TPE composite material for medical pistons and method for producing same

Abstract

The present application relates to a kind of TPE composite material for medical piston and its preparation method, the TPE composite material is by SEBS, SEEPS, POE, PP, SEBS-g-MAH, white oil, naphthenic oil, surface activation treated calcium carbonate, modified nano-silica, hydrogenated petroleum resin, antioxidant, erucic amide and silicone master batch according to specific mass fraction composition.The present application is formed by the more complete microphase separation structure of SEBS and SEEPS double elastomer compound, combines white oil and naphthenic oil compound oil, erucic amide and silicone master batch compound lubrication and the interface bonding of surface activation calcium carbonate and SEBS-g-MAH, so that material injection molding yield is 97.5% or more, compression permanent deformation is 16%~20%, while meeting the biological evaluation requirement of medical piston, and cost is substantially reduced compared with butyl rubber, suitable for large-scale precision injection molding production of medical piston.

Description

Technical Field

[0001] This invention relates to the field of medical polymer materials technology, specifically to a TPE composite material for medical pistons and its preparation method. Background Technology

[0002] Disposable syringes, pre-filled syringes, and other medical devices are commonly used in clinical practice. The piston inside these devices is a key component for achieving sealing, fluid retention, and injection functions. Currently, butyl rubber is the mainstream material for manufacturing medical pistons. Due to its good airtightness and high chemical stability, butyl rubber has replaced natural rubber as the mainstream material for medical pistons. However, butyl rubber pistons have the following significant drawbacks: First, they are difficult to mold and process, requiring complex processes such as mixing, vulcanization, punching, and cleaning. Traditional medical piston production involves more than twenty steps, making the process cumbersome, energy-intensive, time-consuming, and environmentally polluting. Second, the instability of the vulcanization process leads to a low yield rate. Insufficient vulcanization pressure or excessively fast vulcanization speed can easily cause quality problems such as material shortages, surface bubbles, or wrinkles on the piston surface. Third, they are expensive, with high costs associated with halogenated butyl rubber and high-barrier membrane materials. Fourth, traditional rubber pistons often suffer from insufficient cleanliness in the production environment, resulting in compromised product quality and a tendency for needle punctures and chipping. Therefore, developing a material that can replace butyl rubber, is easy to process, has low cost, and can meet the requirements for use in medical pistons has become an urgent technical problem to be solved in this field.

[0003] In recent years, significant progress has been made in the research of using thermoplastic elastomers (TPEs) to replace traditional vulcanized rubber in the preparation of medical elastomer products. TPEs possess good mechanical properties and excellent aging resistance, require no vulcanization, have a fast molding speed, and allow for multiple recycling of scrap materials. However, when TPEs are used alone in medical pistons, there are performance limitations, making it difficult to simultaneously meet the performance requirements of medical pistons.

[0004] Patent CN104817804A discloses a thermoplastic elastomer material for medical devices. By weight percentage, its formulation includes 20%-50% styrene block copolymer, 15%-40% paraffin oil, 15%-25% polypropylene, 20%-40% thermoplastic dynamic vulcanized rubber, and 0%-15% mineral filler. This material can be directly molded using conventional injection molding machines, and the scraps can be recycled and reused, solving the problems of high production cost, low efficiency, and inability to recycle silicone pistons used in existing medical syringes. However, this patent primarily addresses the difficulty of recycling silicone pistons. Its material system is geared towards general medical devices, and the disclosed component range is relatively broad. It lacks systematic optimization for key performance requirements of medical pistons, such as compression set and seal retention after repeated sliding wear. It also does not address the compatibility design between the material and precision injection molding processes, and still faces challenges in dimensional stability and yield control during precision injection molding.

[0005] Patent CN101584895A discloses an energy-saving and environmentally friendly medical syringe and a material used for its piston. It saves raw materials by improving the piston structure (limiting the ratio of the piston's outer diameter to its inner diameter to the range of 120%–160%), and provides a thermoplastic elastomer material to ensure that all physical properties of the piston meet national standards. However, this patent focuses on reducing material consumption from the perspective of piston structure improvement; the formulation of the TPE material used is relatively simple, and it does not systematically optimize the balance between long-term storage stability, sliding resistance, and sealing performance required for medical pistons.

[0006] Patent CN206252665U discloses a thermoplastic elastomer (TPV) piston for large-capacity cartridge vials. The piston body is made of TPV material, leveraging its advantages such as good elasticity, ease of molding, high dimensional accuracy, and recyclability to solve the problems of complex manufacturing processes, low cleanliness, and the impact of extractable and leachable substances on drug quality associated with halogenated butyl rubber pistons. However, the TPV material formulation in this patent is primarily designed for long-term sealed storage of cartridge vials, focusing on the long-term sealing quality stability within the drug's shelf life. Compared to disposable syringe pistons, cartridge vial pistons have far higher requirements for long-term sealing than for injection molding efficiency, resulting in a fundamentally different material design philosophy. Existing TPV material formulations still lack synergistic design in terms of multi-component components, and when used in syringe piston injection molding, defects such as flash at the drug contact end, product deformation, dimensional deviations, and incomplete filling are prone to occur.

[0007] In summary, while existing thermoplastic elastomer materials and their products have demonstrated the potential to replace butyl rubber in the field of medical pistons, they still have the following shortcomings: First, existing TPE / TPV material formulations are mostly general-purpose medical elastomer formulations with a broad component design. They lack specific component synergistic optimization for dimensional stability, flash and burr control, and high yield requirements during precision injection molding of medical pistons, leading to problems such as burrs, material shortages, and deformation after injection molding. Second, existing technologies have relatively simple means of controlling the mechanical strength, compression set, and processing flowability of TPE materials, lacking multi-component synergistic design, making it difficult to ensure good processability while also considering sealing reliability and long-term storage stability. Third, the molding compatibility of existing TPE material formulations with the complex structures of medical pistons (such as multi-step sealing surfaces, conical liquid-stopping structures, and tail positioning grooves) has not been systematically optimized, making it difficult to achieve a synergistic improvement in low cost, high yield, and overall performance.

[0008] Therefore, there is an urgent need to develop a TPE composite material specifically for medical pistons. Through the synergistic design of component optimization and preparation process, this material can meet the comprehensive requirements of medical pistons for sealing performance, compression set, biocompatibility, and long-term storage stability while ensuring good processability and high yield. Summary of the Invention

[0009] This invention aims to solve the problems of excessive burrs, poor dimensional stability, and large compression set in precision injection molding of existing TPE materials used in medical pistons, and provides a TPE composite material specifically for medical pistons and its preparation method.

[0010] To achieve the above objectives, the present invention provides a TPE composite material for medical pistons, comprising the following components by weight: 15-35 parts of styrene-ethylene-butene-styrene block copolymer (SEBS); 15-30 parts of styrene-ethylene-ethylene-propylene block copolymer (SEEPS); 5-20 parts of ethylene-octene copolymer (POE); 20-50 parts of white oil; 10-30 parts of naphthenic oil; Polypropylene (PP) 12-25 parts; 3-12 parts of maleic anhydride grafted with SEBS (SEBS-g-MAH); 10-20 parts of surface-activated calcium carbonate; 0.1–3 parts of modified nano-silica; 1-6 parts of hydrogenated petroleum resin; Antioxidant 0.1–0.8 parts; Erucamide 0.1–0.5 parts; Silicone masterbatch 0.5 to 2 parts.

[0011] Preferably, the SEBS is linear SEBS with a styrene content of 25% to 35% and a number-average molecular weight of 80,000 to 200,000; the SEEPS has a styrene content of 18% to 30% and a number-average molecular weight of 100,000 to 250,000.

