High-transparency fast-forming UV-resistant TPU material and preparation method thereof

Abstract

The invention provides a high-transparency fast-forming UV-resistant thermoplastic elastomer material and a preparation method thereof, and belongs to the field of polyurethane materials. According to the invention, 50-80 parts by weight of polyol, 10-30 parts by mass of isocyanate, 0.1-0.8 part by mass of an antioxidant, 0.1-1 part by mass of a nucleating agent, 2-12 parts by mass of a chain extender, 0.5-2 parts by mass of an anti-UV auxiliary agent and (10-300) * 10 <-6 > parts by weight of a catalyst are utilized to prepare the thermoplastic elastomer with the 6mm molding time of less than 60 seconds, the 6mm plate turbidity of less than or equal to 5.3% and the color difference E of less than or equal to 1.2.

Description

Technical Field

[0001] This invention relates to the field of thermoplastic polyurethane elastomers, and more particularly to a highly transparent, rapidly moldable, and UV-resistant thermoplastic elastomer material and its preparation method. Background Technology

[0002] With the continuous advancement and innovation of TPU (thermoplastic polyurethane) technology, it has become an ideal alternative to rubber and plastics in various fields such as consumer electronics, automobiles, medical devices, and sporting goods, thanks to its excellent elasticity, high strength, wide hardness range, and good abrasion resistance. Its applications are becoming increasingly widespread. Among these, soft TPU, due to its soft touch and excellent elastic recovery, is highly favored in the high-end consumer goods market, with significant demand for products such as smart wearable device watch straps, mobile phone cases, and transparent car covers.

[0003] However, as a block copolymer composed of soft segments (polyester or polyether) and hard segments (isocyanate and chain extender) linked by urethane bonds, soft TPU exhibits a natural correlation between transparency and crystallinity: reducing crystallinity significantly decreases the refractive index difference between crystalline and amorphous regions, preventing light scattering and thus improving transparency, but this directly leads to longer molding times and lower production efficiency. Conversely, low-hardness TPU inherently has a higher tendency to crystallize; increasing crystallinity to accelerate molding results in micro-phase separation with micro-region sizes exceeding the visible light wavelength range, causing the material to appear cloudy and failing to meet high transparency requirements. Furthermore, low-hardness TPU also suffers from injection molding demolding difficulties, further increasing manufacturing costs and hindering its expansion in the high-end market.

[0004] Besides the conflict between transparency and moldability, yellowing is another key challenge hindering TPU applications. While TPU itself is transparent and colorless, the benzene ring structure within the hard segments composed of aromatic isocyanates is prone to photo-oxidation under light, generating chromophores and causing the material to gradually yellow. For TPU, this yellowing phenomenon is significantly amplified, severely impacting product aesthetics and lifespan. To address yellowing, existing technologies typically add anti-yellowing agents such as UV absorbers and hindered amine light stabilizers. However, these agents do not match the refractive index of the TPU matrix, easily forming new light scattering centers, leading to increased haze and decreased transparency.

[0005] In materials modification research, researchers have tried various solutions to overcome the above bottlenecks, but all have limitations: using polyether-type polyols as soft segments can improve transparency, but the weak intermolecular forces of soft segments lead to low cohesive strength and insufficient mechanical properties; using aromatic isocyanates as hard segments can improve mechanical properties, but it will exacerbate photo-oxidative yellowing; adding multifunctional small molecule chain extenders to increase crosslinking density to improve mechanical properties will destroy the microphase separation structure of TPU and affect transparency; when inorganic nanomaterials are introduced for modification, the difference in refractive index between the matrix and the inorganic material will significantly increase the surface reflectance coefficient, further reducing transparency.

[0006] In summary, existing technologies present a technical challenge in achieving high transparency, rapid prototyping, and excellent UV resistance simultaneously with TPU. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a highly transparent, fast-forming, UV-resistant thermoplastic elastomer material and its preparation method, aiming to achieve a synergistic balance between high transparency, rapid molding, and excellent UV resistance in thermoplastic elastomer materials within a low hardness range.

