A kind of polyester low-elastic yarn and its preparation process

Abstract

The present application relates to a polyester low-elastic yarn and a preparation process thereof, comprising the following components by weight: 60-80 parts of modified polyester; 10-16 parts of modified chitosan; 10-16 parts of sodium phytate; 0.5-1.5 parts of a cross-linking agent; 2-4 parts of a flame retardant additive; the modified chitosan is used as a cationic coating, the sodium phytate is used as an anionic coating, and the polyester fiber is self-assembled layer by layer; the modified polyester is obtained by surface grafting casein on the polyester fiber. The polyester low-elastic yarn prepared by the present application has good flame retardant properties, no droplets after burning; after multiple washings, it still has good flame retardant properties.

Description

Technical Field

[0001] The present application relates to the field of fiber spinning, and in particular to a polyester low-elastic yarn and a preparation process thereof. Background Art

[0002] Polyester low-elastic yarn, also known as DTY, is made by stretching and false-twisting POY yarn on a false-twist texturing machine. Polyester low-elastic yarn is often used as a raw material for making clothing fabrics due to its high bulkiness, comfortable feel, and soft luster.

[0003] However, polyester is very flammable. When in contact with a high-temperature heat source, polyester absorbs heat and undergoes a thermal cracking reaction to generate flammable gases. The flammable gases trigger combustion, which again promotes the thermal cracking of polyester fibers in the area, thus forming a new round of combustion cycle. Therefore, clothing made from polyester low-elastic yarn is prone to safety hazards. In traditional processes, polyester is often finished by adding flame retardants in the post-finishing process, but the polyester produced in this way has poor water washing fastness and loses its flame retardant effect after several washes. Summary of the invention

[0004] In order to improve the flame retardancy and washing fastness of polyester, the present application provides a polyester low-elastic yarn.

[0005] In the first aspect, a polyester low-elastic yarn is characterized in that it includes the following components in parts by weight: 60-80 parts of modified polyester; 10-16 parts of modified chitosan; 10-16 parts of sodium phytate; 0.5-1.5 parts of a cross-linking agent; and 2-4 parts of a flame retardant additive; the modified chitosan is used as a cationic coating, and the sodium phytate is used as an anionic coating to perform layer-by-layer self-assembly on the polyester fiber; the modified polyester is obtained by surface grafting casein onto the polyester fiber.

[0006] By adopting the above technical solution, chitosan will form a porous foam char layer when heated, and chitosan is rich in nitrogen. When decomposed by heat, it will release non-flammable gases such as ammonia in the carbon layer, reducing the further reaction of free radicals in the combustion zone, so it can effectively reduce the combustion of polyester. Sodium phytate is selected as the anion coating. Phytic acid has a high content of phosphorus. Under acidic conditions, it can react with metal cations that can catalyze carbon aging to form a stable complex that is not easy to hydrolyze, and has a good flame retardant effect. When sodium phytate is used as an acid source in combination with hydroxypropyl chitosan, it can form an IFR system and produce a good PN effect, which has a rapid flame retardant effect. The use of a cross-linking agent forms an interwoven spatial network structure between the modified chitosan, polyester fiber, and flame retardant additives, which improves the flame retardant properties and water washing fastness of polyester. By grafting casein on the surface of polyester fibers, casein is rich in phosphorus and nitrogen elements, and will be converted into an acid source when heated, catalyzing the dehydration of polyester and chitosan into carbon, forming a multi-level carbon layer, and slowing down the burning rate of the fabric; the surface viscosity of the polyester fiber after casein grafting is improved, which improves the bonding strength between the polyester fiber and the anionic and cationic coatings, and improves the water washing fastness of the polyester.

[0007] Preferably, the cross-linking agent is hypophosphorous acid.

[0008] By adopting the above technical solution, the flame retardant properties and washing fastness of the polyester fiber after cross-linking with hypophosphorous acid are further improved.

[0009] Preferably, the flame retardant additive is fumed silica.

[0010] By adopting the above technical scheme, during the combustion process, silica can improve the quality and strength of the carbon layer and play a flame retardant role; the surface of the polyester modified by casein has more active hydroxyl groups, which can form hydrogen bonds with the hydroxyl groups on the surface of silica, thereby improving the poor compatibility between silica and polyester; chitosan can also carry silica particles to improve the dispersibility and compatibility of silica; after adding silica, the silicon element can reduce the surface free energy of the polyester surface and improve the hydrophobicity of the polyester surface, and more chemical bonds are formed between silica, chitosan and polyester, thereby further improving the water washing fastness and flame retardant properties of polyester.

