High-barrier polypropylene medical material and preparation method thereof

Abstract

The invention relates to a high-barrier polypropylene medical material and a preparation method thereof, and belongs to the technical field of high polymer materials. The medical material is prepared from the following components in percentage by weight: 2.2 to 3.5 percent of modified graphene, 0.35 to 0.4 percent of antioxidant, 0.6 to 0.8 percent of lubricant and the balance of polypropylene resin, the modified graphene induces polypropylene to generate a beta crystal extension area along the lamellar edge, an inorganic-organic barrier surface is formed, the shielding barrier effect is improved, the tortuosity degree of a permeation path is increased, and the core technical problems that large-lamellar graphene is difficult to disperse and small-lamellar graphene is difficult to form a large shielding barrier layer are solved; the beta-phase polypropylene formed at the edge of the graphene has excellent toughness, the toughness gradient of the graphene and a polypropylene matrix is weakened, the defects between interfaces are reduced, and the stability of the barrier property is improved.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a high-barrier polypropylene medical material and its preparation method. Background Technology

[0002] Polypropylene (PP) has become the preferred material for medical products such as medical device packaging, infusion containers, and surgical instrument trays due to its excellent chemical stability, biocompatibility, ease of processing, and cost-effectiveness. Its lightweight nature reduces transportation energy consumption, while its good environmental tolerance meets medical sterilization requirements such as ethylene oxide sterilization and gamma ray sterilization. However, inherent barrier defects in PP limit its application in high-end medical fields: its high oxygen permeability (OTR) and water vapor permeability (WVTR) can lead to risks such as drug oxidation and failure of the sterile barrier of instruments, especially in long-term storage or packaging of sensitive biological agents.

[0003] To improve barrier performance, traditional strategies increase the tortuosity of gas molecule permeation paths by adding layered fillers. The core mechanism follows the "tortuous path model," which shows that the higher the aspect ratio of the filler, the more significant the barrier improvement is for the same amount of filler. According to current research, graphene has an ultra-high aspect ratio (usually >1000), making it an ideal high-efficiency barrier filler.

[0004] However, the practical application of graphene faces the following technical bottlenecks: strong van der Waals forces exist between graphene sheets, resulting in poor dispersion in a polypropylene matrix, especially for large-diameter graphene with high aspect ratio. In addition, the Young's modulus of graphene differs from that of polypropylene by three orders of magnitude, leading to a toughness gradient at the interface. When the material is bent or impacted, micron-sized pores are easily generated at the interface. These defects become "high-speed channels" for gas permeation. Therefore, the permeation channels formed by these interface defects offset the advantages brought by the increase of graphene, becoming a bottleneck for the development of high-barrier polypropylene materials. Summary of the Invention

[0005] In order to solve the technical problems mentioned in the background art, the purpose of this invention is to provide a high-barrier polypropylene medical material and its preparation method.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A high-barrier polypropylene medical material, comprising: 2.2-3.5 wt% modified graphene, 0.35-0.4 wt% antioxidant, and 0.6-0.8 wt% lubricant, with the balance being polypropylene resin.

[0008] The modified graphene is prepared by the following method:

[0009] Step A1: Mix p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine and tetrahydrofuran, purge with nitrogen for protection, and stir in a water bath at 30-40℃ for 5-7 hours. Then add dicyclohexylcarbodiimide and reflux for 1.5-2.2 hours. After the reaction vessel is cooled to room temperature, add saturated sodium bicarbonate solution for washing. After separating the aqueous phase, remove residual tetrahydrofuran by rotary evaporation to obtain the modifier.

[0010] In step A1 above, the molar ratio of tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, dicyclohexylcarbodiimide, and tetrahydrofuran is 0.2 mol: 0.1 mol: 0.35-0.4 g: 0.8-1 g: 150-200 mL. The amidation reaction of tert-butylbenzoic acid and diethylenetriamine is carried out via the following reaction route:

[0011]

[0012] Step A2: Mix ethanol, p-toluenesulfonic acid and toluene, add graphene oxide and stir to disperse, then pressurize to 6-8 bar, heat to 110-120℃ and reflux for 3-4.5 h. After the reaction is completed, centrifuge, take the bottom precipitate, wash with water and dry to obtain activated graphene.

