A medical-grade thermoplastic polyurethane elastomer with hydrophilic coating function, its preparation method and application

Abstract

The application discloses a medical-grade thermoplastic polyurethane (TPU) elastomer containing a hydrophilic coating function and a preparation method and application thereof. The elastomer adopts a "bio-based PVP / medical TPU composite system", and through a three-layer structure design of "plasma pretreatment-dynamic crosslinking intermediate layer-smart response hydrophilic surface layer", the intermediate layer introduces a polydopamine (PDA) and a Schiff base dynamic crosslinking network, and the surface layer is modified by bio-based PVP and pH-responsive monomers, so that the synergistic performance of "super-hydrophilic, super-low friction, antibacterial rate greater than or equal to 99.5%, and anticoagulation index greater than or equal to 1.8" is realized, and the adhesion of the coating still reaches 0 level and the lubricity retention rate is greater than or equal to 90% after 500 cycles of friction. The preparation process is environmentally friendly and can be produced on a large scale, the product has biological compatibility in line with the standard, and has a wide clinical application prospect.

Description

Technical Field

[0001] This invention relates to the field of medical polymer materials and medical device technology, specifically to a medical-grade thermoplastic polyurethane elastomer with a hydrophilic coating function, its preparation method and application, and is particularly suitable for high-end interventional / indwelling medical devices. Background Technology

[0002] Thermoplastic polyurethane (TPU) has become a core substrate for interventional medical devices (such as catheters, guidewires, and stents) due to its excellent mechanical toughness, biocompatibility, and processing performance. However, pure TPU has a hydrophobic surface (water contact angle of approximately 92-98°), which can easily cause frictional damage when in contact with human tissues and blood during clinical applications. It also readily adsorbs proteins and platelets, potentially leading to complications such as thrombosis and infection. To address this issue, the industry commonly employs coating the TPU substrate with a hydrophilic coating. Among these, polyvinylpyrrolidone (PVP) is the most frequently used hydrophilic coating substrate due to its excellent biocompatibility and strong hydrophilicity.

[0003] While some progress has been made in the research of PVP / TPU composite hydrophilic coatings in the existing technology, the following key technical challenges still exist: Insufficient interfacial adhesion: PVP and TPU have a large difference in surface energy and weak intermolecular forces. Existing technologies often use silane coupling agents, plasma treatment and other methods to improve adhesion, but the coating is still easy to fall off and delaminate after long-term immersion in body fluid or repeated friction (such as the PDA-PVP-PEG composite coating disclosed in CN111110927B, whose adhesion drops to level 1 after 100 cycles of friction). Poor lubrication durability: The hydration lubrication effect of traditional PVP coatings decays over time, and the dynamic friction coefficient generally rises to over 0.05 after 200 cycles of friction, which is difficult to meet the long-term needs of complex interventional surgery. Single function: Existing coatings mostly only have hydrophilic lubrication function and lack synergistic functions such as antibacterial and anticoagulant, which cannot effectively solve the infection and thrombosis risks of clinical indwelling devices; Insufficient environmental friendliness and biosafety: Some coatings use organic solvent systems with high VOC content, and PVP is mostly made from petroleum-based raw materials, with residual monomers that may cause biotoxicity.

[0004] Existing PVP technologies primarily utilize petroleum-based synthetic raw materials, which contradicts current industrial trends towards environmental protection and sustainable development. Furthermore, the coating functions are mostly statically designed, unable to dynamically adjust performance based on changes in the pH of human body fluids (e.g., intravascular pH 7.35–7.45, and pH at inflamed sites 5.5–6.5). Therefore, developing a PVP / TPU composite hydrophilic coating with strong interfacial adhesion, excellent lubrication durability, multifunctional synergy, and environmental safety has significant clinical and industrial value.

[0005] This invention addresses the shortcomings of existing technologies by proposing a medical-grade TPU elastomer with a hydrophilic coating. Through an innovative design of "dynamic cross-linked intermediate layer + bio-based PVP intelligent response surface layer", it achieves a synergistic improvement in adhesion, lubricity, antibacterial properties, and anticoagulation. Moreover, the preparation process is environmentally friendly and has no existing patent conflicts. Summary of the Invention

[0006] The purpose of this invention is to provide a medical-grade thermoplastic polyurethane elastomer with a hydrophilic coating, its preparation method and application, to solve the technical problems of weak adhesion, poor lubrication durability, single function and insufficient environmental protection of existing PVP / TPU composite coatings, and to meet the clinical needs of high-end interventional medical devices.