[0011] Preferably, the modified polyester comprises the following components by weight: 100-120 parts of polyester fiber; 8-12 parts of casein; and 1.5-3.5 parts of graft crosslinking agent.

[0012] By adopting the above technical scheme, the various components of polyester modification are optimized, the grafting effect of casein is improved, and the flame retardant properties and washing fastness of polyester fibers are further improved.

[0013] Preferably, the preparation process of the modified polyester comprises the following steps:

[0014] Take casein and dissolve it in sodium hydroxide solution, add polyester fiber and graft crosslinking agent and mix, adjust pH to 7-8 with hydrochloric acid, adjust temperature to 60-70℃, react for 15-35min, take out and dry to obtain modified polyester.

[0015] By adopting the above technical solution, under alkaline conditions, the solubility of casein is better, and the sodium hydroxide solution will etch the surface of the polyester, increasing the active groups on the surface of the polyester, thereby increasing the grafting rate of casein and polyester.

[0016] Preferably, the modified chitosan is obtained by hydroxypropylating chitosan and then cross-linking it with sodium tripolyphosphate.

[0017] By adopting the above technical scheme, after chitosan is hydroxypropylated, the activity of the surface groups such as hydroxyl and amino groups on the surface of chitosan is improved, thereby improving the water solubility of chitosan and the bonding strength with sodium phytate, and improving the flame retardancy and water washing fastness of polyester; sodium tripolyphosphate is used as an ionic crosslinking agent to carry out phosphorylation modification of hydroxypropylated chitosan; sodium tripolyphosphate has a high phosphorus content, and after the phosphate group is introduced into chitosan, the water solubility and carbon-forming performance of chitosan are improved, and the flame retardancy of polyester is improved.

[0018] Preferably, the modified chitosan comprises the following components in parts by weight: 10 parts of chitosan, 10-20 parts of sodium tripolyphosphate, 1.5-2.5 parts of tetramethylammonium hydroxide, and 14-18 parts of propylene oxide.

[0019] By adopting the above technical scheme and optimizing the component ratio of modified chitosan, the prepared cationic coating has better flame retardancy, and the flame retardancy and water washing fastness of polyester are further improved.

[0020] Preferably, the preparation method of the modified chitosan comprises the following steps:

[0021] Hydroxypropylation: Mix chitosan, sodium hydroxide solution and isopropanol, add tetramethylammonium hydroxide and propylene oxide, stir for 1-1.5h, heat to 75-85°C, stir for 6-7h, neutralize with hydrochloric acid solution to pH 7-7.6, precipitate and filter to obtain hydroxypropylated chitosan;

[0022] Ionic modification: hydroxypropylated chitosan is dissolved in water to obtain a hydroxypropylated chitosan solution, sodium tripolyphosphate is dissolved in water to obtain a sodium tripolyphosphate solution, the two solutions are mixed, and stirred at 2000-3000 rpm for 2-4 hours to obtain modified chitosan.

[0023] By adopting the above technical scheme, an isopropanol-sodium hydroxide system is prepared to improve the solubility of chitosan and the activity of active groups, and the hydroxypropyl degree of chitosan is improved; propylene oxide reacts with the carboxyl groups on the hydroxypropyl groups of chitosan to form a short branched structure, and a carboxypropyl group is introduced. Controlling the reaction time and temperature can increase the degree of substitution of the hydroxypropyl groups in the hydroxypropyl chitosan; and the reaction parameters of the ion modification stage are optimized to increase the modified chitosan with a higher degree of ion crosslinking, thereby improving the flame retardancy and water washing fastness of polyester.

[0024] In a second aspect, a process for preparing polyester low-elastic yarn is provided, which is prepared by the following steps:

[0025] Preparation of polyester low-elastic yarn: pre-crystallization, melt spinning, drawing, and false twisting of the modified polyester to obtain the modified polyester low-elastic yarn; layer-by-layer self-assembly: modified chitosan is dissolved in water to obtain a modified chitosan solution, sodium phytate is dissolved in water to obtain a sodium phytate solution, and a cross-linking agent is dissolved in water to obtain a cross-linking agent solution; the modified polyester low-elastic yarn is immersed in deionized water, then immersed in the modified chitosan solution, and finally immersed in the sodium phytate solution. Washing and drying are one cycle. After 15-25 cycles in total, it is immersed in the cross-linking agent solution, and a flame retardant additive is added and stirred for 20-30 minutes. The polyester low-elastic yarn is taken out, washed and dried to obtain the polyester low-elastic yarn.