[0012] Preferably, the POE has an octene content of 20% to 40% and a melt index of 0.5 to 10 g / 10 min.

[0013] Preferably, the maleic anhydride grafting rate of the SEBS-g-MAH is 0.5% to 1.5%.

[0014] Preferably, the white oil is a paraffin-based white oil with a kinematic viscosity of 40–100 mmHg at 40°C. 2 / s; the kinematic viscosity of the naphthenic oil at 40°C is 50–90 mm. 2 / s.

[0015] Preferably, the surface-activated calcium carbonate is 1250-3000 mesh calcium carbonate that has been surface-activated with stearic acid; the modified nano silica is nano silica that has been surface-modified with a silane coupling agent to remove hydrophobicity, and its primary particle size is ≤100nm; the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of (1-2):1.

[0016] Preferably, the softening point of the hydrogenated petroleum resin is 100℃~130℃.

[0017] This invention employs SEBS and SEEPS to form a dual elastomer composite matrix. The ethylene-propylene interblock of SEEPS is more regular than the ethylene-butene block of SEBS. During melt blending, they form a more complete and stable microphase separation structure than SEBS alone, resulting in a smoother melt flow front, effectively suppressing flash and burrs, while simultaneously improving dimensional stability and reducing injection shrinkage. POE, as a toughening component, forms a co-continuous phase structure with the SEBS / SEEPS composite matrix due to its low crystallinity, further improving the uniformity of melt flow in the injection mold.

[0018] In SEBS-g-MAH (maleic anhydride-grafted SEBS), the maleic anhydride groups interact strongly with the polar groups on the surface of surface-activated calcium carbonate particles, effectively dispersing the calcium carbonate particles within the matrix. This improves the dimensional stability of the filler system and reduces injection molding shrinkage. Simultaneously, the maleic anhydride groups in SEBS-g-MAH interact with the polar portions of SEEPS, further optimizing the phase structure of the dual-matrix system.

[0019] The oil-filled system uses a blend of white oil and naphthenic oil. White oil (paraffinic white oil) has good compatibility with the SEBS / SEEPS system, effectively swelling the elastomer phase and improving processing fluidity. Naphthenic oil has a higher plasticizing efficiency for the elastomer phase and exhibits good flexibility at lower temperatures. This blend ensures stable elastic recovery properties over a wide temperature range, from low-temperature operation to high-temperature steam sterilization, improving piston sealing and following performance.

[0020] In the filler system, the maleic anhydride groups of SEBS-g-MAH form a strong interaction with the polar groups on the surface of surface-activated calcium carbonate particles, uniformly dispersing the calcium carbonate particles in the matrix and forming an organic-inorganic composite structure with the elastomer network. This significantly reduces injection molding shrinkage and improves the dimensional stability of the product. Modified nano-silica is used as an auxiliary filler, working together with calcium carbonate to optimize the filling effect.

[0021] The cyclic structure of hydrogenated petroleum resin is compatible with the hard segments of polystyrene, while the linear structure is interspersed between the molecular chains of the soft segments of the elastomer. Under compressive stress, it restricts the plastic slippage and overlapping of the soft segments, thereby significantly reducing compression set.

[0022] Erucamide and silicone masterbatch constitute a compound lubrication system. During injection molding, erucamide migrates to the surface of the product as the melt cools, forming a lubricating film and reducing demolding resistance; silicone masterbatch disperses inside the melt, reducing shear resistance. Both reduce resistance from the outside and the inside simultaneously, ensuring smooth melt filling and rapid demolding, thus suppressing the generation of flash and burrs at the source.

[0023] The above systems work synergistically: the oil-filled elastomer matrix provides ample space and structural basis for the anchoring effect of SEBS-g-MAH and the interpenetration of hydrogenated petroleum resin segments; the improved lubrication system allows for more complete filling of the complex mold cavity, thus fully leveraging the dimensional stability effects of microphase separation and filler anchoring; the combined effect of the systems enables the material to possess comprehensive characteristics such as uniform melt flow, rapid curing and shaping, and low demolding resistance during precision injection molding.

[0024] The antioxidant is a combination of hindered phenolic primary antioxidant 1010 and phosphite auxiliary antioxidant 168, which maintains the stability of material properties after high-temperature processing and steam sterilization.

[0025] The present invention also provides a method for preparing the above-mentioned TPE composite material for medical pistons, comprising the following steps: Step 1: Pre-fill with oil SEBS, SEEPS and POE are added to white oil and naphthenic oil and stirred and mixed at 75℃~95℃ for 1~4h. Then the mixture is taken out and left to stand for 24~96h to obtain a pre-filled oil elastomer mixture. Step 2: Ingredient Preparation The pre-filled oil elastomer mixture obtained in step one is added to a high-speed mixer in sequence with PP, SEBS-g-MAH, surface-activated calcium carbonate, modified nano silica, hydrogenated petroleum resin, antioxidant, erucamide, and silicone masterbatch according to the specified ratio. The mixture is stirred at 300-600 r / min for 10-30 min at room temperature to obtain the mixture. Step 3: Granulation The mixture described in step two is added to a twin-screw extruder, and plasticized, mixed, extruded, and pelletized at 180℃~220℃. The residence time of the material in the twin-screw extruder is 1~3 minutes to obtain TPE composite material pellets. Step 4: Drying The TPE composite material granules described in step three are dried at 50℃~70℃ for 2~4h to obtain the TPE composite material for medical pistons.

[0026] Preferably, in the preparation process of the pre-filled oil elastomer mixture in step one, the oil filling temperature is 80℃~90℃, the pre-filling time is 2~3h, and the standing time is 24~48h.

[0027] Preferably, in step three, the length-to-diameter ratio of the twin-screw extruder is 36:1 to 48:1, and the screw speed is 200 to 400 r / min; the temperatures of each section of the extruder are set as follows: feeding section 160℃ to 180℃, melting section 180℃ to 200℃, homogenization section 200℃ to 220℃, and die head temperature 200℃ to 215℃; during granulation, water ring hot cutting or die surface hot cutting is used, and the granule shape is cylindrical or spherical with a particle size of 2 to 4 mm.

[0028] Pre-filling with oil is a key step in the preparation method of this invention. SEBS, SEEPS, and POE are all elastomer materials that need to swell fully in the oil-filling medium to allow oil molecules to penetrate evenly between the polymer chains, thus achieving uniform distribution of the oil-filling effect and stable control of the product hardness. This invention adds all white oil and naphthenic oil at once, ensuring that both oils are fully and uniformly absorbed by the elastomer phase by controlling the oil-filling temperature, time, and settling time. The molecular structures of SEBS and SEEPS contain ethylene-butene (EB) or ethylene-ethylene-propylene (EEP) soft segments that are highly compatible with white oil and naphthenic oil. These saturated olefin segments have similar solubility parameters to paraffin-based white oil and naphthenic oil. According to the principle of "like dissolves like," they can swell fully under heating conditions, absorbing several times their own weight in oil. Heating the oil-filling process helps the oil quickly penetrate into the interior of the elastomer particles, shortening the swelling time. This pre-filling process effectively avoids problems such as oil leaching and product hardness fluctuations during subsequent processing caused by uneven oil absorption.

[0029] In a twin-screw extruder, SEBS, SEEPS, POE, and PP can all be fully melted and plasticized, with each component achieving uniform mixing under the high shear of the twin screw. If the temperature is too low, plasticization will be incomplete, and the components will not disperse sufficiently, affecting material properties; if the temperature is too high, it may cause oil volatilization and decomposition of hydrogenated petroleum resins. Water ring hot cutting or die-face hot cutting is preferred for granulation, producing cylindrical or spherical granules with a particle size of 2–4 mm. Water ring hot cutting and die-face hot cutting are currently the mainstream methods for thermoplastic elastomer granulation, producing granules with regular shapes and uniform sizes, which is beneficial for stable feeding and melt plasticization during subsequent injection molding.

