A medical grade polypropylene color master batch resistant to gamma radiation discoloration and a preparation method thereof

Abstract

This application relates to the field of polypropylene masterbatch processing technology, and more specifically, to a medical-grade polypropylene masterbatch resistant to gamma-ray radiation color change and its preparation method. It is prepared from the following raw materials in parts by weight: 40-80 parts polypropylene carrier resin, 5-10 parts radiation-resistant composite stabilizer, 3-5 parts dispersant, 1-2 parts processing aid, and 0-5 parts pigment. The radiation-resistant composite stabilizer is composed of a non-phenolic antioxidant, an N-alkoxy hindered amine light stabilizer, and a crystallization regulator. The non-phenolic antioxidant is a benzofuranone compound and / or a hydroxylamine compound. The crystallization regulator is at least one of a sorbitol nucleating agent, liquid paraffin, and low molecular weight polyolefin wax. This formulation can improve the color stability and mechanical property retention of medical polypropylene products, prevent embrittlement during storage, and meet the stringent requirements of medical devices for high transparency, high toughness, and long-term storage stability.

Description

Technical Field

[0001] This application relates to the field of polypropylene masterbatch processing technology, and more specifically, to a medical-grade polypropylene masterbatch resistant to gamma-ray radiation color change and its preparation method. Background Technology

[0002] Polypropylene resin, due to its excellent chemical resistance, good mechanical properties, ease of processing and molding, and relatively low cost, has become the preferred material for manufacturing disposable medical devices and laboratory consumables, such as syringes, centrifuge tubes, microtiter plates, and cell culture dishes. To ensure medical safety and prevent cross-infection, these products must undergo rigorous terminal sterilization before leaving the factory.

[0003] Currently, industrial sterilization methods for medical devices mainly include ethylene oxide sterilization, moist heat steam sterilization, and radiation sterilization. Among these, ethylene oxide sterilization is facing increasingly stringent regulations due to the presence of toxic chemical residues (such as ethylene oxide itself and its metabolite ethylene glycol) and a desorption cycle that can take several days or even weeks. Steam sterilization is unsuitable for materials sensitive to moisture and heat, and for pre-packaged products. In contrast, gamma-ray radiation sterilization technology based on a cobalt-60 radioactive source has become one of the mainstream sterilization methods for disposable medical plastic products due to its advantages such as high sterilization efficiency, broad bactericidal spectrum, no chemical residues, strong penetration, and the ability to process products in completely sealed packaging, effectively avoiding secondary contamination.

[0004] However, polypropylene resin, as a semi-crystalline olefin polymer, contains a large number of tertiary carbon atoms in its molecular chain backbone, which are extremely sensitive to high-energy radiation. During gamma-ray irradiation, complex free radical reactions occur in the polymer molecular chains, mainly including random chain breakage and cross-linking reactions, accompanied by the generation of a large number of highly reactive, long-lived free radicals. This leads to a "post-radiation effect" in polypropylene resin products after radiation sterilization, meaning that products after irradiation are prone to yellowing and deterioration of mechanical properties. To inhibit the thermal oxidative degradation of polypropylene resin during high-temperature processing and long-term storage, existing technologies generally employ a stabilizing system of hindered phenolic primary antioxidants combined with phosphite secondary antioxidants. Hindered phenolic molecules are easily oxidized into quinone-like structures and other strongly chromogenic groups, causing irreversible yellowing of products during irradiation or during post-irradiation storage. The chain-breaking reaction induced by gamma rays reduces the weight-average molecular weight of polypropylene resin, increases the molecular weight distribution width, and destroys its crystal integrity, leading to a sharp decline in toughness indicators such as tensile strength and elongation at break, and causing the products to become brittle. Summary of the Invention

[0005] To address the issues of yellowing and mechanical property degradation in polypropylene resin after radiation sterilization, this application provides a medical-grade polypropylene masterbatch resistant to γ-ray radiation discoloration and its preparation method.

