A kind of N / P / Si synergistic flame retardant and preparation method of flame retardant spandex thereof

Abstract

The invention discloses a N / P / Si synergistic flame retardant and a method for preparing a flame-retardant spandex thereof. The structure of the flame retardant contains HO-siloxane-C-N hexacyclic ring or N-P hexacyclic ring-siloxane-OH; the C-N hexacyclic ring and the N-P hexacyclic ring are one of pyrimidine, triazine ring and phosphazene ring; the hydrogen moieties on the C-N hexacyclic ring and the N-P hexacyclic ring are replaced by pentaerythritol phosphate, dimethyl hydroxymethyl phosphite, diphenyl phosphonic acid, dimethyl phosphonic acid and diphenyl phosphate. The product of the reaction of the flame retardant with polytetramethylene ether glycol and diisocyanate compound is used to prepare polyether flame-retardant spandex; the flame retardant is mixed with dibasic acid and diol, polycondensed to obtain flame-retardant polyester diol, and then the product of the reaction with diisocyanate compound is used to prepare polyester flame-retardant spandex. The invention realizes that the spandex oxygen index can be greatly improved and the droplets can be reduced by adding a small amount of flame retardant, and the flame retardancy and water washing resistance are good.

Description

Technical Field

[0001] The invention relates to the technical field of textiles, and in particular to a method for preparing a N / P / Si synergistic flame retardant and flame retardant spandex thereof. Background Art

[0002] Spandex is a polyurethane elastic fiber with properties similar to rubber, such as high elasticity and high elongation. It can be used in clothing that needs to have stretch elasticity while meeting comfort requirements, such as professional sportswear, fitness clothing and exercise clothing, surgical protective clothing, performance clothing, etc. However, the limiting oxygen index of spandex is only 18%, and it burns very quickly. Even when blended with other flame-retardant fibers, its flammability will seriously affect the flame-retardant properties of flame-retardant fabrics and fabrics, which limits its application in the field of flame-retardant textiles.

[0003] Chinese patent CN103590138B discloses a method for preparing flame-retardant polyurethane elastic fiber, wherein a phosphorus-based flame retardant containing hydroxyl and carboxyl groups is embedded in the main chain of spandex molecules during the chain extension process as a reactive flame retardant, and a melamine-based flame retardant and an aluminum oxide flame retardant are mixed with a polyurethane stock solution as additive flame retardants and prepared by dry spinning. CN106283265B inserts an alkyl alcohol amine chain extender into the interlayer of ZrP, and then participates in the chain extension of a polyurethane prepolymer to prepare a zirconium phosphate synergistic flame retardant spandex. CN105420844B discloses a method for preparing flame-retardant spandex fiber, wherein a halogen-free phosphorus-based flame retardant of a phenylphosphonate and a synergistic flame retardant of a non-metallic oxide are added to a polyurethane polymer solution to obtain flame-retardant spandex. The oxygen index of spandex fiber can be improved to a certain extent by introducing phosphorus-containing substances into the main chain and adding additive flame retardants to spandex, but a large amount of flame retardants need to be added, and anti-drip has not been effectively solved. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention provides a N / P / Si synergistic flame retardant and a method for preparing flame-retardant spandex thereof. The present invention adopts an in-situ polymerization process to achieve the addition of a small amount of flame retardant, which can greatly improve the oxygen index of spandex and reduce droplets, and has good flame retardancy and water washability, and improves the low-temperature flexibility and thermal stability of spandex.

[0005] The technical solution of the present invention is as follows:

[0006] The first object of the present invention is to provide a N / P / Si synergistic flame retardant, the structure of which contains HO-siloxane-CN six-membered ring or NP six-membered ring-siloxane-OH;

[0007] The CN six-membered ring and the NP six-membered ring are one of pyrimidine ring, triazine ring and phosphazene ring;

[0008] The hydrogen portions on the CN six-membered ring and the NP six-membered ring are replaced by pentaerythritol phosphate, dimethyl hydroxymethyl phosphite, diphenyl phosphate, dimethyl phosphate, and diphenyl phosphate.

[0009] In one embodiment of the present invention, the structure of the N / P / Si synergistic flame retardant is as shown in general formula (1) or general formula (2):

[0010]

[0011] In the general formula (1), X represents C or N;

[0012] In the general formula (1) and the general formula (2), m and n are integers of 0 to 3 respectively;

[0013] R are independently expressed as One of them.

