Medical dilator pp material and method for producing the same

Abstract

The application discloses a medical dilator PP material and a preparation method thereof, relates to the technical field of high-performance polypropylene materials, and belongs to the patent classification C08L23 / 12. The method comprises the following steps: firstly, calcining and silanizing surface modification are performed on nano-hydroxyapatite to obtain silanized nano-hydroxyapatite with surface grafted amino groups; then, polypropylene, the modified nano-hydroxyapatite and maleic anhydride grafted polypropylene are premixed, melt blended through a double-screw extruder and granulated to prepare base composite material particles; the base particles are mixed with a dibenzyl sorbitol nucleating agent and trimethylolpropane trimethacrylate, and then injection molding is performed, and annealing treatment is performed on the sample; finally, electron beam irradiation is performed on the sample under an inert atmosphere, and the medical dilator PP material is obtained after standing and stabilization. The medical dilator PP material prepared by the method has excellent mechanical strength.

Description

Technical Field

[0001] This invention relates to the field of high-performance polypropylene materials technology, belonging to patent classification number C08L23 / 12, specifically to a medical expander PP material and its preparation method. Background Technology

[0002] Medical expanders are indispensable passive medical devices in multidisciplinary clinical diagnosis and treatment. They are widely used in obstetrics and gynecology for vaginal and cervical examination and dilation, plastic surgery for skin and soft tissue dilation, and vascular interventions. Their core function is to expand and extend cavities or tissues through mechanical action, creating conditions for diagnostic procedures or subsequent treatments. These devices typically include functional actuators (such as dilation bladders, dilation blades, balloons, etc.) and operating parts (such as handles, connectors, etc.). Depending on the application, they can be divided into disposable sterile types and reusable types, with disposable products being more widely used due to the avoidance of cross-infection.

[0003] Currently, the materials used in the manufacture of medical specula are mainly divided into two categories: metals and polymers. Metal materials, primarily stainless steel and brass, are mostly used in reusable surgical specula, but they have drawbacks such as being heavy, prone to causing tissue damage, and requiring strict sterilization. Polymer materials, with their advantages of good biocompatibility, easy molding, and controllable cost, have become the mainstream choice for disposable medical specula. Among them, polypropylene (PP) is widely used in the manufacture of various specula products such as vaginal specula and cervical dilators due to its good processing fluidity, chemical stability, and bioinertness.

[0004] However, existing polypropylene materials used in medical expanders have significant mechanical property defects, making it difficult to meet the safety requirements of clinical applications. Pure polypropylene itself has poor impact resistance, and during clinical operations, it is prone to structural fracture or localized damage if it encounters external impact or needs to withstand a certain amount of tension. Summary of the Invention

[0005] The purpose of this invention is to provide a medical expander PP material and its preparation method, thereby solving the technical problem of poor mechanical strength of expander PP materials mentioned in the background art. The expander PP material prepared by this invention has excellent mechanical properties.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for preparing PP material for medical expanders includes the following steps:

[0008] S1. The nano-hydroxyapatite was calcined and then dispersed in a mixed solvent of ethanol and water. Silane coupling agent KH-550 was added, and the reaction was carried out under inert gas protection and heating conditions. After the reaction was completed, the nano-hydroxyapatite with amino grafted on the surface was obtained by separation, washing and drying.

[0009] S2. Polypropylene, silanized nano-hydroxyapatite and maleic anhydride-grafted polypropylene are premixed and then melt-blended and extruded granulated by a twin-screw extruder to obtain basic composite material particles.

[0010] S3. Mix the basic composite material particles, dibenzyl sorbitol nucleating agent and trimethylolpropane trimethacrylate evenly, then perform injection molding, and anneal the injection molded specimen.

[0011] S4. The annealed sample is placed in an inert atmosphere and crosslinked by electron beam irradiation. After irradiation, it is allowed to stand to stabilize, thus obtaining the PP material for medical expanders.

[0012] In this invention, the mechanical properties of the expander PP material are improved through a two-pronged synergistic effect. Firstly, nano-hydroxyapatite undergoes a hydrolysis-condensation reaction with the silane coupling agent KH-550 to form a dense covalently grafted layer, transforming the hydrophilic inorganic nanoparticles into fillers rich in organic amino groups. During melt blending, the anhydride groups of the compatibilizer maleic anhydride grafted onto the polypropylene react with the amino groups on the filler surface, while its polypropylene segments become deeply entangled with the matrix PP molecular chains. This constructs a robust and tough molecular bridge between the nanoparticles and the matrix. When the material is under stress, these uniformly dispersed rigid nanoparticles act as efficient stress transfer points, effectively hindering molecular chain slippage and the expansion of crazing. By bearing and dispersing external stress, the elastic modulus and tensile strength of the material are significantly improved. Simultaneously, the excellent interfacial bonding avoids defects caused by interfacial debonding, preventing early fracture due to stress concentration.