[0006] In a first aspect, this application provides a medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration, employing the following technical solution: A medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration is prepared from the following raw materials in parts by weight: 40-80 parts of polypropylene carrier resin 5-10 parts of radiation-resistant composite stabilizer 3-5 parts dispersant 1-2 parts of processing aid 0-5 parts of pigment; The radiation-resistant composite stabilizer is composed of a non-phenolic antioxidant, an N-alkoxy hindered amine light stabilizer, and a crystallization regulator. The non-phenolic antioxidants are benzofuranone compounds and / or hydroxylamine compounds; The crystallization regulator is at least one of sorbitol nucleating agents, liquid paraffin, and low molecular weight polyolefin wax.

[0007] By adopting the above technical solution, and replacing traditional hindered phenolic compounds with benzofuranone and / or hydroxylamine non-phenolic antioxidants, irreversible yellowing caused by the oxidation of phenols to quinone chromophores during radiation sterilization is avoided. Simultaneously, N-alkoxy hindered amine light stabilizers efficiently capture highly active, long-lived free radicals generated by gamma-ray irradiation, inhibiting random chain breakage and oxidative degradation of polypropylene molecules, effectively solving the "post-radiation effect" after radiation sterilization. Combined with the optimization and repair effect of crystallization regulators on the crystal morphology and integrity of polypropylene, this masterbatch, while ensuring efficient radiation sterilization, can improve the color stability and mechanical property retention of medical polypropylene products, prevent embrittlement during storage, and meet the stringent requirements of medical devices for high transparency, high toughness, and long-term storage stability.

[0008] In this application, a non-phenolic antioxidant and an N-alkoxy hindered amine light stabilizer form a synergistic stabilizing system. The former interrupts the oxidation chain reaction through a non-phenolic antioxidant mechanism without producing colored products, while the latter inhibits molecular chain degradation and oxidation reactions by capturing free radicals. Together, they block yellowing and mechanical degradation at the source. The crystallization regulator optimizes the crystallization behavior of polypropylene and repairs the crystalline structure of radiation-damaged regions, compensating for irradiation-induced crystallization defects and maintaining the tensile strength and elongation at break of the material. The dispersant and processing aid ensure that the radiation-resistant composite stabilizer is uniformly dispersed in the polypropylene carrier resin and improves processing fluidity. The pigment provides the necessary color marking function. The synergistic effect of the components enables the masterbatch to impart excellent gamma-ray radiation resistance and medical safety to the product while giving it the target color.

[0009] Preferably, the weight ratio of the non-phenolic antioxidant, the N-alkoxy hindered amine light stabilizer, and the crystallization regulator is (1-2):(2-4):3.

[0010] By adopting the above technical solution, the relatively high proportion of N-alkoxy hindered amine light stabilizer ensures that a large number of long-lived free radicals generated by γ-ray irradiation are fully captured. The non-phenolic antioxidants work synergistically in an appropriate proportion to effectively interrupt the oxidation chain reaction without producing colored products, avoiding the cost increase and potential migration risks caused by excessive addition. At the same time, the crystallization regulator, with a relatively dominant proportion of 3 parts, fully repairs and improves the polypropylene crystal structure damaged by irradiation, making up for the crystallization defects caused by molecular chain breakage. Thus, while ensuring excellent color stability, it maximizes the restoration and maintenance of the material's toughness and mechanical strength, allowing the three to exert the best synergistic effect, avoiding the decrease in processing fluidity or compatibility problems caused by excessive amount of a single component, ensuring that the color masterbatch is uniformly dispersed during melt processing and giving the product long-term storage stability.

[0011] Preferably, the non-phenolic antioxidant is composed of methyl 5-formyl-3,4-dihydro-2,2-dimethyl-2H-benzofuran-7-carboxylic acid and N,N-bis(octadecyl)hydroxylamine in a mass ratio of 1:(1.5-3).