[0014] In one embodiment of the present invention, the structure of the N / P / Si synergistic flame retardant is any one of the following structures:

[0015]

[0016] The second object of the present invention is to provide a method for preparing the above-mentioned N / P / Si synergistic flame retardant, comprising the following steps:

[0017] Under nitrogen protection, the chlorinated CN hexacyclic ring or the NP hexacyclic ring is dissolved in an organic solvent, the phosphate ester and triethylamine are dissolved in an organic solvent, the two solutions are mixed and reacted fully, the dihydroxy-containing siloxane material is dissolved in an organic solvent, the above reaction solution is added, and the reaction is carried out at 60-80° C. for 4-24 hours. Finally, the reaction mixture is cooled, washed, and dried under reduced pressure to obtain the N / P / Si synergistic flame retardant.

[0018] In one embodiment of the present invention, the molar ratio of the chlorinated CN six-membered ring or the NP six-membered ring to the phosphate ester is 1:1.

[0019] In one embodiment of the present invention, the molar ratio of the dihydroxy-containing siloxane-based material to the chlorinated CN six-membered ring or NP six-membered ring is 2:1.

[0020] The third object of the present invention is to provide a flame-retardant polyester diol prepared by the above-mentioned N / P / Si synergistic flame retardant. The above-mentioned N / P / Si synergistic flame retardant is mixed with a dibasic acid and a diol, and a condensation reaction is carried out under the action of a catalyst to obtain a flame-retardant polyester diol.

[0021] The fourth object of the present invention is to provide a method for preparing a flame retardant polyester diol using the above-mentioned N / P / Si synergistic flame retardant, comprising the following steps:

[0022] N / P / Si synergistic flame retardant, dibasic acid and diol are mixed, and a catalyst is added. The mixture is stirred at 180-240°C under nitrogen protection. When no more water is produced, the esterification reaction ends. The temperature is then raised to 190-250°C again, and a polycondensation reaction is carried out at -0.1MPa for 2-6 hours to obtain a hydroxyl-terminated N / P / Si flame retardant polyester diol with a molecular weight of 1600-3000.

[0023] In one embodiment of the present invention, the dibasic acid is one or more of terephthalic acid (PTA), phthalic acid (PA), isophthalic acid (PIA), naphthalene dicarboxylic acid (NDA), cyclohexanedicarboxylic acid (CHDA), malonic acid (MA), succinic acid (SA), glutaric acid (GA), adipic acid (H2A), pimelic acid, suberic acid, sebacic acid, dodecanedioic acid (DDCA), 2,5-furandicarboxylic acid (FDCA), and itaconic acid (IA); the diol is one or more of ethylene glycol (EG), 1,2-propylene glycol (PG), 2-methylpropanediol (MPD), 1,3-propylene glycol (PDO), 1,4-butanediol (BDO), and neopentyl glycol (NPG); and the catalyst is one or more of antimony trioxide, antimony acetate, tetrabutyl titanate, titanium ethylene glycol, stannous octoate, and triethylaluminum.

[0024] In one embodiment of the present invention, the molar ratio of N / P / Si synergistic flame retardant, dibasic acid, and diol is 0.5-2.5:10:8-10.5.

[0025] The fifth object of the present invention is to provide an application of the above-mentioned N / P / Si synergistic flame retardant for preparing polyether flame retardant spandex.

[0026] The sixth object of the present invention is to provide a polyether flame-retardant spandex prepared by the above-mentioned N / P / Si synergistic flame retardant, and the reaction product of the above-mentioned N / P / Si synergistic flame retardant with polytetramethylene ether glycol and diisocyanate compound is used to prepare spinning solution.

[0027] The seventh object of the present invention is to provide a method for preparing polyether flame retardant spandex using the above-mentioned N / P / Si synergistic flame retardant, comprising the following steps:

[0028] (1) polytetramethylene ether glycol, diisocyanate compound and the above-mentioned N / P / Si synergistic flame retardant are mixed in proportion and reacted at 89-109° C. for 90-130 minutes to form a prepolymer solution;

[0029] (2) The prepolymer solution is cooled to 8-10° C., and mixed amine is added under stirring conditions to carry out chain extension reaction and chain termination reaction to form a high viscosity polymer;

[0030] (3) the high viscosity polymer is mixed with an anti-yellowing agent, a matting agent, an antioxidant, and magnesium stearate to form a spinning solution;

[0031] (4) After the spinning solution is matured, the polyether flame-retardant spandex is spun using a dry spinning system.

