Anti-yellowing TPU color master batch and preparation method thereof

Abstract

The application relates to the technical field of TPU color master batch, and particularly discloses an anti-yellowing TPU color master batch and a preparation method thereof. The application adopts polycarbonate diol as a soft segment structure of a TPU polymer chain, adopts dicyclohexyl methane diisocyanate as a hard segment structure, simultaneously introduces a reactive ultraviolet absorber and a dihydric alcohol chain extender as an ultraviolet absorption unit and a free radical scavenging unit, and adopts hydroxyethyl piperidine alcohol modified nano cerium dioxide as an inorganic filler, so that the ultraviolet resistance of the TPU material is enhanced.

Description

Technical Field

[0001] This invention relates to the field of TPU masterbatch technology, specifically to an anti-yellowing TPU masterbatch and its preparation method. Background Technology

[0002] Thermoplastic polyurethane elastomer (TPU) is a linear block copolymer formed by the addition polymerization of long-chain polyols and isocyanates. It possesses excellent elasticity, high abrasion resistance, outstanding tear strength, oil resistance, low-temperature resistance, and processability. TPU is widely used in automotive parts, wires and cables, medical devices, sporting goods, films, and pipes.

[0003] Traditional TPU materials, especially those based on aromatic isocyanates, are prone to yellowing under ultraviolet light because the benzene rings and adjacent carbamate bonds in the aromatic isocyanate molecular structure undergo photo-oxidation reactions, generating colored chromophores such as quinone structures. Furthermore, TPU materials also undergo similar oxidative degradation during thermo-oxidative aging, resulting in a yellowing color. Yellowing is not merely an aesthetic issue; it is accompanied by oxidative breakage of the internal molecular chains, leading to decreased mechanical properties, surface powdering, and embrittlement, thus severely impacting the service life and reliability of the TPU material.

[0004] Therefore, developing a TPU masterbatch that resists yellowing and applying it to the production of TPU materials is of great significance for broadening the application of TPU materials in outdoor, light-colored, and high weather-resistant fields. Summary of the Invention

[0005] The purpose of this invention is to provide an anti-yellowing TPU masterbatch and its preparation method, thereby solving the problems of decreased mechanical properties, surface powdering, and embrittlement of TPU materials due to yellowing during long-term use.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A method for preparing anti-yellowing TPU masterbatch, specifically as follows: Step 1: Mix hydroxyethylpiperidine alcohol with hexamethylene diisocyanate and react to obtain NCO-terminated ethylpiperidine alcohol; Step 2: Modify nano-cerium dioxide with silane coupling agent KH-550 to obtain aminated nano-cerium dioxide, and then react it with NCO-terminated ethylpiperidine alcohol to obtain ethylpiperidine alcohol-modified cerium dioxide; Step 3: Mix 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, trimethylolpropane and dicyclohexyldiimide and react to obtain a diol chain extender; Step 4: Mix and react polycarbonate diol, dicyclohexylmethane diisocyanate (hydrogenated MDI), reactive UV absorber and diol chain extender to obtain anti-yellowing polyurethane; Step 5: Melt-mix the anti-yellowing polyurethane with ethylpiperidine alcohol-modified cerium dioxide, extrude and granulate to obtain anti-yellowing TPU masterbatch.

[0007] As a limitation of this invention, the method for preparing the NCO-terminated ethylpiperidine alcohol is as follows: Under nitrogen protection, hydroxyethylpiperidine alcohol was added to tetrahydrofuran and stirred until homogeneous. Hexamethylene diisocyanate and dibutyltin dilaurate catalyst were then added. The mixture was stirred at 70-80℃ and 300-400 rpm for 2-4 hours. After the reaction was completed, the mixture was distilled under reduced pressure to obtain NCO-terminated ethylpiperidine alcohol.

[0008] As a limitation of the present invention, the mass ratio of hydroxyethylpiperidine alcohol, hexamethylene diisocyanate and catalyst dibutyltin dilaurate is (10-12):(10-14):(0.02-0.04).

[0009] Under the action of the catalyst dibutyltin dilaurate, the hydroxyl group on hydroxyethylpiperidine alcohol reacts with the isocyanate group of hexamethylene diisocyanate to form chemically bonded terminal NCO ethylpiperidine alcohol, in which the active hydroxyl group of hydroxyethylpiperidine alcohol is replaced by an isocyanate group.

