A surface treatment method for medical PCL materials based on electron beam irradiation enhanced coating

Abstract

A surface treatment method for medical PCL materials based on electron beam irradiation-enhanced coating bonding includes the following steps: S1: Cleaning and drying medical devices or components made from medical-grade PCL raw materials that meet pharmacopoeia standards, are free of cytotoxicity and heavy metal residues, through melt deposition modeling or injection molding and extrusion molding, to remove surface grease and dust; S2: Placing the pretreated PCL workpiece in a water curtain spray booth for painting; S3: Drying the painted workpiece in a clean oven at 40-50℃ for 60-90 minutes to form a uniform and smooth surface; S4: Sending the dried coated workpiece into an electron beam irradiation device for irradiation treatment; S5: Equipping the irradiated workpiece at room temperature, followed by coating performance testing. This invention can effectively isolate PCL materials from the biological environment, improve their surface smoothness and aesthetics, and ensure long-term stable bonding of the coating during the material's degradation cycle.

Description

Technical Field

[0001] This invention belongs to the field of biomedical material surface modification technology, and specifically relates to a surface treatment method for medical PCL materials based on electron beam irradiation enhanced coating. Background Technology

[0002] Polycaprolactone (PCL), as a biocompatible and biodegradable synthetic polymer, has broad application prospects in tissue engineering scaffolds, drug delivery systems, absorbable sutures, and orthopedic internal fixation devices. However, PCL faces the following technical bottlenecks in practical applications: Surface hydrophobicity and bioinertness: The relatively hydrophobic surface of PCL may affect its initial interaction with surrounding tissues; at the same time, its original surface may come into direct contact with body fluids or tissues, causing unnecessary inflammatory reactions or adhesions.

[0003] Insufficient surface smoothness and aesthetics: PCL devices that are directly molded or 3D printed often have microscopic roughness or texture on their surface, which affects their visual appeal and the feel of use in some applications (such as wearable medical devices).

[0004] Coating adhesion challenge: To improve the above problems, functional coatings (such as hydrophilic coatings, antibacterial coatings, and color marking coatings) are often introduced onto the PCL surface using methods such as spraying and dip coating. However, PCL has a low surface energy and is a thermoplastic material. Traditional thermosetting or UV-curing coatings have weak physical / chemical adhesion to the substrate. In the complex mechanical and biochemical environment inside the substrate, coating peeling, blistering, or detachment can easily occur, leading to functional failure or the generation of microparticles.

[0005] While existing technologies employ plasma treatment and chemical grafting to enhance the surface energy of PCL, these methods are expensive, result in uneven processing, or involve complex processes. Although electron beam irradiation has been used for crosslinking polymer materials, research on its systematic application to enhance the adhesion of sprayed coatings on PCL surfaces, especially in combination with environmentally friendly and efficient water curtain spraying technology, is limited. For example, Xu Zezhou et al. raised a similar issue in 2022: the interfacial adhesion of PCL coatings remains a key factor affecting its development and application, and proposed using nanosecond laser pretreatment technology to address this problem (DOI: 10.1016 / j.matlet.2022.132774). However, this technology is costly and suitable only for microstructure control, making it difficult to achieve high-efficiency, low-cost large-scale industrial production. In contrast, electron beam irradiation is less expensive and can achieve surface chemical functionalization (such as hydrophilic or antibacterial grafting). Simultaneous irradiation processing and sterilization of the product allows for high-efficiency and large-scale production. Summary of the Invention

[0006] In order to overcome the above technical problems, the purpose of this invention is to provide a surface treatment method for medical PCL materials based on electron beam irradiation-enhanced coating. This method can effectively isolate PCL materials from the biological environment, improve their surface smoothness and aesthetics, and ensure long-term stable bonding of the coating during the material degradation cycle.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A surface treatment method for medical PCL materials based on electron beam irradiation enhanced coating includes the following steps; S1: Substrate pretreatment: Medical devices or components made from medical-grade PCL raw materials that meet pharmacopoeia standards, are free of cytotoxicity and heavy metal residues, are cleaned and dried to remove surface grease and dust, and PCL workpieces are obtained. S2: Water curtain spray painting: The pre-treated PCL workpiece is placed in a water curtain spray painting booth and sprayed with paint. S3: Pre-curing and drying: Dry the painted workpiece in a clean oven at 40-50℃ for 60-90 minutes to allow the paint film to initially level out and evaporate most of the solvent / water, forming a uniform and smooth coated workpiece; subsequent electron beam irradiation treatment can also play a certain role in drying. S4: Electron beam irradiation treatment: The dried coated workpiece is sent into an electron accelerator for irradiation treatment.