[0013] On the other hand, dibenzyl sorbitol nucleating agents provide a large number of heterogeneous nucleation sites for PP molecular chains, greatly increasing the crystal density. In subsequent annealing, thermal history control promotes molecular chain rearrangement, forming a more complete and finer spherulitic structure. This follows the principle of grain refinement strengthening, where an increase in the number of grain boundaries effectively hinders molecular chain segment movement and plastic deformation under external forces, thereby simultaneously improving the material's strength, hardness, and heat deformation resistance. Furthermore, under electron beam irradiation, trimethylolpropane trimethacrylate, as a multifunctional monomer, is activated and combines with free radicals generated by the PP molecular chains, forming a three-dimensional cross-linked network of covalent bonds between the molecular chains. This network, like a microscopic fishing net, can restrain the movement of molecular chains. Under external impact, the network absorbs and disperses energy through deformation, effectively preventing the propagation of microcracks, thus significantly improving the material's impact toughness and creep resistance. The uniform and refined crystal structure, combined with the pervasive cross-linked network, achieves an optimal balance between the material's rigidity and toughness.

[0014] Preferably, in step S1, the calcination temperature is 150–200°C and the calcination time is 2–3 hours.

[0015] Preferably, in step S1, the mass ratio of nano-hydroxyapatite to silane coupling agent KH-550 is 10:0.5 to 1.0.

[0016] Preferably, in step S2, the silanized nano-hydroxyapatite undergoes a modification treatment, including the following steps:

[0017] S21. Silanized nano-hydroxyapatite was dispersed in anhydrous tetrahydrofuran. Under an inert atmosphere and cooling in an ice-water bath, a tetrahydrofuran solution of 2-bromoisobutyryl bromide was slowly added dropwise to carry out an acylation reaction. After the reaction was completed, the nanoparticles with an initiator fixed on their surface were obtained by centrifugation, washing and drying.

[0018] S22. Nanoparticles with an initiator fixed on their surface, butyl methacrylate monomer, CuBr catalyst and pentamethyldivinyltriamine ligand are added to toluene and heated under an inert atmosphere. After the reaction is completed, the product is obtained by washing and drying.

[0019] In the technical solution of this invention, as described above, trimethylolpropane trimethacrylate (TMT) is activated as a multifunctional monomer under electron beam irradiation. It combines with free radicals generated by the PP molecular chains, forming a three-dimensional cross-linked network with covalent bonds between the molecular chains. Through in-depth research, the invention team discovered that during radiation cross-linking, rigid nano-hydroxyapatite physically hinders the movement and approach of surrounding polymer molecular chains. This makes it difficult for effective cross-linking points to form in the shielded areas, resulting in uneven distribution of the cross-linking network density within the material. This makes the nanoparticles themselves inherent defects in the three-dimensional network. Areas with lower cross-linking density around the nanoparticles are highly susceptible to becoming stress concentration points and crack initiation sites under stress, thus restricting the simultaneous improvement of the material's toughness and mechanical reliability.

[0020] To further address this technical problem, this invention first involves an acylation reaction between the initiator 2-bromoisobutyryl bromide and some amino groups on the surface of silanized nano-hydroxyapatite, covalently anchoring them to the surface of the silanized nanoparticles to construct a molecular-level initiation platform. This platform then initiates atom transfer radical polymerization of butyl methacrylate monomers, growing in situ from the particle surface a flexible polymer brush with controllable density and uniform length. This flexible polymer brush, like countless molecular tentacles, acts as a flexible interface layer, actively participating in the subsequent cross-linking network. This transforms isolated rigid nanoparticles into a network reinforcement hub capable of forming massive entanglements and covalent connections with the matrix, thereby achieving the goal of uniformly transferring stress at the nanoscale, eliminating interface defects, and synergistically improving the overall mechanical properties of the material.

[0021] Preferably, in step S21, the mass ratio of silanized nano-hydroxyapatite to 2-bromoisobutyryl bromide is 5:0.5-0.9.

[0022] Preferably, in step S22, the mass ratio of nanoparticles with initiator fixed on the surface to butyl methacrylate monomer is 1:10-15.

[0023] Preferably, the mass ratio of the polypropylene, the modified silanized nano-hydroxyapatite, and the maleic anhydride-grafted polypropylene is 100:20-25:3-6.

[0024] Preferably, in step S3, the mass ratio of the basic composite material particles, dibenzyl sorbitol nucleating agent, and trimethylolpropane trimethacrylate is 100:0.3-0.6:1-3.