[0032] In one embodiment of the present invention, the diisocyanate compound is selected from one or more of 4,4'-diphenylmethane diisocyanate (4,4-MDI), 2,4'-diphenylmethane diisocyanate (2,4-MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4'-diisocyanate (HMDI), and tetramethylxylene diisocyanate (TMXDI).

[0033] In one embodiment of the present invention, the molecular weight of polytetramethylene ether glycol is 1800-3000.

[0034] In one embodiment of the present invention, the total hydroxyl molar ratio of the isocyanate of the diisocyanate compound to polytetramethylene ether glycol (PTMEG) and the N / P / Si synergistic flame retardant is 1.4-2.1, and the hydroxyl molar ratio of polytetramethylene ether glycol (PTMEG) and the N / P / Si synergistic flame retardant is 1-10.

[0035] In one embodiment of the present invention, the mixed amine is composed of a chain extender and a terminator; the chain extender is selected from one or more of ethylenediamine, pentamethylenediamine, malonic acid hydrazide, and adipic acid dihydrazide, and the terminator is selected from one or more of diethylamine, dipropylamine, cyclohexylamine, n-butanol, and ethanolamine.

[0036] The eighth object of the present invention is to provide an application of the flame-retardant polyester diol for preparing polyester-type flame-retardant spandex.

[0037] The ninth object of the present invention is to provide a polyester-type flame-retardant spandex prepared from the flame-retardant polyester diol, wherein the reaction product of the flame-retardant polyester diol and the diisocyanate compound is used to prepare a spinning solution.

[0038] The tenth object of the present invention is to provide a method for preparing polyester-type flame-retardant spandex using the flame-retardant polyester diol, comprising the following steps:

[0039] (1) The flame retardant polyester diol and the diisocyanate compound are mixed in proportion and reacted at 89-109° C. for 90-130 minutes to form a prepolymer solution;

[0040] (2) The prepolymer solution is cooled to 8-10° C., and mixed amine is added under stirring conditions to carry out chain extension reaction and chain termination reaction to form a high viscosity polymer;

[0041] (3) the high viscosity polymer is mixed with an anti-yellowing agent, a matting agent, an antioxidant, and magnesium stearate to form a spinning solution;

[0042] (4) After the spinning solution is matured, polyester flame-retardant spandex is spun using a dry spinning system.

[0043] In one embodiment of the present invention, the diisocyanate compound is selected from one or more of 4,4'-diphenylmethane diisocyanate (4,4-MDI), 2,4'-diphenylmethane diisocyanate (2,4-MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexylmethane-4,4'-diisocyanate (HMDI), and tetramethylxylene diisocyanate (TMXDI).

[0044] In one embodiment of the present invention, the molar ratio of the isocyanate of the diisocyanate compound to the hydroxyl group of the flame retardant polyester diol is 1.4-2.1.

[0045] In one embodiment of the present invention, the mixed amine is composed of a chain extender and a terminator; the chain extender is selected from one or more of ethylenediamine, pentamethylenediamine, malonic acid hydrazide, and adipic acid dihydrazide, and the terminator is selected from one or more of diethylamine, dipropylamine, cyclohexylamine, n-butanol, and ethanolamine.

[0046] The beneficial technical effects of the present invention are:

[0047] The present invention adopts an in-situ polymerization process to add a small amount of flame retardant to greatly improve the oxygen index of spandex and reduce droplets, and has good flame retardancy and water washability, and improves the low-temperature flexibility and thermal stability of spandex. DETAILED DESCRIPTION

[0048] The present invention will be described in detail below in conjunction with the embodiments.

[0049] Example 1: Flame retardant

[0050]

[0051] Under nitrogen protection, 18.5g trichlorotriazine (TCT) was dissolved in 120mL 1,4-dioxane, 18.01g pentaerythritol phosphate (PEPA) and 13.9mL triethylamine were dissolved in 100mL 1,4-dioxane, and the trichlorotriazine solution was slowly added dropwise to react at room temperature for 6h. After that, 33.3g 1,1,3,3-tetramethyl-1,3-disiloxanediol (DT) and 27.8mL triethylamine were dissolved in 150mL dioxane, and slowly added dropwise to the above reaction solution, and refluxed at 80°C for 8h. The precipitate was washed five times with distilled water and acetone, and the reaction mixture was cooled, washed, and dried under reduced pressure to obtain DT-TCT(PEPA)-DT.

