Super-soft anti-yellowing polyamide master batch and fiber

Abstract

The application discloses a kind of super-soft anti-yellowing polyamide master batch and fiber, belong to high polymer material technical field, to solve the technical problems that polyamide material's flexibility and yellowing resistance performance need to be further promoted in prior art, including N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride are mixed, heating reaction, reaction is finished, petroleum ether is precipitated, filtration, drying, and modified polytetrahydrofuran graft PA6 is obtained;Modified polytetrahydrofuran graft PA6, modified hydrotalcite and triethylamine are added to toluene, heating reaction, and modified PA6 is obtained;Modified PA6, PA6 master batch, antioxidant 168 and antioxidant 3114 are melt mixed, extruded, granulated, cooled, dried, and super-soft anti-yellowing polyamide master batch is obtained;The super-soft anti-yellowing polyamide master batch prepared by the application has good heat resistance, flexibility and anti-yellowing property.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to an ultra-soft, anti-yellowing polyamide masterbatch and fiber. Background Technology

[0002] Polyamide, commonly known as nylon, is a general term for thermoplastic resins whose main molecular chain contains repeating amide groups. Based on different molecular structures, polyamides can be classified into PA6, PA66, PA56, and PA610, among others. Polyamides can be melt-spun into fibers, which possess excellent wear resistance and good mechanical properties. PA6, also known as Nylon 6, is an engineering plastic widely used in industry and daily life, ranking first among the five major engineering plastics. The amide bonds (-CONH-) and methylene groups (-CH-) in the PA6 molecule are prone to oxidative degradation under light, ultraviolet radiation, and / or high temperatures, forming conjugated double bonds and causing yellowing. This is detrimental to the long-term use of the material. Furthermore, as an important semi-crystalline polymer, PA6 has low toughness, limiting its application in some fields.

[0003] Chinese patent CN114015228B discloses anti-light and heat yellowing polyamide masterbatch and fiber. This invention discloses the preparation methods of type A masterbatch and type B masterbatch, and uses type A masterbatch and type B masterbatch respectively in the sheath and core layer of fiber, which can improve the utilization efficiency of anti-light and heat yellowing additives such as ultraviolet shielding agents and antioxidants. However, the optimal anti-light yellowing index disclosed in this invention is 3, and the optimal anti-heat yellowing index is 4, and the yellowing resistance performance needs to be further improved. Chinese patent CN114989422B discloses a polyamide material for industrial yarn and its preparation method and fiber. The invention introduces aromatic ring structures, phosphorus-containing groups, and flexible segments into the polyamide molecular chain through copolymerization. It utilizes the rigid benzene ring structure and the phosphorus-containing flame-retardant structure to reduce hydrogen bonding between polyamide molecular chains, increasing the proportion of amorphous regions in the modified polyamide. The long-chain flexible segments of the polyamide enhance the flexibility and activity of the modified polyamide. The polyamide material for industrial yarn prepared by this invention exhibits good flexibility and mechanical properties. However, the lack of any antioxidants in this invention results in poor resistance to yellowing. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an ultra-soft, anti-yellowing polyamide masterbatch and fiber, solving the technical issue that the flexibility and yellowing resistance of polyamide materials need further improvement. This invention also provides a method for preparing ultra-soft, anti-yellowing polyamide fibers, which is simple to operate, and the resulting ultra-soft, anti-yellowing polyamide fibers exhibit good softness, yellowing resistance, and thermal stability.

[0005] To achieve the above objectives, the present invention provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, comprising the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine are mixed and heated to react. After the reaction is completed, the mixture is precipitated in cold water, filtered, washed and dried to obtain modified benzotriazole. Step (2) Add polytetrahydrofuran and modified benzotriazole to N,N-dimethylformamide, add 4-dimethylaminopyridine, heat to react, and after the reaction is completed, rotary evaporate to obtain modified polytetrahydrofuran; Step (3) N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride are mixed, heated and reacted. After the reaction is completed, petroleum ether is used to precipitate the mixture, which is then filtered and dried to obtain modified polytetrahydrofuran-grafted PA6. Step (4) Modified polytetrahydrofuran-grafted PA6, modified hydrotalcite and triethylamine are added to toluene, heated to react, and after the reaction is completed, the mixture is evaporated under reduced pressure and dried to obtain modified PA6. Step (5) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are melt-mixed, extruded, granulated, cooled and dried to obtain ultra-soft anti-yellowing polyamide masterbatch; The preparation method of modified hydrotalcite includes the following steps: Hydrotalcite was calcined at high temperature to obtain intermediate I; intermediate I was added to the mixed solution under a nitrogen atmosphere and heated to react. After the reaction was completed, the solution was filtered, washed with ethanol, and dispersed in distilled water to obtain an intercalated hydrotalcite slurry. Intercalated hydrotalcite slurry and 3-chloropropylmethyldimethoxysilane were mixed, ultrasonically dispersed, heated to react, filtered and dried after the reaction was completed to obtain modified hydrotalcite.

