A high-strength heat-resistant polylactic acid DTY filament and preparation method thereof

Abstract

The present invention relates to the field of synthetic fibers, and discloses a high-strength heat-resistant polylactic acid DTY filament and a preparation method thereof. The preparation method comprises: reacting a flame-retardant polyurethane prepolymer with epoxidized montmorillonite to obtain a flame-retardant compatibilizer, mixing the prepolymer with polylactic acid slices and polybutylene terephthalate-adipate slices for melt spinning to obtain polylactic acid POY filaments, and then preparing high-strength heat-resistant polylactic acid DTY filaments through stretching and false twisting deformation. The polylactic acid DTY filaments have good heat resistance, good mechanical properties, and improved flame retardancy.

Description

Technical Field

[0001] The invention relates to the field of synthetic fibers, and in particular to high-strength heat-resistant polylactic acid DTY filaments and a preparation method thereof. Background Art

[0002] Polylactic acid fiber combines the excellent properties of natural fibers and synthetic fibers, and has the advantages of biodegradability, high elastic recovery, good wrinkle resistance, and non-flammability, and is expected to replace traditional synthetic fibers. However, it has the disadvantages of being easily hydrolyzed at high temperatures, poor heat resistance, higher heat shrinkage than traditional synthetic fibers, and poor dimensional stability. DTY stretch textured yarn is a yarn that is falsely twisted and deformed while stretching the POY pre-oriented yarn on a texturing machine, so that the fibers of the yarn are separated and fluffy, and the cross section is irregular. The air permeability and feel are better than FDY.

[0003] Existing technologies such as Chinese patent application CN118147783A disclose a preparation process of high-toughness hydrolysis-resistant polylactic acid FDY filaments, which uses lanthanum pyromellitic acid, anti-hydrolysis agent, and eugenol to modify polylactic acid fibers, improve the toughness of the product by adding a toughening agent, and improve the hydrolysis resistance of the product by adding an anti-hydrolysis agent. The compound of lanthanum pyromellitic acid, anti-hydrolysis agent, and eugenol can play a synergistic role, thereby greatly improving the hydrolysis resistance of the product. Although the mechanical properties and heat resistance and hydrolysis resistance of polylactic acid fibers are improved, the flame retardant properties of the material need to be improved. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a high-strength heat-resistant polylactic acid DTY filament and a preparation method thereof. The polylactic acid DTY filament has good heat resistance, good mechanical properties and improved flame retardancy.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A method for preparing high-strength heat-resistant polylactic acid DTY filaments comprises the following steps:

[0007] Step (1), dissolving hexachlorocyclotriphosphazene and xylene, adding n-propanol in a nitrogen atmosphere, and dripping triethylamine. After the dripping is complete, reacting, filtering after the reaction is complete, and collecting the filtrate to obtain an intermediate product;

[0008] Add ethanolamine dropwise to the intermediate product, continue the reaction after the addition is complete, and purify after the reaction is complete to obtain a modified cyclotriphosphazene;

[0009] Step (2), mixing toluene-2,4-diisocyanate and polylactic acid diol, adding a catalyst, reacting, adding modified cyclotriphosphazene after the reaction is completed, and continuing the reaction, after the reaction is completed, obtaining a polyurethane prepolymer;

[0010] Step (3), mixing the polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole, and reacting them, and obtaining a flame retardant compatibilizer after the reaction is completed;

[0011] Step (4), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn;

[0012] The polylactic acid POY filament is subjected to heating and stretching, cooling, friction twisting, netting, heat setting, oiling and winding to obtain high-strength and heat-resistant polylactic acid DTY filament.

[0013] Preferably, in step (1), the mass ratio of hexachlorocyclotriphosphazene, xylene, n-propanol, triethylamine and ethanolamine is 11-11.4:90-100:12-13:13.5-13.8:13-14; the reaction conditions are: react at 65-70°C for 5-6h; and the continued reaction conditions are: continue to react at 65-70°C for 5-6h.

[0014] Preferably, the triethylamine is added dropwise at 65-70°C for 15-20 min, and the ethanolamine is added dropwise at 65-70°C for 15-20 min in a nitrogen atmosphere.

[0015] Preferably, the purification operation includes: removing the upper layer solvent after the reaction is completed to obtain a crude reaction product, adding xylene 5-8 times the mass of the crude reaction product for washing, drying at 50-60°C for 20-24h, washing with a saturated sodium bicarbonate aqueous solution until neutral, rotary evaporating to remove the solvent water, adding ethanol 5-8 times the mass of the reaction product to dissolve, filtering, taking the filtrate, rotary evaporating again to remove the solvent ethanol, and drying at 50-60°C for 20-24h.

[0016] Preferably, in step (2), the molar ratio of toluene-2,4-diisocyanate to polylactic acid diol is 3-3.5:1; the amount of modified cyclotriphosphazene added is 8-10% of the total mass of toluene-2,4-diisocyanate and polylactic acid diol; the reaction conditions are: reacting at 70-80°C for 20-30min in a nitrogen atmosphere; and the continued reaction conditions are: continuing the reaction at 75-85°C for 1-2h.