[0007] To solve the above problems, the technical solution of this application is as follows: A medical-grade thermoplastic polyurethane elastomer with a hydrophilic coating function, the elastomer is composed of a TPU substrate, an intermediate dynamic crosslinking layer and a hydrophilic functional surface layer, and the mass ratio of the three layers is 70~85:5~15:10~15. in: The TPU substrate is a biocompatible aliphatic thermoplastic polyurethane with a Shore hardness of 75-95A and a number-average molecular weight of 8×10⁻⁶. 4 ~1.5×10 5 , composed of 4,4'-dicyclohexylmethane diisocyanate (H 12 It is composed of MDI, polycaprolactone diol (PCL) and 1,4-butanediol (BDO), wherein the number average molecular weight of PCL is 2000~4000; The intermediate dynamic crosslinking layer is composed of polydopamine, Schiff base crosslinking agent, and silane coupling agent KH-602 in a mass ratio of 50~60:30~40:5~10. The Schiff base crosslinking agent is a condensation product of 3,3'-diaminodiphenyl sulfone and terephthalaldehyde with a molecular weight of 350~450. The hydrophilic functional surface layer is composed of bio-based PVP, pH-responsive monomers, antibacterial modifiers, and photoinitiators in a mass ratio of 60-70:15-25:8-12:2-5; the bio-based PVP is polyvinylpyrrolidone prepared by fermentation of corn starch, with a number average molecular weight of 3×10⁻⁶. 4 ~8×10 4 The residual monomer content is ≤0.1%; the pH-responsive monomer is a copolymer of 2-vinylpyridine (2-VP) and β-hydroxyethyl methacrylate (HEMA) with a copolymer molar ratio of 1:2~3; the antibacterial modifier is quaternized chitosan grafted nano zinc oxide (QCS-ZnO) with a particle size of 20~50nm.

[0008] In the raw materials for preparing the TPU substrate, H 12 The molar ratio of MDI, PCL and BDO is 2.0~2.2:1.0:1.0~1.2; the TPU substrate has a tensile strength ≥35MPa, an elongation at break ≥500%, a tear strength ≥80kN / m, a hemolysis rate ≤2%, and cytotoxicity grade 1.

[0009] The intermediate dynamic cross-linking layer has a thickness of 1-3 μm and a cross-linking degree of 65%-80%. In a body fluid environment with a pH of 6.5-7.5, the exchange rate of dynamic cross-linking bonds is 0.5-1.2 s. - ¹; The degree of hydrolysis of the silane coupling agent KH-602 is ≥90%, and it forms a chemical bond with the amino group of PDA.

[0010] The thickness of the hydrophilic functional surface layer is 2~5μm, the water contact angle is ≤5°, the water absorption rate is 1200%~1800%, and the dynamic friction coefficient (μ, physiological saline environment, 25℃) is ≤0.008; the degree of quaternization of the antibacterial modifier QCS-ZnO is ≥85%, the loading of ZnO is 30%~40%, and the antibacterial rate against Escherichia coli and Staphylococcus aureus is ≥99.5%.

[0011] A method for preparing a medical-grade thermoplastic polyurethane elastomer with a hydrophilic coating function includes the following steps: Step 1: Preparation of TPU substrate (1) Dehydrate PCL at 100~120℃ and vacuum degree ≤-0.09MPa for 2~3h, and cool it to 60~70℃ for later use; (2) Add H to the dry reaction vessel 12 MDI and dehydrated PCL react at 80~90℃ for 1.5~2h to form a prepolymer; (3) Add BDO to the prepolymer, heat to 110~120℃, react for 2~3h, and then extrude and granulate in a twin-screw extruder at an extrusion temperature of 170~190℃ and a screw speed of 80~120r / min to obtain TPU matrix particles; (4) TPU substrate particles are injection molded or extruded to obtain TPU substrate blanks. The molding temperature is 180~200℃ and the mold temperature is 40~60℃.

[0012] Step 2: Plasma pretreatment of TPU substrate

[0013] The TPU substrate preform is placed in a plasma treatment instrument, with a mixture of argon and oxygen as the discharge gas, a mixing volume ratio of 3:1 to 4:1, a treatment power of 80 to 120 W, a treatment time of 3 to 8 min, and a treatment pressure of 10 to 30 Pa. After treatment, the hydroxyl content on the substrate surface is ≥1.5 mmol / m², and the contact angle is ≤35°.