[0010] As a limitation of this invention, the preparation method of the ethylpiperidine alcohol modified cerium dioxide is as follows: Nano-cerium dioxide was added to a mixture of ethanol and deionized water, stirred evenly, and ultrasonically dispersed for 10-20 min. Silane coupling agent KH-550 was added, and the pH was adjusted to 4-5. The mixture was stirred at 60-70℃ and 300-400 rpm for 8-10 h. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol and deionized water, and vacuum dried at 60-70℃ for 10-12 h to obtain aminated nano-cerium dioxide. Aminated nano-cerium dioxide was added to dimethyl sulfoxide, stirred until homogeneous, and ultrasonically dispersed for 10-20 min. Then, terminal NCO ethylpiperidinol and catalyst dibutyltin dilaurate were added, and the mixture was stirred at 90-100℃ and 300-400 rpm for 10-12 h. After the reaction was completed, the mixture was centrifuged, washed with ethanol and deionized water, and vacuum dried at 60-70℃ for 10-12 h to obtain ethylpiperidinol modified cerium dioxide.

[0011] As a limitation of the present invention, the mass ratio of the nano-cerium dioxide to the silane coupling agent KH-550 is (5-10):(0.2-0.3); the mass ratio of the aminated nano-cerium dioxide, the NCO-terminated ethylpiperidinol, and the catalyst dibutyltin dilaurate is (5-10):(0.25-0.35):(0.005-0.01).

[0012] The silanol groups hydrolyzed by the silane coupling agent KH-550 dehydrate and condense with the hydroxyl groups on the surface of nano-cerium dioxide to form covalent bonds. Organosilicon segments with amino groups at the ends are grafted onto the surface of the nano-cerium dioxide. Subsequently, the amino groups react with terminal NCO ethylpiperidinol or conventional isocyanate groups to form chemical bonds, thus immobilizing hydroxyethylpiperidinol on the surface of the nano-cerium dioxide. Nano-cerium dioxide can absorb ultraviolet light through valence band electron transitions. Hydroxyethylpiperidinol contains a hindered amine structure, which can quench the photogenerated carriers generated during the valence band electron transitions of nano-cerium dioxide and restore the hindered amine structure through intramolecular rearrangement to achieve cycling. Immobilizing hydroxyethylpiperidinol on the surface of nano-cerium dioxide allows the nano-cerium dioxide to perform its ultraviolet absorption function while preventing the generation of photogenerated carriers and active free radicals from catalyzing polymer chain degradation. This ensures long-term stable absorption and dissipation of incident ultraviolet light, preventing photocatalytic degradation of the TPU matrix. In addition, the nano-cerium dioxide particles are modified with silane coupling agent KH-550, which improves the interfacial compatibility between nano-cerium dioxide and TPU through polar interaction, enhances its dispersibility in the TPU matrix, reduces agglomeration, enhances the uniformity of nano-cerium dioxide UV protection, and enhances the flowability during TPU masterbatch processing.

[0013] As a limitation of this invention, the preparation method of the diol chain extender is as follows: 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and trimethylolpropane were added to dichloromethane and stirred until homogeneous. Dicyclohexyldiimide and the catalyst 4-dimethylaminopyridine were then added. The mixture was stirred at 20-30°C and 300-400 rpm for 10-12 hours. After the reaction was completed, the mixture was filtered. The filtrate was washed successively with aqueous sodium hydroxide solution, saturated sodium bicarbonate solution, and saturated sodium chloride solution. The solution was dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the diol chain extender.

[0014] As a limitation of the present invention, the mass ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, trimethylolpropane, dicyclohexyldiimide and catalyst 4-dimethylaminopyridine is (10-14):(4-6):(6-10):(0.4-0.5).

[0015] In the presence of dicyclohexyldiimide and the catalyst 4-dimethylaminopyridine, the carboxyl group of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid undergoes dehydration condensation with a hydroxyl group of trimethylolpropane to generate a chemically bonded AO-f diol structure, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid. It is directly bonded to the chain extender. During TPU polymerization, the hydroxyl groups on the chain extender react with the isocyanate groups to form urethane bonds. 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid is then fixed onto the polyurethane molecular chain, enhancing the antioxidant stability of the TPU matrix. Simultaneously, it fundamentally avoids the migration and volatilization of small-molecule antioxidants within the TPU matrix, achieving long-lasting antioxidant protection.