[0017] Preferably, the catalyst comprises dibutyltin dilaurate, and the added amount is 0.5-1% of the mass of the polylactic acid diol.

[0018] Preferably, in step (3), the mass ratio of the polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole is 50:10-15:0.1; and the reaction conditions are: reacting at a temperature of 150-160° C. for 2-3 hours.

[0019] Preferably, in step (3), the epoxidized montmorillonite is prepared by the following steps:

[0020] Epichlorohydrin and methanol are mixed and dissolved, hexadecyl dimethyl tertiary amine is added, and the reaction is carried out. After the reaction is completed, the solvent methanol is removed by rotary evaporation, and the mixture is washed to obtain an epoxy intercalation agent;

[0021] The molar ratio of epichlorohydrin to hexadecyl dimethyl tertiary amine is 1.1-1.2:1; the reaction conditions are: stirring the reaction at 60-65°C for 6-7h;

[0022] Mixing montmorillonite with water, ultrasonically dispersing, adding epoxy intercalation agent, reacting, centrifuging, filtering, washing, drying, grinding and sieving to obtain epoxidized montmorillonite;

[0023] The mass ratio of montmorillonite to epoxy intercalant is 1:1.25-1.3; the reaction conditions are: reacting at a temperature of 60-70°C for 6-7h.

[0024] Preferably, in step (4), the mass ratio of the flame retardant compatibilizer, the polylactic acid chips, and the polybutylene terephthalate-adipate chips is 0.8-1.2:90:10.

[0025] Preferably, in step (4), the mixing conditions are: mixing at a temperature of 190-195°C for 7-8 minutes; the melt spinning conditions are: spinning temperature of 230-235°C; spinning speed of 2800-3200 m / min; spinneret aspect ratio of 3-3.5; heating and stretching temperature of 120-125°C and stretching multiple of 1.2-1.5; friction twisting D / Y ratio of 1.6-1.9; netting pressure of 0.1-0.3 MPa; and heat setting temperature of 88-92°C.

[0026] Preferably, a high-strength heat-resistant polylactic acid DTY filament is prepared by the method for preparing the high-strength heat-resistant polylactic acid DTY filament as described above.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The invention utilizes a nucleophilic substitution reaction to replace part of the chlorine atoms in hexachlorocyclotriphosphazene with n-propanol, and then introduces ethanolamine to continue the reaction to replace the remaining chlorine atoms, thereby obtaining a modified cyclotriphosphazene with active hydroxyl groups, which is reacted with toluene-2,4-diisocyanate and polylactic acid diol to obtain a polyurethane prepolymer containing a polylactic acid segment and a flame-retardant cyclotriphosphazene structure;

[0029] Among them, the polylactic acid chain segments in the polyurethane prepolymer have good compatibility with the matrix material polylactic acid chips; the cyclotriphosphazene structure is a six-membered ring structure composed of phosphorus and nitrogen atoms, which has rigidity and good thermal stability, and the phosphorus and nitrogen content in the structure is relatively high, and the flame retardant properties are excellent, which gives the polyurethane prepolymer excellent flame retardant properties and heat resistance.

[0030] Montmorillonite is a layered aluminum silicate clay. The clay layer is composed of silicon oxygen tetrahedrons and aluminum oxygen octahedrons connected by shared oxygen atoms. It has a good thermal insulation effect, can reduce the heat release rate of polymer combustion, and can be added to the polymer matrix to improve the heat resistance and flame retardancy of the material. The invention obtains an epoxy intercalant by reacting epichlorohydrin with a quaternary ammonium salt of hexadecyldimethyl tertiary amine, and uses the epoxy intercalant for intercalation modification of montmorillonite, thereby increasing the interlayer distance of the montmorillonite and introducing epoxy functional groups to obtain epoxidized montmorillonite; the epoxy groups of the epoxidized montmorillonite react with isocyanate groups of polyurethane prepolymers under the condition of imidazole catalysts to generate oxazolidinone structures, so that the inorganic flame retardant filler montmorillonite and the flame retardant functionalized polyurethane prepolymers are connected through chemical bonds to obtain a flame retardant compatibilizer; the flame retardant compatibilizer, polylactic acid slices, and polybutylene terephthalate-adipate slices are mixed and melt-spun to prepare polylactic acid POY yarns, and high-strength heat-resistant polylactic acid DTY filaments are obtained after stretching and false twisting deformation;

[0031] Among them, the five-membered ring structure of oxazolidinone in the flame-retardant compatibilizer has a very high thermal decomposition temperature and excellent heat resistance. It can cooperate with the inorganic filler montmorillonite and the flame-retardant functionalized polyurethane prepolymer to improve the heat resistance and flame retardancy of the polylactic acid substrate. Since the flame-retardant compatibilizer contains an incompletely reacted isocyanate functional group, it can react with the terminal hydroxyl and / or terminal carboxyl groups of polylactic acid and polybutylene terephthalate-adipate during the melt mixing process to form a carbamate bond, which plays a role in compatibilization, increases the entanglement degree between the molecular chains of the polymer matrix, thereby improving the dispersibility and compatibility of the components in the polylactic acid matrix, and improving the mechanical properties of the polylactic acid DTY filament. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a process flow chart for preparing high-strength heat-resistant polylactic acid DTY filaments in the present invention;