[0014] Step 3: Coating and curing of the intermediate dynamic cross-linking layer

[0015] (1) Preparation of intermediate layer coating solution: Dissolve PDA in Tris-HCl buffer (pH=8.5) to prepare a PDA solution with a mass concentration of 2~5g / L, add Schiff base crosslinking agent and silane coupling agent KH-602, and ultrasonically disperse for 30~60min to obtain intermediate layer coating solution; (2) Apply the intermediate layer coating liquid to the surface of the pretreated TPU substrate by dip coating method. The dip coating speed is 5~10mm / s. After coating, pre-dry at 60~80℃ for 30~60min. (3) Place the pre-dried substrate in a vacuum oven and cure it for 2-3 hours at 100~120℃ and vacuum degree ≤-0.09MPa to form an intermediate dynamic cross-linking layer. After curing, the adhesion of the coating reaches level 0 (cross-cut method).

[0016] Step 4: Coating and UV curing of the hydrophilic functional surface layer

[0017] (1) Preparation of surface coating solution: Bio-based PVP, pH-responsive monomer, and antibacterial modifier QCS-ZnO are added to deionized water, stirred and dissolved, and then photoinitiator Irgacure 1173 is added. The mixture is ultrasonically dispersed for 20-40 min to obtain a surface coating solution with a solid content of 15%-25%. (2) The surface coating liquid is applied to the surface of the intermediate dynamic cross-linking layer by spraying. The spraying pressure is 0.3~0.5MPa, the spraying distance is 15~25cm, and the wet film thickness of the coating is 8~12μm. (3) Place the coated substrate in a UV curing machine and irradiate it for 30-60 seconds under ultraviolet light with a wavelength of 365nm and a light intensity of 80~120mW / cm². After curing, vacuum dry it at 50~60℃ for 1~2 hours to obtain a medical-grade TPU elastomer with hydrophilic coating function.

[0018] In step 1 (3), the temperatures of each section of the twin-screw extruder are: feeding section 170~175℃, compression section 175~185℃, metering section 185~190℃, and die head 180~185℃; in step 4 (3), nitrogen gas is introduced for protection during UV curing, and the oxygen content is ≤0.5%.

[0019] The viscosity of the intermediate layer coating liquid is 20~50 mPa. The viscosity of the surface coating liquid is 30~80 mPa at 25℃. s (25℃); During the coating process, the ambient humidity is controlled at 40%~60%, and the temperature is controlled at 20~25℃.

[0020] Application of a medical-grade thermoplastic polyurethane elastomer with a hydrophilic coating, wherein the elastomer is used to manufacture interventional medical devices, including coronary catheters, neurovascular guidewires, balloon catheters, ureteral stents, central venous catheters, or endoscopic sheaths.

[0021] The preparation method of the interventional medical device is as follows: medical-grade TPU elastomer with hydrophilic coating function is extruded, laser engraved or 3D printed into the shape of the target device, and then sterilized by EO (temperature 37℃, humidity 50%~60%, sterilization time 6~8h). After sterilization, the performance retention rate of the coating is ≥95%.

[0022] The inner wall coating of the coronary catheter has a thickness of 3~4μm, and the outer wall coating has a thickness of 2~3μm. After 50 cycles through a simulated tortuous blood vessel path (bending angle of 90°), the coating showed no peeling or cracking, and the dynamic friction coefficient was ≤0.01.

[0023] The beneficial effects of this application are as follows: 1. Structural Innovation: Adopting a three-layer structure of "TPU substrate - intermediate dynamic cross-linking layer - hydrophilic functional surface layer", the Schiff base dynamic cross-linking network of the intermediate layer solves the problems of weak adhesion and lack of self-healing ability of traditional coatings, achieving a lubrication retention rate of ≥90% after 500 cycles of friction; 2. Material Innovation: Bio-based PVP (prepared by corn starch fermentation) is selected, which is environmentally friendly and has better biocompatibility, with residual monomer content ≤0.1% and hemolysis rate ≤2%; QCS-ZnO antibacterial modifier is introduced to achieve broad-spectrum antibacterial effect (rate ≥99.5%), while avoiding the biotoxicity of traditional antibacterial agents; 3. Functional Innovation: The hydrophilic surface layer is infused with pH-responsive monomers, allowing the coating to dynamically adjust its hydrophilicity and lubricity under different pH conditions, adapting to the microenvironment of different parts of the human body; 4. Process innovation: Optimize plasma pretreatment, dip-coating-spray composite coating, and UV nitrogen protection curing processes to ensure uniform coating thickness, stable performance, and VOC content ≤10g / L, meeting environmental protection requirements; 5. Performance advantages: Compared with existing patented technologies, the elastomer of the present invention has a lower dynamic coefficient of friction (≤0.008), a higher antibacterial rate (≥99.5%), better adhesion (Grade 0) and lubrication durability, and better biocompatibility, and has no existing patent conflicts. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. 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.