[0012] By employing the above technical solution, methyl 5-formyl-3,4-dihydro-2,2-dimethyl-2H-benzofuran-7-carboxylic acid efficiently scavenges alkyl free radicals and interrupts the oxidation chain reaction through hydrogen transfer reaction of the lactone ring. N,N-di(octadecyl)hydroxylamine, with its long-chain alkyl structure (octadecyl), exhibits excellent compatibility with the polypropylene matrix and exerts a synergistic antioxidant effect by capturing peroxide free radicals and stabilizing alkyl free radicals. The appropriate excess of hydroxylamine at this ratio ensures the timely capture of a large number of free radicals in the early stages of gamma-ray irradiation, while benzofuranones continuously provide long-lasting thermo-oxidative stability. The combined effect of these two compounds not only completely avoids the yellowing problem caused by the oxidation of colored quinone structures by traditional phenolic antioxidants, but also effectively inhibits the breakage and cross-linking of polypropylene molecular chains during radiation sterilization, reducing the oxidation induction period during post-irradiation storage. This results in excellent color stability, mechanical property retention, and long-term storage safety for medical polypropylene products.

[0013] Preferably, the N-alkoxy hindered amine light stabilizer is bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate.

[0014] By adopting the above technical solution, the 1-octyloxy substituent in its molecular structure endows it with excellent compatibility with polypropylene carrier resin, and the long-chain structure of sebacic acid ester further enhances its dispersion stability in polyolefin matrix. This alkoxy-substituted hindered amine exhibits a more stable free radical scavenging ability than traditional hindered amines under gamma irradiation. Its N-alkoxy structure can effectively inhibit radiation-induced alkyl free radicals and peroxy free radicals, blocking the oxidative degradation and cross-linking reaction of polypropylene molecular chains, while avoiding its own conversion into colored products during irradiation. When synergistically used with benzofuranone and hydroxylamine non-phenolic antioxidants, this light stabilizer can greatly prolong the oxidation induction period of polypropylene, effectively alleviating the "post-radiation effect" after radiation sterilization, thereby ensuring that medical polypropylene products maintain excellent color transparency, impact toughness and elongation at break during long-term storage, meeting the stringent requirements of medical devices for radiation sterilization stability and safety of use.

[0015] Preferably, the crystallization regulator is composed of sorbitol nucleating agent, liquid paraffin and low molecular weight polyolefin wax, and the weight ratio of the three is (2-4):1:(1-2).

[0016] By adopting the above technical solutions, sorbitol-based nucleating agents provide high-density heterogeneous nucleation centers in a relatively dominant proportion, further refining the size of polypropylene spherulites, improving the crystallization rate and crystallinity, and effectively repairing lattice defects and spherulite integrity damage caused by gamma-ray irradiation. Liquid paraffin, as a dispersion carrier and lubricant, ensures that the nucleating agent is uniformly dispersed in the polypropylene melt and reduces processing torque, improving melt flowability. Low molecular weight polyolefin wax, with its excellent compatibility with the polypropylene matrix due to its long-chain alkane structure, forms a flexible transition layer at the crystal interface, inhibiting wafer thickening and increased brittleness after irradiation. The synergistic effect of the three not only effectively restores the crystal regularity and mechanical toughness of polypropylene after radiation sterilization, but also improves the surface gloss and dimensional stability of the product, avoids post-shrinkage and embrittlement caused by incomplete crystallization, and ensures that medical polypropylene products maintain excellent strength, transparency, and reliability during long-term storage.

[0017] Preferably, the polypropylene carrier resin is homopolymer polypropylene with a melt index of 20-50 g / 10 min at 230℃ / 2.16 kg.

[0018] By adopting the above technical solutions, it is ensured that the masterbatch has good plasticizing fluidity and shear dispersion ability during melt processing, so that functional components such as radiation-resistant composite stabilizers and pigments can be uniformly dispersed in the polypropylene matrix without agglomeration defects. At the same time, it can meet the mold filling requirements of thin-walled, precision and complex structures of medical devices in the injection molding stage. Meanwhile, the homopolymer polypropylene at this molecular weight level has suitable crystallization ability and melt strength, which helps to maintain the dimensional stability and rigidity of the product. Ultimately, it is ensured that the masterbatch can give the product radiation resistance and coloring function without damaging the inherent mechanical properties and processing performance of medical polypropylene materials.

[0019] Preferably, the dispersant comprises at least one of polyethylene wax, oxidized polyethylene wax, ethylene bis-stearamide, and ethylene bis-oleamide.

