Hydrophilic lubricating coating and preparation process

Abstract

The invention relates to the technical field of medical instrument coatings, and particularly provides a hydrophilic lubricating coating and a preparation process thereof, the hydrophilic lubricating coating comprises the following components by weight: 3%-10% of polyvinyl pyrrolidone, 5%-15% of composite bonding resin, 1%-5% of a cross-linking agent, 1%-5% of an initiator, 0.1%-1% of a leveling agent, 0.1%-0.5% of an antifoaming agent, 0.2%-2% of a nanometer reinforcing filler, and 60%-80% of a mixed solution; the preparation process comprises the following steps: preparing a presol, preparing a coating liquid, coating the coating liquid, carrying out thermocuring and carrying out UV photocuring. According to the invention, through collaborative design of the composite bonding resin and a gradient cross-linking system, strong adhesive force and lasting lubricity of the coating on a PVC substrate are realized; the mechanical strength and sterilization resistance of the coating are remarkably improved by introducing the nano reinforcing filler and the PVP with controllable molecular weight; according to the scheme, a dual-curing process is creatively used, and the forming quality of the hydrophilic lubricating coating is improved.

Description

Technical Field

[0001] This invention relates to the field of medical device coating technology, specifically to a hydrophilic lubricating coating and its preparation process. Background Technology

[0002] PVC is the most widely used material in the field of medical device consumables, mostly low-value consumables. Its low surface energy and the plasticizers that leach from the surface after long-term storage severely limit the application of hydrophilic coatings in PVC medical catheters. This is mainly manifested in the coating peeling off after high-temperature, high-humidity sterilization with ethylene oxide and during use, potentially leading to serious clinical consequences. Solutions to improve the adhesion of PVC catheters mainly include surface pretreatment: such as plasma treatment, flame treatment, and undercoating. However, these solutions significantly increase usage costs, and since PVC catheters are mostly low-value consumables, this limits their application.

[0003] A published Chinese patent, publication number CN108117830A, discloses a water-based hydrophilic lubricating coating, characterized by comprising the following components in parts by weight: 5-15 parts of acrylamide-modified vinylpyrrolidone polymer; 10-30 parts of waterborne polyurethane; 1-10 parts of waterborne crosslinking agent; 1-5 parts of leveling agent; and 40-83 parts of solvent. Although this scheme proposes a combination of acrylamide-modified PVP and waterborne polyurethane, it still suffers from defects such as low curing efficiency and insufficient sterilization resistance. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a hydrophilic lubricating coating and its preparation process. Through the synergistic effect of composite bonding resin and the synergistic regulation of the two-stage curing process, the coating achieves high adhesion, long-lasting lubricity and excellent sterilization resistance on PVC substrates. This solves the problems of low curing efficiency and insufficient sterilization resistance of existing hydrophilic lubricating coatings.

[0005] To achieve the above and other related objectives, the present invention provides a hydrophilic lubricating coating comprising the following components in weight percentage: 3%–10% polyvinylpyrrolidone, 5%–15% composite bonding resin, 1%–5% crosslinking agent, 1%–5% initiator, 0.1%–1% leveling agent, 0.1%–0.5% defoamer, 0.2%–2% nano-reinforcing filler, and 60%–80% mixed solution.

[0006] In one embodiment of the present invention, the composite adhesive resin is prepared by mixing polyether polyurethane and acrylate-modified polyurethane in a mass ratio of 1:0.8 to 1:1.5, wherein the polyether polyurethane anchors the PVC substrate through physical adsorption and hydrogen bonding, and the acrylate-modified polyurethane forms a three-dimensional network structure through photocuring.

[0007] In one embodiment of the present invention, the polyvinylpyrrolidone is one or more of K30, K60, and K90.

[0008] In one embodiment of the present invention, the crosslinking agent is a composite system of an acrylate monomer containing a double bond and an aziridine compound containing multiple functional groups, used to construct a gradient crosslinking network.

[0009] In one embodiment of the present invention, the initiator is one or more of 184, 2529, and benzophenone BP, and the initiator contains the photosensitizing agent TPO.

[0010] In one embodiment of the present invention, the leveling agent is one or more of acrylic surfactants, polyether polyester modified organosiloxanes, and cellulose acetate butyrate.

[0011] In one embodiment of the present invention, the nano-reinforced filler is modified nano-silica or nano-cellulose, and the surface of the nano-reinforced filler is treated with a silane coupling agent.