[0006] Preferably, in step (1), the preparation method of amino-terminated PA6 includes the following steps: Under nitrogen protection, caprolactam, hexamethylenediamine and deionized water were placed in a reaction vessel and reacted at 220-240℃ and 0.1-1MPa pressure for 2-4 hours. The pressure was then released to atmospheric pressure, extracted in a 100℃ water bath for 12 hours, and dried in a vacuum oven at 80℃ for 3 hours to obtain amino-terminated PA6. The molar ratio of caprolactam to hexamethylenediamine is (1-1.5):0.1. The mass of deionized water is 1-3% of the total mass of the reaction system.

[0007] Preferably, the weight-average molecular weight of amino-terminated PA6 is 8500-10000.

[0008] Preferably, the high-temperature calcination conditions are: calcination at 420-460℃ for 3-5 hours.

[0009] Preferably, the mass ratio of intermediate I, mixed solution and distilled water is (6-10):(30-50):(20-40); the reaction conditions are 70-75℃ for 6-8 hours.

[0010] Preferably, the conditions for ultrasonic dispersion are: ultrasonication at a frequency of 30-50 kHz for 10-14 minutes. Preferably, the mass ratio of the intercalated hydrotalcite slurry to 3-chloropropylmethyldimethoxysilane is (100-180):(10-18); the reaction conditions are 50-60℃ for 2-4 hours.

[0011] Preferably, in step (1), the mass ratio of tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine is (2000-4000):(100-180):(120-200):(20-40); the reaction temperature is 40-60℃, and the reaction time is 5-7h.

[0012] Preferably, in step (2), the mass ratio of polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine is (300-500):(80-90):(1800-2600):(3-5); the reaction temperature is 75-95℃ and the reaction time is 6-8h.

[0013] Preferably, in step (3), the mass ratio of N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and petroleum ether is (2200-4200):(80-100):(120-160):(50-90):(9000-12000); the reaction temperature is 55-65℃, and the reaction time is 9-13h.

[0014] Preferably, in step (4), the mass ratio of modified polytetrahydrofuran-grafted PA6, modified hydrotalcite, triethylamine and toluene is (200-400):(12-20):(4-6):(800-1000); the reaction temperature is 80-100℃ and the reaction time is 10-12h.

[0015] Preferably, in step (5), the mass ratio of modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 is (30-50):(50-70):(0.5-1):(1-2).

[0016] Preferably, in step (5), the mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is (30-50):(150-270):(12-20).

[0017] Preferably, an ultra-soft, anti-yellowing polyamide masterbatch is prepared using the aforementioned method.

[0018] Preferably, an ultra-soft, anti-yellowing polyamide fiber prepared using the aforementioned ultra-soft, anti-yellowing polyamide masterbatch is prepared by the following steps: The ultra-soft, anti-yellowing polyamide masterbatch is melt-extruded, cooled, oiled, stretched, and wound to obtain ultra-soft, anti-yellowing polyamide fiber.

[0019] Preferably, the side blowing temperature in the melt extrusion is 10-20℃ and the air velocity is 0.1-0.7m / s; the oiling process parameters are: the oil pump mass flow rate is 0.5-2kg / h.

[0020] Preferably, the process parameters for melt extrusion are as follows: the temperature of the twin-screw spinner in zones I, II, and III is 220-260℃, the metering pump temperature is 220-260℃, the pipeline temperature is 220-260℃, the housing temperature is 220-260℃, the metering pump speed is 8-20Hz, and the spinneret has 12-36 holes with a hole diameter of 0.2-0.5μm.

[0021] Preferably, the drawing step uses a guide roller hot roller. The temperature of the guide roller hot roller GR1 is 40-100℃, and the rotation speed is 200-600m / min; the temperature of GR2 is 80-160℃, the rotation speed is 500-900m / min, and the drawing ratio is 2-4 times.

[0022] In this invention, the acyl chloride group in trimellitic anhydride chloride reacts with the hydroxyl group in 2-(2,4-dihydroxyphenyl)-2H-benzotriazole to obtain modified benzotriazole; the hydroxyl group at the end of polytetrahydrofuran undergoes a ring-opening reaction with the anhydride group in modified benzotriazole to introduce a carboxyl group at the end of polytetrahydrofuran to obtain modified polytetrahydrofuran; the carboxyl group in modified polytetrahydrofuran reacts with one end amino group in amino-terminated PA6 under the catalysis of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to obtain modified polytetrahydrofuran-grafted PA6; the end amino group in modified polytetrahydrofuran-grafted PA6 reacts with the chlorine group in modified hydrotalcite to obtain modified PA6; the modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are melt-mixed, extruded, granulated, cooled and dried to obtain an ultra-soft anti-yellowing polyamide masterbatch.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In this invention, hydrotalcite is an inorganic nanosheet with high rigidity. Poor dispersion often reduces the material's flexibility and elongation at break. In this invention, bis(methoxybenzoic acid) with UV absorption function is intercalated into hydrotalcite, followed by modification with 3-chloropropylmethyldimethoxysilane to obtain a modified hydrotalcite with better dispersibility. Simultaneously, hydrotalcite possesses high thermal stability; its addition enhances the material's thermal stability and resistance to yellowing. The silicon-oxygen bonds in 3-chloropropylmethyldimethoxysilane have high bond energies, improving heat resistance. This preparation process expands the application of hydrotalcite in anti-yellowing materials.