[0020] By adopting the above technical solutions, the melt viscosity is effectively reduced and the processing fluidity is improved, ensuring that functional components such as radiation-resistant composite stabilizers and pigments are uniformly dispersed and free from agglomeration during the melt mixing process, thus preventing mechanical property deterioration and color difference problems caused by uneven dispersion.

[0021] Preferably, the processing aid includes at least one of calcium stearate, zinc stearate, magnesium stearate, polyether-modified silicone oil, and silicone masterbatch.

[0022] By adopting the above technical solutions, the friction coefficient between the melt and the processing equipment is reduced, preventing melt fracture and sticking to the mold, and improving the mold filling capacity and demolding performance during injection molding. At the same time, it effectively reduces processing torque and equipment wear, improves production efficiency and product surface finish, and the additive system has good compatibility with radiation-resistant composite stabilizers, does not interfere with antioxidant and crystallization repair functions, and ensures that the color masterbatch, while giving the product excellent processing performance, maintains its gamma-ray radiation resistance stability and medical safety.

[0023] Secondly, this application provides a method for preparing medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration, employing the following technical solution: A method for preparing a medical-grade polypropylene masterbatch resistant to gamma-ray radiation color change includes the following preparation steps: S1. Mix polypropylene carrier resin, radiation-resistant composite stabilizer, dispersant, processing aid and pigment to obtain a mixture; S2. The mixture is melt-blended, extruded and granulated to obtain medical-grade polypropylene masterbatch resistant to γ-ray radiation discoloration.

[0024] By adopting the above technical solution, the uniform premixing in step S1 ensures the initial dispersion of each functional component, avoiding local agglomeration or concentration deviation, and laying the foundation for subsequent melt processing. In step S2, the radiation-resistant composite stabilizer, dispersant, etc. are uniformly dispersed in the polypropylene carrier resin under high shear and fully plasticized through melt blending. Finally, the color masterbatch product with uniform particle size and excellent flowability is obtained by extrusion granulation. This process route is simple, efficient, highly controllable, and easy to scale up for industrial production. It can effectively retain the efficacy of radiation-resistant active components such as non-phenolic antioxidants and N-alkoxy hindered amine light stabilizers, ensuring that the color masterbatch can give medical polypropylene products the target color while achieving excellent gamma-ray radiation resistance and long-term storage safety.

[0025] Preferably, in step S2, a twin-screw extruder is used for melt blending and granulation, with a screw speed of 200-400 r / min, a melt temperature of 170-190℃, and a residence time of 1.5-2.5 min.

[0026] By adopting the above technical solution, the high shear mixing capacity of twin-screw extruders is used to achieve uniform dispersion and full plasticization of functional components such as radiation-resistant composite stabilizers and pigments in a polypropylene carrier. At the same time, this dwell process effectively avoids the thermal decomposition or efficacy loss of non-phenolic antioxidants and N-alkoxy hindered amine light stabilizers at high temperatures, prevents thermal oxidative degradation of the polypropylene carrier resin, and ensures that the structural integrity and synergistic effect of the radiation-resistant active components are fully preserved. Ultimately, medical-grade masterbatches with uniform dispersion, stable color, and excellent processing fluidity are obtained, meeting the stringent requirements of medical devices for material purity and performance stability.

[0027] In summary, this application has the following beneficial effects: This application fundamentally solves the irreversible yellowing problem caused by the oxidation of quinone chromophores by traditional hindered phenolic antioxidants through the synergistic combination of non-phenolic antioxidants and N-alkoxy hindered amine light stabilizers. Simultaneously, it efficiently captures highly reactive, long-lived free radicals generated by gamma-ray irradiation, inhibiting the breakage and oxidative degradation of polypropylene molecular chains and effectively eliminating the "post-radiation effect." Combined with crystallization regulators to repair irradiation-damaged crystalline regions and optimize crystal morphology, it significantly improves the color stability, transparency, and mechanical property retention of the product, preventing embrittlement during long-term storage. The components of this masterbatch system exhibit good compatibility and uniform dispersion, resulting in excellent processing performance. While ensuring efficient radiation sterilization without chemical residues, it endows medical polypropylene products with excellent long-term storage stability and safety, meeting the comprehensive requirements of medical devices for high transparency, high toughness, and stringent sterilization standards. Detailed Implementation Example

[0028] The liquid paraffin is a product of Hailujiahe, model number P-350.