[0030] The granules obtained in step three are dried to remove any moisture that may be adsorbed on the surface, preventing air bubble defects caused by moisture during injection molding, thus obtaining a TPE composite material for medical pistons. The drying temperature should not exceed 70℃ to prevent the granules from softening and sticking together.

[0031] The technical mechanism of this invention lies in the synergistic effect of multiple components. Both SEBS and SEEPS are styrene-based block copolymers, but they differ in molecular structure—the ethylene-propylene mesoblock of SEEPS is more regular than the ethylene-butene block of SEBS. When blended, they form a more complete and stable microphase separation structure than SEBS alone. The integrity of this microphase separation structure directly affects the flow behavior of the injection molded melt: a more complete microphase separation makes the flow front of the melt in the mold cavity smoother, effectively suppressing the generation of flash and burrs. Simultaneously, the product exhibits less dimensional change and lower injection shrinkage during cooling and setting. Both white oil and naphthenic oil are absorbed by SEBS and SEEPS as oiling media, but their effects differ: paraffinic white oil has a similar solubility parameter to the saturated olefin segments of SEBS / SEEPS, allowing for sufficient swelling of the elastomer phase and imparting good processing fluidity and anti-aging properties to the material; naphthenic oil, due to the presence of cycloalkane rings in its molecular structure, has a higher plasticizing efficiency for the elastomer phase and maintains good flexibility even at lower temperatures. When combined, the material maintains stable elastic recovery properties across a wide temperature range, from low-temperature use to high-temperature steam sterilization. The maleic anhydride groups of SEBS-g-MAH form a strong interaction with surface-activated calcium carbonate, effectively dispersing filler particles within the matrix and significantly reducing injection shrinkage. Modified nano-silica, upon addition, acts as a nucleation site to further optimize the system's dimensional stability. The cyclic structure of hydrogenated petroleum resin is compatible with the hard segments of polystyrene, while the linear structure intersperses between the soft segments of the elastomer, restricting plastic slippage and aggregation of the soft segments under compressive stress, thus significantly reducing compression set. Erucamide and silicone masterbatch have different lubrication mechanisms. Erucamide migrates to the surface of the product as the melt cools during injection molding, forming a lubricating film and reducing demolding resistance; silicone masterbatch disperses within the melt, reducing shear resistance. The combination of the two achieves a synergistic lubrication effect of "internal shear reduction + rapid surface migration." The aforementioned systems do not act in isolation: the microphase separation structure provides the structural basis for the interlocking of hydrogenated petroleum resin segments; the improved lubrication system ensures more complete filling of complex mold cavities, thus fully realizing the effects of microphase separation and filler anchoring. Within the aforementioned mass fraction range, the components and systems work synergistically, enabling the material to exhibit comprehensive characteristics during precision injection molding: uniform melt flow, rapid curing and shaping, and low demolding resistance. This allows for the full filling of complex mold cavities without flash or short-fill defects.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In terms of molding and processing, the present invention forms a more complete microphase separation structure by combining SEBS and SEEPS dual elastomers. Combined with the internal and external synergistic lubrication of erucamide and silicone masterbatch, the injection melt fills the mold smoothly and demolds quickly. It effectively solves the problems of flash, burrs, material shortage, deformation and dimensional fluctuation that are easy to occur when injecting existing TPE materials. The injection molding yield reaches more than 97.5%, the key dimension qualification rate reaches more than 98.5%, and the surface is smooth and without defects.

[0033] (2) In terms of sealing and performance, this invention restricts the plastic slippage of the soft segments of the elastomer through the segmental limiting effect of hydrogenated petroleum resin, while SEBS-g-MAH enhances the interfacial bonding between calcium carbonate and the matrix. The two work together to reduce the compression set to 16%–20%, ensuring the sealing and following performance of the piston after long-term compression. The sliding starting force is 3.3–3.8 N, and the continuous force is 2.8–3.2 N, ensuring smooth injection. In addition, this invention uses surface-activated calcium carbonate as a filler, which has low raw material cost, low injection molding scrap rate, and good economic efficiency. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. To enable those skilled in the art to better understand the solutions of this application, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0035] A TPE composite material for use in medical pistons is prepared as follows: S1. Raw material preparation: Weigh the following components according to their mass percentages: 15-35 parts of styrene-ethylene-butene-styrene block copolymer (SEBS) 15-30 parts of styrene-ethylene-ethylene-propylene block copolymer (SEEPS) 5-20 parts of ethylene-octene copolymer (POE) 12-25 parts of polypropylene (PP), 3-12 parts of maleic anhydride grafted with SEBS (SEBS-g-MAH) 20-50 parts of white oil, 10-30 parts of naphthenic oil, 10-20 parts of surface-activated calcium carbonate, 0.1–3 parts of modified nano-silica, 1-6 parts of hydrogenated petroleum resin Antioxidant 0.1–0.8 parts, Erucamide 0.1-0.5 parts, Silicone masterbatch 0.5-2 parts; Among them, SEBS is linear SEBS with a styrene content of 25%–35% and a number-average molecular weight of 80,000–200,000; SEEPS has a styrene content of 18%–30% and a number-average molecular weight of 100,000–250,000; POE has an octene content of 20%–40% and a melt index (190℃ / 2.16kg) of 0.5–10 g / 10 min; SEBS-g-MAH has a maleic anhydride grafting rate of 0.5%–1.5%; and the white oil is paraffin-based white oil with a kinematic viscosity of 40–100 mmHg at 40℃. 2 / s; kinematic viscosity of naphthenic oil at 40℃: 50–90 mm² 2 / s; the surface-activated calcium carbonate is 1250-3000 mesh calcium carbonate that has been surface-activated with stearic acid; the modified nano silica is nano silica that has been hydrophobically modified with silane coupling agent (KH570) and its primary particle size is ≤100nm; the softening point of the hydrogenated petroleum resin is 100℃-130℃; the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of 1:1 to 2:1; S2, Pre-filled oil: SEBS, SEEPS and POE are added to white oil and naphthenic oil, and stirred and mixed at 300-400 r / min for 1-4 hours at 75℃-95℃ to allow the white oil and naphthenic oil to be completely absorbed by SEBS, SEEPS and POE. Then, the mixture is taken out and left to stand for 24-96 hours to obtain a pre-filled oil elastomer mixture. S3. Ingredients: The pre-filled oil elastomer mixture obtained in step S2, along with PP, SEBS-g-MAH, surface-activated calcium carbonate, modified nano silica, hydrogenated petroleum resin, antioxidant, erucamide, and silicone masterbatch, are sequentially added to a high-speed mixer and stirred for 10-30 minutes at room temperature until uniformly mixed. S4. Granulation: The mixture obtained in step S3 is added to a twin-screw extruder and plasticized, mixed, extruded, and granulated at a temperature of 180℃~220℃. The residence time of the material in the twin-screw extruder is 1~3min to obtain TPE composite material granules. The length-to-diameter ratio of the twin-screw extruder is 36:1~48:1, the screw speed is 200~400r / min, and the temperature of each section of the extruder is set as follows: feeding section 160℃~180℃, melting section 180℃~200℃, homogenization section 200℃~220℃, and die head temperature 200℃~215℃. Water ring hot cutting or die surface hot cutting is used for granulation. The granule shape is cylindrical or spherical with a particle size of 2~4mm. S5. Drying: Dry the granules obtained in step S4 at 50℃~70℃ for 2~4 hours.

[0036] All of the above components can be purchased directly from commercially available products.