[0013] In step A2 above, the ratio of graphene oxide, ethanol, p-toluenesulfonic acid and toluene is 10g:80-100mL:0.15-0.2g:120-160mL. Carboxyl groups are enriched at the edges of the graphene oxide sheets, and ethanol is esterified with the edge carboxyl groups to introduce active ethyl ester structures into the edges of the graphene sheets.

[0014] Preferably, the graphene oxide sheet diameter is 3-15 μm. Under this sheet diameter specification, it has good dispersibility in the polypropylene matrix and is conducive to the formation of more barrier units, increasing the permeation path and ensuring good barrier properties.

[0015] Step A3: Mix the modifier, trimethylaluminum and anhydrous dimethyl sulfoxide, purge with dry nitrogen gas for protection, add activated graphene and stir to disperse, then heat to 60-80℃ and stir to react for 10-14 hours. After the reaction is complete, centrifuge to collect the bottom precipitate, wash with cyclohexane and water in sequence, and dry to obtain modified graphene.

[0016] In step A3 above, the ratio of activated graphene, modifier, trimethylaluminum and anhydrous dimethyl sulfoxide is 10g:1.3-1.7g:0.4-0.5mL:60-80mL. The modifier undergoes an amino-ester exchange reaction with the active ethyl ester introduced at the edge of the activated graphene sheet, and aromatic amide is grafted onto the edge of the graphene sheet for modification.

[0017] Preferably, the antioxidant is a combination of antioxidant 1010 and antioxidant DLTP, which has stable anti-migration and thermal stability, meeting the requirements for medical safety.

[0018] Preferably, the lubricant is calcium stearate, which has a stable lubricating effect, high biocompatibility, and meets medical safety requirements.

[0019] A method for preparing a high-barrier polypropylene medical material specifically involves: mixing the raw materials of each component evenly, and then using a twin-screw extruder for melt extrusion granulation to obtain the high-barrier polypropylene medical material.

[0020] The beneficial effects of this invention are:

[0021] This invention utilizes the characteristic that the edges of graphene oxide sheets are rich in carboxyl groups. Esterification of graphene oxide with ethanol produces activated graphene. Highly active ethyl esters with specific reactivity are formed at the edges for activation. Modifiers are prepared by amidation reaction of p-tert-butylbenzoic acid and diethylenetriamine. Finally, the modifier undergoes an amino-ester exchange reaction with the ethyl ester structure at the edges of the activated graphene sheets to produce modified graphene. Compared with existing technologies, the modified graphene edge grafted with an aromatic amide containing tert-butyl groups has a chemical structure where the terminal tert-butyl group and the methyl side chain on the polypropylene main chain are both saturated alkyl structures with similar polarity. This reduces the interfacial energy difference between the graphene sheets and the polypropylene matrix, increasing compatibility and dispersibility. The steric hindrance effect of the tert-butyl group interferes with the regular arrangement of the polypropylene molecular chains. Combined with the aromatic amide structure, it induces the formation of β-phase crystals along the graphene sheet edge of the polypropylene. On the one hand, it forms an inorganic-organic barrier surface of "graphene-β-crystal extension region" in the polypropylene matrix, increasing the shielding effect and the tortuosity of the penetration path. This solves the core technical problems of the difficulty in dispersing large-sheet graphene and the difficulty in forming large shielding barrier layers with small-diameter graphene. On the other hand, the β-phase polypropylene formed at the graphene edge has excellent toughness, weakening the toughness gradient between the graphene and the polypropylene matrix, reducing interfacial defects, and improving the stability of the barrier performance. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1: Preparation of high-barrier polypropylene medical material. The specific implementation process is as follows:

[0024] (1) Preparation of modified graphene

[0025] Step A1: Mix p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, and tetrahydrofuran, purge with nitrogen for protection, and stir in a water bath at 30°C for 7 hours. Then add dicyclohexylcarbodiimide and reflux for 2.2 hours. The ratio of p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, dicyclohexylcarbodiimide, and tetrahydrofuran is 0.2 mol: 0.1 mol: 0.35 g: 0.8 g: 150 mL. After the reaction vessel is cooled to room temperature, add saturated sodium bicarbonate solution to wash the mixture. After separating the aqueous phase, remove the residual tetrahydrofuran by rotary evaporation to obtain the modifier.