[0008] The technical solution of the present invention is as follows: This invention provides a highly transparent, fast-forming, UV-resistant thermoplastic elastomer material, wherein the thermoplastic elastomer material comprises the following components in parts by weight: Polyols: 50-80 parts by weight; Isocyanate: 10-30 parts by weight; Antioxidant: 0.1-0.8 parts by weight; Nucleating agent: 0.1-1 parts by weight; Chain extender: 2-12 parts by weight; UV-resistant additive: 0.5-2 parts by weight; Catalyst: (10-300)×10 -6 ; The thermoplastic elastomer material has a molding time of less than 60 seconds for 6mm, a turbidity of 6mm plate of ≤5.3%, a color difference ΔE of ≤1.2, and a hardness of 65A-80A in an environment of 25±2℃ and 50%RH.

[0009] Furthermore, the polyol is a polyester diol containing at least two different number-average molecular weights, and the number-average molecular weight is 1500-4000 g / mol, preferably 1500-3000 g / mol; Choosing the above-mentioned number-average molecular weight polyester diols to form a block structure with the hard segments results in a more reasonable ratio. This retains the flexibility and elasticity of the soft segments while avoiding problems such as insufficient mechanical strength and easy deformation through the synergistic effect between molecular chains. This allows the material to have both a soft touch and sufficient durability and service life.

[0010] Further, the polyester diol is one or more of the following: polybutylene adipate diol, polybutylene adipate ethylene glycol diol, polyethylene adipate diol, polyhexane adipate diol, polyethylene adipate diethylene glycol diol, polyethylene adipate propylene glycol diol, polycaprolactone diol, or polycarbonate diol; Polyols of different molecular weights complement each other. The shorter molecular chains of the low molecular weight component result in better flowability, reducing light scattering sites within the melt and significantly lowering material turbidity, thus laying the foundation for high transparency. The higher molecular weight component has a higher degree of molecular chain entanglement, which can improve melt strength and crystallization rate, shortening the cooling and setting cycle during injection molding. The combination of the two avoids the problems of slow molding with low molecular weight polyols and poor transparency with high molecular weight polyols, achieving a synergistic balance between high transparency and rapid molding.

[0011] Furthermore, the polyol blend has a wider molecular weight distribution, enabling it to form a more uniform cross-linked network structure with isocyanates and chain extenders. The high molecular weight component provides ample molecular chain entanglement sites, enhancing the material's tensile strength and elastic recovery, ensuring it is less prone to deformation during use; the low molecular weight component adjusts melt viscosity, improving processing fluidity. This broad molecular weight distribution reduces the material's sensitivity to processing temperature fluctuations, resulting in a more uniform reaction during twin-screw extrusion and significantly improved batch-to-batch stability of product performance, thus balancing the processing and mechanical properties of thermoplastic materials.

[0012] In addition, polyols of different molecular weights have slight differences in polarity and solubility parameters. When compounded, they can provide a more suitable dispersion environment for functional additives such as nucleating agents and UV-resistant additives: low molecular weight components can improve the solubility of additives in the melt and prevent additives from agglomerating and forming light scattering centers; high molecular weight components can fix additive molecules through molecular chain adsorption and reduce their migration and precipitation.

[0013] Furthermore, the chain extender includes at least one of ethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol.

[0014] Furthermore, the nucleating agent includes at least one of aromatic phosphate salts, substituted benzoates, and sorbitols.