[0037] Example 1 A TPE composite material for use in medical pistons is prepared as follows: S1. Raw material preparation: Weigh the following components according to their mass percentages: SEBS 25 copies, SEEPS 22 servings 12 copies of POE PP 18 copies, SEBS-g-MAH 8 portions, 35 parts white oil, 20 parts naphthenic oil 15 parts of surface-activated calcium carbonate, 1.5 parts of modified nano-silica, 4 parts of hydrogenated petroleum resin 0.5 parts antioxidant, 0.3 parts erucamide, 1.2 parts silicone masterbatch; Among them, SEBS is linear SEBS with a styrene content of 30% and a number-average molecular weight of 150,000; SEEPS has a styrene content of 25% and a number-average molecular weight of 180,000; POE has an octene content of 30% and a melt index (190℃ / 2.16kg) of 5g / 10min; the maleic anhydride grafting rate of SEBS-g-MAH is 1.0%; and the white oil is paraffin-based white oil with a kinematic viscosity of 60mm at 40℃. 2 / s; Kinematic viscosity of naphthenic oil at 40℃: 70 mm³ / s 2 / s; the surface-activated calcium carbonate is 1250 mesh calcium carbonate that has been surface-activated with stearic acid; the modified nano silica is nano silica that has been surface-modified with a silane coupling agent for hydrophobicity, and its primary particle size is ≤100nm; the softening point of the hydrogenated petroleum resin is 120℃; the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of 1:1; S2, Pre-filled oil: The weighed SEBS, SEEPS and POE are added to the mixture of white oil and naphthenic oil, and stirred and mixed at 85°C for 2.5 hours to allow the white oil and naphthenic oil to be completely absorbed by SEBS, SEEPS and POE. Then, the mixture is taken out and left to stand for 36 hours to obtain the pre-filled oil elastomer mixture. S3. Ingredients: The pre-filled oil elastomer mixture obtained in step S2, along with PP, SEBS-g-MAH, surface-activated calcium carbonate, modified nano silica, hydrogenated petroleum resin, antioxidant, erucamide, and silicone masterbatch, are sequentially added to a high-speed mixer and stirred for 20 minutes at room temperature until uniformly mixed. S4. Granulation: The mixture obtained in step S3 is added to a twin-screw extruder and plasticized, mixed, extruded, and granulated at a temperature of 190℃~210℃. The residence time of the material in the twin-screw extruder is 1~3min to obtain TPE composite material granules. The length-to-diameter ratio of the twin-screw extruder is 40:1, the screw speed is 300r / min, and the temperature of each section of the extruder is set as follows: feeding section 170℃, melting section 190℃, homogenization section 210℃, and die head temperature 205℃. Water ring hot cutting is used during granulation, and the granules are cylindrical with a particle size of 3mm. S5. Drying: Dry the granules obtained in step S4 at 60°C for 3 hours.

[0038] Example 2 A TPE composite material for use in medical pistons is prepared as follows: S1. Raw material preparation: Weigh the following components according to their mass percentages: SEBS 15 copies, SEEPS 15 servings 5 copies of POE PP 12 portions, SEBS-g-MAH 3 copies, 20 parts white oil, 10 parts naphthenic oil 10 parts of surface-activated calcium carbonate, 0.1 parts of modified nano-silica, One part of hydrogenated petroleum resin, 0.1 parts antioxidant, 0.1 parts of erucamide, 0.5 parts silicone masterbatch; Among them, SEBS is linear SEBS with a styrene content of 25% and a number-average molecular weight of 80,000; SEEPS has a styrene content of 18% and a number-average molecular weight of 100,000; POE has an octene content of 20% and a melt index (190℃ / 2.16kg) of 0.5g / 10min; SEBS-g-MAH has a maleic anhydride grafting rate of 0.5%; and the white oil is paraffin-based white oil with a kinematic viscosity of 40mm at 40℃. 2 / s; kinematic viscosity of naphthenic oil at 40℃: 50 mm 2 / s; the surface-activated calcium carbonate is 1250 mesh calcium carbonate that has been surface-activated with stearic acid; the modified nano silica is nano silica that has been surface-modified with silane coupling agent for hydrophobicity, and its primary particle size is ≤100nm; the softening point of the hydrogenated petroleum resin is 100℃; the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of 1:1; S2, Pre-filled oil: SEBS, SEEPS and POE are added to the mixture of white oil and naphthenic oil, and stirred and mixed at 75°C for 1 hour to allow the white oil and naphthenic oil to be completely absorbed by SEBS, SEEPS and POE. Then, the mixture is taken out and left to stand for 24 hours to obtain the pre-filled oil elastomer mixture. S3. Ingredients: The pre-filled oil elastomer mixture obtained in step S2, along with PP, SEBS-g-MAH, surface-activated calcium carbonate, modified nano silica, hydrogenated petroleum resin, antioxidant, erucamide, and silicone masterbatch, are sequentially added to a high-speed mixer and stirred for 10 minutes at room temperature until uniformly mixed. S4. Granulation: The mixture obtained in step S3 is added to a twin-screw extruder and plasticized, mixed, extruded, and granulated at a temperature of 180℃~200℃. The residence time of the material in the twin-screw extruder is 1~3min to obtain TPE composite material granules. The length-to-diameter ratio of the twin-screw extruder is 36:1, the screw speed is 200r / min, and the temperature of each section of the extruder is set as follows: feeding section 160℃, melting section 180℃, homogenization section 200℃, and die head temperature 200℃. Water ring hot cutting is used during granulation, and the granules are cylindrical with a particle size of 2mm. S5. Drying: Dry the granules obtained in step S4 at 50°C for 2 hours.

[0039] Example 3 A TPE composite material for use in medical pistons is prepared as follows: S1. Raw material preparation: Weigh the following components according to their mass percentages: SEBS 35 copies, SEEPS 30 servings 20 copies of POE PP 25 copies, SEBS-g-MAH 12 copies, 50 parts white oil, 30 parts naphthenic oil 20 parts of surface-activated calcium carbonate, 3 parts of modified nano-silica 6 parts of hydrogenated petroleum resin, Antioxidant 0.8 parts, 0.5 parts of erucamide, 2 parts silicone masterbatch; Among them, SEBS is linear SEBS with a styrene content of 35% and a number-average molecular weight of 200,000; SEEPS has a styrene content of 30% and a number-average molecular weight of 250,000; POE has an octene content of 40% and a melt index (190℃ / 2.16kg) of 10g / 10min; the maleic anhydride grafting rate of SEBS-g-MAH is 1.5%; and the white oil is paraffin-based white oil with a kinematic viscosity of 100mm at 40℃. 2 / s; Kinematic viscosity of naphthenic oil at 40°C: 90 mm² 2 / s; the surface-activated calcium carbonate is 3000 mesh calcium carbonate that has been surface-activated with stearic acid; the modified nano silica is nano silica that has been surface-modified with silane coupling agent for hydrophobicity, and its primary particle size is ≤100nm; the softening point of the hydrogenated petroleum resin is 130℃; the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of 2:1; S2, Pre-filled oil: SEBS, SEEPS and POE are added to white oil and naphthenic oil and stirred and mixed at 95°C for 4 hours to allow the white oil and naphthenic oil to be completely absorbed by SEBS, SEEPS and POE. Then, the mixture is taken out and left to stand for 96 hours to obtain a pre-filled oil elastomer mixture. S3. Ingredients: The pre-filled oil elastomer mixture obtained in step S2, along with PP, SEBS-g-MAH, surface-activated calcium carbonate, modified nano silica, hydrogenated petroleum resin, antioxidant, erucamide, and silicone masterbatch, are added sequentially to a high-speed mixer and stirred for 30 minutes at room temperature until uniformly mixed. S4. Granulation: The mixture obtained in step S3 is added to a twin-screw extruder and plasticized, mixed, extruded, and granulated at a temperature of 200℃~220℃. The residence time of the material in the twin-screw extruder is 1~3min to obtain TPE composite material granules. The length-to-diameter ratio of the twin-screw extruder is 48:1, the screw speed is 400r / min, and the temperature of each section of the extruder is set as follows: feeding section 180℃, melting section 200℃, homogenization section 220℃, and die head temperature 215℃. The die surface is hot-cut during granulation, and the granules are spherical with a particle size of 4mm. S5. Drying: Dry the granules obtained in step S4 at 70°C for 4 hours.