[0026] Step A2: Mix ethanol, p-toluenesulfonic acid, and toluene, add graphene oxide and stir to disperse. Then pressurize with nitrogen to 6 bar and reflux at 110°C for 4.5 h. The graphene oxide is a commercially available raw material with an average sheet diameter of 10 μm and a sheet diameter distribution of 3-12 μm. The ratio of graphene oxide, ethanol, p-toluenesulfonic acid, and toluene is 10 g: 80 mL: 0.15 g: 120 mL. After the reaction is complete, centrifuge, take the bottom precipitate, wash with water and dry to obtain activated graphene.

[0027] Step A3: Mix the modifier, trimethylaluminum and anhydrous dimethyl sulfoxide, purge with dry nitrogen for protection, add activated graphene and stir to disperse, then heat to 60℃ and stir to react for 14h. The ratio of activated graphene, modifier, trimethylaluminum and anhydrous dimethyl sulfoxide is 10g:1.3g:0.4mL:60mL. After the reaction is complete, centrifuge to collect the bottom precipitate, wash with cyclohexane and water in sequence, and dry to obtain modified graphene.

[0028] (2) Mixing and granulation

[0029] The raw materials are calculated by weight percentage as follows: 2.2 wt% modified graphene, which is self-made in this embodiment; 0.4 wt% antioxidant, which is a compound of antioxidant 1010 and antioxidant DLTP in a weight ratio of 2:1; 0.6 wt% lubricant, which is medical grade calcium stearate; and the balance is polypropylene resin, which is M800E type resin raw material.

[0030] The raw materials of each component are added to a high-speed mixer and mixed at 600 rpm for 10 minutes. The mixture is then fed into a twin-screw extruder, melted and mixed at 200°C, and extruded and granulated to obtain high-barrier polypropylene medical material.

[0031] Example 2: Preparation of high-barrier polypropylene medical material. The specific implementation process is as follows:

[0032] (1) Preparation of modified graphene

[0033] Step A1: Mix p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, and tetrahydrofuran, purge with nitrogen for protection, and stir in a water bath at 40°C for 5 hours. Then add dicyclohexylcarbodiimide and reflux for 1.5 hours. The ratio of p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, dicyclohexylcarbodiimide, and tetrahydrofuran is 0.2 mol: 0.1 mol: 0.4 g: 1 g: 200 mL. After the reaction vessel is cooled to room temperature, add saturated sodium bicarbonate solution to wash the mixture. After separating the aqueous phase, remove the residual tetrahydrofuran by rotary evaporation to obtain the modifier.

[0034] Step A2: Mix ethanol, p-toluenesulfonic acid, and toluene, add graphene oxide and stir to disperse. Then pressurize with nitrogen to 8 bar and reflux at 1120℃ for 3 hours. The graphene oxide is a commercially available raw material with an average sheet diameter of 10 μm and a sheet diameter distribution of 3-12 μm. The ratio of graphene oxide, ethanol, p-toluenesulfonic acid, and toluene is 10 g: 100 mL: 0.2 g: 160 mL. After the reaction is complete, centrifuge, take the bottom precipitate, wash with water and dry to obtain activated graphene.

[0035] Step A3: Mix the modifier, trimethylaluminum and anhydrous dimethyl sulfoxide, purge with dry nitrogen for protection, add activated graphene and stir to disperse, then heat to 80℃ and stir to react for 10h. The ratio of activated graphene, modifier, trimethylaluminum and anhydrous dimethyl sulfoxide is 10g:1.7g:0.5mL:80mL. After the reaction is complete, centrifuge to collect the bottom precipitate, wash with cyclohexane and water in sequence, and dry to obtain modified graphene.

[0036] (2) Mixing and granulation

[0037] The raw materials are calculated by weight percentage as follows: 3.5 wt% modified graphene, which is self-made in this embodiment; 0.35 wt% antioxidant, which is a compound of antioxidant 1010 and antioxidant DLTP in a weight ratio of 2:1; 0.8 wt% lubricant, which is medical grade calcium stearate; and the balance is polypropylene resin, which is M800E type resin raw material.

[0038] The raw materials of each component are added to a high-speed mixer and mixed at 600 rpm for 10 minutes. The mixture is then fed into a twin-screw extruder, melted and mixed at 200°C, and extruded and granulated to obtain high-barrier polypropylene medical material.