[0024] 2. In this invention, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole is an ultraviolet absorber that absorbs ultraviolet light and converts it into harmless heat energy, thereby protecting the material from photodegradation and delaying yellowing. The acyl chloride group in trimellitic anhydride reacts with the hydroxyl group in 2-(2,4-dihydroxyphenyl)-2H-benzotriazole to obtain modified benzotriazole; the hydroxyl group at the end of polytetrahydrofuran undergoes a ring-opening reaction with the anhydride group in the modified benzotriazole, introducing a carboxyl group at the end of the polytetrahydrofuran to obtain modified polytetrahydrofuran; this modified polytetrahydrofuran not only has good flexibility but also UV resistance. Furthermore, amino-terminated PA6 has better thermal stability than PA6. The modified polytetrahydrofuran and amino-terminated PA6 are linked by chemical bonds, which enhances compatibility and improves the flexibility and yellowing resistance of amino-terminated PA6. Modified PA6 grafted with modified polytetrahydrofuran and then chemically bonded with modified hydrotalcite can produce modified PA6 with better thermal stability.

[0025] 3. The antioxidant 168 added in this invention is a phosphite-based auxiliary antioxidant, which mainly delays material aging by decomposing hydroperoxides generated during polymer oxidation. The decomposition of hydroperoxides also blocks the formation of yellowing precursors. Antioxidant 3114 is a highly efficient hindered phenolic primary antioxidant that can both capture alkyl free radicals (R・) to interrupt the oxidation chain reaction and block chromophore formation through free radical capture, thereby improving yellowing resistance. Modified hydrotalcite is chemically bonded to modified polytetrahydrofuran grafted with PA6, resulting in better compatibility and dispersibility. The interlayer dimethoxybenzoic acid is protected by the main body layer, extending its service life. Simultaneously, modified hydrotalcite has both UV absorption and shielding functions, improving yellowing resistance and addressing the problems of poor stability and short service life of traditional UV absorbers in polymers. The synergistic effect of these three agents significantly improves the yellowing resistance of the matrix material. Attached Figure Description

[0026] Figure 1 This is a flow chart of the preparation process of the ultra-soft, anti-yellowing polyamide masterbatch in this invention; Figure 2 This is a flowchart of the preparation process of the modified hydrotalcite in this invention. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1 This embodiment provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, including the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine were mixed in a mass ratio of 2000:100:120:20 and reacted at 40°C for 7 h. After the reaction was completed, the mixture was precipitated in cold water at 5°C for 3 h, filtered, washed with anhydrous ethanol, and dried at 60°C for 5 h to obtain modified benzotriazole. Step (2) Polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine were mixed in a mass ratio of 300:80:1800:3 and reacted at 75°C for 8 hours. After the reaction was completed, the mixture was rotary evaporated at 10 kPa, 60°C and 120 r / min for 1 hour to obtain modified polytetrahydrofuran. Step (3) N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were mixed and reacted at 55°C for 13 h. After the reaction was completed, petroleum ether was added for precipitation, filtered, and dried in an oven at 60°C for 10 h to obtain modified polytetrahydrofuran-grafted PA6. The mass ratio of N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and petroleum ether is 2200:80:120:50:9000. Step (4) Modified polytetrahydrofuran-grafted PA6, modified hydrotalcite, triethylamine and toluene are mixed in a mass ratio of 200:12:4:800 and reacted at 80℃ for 12h. After the reaction is completed, the mixture is distilled under reduced pressure at 0.03MPa and 70℃ for 50min and dried to obtain modified PA6. The preparation method of the modified hydrotalcite includes the following steps: Hydrotalcite was calcined at 420°C for 5 hours to obtain intermediate I. Intermediate I was mixed with a mixed solution under a nitrogen atmosphere and reacted at 70°C for 8 hours. After the reaction was completed, the mixture was filtered, washed with ethanol, and dispersed in distilled water to obtain an intercalated hydrotalcite slurry. The mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is 30:150:12. The mass ratio of intermediate I, mixed solution and distilled water is 6:30:20. Intercalated hydrotalcite slurry and 3-chloropropylmethyldimethoxysilane were mixed at a mass ratio of 100:10, ultrasonicated at 30 kHz for 14 min, reacted at 50 °C for 4 h, filtered, washed with deionized water, and dried at 60 °C for 6 h to obtain modified hydrotalcite. Step (5) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are placed in a twin-screw extruder at a mass ratio of 30:50:0.5:1, melt-mixed at 220°C, extruded, granulated, cooled, and vacuum dried at 60°C for 8 hours to obtain ultra-soft anti-yellowing polyamide masterbatch.