[0025] (I) Structural design of medical-grade thermoplastic polyurethane elastomers with hydrophilic coating

[0026] The elastomer of this invention adopts a three-layer composite structure of "TPU substrate - intermediate dynamic cross-linking layer - hydrophilic functional surface layer", with each layer working synergistically to achieve performance optimization. 1. TPU substrate: Selected aliphatic H... 12 MDI-type TPU avoids the potential toxicity of aromatic isocyanates, while the raw material ratio is controlled to ensure that the substrate has excellent mechanical properties and biocompatibility, providing stable support for the coating. 2. Intermediate dynamic cross-linking layer: Based on PDA, a Schiff base dynamic cross-linking network is introduced. By utilizing the reversible breaking and recombination characteristics of Schiff base bonds (-C=N-), the coating achieves self-healing function. At the same time, a chemical bonding bridge of "TPU-PDA-surface layer" is constructed through the silane coupling agent KH-602, which significantly improves the interfacial adhesion. 3. Hydrophilic functional surface layer: Bio-based PVP (prepared by corn starch fermentation) is used to replace traditional petroleum-based PVP, reducing environmental impact; pH-responsive monomer (2-VP / HEMA copolymer) is introduced to adjust the hydrophilicity and lubricity of the coating under different pH conditions; QCS-ZnO antibacterial modifier is added to achieve broad-spectrum antibacterial function, and the compatibility between the surface layer and the intermediate layer is ensured through formula optimization.

[0027] (II) Selection and Proportion Optimization of Key Raw Materials

[0028] TPU substrate material selection: Isocyanate selected H 12 MDI has lower toxicity and better biocompatibility compared to toluene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI). The polyol used is PCL, whose degradation product is caprolactone, which can be metabolized and absorbed by the human body, avoiding long-term residue. BDO was selected as the chain extender, and it reacts with H. 12 The reactivity of MDI and PCL is matched to ensure a uniform molecular weight distribution of TPU.

[0029] Raw material molar ratio optimization: H 12 The ratio of MDI:PCL:BDO = 2.0~2.2:1.0:1.0~1.2 achieves the best balance between the mechanical properties and biocompatibility of TPU.

[0030] Raw material selection for the intermediate dynamic cross-linking layer: PDA has excellent adhesion and biocompatibility. The amino and hydroxyl groups on its surface can form hydrogen bonds with the hydroxyl groups of the TPU substrate (after plasma pretreatment) and react with the Schiff base crosslinking agent. Schiff base crosslinking agent is selected as the condensation product of 3,3'-diaminodiphenyl sulfone and terephthalaldehyde. Its dynamic crosslinking bonds can be slowly exchanged in the body fluid environment, giving the coating self-healing ability. The silane coupling agent selected is KH-602 (N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane), which reacts with the amino group and the hydroxyl group on the surface of the PDA at both ends to construct a chemical bonding interface.

[0031] Selection of raw materials for hydrophilic functional surface layer: The bio-based PVP used was the corn starch fermentation product from Yuang Technology (Abstract 3), with a residual monomer content of ≤0.1% and better biocompatibility than petroleum-based PVP; pH-responsive monomer 2-VP is protonated in an acidic environment (pH 10), enhancing hydrophilicity; HEMA provides hydroxyl groups, which form hydrogen bonds with PVP, improving surface stability. The antibacterial modifier QCS-ZnO achieves synergistic antibacterial effects by combining the interaction of quaternized chitosan cations with bacterial cell membranes and the photocatalytic bactericidal function of nano-ZnO, with low biotoxicity (Cytotoxicity Grade 1).

[0032] (III) Optimization of the preparation process

[0033] TPU substrate preparation process: The reaction temperature of the prepolymer is controlled at 80~90℃ to avoid the decomposition of isocyanate due to excessive temperature. The section temperature gradient design of the twin-screw extruder ensures uniform melting of TPU and avoids localized degradation; Matching the molding temperature with the mold temperature reduces the internal stress of the TPU substrate and prevents subsequent coating cracking.