[0015] The addition of nucleating agents enables the rapid formation of numerous micro-crystal nuclei in thermoplastic elastomer materials during the melting and cooling process, altering the coarse grain structure that is prone to occur during traditional TPU crystallization. Aromatic phosphate salts and substituted benzoate nucleating agents have good molecular compatibility with the TPU matrix, can be uniformly dispersed, and act as crystallization centers, promoting the maintenance of small crystal sizes during growth and reducing light scattering. Sorbitol-based nucleating agents, through intermolecular hydrogen bonding, synergistically interact with the soft and hard segments of TPU, further refining the size of crystalline regions, reducing the refractive index difference between crystalline and amorphous regions, and significantly improving the uniformity and clarity of light transmission. Furthermore, these nucleating agents also improve molding time to some extent. The addition of nucleating agents provides sufficient active sites for TPU crystallization. Aromatic phosphate nucleating agents can significantly reduce the crystallization activation energy of TPU and shorten the crystal induction period; substituted benzoate nucleating agents can promote rapid crystal growth and form a regular crystal structure, reducing the cooling waiting time during molding; sorbitol nucleating agents can simultaneously optimize the crystallization rate and crystallinity, avoiding demolding difficulties caused by incomplete crystallization.

[0016] Further, the isocyanate includes at least one of diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), and isophorone diisocyanate (IPDI).

[0017] Furthermore, the antioxidant includes one or more of phosphites, phenols, amines, and sulfides.

[0018] Phenolic antioxidants, as the primary antioxidants, can efficiently capture hydroxyl and alkoxy free radicals generated during TPU processing and use, terminating free radical chain reactions and inhibiting material degradation. Phosphite antioxidants, as auxiliary antioxidants, can decompose hydroperoxides to generate stable products, preventing them from further initiating free radical reactions. They can also reduce oxidized phenolic antioxidants, achieving recycling. Amine antioxidants combine free radical scavenging and UV stabilization functions, providing targeted protection against the hard segments formed by aromatic isocyanates and delaying photo-oxidative yellowing. Sulfides enhance the system's anti-aging sustainability by decomposing hydroperoxides and improving antioxidant compatibility. When used alone or in combination, TPU retains ≥90% of its mechanical properties under harsh conditions such as high temperature and long-term light exposure, with a significant reduction in yellowing.

[0019] Furthermore, the UV-resistant additives include one or more of salicylates, benzophenones, benzotriazoles, substituted acrylonitriles, and triazines.

[0020] Different types of UV-resistant additives can block the photo-oxidation reaction of TPU through multiple mechanisms of action. Multiple UV-resistant additives can be compounded to improve the overall weather resistance and anti-yellowing performance of the material.

[0021] The aforementioned antioxidants, UV stabilizers, nucleating agents, and other additives exhibit good compatibility and can form a synergistic effect. When antioxidants and UV stabilizers are used together, the antioxidants scavenge thermo-oxidative free radicals, while the UV stabilizers block ultraviolet rays, further reducing the color difference ΔE of TPU after UV irradiation. When antioxidants and nucleating agents are used together, the antioxidants protect the nucleating agents from oxidative decomposition, ensuring continuous refinement of crystal nuclei and optimization of the crystal structure, resulting in a more balanced mechanical property while maintaining high transparency and rapid molding.

[0022] Furthermore, the catalyst includes one or more of the following: dibutyltin dilaurate, stannous octanoate, bismuth isooctanoate, tertiary amine catalysts, and organometallic catalysts.

[0023] Polyols and isocyanates react slowly at room temperature. The catalyst described above rapidly activates the isocyanate groups by lowering the activation energy, promoting the efficient combination of hydroxyl and isocyanate groups to form urethane bonds, thus significantly shortening the reaction time. Simultaneously, the introduction of the catalyst lowers the minimum temperature required for the reaction, reducing thermal damage to the raw materials caused by high temperatures.