[0029] Example 2 This embodiment provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, including the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine were mixed in a mass ratio of 2500:120:140:25 and reacted at 45°C for 6.5 h. After the reaction was completed, the mixture was precipitated in cold water at 4°C for 2.5 h, filtered, washed with anhydrous ethanol, and dried at 65°C for 4.5 h to obtain modified benzotriazole. Step (2) Polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine were mixed in a mass ratio of 350:82:2000:3.5 and reacted at 80°C for 7.5 h. After the reaction was completed, the mixture was rotary evaporated at 10 kPa, 62°C and 160 r / min for 0.8 h to obtain modified polytetrahydrofuran. Step (3) N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were mixed and reacted at 57°C for 12 h. After the reaction was completed, petroleum ether was added for precipitation, filtered, and dried in an oven at 62°C for 9.5 h to obtain modified polytetrahydrofuran-grafted PA6. The mass ratio of N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and petroleum ether is 2700:85:130:60:9750. Step (4) Modified polytetrahydrofuran-grafted PA6, modified hydrotalcite, triethylamine and toluene are mixed in a mass ratio of 250:14:4.5:850 and reacted at 85℃ for 11.5h. After the reaction is completed, the mixture is distilled under reduced pressure at 0.03MPa and 72℃ for 45min and dried to obtain modified PA6. The preparation method of the modified hydrotalcite includes the following steps: Hydrotalcite was calcined at 430°C for 4.5 h to obtain intermediate I; intermediate I was mixed with a mixed solution under a nitrogen atmosphere and reacted at 71°C for 7.5 h. After the reaction was completed, the mixture was filtered, washed with ethanol, and dispersed in distilled water to obtain an intercalated hydrotalcite slurry. The mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is 35:180:14. The mass ratio of intermediate I, mixed solution and distilled water is 7:35:25. Intercalated hydrotalcite slurry and 3-chloropropylmethyldimethoxysilane were mixed at a mass ratio of 120:12, ultrasonicated at 35 kHz for 13 min, reacted at 52 ℃ for 3.5 h, filtered, washed with deionized water, and dried at 65 ℃ for 5.5 h to obtain modified hydrotalcite. Step (5) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are placed in a twin-screw extruder at a mass ratio of 35:55:0.6:1.2, melt-mixed at 225°C, extruded, granulated, cooled, and vacuum dried at 65°C for 7 hours to obtain ultra-soft anti-yellowing polyamide masterbatch.

[0030] Example 3 This embodiment provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, including the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine were mixed in a mass ratio of 3000:140:160:30 and reacted at 50°C for 6 hours. After the reaction was completed, the mixture was precipitated in cold water at 3°C ​​for 2 hours, filtered, washed with anhydrous ethanol, and dried at 70°C for 4 hours to obtain modified benzotriazole. Step (2) Polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine were mixed in a mass ratio of 400:85:2200:4 and reacted at 85°C for 7 h. After the reaction was completed, the mixture was rotary evaporated at 10 kPa, 65°C and 200 r / min for 0.7 h to obtain modified polytetrahydrofuran. Step (3) N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were mixed and reacted at 60°C for 11 h. After the reaction was completed, petroleum ether was added for precipitation, filtered, and dried in an oven at 65°C for 9 h to obtain modified polytetrahydrofuran-grafted PA6. The mass ratio of N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and petroleum ether is 3200:90:140:70:10500. Step (4) Modified polytetrahydrofuran-grafted PA6, modified hydrotalcite, triethylamine and toluene are mixed in a mass ratio of 300:16:5:900 and reacted at 90℃ for 11h. After the reaction is completed, the mixture is distilled under reduced pressure at 0.03MPa and 75℃ for 40min and dried to obtain modified PA6. The preparation method of the modified hydrotalcite includes the following steps: Hydrotalcite was calcined at 440°C for 4 hours to obtain intermediate I. Intermediate I was mixed with a mixed solution under a nitrogen atmosphere and reacted at 73°C for 7 hours. After the reaction was completed, the mixture was filtered, washed with ethanol, and dispersed in distilled water to obtain an intercalated hydrotalcite slurry. The mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is 40:210:16. The mass ratio of intermediate I, mixed solution and distilled water is 8:40:30. Intercalated hydrotalcite slurry and 3-chloropropylmethyldimethoxysilane were mixed at a mass ratio of 140:14, ultrasonicated at 40 kHz for 12 min, reacted at 55 ℃ for 3 h, filtered, washed with deionized water, and dried at 70 ℃ for 5 h to obtain modified hydrotalcite. Step (5) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are placed in a twin-screw extruder at a mass ratio of 40:60:0.8:1.5, melt-mixed at 230°C, extruded, granulated, cooled, and vacuum dried at 70°C for 6 hours to obtain ultra-soft anti-yellowing polyamide masterbatch.