[0026] By adopting the above technical solution and optimizing the number of assembled layers, the polyester low-elastic yarn has good flame retardancy and water washing fastness while maintaining the performance of the polyester material.

[0027] In summary, this application has the following beneficial effects:

[0028] 1. By grafting casein onto the surface of polyester, the viscosity of the polyester surface is improved and it has more active groups, thereby improving the bonding strength between the polyester surface and the anionic and cationic coatings; the multi-layer intumescent flame retardant formed between casein and chitosan has a synergistic flame retardant effect in terms of gas phase flame retardancy, foaming flame retardancy and other flame retardant effects, thereby improving the flame retardant properties of polyester low-elastic yarn.

[0029] 2. By modifying chitosan with hydroxypropylation and then using sodium tripolyphosphate for ion cross-linking, the adhesion of chitosan on the polyester surface and the bonding strength with other substances are improved, the performance of chitosan in catalytic decarboxylation to carbon is improved, and the flame retardancy of polyester is improved. DETAILED DESCRIPTION

[0030] The raw materials used in the examples and preparation examples are commercially available and described in detail.

[0031] Preparation examples of raw materials and / or intermediates

[0032] Preparation of modified chitosan

[0033] Preparation Example 1-1, a modified chitosan, is prepared by the following method:

[0034] Hydroxypropylation: 10 g chitosan, 300 mL 1 mol / L sodium hydroxide solution and 200 mL isopropanol were mixed, 2 g tetramethylammonium hydroxide and 16 g propylene oxide were added, stirred for 1.25 h, heated to 80 °C, stirred for another 6.5 h, neutralized with 1 mol / L hydrochloric acid solution to pH 7.3, 500 mL acetone was added for precipitation for 2 h, and hydroxypropyl chitosan was obtained by filtration;

[0035] Ionic modification: Hydroxypropyl chitosan was dissolved in 500 mL of water to obtain a carboxylated chitosan solution, 15 g of sodium tripolyphosphate was dissolved in 500 mL of water to obtain a sodium tripolyphosphate solution, the two solutions were mixed, and stirred at 2500 rpm for 3 h to obtain modified chitosan.

[0036] Preparation Example 1-2, a modified chitosan, prepared by the following method:

[0037] Hydroxypropylation: 10 g chitosan, 300 mL 1 mol / L sodium hydroxide solution and 200 mL isopropanol were mixed, 2.5 g tetramethylammonium hydroxide and 18 g propylene oxide were added, stirred for 1.5 h, heated to 85 °C, stirred for another 6 h, neutralized with 1 mol / L hydrochloric acid solution to pH 7, 500 mL acetone was added for precipitation for 2 h, and hydroxypropyl chitosan was obtained by filtration;

[0038] Ionic modification: Hydroxypropyl chitosan was dissolved in 500 mL of water to obtain a carboxylated chitosan solution. 20 g of sodium tripolyphosphate was dissolved in 500 mL of water to obtain a sodium tripolyphosphate solution. The two solutions were mixed and stirred at 3000 rpm for 2 h to obtain modified chitosan.

[0039] Preparation Example 1-3, a modified chitosan, is prepared by the following method:

[0040] Hydroxypropylation: 10 g chitosan, 300 mL 1 mol / L sodium hydroxide solution and 200 mL isopropanol were mixed, 1.5 g tetramethylammonium hydroxide and 14 g propylene oxide were added, stirred for 1 h, heated to 75 °C, stirred for another 7 h, neutralized with 1 mol / L hydrochloric acid solution to pH 7.6, 500 mL acetone was added for precipitation for 2 h, and hydroxypropyl chitosan was obtained by filtration;

[0041] Ionic modification: Hydroxypropyl chitosan was dissolved in 500 mL of water to obtain a carboxylated chitosan solution, 10 g of sodium tripolyphosphate was dissolved in 500 mL of water to obtain a sodium tripolyphosphate solution, the two solutions were mixed, and stirred at 2000 rpm for 4 h to obtain modified chitosan.