[0025] Preferably, in step S4, the irradiated absorbed dose is 50–60 kGy.

[0026] A medical expander PP material is prepared by the method described above.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. Through the synergistic effect of three mechanisms—rigid nano-hydroxyapatite reinforcement, nucleating agent crystal refinement, and electron beam irradiation crosslinking—not only is the elastic modulus, tensile strength, and hardness of the material significantly improved, but its impact toughness and creep resistance are also greatly enhanced, overcoming the problem of traditional materials being unable to balance strength and toughness.

[0029] 2. By acylation, the initiator 2-bromoisobutyryl bromide is covalently anchored to the surface of silanized nanoparticles, constructing a molecular-level initiation platform. Then, this platform is used to initiate the atom transfer radical polymerization of butyl methacrylate monomer, growing in situ from the particle surface a flexible polymer brush with controllable density and uniform length. This flexible polymer brush, like countless molecular tentacles, acts as a flexible interface layer, actively participating in the subsequent cross-linking network. It transforms isolated rigid nanoparticles into network reinforcement centers that can form massive entanglements and covalent connections with the matrix, thereby achieving the goal of uniformly transferring stress at the nanoscale, eliminating interface defects, and synergistically improving the comprehensive mechanical properties of the material. Attached Figure Description

[0030] Figure 1 This is a SEM image of the surface of the PP material used in the medical expander prepared according to the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing PP material for medical expanders includes the following steps:

[0034] Step 1: Weigh 10.0 g of nano-hydroxyapatite and place it in a muffle furnace. Calcinate it in air at 190 °C for 2.5 h. Disperse the calcined nano-hydroxyapatite in 200 mL of a mixed solvent of anhydrous ethanol and deionized water (95:5 volume ratio). Treat the solution with a 500 W ultrasonic processor for 30 min to form a homogeneous suspension. Then, under mechanical stirring, slowly add 0.9 g of silane coupling agent KH-550 to the suspension. Transfer the mixture to a three-necked flask equipped with a reflux condenser and react it in an oil bath at 80 °C for 6 h under nitrogen protection. After the reaction, separate the white precipitate by high-speed centrifugation (8000 rpm, 10 min), wash it three times with anhydrous ethanol, and finally dry it in a vacuum drying oven at 80 °C for 6 h to obtain silanized nano-hydroxyapatite with amino-grafted surface.

[0035] Step 2: 5g of silanized nano-hydroxyapatite was dispersed in 100mL of anhydrous tetrahydrofuran, and then 1.5mL of triethylamine was added. Under ice-water bath and nitrogen protection, 20mL of anhydrous THF solution containing 0.8g of 2-bromoisobutyryl bromide was slowly added dropwise using a constant pressure dropping funnel, controlling the dropping rate to complete within 1 hour. The reaction was then allowed to continue at room temperature for 12 hours. After the reaction was complete, unreacted reagents were removed by centrifugation and THF washing, and the nanoparticles with the initiator immobilized on their surface were obtained after vacuum drying.

[0036] 1.0 g of nanoparticles with an initiator immobilized on their surface, 14 g of butyl methacrylate monomer, 0.05 g of CuBr catalyst, and 0.12 g of pentamethyldivinyltriamine (PMDETA) ligand, along with 30 mL of toluene as solvent, were added sequentially to a reaction flask. After deoxygenation, the reaction system was polymerized in an oil bath at 70 °C for 6 h under an inert atmosphere. After the reaction was complete, the mixture was washed several times by alternating centrifugation with large amounts of toluene and ethanol until the supernatant was colorless and transparent. The supernatant was then vacuum dried at 60 °C for 24 h to obtain modified silanized nano-hydroxyapatite.

[0037] Weigh 100g of medical-grade polypropylene granules, 24g of modified silanized nano-hydroxyapatite, and 5g of maleic anhydride-grafted polypropylene, and premix them in a high-speed mixer for 5 minutes. Then, feed the premix into the hopper of a twin-screw extruder. Set the temperatures of each section of the extruder (from the feeding section to the die head) to 170℃, 180℃, 190℃, 195℃, and 195℃, respectively, and maintain a constant screw speed of 180 rpm. After melt blending, the materials are extruded from the die head, cooled in a water bath, and finally granulated using a pelletizer to obtain basic composite material granules.