[0016] As a limitation of the present invention, the preparation method of the anti-yellowing polyurethane is as follows: Under nitrogen protection, polycarbonate diol and reactive UV absorber are mixed and stirred evenly. The mixture is heated to 90-100℃, and dicyclohexylmethane diisocyanate and dibutyltin dilaurate catalyst are added. The mixture is stirred at 90-100℃ and 300-400 rpm for 2-3 hours. After the reaction is completed, diol chain extender is added, and the mixture is stirred for another 1-2 hours. After the reaction is completed, the mixture is cooled to obtain anti-yellowing polyurethane.

[0017] Preferably, the mass ratio of the polycarbonate diol, the reactive ultraviolet absorber, the dicyclohexylmethane diisocyanate, and the catalyst dibutyltin dilaurate is (100-120):(10-14):(33-43):(0.03-0.05).

[0018] Under the catalysis of dibutyltin dilaurate, the terminal hydroxyl groups of polycarbonate diol and reactive UV absorbers react with the isocyanate groups of dicyclohexylmethane diisocyanate. The benzotriazole structure from the reactive UV absorber is chemically bonded to the polymer backbone, forming a TPU prepolymer with a -NCO terminal benzotriazole structure. Subsequently, under the action of a diol chain extender, the prepolymer completes chain growth, while the hindered phenolic antioxidant structure on the chain extender is chemically bonded to the TPU polymer chain. Polycarbonate diol serves as the soft segment structure of the TPU polymer chain, and dicyclohexylmethane diisocyanate serves as the hard segment structure, enhancing the intrinsic strength, toughness, and other mechanical properties of the TPU matrix. The introduced reactive UV absorber and diol chain extender act as UV absorption units and free radical scavenging units, respectively, enhancing the UV resistance of the TPU material.

[0019] As a limitation of the present invention, the mass ratio of anti-yellowing polyurethane to ethylpiperidine alcohol modified cerium dioxide in the anti-yellowing TPU masterbatch is (65-75):(25-35); the extrusion granulation process conditions include a screw speed of 200-300 rpm, a zone 1 temperature of 180-190℃, a zone 2 temperature of 190-200℃, a zone 3 temperature of 200-210℃, and a zone 4 temperature of 180-190℃.

[0020] The application of anti-yellowing TPU masterbatch prepared by any of the above preparation methods in anti-yellowing TPU products.

[0021] Compared with the prior art, the beneficial effects of the present invention are: This invention uses polycarbonate diol as the soft segment structure of the TPU polymer chain and dicyclohexylmethane diisocyanate as the hard segment structure. It also introduces reactive UV absorbers and diol chain extenders as UV absorption units and free radical scavenging units to enhance the UV resistance of TPU materials.

[0022] This invention uses hydroxyethylpiperidinol-modified nano-cerium dioxide as an inorganic filler. While the nano-cerium dioxide performs its ultraviolet absorption function, it avoids the generation of photogenerated carriers and active free radicals that catalyze the degradation of polymer molecular chains, enabling it to absorb and dissipate incident ultraviolet light stably for a long time and enhancing the UV resistance of TPU materials. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. The terminology used in the embodiments is for describing specific implementation schemes, not for limiting the scope of protection of the present invention. The dosages in the embodiments are laboratory-scale tests and can be scaled up proportionally. 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.

[0024] In the examples and comparative examples, the full name of hydroxyethylpiperidinol is 1-(2'-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol, CAS number 52722-86-8; the particle size of nano-cerium dioxide is 50 nm; the molecular weight of polycarbonate diol is 1000; the name of the reactive ultraviolet absorber is ultraviolet absorber Chiguard R-455, and the composition is 2-[3'-(2H-benzotriazole)-5'-tert-butyl-4'-hydroxy-phenyl]-2-ethylpropane-1,3-propanediol); all raw materials used in the examples were dehydrated and dried before being added.