[0031] Example 4 This embodiment provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, including the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine were mixed in a mass ratio of 3500:160:180:35 and reacted at 55°C for 5.5 h. After the reaction was completed, the mixture was precipitated in cold water at 1°C for 1.5 h, filtered, washed with anhydrous ethanol, and dried at 75°C for 3.5 h to obtain modified benzotriazole. Step (2) Polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine were mixed in a mass ratio of 450:87:2400:4.5 and reacted at 90°C for 6.5 h. After the reaction was completed, the mixture was rotary evaporated at 10 kPa, 67°C and 240 r / min for 0.6 h to obtain modified polytetrahydrofuran. Step (3) N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were mixed and reacted at 62°C for 10 h. After the reaction was completed, petroleum ether was added for precipitation, filtered, and dried in an oven at 67°C for 8.5 h to obtain modified polytetrahydrofuran-grafted PA6. The mass ratio of N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and petroleum ether is 3700:95:150:80:11250. Step (4) Modified polytetrahydrofuran-grafted PA6, modified hydrotalcite, triethylamine and toluene are mixed in a mass ratio of 350:18:5.5:950 and reacted at 95℃ for 10.5h. After the reaction is completed, the mixture is distilled under reduced pressure at 0.03MPa and 77℃ for 35min and dried to obtain modified PA6. The preparation method of the modified hydrotalcite includes the following steps: Hydrotalcite was calcined at 450°C for 3.5 h to obtain intermediate I; intermediate I was mixed with a mixed solution under a nitrogen atmosphere and reacted at 74°C for 6.5 h. After the reaction was completed, the mixture was filtered, washed with ethanol, and dispersed in distilled water to obtain an intercalated hydrotalcite slurry. The mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is 45:240:18. The mass ratio of intermediate I, mixed solution and distilled water is 9:45:35. Intercalated hydrotalcite slurry and 3-chloropropylmethyldimethoxysilane were mixed at a mass ratio of 160:16, ultrasonicated at 45 kHz for 11 min, reacted at 57 °C for 2.5 h, filtered, washed with deionized water, and dried at 75 °C for 4.5 h to obtain modified hydrotalcite. Step (5) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are placed in a twin-screw extruder at a mass ratio of 45:65:0.9:1.8, melt-mixed at 235°C, extruded, granulated, cooled, and vacuum dried at 75°C for 5 hours to obtain ultra-soft anti-yellowing polyamide masterbatch.

[0032] Example 5 This embodiment provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, including the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine were mixed in a mass ratio of 4000:180:200:40 and reacted at 60°C for 5 h. After the reaction was completed, the mixture was precipitated in cold water at 0°C for 1 h, filtered, washed with anhydrous ethanol, and dried at 80°C for 3 h to obtain modified benzotriazole. Step (2) Polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine were mixed in a mass ratio of 500:90:2600:5 and reacted at 95°C for 6 h. After the reaction was completed, the mixture was rotary evaporated at 10 kPa, 70°C and 280 r / min for 0.5 h to obtain modified polytetrahydrofuran. Step (3) N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were mixed and reacted at 65°C for 9 h. After the reaction was completed, petroleum ether was added for precipitation, filtered, and dried in an oven at 70°C for 8 h to obtain modified polytetrahydrofuran-grafted PA6. The mass ratio of N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and petroleum ether is 4200:100:160:90:12000. Step (4) Modified polytetrahydrofuran-grafted PA6, modified hydrotalcite, triethylamine and toluene are mixed in a mass ratio of 400:20:6:1000 and reacted at 100℃ for 10h. After the reaction is completed, the mixture is distilled under reduced pressure at 0.03MPa and 80℃ for 30min and dried to obtain modified PA6. The preparation method of the modified hydrotalcite includes the following steps: Hydrotalcite was calcined at 460°C for 3 hours to obtain intermediate I; intermediate I was mixed with the mixed solution under a nitrogen atmosphere and reacted at 75°C for 6 hours. After the reaction was completed, the mixture was filtered, washed with ethanol, and dispersed in distilled water to obtain an intercalated hydrotalcite slurry. The mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is 50:270:20. The mass ratio of intermediate I, mixed solution and distilled water is 10:50:40. Intercalated hydrotalcite slurry and 3-chloropropylmethyldimethoxysilane were mixed at a mass ratio of 180:18, ultrasonicated at 50 kHz for 10 min, reacted at 60 ℃ for 2 h, filtered, washed with deionized water, and dried at 80 ℃ for 4 h to obtain modified hydrotalcite. Step (5) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are placed in a twin-screw extruder at a mass ratio of 50:70:1:2, melt-mixed at 240°C, extruded, granulated, cooled, and vacuum dried at 80°C for 4 hours to obtain ultra-soft anti-yellowing polyamide masterbatch.

[0033] Example 6 This embodiment provides a method for preparing amino-terminated PA6, including the following steps: Under nitrogen protection, caprolactam, hexamethylenediamine and deionized water were placed in a reaction vessel and reacted at 220°C and 0.1 MPa for 4 h. The pressure was then released to atmospheric pressure, extracted in a 100°C water bath for 12 h, and dried in a vacuum oven at 80°C for 3 h to obtain amino-terminated PA6. The molar ratio of caprolactam to hexamethylenediamine is 1:0.1. The mass of deionized water is 1% of the total mass of the reaction system. Among them, the weight-average molecular weight of amino-terminated PA6 is 8500.