[0012] In one embodiment of the present invention, the mixed solution is a mixture of isopropanol, ethanol, ethyl acetate and tetrahydrofuran, and the ratio of isopropanol mixed with ethanol to ethyl acetate mixed with tetrahydrofuran is 1:0.5 to 1:1.5.

[0013] This invention provides a process for preparing a hydrophilic lubricating coating, comprising the following steps: a) Polyvinylpyrrolidone is pre-dissolved in a solvent made of one or a mixture of isopropanol and ethanol to form a presol; b) Add composite bonding resin, crosslinking agent, initiator, leveling agent, defoamer and nano-reinforcing filler to the pre-solid in sequence, and add a mixed solution made of isopropanol, ethanol, ethyl acetate and tetrahydrofuran. After high-speed dispersion, a uniform coating liquid is formed. c) Apply the coating liquid to the surface of the PVC conduit using a micro-gravure coating method to form a coating; d) Perform the first stage of heat curing on the coated conduit, with a heat curing temperature of 60-80℃ and a heat curing time of 5-15 minutes; e) The thermocured coated conduit is subjected to a second stage of UV curing in a nitrogen atmosphere, with an irradiation energy of 500–1000 mJ / cm².

[0014] In one embodiment of the present invention, the thermosetting and UV curing are carried out continuously online, and an infrared preheating zone is provided between the two stages.

[0015] As described above, the hydrophilic lubricating coating and preparation process of the present invention have the following beneficial effects: This invention achieves strong adhesion and long-lasting lubricity of the coating on PVC substrates through the synergistic design of composite bonding resin and gradient crosslinking system; by introducing nano-reinforcing fillers and molecular weight controllable PVP, the mechanical strength and sterilization resistance of the coating are significantly improved; this solution uses microgravure coating and combines the advantages of thermosetting and UV curing, pioneering the use of dual curing, which greatly reduces costs while retaining the advantages of each, and can be applied to large-scale, high-volume applications; the UV curing under nitrogen protection effectively inhibits oxygen inhibition polymerization, improving curing efficiency and coating surface quality. Detailed Implementation

[0016] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0017] Example 1: This invention provides a hydrophilic lubricating coating comprising the following components by weight percentage: 3%–10% polyvinylpyrrolidone, 5%–15% composite bonding resin, 1%–5% crosslinking agent, 1%–5% initiator, 0.1%–1% leveling agent, 0.1%–0.5% defoamer, 0.2%–2% nano-reinforcing filler, and 60%–80% mixed solution; the composite bonding resin is prepared by mixing polyether-type polyurethane and acrylate-modified polyurethane in a mass ratio of 1:0.8–1:1.5, wherein the polyether-type polyurethane anchors the PVC substrate through physical adsorption and hydrogen bonding, and the acrylate-modified polyurethane forms a three-dimensional network structure through photocuring; the polyvinylpyrrolidone is one or more of K30, K60, and K90. The preparation method of polyvinylpyrrolidone (PVP) involves pre-dissolving PVP in a solvent, which is one or a mixture of isopropanol and ethanol. The crosslinking agent is a composite system of acrylate monomers containing double bonds and aziridine compounds containing polyfunctional groups, used to construct a gradient crosslinking network. The initiator is one or more of 184, 2529, and benzophenone (BP), and the initiator includes the photosensitizing agent TPO. The leveling agent is one or more of acrylic surfactants, polyether polyester-modified organosiloxanes, and cellulose acetate butyrate. The nano-reinforcing filler is modified nano-silica or nano-cellulose, and the surface of the nano-reinforcing filler is treated with a silane coupling agent. The mixed solution is a mixture of isopropanol, ethanol, ethyl acetate, and tetrahydrofuran, and the ratio of isopropanol mixed with ethanol to ethyl acetate mixed with tetrahydrofuran is 1:0.5 to 1:1.5.

[0018] The hydrophilic lubricating coating component of this invention provides durable hydrophilic lubricity through polyvinylpyrrolidone and innovatively employs a composite adhesive resin system composed of polyether-type polyurethane and acrylate-modified polyurethane, which works synergistically on the PVC substrate. The former achieves strong anchoring through physical adsorption and entanglement, while the latter constructs a three-dimensional network through photocuring. This system, combined with a specific crosslinking agent and nano-reinforcing filler, forms a stable coating with a gradient crosslinking structure. Thus, without the need for undercoating, it achieves ultra-high adhesion of the coating to the PVC substrate (5B grade), an extremely low coefficient of dynamic friction (below 0.05), and excellent resistance to ethylene oxide sterilization, while ensuring good coating uniformity and mechanical durability.