[0025] Example 1: A method for preparing an anti-yellowing TPU masterbatch, specifically as follows: Step 1: Under nitrogen protection, 10g of hydroxyethylpiperidinol was added to 100mL of tetrahydrofuran and stirred until homogeneous. Then, 10g of hexamethylene diisocyanate and 0.03g of catalyst dibutyltin dilaurate were added. The mixture was stirred at 80℃ and 400rpm for 3h. After the reaction was completed, the mixture was distilled under reduced pressure to obtain NCO-terminated ethylpiperidinol. Step 2: Add 5g of nano-cerium dioxide to a mixture of 90mL ethanol and 10mL deionized water, stir evenly, sonicate for 10min, add 0.2g of silane coupling agent KH-550, adjust the pH to 5, stir at 70℃ and 400rpm for 8h, cool after the reaction is complete, filter, wash with ethanol and deionized water, and vacuum dry at 60℃ for 12h to obtain aminated nano-cerium dioxide; Step 3: Add 5g of aminated nano-cerium dioxide to 100mL of dimethyl sulfoxide, stir evenly, and ultrasonically disperse for 10min. Add 0.25g of NCO-terminated ethylpiperidinol and 0.005g of catalyst dibutyltin dilaurate. Stir and react at 90℃ and 400rpm for 12h. After the reaction is completed, centrifuge and wash with ethanol and deionized water. Dry under vacuum at 60℃ for 12h to obtain ethylpiperidinol modified cerium dioxide. Step 4: Add 10g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and 4g of trimethylolpropane to 200mL of dichloromethane, stir well, add 6g of dicyclohexyldiimide and 0.4g of catalyst 4-dimethylaminopyridine, stir at 30℃ and 400rpm for 12h, filter after the reaction is complete, wash the filtrate successively with 1wt% sodium hydroxide aqueous solution, saturated sodium bicarbonate aqueous solution and saturated sodium chloride aqueous solution, dry with anhydrous sodium sulfate, remove the solvent by rotary evaporation to obtain the diol chain extender; Step 5: Under nitrogen protection, mix 100g of polycarbonate diol and 10g of UV absorber Chiguard R-455, stir evenly, heat to 95℃, add 33g of hydrogenated MDI and 0.03g of catalyst dibutyltin dilaurate, stir at 95℃ and 400rpm for 2h. After the reaction is complete, add 4g of diol chain extender, continue stirring for 1h, cool after the reaction is complete to obtain anti-yellowing polyurethane; Step 6: Under nitrogen protection, mix 75g of anti-yellowing polyurethane and 25g of ethylpiperidinol modified cerium dioxide evenly, add it to a twin-screw extruder for extrusion, set the screw speed to 300rpm, the zone 1 temperature to 180℃, the zone 2 temperature to 190℃, the zone 3 temperature to 200℃, and the zone 4 temperature to 190℃. After extrusion, cool and granulate to obtain anti-yellowing TPU masterbatch.

[0026] Example 2: A method for preparing an anti-yellowing TPU masterbatch, specifically as follows: Step 1: Under nitrogen protection, 11g of hydroxyethylpiperidinol was added to 100mL of tetrahydrofuran and stirred until homogeneous. Then, 12g of hexamethylene diisocyanate and 0.03g of catalyst dibutyltin dilaurate were added. The mixture was stirred at 80℃ and 400rpm for 3h. After the reaction was completed, the mixture was distilled under reduced pressure to obtain NCO-terminated ethylpiperidinol. Step 2: Add 7g of nano-cerium dioxide to a mixture of 90mL ethanol and 10mL deionized water, stir evenly, sonicate for 10min, add 0.25g of silane coupling agent KH-550, adjust the pH to 5, stir at 70℃ and 400rpm for 8h, cool after the reaction is complete, filter, wash with ethanol and deionized water, and vacuum dry at 60℃ for 12h to obtain aminated nano-cerium dioxide; Step 3: Add 7g of aminated nano-cerium dioxide to 100mL of dimethyl sulfoxide, stir evenly, and ultrasonically disperse for 10min. Add 0.3g of NCO-terminated ethylpiperidinol and 0.007g of catalyst dibutyltin dilaurate. Stir and react at 90℃ and 400rpm for 12h. After the reaction is completed, centrifuge and wash with ethanol and deionized water. Dry under vacuum at 60℃ for 12h to obtain ethylpiperidinol modified cerium dioxide. Step 4: Add 12g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and 5g of trimethylolpropane to 200mL of dichloromethane, stir well, add 8g of dicyclohexyldiimide and 0.5g of catalyst 4-dimethylaminopyridine, stir at 30℃ and 400rpm for 12h, filter after the reaction is complete, wash the filtrate successively with 1wt% sodium hydroxide aqueous solution, saturated sodium bicarbonate aqueous solution and saturated sodium chloride aqueous solution, dry with anhydrous sodium sulfate, remove the solvent by rotary evaporation to obtain the diol chain extender; Step 5: Under nitrogen protection, mix 110g of polycarbonate diol and 12g of UV absorber Chiguard R-455, stir evenly, heat to 95℃, add 38g of hydrogenated MDI and 0.04g of catalyst dibutyltin dilaurate, stir at 95℃ and 400rpm for 2h. After the reaction is complete, add 4g of diol chain extender, continue stirring for 1h, cool after the reaction is complete to obtain anti-yellowing polyurethane; Step 6: Under nitrogen protection, mix 70g of anti-yellowing polyurethane and 30g of ethylpiperidinol modified cerium dioxide evenly, add it to a twin-screw extruder for extrusion, set the screw speed to 300rpm, the zone 1 temperature to 180℃, the zone 2 temperature to 190℃, the zone 3 temperature to 200℃, and the zone 4 temperature to 190℃. After extrusion, cool and granulate to obtain anti-yellowing TPU masterbatch.