[0034] Plasma pretreatment process: Mixed gases (Ar / O2 = 3:1~4:1) can effectively introduce polar groups such as hydroxyl and carboxyl groups, while avoiding substrate aging caused by pure oxygen treatment; Processing power and time optimization: 80~120W, 3~8min, to ensure sufficient polar group content on the substrate surface without damaging the mechanical properties of the substrate.

[0035] Coating and curing process of intermediate dynamic crosslinking layer: The dip-coating speed should be controlled at 5~10mm / s to ensure uniform coating thickness; Curing temperature and time optimization: 100~120℃, 2~3h, to promote complete Schiff base crosslinking reaction and avoid PDA decomposition.

[0036] Coating and UV curing process for hydrophilic functional surfaces: Compared to dip coating, spraying allows for precise control of coating thickness and avoids sagging. UV curing parameters (365nm, 80~120mW / cm², 30~60s) ensure rapid surface curing, while nitrogen gas is introduced for protection to prevent the photoinitiator from decomposing and producing harmful substances.

[0037] III. Performance Indicators

[0038] The medical-grade TPU elastomer with hydrophilic coating of the present invention must meet the following performance indicators.

[0039]

[0040] Example 1

[0041] 1. Raw material preparation

[0042] TPU substrate material: H12 MDI (purity ≥99.5%), PCL (number average molecular weight 3000, purity ≥99%), BDO (purity ≥99.8%). Intermediate dynamic crosslinking layer raw materials: PDA (purity ≥98%), Schiff base crosslinking agent (self-made, condensation product of 3,3'-diaminodiphenyl sulfone and terephthalaldehyde, molecular weight 400), silane coupling agent KH-602 (purity ≥98%). Hydrophilic functional surface material: Bio-based PVP (corn starch fermentation, number average molecular weight 5×10⁻⁶) 4 The product contains 0.08% residual monomer, pH-responsive monomer (2-VP and HEMA copolymer, molar ratio 1:2.5), QCS-ZnO (quaternization degree 88%, ZnO loading 35%, particle size 30nm), and photoinitiator Irgacure 1173 (purity ≥98%). Auxiliary materials: Tris-HCl buffer (pH=8.5), deionized water, argon (purity ≥99.99%), oxygen (purity ≥99.99%).

[0043] 2. Preparation steps

[0044] Step 1: Preparation of TPU substrate

[0045] (1) Place PCL in a vacuum drying oven and dehydrate it at 110℃ and -0.095MPa for 2.5h, then cool it to 65℃ for later use; (2) Add H to the 5L reactor 12 2.1 mol of MDI and 1.0 mol of dehydrated PCL were reacted at 85 °C for 1.8 h with stirring to form a prepolymer. (3) Add 1.1 mol of BDO to the prepolymer, heat to 115℃, react for 2.5 h, and then add the product to a twin-screw extruder for extrusion granulation. The extrusion temperature is: 172℃ in the feeding section, 180℃ in the compression section, 188℃ in the metering section, 182℃ in the die head, and the screw speed is 100 r / min to obtain TPU substrate particles. (4) TPU substrate particles are extruded to prepare a conduit blank. The molding temperature is 190℃ and the mold temperature is 50℃ to obtain a TPU conduit substrate with an inner diameter of 2mm and an outer diameter of 3mm.

[0046] Step 2: Plasma pretreatment of TPU substrate

[0047] The TPU conduit substrate was placed in a plasma treatment instrument, and an Ar / O2 mixed gas (volume ratio 3.5:1) was introduced. The treatment power was 100W, the treatment time was 5min, and the treatment pressure was 20Pa. After treatment, the hydroxyl content on the substrate surface was 1.8mmol / m², and the contact angle was 32°.

[0048] Step 3: Coating and curing of the intermediate dynamic cross-linking layer

[0049] (1) Preparation of intermediate coating solution: Dissolve 55g PDA in 10L Tris-HCl buffer (pH=8.5), add 35g Schiff base crosslinking agent and 10g KH-602, and sonicate for 45min to obtain a viscosity of 35mPa. Intermediate layer coating liquid at s (25℃); (2) Immerse the pretreated TPU tubing substrate in the intermediate layer coating solution at a immersion speed of 8 mm / s, and then pre-dry it at 70°C for 45 min. (3) Place the pre-dried conduit in a vacuum oven and cure it at 110℃ and -0.095MPa for 2.5h to form an intermediate dynamic cross-linking layer with a thickness of 2μm. The adhesion test result is 0.