[0052] Example 2: Flame Retardant

[0053]

[0054] Under nitrogen protection, 56.02g of dimethyl hydroxymethylphosphite (DMPM) and 67.25g of triethylamine (TEA) were dissolved in 250mL of anhydrous THF and cooled in an ice-water bath. 34.76g of hexachlorocyclotriphosphazene (HCCTP) was dissolved in 200mL of THF and cooled in an ice-water bath. The DMPM solution was slowly added dropwise to the HCCTP solution, and the reaction was carried out at room temperature for 48h after the addition was completed.

[0055] Under nitrogen protection, 50.08 g of 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane (BHTTD) and 30.36 g of triethylamine (TEA) were added to 200 mL of THF, cooled in an ice-water bath, and slowly dripped into the above reaction solution. After the addition was completed, the reaction was carried out at 60° C. for 24 h. The reaction mixture was washed and dried under reduced pressure to obtain BHTTD-HCCTP(DMPM)-BHTTD.

[0056] Example 3: Flame retardant

[0057]

[0058] Under nitrogen protection, 21.82g of diphenylphosphoric acid (DPPA) and 10.12g of triethylamine (TEA) were dissolved in 250mL of anhydrous DMF and cooled in an ice-water bath. 18.34g of 2,4,6-trichloropyrimidine (TCPY) was dissolved in 200mL of DMF and cooled in an ice-water bath. The DPPA solution was slowly added dropwise to the TCPY solution, and the reaction was carried out at room temperature for 10h after the addition was completed. 50.08g of 1,3-bis(3-hydroxypropyl)-1,1,3,3-tetramethyldisiloxane (BHTTD) and 30.36g of triethylamine (TEA) were added to 200mL of THF, cooled in an ice-water bath, and slowly added dropwise to the above reaction solution. After the addition was completed, the reaction was carried out at 70°C for 4h. The reaction mixture was washed and dried under reduced pressure to obtain BHTTD-TCPY(DPPA)-BHTTD.

[0059] Example 4 Flame retardant polyester diol

[0060] Under nitrogen protection, DT-TCT (PEPA) -DT, 1,4-succinic acid (SA) and 1,4-butanediol (BDO) with a molar ratio of 2:10:8.5 were placed in a flask, and tetrabutyl titanate with a molar amount of 0.12% of 1,4-succinic acid (SA) was added, and the temperature was raised to 180 ° C and stirred vigorously. When no water was produced, the esterification reaction was completed. Then the temperature was raised to 190 ° C, and the polycondensation reaction was carried out at -0.1 MPa for 5 hours. The flame-retardant polyester diol DTD-SA-BDO with a molecular weight of 2000 and end-capped with terminal hydroxyl groups was obtained.

[0061] Example 5: Flame retardant polyester diol

[0062] Under nitrogen protection, BHTTD-HCCTP(DMPM)-BHTTD, terephthalic acid (PTA) and ethylene glycol with a molar ratio of 1:10:9.5 were placed in a flask, and antimony trioxide with a molar amount of 0.18% of terephthalic acid (PTA) was added, and the temperature was raised to 235°C and stirred strongly for prepolymerization. Then the temperature was raised to 250°C, and the polycondensation reaction was carried out at 80Pa for 3 hours. The flame-retardant polyester diol BHB-PTA-EG with a molecular weight of 2800 and end-capped with terminal hydroxyl groups was obtained.

[0063] Example 6: Flame retardant polyester diol

[0064] Under nitrogen protection, BHTTD-TCPY(DPPA)-BHTTD, adipic acid (H2A) and 1,3-propylene glycol (PDO) with a molar ratio of 1.5:10:9 were placed in a flask, and stannous octoate with a molar amount of 0.16% of adipic acid (H2A) was added, and the temperature was raised to 215°C and stirred strongly for prepolymerization. Then the temperature was raised to 230°C, and the polycondensation reaction was carried out at 80Pa for 3 hours. The flame-retardant polyester diol BTB-H2A-PDO with a molecular weight of 2600 and end-capped with terminal hydroxyl groups was obtained.

[0065] Example 7: Polyester flame retardant spandex

[0066] (1) Preparation of prepolymer: 2911 g of DTD-SA-BDO with a molecular weight of 2000 and 639 g of 4,4-MDI were reacted at 90° C. for 130 min to obtain a prepolymer having isocyanate groups at both ends. 6550 g of N,N-dimethylacetamide was used to dissolve the prepolymer, and the temperature was cooled to 10° C. to obtain a prepolymer solution.