[0034] Comparative Example 1 This comparative example provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, comprising the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine were mixed in a mass ratio of 2000:100:120:20 and reacted at 40°C for 7 h. After the reaction was completed, the mixture was precipitated in cold water at 5°C for 3 h, filtered, washed with anhydrous ethanol, and dried at 60°C for 5 h to obtain modified benzotriazole. Step (2) Polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine were mixed in a mass ratio of 300:80:1800:3 and reacted at 75°C for 8 hours. After the reaction was completed, the mixture was rotary evaporated at 10 kPa, 60°C and 120 r / min for 1 hour to obtain modified polytetrahydrofuran. Step (3) N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride were mixed and reacted at 55°C for 13 h. After the reaction was completed, petroleum ether was added for precipitation, filtered, and dried in an oven at 60°C for 10 h to obtain modified polytetrahydrofuran-grafted PA6. The mass ratio of N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and petroleum ether is 2200:80:120:50:9000. Step (4) Modified polytetrahydrofuran grafted PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are placed in a twin-screw extruder at a mass ratio of 30:50:0.5:1, melt-mixed at 220°C, extruded, granulated, cooled, and vacuum dried at 60°C for 8 hours to obtain ultra-soft anti-yellowing polyamide masterbatch.

[0035] Comparative Example 2 This comparative example provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, comprising the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine were mixed in a mass ratio of 2000:100:120:20 and reacted at 40°C for 7 h. After the reaction was completed, the mixture was precipitated in cold water at 5°C for 3 h, filtered, washed with anhydrous ethanol, and dried at 60°C for 5 h to obtain modified benzotriazole. Step (2) Polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine were mixed in a mass ratio of 300:80:1800:3 and reacted at 75°C for 8 hours. After the reaction was completed, the mixture was rotary evaporated at 10 kPa, 60°C and 120 r / min for 1 hour to obtain modified polytetrahydrofuran. Step (3) Modified polytetrahydrofuran and amino-terminated PA6 are melt-mixed at a mass ratio of 80:120 and dried in an oven at 60°C for 10 hours to obtain modified PA6; Step (4) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are placed in a twin-screw extruder at a mass ratio of 30:50:0.5:1, melt-mixed at 220°C, extruded, granulated, cooled, and vacuum dried at 60°C for 8 hours to obtain ultra-soft anti-yellowing polyamide masterbatch.

[0036] Comparative Example 3 This comparative example provides a method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, comprising the following steps: Step (1) Polytetrahydrofuran and amino-terminated PA6 are melt-mixed at a mass ratio of 80:120 and dried in an oven at 60°C for 10 hours to obtain modified PA6; Step (2) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are placed in a twin-screw extruder at a mass ratio of 30:50:0.5:1, melt-mixed at 220℃, extruded, granulated, cooled, and vacuum dried at 60℃ for 8h to obtain ultra-soft anti-yellowing polyamide masterbatch.

[0037] The amino-terminated PA6 in Examples 1-5 and Comparative Examples 1-3 of this invention were all prepared using the amino-terminated PA6 obtained in Example 6.

[0038] In the embodiments and comparative examples of this invention, the hydrotalcite is specifically MgAl hydrotalcite, sourced from Jingjiang Kanggaote New Material Technology Co., Ltd., brand: Kanggaote; caprolactam is from Shandong Fuman New Material Co., Ltd., CAS number: 105-60-2; trimellitic anhydride chloride is from Shanghai Aoji Chemical Co., Ltd., CAS number: 1204-28-0; 2-(2,4-dihydroxyphenyl)-2H-benzotriazole is from Zhengzhou Huiju Chemical Co., Ltd., CAS number: 22607-31-4; polytetrahydrofuran is from Jining Lido Chemical Co., Ltd., model: ptmg2000, with a molecular weight of 2000±50; PA6 masterbatch is from Suzhou Liaobo Plastics Co., Ltd., item number: 20230220; dimethoxybenzoic acid is from China National Pharmaceutical Group Shanghai Chemical Reagent Co., Ltd.; all others are commercially available products.

[0039] Performance testing: The ultra-soft, anti-yellowing polyamide masterbatches prepared in Examples 1-5 and Comparative Examples 1-3 were fed into the feed inlet of a spinning machine, passed through the screw into the spinning chamber, and the melt was ejected from the spinneret and entered the spinning tunnel. After cooling, oiling, drawing by the guide rollers, and winding, ultra-soft, anti-yellowing polyamide fibers were obtained. The main process parameters were: the spinneret had 36 holes with a diameter of 0.2 μm; the temperatures in zones I, II, and III of the twin-screw spinning machine were 250°C, 2... 50℃, 250℃, metering pump temperature is 250℃, pipeline temperature is 255℃, box temperature is 255℃, metering pump speed is 12Hz; side blowing air temperature is 15℃, wind speed is 0.1m / s; oil pump mass flow rate is 0.5kg / h; guide roller GR1 temperature is 40℃, speed is 100m / min, GR2 temperature is 100℃, speed is 500m / min, draw ratio is 2.5 times.