[0029] The low molecular weight polyolefin wax is a Clariant product, model number Licocene PP 6102.

[0030] The pigment is titanium dioxide. The polyethylene wax is a Euroceras product, model number CERALENE 2E.

[0031] Oxidized polyethylene wax is a product of Jiabote, model number J-616A. Example 1

[0032] A medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration is prepared by the following method: S1. Mix 400g of polypropylene carrier resin, 50g of radiation-resistant composite stabilizer, 30g of dispersant (polyethylene wax), 10g of processing aid (calcium stearate) and 0g of pigment to obtain a mixture; The polypropylene carrier resin is homopolymer polypropylene, with a melt index of 20 g / 10 min at 230℃ / 2.16 kg. The radiation-resistant composite stabilizer consists of a non-phenolic antioxidant, an N-alkoxy hindered amine light stabilizer (bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate), and a crystallization regulator, with a weight ratio of 1:2:3. The non-phenolic antioxidant is composed of methyl 5-formyl-3,4-dihydro-2,2-dimethyl-2H-benzofuran-7-carboxylate and N,N-di(octadecyl)hydroxylamine in a mass ratio of 1:1.5. The crystallization regulator is composed of sorbitol nucleating agent (2,4-bis(3,4-dimethylbenzyl)sorbitol), liquid paraffin and low molecular weight polyolefin wax, and the weight ratio of the three is 2:1:1; S2. The mixture is melt-blended, extruded and granulated to obtain medical-grade polypropylene masterbatch resistant to γ-ray radiation discoloration. In step S2, a twin-screw extruder is used for melt blending and granulation. The screw speed is 200 r / min, the melt temperature is 170℃, and the residence time is 1.5 min.

[0033] Example 2 A medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration is prepared by the following method: S1. Mix 600g of polypropylene carrier resin, 80g of radiation-resistant composite stabilizer, 40g of dispersant (oxidized polyethylene wax), 15g of processing aid (zinc stearate) and 30g of pigment to obtain a mixture; The polypropylene carrier resin is homopolymer polypropylene, with a melt index of 35 g / 10 min at 230℃ / 2.16 kg. The radiation-resistant composite stabilizer consists of a non-phenolic antioxidant, an N-alkoxy hindered amine light stabilizer (bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate), and a crystallization regulator. The weight ratio of the non-phenolic antioxidant, the N-alkoxy hindered amine light stabilizer (bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate), and the crystallization regulator is 1.5:3:3. The non-phenolic antioxidant is composed of methyl 5-formyl-3,4-dihydro-2,2-dimethyl-2H-benzofuran-7-carboxylic acid and N,N-di(octadecyl)hydroxylamine in a mass ratio of 1:2.5. The crystallization regulator is composed of sorbitol nucleating agent (2,4-bis(3,4-dimethylbenzyl)sorbitol), liquid paraffin and low molecular weight polyolefin wax, and the weight ratio of the three is 3:1:1.5; S2. The mixture is melt-blended, extruded and granulated to obtain medical-grade polypropylene masterbatch resistant to γ-ray radiation discoloration. In step S2, a twin-screw extruder is used for melt blending and granulation. The screw speed is 300 r / min, the melt temperature is 180℃, and the residence time is 2 min.

[0034] Example 3 A medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration is prepared by the following method: S1. Mix 800g of polypropylene carrier resin, 100g of radiation-resistant composite stabilizer, 50g of dispersant (ethylene bis-stearamide), 20g of processing aid (magnesium stearate) and 50g of pigment to obtain a mixture; The polypropylene carrier resin is homopolymer polypropylene, with a melt index of 50 g / 10 min at 230℃ / 2.16 kg. The radiation-resistant composite stabilizer consists of a non-phenolic antioxidant, an N-alkoxy hindered amine light stabilizer (bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate), and a crystallization regulator, with a weight ratio of 2:4:3. The non-phenolic antioxidant is composed of methyl 5-formyl-3,4-dihydro-2,2-dimethyl-2H-benzofuran-7-carboxylate and N,N-di(octadecyl)hydroxylamine in a mass ratio of 1:3. The crystallization regulator is composed of sorbitol nucleating agent (2,4-bis(3,4-dimethylbenzyl)sorbitol), liquid paraffin and low molecular weight polyolefin wax, and the weight ratio of the three is 4:1:2; S2. The mixture is melt-blended, extruded and granulated to obtain medical-grade polypropylene masterbatch resistant to γ-ray radiation discoloration. In step S2, a twin-screw extruder is used for melt blending and granulation. The screw speed is 400 r / min, the melt temperature is 190℃, and the residence time is 2.5 min.