[0042] Preparation Example 1-4, a modified chitosan, is different from Preparation Example 1-1 in that in the hydroxypropylation reaction, the temperature is raised to 100°C and then stirred for 6 hours. (That is, the heating temperature is changed from 85°C to 100°C)

[0043] Preparation Example 1-5, a modified chitosan, is different from Preparation Example 1-1 in that in the hydroxypropylation reaction, the temperature is raised to 60°C and then stirred for 6 hours. (That is, the heating temperature is changed from 85°C to 60°C)

[0044] Preparation Example 1-6 is a modified chitosan, which differs from Preparation Example 1-1 in that in the ion modification step, sodium tripolyphosphate is replaced by sodium hexametaphosphate.

[0045] Preparation Example 1-7 is a modified chitosan, which is different from Preparation Example 1-1 in that the chitosan does not undergo an ion modification step.

[0046] Preparation Example 1-8, a modified chitosan, is prepared by the following steps: dissolving chitosan in 500 mL of acetic acid to obtain a chitosan solution, dissolving 15 g of sodium tripolyphosphate in 500 mL of water to obtain a sodium tripolyphosphate solution, mixing the two solutions, and stirring at 2500 rpm for 3 hours to obtain a modified chitosan. (i.e., not modified by hydroxypropyl)

[0047] Preparation of modified polyester fiber

[0048] Preparation Example 2-1, a modified polyester, is prepared by the following steps:

[0049] Take 10g of casein and dissolve it in 1L of 2.5mol / L sodium hydroxide solution, add 110g of polyester fiber and 2.5 parts of glutaraldehyde and mix evenly, adjust the pH to 7.5 with 1mol / L hydrochloric acid solution, adjust the temperature to 65℃, react for 25min, take it out, and dry it in an oven at 80℃ for 1h to obtain modified polyester.

[0050] Preparation Example 2-2, a modified polyester, is prepared by the following steps:

[0051] Take 12g of casein and dissolve it in 1L of 2.5mol / L sodium hydroxide solution, add 120g of polyester fiber and 3.5 parts of glutaraldehyde and mix evenly, adjust the pH to 7 with 1mol / L hydrochloric acid solution, adjust the temperature to 70℃, react for 15min, take it out, and dry it in an oven at 80℃ for 1h to obtain modified polyester.

[0052] Preparation Example 2-3, a modified polyester, is prepared by the following steps:

[0053] Take 8g of casein and dissolve it in 1L of 2.5mol / L sodium hydroxide solution, add 100g of polyester fiber and 1.5 parts of glutaraldehyde and mix evenly, adjust the pH to 8 with 1mol / L hydrochloric acid solution, adjust the temperature to 60℃, react for 35min, take it out, and dry it in an oven at 80℃ for 1h to obtain modified polyester.

[0054] Preparation Example 2-4, a method for preparing modified polyester, is different from Preparation Example 2-1 in that the mass of casein is 20 g, that is, the weight parts of casein are 20 parts.

[0055] Preparation Example 2-5, a modified polyester, is different from Preparation Example 2-1 in that the mass of casein is 2 g, that is, the weight portion of casein is 2 g.

[0056] Preparation Example 2-6, a modified polyester, is different from Preparation Example 2-1 in that casein is replaced by an equal amount of wool protein.

[0057] Preparation Example 2-7, a modified polyester, is prepared by the following steps:

[0058] 110 g of polyester was put into 3 kg of 5 mol / L sodium hydroxide solution, the temperature was adjusted to 75° C., stirred for 1.5 h, taken out and rinsed twice with cold water, and then dried in an oven at 80° C. to obtain the modified polyester.

[0059] Example

[0060] Embodiment 1, a polyester low-elastic yarn, is prepared by the following steps:

[0061] Preparation of raw material POY yarn: melt extrusion, cooling, oiling and winding of modified polyester to obtain POY fiber; the extrusion temperature is 280° C., the oiling rate is 0.3wt%, and the winding speed is 2000m / min;

[0062] Preparation of modified polyester low-elastic yarn: POY fiber is cut, passed through the first roller, the first hot box, the cooling plate, the false twister, the second roller, the grid, the shaping hot box, the third roller, oiled, and wound to obtain the modified polyester low-elastic yarn; the temperature of the first hot box is 170°C, the temperature of the second hot box is 120°C, the traction ratio is 1.6, the stretching multiple is 1.6, the shaping overfeed rate is 5%, and the winding speed is 2000m / min;