[0019] Example 2: This example provides a process for preparing the hydrophilic lubricating coating, comprising the following steps: a) Polyvinylpyrrolidone is pre-dissolved in a solvent made of one or a mixture of isopropanol and ethanol to form a presol; b) Add composite bonding resin, crosslinking agent, initiator, leveling agent, defoamer and nano-reinforcing filler to the pre-solid in sequence, and add a mixed solution made of isopropanol, ethanol, ethyl acetate and tetrahydrofuran. After high-speed dispersion, a uniform coating liquid is formed. c) Apply the coating liquid to the surface of the PVC conduit using a micro-gravure coating method to form a coating; d) Perform the first stage of heat curing on the coated conduit, with a heat curing temperature of 60-80℃ and a heat curing time of 5-15 minutes; e) The thermocured coated conduit is subjected to a second stage of UV curing in a nitrogen atmosphere, with an irradiation energy of 500–1000 mJ / cm².

[0020] In steps d) and e), the thermocuring and UV curing are carried out continuously online, and an infrared preheating zone is provided between the two stages.

[0021] The hydrophilic lubricating coating preparation process of this invention adopts an innovative two-stage continuous curing process of first thermal curing and then UV curing. It combines the advantages of thermal curing in removing solvents and achieving preliminary leveling and pre-crosslinking of the coating, with the advantages of UV curing in rapidly building a high-strength three-dimensional network structure. Thus, it can achieve efficient and deep curing without nitrogen protection. This process significantly improves production efficiency, enabling large-scale continuous production of 100,000 pieces per day by 10 people. At the same time, it ensures a strong bond between the coating and the PVC substrate, and has excellent lubrication durability and sterilization resistance, perfectly balancing the industrial demand for high performance and low cost.

[0022] Example 3, based on Examples 1 and 2, describes the preparation of a low-cost, high-efficiency curable hydrophilic lubricating coating, comprising the following components by weight percentage: Hydrophilic polymer: Polyvinylpyrrolidone (PVPK90, BASF) 4%; Composite bonding resin: 4% acrylate-modified polyurethane (U-25-20D, DSM); Crosslinking agent: 1% polyethylene glycol diacrylate (PEGDA600, Changxing Technology); Initiator: Omnirad 2959 (IGMResins) 2%; Leveling agent (BYK-333) 0.5%; Defoamer (BYK-3155) 0.5%; Mixed solution: isopropanol 43%, ethyl acetate 45%; The preparation process includes the following steps: a) Pre-dissolution: At room temperature, slowly add 4 parts by weight of PVPK90 to a mixed solution consisting of 43 parts by weight of isopropanol and 20 parts by weight of ethyl acetate, and continue mechanical stirring at 400 rpm for about 50 minutes until completely dissolved to form a transparent, viscous PVP pre-solution gel.

[0023] b) Preparing the coating solution: To the above PVP pre-solvent, add 4 parts by weight of acrylate-modified polyurethane U-25-20D, 1 part by weight of PEGDA600 crosslinking agent, 0.5 parts by weight of leveling agent BYK-333, and 0.5 parts by weight of defoamer BYK-3155 in sequence. Increase the stirring speed to 800 rpm and continue to disperse for 30 minutes to ensure that all components are mixed evenly.

[0024] Add initiator: Reduce the stirring speed to 300 rpm, add the remaining 25 parts by weight of ethyl acetate to adjust the viscosity of the system, and finally add 2 parts by weight of photoinitiator Omnirad2959. Stir at low speed for 15 minutes to avoid introducing too many air bubbles, and obtain a clear and uniform hydrophilic lubricating coating liquid.

[0025] c) Coating: Using the dip-coating method, the PVC conduit is immersed in the coating liquid at a constant speed of 100 mm / min, and then pulled up at a uniform speed of 200 mm / min to make the coating liquid evenly cover the surface of the conduit, forming a coating with a wet film thickness of about 8-10 μm.

[0026] d) Heat curing: Transfer the coated conduit to a 75°C forced-air oven and allow it to heat-cur for 8 minutes to remove most of the solvent and achieve initial shaping of the coating.

[0027] e) UV curing: Subsequently, the conduit is immediately moved into the UV curing machine, and UV-LED light source with a main wavelength of 365nm is used in an air atmosphere to cure the light with a cumulative irradiation energy of 800mJ / cm² to form the final cross-linked coating network.

