A co-extruded polypropylene / poly-4-methyl-1-pentene microporous hollow fiber and a preparation method and application thereof

Abstract

The application discloses a kind of co-extrusion polypropylene / poly-4-methyl-1-pentene microporous hollow fibers and its preparation method and application, belong to the technical field of hollow fiber.The method is by co-extrusion way polypropylene (PP) and poly-4-methyl-1-pentene (PMP) compound, PP forms inner layer microporous structure, PMP forms outer layer dense skin, give consideration to strength and anti-leakage.The preparation process includes melt co-extrusion, cooling traction, annealing, hot stretching and setting, simple and efficient process.The obtained fiber has excellent gas permeability and anti-plasma leakage performance, suitable for extracorporeal membrane oxygenation (ECMO) technology, effectively prolongs the service life of oxygenator, solves the problem that traditional PP fiber is easy to leak, PMP fiber is low in strength.

Description

Technical Field

[0001] This invention belongs to the field of hollow fiber technology, and particularly relates to a co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber, its preparation method and application. Background Technology

[0002] Extracorporeal membrane oxygenation (ECMO), a key extracorporeal life support technology for treating severe cardiopulmonary failure, relies on an oxygenator as its core component, the "artificial lung." This device functions by encapsulating a fabric woven from thousands of hollow fibers. Its working mechanism is based on concentration gradient-driven gas exchange: as blood flows over the outer surface of the hollow fibers, oxygen selectively permeates from the fiber lumen into the blood, while carbon dioxide from the blood flows back into the fiber lumen, ultimately completing the blood oxygenation process.

[0003] Currently, the mainstream materials for hollow fibers used in ECMO oxygenators are polypropylene (PP) and poly4-methyl-1-pentene (PMP), but both have significant technical limitations.

[0004] PP hollow fibers, with their high porosity and excellent mechanical strength, can achieve efficient gas exchange and oxygenation. However, as disclosed in patent CN107297155B, the outer surface of PP hollow fibers in contact with blood also has micropores. This structural defect leads to frequent thrombosis and plasma leakage problems in practical applications. According to publicly available data from Maquet (Germany), Terumo (Japan), and Medtronic (USA), the service life of PP hollow fibers used in ECMO oxygenators is only 6-8 hours, which can only meet short-term treatment needs.

[0005] PMP (Polymethyl methacrylate) materials, due to their large isobutyl side chains, possess excellent gas permeability, chemical stability, and biocompatibility, making them a mainstream choice in the current market. To construct a dense outer layer on the fiber surface to improve leak resistance, the industry typically uses the thermally induced phase separation (TIPS) method to prepare PMP hollow fibers (e.g., patent CN114602333B). This method requires adding a large amount of diluent to the PMP, and after melt extrusion, the fibers must be immersed in an extractant for more than 24 hours to remove the diluent, thereby forming pores inside the fiber. However, the use of large amounts of organic reagents places extremely high demands on the precision of production equipment, environmental safety control, and product biotoxicity testing in the TIPS method. Simultaneously, the isobutyl side chains also result in low crystallinity and poor mechanical strength in PMP materials, making them prone to breakage not only during the weaving and fabrication of oxygenators but also easily deformed in actual clinical applications.

[0006] To address the issue of insufficient mechanical properties of PMP, patents CN116020282A and CN113975981B propose using the TIPS method to blend polypropylene, polysulfone, and PMP to enhance fiber strength. However, in such solutions, the PMP content needs to be higher than 70%, and the interface between the two phases formed by blending is prone to defects. These defects can easily lead to fiber breakage under stress concentration at the weaving points, severely affecting the service life of the oxygenator.

[0007] In summary, the localization process of high-performance, long-life hollow fiber for ECMO still faces many obstacles. Developing a hollow fiber with simple preparation process and high mechanical strength, long-term surface impermeability and high air permeability has become a key problem that the industry urgently needs to solve. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber, its preparation method, and its application.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] One objective of this invention is to provide a method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0011] Two extruders are used to plasticize and melt polypropylene and poly4-methyl-1-pentene respectively. The polypropylene is co-extruded through a die consisting of two concentric ring nozzles. Polypropylene is located in the inner layer and poly4-methyl-1-pentene is located in the outer layer. The extruded melt is cooled in a water tank and then drawn and wound by a traction mechanism to obtain co-extruded hollow nascent fibers.