[0038] Step 3: Weigh 100g of basic composite material particles, 0.5g of dibenzyl sorbitol nucleating agent (Millad 3988), and 2.5g of trimethylolpropane trimethacrylate (TMPTMA) crosslinking agent. Mix them in a high-speed mixer at room temperature for 5 minutes to ensure uniform dispersion. Then, immediately use an injection molding machine to injection mold the mixture into standard mechanical test specimens at a barrel temperature of 190°C and a mold temperature of 60°C. Carefully place the injection-molded specimens flat on a heat-resistant tray and immediately place them in a programmed temperature-controlled oven for annealing: heat from room temperature to 135°C at a heating rate of 2°C / min, maintain the temperature at 135°C for 2 hours, and finally cool to below 60°C at a slow cooling rate of 1°C / min.

[0039] Step 4: Arrange the annealed sample strips tightly on the sample tray of the electron beam irradiation device. Before irradiation, continuously purge the sample chamber with high-purity nitrogen gas for 15 minutes. Then, irradiate the sample strips at room temperature using an electron beam irradiation device (energy 10 MeV, beam current 1 mA), controlling the absorbed dose to 55 kGy. After irradiation, remove the sample strips and allow them to stand at room temperature and in the dark for 24 hours to obtain the PP material for medical expanders.

[0040] Example 2

[0041] A method for preparing PP material for medical expanders includes the following steps:

[0042] Step 1: Weigh 10.0g of nano-hydroxyapatite and place it in a muffle furnace. Calcinate it in air at 160℃ for 2.5h. Disperse the calcined nano-hydroxyapatite in 200mL of a mixed solvent of anhydrous ethanol and deionized water (95:5 volume ratio). Treat the solution with a 500W ultrasonic processor for 30min to form a homogeneous suspension. Then, under mechanical stirring, slowly add 0.6g of silane coupling agent KH-550 to the suspension. Transfer the mixture to a three-necked flask equipped with a reflux condenser and react it in an oil bath at 80℃ for 6h under nitrogen protection. After the reaction, separate the white precipitate by high-speed centrifugation (8000rpm, 10min), wash it three times with anhydrous ethanol, and finally dry it in a vacuum drying oven at 80℃ for 6h to obtain silanized nano-hydroxyapatite with amino-grafted surfaces.

[0043] Step 2: 5g of silanized nano-hydroxyapatite was dispersed in 100mL of anhydrous tetrahydrofuran, and then 1.5mL of triethylamine was added. Under ice-water bath and nitrogen protection, 20mL of anhydrous THF solution containing 0.7g of 2-bromoisobutyryl bromide was slowly added dropwise using a constant pressure dropping funnel, controlling the dropping rate to complete within 1 hour. The reaction was then allowed to continue at room temperature for 12 hours. After the reaction was complete, unreacted reagents were removed by centrifugation and THF washing, and the nanoparticles with the initiator immobilized on their surface were obtained after vacuum drying.

[0044] 1.0 g of nanoparticles with an initiator immobilized on their surface, 12 g of butyl methacrylate monomer, 0.05 g of CuBr catalyst, and 0.12 g of pentamethyldivinyltriamine (PMDETA) ligand, along with 30 mL of toluene as solvent, were added sequentially to a reaction flask. After removing oxygen, the reaction system was polymerized in an oil bath at 70 °C for 6 h under an inert atmosphere. After the reaction was complete, the mixture was washed several times by alternating centrifugation with large amounts of toluene and ethanol until the supernatant was colorless and transparent. The supernatant was then vacuum dried at 60 °C for 24 h to obtain modified silanized nano-hydroxyapatite.

[0045] Weigh 100g of medical-grade polypropylene granules, 22g of modified silanized nano-hydroxyapatite, and 4g of maleic anhydride-grafted polypropylene, and premix them in a high-speed mixer for 5 minutes. Then, feed the premix into the hopper of a twin-screw extruder. Set the temperatures of each section of the extruder (from the feeding section to the die head) to 170℃, 180℃, 190℃, 195℃, and 195℃, respectively, and maintain a constant screw speed of 180 rpm. After melt blending, the material is extruded from the die head, cooled in a water bath, and finally granulated using a pelletizer to obtain basic composite material granules.

[0046] Step 3: Weigh 100g of basic composite material particles, 0.4g of dibenzyl sorbitol nucleating agent (Millad 3988), and 1.5g of trimethylolpropane trimethacrylate (TMPTMA) crosslinking agent. Mix them in a high-speed mixer at room temperature for 5 minutes to ensure uniform dispersion. Then, immediately use an injection molding machine to injection mold the mixture into standard mechanical test specimens at a barrel temperature of 190°C and a mold temperature of 60°C. Carefully place the injection-molded specimens flat on a heat-resistant tray and immediately place them in a programmed temperature-controlled oven for annealing: heat from room temperature to 135°C at a heating rate of 2°C / min, maintain the temperature at 135°C for 2 hours, and finally cool to below 60°C at a slow cooling rate of 1°C / min.