[0033] Figure 2 It is a bar graph of the elongation at break of the polylactic acid DTY filaments prepared in Examples 1-5 and Comparative Examples 1-2 of the present invention in performance tests;

[0034] Figure 3 It is a bar graph of hot air shrinkage of polylactic acid DTY filaments prepared in Examples 1-5 and Comparative Examples 1-2 of the present invention in performance tests;

[0035] Figure 4It is a bar graph of the limiting oxygen index of the polylactic acid DTY filaments prepared in Examples 1-5 and Comparative Examples 1-2 of the present invention in performance tests. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment discloses a method for preparing high-strength heat-resistant polylactic acid DTY filaments, comprising the following steps:

[0039] Step (1), dissolving hexachlorocyclotriphosphazene and xylene, adding n-propanol in a nitrogen atmosphere, heating to 65°C, adding triethylamine dropwise for 15 min, reacting at 65°C for 6 h, filtering and collecting the filtrate to obtain an intermediate product;

[0040] Ethanolamine was added dropwise to the intermediate product in a nitrogen atmosphere at 65°C for 15 minutes. After the addition was completed, the reaction was continued at 65°C for 6 hours. After the reaction was completed, the upper solvent was removed to obtain a crude reaction product. Xylene with a mass of 5 times that of the crude reaction product was added for washing. The product was dried at 50°C for 24 hours to obtain a reaction product. The product was purified to obtain a modified cyclotriphosphazene.

[0041] The mass ratio of hexachlorocyclotriphosphazene, xylene, n-propanol, triethylamine and ethanolamine is 11:90:12:13.5:13; the purification operation comprises: washing the reaction product with a saturated sodium bicarbonate aqueous solution until neutral, removing the solvent water by rotary evaporation, adding ethanol 5 times the mass of the reaction product to dissolve, filtering, taking the filtrate, removing the solvent ethanol by rotary evaporation again, and drying at 50°C for 24 hours;

[0042] Step (2), mixing toluene-2,4-diisocyanate and polylactic acid diol in a molar ratio of 3:1, adding a catalyst dibutyltin dilaurate of 0.5% by mass of the polylactic acid diol, reacting for 30 minutes in a nitrogen atmosphere at 70°C, adding modified cyclotriphosphazene after the reaction, wherein the amount of modified cyclotriphosphazene added is 8% of the total mass of toluene-2,4-diisocyanate and polylactic acid diol, and continuing the reaction at 75°C for 2 hours. After the reaction is completed, a polyurethane prepolymer is obtained;

[0043] Step (3), mixing the polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole in a mass ratio of 50:10:0.1, reacting at 150° C. for 3 hours, and obtaining a flame retardant compatibilizer after the reaction is completed;

[0044] Wherein, the epoxidized montmorillonite is prepared by the following steps:

[0045] Epichlorohydrin and methanol were mixed and dissolved in a volume ratio of 1:3, hexadecyl dimethyl tertiary amine was added at 60°C, the molar ratio of epichlorohydrin to hexadecyl dimethyl tertiary amine was 1.1:1, and the mixture was stirred and reacted at 60°C for 6 hours. After the reaction was completed, the solvent methanol was removed by rotary evaporation to obtain a reaction product, and ethanol 5 times the mass of the reaction product was added to wash three times to obtain an epoxy intercalation agent;

[0046] Mix montmorillonite and water at a mass ratio of 1:100, ultrasonically disperse for 10 minutes, add an epoxy intercalant, the mass ratio of montmorillonite to epoxy intercalant is 1:1.25, react at 60°C for 6 hours, centrifuge after the reaction, filter, take the filter cake, add 5-8 times the mass of the filter cake ethanol for washing, dry at 50°C for 12 hours, grind through a 400-mesh sieve to obtain epoxidized montmorillonite;

[0047] Step (4), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips at a mass ratio of 0.8:90:10 at 190° C. for 8 minutes, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn;

[0048] The melt spinning conditions are as follows: spinning temperature is 230°C; spinning speed is 2800 m / min; spinneret aspect ratio is 3;

[0049] The polylactic acid POY filament is heated and stretched, cooled, friction twisted, meshed, heat-set, oiled, and wound to obtain a high-strength heat-resistant polylactic acid DTY filament;

[0050] Among them, the temperature of heating and stretching is 120°C and the stretching ratio is 1.2; the D / Y ratio of friction twisting is 1.6; the pressure of meshing is 0.1MPa; and the temperature of heat setting is 88°C.

[0051] Example 2

[0052] This embodiment discloses a method for preparing high-strength heat-resistant polylactic acid DTY filaments, comprising the following steps:

[0053] Step (1), dissolving hexachlorocyclotriphosphazene and xylene, adding n-propanol in a nitrogen atmosphere, heating to 65°C, adding triethylamine dropwise for 15 min, reacting at 65°C for 5.5 h, filtering and collecting the filtrate to obtain an intermediate product;

[0054] Ethanolamine was added dropwise to the intermediate product in a nitrogen atmosphere at 65°C for 15 minutes. After the addition was completed, the reaction was continued at 65°C for 5.5 hours. After the reaction was completed, the upper solvent was removed to obtain a crude reaction product. Xylene with a mass of 5 times that of the crude reaction product was added for washing. The product was dried at 50°C for 24 hours to obtain a reaction product. The product was purified to obtain a modified cyclotriphosphazene.