[0024] This invention also provides a method for preparing the above-mentioned high-transparency, fast-forming, UV-resistant thermoplastic elastomer material, comprising the following steps: S1. A premix is ​​obtained by pre-mixing polyols, antioxidants and nucleating agents; S2. The premix, isocyanate, catalyst and chain extender obtained in step 1 are mixed and fed into the main feed port of a twin-screw extruder for reaction; S3. A UV-resistant additive is fed into the first exhaust port of a twin-screw extruder to obtain a high molecular polymer. S4. The polymer obtained in step 3 is reacted and extruded in a twin-screw extruder, and then granulated underwater to obtain solid particles; S5. The solid particles obtained in step 4 are cured to obtain the highly transparent, fast-forming, UV-resistant thermoplastic elastomer material.

[0025] Furthermore, the premix obtained in step 1 is conveyed under heat preservation at 90-120°C.

[0026] Furthermore, the temperature for maintaining the catalyst in step 2 is 20-60℃.

[0027] Furthermore, in step 3, the first vent of the twin-screw extruder is typically located in zone 8-12 of the twin-screw extruder; Furthermore, the underwater pelletizing temperature in step 4 is 10-40℃.

[0028] Furthermore, in step 5, the curing temperature is 30-90℃ and the curing time is 1-6 hours.

[0029] If the UV-resistant additive is added at the main feed port, located in Zone 1 of the twin-screw extruder, the material will undergo high-temperature heating and prolonged shearing throughout the entire process from Zone 1 to Zone 13. Although the UV-resistant additive has excellent thermal stability, during the extrusion stage, prolonged contact with reactive components such as isocyanates and polyols may still lead to slight decomposition or participation in side reactions, resulting in the loss of effective components. However, the first exhaust port is located in Zones 8-12 of the screw. At this point, the urethane bond formation reaction of TPU is basically complete, the system's reactivity is reduced, and the additive only needs to undergo a homogenization and cooling process after addition. During this process, the UV-resistant additive can be fixed at the interface between the crystalline and amorphous regions, reducing additive migration and loss during use, significantly reducing high-temperature exposure time, controlling the loss rate of effective components, and significantly increasing the effective concentration of the UV-resistant additive in the final product.

[0030] The beneficial effects of this application are as follows: 1. This invention achieves high transparency, rapid molding, and excellent UV resistance simultaneously within a low hardness range of 65A-80A, completely solving the technical problem in existing technologies that require sacrificing transparency to improve moldability and UV resistance. The turbidity of the 6mm thick sheet is ≤5.3%, with uniform and clear light transmission; the complete setting time of the 6mm thick injection molded part is less than 60 seconds, significantly improving production efficiency; after 3 hours of irradiation with a UVB313 lamp, the color difference ΔE is ≤1.2, effectively delaying yellowing and extending the product's service life.

[0031] 2. This invention employs a blend of two or more polyester diols with different number-average molecular weights. This not only achieves a balance between transparency and molding efficiency through molecular weight complementarity but also constructs a more uniform cross-linked network structure. While maintaining both softness and hardness, the material exhibits significantly improved mechanical properties such as tensile strength and elastic recovery, making it less prone to deformation during use and demonstrating excellent dimensional stability.

[0032] 3. The precise selection of nucleating agent in this invention refines the crystal size, avoids light scattering caused by coarse grains, further enhances the high transparency, and at the same time reduces the crystallization activation energy and shortens the molding cycle.

[0033] 4. The combination of antioxidants and UV-resistant additives creates a dual protection system that captures free radicals and blocks ultraviolet rays, which not only effectively inhibits photo-oxidative yellowing but also resists thermo-oxidative aging. Detailed Implementation

[0034] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0035] Example 1 S1. Premix a macromolecular polyester diol with a number average molecular weight of 2500 g / mol and an antioxidant; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 25℃. S4. The granulated solid particles are cured at 60°C for 3 hours to obtain TPU material.

[0036] In this embodiment, the macromolecular polyester diol is 72 parts by weight of polyether block polyamide PEBA; the chain extender is 5 parts by weight of 1,4-butanediol (1,4-BDO); ​​the diisocyanate is 22 parts by weight of MDI; the antioxidant is 0.4 parts by weight of 1010; and the catalyst is 150×10 -6 Parts by weight of stannous octoate.