[0047] Step 4: Arrange the annealed sample strips tightly on the sample tray of the electron beam irradiation device. Before irradiation, continuously purge the sample chamber with high-purity nitrogen gas for 15 minutes. Then, irradiate the sample strips at room temperature using an electron beam irradiation device (energy 10 MeV, beam current 1 mA), controlling the absorbed dose to 55 kGy. After irradiation, remove the sample strips and allow them to stand at room temperature and in the dark for 24 hours to obtain the PP material for medical expanders.

[0048] Example 3

[0049] A method for preparing PP material for medical expanders includes the following steps:

[0050] Step 1: Weigh 10.0 g of nano-hydroxyapatite and place it in a muffle furnace. Calcinate it in air at 180 °C for 2.5 h. Disperse the calcined nano-hydroxyapatite in 200 mL of a mixed solvent of anhydrous ethanol and deionized water (95:5 volume ratio). Treat the solution with a 500 W ultrasonic processor for 30 min to form a homogeneous suspension. Then, under mechanical stirring, slowly add 0.8 g of silane coupling agent KH-550 to the suspension. Transfer the mixture to a three-necked flask equipped with a reflux condenser and react it in an oil bath at 80 °C for 6 h under nitrogen protection. After the reaction, separate the white precipitate by high-speed centrifugation (8000 rpm, 10 min), wash it three times with anhydrous ethanol, and finally dry it in a vacuum drying oven at 80 °C for 6 h to obtain silanized nano-hydroxyapatite with amino-grafted surface.

[0051] Step 2: 5g of silanized nano-hydroxyapatite was dispersed in 100mL of anhydrous tetrahydrofuran, and then 1.5mL of triethylamine was added. Under ice-water bath and nitrogen protection, 20mL of anhydrous THF solution containing 0.7g of 2-bromoisobutyryl bromide was slowly added dropwise using a constant pressure dropping funnel, controlling the dropping rate to complete within 1 hour. The reaction was then allowed to continue at room temperature for 12 hours. After the reaction was complete, unreacted reagents were removed by centrifugation and THF washing, and the nanoparticles with the initiator immobilized on their surface were obtained after vacuum drying.

[0052] 1.0 g of nanoparticles with an initiator immobilized on their surface, 13 g of butyl methacrylate monomer, 0.05 g of CuBr catalyst, and 0.12 g of pentamethyldivinyltriamine (PMDETA) ligand, along with 30 mL of toluene as solvent, were added sequentially to a reaction flask. After deoxygenation, the reaction system was polymerized in an oil bath at 70 °C for 6 h under an inert atmosphere. After the reaction was complete, the mixture was washed several times by alternating centrifugation with large amounts of toluene and ethanol until the supernatant was colorless and transparent. The supernatant was then vacuum dried at 60 °C for 24 h to obtain modified silanized nano-hydroxyapatite.

[0053] Weigh 100g of medical-grade polypropylene granules, 23g of modified silanized nano-hydroxyapatite, and 4.5g of maleic anhydride-grafted polypropylene, and premix them in a high-speed mixer for 5 minutes. Then, feed the premix into the hopper of a twin-screw extruder. Set the temperatures of each section of the extruder (from the feeding section to the die head) to 170℃, 180℃, 190℃, 195℃, and 195℃, respectively, and maintain a constant screw speed of 180 rpm. After melt blending, the materials are extruded from the die head, cooled in a water bath, and finally granulated using a pelletizer to obtain basic composite material granules.

[0054] Step 3: Weigh 100g of basic composite material particles, 0.45g of dibenzyl sorbitol nucleating agent (Millad3988), and 2g of trimethylolpropane trimethacrylate (TMPTMA) crosslinking aid. Mix them in a high-speed mixer at room temperature for 5 minutes to ensure uniform dispersion. Then, immediately use an injection molding machine to injection mold the mixture into standard mechanical test specimens at a barrel temperature of 190°C and a mold temperature of 60°C. Carefully place the injection-molded specimens flat on a heat-resistant tray and immediately place them in a programmed temperature-controlled oven for annealing: heat from room temperature to 135°C at a heating rate of 2°C / min, maintain the temperature at 135°C for 2 hours, and finally cool to below 60°C at a slow cooling rate of 1°C / min before removing them.

[0055] Step 4: Arrange the annealed sample strips tightly on the sample tray of the electron beam irradiation device. Before irradiation, continuously purge the sample chamber with high-purity nitrogen gas for 15 minutes. Then, irradiate the sample strips at room temperature using an electron beam irradiation device (energy 10 MeV, beam current 1 mA), controlling the absorbed dose to 55 kGy. After irradiation, remove the sample strips and allow them to stand at room temperature and in the dark for 24 hours to obtain the PP material for medical expanders.