[0040] Example 4 A TPE composite material for use in medical pistons is prepared as follows: S1. Raw material preparation: Weigh the following components according to their mass percentages: SEBS 35 copies, SEEPS 30 servings 20 copies of POE PP 25 copies, SEBS-g-MAH 12 copies, 50 parts white oil, 30 parts naphthenic oil 20 parts of surface-activated calcium carbonate, 3 parts of modified nano-silica 6 parts of hydrogenated petroleum resin, Antioxidant 0.8 parts, 0.5 parts of erucamide, 2 parts silicone masterbatch; Among them, SEBS is linear SEBS with a styrene content of 25% and a number-average molecular weight of 80,000; SEEPS has a styrene content of 18% and a number-average molecular weight of 100,000; POE has an octene content of 20% and a melt index (190℃ / 2.16kg) of 0.5g / 10min; the maleic anhydride grafting rate of SEBS-g-MAH is 0.5%; the white oil is paraffinic white oil with a kinematic viscosity of 40mm² / s at 40℃; the naphthenic oil has a kinematic viscosity of 50mm² / s at 40℃; the surface-activated calcium carbonate is 1250-mesh calcium carbonate surface-activated with stearic acid; the modified nano-silica is nano-silica with a primary particle size ≤100nm modified by a silane coupling agent for surface hydrophobicity; the softening point of the hydrogenated petroleum resin is 100℃; the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 1:1. S2, Pre-filled oil: SEBS, SEEPS and POE are added to white oil and naphthenic oil and stirred and mixed at 75°C for 1 hour to allow the white oil and naphthenic oil to be completely absorbed by SEBS, SEEPS and POE. Then, the mixture is taken out and left to stand for 24 hours to obtain a pre-filled oil elastomer mixture. S3. Ingredients: The pre-filled oil elastomer mixture obtained in step S2, along with PP, SEBS-g-MAH, surface-activated calcium carbonate, modified nano silica, hydrogenated petroleum resin, antioxidant, erucamide, and silicone masterbatch, are added sequentially to a high-speed mixer and stirred for 10 minutes at room temperature until uniformly mixed. S4. Granulation: The mixture obtained in step S3 is added to a twin-screw extruder and plasticized, mixed, extruded, and granulated at a temperature of 180℃~200℃. The residence time of the material in the twin-screw extruder is 1~3min to obtain TPE composite material granules. The length-to-diameter ratio of the twin-screw extruder is 36:1, the screw speed is 200r / min, and the temperature of each section of the extruder is set as follows: feeding section 160℃, melting section 180℃, homogenization section 200℃, and die head temperature 200℃. Water ring hot cutting is used during granulation, and the granules are cylindrical with a particle size of 2mm. S5. Drying: Dry the granules obtained in step S4 at 50°C for 2 hours.

[0041] Example 5 A TPE composite material for use in medical pistons is prepared as follows: S1. Raw material preparation: Weigh the following components according to their mass percentages: SEBS 15 copies, SEEPS 15 servings 5 copies of POE PP 12 portions, SEBS-g-MAH 3 copies, 20 parts white oil, 10 parts naphthenic oil 10 parts of surface-activated calcium carbonate, 0.1 parts of modified nano-silica, One part of hydrogenated petroleum resin, 0.1 parts antioxidant, 0.1 parts of erucamide, 0.5 parts silicone masterbatch; Among them, SEBS is linear SEBS with a styrene content of 35% and a number-average molecular weight of 200,000; SEEPS has a styrene content of 30% and a number-average molecular weight of 250,000; POE has an octene content of 40% and a melt index (190℃ / 2.16kg) of 10g / 10min; the maleic anhydride grafting rate of SEBS-g-MAH is 1.5%; the white oil is paraffin-based white oil with a kinematic viscosity of 100mm² / s at 40℃; the naphthenic oil has a kinematic viscosity of 90mm² / s at 40℃; the surface-activated calcium carbonate is 3000-mesh calcium carbonate surface-activated with stearic acid; the modified nano-silica is nano-silica with a primary particle size ≤100nm modified by a silane coupling agent; the softening point of the hydrogenated petroleum resin is 130℃; and the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168 in a mass ratio of 2:1. S2, Pre-filled oil: SEBS, SEEPS and POE are added to white oil and naphthenic oil and stirred and mixed at 95°C for 4 hours to allow the white oil and naphthenic oil to be completely absorbed by SEBS, SEEPS and POE. Then, the mixture is taken out and left to stand for 96 hours to obtain a pre-filled oil elastomer mixture. S3. Ingredients: The pre-filled oil elastomer mixture obtained in step S2, along with PP, SEBS-g-MAH, surface-activated calcium carbonate, modified nano silica, hydrogenated petroleum resin, antioxidant, erucamide, and silicone masterbatch, are added sequentially to a high-speed mixer and stirred for 30 minutes at room temperature until uniformly mixed. S4. Granulation: The mixture obtained in step S3 is added to a twin-screw extruder and plasticized, mixed, extruded, and granulated at a temperature of 200℃~220℃. The residence time of the material in the twin-screw extruder is 1~3min to obtain TPE composite material granules. The length-to-diameter ratio of the twin-screw extruder is 48:1, the screw speed is 400r / min, and the temperature of each section of the extruder is set as follows: feeding section 180℃, melting section 200℃, homogenization section 220℃, and die head temperature 215℃. The die surface is hot-cut during granulation, and the granules are spherical with a particle size of 4mm. S5. Drying: Dry the granules obtained in step S4 at 70°C for 4 hours.

[0042] Comparative Example 1 A TPE composite material for medical pistons differs from Example 1 in that the amount of SEBS is 12 parts and the amount of SEEPS is 40 parts, while the other components and preparation methods are completely consistent with Example 1.

[0043] Comparative Example 2 A TPE composite material for medical pistons differs from Example 1 in that only 55 parts of white oil are used in the pre-filling process, while the other components and preparation methods are completely consistent with Example 1.

[0044] Comparative Example 3 A TPE composite material for medical pistons differs from Example 1 in that: the amount of erucamide is 0 parts, the amount of silicone masterbatch is 3 parts, and the other components and preparation methods are completely consistent with Example 1.

[0045] Comparative Example 4 A TPE composite material for medical pistons differs from Example 1 in that: the amount of SEBS-g-MAH is 0 parts, the calcium carbonate is unactivated ordinary calcium carbonate, and the other components and preparation methods are completely consistent with Example 1.

[0046] Comparative Example 5 A TPE composite material for medical pistons differs from Example 1 in that the amount of hydrogenated petroleum resin used is 10 parts, while the other components and preparation methods are completely consistent with Example 1.

[0047] Comparative Example 6 A TPE composite material for medical pistons differs from Example 1 in that the settling time after pre-filling with oil is changed from 36 hours to 8 hours, while the other components and preparation methods are completely consistent with Example 1.

[0048] Comparative Example 7 A TPE composite material for medical pistons differs from Example 1 in that the temperature of the extruder homogenization section during granulation is changed from 210°C to 235°C, while the other components and preparation methods are completely consistent with Example 1.