[0008] S5: Post-treatment and inspection: The irradiated workpiece is equilibrated at room temperature for 24 hours, and then the coating performance is tested.

[0009] In step S2, the paint is a special medical-grade coating with good biocompatibility with PCL, preferably water-based polyurethane, medical acrylic resin or biodegradable polyester-based paint, and non-toxic pigments or functional factors (such as antibacterial agents) can be added as needed.

[0010] The air pressure of the spray gun is controlled at 0.3-0.7 MPa, and the distance between the spray gun and the workpiece is 5-20 cm. Through multiple thin-layer sprayings, the dry film thickness is controlled at 15-45 μm.

[0011] The effect of setting these parameters is that the painted surface is uniform, which can effectively increase the aesthetics of PCL material and reduce direct contact between PCL and the human body during deformation.

[0012] The water curtain system effectively captures paint mist, ensuring a clean and environmentally friendly working environment.

[0013] In step S4, during the irradiation treatment, the electron beam energy is 5-10.0 MeV, and the irradiation dose is 15-50 kGy. This increases the adhesion between the coating and the PCL, i.e., increases the bonding strength. The workpiece surface is scanned uniformly to ensure uniform dose distribution.

[0014] The electron accelerator generates a controllable deflection magnetic field by scanning magnets. Combined with nonlinear quasi-triangular wave current drive and conveyor belt speed matching, it broadens the Gaussian distributed thin beam of electrons into a uniform electron "curtain", thereby achieving uniform irradiation of the material surface.

[0015] The function of uniform irradiation is inherent in electron accelerators. The core principle of electron accelerator scanning is to expand a concentrated electron beam into a large-area uniform irradiation field through a combination of electromagnetic deflection and mechanical motion. This process is divided into two parts: transverse scanning and longitudinal scanning. I. Principle of Lateral Scanning The core component is the alternating scanning magnetic field inside the scanning box. After the accelerated electron beam enters the scanning box, it is deflected by the periodically changing transverse magnetic field and oscillates back and forth in the direction perpendicular to the electron's movement.

[0016] The scanning coil is driven by a quasi-triangular wave current that has been nonlinearly corrected to compensate for the geometric velocity difference when the electron beam deflects, avoid electron accumulation at both ends of the scan, and ensure that the linear density of the electron beam remains consistent throughout the entire transverse scanning range, ultimately expanding into a uniform electron beam band of a certain width.

[0017] II. Vertical Scanning Principle Longitudinal scanning is not achieved by magnetic field deflection, but by uniform mechanical transport of the irradiated workpiece, allowing the workpiece to move continuously in a direction perpendicular to the transverse scanning direction.

[0018] The transmission speed and transverse scanning frequency are strictly synchronized, allowing the transverse scanning trajectory of the electron beam to be continuously superimposed in the direction of workpiece movement. This splices the one-dimensional electron beam strip into a two-dimensional uniform irradiation surface, avoiding dose unevenness caused by scanning stripes. This achieves uniform irradiation of the material surface.

[0019] The high-energy electrons irradiated by the electron beam of this invention penetrate the coating film and act on the interface between the coating film and the PCL substrate and within both, producing the following synergistic effect: 1) Interfacial chemical bonding: High-energy electrons cause chain breaks in the polymer molecules of the coating film and the molecules on the PCL surface, generating a large number of free radicals. These free radicals recombine in the interfacial region to form covalent bonds or a strong interpenetrating network structure between the coating film and the PCL substrate, greatly enhancing the interfacial chemical bonding force.

[0020] 2) Bulk cross-linking enhancement: The electron beam simultaneously induces mild cross-linking of the PCL surface molecular chains and the paint film bulk, which improves the mechanical strength of the substrate surface and the cohesive force of the paint film, and together resists peel stress.

[0021] 3) Surface smoothing and curing: Irradiation can further cure the paint film evenly, eliminate internal stress, and make the surface smoother and denser.

[0022] The beneficial effects of the present invention.

[0023] Excellent isolation and aesthetic effects: Water curtain spraying can form a uniform, smooth, and color-controllable coating, effectively isolating the PCL substrate from direct contact with the human body and enhancing the product's appearance and texture.

[0024] Revolutionary coating adhesion: Through electron beam irradiation, the traditional physical adsorption-based bonding method is transformed into a strong chemical bond / network interpenetration bonding, which can improve the coating adhesion by more than 3 levels.

[0025] Environmentally friendly and efficient process: Water curtain spraying is environmentally friendly, electron beam irradiation is a cold processing process that does not cause thermal deformation of PCL substrate, and the processing speed is fast, making it suitable for continuous production.