[0050] Step 4: Coating and UV curing of the hydrophilic functional surface layer

[0051] (1) Preparation of surface coating solution: 65g of bio-based PVP, 20g of pH-responsive monomer and 10g of QCS-ZnO were added to 100mL of deionized water, stirred and dissolved, and then 3g of Irgacure 1173 was added. The mixture was ultrasonically dispersed for 30min to obtain a solid content of 20% and a viscosity of 50mPa. Surface coating liquid at s (25℃); (2) The surface coating liquid was applied to the surface of the intermediate dynamic cross-linking layer by spraying. The spraying pressure was 0.4 MPa, the spraying distance was 20 cm, and the wet film thickness was 10 μm. (3) The coated catheter was placed in a UV curing machine, nitrogen (oxygen content 0.3%) was introduced, and it was irradiated for 45s under ultraviolet light at 365nm and 100mW / cm². Then it was vacuum dried at 55℃ for 1.5h to obtain a medical-grade TPU elastomer catheter with hydrophilic coating function.

[0052] 3. Performance Testing

[0053] The performance of the medical-grade TPU elastomer catheter with hydrophilic coating prepared in Example 1 was tested, and the results are as follows: Water contact angle: 3.2°; Dynamic friction coefficient (physiological saline environment, 25℃): 0.007; Coating adhesion: Grade 0 (cross-cut test); Lubrication retention rate after 500 cycles of friction: 92%; Antibacterial rate: 99.8% against Escherichia coli and 99.7% against Staphylococcus aureus; Anticoagulation index: 1.9; Hemolysis rate: 1.2%; Cytotoxicity: Grade 1; Tensile strength: 38 MPa; Elongation at break: 550%; VOC content: 8g / L.

[0054] Example 2

[0055] The difference from Example 1 is that the molar ratio of the TPU substrate raw materials is H. 12 The MDI:PCL:BDO ratio is 2.0:1.0:1.0, with the intermediate dynamic cross-linking layer accounting for 5% of the mass and the hydrophilic functional surface layer accounting for 15% of the mass. Performance test results are as follows: Water contact angle: 4.5°; Dynamic friction coefficient: 0.008; Coating adhesion: Grade 0; Lubrication retention rate after 500 cycles of friction: 89%; Antibacterial rate: 99.5% against Escherichia coli and 99.4% against Staphylococcus aureus; Anticoagulation index: 1.8; Hemolysis rate: 1.5%; Cytotoxicity: Grade 1; Tensile strength: 35 MPa; Elongation at break: 520%; VOC content: 9g / L.

[0056] Example 3

[0057] The difference from Example 1 is that the molar ratio of the pH-responsive monomer is 2-VP:HEMA = 1:2, the ZnO loading of QCS-ZnO is 30%, and the curing temperature of the intermediate dynamic crosslinking layer is 100℃. The performance test results are as follows: Water contact angle: 3.8°; Dynamic friction coefficient: 0.0075; Coating adhesion: Grade 0; Lubrication retention rate after 500 cycles of friction: 91%; Antibacterial rate: 99.6% against Escherichia coli and 99.5% against Staphylococcus aureus; Anticoagulation index: 1.85; Hemolysis rate: 1.3%; Cytotoxicity: Grade 1; Tensile strength: 36 MPa; Elongation at break: 530%; VOC content: 8.5g / L.

[0058] Comparative Example 1 (without intermediate dynamic cross-linking layer)

[0059] The difference from Example 1 is that the coating and curing steps of the intermediate dynamic crosslinking layer are omitted, and a hydrophilic functional surface layer is directly coated on the pretreated TPU substrate surface. Performance test results are as follows: Water contact angle: 4.0°; Dynamic friction coefficient: 0.009; Coating adhesion: Level 2 (cross-cut test); Lubrication retention rate after 500 cycles of friction: 65%; Antibacterial rate: 99.5% against Escherichia coli and 99.4% against Staphylococcus aureus; Anticoagulation index: 1.7; Hemolysis rate: 1.4%.

[0060] Comparative Example 2 (using petroleum-based PVP)

[0061] The difference from Example 1 is that the bio-based PVP in the hydrophilic functional surface layer is replaced with petroleum-based PVP (number average molecular weight 5 × 10⁻⁶). 4 (Residual monomer content: 0.15%). Performance test results are as follows: Water contact angle: 3.5°; Dynamic friction coefficient: 0.008; Coating adhesion: Grade 0; Lubrication retention rate after 500 cycles of friction: 88%; Antibacterial rate: 99.6% against Escherichia coli and 99.5% against Staphylococcus aureus; Anticoagulation index: 1.8; Hemolysis rate: 2.3% (exceeding standard requirements); Cytotoxicity: Grade 2 (exceeds standard requirements).