[0063] Layer-by-layer self-assembly: 13 g of modified chitosan was dissolved in 650 mL of water to obtain a modified chitosan solution, 13 g of sodium phytate was dissolved in 650 mL of water to obtain a sodium phytate solution, and 1 g of hypophosphorous acid was dissolved in 500 mL of water to obtain a crosslinker solution; 70 g of modified polyester low-elastic yarn was immersed in deionized water for 1 min, then immersed in the modified chitosan solution for 10 min, and finally immersed in the sodium phytate solution for 10 min. Washing and drying were one cycle, and a total of 20 cycles were performed. Then, the yarn was immersed in the crosslinker solution, 3 g of fumed silica was added, and the yarn was stirred for 25 min. The yarn was taken out, washed, and dried to obtain polyester low-elastic yarn.

[0064] The modified chitosan comes from Preparation Example 1-1, and the modified polyester comes from Preparation Example 2-1.

[0065] Embodiment 2, a polyester low-elastic yarn, is prepared by the following steps:

[0066] Preparation of raw material POY yarn: melt-extrude, cool, oil and wind the modified polyester to obtain POY fiber; the process parameters are the same as those in Example 1;

[0067] Preparation of modified polyester low-elastic yarn: POY fiber is cut, passed through a first roller, a first hot box, a cooling plate, a false twister, a second roller, a grid, a shaping hot box, a third roller, oiled, and wound to obtain modified polyester low-elastic yarn; the process parameters are the same as those in Example 1;

[0068] Layer-by-layer self-assembly: 16 g of modified chitosan was dissolved in 650 mL of water to obtain a modified chitosan solution, 10 g of sodium phytate was dissolved in 650 mL of water to obtain a sodium phytate solution, and 1.5 g of hypophosphorous acid was dissolved in 500 mL of water to obtain a crosslinker solution; 80 g of modified polyester low-elastic yarn was immersed in deionized water for 1 min, then immersed in the modified chitosan solution for 10 min, and finally immersed in the sodium phytate solution for 10 min. Washing and drying were one cycle, and a total of 15 cycles were performed. Then, the yarn was immersed in the crosslinker solution, 4 g of fumed silica was added, and the yarn was stirred for 20 min. The yarn was taken out, washed, and dried to obtain polyester low-elastic yarn.

[0069] The modified chitosan comes from Preparation Example 1-2, and the modified polyester comes from Preparation Example 2-2.

[0070] Embodiment 3, a polyester low-elastic yarn, is prepared by the following steps:

[0071] Preparation of raw material POY yarn: melt-extrude, cool, oil and wind the modified polyester to obtain POY fiber; the process parameters are the same as those in Example 1;

[0072] Preparation of modified polyester low-elastic yarn: POY fiber is cut, passed through a first roller, a first hot box, a cooling plate, a false twister, a second roller, a grid, a shaping hot box, a third roller, oiled, and wound to obtain modified polyester low-elastic yarn; the process parameters are the same as those in Example 1;

[0073] Layer-by-layer self-assembly: 16 g of modified chitosan was dissolved in 650 mL of water to obtain a modified chitosan solution, 10 g of sodium phytate was dissolved in 650 mL of water to obtain a sodium phytate solution, and 0.5 g of hypophosphorous acid was dissolved in 500 mL of water to obtain a crosslinker solution; 80 g of modified polyester low-elastic yarn was immersed in deionized water for 1 min, then immersed in the modified chitosan solution for 10 min, and finally immersed in the sodium phytate solution for 10 min. Washing and drying were one cycle, and a total of 25 cycles were performed. Then, the yarn was immersed in the crosslinker solution, 2 g of fumed silica was added, and the yarn was stirred for 30 min. The yarn was taken out, washed, and dried to obtain polyester low-elastic yarn.

[0074] The modified chitosan is from Preparation Example 1-3, and the modified polyester is from Preparation Example 2-3.

[0075] Example 4, a process for preparing polyester low-elastic yarn, is different from Example 1 in that the modified chitosan is derived from Preparation Example 1-4.

[0076] Example 5, a process for preparing polyester low-elastic yarn, is different from Example 1 in that the modified chitosan is derived from Preparation Example 1-5.

[0077] Example 6, a process for preparing polyester low-elastic yarn, is different from Example 1 in that the modified chitosan is derived from Preparation Example 1-6.

[0078] Example 7, a process for preparing polyester low-elastic yarn, is different from Example 1 in that the modified chitosan is derived from Preparation Example 1-7.