[0049] Comparative Example 8 A TPE composite material for medical pistons differs from Example 1 in that the order of addition is changed during the preparation process. Surface-activated calcium carbonate, PP, and SEBS-g-MAH are added simultaneously to the pre-oiled elastomer, and then the lubricant is added. The other components and preparation methods are completely consistent with Example 1.

[0050] Comparative Example 9 A TPE composite material for medical pistons differs from Example 1 in that the pre-filling oil temperature is 105°C, while the other components and preparation methods are completely consistent with Example 1.

[0051] Comparative Example 10 A TPE composite material for medical pistons differs from Example 1 in that the mixing time during the pre-filling process is 0.5 h at 85°C, while the other components and preparation methods are completely consistent with Example 1.

[0052] Comparative Example 11 A TPE composite material for medical pistons differs from Example 1 in that the mixing time is 2 minutes, while the other components and preparation method are completely consistent with Example 1.

[0053] The samples prepared in Examples 1-5 and Comparative Examples 1-11 were subjected to relevant performance tests. The corresponding test methods are shown in Table 1, and the test results are shown in Tables 2-5. Table 2 shows the basic material properties, Table 3 shows the piston functional indicators, Table 4 shows the process and reliability indicators, and Table 5 shows the biocompatibility test results. Given that the above materials are used in medical pistons, the sealing and sliding performance of the finished pistons were tested according to YY / T0243-2016 "Pistons for Disposable Syringes" to ensure their functions of stopping liquid and pushing injection in syringes. Compression set reflects the piston's elastic recovery ability under long-term compression and is a key indicator for evaluating its long-term sealing performance. Hardness, tensile strength, and elongation at break reflect the mechanical properties of the material and affect the assembly and reliability of the piston. Post-sterilization performance retention rate assesses the material's performance stability after steam sterilization, ensuring safe clinical use.

[0054] Table 1 Detection Methods hardness Referring to the test method in GB / T 39693.4-2025, "Determination of Hardness of Vulcanized Rubber or Thermoplastic Rubber - Part 4: Determination of Indentation Hardness by Shore Hardness Tester (Shore Hardness)," a Shore Type A hardness tester should be used, preferably mounted on a stand. The sample thickness should be no less than 6 mm, and can be stacked to achieve the required thickness. The indenter is pressed into the sample under the specified pressure, and the hardness value is read after 15 seconds ± 1 second. Five points are measured for each sample, and the median is taken as the test result. Tensile properties Following the test method in GB / T 528-2009, "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", the samples were prepared and conditioned according to GB / T 2941-2006. A type 1 dumbbell-shaped cutter was used to cut the specimens, with a gauge length of 25 mm ± 0.5 mm. The specimens were continuously stretched at a test speed of 500 mm / min ± 50 mm / min until fracture, and the tensile strength and elongation at break were recorded. Compression permanent deformation <![CDATA[Refer to the test method in GB / T 7759.1-2015, "Rubber, vulcanized or thermoplastic - Determination of compression set - Part 1: At ambient and elevated temperature", Type A specimen (diameter 13 mm ± 0.5 mm, height 6 mm ± 0.3 mm), compression ratio 25%, compression duration 22 h, temperature 23°C ± 2°C. After taking out the specimen, let it freely recover in an environment of 23°C ± 2°C for 30 min and then measure the final height. The calculation formula is: C = (H0 - H1) / (H0 - H s )×100%.]]> Sealing Referring to the test method in YY / T 0243-2016 (Article 5.3), positive pressure sealing: inject water into the syringe, assemble the piston and place it in a special fixture, pressurize to 0.3MPa and hold for 30s, and observe whether water seeps out from the front end of the syringe. Negative pressure sealing: evacuate to -80kPa and hold for 60s, and observe whether air enters at the contact point between the piston and the syringe. Sliding performance Referring to the test method in YY / T 0243-2016 (Clause 5.4), the syringe is filled with water to 50% of its capacity, and the needle tube is clamped vertically downwards in the test frame. A vertically downward force is applied to the mandrel, and the starting force and continuous force are expressed as readings on the force value curve. The initial starting force and continuous sliding resistance of the piston moving in the syringe are measured in 10 cycles. Size and appearance Refer to the testing methods in YY / T 0243-2016 (clauses 5.1-5.2). Inspect visually or with a magnifying glass of no more than 10x under an illuminance of approximately 300 lx; ​​the surface should be smooth, free of bubbles, impurities, missing materials, burrs, and have a uniform color. Use a vernier caliper or projection measuring instrument with an accuracy of not less than 0.02 mm; randomly select a specified number of samples from the sample batch, measure the diameter of the sealing ring and the overall length of the piston, and record the deviations. Injection molding yield On-site production statistics show the percentage of pistons that passed appearance and key dimension inspections within the same production batch, relative to the total injection molding output of that batch. Performance retention rate after sterilization <![CDATA[Before steam sterilization, measure the tensile strength S1 according to GB / T 528-2009 and the compression set C1 according to GB / T 7759.1-2015. After sterilizing the sample, measure the tensile strength S2 and the compression set C2 under the same conditions again. Tensile strength retention rate = S2 / S1×100%; Compression set increment = C2 - C1 (absolute value change).]]> Cytotoxicity The detection method is based on GB / T 16886.5-2017 "Biological Evaluation of Medical Devices - Part 5: In Vitro Cytotoxicity Tests". The extract method is used, where the test sample extract is cultured in contact with L929 mouse fibroblasts. The relative cell proliferation rate is then determined by the MTT assay, and the cytotoxicity level should not exceed grade 1. Sensitization test Refer to the detection methods in GB / T 16886.10-2017 "Biological Evaluation of Medical Devices - Part 10: Irritation and Skin Sensitization Tests". Use the guinea pig maximum dose test method, observing skin allergic reactions after intradermal injection of the test sample extract and local induction; no sensitization reaction should be observed. Intradermal reaction test Refer to the detection method in GB / T 16886.10-2017. Inject the test sample extract intradermally into both sides of the spine on the back of the rabbit, and observe the erythema and edema reaction at the injection site. The score of the intradermal reaction should not be greater than 1.0. pyrogen test Referring to the pyrogen testing method in the Pharmacopoeia of the People's Republic of China (2020 edition), the extract of the test sample is injected into the marginal ear vein of rabbits according to the dosage, and the body temperature change is observed within the specified time. It should meet the requirements of pyrogen testing. hemolysis test Refer to the detection method in GB / T 16886.4-2022 "Biological Evaluation of Medical Devices Part 4: Selection of Blood Interaction Tests". After mixing and incubating the test sample extract with rabbit anticoagulated blood, measure the amount of hemoglobin released and calculate the hemolysis rate, which should be ≤5%. Acute systemic toxicity test According to the test method in GB / T 16886.11-2021 "Biological evaluation of medical devices - Part 11: Systemic toxicity test", the test sample extract is injected into the peritoneal cavity or vein of mice once, and the poisoning manifestations and mortality rate of the animals are observed within 72 hours. There should be no acute systemic toxicity reaction.