[0027] Example 3: A method for preparing an anti-yellowing TPU masterbatch, specifically as follows: Step 1: Under nitrogen protection, 12g of hydroxyethylpiperidinol was added to 100mL of tetrahydrofuran and stirred until homogeneous. Then, 14g of hexamethylene diisocyanate and 0.03g of dibutyltin dilaurate catalyst were added. The mixture was stirred at 80℃ and 400rpm for 3h. After the reaction was completed, the mixture was distilled under reduced pressure to obtain NCO-terminated ethylpiperidinol. Step 2: Add 10g of nano-cerium dioxide to a mixture of 90mL ethanol and 10mL deionized water, stir evenly, sonicate for 10min, add 0.3g of silane coupling agent KH-550, adjust the pH to 5, stir at 70℃ and 400rpm for 8h, cool after the reaction is complete, filter, wash with ethanol and deionized water, and vacuum dry at 60℃ for 12h to obtain aminated nano-cerium dioxide; Step 3: Add 10g of aminated nano-cerium dioxide to 100mL of dimethyl sulfoxide, stir evenly, and ultrasonically disperse for 10min. Add 0.35g of NCO-terminated ethylpiperidinol and 0.01g of catalyst dibutyltin dilaurate. Stir and react at 90℃ and 400rpm for 12h. After the reaction is completed, centrifuge and wash with ethanol and deionized water. Dry under vacuum at 60℃ for 12h to obtain ethylpiperidinol modified cerium dioxide. Step 4: Add 14g of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and 6g of trimethylolpropane to 200mL of dichloromethane, stir until homogeneous, add 10g of dicyclohexyldiimide and 0.5g of catalyst 4-dimethylaminopyridine, stir at 30℃ and 400rpm for 12h, filter after the reaction is complete, wash the filtrate successively with 1wt% sodium hydroxide aqueous solution, saturated sodium bicarbonate aqueous solution and saturated sodium chloride aqueous solution, dry with anhydrous sodium sulfate, remove the solvent by rotary evaporation to obtain the diol chain extender; Step 5: Under nitrogen protection, mix 120g of polycarbonate diol and 14g of UV absorber Chiguard R-455, stir evenly, heat to 95℃, add 43g of hydrogenated MDI and 0.05g of catalyst dibutyltin dilaurate, stir at 95℃ and 400rpm for 2h. After the reaction is complete, add 4g of diol chain extender, continue stirring for 1h, cool after the reaction is complete to obtain anti-yellowing polyurethane; Step 6: Under nitrogen protection, mix 65g of anti-yellowing polyurethane and 35g of ethylpiperidinol modified cerium dioxide evenly, add it to a twin-screw extruder for extrusion, set the screw speed to 300rpm, the zone 1 temperature to 180℃, the zone 2 temperature to 190℃, the zone 3 temperature to 200℃, and the zone 4 temperature to 190℃. After extrusion, cool and granulate to obtain anti-yellowing TPU masterbatch.