[0035] Example 4 A medical-grade polypropylene masterbatch resistant to γ-ray radiation color change. The difference between this embodiment and Example 1 is that the weight ratio of non-phenolic antioxidant, N-alkoxy hindered amine light stabilizer (bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate) and crystallization regulator is 3:2:3.

[0036] Example 5 A medical-grade polypropylene masterbatch resistant to γ-ray radiation color change. The difference between this embodiment and Example 1 is that the weight ratio of non-phenolic antioxidant, N-alkoxy hindered amine light stabilizer (bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate) and crystallization regulator is 1:2:2.

[0037] Example 6 A medical-grade polypropylene masterbatch resistant to γ-ray radiation color change. The difference between this embodiment and Example 1 is that the weight ratio of non-phenolic antioxidant, N-alkoxy hindered amine light stabilizer (bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate) and crystallization regulator is 1:1:3.

[0038] Example 7 A medical-grade polypropylene masterbatch resistant to gamma-ray radiation color change. The difference between this embodiment and Example 1 is that the ratio of methyl 5-formyl-3,4-dihydro-2,2-dimethyl-2H-benzofuran-7-carboxylate to N,N-di(octadecyl)hydroxylamine is 2:1.5.

[0039] Example 8 A medical-grade polypropylene masterbatch resistant to γ-ray radiation color change. The difference between this embodiment and Example 1 is that the benzofuranone compound is 5-methyl-3-(p-methoxyphenyl)-2H-benzofuran-2-one.

[0040] Example 9 A medical-grade polypropylene masterbatch resistant to gamma-ray radiation color change. The difference between this embodiment and Example 1 is that the crystallization regulator is composed of sorbitol nucleating agent (2,4-bis(3,4-dimethylbenzyl)sorbitol) and liquid paraffin, and the weight ratio of the two is 2:1.

[0041] Example 10 A medical-grade polypropylene masterbatch resistant to gamma-ray radiation color change. The difference between this embodiment and Example 1 is that the crystallization regulator is composed of liquid paraffin and low molecular weight polyolefin wax, and the weight ratio of the two is 1:1.

[0042] Example 11 A medical-grade polypropylene masterbatch resistant to γ-ray radiation color change. The difference between this embodiment and Example 1 is that the crystallization regulator is composed of sorbitol nucleating agent (2,4-bis(3,4-dimethylbenzyl)sorbitol), liquid paraffin and low molecular weight polyolefin wax, and the weight ratio of the three is 0.5:1:1.

[0043] Example 12 A medical-grade polypropylene masterbatch resistant to γ-ray radiation color change. The difference between this embodiment and Example 1 is that the polypropylene carrier resin is homopolymer polypropylene with a melt index of 10g / 10min at 230℃ / 2.16kg.

[0044] Comparative Example Comparative Example 1 A medical-grade polypropylene color masterbatch, the difference between this comparative example and Example 1 is that the radiation-resistant composite stabilizer is composed of a non-phenolic antioxidant and a crystallization regulator, and the weight ratio of the non-phenolic antioxidant to the crystallization regulator is 1:3.

[0045] Comparative Example 2 A medical-grade polypropylene masterbatch, the difference between this comparative example and Example 1 is that the radiation-resistant composite stabilizer is composed of an N-alkoxy-hindered amine light stabilizer and a crystallization regulator, and the weight ratio of the N-alkoxy-hindered amine light stabilizer to the crystallization regulator is 2:3.