[0040] (1) Breaking elongation test: The ultra-soft anti-yellowing polyamide fibers obtained by melt spinning of the ultra-soft anti-yellowing polyamide masterbatch in Examples 1-5 and Comparative Examples 1-3 were tested. The test method refers to GB / T14344—2008 "Test method for tensile properties of chemical fiber filaments". The tensile spacing is 500 mm and the tensile speed is 500 mm / min. The specific test results are shown in Table 1. Table 1 As can be seen from the test results in Table 1, the ultra-soft, anti-yellowing polyamide masterbatch prepared in this invention has good elongation at break and a certain degree of flexibility. In this invention, modified polytetrahydrofuran is grafted with amino-terminated PA6 to form a block copolymer, introducing flexible segments into the rigid segments of PA6, thereby increasing flexibility. Modified hydrotalcite is chemically bonded to modified polytetrahydrofuran grafted with PA6, reducing interfacial tension and stress concentration factor, thus indirectly improving toughness. Compared with Example 1, Comparative Example 1 lacks modified hydrotalcite, therefore its flexibility decreases and its elongation at break value decreases. Compared to Comparative Example 1, Comparative Example 2 uses a physical mixing method to prepare modified PA6 by mixing modified polytetrahydrofuran and amino-terminated PA6. In this case, compared with the modified polytetrahydrofuran-grafted PA6 in Comparative Example 1, the modified polytetrahydrofuran-grafted PA6 in Comparative Example 1 has better compatibility and better mechanical properties. Therefore, the elongation at break of Comparative Example 2 is lower than that of Comparative Example 1.

[0041] (2) Anti-yellowing test: The test was conducted according to GB / T 30669-2014 Textiles - Tests for Color Fastness - Resistance to Yellowing, as follows: Fabrics made of ultra-soft anti-yellowing polyamide fibers corresponding to Examples 1-5 and Comparative Examples 1-3 were designated as Samples 1-8, and irradiated for 6 hours under a UV-A340 lamp or a UV-A340 combination lamp with a lamp wavelength of 320-340nm. According to ASTM E313 standard, a Konica Minolta CM3600d spectrophotometer with a D65 light source and a 10° viewing angle was used to test the yellowness index of the materials. The specific test results are shown in Table 2. (3) Heat resistance yellowing test: Fabrics made of ultra-soft anti-yellowing polyamide fibers corresponding to Examples 1-5 and Comparative Examples 1-3 were designated as Samples 1-8 and placed at 190°C for 2 minutes. According to ASTM E 313 standard, the yellowness index of the materials was tested using a Konica Minolta CM3600d spectrophotometer with a D65 light source and a 10° viewing angle. The specific test results are shown in Table 2. Table 2 As can be seen from the test results in Table 2, the fabrics made of the ultra-soft, anti-yellowing polyamide fibers corresponding to Examples 1-5 exhibit excellent anti-yellowing properties. The lower the photochromic index after light exposure, the less the material deviates from its original color, indicating better anti-yellowing performance. The heat yellowing index is an important indicator for measuring a material's ability to resist yellowing under high-temperature conditions; the lower the heat yellowing index, the less the material's color deviates from its original color, and the better its anti-yellowing performance. In the preparation of modified hydrotalcite of this invention, bis(methoxybenzoic acid) is first intercalated into the hydrotalcite layers, followed by surface modification with 3-chloropropylmethyldimethoxysilane to obtain modified hydrotalcite with better dispersibility and matrix compatibility. The bis(methoxybenzoic acid) contains a conjugated system that can absorb short-wavelength ultraviolet light, while the silicon-oxygen bonds in 3-chloropropylmethyldimethoxysilane have high chemical bond energy, improving heat resistance and enhancing resistance to yellowing. The hydrotalcite layer itself has high thermal stability, increasing the heat resistance of the matrix material. Comparative Example 1 lacks the modified hydrotalcite compared to Example 1; therefore, the yellowing resistance of the ultra-soft, anti-yellowing polyamide masterbatch obtained in Comparative Example 1 is reduced, meaning that the anti-photoyellowing index and anti-heatyellowing index of Sample 6 are both greater than those of Sample 1. Compared to Comparative Example 1, in Comparative Example 2, the modified polytetrahydrofuran and amino-terminated PA6 were not chemically linked, resulting in reduced compatibility of the modified polytetrahydrofuran containing the benzotriazole structure. This is detrimental to the continued photostability of the benzotriazole structure, leading to decreased resistance to photo-yellowing. Furthermore, the chemical bonding method in Comparative Example 1 enhances molecular chain stability, inhibits thermo-oxidative diffusion, and optimizes antioxidant distribution, thus promoting heat resistance to yellowing. However, the physical mixing method used in Comparative Example 2 resulted in decreased heat resistance to yellowing. In Comparative Example 3, the lack of modified benzotriazole compared to Comparative Example 2 resulted in decreased resistance to photo-yellowing. Simultaneously, the absence of modified benzotriazole to absorb ultraviolet light prevents photoinitiation, increasing antioxidant consumption and causing premature loss of protective effect during thermal aging, further reducing heat resistance to yellowing.