[0056] Example 4

[0057] A method for preparing PP material for medical expanders includes the following steps:

[0058] Step 1: Weigh 10.0g of nano-hydroxyapatite and place it in a muffle furnace. Calcinate it in air at 200℃ for 3 hours. Disperse the calcined nano-hydroxyapatite in 200mL of a mixed solvent of anhydrous ethanol and deionized water (95:5 volume ratio). Treat the solution with a 500W ultrasonic processor for 30 minutes to form a homogeneous suspension. Then, under mechanical stirring, slowly add 1.0g of silane coupling agent KH-550 to the suspension. Transfer the mixture to a three-necked flask equipped with a reflux condenser and react it in an oil bath at 80℃ for 6 hours under nitrogen protection. After the reaction, separate the precipitate by high-speed centrifugation (8000 rpm, 10 minutes), wash it three times with anhydrous ethanol, and finally dry it in a vacuum drying oven at 80℃ for 6 hours to obtain silanized nano-hydroxyapatite with amino-grafted surfaces.

[0059] Step 2: 5g of silanized nano-hydroxyapatite was dispersed in 100mL of anhydrous tetrahydrofuran, and then 1.5mL of triethylamine was added. Under ice-water bath and nitrogen protection, 20mL of anhydrous THF solution containing 0.9g of 2-bromoisobutyryl bromide was slowly added dropwise using a constant pressure dropping funnel, controlling the dropping rate to complete within 1 hour. The reaction was then allowed to continue at room temperature for 12 hours. After the reaction was complete, unreacted reagents were removed by centrifugation and THF washing, and the nanoparticles with the initiator immobilized on their surface were obtained after vacuum drying.

[0060] 1.0 g of nanoparticles with an initiator immobilized on their surface, 15 g of butyl methacrylate monomer, 0.05 g of CuBr catalyst, and 0.12 g of pentamethyldivinyltriamine (PMDETA) ligand, along with 30 mL of toluene as solvent, were added sequentially to a reaction flask. After deoxygenation, the reaction system was polymerized in an oil bath at 70 °C for 6 h under an inert atmosphere. After the reaction was complete, the mixture was washed several times by alternating centrifugation with large amounts of toluene and ethanol until the supernatant was colorless and transparent. The supernatant was then vacuum dried at 60 °C for 24 h to obtain modified silanized nano-hydroxyapatite.

[0061] Weigh 100g of medical-grade polypropylene granules, 25g of modified silanized nano-hydroxyapatite, and 6g of maleic anhydride-grafted polypropylene, and premix them in a high-speed mixer for 5 minutes. Then, feed the premix into the hopper of a twin-screw extruder. Set the temperatures of each section of the extruder (from the feeding section to the die head) to 170℃, 180℃, 190℃, 195℃, and 195℃, respectively, and maintain a constant screw speed of 180 rpm. After melt blending, the materials are extruded from the die head, cooled in a water bath, and finally granulated using a pelletizer to obtain basic composite material granules.

[0062] Step 3: Weigh 100g of basic composite material particles, 0.6g of dibenzyl sorbitol nucleating agent (Millad 3988), and 3g of trimethylolpropane trimethacrylate (TMPTMA) crosslinking aid. Mix them in a high-speed mixer at room temperature for 5 minutes to ensure uniform dispersion. Then, immediately use an injection molding machine to injection mold the mixture into standard mechanical test specimens at a barrel temperature of 190°C and a mold temperature of 60°C. Carefully place the injection-molded specimens flat on a heat-resistant tray and immediately place them in a programmed temperature-controlled oven for annealing: heat from room temperature to 135°C at a heating rate of 2°C / min, maintain the temperature at 135°C for 2 hours, and finally cool to below 60°C at a slow cooling rate of 1°C / min before removing them.

[0063] Step 4: Arrange the annealed samples tightly on the sample tray of the electron beam irradiation device. Before irradiation, continuously purge the sample chamber with high-purity nitrogen gas for 15 minutes. Then, irradiate the samples at room temperature using an electron beam irradiation device (energy 10 MeV, beam current 1 mA), controlling the absorbed dose to 60 kGy. After irradiation, remove the samples and allow them to stand at room temperature and in the dark for 24 hours to obtain the PP material for medical expanders.