[0028] Based on Example 1, the following comparative experiments were conducted, specifically Comparative Example 1, Comparative Example 2, and Comparative Example 3, as described below: Comparative Example 1: This comparative example relates to a method for preparing anti-yellowing TPU masterbatch. The difference from Example 1 is that the nano-cerium dioxide is only modified with silane coupling agent KH-550, specifically: Step 1: Add 5g of nano-cerium dioxide to a mixture of 90mL ethanol and 10mL deionized water, stir evenly, sonicate for 10min, add 0.2g of silane coupling agent KH-550, adjust the pH to 5, stir at 70℃ and 400rpm for 8h, cool after the reaction is complete, filter, wash with ethanol and deionized water, and vacuum dry at 60℃ for 12h to obtain aminated nano-cerium dioxide; Step 2: Under nitrogen protection, mix 75g of anti-yellowing polyurethane and 25g of aminated nano-cerium dioxide evenly, add it to a twin-screw extruder and extrude it. Set the screw speed to 300rpm, the temperature of zone 1 to 180℃, the temperature of zone 2 to 190℃, the temperature of zone 3 to 200℃, and the temperature of zone 4 to 190℃. After extrusion, cool and granulate to obtain anti-yellowing TPU masterbatch. The preparation method of the anti-yellowing polyurethane is the same as that in Example 1.

[0029] Comparative Example 2: This comparative example relates to a method for preparing anti-yellowing TPU masterbatch. The difference from Example 1 is that an equal mass of 1,4-butanediol is used instead of the diol chain extender. Specifically: Step 1: Under nitrogen protection, mix 100g of polycarbonate diol and 10g of UV absorber Chiguard R-455, stir until homogeneous, heat to 95℃, add 33g of hydrogenated MDI and 0.03g of catalyst dibutyltin dilaurate, stir at 95℃ and 400rpm for 2h. After the reaction is complete, add 4g of 1,4-butanediol, continue stirring for 1h, cool after the reaction is complete to obtain anti-yellowing polyurethane; Step 2: Under nitrogen protection, mix 75g of anti-yellowing polyurethane and 25g of ethylpiperidinol modified cerium dioxide evenly, add it to a twin-screw extruder for extrusion, set the screw speed to 300rpm, the temperature of zone 1 to 180℃, the temperature of zone 2 to 190℃, the temperature of zone 3 to 200℃, and the temperature of zone 4 to 190℃. After extrusion, cool and granulate to obtain anti-yellowing TPU masterbatch. The preparation method of ethylpiperidine alcohol modified cerium dioxide is the same as that in Example 1.

[0030] Comparative Example 3: This comparative example relates to a method for preparing an anti-yellowing TPU masterbatch. The difference from Example 1 is that the anti-yellowing polyurethane does not contain the UV absorber Chiguard R-455. Specifically: Step 1: Under nitrogen protection, mix 100g of polycarbonate diol and 33g of hydrogenated MDI, stir evenly, heat to 95℃, add 0.03g of catalyst dibutyltin dilaurate, stir at 95℃ and 400rpm for 2h. After the reaction is complete, add 4g of diol chain extender, continue stirring for 1h, cool after the reaction is complete to obtain anti-yellowing polyurethane; Step 2: Under nitrogen protection, mix 75g of anti-yellowing polyurethane and 25g of ethylpiperidinol modified cerium dioxide evenly, add it to a twin-screw extruder for extrusion, set the screw speed to 300rpm, the temperature of zone 1 to 180℃, the temperature of zone 2 to 190℃, the temperature of zone 3 to 200℃, and the temperature of zone 4 to 190℃. After extrusion, cool and granulate to obtain anti-yellowing TPU masterbatch. The preparation methods of the diol chain extender and the ethylpiperidinol modified cerium dioxide are the same as those in Example 1.

[0031] Testing experiment: Anti-yellowing TPU masterbatches were prepared according to the preparation methods in each embodiment and comparative example. They were then blended with TPU resin at a mass ratio of 1:3, extruded, and cast into a film to prepare an anti-yellowing TPU film. The following tests were then conducted.