[0055] Table 2. Basic properties of materials in the examples and comparative examples Example 1 55 9.2 620 18 Example 2 52 8.4 580 22 Example 3 58 9.5 640 16 Example 4 63 7.8 510 24 Example 5 50 8.8 550 20 Comparative Example 1 62 7.2 480 28 Comparative Example 2 56 8.1 550 26 Comparative Example 3 54 8.9 590 25 Comparative Example 4 52 6.5 420 30 Comparative Example 5 61 6.2 320 10 Comparative Example 6 55 8.5 540 21 Comparative Example 7 63 6.8 450 27 Comparative Example 8 56 7.8 530 22 Comparative Example 9 58 7.5 480 26 Comparative Example 10 54 8.0 520 23 Comparative Example 11 55 8.5 570 20

[0056] Table 3 Functional Indicators of Pistons in Examples and Comparative Examples Example 1 No leakage No air intake 3.5 3.0 Smooth and without defects Example 2 No leakage No air intake 3.7 3.2 Smooth and without defects Example 3 No leakage No air intake 3.4 2.9 Smooth and without defects Example 4 No leakage No air intake 4.4 3.7 Slight flash, slightly yellow surface Example 5 No leakage No air intake 3.3 2.8 Smooth and without defects Comparative Example 1 No leakage No air intake 4.2 3.6 Material shortage, air bubbles Comparative Example 2 No leakage No air intake 4.0 3.4 Minor flash Comparative Example 3 No leakage No air intake 4.5 3.9 Demolding and whitening Comparative Example 4 Minor leakage intake 3.9 3.3 White spots Comparative Example 5 No leakage No air intake 3.2 2.7 Smooth surface, brittle fracture during sliding Comparative Example 6 No leakage No air intake 4.3 3.7 Slightly sticky, with oil separation Comparative Example 7 No leakage No air intake 4.8 4.2 Dark yellow color change Comparative Example 8 No leakage No air intake 4.1 3.5 Surface spots, cracks Comparative Example 9 No leakage No air intake 4.0 3.4 The surface is slightly sticky and has a dull luster. Comparative Example 10 No leakage No air intake 3.9 3.3 The surface is sticky and there is obvious oil separation. Comparative Example 11 No leakage No air intake 3.8 3.2 A few white spots, uneven luster

[0057] Table 4. Process and Reliability Indicators for Examples and Comparative Examples Example 1 99.2 98.5 94 +2 Example 2 97.5 97.0 91 +3 Example 3 98.8 98.2 94 +2 Example 4 88.5 85.2 84 +4 Example 5 97.8 97.5 92 +2 Comparative Example 1 71.8 72.3 88 +4 Comparative Example 2 87.6 84.7 90 +3 Comparative Example 3 81.5 79.8 91 +3 Comparative Example 4 77.3 74.6 85 +5 Comparative Example 5 85.4 82.1 78 +8 Comparative Example 6 77.8 74.6 86 +4 Comparative Example 7 79.6 77.8 72 +6 Comparative Example 8 69.7 67.8 83 +4 Comparative Example 9 84.8 82.7 82 +5 Comparative Example 10 69.5 64.8 88 +4 Comparative Example 11 87.7 85.9 91 +3

[0058] Table 5 Biocompatibility Tests of Examples and Comparative Examples Example 1 Level 0 No allergic reaction 0.1 Compliant 0.3 No toxic reaction Example 2 Level 0 No allergic reaction 0.1 Compliant 0.4 No toxic reaction Example 3 Level 0 No allergic reaction 0.1 Compliant 0.3 No toxic reaction Example 4 Level 1 No allergic reaction 0.4 Compliant 0.8 No toxic reaction Example 5 Level 0 No allergic reaction 0.1 Compliant 0.3 No toxic reaction Comparative Example 1 Level 0 No allergic reaction 0.1 Compliant 0.4 No toxic reaction Comparative Example 2 Level 0 No allergic reaction 0.1 Compliant 0.4 No toxic reaction Comparative Example 3 Level 0 No allergic reaction 0.2 Compliant 0.3 No toxic reaction Comparative Example 4 Level 1 No allergic reaction 0.4 Compliant 1.2 No toxic reaction Comparative Example 5 Level 0 No allergic reaction 0.1 Compliant 0.5 No toxic reaction Comparative Example 6 Level 0 No allergic reaction 0.2 Compliant 0.4 No toxic reaction Comparative Example 7 Level 1 No allergic reaction 0.3 Compliant 0.9 No toxic reaction Comparative Example 8 Level 0 No allergic reaction 0.1 Compliant 0.4 No toxic reaction Comparative Example 9 Level 0 No allergic reaction 0.2 Compliant 0.5 No toxic reaction Comparative Example 10 Level 0 No allergic reaction 0.2 Compliant 0.4 No toxic reaction Comparative Example 11 Level 0 No allergic reaction 0.1 Compliant 0.4 No toxic reaction This invention systematically solves the aforementioned problems through a multi-layered synergistic design, including a SEBS and SEEPS dual elastomer composite matrix, a white oil and naphthenic oil composite for oil filling, a erucamide and silicone masterbatch composite for lubrication, an interfacial bonding between surface-activated calcium carbonate and SEBS-g-MAH, and hydrogenated petroleum resin segment confinement. The performance of Examples 1 to 3 is significantly superior to the comparative examples, exhibiting moderate hardness, high tensile strength and elongation at break, low compression set, excellent sealing and sliding performance, a smooth and defect-free appearance, high critical dimension pass rate and injection molding yield, and good performance retention after sterilization. Furthermore, in biocompatibility testing, all samples showed cytotoxicity grade 0, no sensitization reactions, intradermal reaction scores below 0.2, pyrogen tests meeting regulations, hemolysis rate below 0.5%, and no acute systemic toxicity reactions, thus meeting the biological evaluation requirements for medical pistons. Example 4 sets the dosage of all components in the independent claim to the upper limit, while setting the styrene content, molecular weight, octene content, melt index, grafting rate, kinematic viscosity of white oil and naphthenic oil, calcium carbonate mesh size, and softening point of hydrogenated petroleum resin in the dependent claims to the lower limit of their respective ranges. Test results show that this solution still possesses acceptable mechanical properties and sealing performance, with an injection molding yield of 85.2% and cytotoxicity level 1, meeting the requirement of no greater than level 1 in GB / T 16886.5-2017. This demonstrates that the invention remains practical even under the extreme conditions of highest component dosage and lowest raw material performance parameters. Example 5 sets the dosage of all components in the independent claim to the lower limit, while setting the aforementioned raw material performance parameters to the upper limit of their respective ranges. Test results show that the performance of this solution remains excellent, at the same level as Examples 1 to 3, indicating that the extreme combination of lowest component dosage and highest raw material performance parameters can also achieve the invention's objective. The above five embodiments cover the upper and lower endpoints and the middle region of the component dosage range of the independent claims, and at the same time verify the feasibility of component dosage and raw material performance parameters under the extreme conditions of reverse crossover, indicating that the parameter range defined by the claims of the present invention has sufficient experimental support.

[0059] The mechanism is as follows: SEBS and SEEPS form a fine microphase separation structure due to differences in molecular structure. During injection molding and cooling, the regular segments of SEEPS preferentially form a stable microphase separation structure, making the melt flow front smooth and suppressing flash and burrs. White oil provides anti-aging properties and processing stability, while naphthenic oil improves plasticizing efficiency and low-temperature flexibility. The combination of the two allows the material to maintain stable elastic recovery over a wide temperature range. Erucamide migrates rapidly to the surface of the product to form a lubricating film, reducing demolding resistance. Silicone masterbatch reduces shear resistance inside the melt, and the internal and external synergy completely eliminates flash. The maleic anhydride groups of SEBS-g-MAH interact strongly with the surface of activated calcium carbonate, effectively dispersing filler particles in the matrix, significantly reducing injection shrinkage and improving dimensional stability. Hydrogenated petroleum resin intersperses between the soft segments of the elastomer, restricting segment slippage and significantly reducing compression set without excessively sacrificing toughness. Under the extreme conditions of Example 4, the elastomer had a low molecular weight and low grafting rate, resulting in weakened microphase separation perfection and interfacial bonding strength, but it still maintained basic mechanical properties and sealing performance. Under the extreme conditions of Example 5, the high molecular weight elastomer with high hard segment content, combined with a compatibilizer with a high grafting rate, although the total elastomer volume was low, still formed an effective physical cross-linking network and interfacial bonding, maintaining good overall performance. The results of each example and comparative example fully verify the universality and effectiveness of the above-mentioned multiple synergistic mechanism within the scope of protection of the claims.