[0067] (2) 9 g of ethylenediamine and 7 g of diethylamine were added to 1134 g of N,N-dimethylacetamide to obtain a mixed ammonia solution, which was added to a prepolymer solution cooled to 10° C. while stirring, to finally obtain a high-viscosity stable polymer.

[0068] (3) 6 g of an anti-yellowing agent, 12 g of a matting agent, titanium dioxide, 3 g of an antioxidant, and 14 g of magnesium stearate were added to the polymer solution to obtain a spinning solution.

[0069] (4) The spinning solution is aged at 40° C., and then flame-retardant spandex is prepared by a dry spinning system through processes such as liquid discharge, spraying, stretching, false twisting, and oiling.

[0070] Example 8: Polyester flame retardant spandex

[0071] (1) 3061 g of BTB-H2A-PDO with a molecular weight of 2600, 489 g of 4,4-MDI, and 40 g of IPDI were reacted at 90° C. for 130 min to obtain a prepolymer having isocyanate groups at both ends. 6766 g of N,N-dimethylacetamide was used to dissolve the prepolymer, and the temperature was cooled to 10° C. to obtain a prepolymer solution.

[0072] (2) 53 g of ethylenediamine, 17 g of adipic acid dihydrazide, and 6 g of diethylamine were added to 1134 g of N,N-dimethylacetamide to obtain a mixed ammonia solution, which was added to a prepolymer solution cooled to 10° C. while stirring, to finally obtain a high-viscosity stable polymer.

[0073] (3) 6 g of an anti-yellowing agent, 12 g of a matting agent, titanium dioxide, 3 g of an antioxidant, and 14 g of magnesium stearate were added to the polymer solution to obtain a spinning solution.

[0074] (4) The spinning solution is aged at 40° C., and then flame-retardant spandex is prepared by a dry spinning system through processes such as liquid discharge, spraying, stretching, false twisting, and oiling.

[0075] Example 9: Polyether flame retardant spandex

[0076] (1) 2516 g of polytetramethylene ether glycol with a molecular weight of 2000, 757 g of 4,4-MDI and 368 g of DT-TCT (PEPA)-DT were reacted at 90° C. for 130 min to obtain a prepolymer having isocyanate groups at both ends. 6720 g of N,N-dimethylacetamide was added to dissolve the prepolymer, and the temperature was cooled to 10° C. to obtain a prepolymer solution.

[0077] (2) 62 g of ethylenediamine, 20 g of adipic acid dihydrazide, and 7 g of diethylamine were added to 1538 g of N,N-dimethylacetamide to obtain a mixed ammonia solution, which was added to a prepolymer solution cooled to 10° C. while stirring, to finally obtain a high-viscosity stable polymer.

[0078] (3) 6 g of an anti-yellowing agent, 13 g of a matting agent, titanium dioxide, 4 g of an antioxidant, and 12 g of magnesium stearate were added to the polymer solution to obtain a spinning solution.

[0079] (4) The spinning solution is aged at 40° C., and then flame-retardant spandex is prepared by a dry spinning system through processes such as liquid discharge, spraying, stretching, false twisting, and oiling.

[0080] Example 10: Polyether flame retardant spandex

[0081] (1) 2561 g of polytetramethylene ether glycol with a molecular weight of 2000, 667 g of 4,4-MDI, 28 g of HDI and 216 g of BHTTD-HCCTP (DMPM) -BHTTD were reacted at 90°C for 130 min to obtain a prepolymer having isocyanate groups at both ends. 6260 g of N,N-dimethylacetamide was used to dissolve the prepolymer, and the temperature was cooled to 10°C to obtain a prepolymer solution.

[0082] (2) 66 g of ethylenediamine and 8 g of diethylamine were added to 1274 g of N,N-dimethylacetamide to obtain a mixed ammonia solution, which was added to a prepolymer solution cooled to 10° C. while stirring, to finally obtain a high-viscosity stable polymer.

[0083] (3) 6 g of an anti-yellowing agent, 12 g of a matting agent, titanium dioxide, 3 g of an antioxidant, and 14 g of magnesium stearate were added to the polymer solution to obtain a spinning solution.

[0084] (4) The spinning solution is aged at 40° C., and then flame-retardant spandex is prepared by a dry spinning system through processes such as liquid discharge, spraying, stretching, false twisting, and oiling.