[0055] The mass ratio of hexachlorocyclotriphosphazene, xylene, n-propanol, triethylamine and ethanolamine is 11.1:93:12.3:13.5:13.3; the purification operation comprises: washing the reaction product with a saturated sodium bicarbonate aqueous solution until neutral, removing the solvent water by rotary evaporation, adding ethanol 5 times the mass of the reaction product to dissolve, filtering, taking the filtrate, removing the solvent ethanol by rotary evaporation again, and drying at 50°C for 24 hours;

[0056] Step (2), mixing toluene-2,4-diisocyanate and polylactic acid diol in a molar ratio of 3.2:1, adding a catalyst dibutyltin dilaurate of 0.8% by mass of the polylactic acid diol, reacting for 25 minutes in a nitrogen atmosphere at 75°C, adding modified cyclotriphosphazene after the reaction, wherein the amount of modified cyclotriphosphazene added is 8.5% of the total mass of toluene-2,4-diisocyanate and polylactic acid diol, and continuing the reaction at 80°C for 1.5 hours. After the reaction is completed, a polyurethane prepolymer is obtained;

[0057] Step (3), mixing the polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole in a mass ratio of 50:11:0.1, reacting at 155° C. for 2.5 hours, and obtaining a flame retardant compatibilizer after the reaction is completed;

[0058] Wherein, the preparation of epoxidized montmorillonite is the same as that in Example 1;

[0059] Step (4), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips at a mass ratio of 0.9:90:10 at 190° C. for 8 minutes, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn;

[0060] The melt spinning conditions are as follows: spinning temperature is 233°C; spinning speed is 3000 m / min; spinneret aspect ratio is 3;

[0061] The polylactic acid POY filament is heated and stretched, cooled, friction twisted, meshed, heat-set, oiled, and wound to obtain a high-strength heat-resistant polylactic acid DTY filament;

[0062] Among them, the temperature of heating and stretching is 120°C and the stretching ratio is 1.2; the D / Y ratio of friction twisting is 1.6; the pressure of meshing is 0.1MPa; and the temperature of heat setting is 88°C.

[0063] Example 3

[0064] This embodiment discloses a method for preparing high-strength heat-resistant polylactic acid DTY filaments, comprising the following steps:

[0065] Step (1), dissolving hexachlorocyclotriphosphazene and xylene, adding n-propanol in a nitrogen atmosphere, heating to 65°C, adding triethylamine dropwise for 15 min, reacting at 65°C for 5.5 h, filtering and collecting the filtrate to obtain an intermediate product;

[0066] Ethanolamine was added dropwise to the intermediate product in a nitrogen atmosphere at 65°C for 15 minutes. After the addition was completed, the reaction was continued at 65°C for 5.5 hours. After the reaction was completed, the upper solvent was removed to obtain a crude reaction product. Xylene with a mass of 5 times that of the crude reaction product was added for washing. The product was dried at 50°C for 24 hours to obtain a reaction product. The product was purified to obtain a modified cyclotriphosphazene.

[0067] The mass ratio of hexachlorocyclotriphosphazene, xylene, n-propanol, triethylamine and ethanolamine is 11.2:95:12.5:13.6:13.5; the purification operation comprises: washing the reaction product with a saturated sodium bicarbonate aqueous solution until neutral, removing the solvent water by rotary evaporation, adding ethanol 5 times the mass of the reaction product to dissolve, filtering, taking the filtrate, removing the solvent ethanol by rotary evaporation again, and drying at 50°C for 24 hours;

[0068] Step (2), mixing toluene-2,4-diisocyanate and polylactic acid diol at a molar ratio of 3.3:1, adding a catalyst dibutyltin dilaurate of 0.8% by mass of the polylactic acid diol, reacting for 25 minutes in a nitrogen atmosphere at 75°C, adding modified cyclotriphosphazene after the reaction, wherein the amount of modified cyclotriphosphazene added is 9% of the total mass of toluene-2,4-diisocyanate and polylactic acid diol, and continuing the reaction at 80°C for 1.5 hours. After the reaction is completed, a polyurethane prepolymer is obtained;

[0069] Step (3), mixing the polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole in a mass ratio of 50:13:0.1, reacting at 155° C. for 2.5 hours, and obtaining a flame retardant compatibilizer after the reaction is completed;

[0070] Wherein, the preparation of epoxidized montmorillonite is the same as that in Example 1;

[0071] Step (4), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips in a mass ratio of 1:90:10 at 190° C. for 8 minutes, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn;

[0072] The melt spinning conditions are as follows: spinning temperature is 233°C; spinning speed is 3000 m / min; spinneret aspect ratio is 3;

[0073] The polylactic acid POY filament is heated and stretched, cooled, friction twisted, meshed, heat-set, oiled, and wound to obtain a high-strength heat-resistant polylactic acid DTY filament;

[0074] Among them, the temperature of heating and stretching is 120°C and the stretching ratio is 1.2; the D / Y ratio of friction twisting is 1.6; the pressure of meshing is 0.1MPa; and the temperature of heat setting is 88°C.