[0037] Test sample preparation: TPU samples were dried in an oven at 100℃ for 4 hours and then injection molded into 6mm test pieces. The test pieces were then cured in an oven at 100℃ for 24 hours before performance testing.

[0038] Example 2 S1. Premix the macromolecular polyester diol and antioxidant; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 25℃. S4. The granulated solid particles are cured at 60°C for 3 hours to obtain TPU material.

[0039] In this embodiment, the macromolecular polyester diols are 36 parts by weight of PEBA with a number average molecular weight of 2000 g / mol and 36 parts by weight of PEBA with a number average molecular weight of 3000 g / mol; the chain extender is 5 parts by weight of 1,4-butanediol (1,4-BDO); ​​the diisocyanate is 22 parts by weight of MDI; the antioxidant is 0.4 parts by weight of 1010; and the catalyst is 150×10 -6 Parts by weight of stannous octoate.

[0040] As can be seen, the difference between Example 2 and Example 1 is that the macromolecular polyester diol was replaced with 36 parts by weight of PEBA with a number average molecular weight of 2000 g / mol and 36 parts by weight of PEBA with a number average molecular weight of 3000 g / mol. The other raw materials and process conditions remained unchanged.

[0041] The sample preparation and testing methods are the same as in Example 1.

[0042] Example 3 S1. Premix the macromolecular polyester diol, antioxidant and nucleating agent; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 25℃. S4. The granulated solid particles are cured at 60°C for 3 hours to obtain TPU material.

[0043] In this embodiment, the macromolecular polyester diols are 36 parts by weight of PEBA with a number average molecular weight of 2000 g / mol and 36 parts by weight of PEBA with a number average molecular weight of 3000 g / mol; the chain extender is 5 parts by weight of 1,4-butanediol (1,4-BDO); ​​the diisocyanate is 22 parts by weight of MDI; the antioxidant is 0.4 parts by weight of 1010; the nucleating agent is 0.5 parts by weight of a sorbitol-based nucleating agent, specifically WBQ-88; and the catalyst is 150 × 10⁻⁶. -6 Parts by weight of stannous octoate.

[0044] As can be seen, the difference between Example 3 and Example 2 is that a nucleating agent was added in step S1. The other raw materials and process conditions remained unchanged.

[0045] The sample preparation and testing methods are the same as in Example 1.

[0046] Example 4 S1. Premix the macromolecular polyester diol, antioxidant, nucleating agent and anti-UV additive; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 25℃. S4. The granulated solid particles are cured at 60°C for 3 hours to obtain TPU material.

[0047] In this embodiment, the macromolecular polyester diols are 36 parts by weight of PEBA with a number average molecular weight of 2000 g / mol and 36 parts by weight of PEBA with a number average molecular weight of 3000 g / mol; the chain extender is 5 parts by weight of 1,4-butanediol (1,4-BDO); ​​the diisocyanate is 22 parts by weight of MDI; the antioxidant is 0.4 parts by weight of 1010; the nucleating agent is 0.5 parts by weight of a sorbitol-based nucleating agent, specifically WBQ-88; the UV-resistant additive is 1 part by weight of VX-5566; and the catalyst is 150×10 -6 Parts by weight of stannous octoate.

[0048] As can be seen, the difference compared to Example 3 is that an anti-UV additive was added in step S1 of Example 4. The other raw materials and process conditions remain unchanged.

[0049] The sample preparation and testing methods are the same as in Example 1.

[0050] Example 5 S1. Premix the macromolecular polyester diol, antioxidant, and nucleating agent; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. A UV-resistant additive is fed into the first exhaust port of a twin-screw extruder to obtain a high molecular polymer. S4. The above-mentioned polymer is reacted and extruded in a twin-screw extruder. The temperature of the reaction section is 200°C and the temperature of the homogenization / cooling section is 120°C. Solid particles are obtained by underwater pelletizing at 25°C. S5. The granulated solid particles are cured at 60°C for 3 hours to obtain TPU material.