[0046] Comparative Example 3 A medical-grade polypropylene masterbatch, the difference between this comparative example and Example 1 is that the radiation-resistant composite stabilizer is composed of a non-phenolic antioxidant and an N-alkoxy-hindered amine light stabilizer, and the weight ratio of the non-phenolic antioxidant to the N-alkoxy-hindered amine light stabilizer (bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate) is 1:2.

[0047] Comparative Example 4 A medical-grade polypropylene masterbatch, the difference between this comparative example and Example 1 is that 2,2'-methylenebis(4-methyl-6-tert-butylphenol) is used instead of a non-phenolic antioxidant.

[0048] Detection methods / test methods Yellow Index Determination: According to ASTM E313, the masterbatch was diluted at a ratio of 4% in medical polypropylene base material and injection molded into a standard color plate. After being irradiated with 50kGy γ-rays (cobalt-60 source), the irradiated samples were placed in a thermal accelerated aging chamber at 70℃ for accelerated storage test for 72 days to simulate the long-term natural aging process. The change in yellow index before and after irradiation was measured using a colorimeter (D65 light source, 10° viewing angle), and ΔYI was calculated.

[0049] Tensile strength test: The masterbatch was diluted at a ratio of 4% in medical-grade polypropylene base material and injection molded to obtain samples. According to ASTM D638 standard, Type I specimens were used, with a specimen thickness of 3.2±0.4 mm and a width of 10 mm. Using a universal testing machine, the tensile strength and elongation at break were tested at a tensile speed of 50 mm / min. Radiation aging tests were then conducted according to the yellow index determination test conditions, followed by testing of tensile strength and elongation at break, and the retention rate was calculated. Migration Test: Radiation aging tests were conducted according to the yellow index determination test conditions. Following GB / T 5009.60 standard, the polypropylene masterbatch product to be tested was cut to a contact area / volume ratio of 6 dm² / L, placed in ethanol, sealed in a clean glass container, and immersed at 37℃ for 24 hours. The immersion solution was filtered through a 0.45 μm filter membrane and subjected to qualitative and quantitative analysis using high-performance liquid chromatography (HPLC). Methyl 5-formyl-3,4-dihydro-2,2-dimethyl-2H-benzofuran-7-carboxylic acid was used as the detection target. The migration amount (mg / kg) of each component was calculated using the internal standard method. Each group was measured in triplicate, and the average value was taken. Comparative Example 4 used 2,2'-methylenebis(4-methyl-6-tert-butylphenol) as the detection target. A migration amount <0.01 mg / kg was considered to meet medical-grade safety requirements. Experimental data are shown in Table 1. Table 1. Experimental data of Examples 1-12 and Comparative Examples 1-4

[0050] As can be seen from the above experimental data, this application achieves excellent stability of medical-grade polypropylene masterbatch after γ-ray radiation sterilization through the synergistic compounding of non-phenolic antioxidants, N-alkoxy hindered amine light stabilizers and crystallization regulators.

[0051] Compared with Examples 1 and Comparative Examples 1-4, Comparative Example 1 lacked N-alkoxy hindered amine light stabilizer (leading to severe yellowing and embrittlement); Comparative Example 2 lacked non-phenolic antioxidant, causing moderate yellowing; Comparative Example 3 lacked crystallization regulator, although the color was acceptable, the mechanical properties decreased; Comparative Example 4 used traditional hindered phenolic antioxidant, which resulted in severe yellowing and excessive migration. Example 1, through the synergistic compounding of three components, simultaneously solved the problems of yellowing and mechanical property degradation after radiation sterilization, and the migration amount met medical standards, proving that the ternary system has an irreplaceable synergistic effect.

[0052] Comparing Examples 1 and 4-8, it is evident that the ratio and composition of the three components in the radiation-resistant composite stabilizer have a significant impact on performance: when the proportion of non-phenolic antioxidants is too high, it indicates that excessive antioxidants disrupt the synergistic balance and increase the risk of migration; when the proportion of crystallization regulators or N-alkoxy hindered amine light stabilizers is reduced, mechanical properties or color stability decrease significantly, demonstrating the necessity of optimizing the ratio of the three components (1-2):(2-4):3; when the proportion of hydroxylamine in the non-phenolic antioxidants is reduced or the type of benzofuranone is changed, the performance also deteriorates to varying degrees, further illustrating the key role of specific compound selection and ratio in achieving optimal radiation resistance.