[0012] The co-extruded hollow nascent fibers were subjected to annealing heat treatment to obtain heat-treated co-extruded hollow fibers.

[0013] The co-extruded hollow fibers were subjected to hot stretching and heat setting to obtain the co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers.

[0014] The co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber provided by this invention incorporates high-mechanical-strength polypropylene into the inner layer of traditional poly4-methyl-1-pentene hollow fiber through co-extrusion, thereby enhancing the mechanical strength of the hollow fiber. Simultaneously, the asymmetric structure of the inner PP microporous layer and the outer PMP sheath gives the co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber high resistance to plasma leakage, while also meeting the gas permeation rate requirements for microporous hollow fibers used in ECMO.

[0015] Furthermore, the polypropylene is homopolymer polypropylene with a melt index of 6-15 g / 10 min.

[0016] Furthermore, the poly-4-methyl-1-pentene is a homopolymer poly-4-methyl-1-pentene with a melt index of 12-32 g / 10 min.

[0017] Furthermore, the temperature of the die head is 260-290℃.

[0018] Furthermore, the temperature of the cooling water in the water tank is 5-25℃, and the distance between the water surface and the mold head is 10-100mm. The cooling water temperature and the distance between the water surface help to rapidly cool the outer layer of poly-4-methyl-1-pentene, inhibit the crystallization process of the molecular chain, and help to form a low-crystallinity spherulitic structure outer layer of poly-4-methyl-1-pentene.

[0019] Furthermore, the traction speed is 60-600 m / min, more preferably 250-450 m / min. The traction speed helps the inner polypropylene melt form a lamellar structure with parallel alignment perpendicular to the extrusion direction after stretching.

[0020] Furthermore, the annealing heat treatment is performed at a temperature of 145°C for 30 minutes. At this temperature, the lamellar structure and strength of the polypropylene in the hollow fiber inner layer are further improved. At the same time, this temperature is much lower than the crystallization temperature range of poly(4-methyl-1-pentene) (170-215°C), and has no effect on the crystallinity of the outer layer material.

[0021] Furthermore, this invention involves specifically stretching the aforementioned heat-treated co-extruded hollow fibers, causing the lamellar crystals of the inner polypropylene layer to separate and form a porous structure, while the spherulitic structure of the outer poly(4-methyl-1-pentene) layer remains intact, ultimately yielding microporous hollow fibers with an internally porous outer sheath structure. The specific hot-stretching steps are as follows: the obtained heat-treated co-extruded hollow fibers are hot-stretched at 50-90°C, with a stretch ratio of 120-200% and a stretching speed of 10-300 mm / min; the stretched fibers are then heat-set at 10-30°C above the stretching temperature for 10-30 minutes to obtain microporous hollow fibers with an internally porous outer sheath structure.

[0022] A second objective of this invention is to provide a co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber prepared using the above-described method, comprising an inner layer and an outer layer; the inner layer is a polypropylene microporous layer, and the outer layer is a dense poly4-methyl-1-pentene skin layer. The prepared co-extruded microporous hollow fiber exhibits a uniform pore size distribution in the inner layer and a pore-free outer layer, resulting in significantly improved mechanical strength and service life.

[0023] The third objective of this invention is to provide an application of co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber in extracorporeal membrane oxygenation (ECMO) technology.

[0024] A fourth objective of this invention is to provide an oxygenator comprising the co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] This invention utilizes melt extrusion to co-extrude polypropylene and poly(4-methyl-1-pentene) to obtain hollow fibers with a high-strength PP lamellar inner layer and a low-crystallinity PMP spherulitic outer layer. A one-step stretching and shaping process yields co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers. The preparation method is simple and rapid. By controlling different traction speeds and stretching conditions, high-rigidity, high-gas-permeability, and long-lasting anti-plasma leakage microporous hollow fibers for ECMO can be rapidly prepared. Attached Figure Description

[0027] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0028] Figure 1 This is a scanning electron microscope image of the inner surface of co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber in Example 3.

[0029] Figure 2 This is a scanning electron microscope (SEM) image of the outer surface of the co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber in Example 3.

[0030] Figure 3 This is a scanning electron microscope image of the outer surface of the polypropylene microporous hollow fiber in Comparative Example 1. Detailed Implementation

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0034] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0035] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0036] This invention provides a method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0037] 1. Raw material preparation: Homopolymer polypropylene with a melt index of 6-15 g / 10 min is selected as the inner layer raw material, and homopolymer poly-4-methyl-1-pentene with a melt index of 12-32 g / 10 min is selected as the outer layer raw material.