[0028] This embodiment uses a single acrylate-modified polyurethane as the bonding resin and employs the common and low-cost solvent system of isopropanol / ethyl acetate, significantly reducing raw material costs while ensuring performance. Furthermore, this formulation is water-free, avoiding the potential impact of moisture on the PVC substrate, and the rapid solvent evaporation rate helps improve production line speed. This embodiment selects Omnirad 2959, which has excellent photoactivity, enabling efficient curing even in air without the need for expensive nitrogen protection equipment, further reducing equipment investment and operating costs.

[0029] Tests showed that the coating prepared in this embodiment achieved a 4B adhesion rating on PVC catheters, with a dynamic friction coefficient of <0.08, good lubricity, and the ability to withstand conventional ethylene oxide sterilization processes, fully meeting the usage requirements of most low-value PVC medical devices.

[0030] Example 4: This example provides a highly biocompatible and smooth-surfaced hydrophilic lubricating coating. This embodiment aims to provide a solution that places particular emphasis on biosafety, coating surface quality, and curing uniformity, comprising the following components by weight percentage: Hydrophilic polymer: Polyvinylpyrrolidone (PVPK30, BASF) 5%; Composite bonding resin: 3% acrylate-modified polyurethane (U-25-20D, DSM); Crosslinking agent: Acryloylmorpholine (ACMO, Kejuxi) 1%; Initiator: 2% benzophenone (BP); Leveling agent (BYK-UV3500) 0.8%; Defoamer (Tego-920) 0.2%; Mixed solution: 48% ethanol, 40% ethyl acetate.

[0031] The preparation process includes the following steps: a) Pre-dissolution: At room temperature, slowly add 5 parts by weight of PVPK30 to a mixed solution consisting of 48 parts by weight of ethanol and 20 parts by weight of ethyl acetate, and mechanically stir at 500 rpm for 60 minutes until a completely transparent homogeneous solution is formed.

[0032] b) Preparing the coating solution: While stirring, add 3 parts by weight of acrylate-modified polyurethane U-25-20D, 1 part by weight of ACMO crosslinking agent, 0.8 parts by weight of leveling agent BYK-UV3500, and 0.2 parts by weight of defoamer Tego-920 to the solution in sequence. Increase the stirring speed to 900 rpm and disperse at high speed for 40 minutes to ensure that the additives are fully dispersed and the resin is completely dissolved.

[0033] Add initiator: Reduce the stirring speed to 400 rpm, add the remaining 20 parts by weight of ethyl acetate, and finally add 2 parts by weight of benzophenone; continue stirring at low speed for 20 minutes until the benzophenone is completely dissolved, to obtain a coating liquid with moderate viscosity and clear appearance.

[0034] c) Coating: Using a precision spraying process, the coating liquid is evenly sprayed onto the surface of the PVC conduit under controlled spray gun pressure and moving speed, forming a thin layer with a wet film thickness of approximately 6-8 μm. This method is beneficial for obtaining extremely high surface smoothness.

[0035] d) Thermal curing: Place the sprayed workpiece in an oven at 65°C and cure for 12 minutes to allow the solvent to evaporate slowly and evenly, creating a good base for UV curing.

[0036] e) UV curing: The workpiece is transferred to a UV curing device equipped with a medium-pressure mercury lamp. Due to the absorption wavelength characteristics of the initiator benzophenone, this type of broadband light source is required. Curing is carried out in an air atmosphere with an irradiation energy of 1200 mJ / cm².

[0037] The ACMO monomer used in this embodiment is characterized by low irritation, low toxicity, and high reactivity. Its homopolymer exhibits good hydrophilicity and biocompatibility. Combined with PVPK30, it further ensures good compatibility between the coating and the human body, meeting more stringent biosafety testing requirements. The leveling agent BYK-UV3500 is a highly efficient UV-curing leveling agent that significantly improves the leveling and substrate wettability of the coating, eliminating defects such as orange peel and pinholes. Combined with Tego-920 defoamer, it ensures that bubbles are not easily generated during the spraying process, ultimately resulting in an extremely smooth and flat coating surface. This embodiment uses ethanol and ethyl acetate as solvents throughout, simplifying the system. Ethanol is also a more environmentally friendly and low-toxicity solvent, beneficial for occupational health and subsequent environmental treatment. While ensuring excellent biocompatibility and surface quality, this embodiment also maintains good 4B-level adhesion and a friction coefficient <0.07 lubricity, and exhibits good resistance to ethylene oxide sterilization.