[0079] Example 8, a process for preparing polyester low-elastic yarn, is different from Example 1 in that the modified chitosan is derived from Preparation Example 1-8.

[0080] Example 9, a process for preparing polyester low-elastic yarn, is different from Example 1 in that the modified polyester comes from Preparation Example 2-4.

[0081] Example 10, a process for preparing polyester low-elastic yarn, is different from Example 1 in that the modified polyester comes from Preparation Example 2-5.

[0082] Example 11, a preparation process of polyester low-elastic yarn, is different from Example 1 in that the number of cycles is 30 times.

[0083] Example 12, a process for preparing polyester low-elastic yarn, is different from Example 1 in that the number of cycles is 10.

[0084] Comparative Example

[0085] Comparative Example 1 is a process for preparing a polyester low-elastic yarn, which is different from Example 1 in that the modified polyester comes from Preparation Examples 2-6.

[0086] Comparative Example 2 is a process for preparing a polyester low-elastic yarn, which is different from Example 1 in that the modified polyester comes from Preparation Example 2-7.

[0087] Comparative Example 3 is a process for preparing polyester low-elastic yarn, which is different from Example 1 in that hypophosphorous acid is replaced by an equal amount of deionized water.

[0088] Comparative Example 4 is a process for preparing polyester low-elastic yarn, which is different from Example 1 in that the fumed silica is replaced by an equal amount of phosphatidic acid.

[0089] Comparative Example 5, a polyester low-elastic yarn, is prepared by the following preparation steps:

[0090] Pretreatment: 110 g of polyester fiber was added into 3 kg of 3 mol / L sodium hydroxide solution, the temperature was adjusted to 80°C and soaked for 60 min, and then washed and dried to obtain pretreated polyester fiber;

[0091] Surface modification: taking the pretreated polyester fiber, immersing it in a hexaaminocyclotriphosphazene solution for 5 minutes, taking it out and wringing it dry, washing it with deionized water for 4 times, and obtaining a substrate modified with a positively charged electrolyte layer; placing the substrate modified with a positively charged electrolyte layer in a sodium alginate solution and immersing it for 5 minutes, taking it out and wringing it dry, and washing it with deionized water for 4 times as one cycle; a total of 20 cycles were performed to obtain a surface-modified polyester fiber;

[0092] Cross-linking: Put the surface-modified polyester fiber into 500 mL of distilled water, stir magnetically at room temperature, then add 5 g of catalyst 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride, stir at 4°C for 1 hour, wash and dry to obtain a polyester low-elastic yarn.

[0093] Performance Test The polyester low-elastic yarns of Examples 1-12 and Comparative Examples 1-5 were taken, and untreated polyester was set as a blank control. Performance tests were performed on samples that were not washed and machine washed 10 times. Four groups were tested in parallel and the average value was taken.

[0094] Test 1: Limiting oxygen index test. The limiting oxygen index test was carried out in accordance with GB / T5454-1997. The test results are shown in Table 1.

[0095] Test 2: Vertical burning performance, tested in accordance with GB / T 5455-1997 “Vertical method for testing burning performance of textiles”. The test results are shown in Table 1.

[0096] Table 1: Test results

[0097]

[0098] With reference to Examples 1-8 and in combination with Table 1, it can be seen that the degree of hydroxypropyl substitution in chitosan and whether chitosan has been ionically crosslinked have an effect on the flame retardant properties and water washing fastness of polyester low-elastic yarn. The reason is that after chitosan is modified by hydroxypropyl and ion crosslinking agent, its surface presents more positive charges and is more firmly bonded to the polyester surface; its surface also presents more active groups, and the bond between the polyester fiber and the fumed titanium dioxide is also more firmly; its internal phosphorus content is higher, and the synergistic flame retardant effect with casein is more obvious, and a flame retardant carbon layer with larger mass and richer layers can be formed more quickly, thereby improving the flame retardant properties and water washing fastness of polyester low-elastic yarn.

[0099] With reference to Example 1, Examples 9-10 and Comparative Examples 1-2, combined with Table 1, it can be seen that the flame retardant properties and water washing fastness of polyester fiber modified by casein are better, because there is a synergistic flame retardant effect between casein and modified chitosan, and the sticky surface formed after cross-linking between casein and polyester improves the bonding fastness between fumed silica and cationic and anionic coatings and polyester. Further, fumed silica can improve the hydrophobicity of the polyester surface, which in turn improves the water washing fastness of polyester. When the amount of casein added is too much, the flame retardant properties of the modified polyester fiber decrease, because casein itself is not easy to form a film. When the quality of casein is too high, it affects the bonding of polyester fiber with anionic and cationic coatings, thus causing a decrease in flame retardant properties.