[0064] Example 5

[0065] A method for preparing PP material for medical expanders includes the following steps:

[0066] Step 1: Weigh 10.0g of nano-hydroxyapatite and place it in a muffle furnace. Calcinate it in air at 150℃ for 2 hours. Disperse the calcined nano-hydroxyapatite in 200mL of a mixed solvent of anhydrous ethanol and deionized water (95:5 volume ratio). Treat the solution with a 500W ultrasonic processor for 30 minutes to form a homogeneous suspension. Then, under mechanical stirring, slowly add 0.5g of silane coupling agent KH-550 to the suspension. Transfer the mixture to a three-necked flask equipped with a reflux condenser and react it in an oil bath at 80℃ for 6 hours under nitrogen protection. After the reaction, separate the precipitate by high-speed centrifugation (8000 rpm, 10 minutes), wash it three times with anhydrous ethanol, and finally dry it in a vacuum drying oven at 80℃ for 6 hours to obtain silanized nano-hydroxyapatite with amino-grafted surfaces.

[0067] Step 2: 5g of silanized nano-hydroxyapatite was dispersed in 100mL of anhydrous tetrahydrofuran, and then 1.5mL of triethylamine was added. Under ice-water bath and nitrogen protection, 20mL of anhydrous THF solution containing 0.5g of 2-bromoisobutyryl bromide was slowly added dropwise using a constant pressure dropping funnel, controlling the dropping rate to complete within 1 hour. The reaction was then allowed to continue at room temperature for 12 hours. After the reaction was complete, unreacted reagents were removed by centrifugation and THF washing, and the nanoparticles with the initiator immobilized on their surface were obtained after vacuum drying.

[0068] 1.0 g of nanoparticles with an initiator immobilized on their surface, 10 g of butyl methacrylate monomer, 0.05 g of CuBr catalyst, and 0.12 g of pentamethyldivinyltriamine (PMDETA) ligand, along with 30 mL of toluene as solvent, were added sequentially to a reaction flask. After deoxygenation, the reaction system was polymerized in an oil bath at 70 °C for 6 h under an inert atmosphere. After the reaction was complete, the mixture was washed several times by alternating centrifugation with large amounts of toluene and ethanol until the supernatant was colorless and transparent. The supernatant was then vacuum dried at 60 °C for 24 h to obtain modified silanized nano-hydroxyapatite.

[0069] Weigh 100g of medical-grade polypropylene granules, 20g of modified silanized nano-hydroxyapatite, and 3g of maleic anhydride-grafted polypropylene, and premix them in a high-speed mixer for 5 minutes. Then, feed the premix into the hopper of a twin-screw extruder. Set the temperatures of each section of the extruder (from the feeding section to the die head) to 170℃, 180℃, 190℃, 195℃, and 195℃, respectively, and maintain a constant screw speed of 180 rpm. After melt blending, the materials are extruded from the die head, cooled in a water bath, and finally granulated using a pelletizer to obtain basic composite material granules.

[0070] Step 3: Weigh 100g of basic composite material particles, 0.3g of dibenzyl sorbitol nucleating agent (Millad 3988), and 1g of trimethylolpropane trimethacrylate (TMPTMA) crosslinking aid. Mix them in a high-speed mixer at room temperature for 5 minutes to ensure uniform dispersion. Then, immediately use an injection molding machine to injection mold the mixture into standard mechanical test specimens at a barrel temperature of 190°C and a mold temperature of 60°C. Carefully place the injection-molded specimens flat on a heat-resistant tray and immediately place them in a programmed temperature-controlled oven for annealing: heat from room temperature to 135°C at a heating rate of 2°C / min, maintain the temperature at 135°C for 2 hours, and finally cool to below 60°C at a slow cooling rate of 1°C / min before removing them.

[0071] Step 4: Arrange the annealed sample strips tightly on the sample tray of the electron beam irradiation device. Before irradiation, continuously purge the sample chamber with high-purity nitrogen gas for 15 minutes. Then, irradiate the sample strips at room temperature using an electron beam irradiation device (energy 10 MeV, beam current 1 mA), controlling the absorbed dose to 50 kGy. After irradiation, remove the sample strips and allow them to stand at room temperature and in the dark for 24 hours to obtain the PP material for medical expanders.

[0072] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that steps 1 and 2 are omitted in the preparation process of the medical expander PP material, and the basic composite material particles in step 3 are replaced with medical polypropylene particles of equal mass.

[0073] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that in the preparation process of the PP material for the medical expander, step 2 replaces the modified silanized nano-hydroxyapatite with alkylated nano-hydroxyapatite, that is, the silanized nano-hydroxyapatite is not modified.

[0074] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that steps 3 and 4 are omitted in the preparation process of the PP material for the medical expander.