[0038] Example 5: This example provides a hydrophilic lubricating coating with a high adhesion and toughness balance, comprising the following components by weight percentage: Hydrophilic polymer: Polyvinylpyrrolidone (PVPK60, BASF) 5%; Composite bonding resin: 2% single-component polyether polyurethane, 3% acrylate-modified polyurethane (U-25-20D, DSM); Crosslinking agent: Acryloylmorpholine (ACMO, Kejuxi) 1%; Initiator: 2% benzophenone (BP); Leveling agent (BYK-UV3500) 0.8%; Defoamer (Tego-920) 0.2%; Mixed solution: 48% ethanol, 40% ethyl acetate.

[0039] The preparation process includes the following steps: a) Resin premixing: 2 parts by weight of single-component polyether polyurethane 533 and 3 parts by weight of acrylate-modified polyurethane U-25-20D were pre-dissolved in a total of 30 parts by weight of a solvent composed of ethanol and ethyl acetate in a specific ratio. The solution was stirred at 600 rpm for 30 minutes in a 40°C water bath to form a homogeneous resin solution. Hydrophilic phase preparation: In another container, 5 parts by weight of PVPK60 were dissolved in the remaining 38 parts by weight of ethanol and stirred at room temperature until completely transparent.

[0040] b) Mixing and blending: Under low stirring speed of 300 rpm, slowly add the hydrophilic PVP solution to the resin solution to avoid gel formation; then add 1 part by weight of ACMO, 0.8 parts by weight of leveling agent BYK-UV3500 and 0.2 parts by weight of defoamer Tego-920 in sequence; increase the speed to 800 rpm and disperse for 30 minutes.

[0041] Add initiator: Finally, add 2 parts by weight of benzophenone and the remaining 10 parts by weight of ethyl acetate to adjust the final viscosity and solid content, and stir at a low speed of 400 rpm for 20 minutes to obtain a uniform and stable coating liquid.

[0042] c) Coating: The coating liquid is applied to the PVC conduit using the dip-coating method at a speed of 150 mm / min, with a wet film thickness of approximately 10 μm.

[0043] d) Heat curing: Then perform heat curing at 65℃ for 10 minutes; e) UV curing: Then UV curing is performed under a medium-pressure mercury lamp at 1000mJ / cm².

[0044] In this embodiment, the polyether-type polyurethane 533, through its long-chain structure, hydrogen bonds, and van der Waals forces, forms a strong physical adsorption and entanglement with the PVC substrate surface, including the precipitated plasticizer, constituting a robust underlying anchor. The acrylate-modified polyurethane, during UV curing, undergoes a copolymerization reaction with ACMO, PVP, etc., forming a dense three-dimensional network structure, constituting a hard surface armor. This structure of a "flexible underlayer" and a "rigid surface layer" achieves a perfect balance between adhesion and cohesion, effectively inhibiting peeling caused by stress concentration. After ethylene oxide sterilization or immersion in simulated body fluids, the adhesion retention rate of this coating far exceeds that of single-resin systems. In repeated bending tests on the conduit, the coating did not wrinkle or crack, exhibiting excellent flexibility and durability. While maintaining excellent adhesion and good lubricity, the moderate molecular weight of PVPK60 results in ideal drying speed and curing efficiency for the coating.

[0045] Example 6: This example describes the preparation of a general-purpose, highly lubricating hydrophilic coating, comprising the following components by weight percentage: Polyvinylpyrrolidone (PVPK90) 8%; The composite adhesive resin comprises 12%, wherein the ratio of polyether-type polyurethane to acrylate-modified polyurethane is 1:1. Crosslinking agent: 3%, of which PEGDA400:aziridine crosslinking agent XL-100 = 2:1; Initiator: 2%, of which photoinitiator 184: photosensitizer TPO = 3:1; Leveling agent: 0.4% polyether polyester modified organosiloxane; Defoamer: 0.2% Nano-reinforced filler: 1% nano-silica modified with silane coupling agent; Mixed solution: 73.4%, wherein isopropanol:ethanol:ethyl acetate:tetrahydrofuran = 3:2:3:2; The preparation process includes the following steps: a) Pre-dissolution: Slowly add PVPK90 to a mixed solution of isopropanol and ethanol while stirring, and continue stirring in a 40°C water bath for 60 minutes until completely dissolved to form a transparent pre-solution gel.

[0046] b) Preparing the coating solution: Add the composite bonding resin, PEGDA400, leveling agent, defoamer, and nano silica to the pre-solidified adhesive in sequence, and disperse at high speed at 800 rpm for 30 minutes. Then add aziridine crosslinking agent XL-100, photoinitiator 184, and TPO, and stir at low speed at 500 rpm for 15 minutes to avoid introducing too many air bubbles, so as to obtain a uniform coating solution.