[0075] Example 4

[0076] This embodiment discloses a method for preparing high-strength heat-resistant polylactic acid DTY filaments, comprising the following steps:

[0077] Step (1), dissolving hexachlorocyclotriphosphazene and xylene, adding n-propanol in a nitrogen atmosphere, heating to 70°C, adding triethylamine dropwise for 20 min, reacting at 70°C for 5 h after the addition is complete, filtering and collecting the filtrate to obtain an intermediate product;

[0078] Ethanolamine was added dropwise to the intermediate product in a nitrogen atmosphere at 70°C for 20 minutes. After the addition was completed, the reaction was continued at 70°C for 5 hours. After the reaction was completed, the upper solvent was removed to obtain a crude reaction product. Xylene in an amount 8 times the mass of the crude reaction product was added for washing. The product was dried at 60°C for 20 hours to obtain a reaction product. The product was purified to obtain a modified cyclotriphosphazene.

[0079] The mass ratio of hexachlorocyclotriphosphazene, xylene, n-propanol, triethylamine and ethanolamine is 11.3:98:12.8:13.7:13.8; the purification operation comprises: washing the reaction product with a saturated sodium bicarbonate aqueous solution until neutral, removing the solvent water by rotary evaporation, adding ethanol 5 times the mass of the reaction product to dissolve, filtering, taking the filtrate, removing the solvent ethanol by rotary evaporation again, and drying at 50°C for 24 hours;

[0080] Step (2), mixing toluene-2,4-diisocyanate and polylactic acid diol in a molar ratio of 3.4:1, adding a catalyst dibutyltin dilaurate of 0.8% by mass of the polylactic acid diol, reacting for 25 minutes in a nitrogen atmosphere at 75°C, adding modified cyclotriphosphazene after the reaction, wherein the amount of modified cyclotriphosphazene added is 9.5% of the total mass of toluene-2,4-diisocyanate and polylactic acid diol, and continuing the reaction at 80°C for 1.5 hours. After the reaction is completed, a polyurethane prepolymer is obtained;

[0081] Step (3), mixing the polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole in a mass ratio of 50:14:0.1, reacting at 155° C. for 2.5 hours, and obtaining a flame retardant compatibilizer after the reaction is completed;

[0082] Wherein, the preparation of epoxidized montmorillonite is the same as that in Example 1;

[0083] Step (4), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips at a mass ratio of 1.1:90:10 at 195° C. for 7 minutes, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn;

[0084] The melt spinning conditions are as follows: spinning temperature is 235°C; spinning speed is 3200 m / min; spinneret aspect ratio is 3.5;

[0085] The polylactic acid POY filament is heated and stretched, cooled, friction twisted, meshed, heat-set, oiled, and wound to obtain a high-strength heat-resistant polylactic acid DTY filament;

[0086] Among them, the temperature of heating and stretching is 125°C and the stretching ratio is 1.5; the D / Y ratio of friction twisting is 1.9; the pressure of meshing is 0.3MPa; and the temperature of heat setting is 92°C.

[0087] Example 5

[0088] This embodiment discloses a method for preparing high-strength heat-resistant polylactic acid DTY filaments, comprising the following steps:

[0089] Step (1), dissolving hexachlorocyclotriphosphazene and xylene, adding n-propanol in a nitrogen atmosphere, heating to 70°C, adding triethylamine dropwise for 20 min, reacting at 70°C for 5 h after the addition is complete, filtering and collecting the filtrate to obtain an intermediate product;

[0090] Ethanolamine was added dropwise to the intermediate product in a nitrogen atmosphere at 70°C for 20 minutes. After the addition was completed, the reaction was continued at 70°C for 5 hours. After the reaction was completed, the upper solvent was removed to obtain a crude reaction product. Xylene in an amount 8 times the mass of the crude reaction product was added for washing. The product was dried at 60°C for 20 hours to obtain a reaction product. The product was purified to obtain a modified cyclotriphosphazene.

[0091] The mass ratio of hexachlorocyclotriphosphazene, xylene, n-propanol, triethylamine and ethanolamine is 11.4:100:13:13.8:14; the purification operation comprises: washing the reaction product with a saturated sodium bicarbonate aqueous solution until neutral, removing the solvent water by rotary evaporation, adding ethanol 8 times the mass of the reaction product to dissolve, filtering, taking the filtrate, removing the solvent ethanol by rotary evaporation again, and drying at 60°C for 20 hours;

[0092] Step (2), mixing toluene-2,4-diisocyanate and polylactic acid diol at a molar ratio of 3.5:1, adding a catalyst dibutyltin dilaurate of 1% by mass of the polylactic acid diol, reacting for 20 minutes at 80°C in a nitrogen atmosphere, adding modified cyclotriphosphazene after the reaction, wherein the amount of modified cyclotriphosphazene added is 10% of the total mass of toluene-2,4-diisocyanate and polylactic acid diol, and continuing the reaction at 85°C for 1 hour, and obtaining a polyurethane prepolymer after the reaction;