[0100] With reference to Example 1, Comparative Examples 3-5 and the blank control, and in combination with Table 1, it can be seen that the polyester low-elastic yarn prepared in the present application has good flame retardant properties, and can still maintain good flame retardant properties after multiple washings. The reason is that: the anionic and cationic coatings of the present application and the casein-modified polyester can form a complex spatial network structure, which greatly improves the bonding strength between the anionic and cationic coatings and the polyester, and the flame retardant carbon layer formed by the structure when burning is better, and the release of non-combustible gas is faster, so it has a better flame retardant effect.

[0101] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A polyester low-elastic yarn, characterized in that: The invention comprises the following components in parts by weight: 60-80 parts of modified polyester; 10-16 parts of modified chitosan; 10-16 parts of sodium phytate; 0.5-1.5 parts of cross-linking agent; 2-4 parts of flame retardant additive; The modified polyester is obtained by grafting casein onto the surface of polyester fiber; The modified chitosan is obtained by hydroxypropylating chitosan and then cross-linking it with sodium tripolyphosphate; The cross-linking agent is hypophosphorous acid; The flame retardant additive is fumed silica; The preparation process of the polyester low-elastic yarn is prepared by the following steps: Preparation of raw material POY yarn: melt extrusion, cooling, oiling and winding of modified polyester to obtain POY fiber; Preparation of modified polyester low-elastic yarn: POY fiber is cut, passed through a first roller, a first hot box, a cooling plate, a false twister, a second roller, a grid, a shaping hot box, a third roller, oiled, and wound to obtain modified polyester low-elastic yarn; Layer-by-layer self-assembly: take modified chitosan and dissolve it in water to obtain a modified chitosan solution, take sodium phytate and dissolve it in water to obtain a sodium phytate solution, take a cross-linking agent and dissolve it in water to obtain a cross-linking agent solution; take modified polyester low-elastic yarn, immerse it in deionized water, then immerse it in the modified chitosan solution, and finally immerse it in the sodium phytate solution. Washing and drying are one cycle. After 15-25 cycles in total, immerse it in the cross-linking agent solution, add a flame retardant additive and stir for 20-30 minutes, take it out, wash and dry it to obtain polyester low-elastic yarn.

2. The polyester low-elastic yarn according to claim 1, characterized in that: The modified polyester comprises the following components by weight: 100-120 parts of polyester fiber; 8-12 parts of casein; and 1.5-3.5 parts of a graft crosslinking agent.

3. The polyester low-elastic yarn according to claim 1, characterized in that: The preparation process of the modified polyester comprises the following steps: Take casein and dissolve it in sodium hydroxide solution, add polyester fiber and graft crosslinking agent and mix, adjust pH to 7-8 with hydrochloric acid, adjust temperature to 60-70℃, react for 15-35min, take out and dry to obtain modified polyester.

4. The polyester low-elastic yarn according to claim 2, characterized in that: The graft cross-linking agent is glutaraldehyde.

5. The polyester low-elastic yarn according to claim 1, characterized in that: The modified chitosan comprises the following components in parts by weight: 10 parts of chitosan, 10-20 parts of sodium tripolyphosphate, 1.5-2.5 parts of tetramethylammonium hydroxide, and 14-18 parts of propylene oxide.

6. The polyester low-elastic yarn according to claim 1, characterized in that: The preparation method of the modified chitosan comprises the following steps: Hydroxypropylation: Mix chitosan, sodium hydroxide solution and isopropanol, add tetramethylammonium hydroxide and propylene oxide, stir for 1-1.5h, heat to 75-85°C, stir for 6-7h, neutralize with hydrochloric acid solution to pH 7-7.6, precipitate and filter to obtain hydroxypropylated chitosan; Ionic modification: hydroxypropylated chitosan is dissolved in acetic acid to obtain a hydroxypropylated chitosan solution, sodium tripolyphosphate is dissolved in water to obtain a sodium tripolyphosphate solution, the two solutions are mixed, and stirred at 2000-3000 rpm for 2-4 hours to obtain hydroxypropylated modified chitosan.

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