[0047] c) Coating: A micro-gravure coating machine is used to precisely coat the coating liquid onto the surface of the PVC conduit, controlling the wet film thickness to 12μm.

[0048] d) Heat curing: The coated conduit is dried in a hot air circulation tunnel at 70°C for 10 minutes.

[0049] e) UV curing: Subsequently, the conduit immediately enters the UV curing equipment and is cured under a nitrogen protective atmosphere (oxygen concentration <100ppm) with an irradiation energy of 800mJ / cm².

[0050] The coating prepared in this embodiment has an extremely low coefficient of friction of <0.03, excellent lubricity, and an adhesion rating of 5B (ASTM D3359). Furthermore, it does not peel off or degrade in performance after ethylene oxide sterilization, making it suitable for interventional catheters with extremely high lubricity requirements.

[0051] Example 7: This example provides a high-adhesion and abrasion-resistant hydrophilic lubricating coating, comprising the following components by weight percentage: Polyvinylpyrrolidone: PVPK60 5%; Composite bonding resin: 14%, wherein polyether polyurethane: acrylate modified polyurethane = 1:1.2; Crosslinking agent: 4%, of which trimethylolpropane triacrylate (TMPTA):ACMO = 1:1; Initiator: 2.5%, photoinitiator BP: photoinitiator 2529 = 1:1; Leveling agent: 0.3% cellulose acetate butyrate; Non-silicone defoamer: 0.15%; Nano-reinforced filler: 1.5% nano-cellulose whiskers; Mixed solution: 72.55%, wherein isopropanol:ethanol:ethyl acetate:tetrahydrofuran = 4:3:2:1.

[0052] The preparation process includes the following steps: a) Pre-dissolution: Dissolve PVPK60 in a mixed solution of isopropanol and ethanol and stir for 45 minutes at room temperature.

[0053] b) Preparing the coating solution: Add the composite bonding resin, TMPTA, leveling agent, defoamer, and nanocellulose whiskers, and disperse at high speed at 1000 rpm for 40 minutes. Then add ACMO and two photoinitiators, and mix thoroughly by low-speed stirring.

[0054] c) Coating: The dip-coating method is used, and the lifting speed is controlled at 5 mm / s to obtain a wet film thickness of about 10 μm.

[0055] d) Heat curing: First, cure at 65°C for 8 minutes.

[0056] Infrared preheating: The coating is rapidly preheated to 50°C using a short-wave infrared device to promote coating leveling.

[0057] e) UV curing: Curing is performed in a nitrogen atmosphere with an irradiation energy of 1000 mJ / cm².

[0058] This embodiment significantly enhances the crosslinking density and mechanical strength of the coating by increasing the proportion of the bonding resin and using TMPTA and nanocellulose. The coating showed no significant wear after 1000 cycles of rubbing tests, maintaining an adhesion of 5B, making it particularly suitable for instruments requiring frequent repositioning or subject to friction.

[0059] Example 8: This example provides a fast-curing and economical hydrophilic lubricating coating, comprising the following components by weight percentage: Polyvinylpyrrolidone (PVPK30) 4%; Composite bonding resin: 8%, of which polyether polyurethane: acrylate-modified polyurethane = 1:0.8; Crosslinking agent: DMAA 2%; Initiator: Photoinitiator 184 3%; Leveling agent: 0.6% acrylate; Organosilicon defoamer: 0.25%; Nano-reinforced filler: 0.5% modified nano-silica; Mixed solution: 81.65%, wherein isopropanol:ethanol:ethyl acetate:tetrahydrofuran = 5:4:0.5:0.5.

[0060] The preparation process includes the following steps: a) Pre-dissolution: Dissolve PVPK30 in a mixed solution of isopropanol and ethanol at room temperature and stir for 30 minutes.

[0061] b) Prepare the coating solution: Add all remaining components and disperse at 700 rpm for 25 minutes to form the coating solution.

[0062] c) Coating: A spray coating process is used, and the wet film thickness of the coating is approximately 8 μm.

[0063] d) Heat curing: The time is shortened to 5 minutes by passing through an 80°C drying tunnel.

[0064] e) UV curing: No nitrogen protection required; rapid curing in air at an energy of 600 mJ / cm².

[0065] This embodiment, by selecting low molecular weight PVP, a highly photoactive initiator, and a simplified solvent system, significantly improves the curing speed and reduces production energy consumption and protective gas costs while ensuring the basic performance of adhesion 4B and friction coefficient <0.06. It is very suitable for large-scale, low-cost production of PVC conduits.