[0032] Tensile property test: Refer to the standard "Determination of tensile properties of plastics - Part 3: Test conditions for films and sheets" (GB / T 1040.3-2006). Cut the specimen from the anti-yellowing TPU film. The total length of the specimen is 150 mm, the width is 25 mm, and the gauge length in the middle part of the specimen is 50 mm. Before the test, the specimen is conditioned at 25℃ and 50%RH for 24 h. During the test, the tensile speed of the universal testing machine is set to 50 mm / min. The tensile properties of the specimen are tested.

[0033] Yellowing resistance test: Referring to the standard "Determination of Yellowing Index and its Change Value of Plastics" (GB / T 39822-2021), a sample was cut from the anti-yellowing TPU film with a length of 150 mm and a width of 100 mm. Before the test, the sample was conditioned at 25℃ and 50%RH for 24 h. The initial yellowing index of the sample was measured using a colorimeter. Then, the sample was placed in UVA-340 ultraviolet light for 500 h of cycle aging. The cycle process was 60℃ UV light exposure for 8 h and 50℃ light avoidance for 4 h. After aging, the sample was taken out and conditioned at 25℃ and 50%RH for 24 h. The yellowing index of the sample after aging was measured and the change value of the yellowing index of the sample was calculated.

[0034] Performance testing after UV aging: Referring to the standard "Laboratory Light Source Test Methods for Plastics - Part 3: Fluorescent UV Lamp" (GB / T 16422.3-2022), samples were cut from the anti-yellowing TPU film with a length of 150 mm and a width of 100 mm. Before testing, the samples were conditioned at 25℃ and 50%RH for 24 hours, and the initial tensile strength of the samples was measured. Subsequently, the samples were placed in UVA-340 ultraviolet light for 500 hours of cyclic aging, with the cycle consisting of 8 hours of UV light exposure at 60℃ and 4 hours of light avoidance at 50℃. After aging, the samples were removed and conditioned at 25℃ and 50%RH for 24 hours. The tensile strength of the samples after aging was measured, and the tensile strength retention rate of the samples was calculated.

[0035]

[0036] Conclusion: The test data shows that, compared with Example 1, the yellow index of the anti-yellowing TPU film prepared from the masterbatch of Comparative Example 1 (without hydroxyethylpiperidinol-modified aminated nano-cerium dioxide), Comparative Example 2 (using 1,4-butanediol instead of diol chain extender), and Comparative Example 3 (without adding the UV absorber Chiguard R-455) all showed an increasing trend, while the tensile strength retention rate showed a decreasing trend. The anti-yellowing TPU masterbatch prepared in the examples, after further processing into an anti-yellowing TPU film, exhibited superior anti-yellowing and UV resistance compared to the comparative examples. The anti-yellowing TPU masterbatch provided by this invention possesses excellent anti-yellowing and UV resistance properties.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for preparing anti-yellowing TPU masterbatch, characterized in that: Specifically: Step 1: Mix hydroxyethylpiperidine alcohol with hexamethylene diisocyanate and react to obtain NCO-terminated ethylpiperidine alcohol; Step 2: Modify nano-cerium dioxide with silane coupling agent KH-550 to obtain aminated nano-cerium dioxide, and then react it with NCO-terminated ethylpiperidine alcohol to obtain ethylpiperidine alcohol-modified cerium dioxide; Step 3: Mix 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, trimethylolpropane and dicyclohexyldiimide and react to obtain a diol chain extender; Step 4: Mix and react polycarbonate diol, dicyclohexylmethane diisocyanate, reactive UV absorber and diol chain extender to obtain anti-yellowing polyurethane; Step 5: Melt-mix the anti-yellowing polyurethane with ethylpiperidine alcohol-modified cerium dioxide, extrude and granulate to obtain anti-yellowing TPU masterbatch.

2. The method for preparing an anti-yellowing TPU masterbatch according to claim 1, characterized in that: The preparation method of NCO-terminated ethylpiperidine alcohol is as follows: Under nitrogen protection, hydroxyethylpiperidine alcohol was added to tetrahydrofuran and stirred until homogeneous. Hexamethylene diisocyanate and dibutyltin dilaurate catalyst were then added. The mixture was stirred at 70-80℃ and 300-400 rpm for 2-4 hours. After the reaction was completed, the mixture was distilled under reduced pressure to obtain NCO-terminated ethylpiperidine alcohol.