[0039] Example 3: Preparation of high-barrier polypropylene medical material. The specific implementation process is as follows:

[0040] (1) Preparation of modified graphene

[0041] Step A1: Mix p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, and tetrahydrofuran, purge with nitrogen for protection, and stir in a water bath at 35°C for 6 hours. Then add dicyclohexylcarbodiimide and reflux for 2 hours. The ratio of p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, dicyclohexylcarbodiimide, and tetrahydrofuran is 0.2 mol: 0.1 mol: 0.35 g: 0.9 g: 170 mL. After the reaction vessel is cooled to room temperature, add saturated sodium bicarbonate solution to wash the mixture. After separating the aqueous phase, remove the residual tetrahydrofuran by rotary evaporation to obtain the modifier.

[0042] Step A2: Mix ethanol, p-toluenesulfonic acid and toluene, add graphene oxide and stir to disperse. Then pressurize with nitrogen to 7 bar and reflux at 115°C for 4 hours. The graphene oxide is a commercially available raw material with an average sheet diameter of 10 μm and a sheet diameter distribution of 3-12 μm. The ratio of graphene oxide, ethanol, p-toluenesulfonic acid and toluene is 10 g: 90 mL: 0.18 g: 140 mL. After the reaction is complete, centrifuge, take the bottom precipitate, wash with water and dry to obtain activated graphene.

[0043] Step A3: Mix the modifier, trimethylaluminum and anhydrous dimethyl sulfoxide, purge with dry nitrogen for protection, add activated graphene and stir to disperse, then heat to 70℃ and stir to react for 12 hours. The ratio of activated graphene, modifier, trimethylaluminum and anhydrous dimethyl sulfoxide is 10g:1.5g:0.5mL:70mL. After the reaction is complete, centrifuge to collect the bottom precipitate, wash with cyclohexane and water in sequence, and dry to obtain modified graphene.

[0044] (2) Mixing and granulation

[0045] The raw materials are calculated by weight percentage: 3 wt% modified graphene, which is self-made in this embodiment; 0.4 wt% antioxidant, which is a compound of antioxidant 1010 and antioxidant DLTP in a weight ratio of 2:1; 0.7 wt% lubricant, which is medical grade calcium stearate; and the balance is polypropylene resin, which is M800E type resin raw material.

[0046] The raw materials of each component are added to a high-speed mixer and mixed at 600 rpm for 10 minutes. The mixture is then fed into a twin-screw extruder, melted and mixed at 200°C, and extruded and granulated to obtain high-barrier polypropylene medical material.

[0047] Example 4: Preparation of high-barrier polypropylene medical material. The specific implementation process is as follows:

[0048] (1) Preparation of modified graphene

[0049] Step A1: Mix p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, and tetrahydrofuran, purge with nitrogen for protection, and stir in a water bath at 40°C for 5.5 h. Then add dicyclohexylcarbodiimide and reflux for 1.8 h. The ratio of p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, dicyclohexylcarbodiimide, and tetrahydrofuran is 0.2 mol: 0.1 mol: 0.35 g: 0.9 g: 180 mL. After the reaction vessel is cooled to room temperature, add saturated sodium bicarbonate solution to wash the mixture. After separating the aqueous phase, remove the residual tetrahydrofuran by rotary evaporation to obtain the modifier.

[0050] Step A2: Mix ethanol, p-toluenesulfonic acid, and toluene, add graphene oxide and stir to disperse. Then pressurize with nitrogen to 8 bar and reflux at 120°C for 3.5 h. The graphene oxide is a commercially available raw material with an average sheet diameter of 10 μm and a sheet diameter distribution of 3-12 μm. The ratio of graphene oxide, ethanol, p-toluenesulfonic acid, and toluene is 10 g: 100 mL: 0.17 g: 150 mL. After the reaction is complete, centrifuge, take the bottom precipitate, wash with water and dry to obtain activated graphene.

[0051] Step A3: Mix the modifier, trimethylaluminum and anhydrous dimethyl sulfoxide, purge with dry nitrogen for protection, add activated graphene and stir to disperse, then heat to 75℃ and stir to react for 11 hours. The ratio of activated graphene, modifier, trimethylaluminum and anhydrous dimethyl sulfoxide is 10g:1.6g:0.5mL:80mL. After the reaction is complete, centrifuge to collect the bottom precipitate, wash with cyclohexane and water in sequence, and dry to obtain modified graphene.

[0052] (2) Mixing and granulation

[0053] The raw materials are calculated by weight percentage as follows: 2.8 wt% modified graphene, which is self-made in this embodiment; 0.4 wt% antioxidant, which is a compound of antioxidant 1010 and antioxidant DLTP in a weight ratio of 2:1; 0.7 wt% lubricant, which is medical grade calcium stearate; and the balance is polypropylene resin, which is M800E type resin raw material.