[0075] Performance testing:

[0076] 1. Tensile Strength and Elastic Modulus Testing: According to GB / T 1040.2-2006 "Determination of Tensile Properties of Plastics - Part 2: Test Conditions for Molded and Extruded Plastics", Type I standard tensile specimens (4 mm thickness, 10 mm width, gauge length 50 mm) were prepared from the materials of each embodiment and comparative example. An electronic universal testing machine was used, with a tensile speed of 50 mm / min, an ambient temperature of (23±2)℃, and a relative humidity of (50±5)%. Each sample was tested 5 times, and the maximum load at fracture was recorded to calculate the tensile strength. The elastic modulus was calculated using the slope of the linear segment of the stress-strain curve, and the average value was taken as the final result. The test results are shown in Table 1.

[0077] 2. Impact Strength Test of Simply Supported Beams: According to GB / T 1043.1-2008 "Determination of Impact Properties of Simply Supported Beams in Plastics - Part 1: Non-Instrumental Impact Testing", a type A notched standard specimen (thickness 4 mm, width 10 mm, notch depth 2 mm, remaining thickness 8 mm) was prepared. A simply supported beam impact testing machine was used, with an impact energy of 5.5 J, a pendulum angle of 150°, and an ambient temperature of (23±2) ℃. Each sample was tested 5 times, and the average value after removing outliers was taken as the impact strength of the notched simply supported beam. The test results are shown in Table 1.

[0078] 3. Bending Strength Test: Standard bending specimens (80mm length, 10mm width, 4mm thickness) were prepared according to GB / T 9341-2008 "Determination of Bending Properties of Plastics". An electronic universal testing machine was used, with a bending speed of 2mm / min, a support span of 64mm (span / thickness = 16:1), and an ambient temperature of (23±2)℃. Loading was stopped when the specimen broke or the deformation reached 5%. Each sample was tested 5 times, and the bending strength was calculated using the formula, with the average value taken. The test results are shown in Table 1.

[0079] Table 1:

[0080]

[0081] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing PP material for medical expanders, characterized in that, Includes the following steps: S1. The nano-hydroxyapatite was calcined and then dispersed in a mixed solvent of ethanol and water. Silane coupling agent KH-550 was added, and the reaction was carried out under inert gas protection and heating conditions. After the reaction was completed, the nano-hydroxyapatite with amino grafted on the surface was obtained by separation, washing and drying. S2. Polypropylene, modified silanized nano-hydroxyapatite and maleic anhydride-grafted polypropylene are premixed, and the mass ratio of polypropylene, modified silanized nano-hydroxyapatite and maleic anhydride-grafted polypropylene is 100:20-25:3-6. Then, the mixture is melt-blended and extruded into granules using a twin-screw extruder to obtain basic composite material particles. The preparation method of modified silanized nano-hydroxyapatite includes the following steps: S21. Silanized nano-hydroxyapatite was dispersed in anhydrous tetrahydrofuran. Under an inert atmosphere and cooling in an ice-water bath, a tetrahydrofuran solution of 2-bromoisobutyryl bromide was slowly added dropwise to carry out an acylation reaction. The mass ratio of silanized nano-hydroxyapatite to 2-bromoisobutyryl bromide was 5:0.5-0.

9. After the reaction was completed, the nanoparticles with an initiator fixed on their surface were obtained by centrifugation, washing and drying. S22. Nanoparticles with an initiator fixed on their surface, butyl methacrylate monomer, CuBr catalyst and pentamethyldivinyltriamine ligand are added to toluene. The mass ratio of nanoparticles with an initiator fixed on their surface to butyl methacrylate monomer is 1:10-15. The reaction is carried out under an inert atmosphere and heated. After the reaction is completed, the product is washed and dried to obtain the final product. S3. Mix the basic composite material particles, dibenzyl sorbitol nucleating agent and trimethylolpropane trimethacrylate evenly, then perform injection molding, and anneal the injection molded specimen. S4. The annealed sample is placed in an inert atmosphere and crosslinked by electron beam irradiation. After irradiation, it is allowed to stand to stabilize, thus obtaining the PP material for medical expanders.

2. The method for preparing a medical expander PP material according to claim 1, characterized in that, In step S1, the calcination temperature is 150-200℃ and the calcination time is 2-3 hours.

3. The method for preparing a medical expander PP material according to claim 1, characterized in that, In step S1, the mass ratio of nano-hydroxyapatite to silane coupling agent KH-550 is 10:0.5~1.

0.

4. The method for preparing a medical expander PP material according to claim 1, characterized in that, In step S3, the mass ratio of the basic composite material particles, dibenzyl sorbitol nucleating agent, and trimethylolpropane trimethacrylate is 100:0.3-0.6:1-3.

5. The method for preparing a medical expander PP material according to claim 1, characterized in that, In step S4, the irradiated absorbed dose is 50–60 kGy.

6. A medical expander PP material, characterized in that, It is prepared by the method described in any one of claims 1 to 5 above.

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