[0042] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for preparing an ultra-soft, anti-yellowing polyamide masterbatch, characterized in that, Includes the following steps: Step (1) Tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine are mixed and heated to react. After the reaction is completed, the mixture is precipitated in cold water, filtered, washed and dried to obtain modified benzotriazole. Step (2) Add polytetrahydrofuran and modified benzotriazole to N,N-dimethylformamide, add 4-dimethylaminopyridine, heat to react, and after the reaction is completed, rotary evaporate to obtain modified polytetrahydrofuran; Step (3) N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6 and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride are mixed, heated and reacted. After the reaction is completed, petroleum ether is used to precipitate the mixture, which is then filtered and dried to obtain modified polytetrahydrofuran-grafted PA6. Step (4) Modified polytetrahydrofuran-grafted PA6, modified hydrotalcite and triethylamine are added to toluene, heated to react, and after the reaction is completed, the mixture is evaporated under reduced pressure and dried to obtain modified PA6. Step (5) Modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 are melt-mixed, extruded, granulated, cooled and dried to obtain ultra-soft anti-yellowing polyamide masterbatch; The preparation method of modified hydrotalcite includes the following steps: Hydrotalcite was calcined at high temperature to obtain intermediate I; intermediate I was added to the mixed solution under a nitrogen atmosphere and heated to react. After the reaction was completed, the solution was filtered, washed with ethanol, and dispersed in distilled water to obtain an intercalated hydrotalcite slurry. Intercalated hydrotalcite slurry and 3-chloropropylmethyldimethoxysilane were mixed, ultrasonically dispersed, heated to react, filtered, and dried to obtain modified hydrotalcite.

2. The method for preparing an ultra-soft, anti-yellowing polyamide masterbatch according to claim 1, characterized in that, In step (3), the preparation method of amino-terminated PA6 includes the following steps: Under nitrogen protection, caprolactam, hexamethylenediamine and deionized water were placed in a reaction vessel and reacted at 220-240℃ and 0.1-1MPa pressure for 2-4 hours. The pressure was then released to atmospheric pressure, extracted in a 100℃ water bath for 12 hours, and dried in a vacuum oven at 80℃ for 3 hours to obtain amino-terminated PA6. The molar ratio of caprolactam to hexamethylenediamine is (1-1.5):0.

1. The mass of deionized water is 1-3% of the total mass of the reaction system.

3. The method for preparing an ultra-soft, anti-yellowing polyamide masterbatch according to claim 1, characterized in that, In step (1), the mass ratio of tetrahydrofuran, trimellitic anhydride chloride, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole and triethylamine is (2000-4000):(100-180):(120-200):(20-40); the reaction temperature is 40-60℃ and the reaction time is 5-7h.

4. The method for preparing an ultra-soft, anti-yellowing polyamide masterbatch according to claim 1, characterized in that, In step (2), the mass ratio of polytetrahydrofuran, modified benzotriazole, N,N-dimethylformamide and 4-dimethylaminopyridine is (300-500):(80-90):(1800-2600):(3-5); the reaction temperature is 75-95℃ and the reaction time is 6-8h.

5. The method for preparing an ultra-soft, anti-yellowing polyamide masterbatch according to claim 1, characterized in that, In step (3), the mass ratio of N,N-dimethylformamide, modified polytetrahydrofuran, amino-terminated PA6, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and petroleum ether is (2200-4200):(80-100):(120-160):(50-90):(9000-12000); the reaction temperature is 55-65℃, and the reaction time is 9-13h.

6. The method for preparing an ultra-soft, anti-yellowing polyamide masterbatch according to claim 1, characterized in that, In step (4), the mass ratio of modified polytetrahydrofuran-grafted PA6, modified hydrotalcite, triethylamine and toluene is (200-400):(12-20):(4-6):(800-1000); the reaction temperature is 80-100℃ and the reaction time is 10-12h.

7. The method for preparing an ultra-soft, anti-yellowing polyamide masterbatch according to claim 1, characterized in that, In step (5), the mass ratio of modified PA6, PA6 masterbatch, antioxidant 168 and antioxidant 3114 is (30-50):(50-70):(0.5-1):(1-2).

8. The method for preparing an ultra-soft, anti-yellowing polyamide masterbatch according to claim 1, characterized in that, In step (5), the mass ratio of dimethoxybenzoic acid, anhydrous ethanol and deionized water in the mixed solution is (30-50):(150-270):(12-20).

9. An ultra-soft, anti-yellowing polyamide masterbatch prepared by the preparation method of the ultra-soft, anti-yellowing polyamide masterbatch as described in any one of claims 1-8.

10. An ultra-soft, anti-yellowing polyamide fiber prepared using the ultra-soft, anti-yellowing polyamide masterbatch as described in claim 9, characterized in that, It is prepared by the following steps: The ultra-soft, anti-yellowing polyamide masterbatch is melt-extruded, cooled, oiled, stretched, and wound to obtain ultra-soft, anti-yellowing polyamide fiber.

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