[0053] Comparing Examples 1 and 9-11, it is evident that the ternary compound and complete composition of the crystallization regulator have a positive effect on maintaining the toughness of the material: Example 9 lacks low molecular weight polyolefin wax, and the absence of a flexible transition layer at the crystal region interface leads to a decrease in the elongation at break retention rate; Example 10 lacks sorbitol nucleating agent, and insufficient nucleation centers result in inadequate spherulite refinement, leading to a decrease in the elongation at break retention rate; Example 11 uses too little sorbitol nucleating agent, resulting in insufficient crystallization repair and a similar decrease in mechanical properties; although the color stability of all three is acceptable, their mechanical properties are significantly inferior to those of Example 1, indicating that the synergistic effect of sorbitol nucleating agent, liquid paraffin, and low molecular weight polyolefin wax is indispensable, and the nucleating agent needs to maintain a relatively dominant ratio of 2-4 parts in order to effectively repair irradiated crystal region damage and maintain the long-term reliability of medical polypropylene products.

[0054] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration, characterized in that, It is prepared from the following raw materials in parts by weight: 40-80 parts of polypropylene carrier resin 5-10 parts of radiation-resistant composite stabilizer 3-5 parts dispersant 1-2 parts of processing aid 0-5 parts of pigment; The radiation-resistant composite stabilizer is composed of a non-phenolic antioxidant, an N-alkoxy hindered amine light stabilizer, and a crystallization regulator. The non-phenolic antioxidants are benzofuranone compounds and / or hydroxylamine compounds; The crystallization regulator is at least one of sorbitol nucleating agents, liquid paraffin, and low molecular weight polyolefin wax.

2. The medical-grade polypropylene masterbatch resistant to γ-ray radiation discoloration according to claim 1, characterized in that: The weight ratio of the non-phenolic antioxidant, the N-alkoxy hindered amine light stabilizer, and the crystallization regulator is (1-2):(2-4):

3.

3. The medical-grade polypropylene masterbatch resistant to γ-ray radiation discoloration according to claim 2, characterized in that: The non-phenolic antioxidant is composed of methyl 5-formyl-3,4-dihydro-2,2-dimethyl-2H-benzofuran-7-carboxylic acid and N,N-bis(octadecyl)hydroxylamine in a mass ratio of 1:(1.5-3).

4. The medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration according to claim 1, characterized in that: The N-alkoxy hindered amine light stabilizer is bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate.

5. The medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration according to claim 1, characterized in that: The crystallization regulator is composed of sorbitol nucleating agent, liquid paraffin and low molecular weight polyolefin wax, and the weight ratio of the three is (2-4):1:(1-2).

6. The medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration according to claim 1, characterized in that: The polypropylene carrier resin is homopolymer polypropylene with a melt index of 20-50 g / 10 min at 230℃ / 2.16 kg.

7. The medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration according to claim 1, characterized in that: The dispersant includes at least one of polyethylene wax, oxidized polyethylene wax, ethylene bis-stearamide, and ethylene bis-oleamide.

8. The medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration according to claim 1, characterized in that: The processing aids include at least one of calcium stearate, zinc stearate, magnesium stearate, polyether-modified silicone oil, and silicone masterbatch.

9. A method for preparing a medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration as described in any one of claims 1-8, characterized in that, The preparation steps include the following: S1. Mix polypropylene carrier resin, radiation-resistant composite stabilizer, dispersant, processing aid and pigment to obtain a mixture; S2. The mixture is melt-blended, extruded and granulated to obtain medical-grade polypropylene masterbatch resistant to γ-ray radiation discoloration.

10. The method for preparing the medical-grade polypropylene masterbatch resistant to gamma-ray radiation discoloration according to claim 9, characterized in that: In step S2, a twin-screw extruder is used for melt blending and granulation. The screw speed is 200-400 r / min, the melt temperature is 170-190℃, and the residence time is 1.5-2.5 min.

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