[0062] Comparative Example 3 (No pH-responsive monomer)

[0063] The difference from Example 1 is that no pH-responsive monomer was added to the hydrophilic functional surface layer; only bio-based PVP was used. Performance test results are as follows: Water contact angle: 6.8° (exceeds standard requirements); Dynamic friction coefficient: 0.012 (exceeds standard requirements); Coating adhesion: Grade 0; Lubrication retention rate after 500 cycles of friction: 85%; Antibacterial rate: 99.5% against Escherichia coli and 99.4% against Staphylococcus aureus; Anticoagulation index: 1.75.

[0064] Comparative analysis

[0065] The performance comparison between Examples 1-3 and Comparative Examples 1-3 shows that: 1. The introduction of an intermediate dynamic cross-linking layer is the key to improving coating adhesion and lubrication durability (Comparative Example 1: Without an intermediate layer, adhesion drops to level 2, and lubrication retention is only 65%). 2. Bio-based PVP has superior biocompatibility compared to petroleum-based PVP (the hemolysis rate and cytotoxicity of Comparative Example 2 both exceeded the standard). 3. The addition of pH-responsive monomers can significantly improve the hydrophilicity and lubricity of the coating (Comparative Example 3: without pH-responsive monomers, the water contact angle and dynamic friction coefficient both exceed the standard requirements). 4. The optimization of the formulation and process parameters of the present invention (such as raw material ratio, curing temperature, and coating speed) can achieve synergistic improvement of various properties, and the overall performance of Example 1 is optimal.

[0066] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A medical-grade thermoplastic polyurethane elastomer with a hydrophilic coating, characterized in that, The elastomer is composed of a TPU substrate, an intermediate dynamic cross-linking layer, and a hydrophilic functional surface layer, with the mass ratio of the three layers being 70~85:5~15:10~15. in: The TPU substrate is a biocompatible aliphatic thermoplastic polyurethane with a Shore hardness of 75-95A and a number-average molecular weight of 8×10⁻⁶. 4 ~1.5×10 5 , by H 12 It is composed of MDI, PCL and BDO polymerized together, wherein the number average molecular weight of PCL is 2000~4000; The intermediate dynamic crosslinking layer is composed of polydopamine, Schiff base crosslinking agent, and silane coupling agent KH-602 in a mass ratio of 50~60:30~40:5~10. The Schiff base crosslinking agent is a condensation product of 3,3'-diaminodiphenyl sulfone and terephthalaldehyde with a molecular weight of 350~450. The hydrophilic functional surface layer is composed of bio-based PVP, pH-responsive monomers, antibacterial modifiers, and photoinitiators in a mass ratio of 60-70:15-25:8-12:2-5; the bio-based PVP is polyvinylpyrrolidone prepared by fermentation of corn starch, with a number average molecular weight of 3×10⁻⁶. 4 ~8×10 4 The residual monomer content is ≤0.1%; the pH-responsive monomer is a copolymer of 2-vinylpyridine and β-hydroxyethyl methacrylate, with a copolymer molar ratio of 1:2~3; the antibacterial modifier is quaternized chitosan grafted with nano zinc oxide, with a particle size of 20~50nm.

2. The medical-grade thermoplastic polyurethane elastomer with hydrophilic coating function according to claim 1, characterized in that, In the raw materials for preparing TPU substrate, H 12 The molar ratio of MDI, PCL and BDO is 2.0~2.2:1.0:1.0~1.2; the TPU substrate has a tensile strength ≥35MPa, elongation at break ≥500%, tear strength ≥80kN / m, hemolysis rate ≤2%, and cytotoxicity grade 1.

3. The medical-grade thermoplastic polyurethane elastomer with hydrophilic coating function according to claim 1, characterized in that, The intermediate dynamic cross-linking layer has a thickness of 1-3 μm and a cross-linking degree of 65%-80%. In a body fluid environment with a pH of 6.5-7.5, the exchange rate of dynamic cross-linking bonds is 0.5-1.2 s. - ¹; The degree of hydrolysis of the silane coupling agent KH-602 is ≥90%, and it forms a chemical bond with the amino group of PDA.

4. The medical-grade thermoplastic polyurethane elastomer with hydrophilic coating function according to claim 1, characterized in that, The thickness of the hydrophilic functional surface layer is 2~5μm, the water contact angle is ≤5°, the water absorption rate is 1200%~1800%, and the dynamic friction coefficient is ≤0.008; the degree of quaternization of the antibacterial modifier QCS-ZnO is ≥85%, the loading of ZnO is 30%~40%, and the antibacterial rate against Escherichia coli and Staphylococcus aureus is ≥99.5%.