[0093] Step (3), mixing the polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole in a mass ratio of 50:15:0.1, reacting at 160° C. for 2 h, and obtaining a flame retardant compatibilizer after the reaction is completed;

[0094] Wherein, the preparation of epoxidized montmorillonite is the same as that in Example 1;

[0095] Step (4), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips at a mass ratio of 1.2:90:10 at 195° C. for 7 minutes, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn;

[0096] The melt spinning conditions are as follows: spinning temperature is 235°C; spinning speed is 3200 m / min; spinneret aspect ratio is 3.5;

[0097] The polylactic acid POY filament is heated and stretched, cooled, friction twisted, meshed, heat-set, oiled, and wound to obtain a high-strength heat-resistant polylactic acid DTY filament;

[0098] Among them, the temperature of heating and stretching is 125°C and the stretching ratio is 1.5; the D / Y ratio of friction twisting is 1.9; the pressure of meshing is 0.3MPa; and the temperature of heat setting is 92°C.

[0099] Comparative Example 1

[0100] This comparative example discloses a method for preparing polylactic acid DTY filaments, comprising the following steps:

[0101] Step (1), dissolving hexachlorocyclotriphosphazene and xylene, adding n-propanol in a nitrogen atmosphere, heating to 65°C, adding triethylamine dropwise for 15 min, reacting at 65°C for 6 h, filtering and collecting the filtrate to obtain an intermediate product;

[0102] Ethanolamine was added dropwise to the intermediate product in a nitrogen atmosphere at 65°C for 15 minutes. After the addition was completed, the reaction was continued at 65°C for 6 hours. After the reaction was completed, the upper solvent was removed to obtain a crude reaction product. Xylene with a mass of 5 times that of the crude reaction product was added for washing. The product was dried at 50°C for 24 hours to obtain a reaction product. The product was purified to obtain a modified cyclotriphosphazene.

[0103] The mass ratio of hexachlorocyclotriphosphazene, xylene, n-propanol, triethylamine and ethanolamine is 11:90:12:13.5:13; the purification operation comprises: washing the reaction product with a saturated sodium bicarbonate aqueous solution until neutral, removing the solvent water by rotary evaporation, adding ethanol 5 times the mass of the reaction product to dissolve, filtering, taking the filtrate, removing the solvent ethanol by rotary evaporation again, and drying at 50°C for 24 hours;

[0104] Step (2), mixing toluene-2,4-diisocyanate and polylactic acid diol in a molar ratio of 3:1, adding a catalyst dibutyltin dilaurate of 0.5% by mass of the polylactic acid diol, reacting for 30 minutes in a nitrogen atmosphere at 70°C, adding modified cyclotriphosphazene after the reaction, wherein the amount of modified cyclotriphosphazene added is 8% of the total mass of toluene-2,4-diisocyanate and polylactic acid diol, and continuing the reaction at 75°C for 2 hours. After the reaction is completed, a flame retardant compatibilizer is obtained;

[0105] Step (3), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips at a mass ratio of 0.8:90:10 at 190° C. for 8 minutes, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn;

[0106] The melt spinning conditions are as follows: spinning temperature is 230°C; spinning speed is 2800 m / min; spinneret aspect ratio is 3;

[0107] The polylactic acid POY filament is heated and stretched, cooled, friction twisted, netted, heat-set, oiled, and wound to obtain the polylactic acid DTY filament;

[0108] Among them, the temperature of heating and stretching is 120°C and the stretching ratio is 1.2; the D / Y ratio of friction twisting is 1.6; the pressure of meshing is 0.1MPa; and the temperature of heat setting is 88°C.

[0109] Comparative Example 2

[0110] This comparative example discloses a method for preparing polylactic acid DTY filaments, comprising the following steps:

[0111] Step (1), mixing toluene-2,4-diisocyanate and polylactic acid diol at a molar ratio of 3:1, adding 0.5% by weight of polylactic acid diol as a catalyst dibutyltin dilaurate, reacting at 75° C. for 2 h in a nitrogen atmosphere, and obtaining a polyurethane prepolymer after the reaction is completed;

[0112] Step (2), mixing the polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole in a mass ratio of 50:10:0.1, reacting at 150° C. for 3 hours, and obtaining a flame retardant compatibilizer after the reaction is completed;

[0113] Wherein, the preparation of epoxidized montmorillonite is the same as that in Example 1;

[0114] Step (3), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips at a mass ratio of 0.8:90:10 at 190° C. for 8 minutes, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn;

[0115] The melt spinning conditions are as follows: spinning temperature is 230°C; spinning speed is 2800 m / min; spinneret aspect ratio is 3;

[0116] The polylactic acid POY filament is heated and stretched, cooled, friction twisted, netted, heat-set, oiled, and wound to obtain the polylactic acid DTY filament;

[0117] Among them, the temperature of heating and stretching is 120°C and the stretching ratio is 1.2; the D / Y ratio of friction twisting is 1.6; the pressure of meshing is 0.1MPa; and the temperature of heat setting is 88°C.