[0060] Compared to the examples, Comparative Example 1, due to its excessively low SEBS and excessively high SEEPS content, resulted in a SEEPS-dominated matrix, excessively high melt viscosity, and insufficient injection filling, leading to material shortages, air bubbles, and a sharp drop in yield. Conversely, if the SEBS content was too high and the SEEPS content too low, the melt was too thin, resulting in severe flash and large dimensional fluctuations. Comparative Example 2, using only white oil and omitting naphthenic oil, showed insufficient elastic recovery at low temperatures, significantly increased compression set, and the high proportion of white oil caused demolding difficulties and increased flash rate. In Comparative Example 3, the lack of erucamide and the excessive amount of silicone masterbatch resulted in a lack of rapid surface lubrication, causing whitening and deformation during piston demolding, and increasing sliding resistance due to an incomplete lubrication film. Comparative Example 4 did not use SEBS-g-MAH and the calcium carbonate was not activated. The filler and matrix were only physically mixed, failing to form a stable interfacial bond. Calcium carbonate agglomeration led to increased injection shrinkage and severe dimensional deviations. The filler agglomerates became stress concentration points, causing edge cracking during sliding and even sealing leaks. Its cytotoxicity and hemolysis rate were also slightly higher than in the examples. Comparative Example 5 used hydrogenated petroleum resin exceeding the upper limit. Although the compression set was lower, the material brittleness increased sharply, and the tensile strength and elongation at break decreased significantly. Brittle fracture occurred during sliding, failing to meet the usage requirements. Comparative Example 6 had insufficient settling time, resulting in incomplete and uneven absorption of oil, causing sticky granules, oil separation, and dimensional fluctuations. Comparative Example 7 had excessively high extrusion temperature, causing oil volatilization and decomposition of hydrogenated petroleum resin. The granules discolored, the material underwent severe thermal aging, and the mechanical properties deteriorated significantly after sterilization. The increase in compression set was the largest, and scorching occurred on the piston surface. Its cytotoxicity and hemolysis rate also increased. Comparative Example 8 had an incorrect feeding sequence; the filler was added before the lubricant, causing calcium carbonate to directly contact the elastomer without lubricant coating, forming large agglomerates. The lubricant was added late and could not be effectively dispersed, resulting in white spots on the injection-molded product surface. The agglomerates caused stress cracking, and sliding resistance fluctuated drastically. Comparative Example 9 had an excessively high pre-filling oil temperature of 105℃, disrupting the physical cross-linking network of SEBS and SEEPS. After oil filling, the elastomer particles swelled excessively, leading to a decrease in material mechanical properties, an increase in compression set to 26%, and slight stickiness on the piston surface. Comparative Example 10 had a pre-filling oil time of only 0.5 hours; the elastomer failed to fully absorb the oil, causing oil leaching, resulting in sticky granules, screw slippage, and a critical dimension pass rate dropping to 70%. Comparative Example 11 had a mixing time of only 2 minutes; the components were unevenly mixed, calcium carbonate agglomerates remained, a few spots appeared on the piston surface, and sliding resistance increased slightly and fluctuated. The above comparison fully demonstrates that the component range and process conditions defined in this invention have clear critical significance. Any deviation from any component or process parameter will lead to significant performance degradation, making it impossible to simultaneously achieve the invention's objectives of high yield, low compression set, and precise dimensional stability.

[0061] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A TPE composite material for use in medical pistons, characterized in that, By weight, it includes the following components: SEBS 15-35 portions, SEEPS 15-30 parts POE 5-20 parts 20-50 parts of white oil, 10-30 parts of naphthenic oil, PP 12-25 parts, SEBS-g-MAH 3-12 parts, 10-20 parts of surface-activated calcium carbonate, 0.1–3 parts of modified nano-silica, 1-6 parts of hydrogenated petroleum resin Antioxidant 0.1–0.8 parts, Erucamide 0.1-0.5 parts, Silicone masterbatch 0.5 to 2 parts.

2. The TPE composite material for medical pistons according to claim 1, characterized in that, The SEBS is linear SEBS with a styrene content of 25% to 35% and a number-average molecular weight of 80,000 to 200,000; the SEEPS has a styrene content of 18% to 30% and a number-average molecular weight of 100,000 to 250,000.

3. The TPE composite material for medical pistons according to claim 1, characterized in that, The POE has an octene content of 20% to 40% and a melt index of 0.5 to 10 g / 10 min.

4. The TPE composite material for medical pistons according to claim 1, characterized in that, The maleic anhydride grafting rate of the SEBS-g-MAH is 0.5% to 1.5%.

5. The TPE composite material for medical pistons according to claim 1, characterized in that, The white oil is a paraffin-based white oil with a kinematic viscosity of 40–100 mm at 40°C. 2 / s; the kinematic viscosity of the naphthenic oil at 40°C is 50–90 mm. 2 / s.

6. The TPE composite material for medical pistons according to claim 1, characterized in that, The surface-activated calcium carbonate is 1250-3000 mesh calcium carbonate that has been surface-activated with stearic acid; the modified nano silica is nano silica that has been surface-modified with a silane coupling agent to remove hydrophobicity, and its primary particle size is ≤100nm; the antioxidant is a mixture of hindered phenolic antioxidant 1010 and phosphite antioxidant 168, with a mass ratio of (1-2):

1.

7. The TPE composite material for medical pistons according to claim 1, characterized in that, The softening point of the hydrogenated petroleum resin is 100℃~130℃.

8. A method for preparing a TPE composite material for a medical piston as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Pre-fill with oil SEBS, SEEPS and POE are added to white oil and naphthenic oil and stirred and mixed at 75℃~95℃ for 1~4h. Then the mixture is taken out and left to stand for 24~96h to obtain a pre-filled oil elastomer mixture. Step 2: Ingredient Preparation The pre-filled oil elastomer mixture obtained in step one is added to a high-speed mixer in sequence with PP, SEBS-g-MAH, surface-activated calcium carbonate, modified nano silica, hydrogenated petroleum resin, antioxidant, erucamide, and silicone masterbatch according to the specified ratio. The mixture is stirred at 300-600 r / min for 10-30 min at room temperature to obtain the mixture. Step 3: Granulation The mixture described in step two is added to a twin-screw extruder and plasticized, mixed, extruded, and pelletized at 180℃~220℃ to obtain TPE composite material pellets. Step 4: Drying The TPE composite material granules described in step three are dried at 50℃~70℃ for 2~4h to obtain the TPE composite material for medical pistons.

9. The method for preparing the TPE composite material for medical pistons according to claim 8, characterized in that, In step one, the pre-filling temperature is 80℃~90℃, the pre-filling time is 2~3h, and the settling time is 24~48h.

10. The method for preparing the TPE composite material for medical pistons according to claim 8, characterized in that, In step three, the length-to-diameter ratio of the twin-screw extruder is 36:1 to 48:1, the screw speed is 200 to 400 r / min, and the residence time of the material in the twin-screw extruder is 1 to 3 min. The temperatures of each section of the extruder are set as follows: feeding section 160℃ to 180℃, melting section 180℃ to 200℃, homogenization section 200℃ to 220℃, and die head temperature 200℃ to 215℃. During granulation, water ring hot cutting or die surface hot cutting is used, and the granule shape is cylindrical or spherical with a particle size of 2 to 4 mm.