[0051] In this embodiment, the macromolecular polyester diols are 36 parts by weight of PEBA with a number average molecular weight of 2000 g / mol and 36 parts by weight of PEBA with a number average molecular weight of 3000 g / mol; the chain extender is 5 parts by weight of 1,4-butanediol (1,4-BDO); ​​the diisocyanate is 22 parts by weight of MDI; the antioxidant is 0.4 parts by weight of 1010; the nucleating agent is 0.5 parts by weight of a sorbitol-based nucleating agent, specifically WBQ-88; the UV-resistant additive is 1 part by weight of VX-5566; and the catalyst is 150×10 -6 Parts by weight of stannous octoate.

[0052] As can be seen, the difference compared to Example 4 is that in Example 5, the UV-resistant additive is added through the first vent of the twin-screw extruder in step S3. The first vent of the twin-screw extruder is located in zone 10 of the screw. The remaining raw materials and process conditions remain unchanged.

[0053] The sample preparation and testing methods are the same as in Example 1.

[0054] Example 6 S1. Premix a macromolecular polyester diol with a number average molecular weight of 2500 g / mol and an antioxidant; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 40℃. S4. The granulated solid particles are cured at 70°C for 5 hours to obtain TPU material.

[0055] In this embodiment, the macromolecular polyester diol is 60 parts by weight of polyhexyl adipate diol (PHA); the chain extender is 11 parts by weight of 1,6-hexanediol (1,6-HDO); the diisocyanate is 29 parts by weight of HDI; the antioxidant is 0.6 parts by weight of 1135; and the catalyst is 120×10 -6 Parts by weight of organic bismuth.

[0056] The sample preparation and testing methods are the same as in Example 1.

[0057] Example 7 S1. Premix the macromolecular polyester diol and antioxidant; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 40℃. S4. The granulated solid particles are cured at 70°C for 5 hours to obtain TPU material.

[0058] In this embodiment, the macromolecular polyester diol is 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 2000 g / mol and 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 3000 g / mol; the chain extender is 11 parts by weight of 1,6-hexanediol (1,6-HDO); the diisocyanate is 29 parts by weight of HDI; the antioxidant is 0.6 parts by weight of 1135; and the catalyst is 120×10 -6 Parts by weight of organic bismuth.

[0059] As can be seen, the difference compared to Example 6 is that in Example 7, the macromolecular polyester diol is replaced with 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 2000 g / mol and 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 3000 g / mol. The other raw materials and process conditions remain unchanged.

[0060] The sample preparation and testing methods are the same as in Example 1.

[0061] Example 8 S1. Premix the macromolecular polyester diol, antioxidant and nucleating agent; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 40℃. S4. The granulated solid particles are cured at 70°C for 5 hours to obtain TPU material.

[0062] In this embodiment, the macromolecular polyester diol is 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 2000 g / mol and 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 3000 g / mol; the chain extender is 11 parts by weight of 1,6-hexanediol (1,6-HDO); the diisocyanate is 29 parts by weight of HDI; the antioxidant is 0.6 parts by weight of 1135; the nucleating agent is 0.6 parts by weight of WNA-108; and the catalyst is 120×10 -6 Parts by weight of organic bismuth.

[0063] As can be seen, the difference compared to Example 7 is that a nucleating agent was added in step S1 of Example 8. The other raw materials and process conditions remain unchanged.

[0064] The sample preparation and testing methods are the same as in Example 1.

[0065] Example 9 S1. Premix the macromolecular polyester diol, antioxidant, nucleating agent and anti-UV additive; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 40℃. S4. The granulated solid particles are cured at 70°C for 5 hours to obtain TPU material.