[0118] Comparative Example 3

[0119] This comparative example discloses a method for preparing polylactic acid DTY filaments, comprising the following steps:

[0120] Montmorillonite, polylactic acid chips, and polybutylene terephthalate-adipate chips were mixed at a mass ratio of 0.4:90:10 at 190° C. for 8 min, melt-spun, cooled, oiled, and wound to obtain polylactic acid POY yarns;

[0121] The melt spinning conditions are as follows: spinning temperature is 230°C; spinning speed is 2800 m / min; spinneret aspect ratio is 3;

[0122] The polylactic acid POY filament is heated and stretched, cooled, friction twisted, netted, heat-set, oiled, and wound to obtain the polylactic acid DTY filament;

[0123] Among them, the temperature of heating and stretching is 120°C and the stretching ratio is 1.2; the D / Y ratio of friction twisting is 1.6; the pressure of meshing is 0.1MPa; and the temperature of heat setting is 88°C.

[0124] In the above embodiments and comparative examples:

[0125] Hexachlorocyclotriphosphazene comes from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 940-71-6; toluene-2,4-diisocyanate comes from Shanghai MacLean Biochemical Technology Co., Ltd., CAS No.: 584-84-9; polylactic acid diol comes from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., Mn=1000; 2-ethyl-4-methylimidazole comes from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 931-36-2; montmorillonite is sodium montmorillonite from Nanocor, USA, with an ion exchange capacity of 100 meq / 100g; polylactic acid chips are fiber-grade polylactic acid chips from Nature Works, model 6202D, with a viscosity-average molecular weight of 51000; polybutylene terephthalate-adipate chips are PBAT chips from Blue Mountain Tunhe Polyester Co., Ltd., specification TH801T, with an intrinsic viscosity of 1.049.

[0126] The comprehensive performance test was conducted on the polylactic acid DTY filaments prepared in Examples 1-5 and Comparative Examples 1-3. The specific test results are shown in Table 1:

[0127] Table 1

[0128] Breaking strength (cN / dtex) Elongation at break (%) Hot air shrinkage (%) Limiting oxygen index LOI (%) Example 1 ＞2.4 41 2.5 33.1 Example 2 ＞2.4 42 2.4 33.3 Example 3 ＞2.4 44 2.4 33.5 Example 4 ＞2.4 45 2.3 33.6 Example 5 ＞2.4 46 2.3 33.8 Comparative Example 1 ＞2.4 53 4.1 31.1 Comparative Example 2 ＞2.4 41 3.3 32.3 Comparative Example 3 ＜2.4 28 4.8 29.7

[0129] The testing of various indicators in Table 1 is based on the following standards: breaking strength and breaking elongation are measured with reference to GB / T14344-2008 "Test method for tensile properties of chemical fiber filaments"; breaking elongation is measured with reference to GB / T14344-2008 "Test method for tensile properties of chemical fiber filaments"; hot air shrinkage is measured with reference to GB / T6505-2008 "Test method for thermal shrinkage of chemical fiber filaments"; limiting oxygen index is measured with reference to GB / T5454-1997 "Oxygen index method for textile combustion performance test".

[0130] It can be seen from the test results in Table 1 that the polylactic acid DTY filaments prepared by the present invention have good heat resistance, excellent mechanical properties, and improved flame retardancy.

[0131] The invention uses a polyurethane prepolymer containing a polylactic acid segment and a flame-retardant cyclotriphosphazene structure to react with epoxidized montmorillonite under an imidazole catalyst condition to generate an oxazolidinone structure to prepare a flame-retardant compatibilizer. The oxazolidinone five-membered ring structure has a very high thermal decomposition temperature and excellent heat resistance, and can cooperate with the inorganic filler montmorillonite and the flame-retardant functionalized polyurethane prepolymer to improve the heat resistance and flame retardancy of a polylactic acid substrate. Since the flame-retardant compatibilizer contains an incompletely reacted isocyanate functional group, the flame-retardant compatibilizer can react with the terminal hydroxyl group and / or terminal carboxyl group of polylactic acid and polybutylene terephthalate-adipate in a melt mixing process to generate a carbamate bond, which plays a role of compatibilization, improves the entanglement degree between polymer matrix molecular chains, thereby improving the dispersibility and compatibility of each component in the polylactic acid matrix, and improving the mechanical properties of the polylactic acid DTY filament.

