 6 fabric;

[0149] In the finishing liquid, the concentration of the reactive phosphorus-sulfur flame retardant is 65 g / L, the concentration of the free radical initiator is 18 g / L, and the mass ratio of nylon 6 fabric to the finishing liquid is 1:35.

[0150] The final durable flame-retardant nylon 6 fabric has a limiting oxygen index of 32.4%, a damaged length of 8.3 cm, and no molten droplets are produced. After 40 washes, it can still pass the vertical burning test with a damaged length of 12.6 cm and no molten droplets.

[0151] Example 5

[0152] A method for preparing a durable flame-retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant, the specific steps are as follows:

[0153] (1) Raw material preparation:

[0154] Nylon 6 fabric: Limiting oxygen index is 20.1%, and the damaged length is 30cm;

[0155] Free radical initiator: ammonium persulfate;

[0156] p-Hydroxybenzaldehyde;

[0157] 3-bromopropylene;

[0158] Acid absorbent: potassium carbonate;

[0159] Thiourea;

[0160] DOPO;

[0161] Solvent a: a mixed solution of N,N-dimethylformamide and water, wherein the volume proportion of water is 40%;

[0162] Solvent b: acetone;

[0163] Solvent c: tetrahydrofuran;

[0164] acetic acid;

[0165] (2) Preparation of reactive phosphorus-sulfur flame retardant:

[0166] (2.1) After mixing p-hydroxybenzaldehyde, 3-bromopropylene, an acid absorbent and solvent b, react at 65°C for 10 h by reflux, cool down and filter to remove the precipitate;

[0167] Wherein, the molar ratio of p-hydroxybenzaldehyde to 3-bromopropylene is 1:1.2, the molar ratio of the acid scavenger to p-hydroxybenzaldehyde is 1:1, and the mass ratio of p-hydroxybenzaldehyde to solvent b is 1:40;

[0168] (2.2) Add thiourea to the system of step (2.1) and continue the reaction for 5 h. Remove the solvent by filtering and distilling under reduced pressure to obtain an intermediate product.

[0169] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to thiourea in step (2.2) is 2:1;

[0170] (2.3) After mixing the intermediate product, DOPO and solvent c, the mixture is reacted at 70°C for 4 hours by reflux to obtain a reactive phosphorus-sulfur flame retardant;

[0171] Wherein, the molar ratio of p-hydroxybenzaldehyde in step (2.1) to DOPO in step (2.3) is 1:1;

[0172] (3) Flame retardant finishing:

[0173] After adding nylon 6 fabric into a finishing solution composed of a reactive phosphorus-sulfur flame retardant, a free radical initiator and a solvent a, acetic acid is used to adjust the pH of the system to 4, and the reaction is carried out at 85°C for 6 hours to obtain a durable flame-retardant nylon 6 fabric;

[0174] In the finishing liquid, the concentration of the reactive phosphorus-sulfur flame retardant is 70 g / L, the concentration of the free radical initiator is 20 g / L, and the mass ratio of nylon 6 fabric to the finishing liquid is 1:30.

[0175] The final durable flame-retardant nylon 6 fabric has a limiting oxygen index of 32.6%, a damaged length of 8 cm, and no molten droplets are produced. After 40 washes, it can still pass the vertical burning test with a damaged length of 12.4 cm and no molten droplets.

Claims

1. A method for preparing durable flame-retardant nylon 6 fabric based on reactive phosphorus-sulfur flame retardant, characterized in that: After adding nylon 6 fabric into a finishing solution containing a reactive phosphorus-sulfur flame retardant, a free radical initiator and a solvent a, the fabric is reacted at 75-85°C for 6-8h to obtain a durable flame-retardant nylon 6 fabric, wherein the reactive phosphorus-sulfur flame retardant has the following structural formula: The free radical initiator is ammonium persulfate, and the solvent a is a mixed solution of N,N-dimethylformamide and water.

2. The method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant according to claim 1, characterized in that: In the finishing liquid, the concentration of the reactive phosphorus-sulfur flame retardant is 40-70 g / L, and the concentration of the free radical initiator is 10-20 g / L.

3. The method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant according to claim 1, characterized in that: The pH value of the finishing solution is 4-5.

4. The method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant according to claim 1, characterized in that: The mass ratio of nylon 6 fabric to finishing liquid is 1:30-40.

5. The method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant according to claim 1, characterized in that: The preparation steps of reactive phosphorus-sulfur flame retardant are as follows: (a) mixing p-hydroxybenzaldehyde, 3-bromopropylene, an acid acceptor and a solvent b and reacting them; wherein the acid acceptor is potassium carbonate and the solvent b is acetone; (b) adding thiourea to the system of step (a) and continuing the reaction to obtain an intermediate product; (c) mixing the intermediate product, DOPO and solvent c and reacting them to obtain a reactive phosphorus-sulfur flame retardant; wherein solvent c is tetrahydrofuran.

6. The method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant according to claim 5, characterized in that: In step (a), the molar ratio of p-hydroxybenzaldehyde to 3-bromopropylene is 1:1-1.2, the molar ratio of the acid scavenger to p-hydroxybenzaldehyde is 1:1-1.1, the mass ratio of p-hydroxybenzaldehyde to solvent b is 1:30-40, the reaction temperature is 60-65° C., the reaction time is 10-12 h, and the reaction is carried out in a reflux manner.

7. The method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant according to claim 5, characterized in that: The molar ratio of p-hydroxybenzaldehyde in step (a) to thiourea in step (b) is 2:1-1.

2. In step (b), the reaction is continued for 5-7 hours.

8. The method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant according to claim 5, characterized in that: The molar ratio of p-hydroxybenzaldehyde in step (a) to DOPO in step (c) is 1:1-1.

2. In step (c), the reaction temperature is 65-70° C., the reaction time is 4-6 hours, and the reaction is carried out in a reflux manner.

9. A method for preparing a durable flame retardant nylon 6 fabric based on a reactive phosphorus-sulfur flame retardant according to any one of claims 1 to 8, characterized in that: The limiting oxygen index of the durable flame-retardant nylon 6 fabric is higher than 29.3%, the damaged length is less than 10.5cm, no molten droplets are generated, and it can still pass the vertical burning test after 40 washes, with the damaged length less than 14.4cm and no molten droplets generated.

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