[0066] In this embodiment, the macromolecular polyester diol is 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 2000 g / mol and 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 3000 g / mol; the chain extender is 11 parts by weight of 1,6-hexanediol (1,6-HDO); the diisocyanate is 29 parts by weight of HDI; the antioxidant is 0.6 parts by weight of 1135; the nucleating agent is 0.6 parts by weight of WNA-108; the UV-resistant additive is 1 part by weight of UV234; and the catalyst is 120×10 -6 Parts by weight of organic bismuth.

[0067] As can be seen, the difference compared to Example 8 is that an anti-UV additive was added in step S1 of Example 9. The other raw materials and process conditions remain unchanged.

[0068] The sample preparation and testing methods are the same as in Example 1.

[0069] Example 10 S1. Premix the macromolecular polyester diol, antioxidant, and nucleating agent; S2. The mixture obtained in step 1, diisocyanate, catalyst and chain extender are mixed and fed into the main feed port of a twin-screw extruder to carry out the reaction; S3. A UV-resistant additive is fed into the first exhaust port of a twin-screw extruder to obtain a high molecular polymer. S4. The material undergoes reaction extrusion in a twin-screw extruder. The temperature of the reaction section is 200℃, the temperature of the homogenization / cooling section is 120℃, and solid particles are obtained by underwater pelletizing at 40℃. S5. The granulated solid particles are cured at 70°C for 5 hours to obtain TPU material.

[0070] In this embodiment, the macromolecular polyester diol is 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 2000 g / mol and 30 parts by weight of polyhexyl adipate diol PHA with a number average molecular weight of 3000 g / mol; the chain extender is 11 parts by weight of 1,6-hexanediol (1,6-HDO); the diisocyanate is 29 parts by weight of HDI; the antioxidant is 0.6 parts by weight of 1135; the nucleating agent is 0.6 parts by weight of WNA-108; the UV-resistant additive is 1 part by weight of UV234; and the catalyst is 120×10 -6 Parts by weight of organic bismuth.

[0071] As can be seen, the difference compared to Example 9 is that in Example 10, the UV-resistant additive is added through the first vent of the twin-screw extruder in step S3. The first vent of the twin-screw extruder is located in zone 10 of the screw. The remaining raw materials and process conditions remain unchanged.

[0072] The sample preparation and testing methods are the same as in Example 1.

[0073] Table 1 lists the components and contents of the thermoplastic elastomers in Examples 1-10 of this paper.

[0074] Table 2 shows the properties of the materials used in Examples 1-10 of this invention.

[0075] The turbidity test standard for 6mm plates is ASTM D1003, and the UV index test standard is ASTM D1148.

[0076] As shown in Tables 1 and 2, comparing Examples 1 and 2, and Examples 6 and 7, the use of mixed macromolecular polyester diols with different molecular weights avoids the problems of slow molding with single low molecular weight polyols and poor transparency with single high molecular weight polyols, significantly shortening the molding time and effectively reducing turbidity compared to using a single molecular weight diol. This indicates that low molecular weight polyols help improve transparency, while high molecular weight polyols help accelerate molding. This invention uses two diols with different molecular weights, which not only improves transparency but also shortens the molding time.

[0077] Comparing Examples 2 and 3, and Examples 7 and 8, the addition of a nucleating agent to the mixed polyol altered the coarse grain structure that is prone to occur during the traditional TPU crystallization process. The addition of the nucleating agent further significantly reduced the turbidity, indicating that the nucleating agent effectively promoted the formation of smaller crystal nuclei, greatly improved transparency and gloss, and also slightly improved the molding time.

[0078] Comparing Examples 3 and 4, and Examples 8 and 9: the addition of an anti-UV additive (added together with the nucleating agent at the main feed inlet) to the formulation significantly improved UV performance (ΔE), indicating that the anti-UV additive played a key role. Turbidity increased slightly but remained at a low level.

[0079] Comparing Examples 4 and 5, and Examples 9 and 10: Adding the UV-resistant additive at the exhaust port significantly improved UV performance, indicating that this addition method more effectively preserves the function of the UV-resistant additive. Adding it at the exhaust port avoids prolonged high-temperature heating and shearing, thus maintaining its activity.