[0132] The flame retardant compatibilizer of Comparative Example 1 does not contain epoxidized montmorillonite, lacks the effect of improving the heat resistance and flame retardancy of the polylactic acid filament by the inorganic filler montmorillonite with good heat resistance and flame retardancy, and because the compatibilizer contains only polyurethane prepolymer and does not generate the oxazolidinone five-membered ring structure, the elongation at break of Comparative Example 1 is improved compared with that of the embodiment, but the heat resistance and flame retardancy are lower than those of the embodiment;

[0133] In the flame-retardant compatibilizer of Comparative Example 2, the polyurethane prepolymer does not have modified cyclotriphosphazene added, and lacks the effect of the cyclotriphosphazene structure on improving the flame retardancy and heat resistance of the material, so the heat resistance and flame retardancy of Comparative Example 2 are lower than those of the embodiment;

[0134] The montmorillonite surface in Comparative Example 3 is not modified, and no polyurethane prepolymer is added. The compatibility of montmorillonite with the matrix material is poor, and the dispersibility is poor, which affects the mechanical properties of the fiber. In addition, there is a lack of the polyurethane prepolymer to improve the heat resistance and flame retardancy of the matrix material. Therefore, the mechanical properties, heat resistance and flame retardancy of Comparative Example 3 are all lower than those of the embodiments.

[0135] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing high-strength heat-resistant polylactic acid DTY filament, characterized in that: The following steps are involved: Step (1), by weight, 11-11.4 parts of hexachlorocyclotriphosphazene and 90-100 parts of xylene are mixed and dissolved, 12-13 parts of n-propanol are added in a nitrogen atmosphere, and 13.5-13.8 parts of triethylamine are added dropwise. After the addition is completed, the mixture is reacted at a temperature of 65-70° C. for 5-6 hours. After the reaction is completed, the mixture is filtered and the filtrate is taken to obtain an intermediate product; 13-14 parts of ethanolamine are added dropwise to the intermediate product. After the addition is completed, the reaction is continued at 65-70° C. for 5-6 hours. After the reaction is completed, the modified cyclotriphosphazene is purified to obtain the modified cyclotriphosphazene. Toluene-2,4-diisocyanate and polylactic acid diol are mixed, a catalyst is added, and the mixture is reacted. After the reaction is completed, modified cyclotriphosphazene is added and the mixture is continued to react. After the reaction is completed, a polyurethane prepolymer is obtained. Step (2), epichlorohydrin and methanol are mixed and dissolved, hexadecyl dimethyl tertiary amine is added, and the mixture is stirred and reacted at 60-65° C. for 6-7 hours. After the reaction is completed, the solvent methanol is removed by rotary evaporation, and the mixture is washed to obtain an epoxy intercalation agent; Wherein, the molar ratio of epichlorohydrin to hexadecyl dimethyl tertiary amine is 1.1-1.2:1; Mixing montmorillonite with water, ultrasonically dispersing, adding epoxy intercalant, reacting at 60-70°C for 6-7h, centrifuging, filtering, washing, drying, grinding and sieving to obtain epoxidized montmorillonite; Wherein, the mass ratio of montmorillonite to epoxy intercalant is 1:1.25-1.3; The polyurethane prepolymer, epoxidized montmorillonite and 2-ethyl-4-methylimidazole are mixed and reacted, and after the reaction is completed, a flame retardant compatibilizer is obtained; Step (3), mixing the flame retardant compatibilizer, polylactic acid chips, and polybutylene terephthalate adipate chips, melt spinning, cooling, oiling, and winding to obtain polylactic acid POY yarn; The polylactic acid POY filament is heated and stretched, cooled, frictionally twisted, meshed, heat-set, oiled, and wound to obtain high-strength and heat-resistant polylactic acid DTY filament.

2. The method for preparing high-strength heat-resistant polylactic acid DTY filament according to claim 1, characterized in that: In the step (1), the molar ratio of toluene-2,4-diisocyanate to polylactic acid diol is 3-3.5:1; the amount of modified cyclotriphosphazene added is 8-10% of the total mass of toluene-2,4-diisocyanate and polylactic acid diol; the reaction conditions are: reacting at a temperature of 70-80°C for 20-30 minutes in a nitrogen atmosphere; and the continued reaction conditions are: continuing the reaction at a temperature of 75-85°C for 1-2 hours.

3. The method for preparing high-strength heat-resistant polylactic acid DTY filament according to claim 1, characterized in that: In the step (2), the mass ratio of the polyurethane prepolymer, the epoxidized montmorillonite and the 2-ethyl-4-methylimidazole is 50:10-15:0.1; and the reaction conditions are: reacting at a temperature of 150-160° C. for 2-3 hours.

4. The method for preparing high-strength heat-resistant polylactic acid DTY filament according to claim 1, characterized in that: In the step (3), the mass ratio of the flame retardant compatibilizer, the polylactic acid slices, and the polybutylene terephthalate-adipate slices is 0.8-1.2:90:

10.

5. The method for preparing high-strength heat-resistant polylactic acid DTY filament according to claim 1, characterized in that: In the step (3), the mixing conditions are: mixing at a temperature of 190-195°C for 7-8 minutes; the melt spinning conditions are: spinning temperature of 230-235°C; spinning speed of 2800-3200 m / min; spinneret aspect ratio of 3-3.5; heating and stretching temperature of 120-125°C, stretching multiple of 1.2-1.5; friction twisting D / Y ratio of 1.6-1.9; netting pressure of 0.1-0.3 MPa; heat setting temperature of 88-92°C.

6. A high-strength heat-resistant polylactic acid DTY filament prepared by the method for preparing high-strength heat-resistant polylactic acid DTY filament as claimed in any one of claims 1 to 5.

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