[0054] The raw materials of each component are added to a high-speed mixer and mixed at 600 rpm for 10 minutes. The mixture is then fed into a twin-screw extruder, melted and mixed at 200°C, and extruded and granulated to obtain high-barrier polypropylene medical material.

[0055] Comparative Example 1: This comparative example is a blank control. It is the same as Example 4, but without the addition of modified graphene. The rest of the implementation process is exactly the same.

[0056] Comparative Example 2 used 2.5 wt% coupled graphene and 0.3 wt% WBG-II type β nucleating agent to replace the modified graphene, with the rest of the implementation process being exactly the same.

[0057] The material prepared above was injection molded into a 1 mm thick sheet sample. Tensile properties were tested according to ASTM D638-2022, impact properties according to ASTM D256-2024, and oxygen transmission rate according to ASTM D3985-2024. The reduction rate of oxygen transmission rate (OTR) was calculated using Comparative Example 1 as a reference. Water vapor transmission rate was tested according to ASTM F1249-2020, and the reduction rate of water vapor transmission rate (WVTR) was calculated using Comparative Example 1 as a reference. The sample was then subjected to 20 90° bends according to ASTM D2176-2016, and the oxygen transmission rate was tested again, and the change rate of oxygen transmission rate (OTR) was calculated. The specific test results are shown in Table 1.

[0058] Table 1

[0059]

[0060] As shown in Table 1, the tensile strength and impact strength of the polypropylene medical material in the embodiment are higher than those in the comparative example, indicating that the introduction of modified graphene has a lower impact on the mechanical properties of the matrix. In the barrier test, the permeability reduction rate of the embodiment is higher than that of the comparative example, especially the oxygen permeability reduction rate is significantly increased, showing excellent barrier performance. Moreover, the embodiment has extremely high stability under external force deformation.

[0061] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0062] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A high-barrier polypropylene medical material, characterized in that, The specific components are: 2.2-3.5 wt% modified graphene, 0.35-0.4 wt% antioxidant, and 0.6-0.8 wt% lubricant, with the balance being polypropylene resin; The modified graphene is prepared by the following method: Step A1: Mix p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine and tetrahydrofuran, purge with nitrogen for protection, stir and react in a water bath at 30-40℃ for 5-7 hours, then add dicyclohexylcarbodiimide and reflux for 1.5-2.2 hours to prepare the modifier. Step A2: Mix ethanol, p-toluenesulfonic acid and toluene, add graphene oxide and stir to disperse, then pressurize to 6-8 bar, heat to 110-120℃ and reflux for 3-4.5 h to prepare activated graphene; Step A3: Mix the modifier, trimethylaluminum and anhydrous dimethyl sulfoxide, purge with dry nitrogen gas for protection, add activated graphene and stir to disperse, then heat to 60-80℃ and stir to react for 10-14 hours to prepare modified graphene.

2. The high-barrier polypropylene medical material according to claim 1, characterized in that, The ratio of p-tert-butylbenzoic acid, diethylenetriamine, 4-dimethylaminopyridine, dicyclohexylcarbodiimide and tetrahydrofuran is 0.2mol:0.1mol:0.35-0.4g:0.8-1g:150-200mL.

3. The high-barrier polypropylene medical material according to claim 2, characterized in that, The ratio of graphene oxide, ethanol, p-toluenesulfonic acid and toluene is 10g: 80-100mL: 0.15-0.2g: 120-160mL.

4. The high-barrier polypropylene medical material according to claim 3, characterized in that, The sheet diameter of graphene oxide is 3-15 μm.

5. A high-barrier polypropylene medical material according to claim 4, characterized in that, The ratio of activated graphene, modifier, trimethylaluminum and anhydrous dimethyl sulfoxide is 10g: 1.3-1.7g: 0.4-0.5mL: 60-80mL.

6. The high-barrier polypropylene medical material according to claim 1, characterized in that, The antioxidant is a combination of antioxidant 1010 and antioxidant DLTP.

7. The high-barrier polypropylene medical material according to claim 1, characterized in that, The lubricant is calcium stearate.

8. A method for preparing a high-barrier polypropylene medical material according to any one of claims 1-7, characterized in that, Specifically, the raw materials are mixed evenly, and then melt-extruded and granulated using a twin-screw extruder to obtain high-barrier polypropylene medical materials.

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