[0026] Biosafety assurance: The entire process uses medical-grade raw materials, and electron beam irradiation simultaneously achieves efficient sterilization, eliminating the need for additional sterilization steps and introducing no toxic chemical cross-linking agents. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the interaction between the electron beam irradiated coating and the substrate interface.

[0028] Figure 2 This is a comparison chart of the coating adhesion test results of PCL samples before and after treatment in Example 1 using the cross-cut adhesion test. Detailed Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1: Surface treatment of orthopedic fixation plate The orthopedic fixation plate made of PCL (molecular weight 50,000) was ultrasonically cleaned with anhydrous ethanol and dried.

[0031] In a water curtain spray booth, medical-grade acrylic resin coating is sprayed, with a dry film thickness of approximately 15 μm. It is then dried in a 50℃ oven for 60 minutes.

[0032] The workpiece was placed in an electron beam irradiator and uniformly irradiated with a dose of 15 kGy at an energy of 10.0 MeV.

[0033] Testing: Cross-cut adhesion test achieved the highest grade 5B in ASTM D3359 (1B for untreated samples). At a measurement angle of 20°, surface gloss improved from 11.8 RU (unpainted) to 39.3 RU (after paint irradiation).

[0034] Example 2: Surface treatment of tissue engineering scaffolds: Take the 3D printed PCL porous bracket.

[0035] Spray a hydrophilic medical-grade acrylic coating to a dry film thickness of approximately 8 μm. Dry at 50°C for 60 minutes.

[0036] Electron beam irradiation was performed in a nitrogen atmosphere at an energy of 10 MeV and a dose of 50 kGy.

[0037] Test: The coating uniformly covered the complex three-dimensional structure of the scaffold. No visible peeling of the coating was observed after ultrasonic vibration (30 min).

[0038] Comparative example: Before painting, the surface gloss of PCL sheets is only about 10 RU. PCL samples that only undergo water curtain painting and thermosetting (without electron beam irradiation) have a coating cross-cut adhesion test grade of 1B or below.

[0039] like Figure 1 The diagram illustrates the interaction between the coating and the substrate interface after electron beam irradiation. Layers A and C are the upper and lower coatings of the PCL substrate material, respectively. Electron irradiation causes chain scission and cross-linking at the coating-substrate interface, significantly increasing the adhesion between the coating and the substrate material.

[0040] like Figure 2 The image shows a comparison of the cross-cut adhesion test results of the PCL sample coatings before and after irradiation with a dose of 15 kGy in Example 1. It can be clearly seen from the image that the coating on the PCL surface before irradiation has a large area of ​​peeling off, while the coating of the PCL sample after irradiation with a dose of 15 kGy has not shown obvious peeling off.

Claims

1. A surface treatment method for medical PCL materials based on electron beam irradiation enhanced coating, characterized in that, Includes the following steps; S1: Medical devices or components made from medical-grade PCL raw materials that meet pharmacopoeia standards, are free of cytotoxicity and heavy metal residues, are cleaned and dried to remove surface grease and dust, and PCL workpieces are obtained. S2: Place the pre-treated PCL workpiece in a water curtain spray booth and spray it with paint. S3: Dry the painted workpiece in a clean oven at 40-50℃ for 60-90 minutes to form a coated workpiece with a uniform and smooth surface. S4: The dried coated workpiece is sent into an electron accelerator for irradiation treatment; S5: The irradiated workpiece is equilibrated at room temperature, and then the coating performance is tested.

2. The surface treatment method for medical PCL materials based on electron beam irradiation enhanced coating according to claim 1, characterized in that, In S2, the paint is water-based polyurethane, medical acrylic resin, or biodegradable polyester-based paint.

3. The surface treatment method for medical PCL materials based on electron beam irradiation enhanced coating according to claim 2, characterized in that, The air pressure of the spray gun is controlled at 0.3-0.7 MPa, and the distance between the spray gun and the workpiece is 5-20 cm. Through multiple thin-layer sprayings, the dry film thickness is controlled at 15-45 μm.

4. The surface treatment method for medical PCL materials based on electron beam irradiation enhanced coating according to claim 1, characterized in that, In S4, during the irradiation treatment, the electron beam energy is 5-10.0 MeV, and the irradiation dose is 15-50 kGy.

5. The surface treatment method for medical PCL materials based on electron beam irradiation enhanced coating according to claim 1, characterized in that, The electron accelerator generates a controllable deflection magnetic field by scanning magnets, and, in conjunction with nonlinear quasi-triangular wave current drive and conveyor belt speed matching, broadens the Gaussian distributed thin beam of electrons into a uniform electron curtain.

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