[0066] Comparative Example 1, this embodiment omits the preparation of the hydrophilic lubricating coating with nano-reinforced filler and composite bonding resin, and includes the following components by weight percentage: Polyvinylpyrrolidone: PVPK90, BASF 8%; Single bonding resin: Acrylic modified polyurethane (U-25-20D, DSM): 12%; Crosslinking agent (PEGDA600, Changxing Technology): 3%; Initiator (Omnirad 2959): 2%; Leveling agent (BYK-333): 0.4%; Defoamer (BYK-3155): 0.2%; Mixed solution (isopropanol:ethyl acetate = 1:1): 74.4%; The preparation process includes the following steps: consistent with Example 3, including UV curing in a nitrogen environment.

[0067] Performance comparison and results analysis: Abrasion resistance test: After 500 cycles of reciprocating friction, the coating surface of Comparative Example 1 showed obvious wear marks, and the coefficient of friction increased by more than 50%. However, the coatings of Examples 3 and 4 remained intact after 1000 cycles of friction.

[0068] Adhesion test: The initial adhesion was 3B, which dropped to 1B after ethylene oxide sterilization, and the coating edge began to peel up.

[0069] Analysis of the causes: A single resin system lacks the physical anchoring ability of polyether polyurethane to the PVC substrate. Furthermore, without the reinforcing effect of nanofillers, the cross-linked network of the coating is more easily damaged under mechanical and thermal stress. This demonstrates that composite bonding resin and nano-reinforcing fillers have a synergistic reinforcing effect in constructing a robust and durable coating network; neither can be dispensed with.

[0070] Comparative Example 2, this embodiment modifies the curing sequence and curing atmosphere to prepare a hydrophilic lubricating coating, comprising the following components by weight percentage: Hydrophilic polymer: Polyvinylpyrrolidone (PVPK90, BASF) 4%; Composite bonding resin: 4% acrylate-modified polyurethane (U-25-20D, DSM); Crosslinking agent: 1% polyethylene glycol diacrylate (PEGDA600, Changxing Technology); Initiator: Omnirad 2959 (IGMResins) 2%; Leveling agent (BYK-333) 0.5%; Defoamer (BYK-3155) 0.5%; Mixed solution: isopropanol 43%, ethyl acetate 45%; The coating steps in the preparation process are the same as in Example 3.

[0071] First, UV curing: The wet coating is first UV cured in an air atmosphere with an irradiation energy of 800 mJ / cm².

[0072] Post-heat curing: Subsequently, the conduit is placed in an oven at 70°C and heated for 10 minutes.

[0073] Performance comparison and results analysis: Coating appearance: The coating surface is severely sticky and cannot reach a fully dry state, and there are visible micro-bubbles and leveling defects.

[0074] Chemical properties: FTIR analysis revealed that the conversion rate of C=C double bonds in the coating was significantly lower than that in Example 1.

[0075] Mechanical properties: The coating has low hardness and extremely poor wear resistance; it can be damaged by light scratching.

[0076] Cause Analysis: During initial UV curing, the coating surface rapidly cross-links in the air, forming a dense layer, while the solvent is encapsulated within. Subsequent thermal curing, although able to expel the solvent, leads to bubble formation and fails to promote further reaction of the encapsulated active groups. More importantly, the quenching effect of oxygen in the air on surface free radicals (oxygen inhibition) results in incomplete surface curing, leading to a sticky texture. This demonstrates that the specific process path of "initial thermal curing to remove solvent and achieve preliminary cross-linking, followed by deep UV curing in an inert atmosphere" is key to achieving high cross-linking density and excellent appearance in the coating; its technical effects are not easily predicted by those skilled in the art.

[0077] Comparative Example 3: This embodiment uses a hydrophilic lubricating coating based on a single acrylate-modified polyurethane resin system, comprising the following components by weight percentage: Polyvinylpyrrolidone (PVPK60, BASF): 5%; Acrylic-modified polyurethane (U-25-20D, DSM): 5%; Crosslinking agent (ACMO, Kejuxi): 1%; Initiator (benzophenone BP): 2%; Leveling agent (BYK-UV3500): 0.8%; Defoamer (Tego-920): 0.2%; Mixed solution: 48% ethanol, 40% ethyl acetate.

[0078] Preparation process: exactly the same as in Example 7.