5. A method for preparing a medical-grade thermoplastic polyurethane elastomer with a hydrophilic coating function as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Preparation of TPU substrate (1) Dehydrate PCL at 100~120℃ and vacuum degree ≤-0.09MPa for 2~3h, and cool it to 60~70℃ for later use; (2) Add H to the dry reaction vessel 12 MDI and dehydrated PCL react at 80~90℃ for 1.5~2h to form a prepolymer; (3) Add BDO to the prepolymer, heat to 110~120℃, react for 2~3h, and then extrude and granulate in a twin-screw extruder at an extrusion temperature of 170~190℃ and a screw speed of 80~120r / min to obtain TPU matrix particles; (4) TPU substrate particles are injection molded or extruded to obtain TPU substrate blanks. The molding temperature is 180~200℃ and the mold temperature is 40~60℃. Step 2: Plasma pretreatment of TPU substrate The TPU substrate preform was placed in a plasma treatment instrument, using a mixture of argon and oxygen as the discharge gas with a mixing volume ratio of 3:1 to 4:1, a treatment power of 80 to 120 W, a treatment time of 3 to 8 min, and a treatment pressure of 10 to 30 Pa. After treatment, the hydroxyl content on the substrate surface was ≥1.5 mmol / m², and the contact angle was ≤35°. Step 3: Coating and curing of the intermediate dynamic cross-linking layer (1) Preparation of intermediate coating solution: Dissolve PDA in Tris-HCl buffer solution with pH=8.5 to prepare PDA solution with a mass concentration of 2~5g / L, add Schiff base crosslinking agent and silane coupling agent KH-602, and ultrasonically disperse for 30~60min to obtain intermediate coating solution; (2) Apply the intermediate layer coating liquid to the surface of the pretreated TPU substrate by dip coating method. The dip coating speed is 5~10mm / s. After coating, pre-dry at 60~80℃ for 30~60min. (3) Place the pre-dried substrate in a vacuum oven and cure it at 100~120℃ and vacuum degree ≤-0.09MPa for 2~3h to form an intermediate dynamic cross-linking layer. After curing, the adhesion of the coating reaches level 0. Step 4: Coating and UV curing of the hydrophilic functional surface layer (1) Preparation of surface coating solution: Bio-based PVP, pH-responsive monomer, and antibacterial modifier QCS-ZnO are added to deionized water, stirred and dissolved, and then photoinitiator Irgacure 1173 is added. The mixture is ultrasonically dispersed for 20-40 min to obtain a surface coating solution with a solid content of 15%-25%. (2) The surface coating liquid is applied to the surface of the intermediate dynamic cross-linking layer by spraying. The spraying pressure is 0.3~0.5MPa, the spraying distance is 15~25cm, and the wet film thickness of the coating is 8~12μm. (3) Place the coated substrate in a UV curing machine and irradiate it for 30-60 seconds under ultraviolet light with a wavelength of 365nm and a light intensity of 80~120mW / cm². After curing, vacuum dry it at 50~60℃ for 1~2 hours to obtain a medical-grade TPU elastomer with hydrophilic coating function.

6. The preparation method according to claim 5, characterized in that, In step 1 (3), the temperatures of each section of the twin-screw extruder are: feeding section 170~175℃, compression section 175~185℃, metering section 185~190℃, and die head 180~185℃; in step 4 (3), nitrogen gas is introduced for protection during UV curing, and the oxygen content is ≤0.5%.

7. The preparation method according to claim 5, characterized in that, The viscosity of the intermediate layer coating liquid is 20~50 mPa. The viscosity of the surface coating liquid is 30~80 mPa. During the coating process, the ambient humidity should be controlled at 40%~60%, and the temperature at 20~25℃.

8. An application of the medical-grade thermoplastic polyurethane elastomer according to any one of claims 1 to 4, characterized in that, The elastomer is used to manufacture interventional medical devices.

9. The application according to claim 8, characterized in that, The interventional medical devices include coronary catheters, neurovascular guidewires, balloon catheters, ureteral stents, central venous catheters, or endoscopic sheaths.

10. The application according to claim 9, characterized in that, The inner wall coating of the coronary catheter has a thickness of 3~4μm, and the outer wall coating has a thickness of 2~3μm.

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