[0085] Comparative Example 1:

[0086] (1) 2883 g of polytetramethylene ether glycol with a molecular weight of 2000 and 670 g of 4,4-MDI were heated to 90° C. and reacted for 130 min to obtain a prepolymer having isocyanate groups at both ends. 6030 g of N,N-dimethylacetamide was added to dissolve the prepolymer, and the temperature was cooled to 10° C. to obtain a prepolymer solution.

[0087] (2) 62 g of ethylenediamine and 10 g of diethylamine were added to 1393 g of N,N-dimethylacetamide to obtain a mixed ammonia solution, which was added to a prepolymer solution cooled to 10° C. while stirring, to finally obtain a high-viscosity stable polymer.

[0088] (3) 6 g of an anti-yellowing agent, 12 g of a matting agent, titanium dioxide, 5 g of an antioxidant, and 14 g of magnesium stearate were added to the polymer solution to obtain a spinning solution.

[0089] (4) Spinning: After the spinning solution is matured at 40°C, spandex is prepared by a dry spinning system through processes such as liquid discharge, spraying, stretching, false twisting, and oiling.

[0090] The performance of the spandex obtained in Example 1 and Comparative Example 1 was tested, and the test results are shown in Table 1.

[0091] Table 1

[0092]

[0093] Note: Tensile test: FZ / T 54010-2014 "Spandex Filament";

[0094] Oxygen index test: After washing 10 times, follow the "GB / T 5454-1997 Textile Combustion Performance Test Oxygen Index Method".

[0095] It can be seen from Table 1 that the flame retardant of the present invention enables the spandex fiber to have excellent flame retardancy, water washability and good anti-dripping performance. The in-situ polymerization process makes the flame retardant spandex have good spinnability and the flame retardant has little effect on the mechanical properties of the spandex fiber. At the same time, the N / P / Si synergistic effect makes the flame retardant performance of the spandex more prominent.

[0096] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A N / P / Si synergistic flame retardant, characterized in that: The structure of the flame retardant contains HO-siloxane-CN six-membered ring or NP six-membered ring-siloxane-OH; The CN six-membered ring and the NP six-membered ring are one of pyrimidine ring, triazine ring and phosphazene ring; The hydrogen portions on the CN six-membered ring and the NP six-membered ring are replaced by pentaerythritol phosphate, dimethyl hydroxymethyl phosphite, diphenyl phosphate, dimethyl phosphate, and diphenyl phosphate.

2. The N / P / Si synergistic flame retardant according to claim 1, characterized in that: The structure is shown in general formula (1) or general formula (2): In the general formula (1), X represents C or N; In general formula (1) and general formula (2), m and n are integers of 0-3 respectively; R are independently expressed as One of them.

3. The N / P / Si synergistic flame retardant according to claim 1, characterized in that: Its structure is any of the following:

4. A flame-retardant polyester diol prepared by using the N / P / Si synergistic flame retardant according to claim 1, characterized in that: The N / P / Si synergistic flame retardant is mixed with a dibasic acid and a diol, and a polycondensation reaction is carried out under the action of a catalyst to prepare a flame-retardant polyester diol.

5. The flame retardant polyester diol according to claim 4, characterized in that: The dibasic acid is one or more of terephthalic acid, phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid, 2,5-furandicarboxylic acid, and itaconic acid; the dihydric alcohol is one or more of ethylene glycol, 1,2-propylene glycol, 2-methylpropylene glycol, 1,3-propylene glycol, 1,4-butanediol, and neopentyl glycol; the catalyst is one or more of antimony trioxide, antimony acetate, tetrabutyl titanate, ethylene glycol titanium, stannous octoate, and triethylaluminum.

6. The flame retardant polyester diol according to claim 4, characterized in that: The molar ratio of the flame retardant, the dibasic acid and the diol is 0.5-2.5:10:8-10.

5.

7. An application of the N / P / Si synergistic flame retardant according to claim 1, characterized in that: Used to prepare polyether flame-retardant spandex.

8. A polyether flame retardant spandex prepared by the N / P / Si synergistic flame retardant according to claim 1, characterized in that: The reaction product of the N / P / Si synergistic flame retardant, polytetramethylene ether glycol and diisocyanate compound is used to prepare spinning solution.

9. An application of the flame retardant polyester diol according to claim 4, characterized in that: Used to prepare polyester flame-retardant spandex.

10. A polyester flame retardant spandex prepared from the flame retardant polyester diol according to claim 4, characterized in that: The reaction product of the flame retardant polyester diol and the diisocyanate compound is used to prepare spinning solution.

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