3. The method for preparing an anti-yellowing TPU masterbatch according to claim 2, characterized in that: The mass ratio of hydroxyethylpiperidine alcohol, hexamethylene diisocyanate and catalyst dibutyltin dilaurate is (10-12):(10-14):(0.02-0.04).

4. The method for preparing an anti-yellowing TPU masterbatch according to claim 1, characterized in that: The preparation method of ethylpiperidine alcohol modified cerium dioxide is as follows: Nano-cerium dioxide was added to a mixture of ethanol and deionized water, stirred evenly, and ultrasonically dispersed for 10-20 min. Silane coupling agent KH-550 was added, and the pH was adjusted to 4-5. The mixture was stirred at 60-70℃ and 300-400 rpm for 8-10 h. After the reaction was completed, the mixture was cooled, filtered, washed with ethanol and deionized water, and vacuum dried at 60-70℃ for 10-12 h to obtain aminated nano-cerium dioxide. Aminated nano-cerium dioxide was added to dimethyl sulfoxide, stirred until homogeneous, and ultrasonically dispersed for 10-20 min. Then, terminal NCO ethylpiperidinol and catalyst dibutyltin dilaurate were added, and the mixture was stirred at 90-100℃ and 300-400 rpm for 10-12 h. After the reaction was completed, the mixture was centrifuged, washed with ethanol and deionized water, and vacuum dried at 60-70℃ for 10-12 h to obtain ethylpiperidinol modified cerium dioxide.

5. The method for preparing an anti-yellowing TPU masterbatch according to claim 4, characterized in that: The mass ratio of nano-cerium dioxide to silane coupling agent KH-550 is (5-10):(0.2-0.3); the mass ratio of aminated nano-cerium dioxide, NCO-terminated ethylpiperidinol, and catalyst dibutyltin dilaurate is (5-10):(0.25-0.35):(0.005-0.01).

6. The method for preparing an anti-yellowing TPU masterbatch according to claim 1, characterized in that: The preparation method of diol chain extender is as follows: 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid and trimethylolpropane were added to dichloromethane and stirred until homogeneous. Dicyclohexyldiimide and the catalyst 4-dimethylaminopyridine were then added. The mixture was stirred at 20-30°C and 300-400 rpm for 10-12 hours. After the reaction was completed, the mixture was filtered. The filtrate was washed successively with aqueous sodium hydroxide solution, saturated sodium bicarbonate solution, and saturated sodium chloride solution. The solution was dried over anhydrous sodium sulfate, and the solvent was removed by rotary evaporation to obtain the diol chain extender.

7. The method for preparing an anti-yellowing TPU masterbatch according to claim 6, characterized in that: The mass ratio of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid, trimethylolpropane, dicyclohexyldiimide and catalyst 4-dimethylaminopyridine is (10-14):(4-6):(6-10):(0.4-0.5).

8. The method for preparing an anti-yellowing TPU masterbatch according to claim 1, characterized in that: The preparation method of anti-yellowing polyurethane is as follows: Under nitrogen protection, polycarbonate diol and reactive UV absorber are mixed and stirred evenly. The mixture is heated to 90-100℃, and dicyclohexylmethane diisocyanate and dibutyltin dilaurate catalyst are added. The mixture is stirred at 90-100℃ and 300-400 rpm for 2-3 hours. After the reaction is completed, diol chain extender is added, and the mixture is stirred for another 1-2 hours. After the reaction is completed, the mixture is cooled to obtain anti-yellowing polyurethane.

9. The method for preparing an anti-yellowing TPU masterbatch according to claim 1, characterized in that: The mass ratio of anti-yellowing polyurethane to ethylpiperidine alcohol modified cerium dioxide in the anti-yellowing TPU masterbatch is (65-75):(25-35); the extrusion granulation process conditions include a screw speed of 200-300 rpm, a zone 1 temperature of 180-190℃, a zone 2 temperature of 190-200℃, a zone 3 temperature of 200-210℃, and a zone 4 temperature of 180-190℃.

10. The anti-yellowing TPU masterbatch prepared by the preparation method according to any one of claims 1-9, characterized in that: Application in anti-yellowing TPU products.

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