[0079] Performance comparison and results analysis: Adhesion test: After coating and curing, the initial adhesion was only 2B grade; after ethylene oxide (EO) sterilization, the adhesion further decreased to 0B grade, and the coating peeled off over a large area.

[0080] Analysis of the cause: Single acrylate-modified polyurethane mainly relies on chemical bonds formed by photocuring and limited polarity to adhere to the PVC surface, lacking the strong physical anchoring and penetration provided by polyether-type polyurethane. Under the high temperature and humidity environment of EO sterilization, the PVC substrate swells slightly, and the cohesive energy changes, leading to the destruction of this relatively fragile interfacial bond. This, in turn, proves the necessity and superiority of the synergistic effect of the composite adhesive resin in this invention.

[0081] In summary, this invention achieves strong adhesion and long-lasting lubricity of the coating on PVC substrates through the synergistic design of composite bonding resin and gradient crosslinking system. By introducing nano-reinforcing fillers and molecular weight-controllable PVP, the mechanical strength and sterilization resistance of the coating are significantly improved. This solution utilizes microgravure coating combined with the advantages of thermosetting and UV curing, innovatively employing dual curing, which greatly reduces costs while retaining the advantages of each, making it suitable for large-scale, high-volume applications. Furthermore, the UV curing under nitrogen protection effectively inhibits oxygen-induced polymerization, improving curing efficiency and coating surface quality. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and possesses high industrial applicability.

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A hydrophilic lubricating coating, characterized in that, It comprises the following components by weight percentage: 3%–10% polyvinylpyrrolidone, 5%–15% composite adhesive resin, 1%–5% crosslinking agent, 1%–5% initiator, 0.1%–1% leveling agent, 0.1%–0.5% defoamer, 0.2%–2% nano-reinforcing filler, and 60%–80% mixed solution.

2. The hydrophilic lubricating coating according to claim 1, characterized in that: The composite bonding resin is made by mixing polyether polyurethane and acrylate-modified polyurethane in a mass ratio of 1:0.8 to 1:1.

5. The polyether polyurethane anchors the PVC substrate through physical adsorption and hydrogen bonding, while the acrylate-modified polyurethane forms a three-dimensional network structure through photocuring.

3. The hydrophilic lubricating coating according to claim 1, characterized in that: The polyvinylpyrrolidone is one or more of K30, K60, and K90.

4. The hydrophilic lubricating coating according to claim 1, characterized in that: The crosslinking agent is a composite system of acrylate monomers containing double bonds and aziridine compounds containing polyfunctional groups, used to construct a gradient crosslinking network.

5. The hydrophilic lubricating coating according to claim 1, characterized in that: The initiator is one or more of 184, 2529, and benzophenone BP, and the initiator contains the photosensitizing agent TPO.

6. The hydrophilic lubricating coating according to claim 1, characterized in that: The leveling agent is one or more of the following: acrylic surfactants, polyether polyester modified organosiloxanes, and cellulose acetate butyrate.

7. The hydrophilic lubricating coating according to claim 1, characterized in that: The nano-reinforced filler is modified nano-silica or nano-cellulose, and the surface of the nano-reinforced filler is treated with a silane coupling agent.

8. The hydrophilic lubricating coating according to claim 1, characterized in that: The mixed solution is a mixture of isopropanol, ethanol, ethyl acetate and tetrahydrofuran, and the ratio of isopropanol mixed with ethanol to ethyl acetate mixed with tetrahydrofuran is 1:0.5 to 1:1.

5.

9. A process for preparing a hydrophilic lubricating coating according to any one of claims 1-8, characterized in that, Includes the following steps: a) Polyvinylpyrrolidone is pre-dissolved in a solvent made of one or a mixture of isopropanol and ethanol to form a presol; b) Add composite bonding resin, crosslinking agent, initiator, leveling agent, defoamer and nano-reinforcing filler to the pre-solid in sequence, and add a mixed solution made of isopropanol, ethanol, ethyl acetate and tetrahydrofuran. After high-speed dispersion, a uniform coating liquid is formed. c) Apply the coating liquid to the surface of the PVC conduit using a micro-gravure coating method to form a coating; d) Perform the first stage of heat curing on the coated conduit, with a heat curing temperature of 60-80℃ and a heat curing time of 5-15 minutes; e) The thermocured coated conduit is subjected to a second stage of UV curing in a nitrogen atmosphere, with an irradiation energy of 500–1000 mJ / cm².

10. The hydrophilic lubricating coating preparation process according to claim 9, characterized in that: The thermosetting and UV curing are carried out continuously online, and an infrared preheating zone is provided between the two stages.