[0080] In summary, by optimizing the selection of raw materials (mixed molecular weight polyols), adding specific additives (nucleating agents and UV-resistant additives), and adopting key processes (adding UV-resistant additives through the exhaust port), this invention has successfully prepared a TPU material with high transparency, rapid molding, and excellent UV resistance within a hardness range of 65A-80A.

[0081] It should be understood that this application is not limited to the processes and structures described above, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A high transparent, fast-molding, UV resistant thermoplastic elastomer material, characterized in that, The thermoplastic elastomer material comprises the following components by weight: Polyol: 50-80 parts by weight; Isocyanate: 10-30 parts by mass; Antioxidant: 0.1-0.8 parts by mass; Nucleating agent: 0.1-1 parts by mass; Chain extender: 2-12 parts by mass; Anti-UV additive: 0.5-2 parts by mass; Catalyst: (10-300) x 10 -6 Parts by weight; The thermoplastic elastomer material has a 6mm molding time of less than 60 seconds, a 6mm plate haze of ≤5.3%, a color difference △E of ≤1.2, and a hardness of 65A-80A at 25±2℃ and 50% RH.

2. The highly transparent, rapid-molded, UV resistant thermoplastic elastomer material of claim 1, wherein, The polyol is a diol comprising at least two polyester diols with different number average molecular weights, and the number average molecular weight is 1500-4000 g / mol, preferably 1500-3000 g / mol.

3. The highly transparent, rapid-cure, UV resistant thermoplastic elastomer material of claim 1, wherein, The chain extender includes at least one of ethylene glycol, propylene glycol, butanediol, pentanediol, and hexanediol.

4. The highly transparent, rapid-cure, UV resistant thermoplastic elastomer material of claim 1, wherein, The nucleating agent includes at least one of aromatic phosphate salts, substituted benzoic acid salts, and sorbitol.

5. The highly transparent, rapid-cure, UV resistant thermoplastic elastomer material of claim 1, wherein, The isocyanate includes at least one of diphenylmethane diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, and isophorone diisocyanate.

6. The highly transparent, rapid-cure, UV resistant thermoplastic elastomer material of claim 1, wherein, The antioxidant includes one or more of phosphite, phenol, amine, and sulfide.

7. The highly transparent, rapid-cure, UV resistant thermoplastic elastomer material of claim 1, wherein, The anti-UV additive includes one or more of salicylate, benzophenone, benzotriazole, substituted acrylonitrile, and triazine.

8. The highly transparent, rapid-cure, UV resistant thermoplastic elastomer material of claim 1, wherein, The catalyst includes one or more of dibutyltin dilaurate, stannous octoate, bismuth isooctoate, tertiary amine catalyst, and organometallic catalyst.

9. A process for the preparation of a high transparent fast-molding UV resistant thermoplastic elastomeric material according to claims 1-8, characterized by, The method comprises the following steps: S1. Pre-mixing the polyol, antioxidant, and nucleating agent to obtain a pre-mix; S2. Mixing and feeding the pre-mix obtained in step 1, isocyanate, catalyst, and chain extender through the main feeding port of the twin-screw extruder to perform reaction; S3. Feeding the anti-UV additive through the first exhaust port of the twin-screw extruder to obtain a high molecular polymer; S4. Completing the reaction and extrusion of the high molecular polymer obtained in step 3 in the twin-screw extruder, and obtaining solid particles by underwater pelletizing; S5. Aging the solid particles obtained in step 4 to obtain the high-transparency, fast-molding, UV-resistant thermoplastic elastomer material.

10. The method of claim 9, wherein the high-transparency, rapid-molded, UV- resistant thermoplastic elastomer material is prepared by, The underwater pelletizing temperature is 10-40℃, the aging temperature is 30-90℃, and the aging time is 1-6 hours.

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