[0038] 2. Melt co-extrusion: Two extruders are used to plasticize and melt polypropylene and poly4-methyl-1-pentene respectively, and then co-extrusion is carried out through a die consisting of two concentric ring nozzles (die temperature is controlled at 260-290℃), in which polypropylene is located in the inner layer and poly4-methyl-1-pentene is located in the outer layer.

[0039] 3. Cooling and Traction Winding: The extruded melt enters a water tank for cooling. The temperature of the cooling water in the water tank is 5-25℃, and the distance between the water surface and the die head is 10-100mm. The cooled fibers are drawn by the traction mechanism at a speed of 60-600m / min (preferably 250-450m / min) and wound to obtain co-extruded hollow nascent fibers.

[0040] 4. Annealing heat treatment: The co-extruded hollow nascent fibers are placed in an environment of 145℃ for annealing heat treatment for 30 minutes to obtain heat-treated co-extruded hollow fibers.

[0041] 5. Hot stretching and heat setting: The heat-treated co-extruded hollow fibers are hot stretched at 50-90℃ with a stretch ratio of 120-200% and a stretching speed of 10-300 mm / min. After stretching, the fibers are heat-set at 10-30℃ above the stretching temperature for 10-30 min to finally obtain co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers.

[0042] For example, in the following preferred embodiments of the present invention, the melt index of the homopolymer polypropylene is 6 g / 10 min, 10 g / 10 min or 15 g / 10 min.

[0043] For example, in the following preferred embodiments of the present invention, the melt index of the homopolymer poly(4-methyl-1-pentene) is 12 g / 10 min, 20 g / 10 min or 32 g / 10 min.

[0044] For example, in the following preferred embodiments of the present invention, the die head temperature is 260°C or 290°C.

[0045] For example, in the following preferred embodiments of the present invention, the temperature of the cooling water in the water tank is 5°C or 25°C.

[0046] For example, in the following preferred embodiments of the present invention, the distance between the water surface and the mold head is 10 mm or 100 mm.

[0047] For example, in the following preferred embodiments of the present invention, the traction speed is 60 m / min, 300 m / min or 600 m / min.

[0048] For example, in the following preferred embodiments of the present invention, the temperature of the thermal stretching is 50°C, 60°C or 90°C.

[0049] For example, in the following preferred embodiments of the present invention, the stretching ratio of the thermal stretching is 120%, 140%, or 200%.

[0050] For example, in the following preferred embodiments of the present invention, the stretching speed of the thermal stretching is 10 mm / min, 200 mm / min or 300 mm / min.

[0051] For example, in the following preferred embodiments of the present invention, the heat setting temperature can be carried out in an environment 10°C or 30°C above the stretching temperature.

[0052] For example, in the following preferred embodiments of the present invention, the heat setting time is 10 min or 30 min.

[0053] All raw materials used in this invention were purchased from the market.

[0054] The technical solution of the present invention will be further illustrated by the following embodiments.

[0055] Example 1

[0056] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0057] Homopolymer polypropylene with a melt index of 6 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 12 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and a distance of 10 mm between the water surface and the die. The cooled fibers were drawn by a traction mechanism at a speed of 60 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 120% strain at 50℃ at a speed of 10 mm / min. Subsequently, they were set at 60℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0058] Example 2

[0059] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0060] Homopolymer polypropylene with a melt index of 15 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 32 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 290℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 25℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 600 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 200% strain at 90℃ and a speed of 300 mm / min. Subsequently, they were set at 120℃ for 30 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0061] Example 3

[0062] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0063] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 60℃ at a speed of 200 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0064] Example 4

[0065] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0066] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 600 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 200% strain at 60℃ at a speed of 10 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0067] Example 5

[0068] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0069] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 120% strain at 60℃ at a speed of 10 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0070] Example 6

[0071] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0072] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 120% strain at 60℃ at a speed of 300 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0073] Example 7

[0074] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0075] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 90℃ at a speed of 200 mm / min. Subsequently, they were set at 100℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0076] Example 8

[0077] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0078] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 60℃ at a speed of 200 mm / min. Subsequently, they were set at 70℃ for 30 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0079] Example 9

[0080] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0081] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 90℃ at a speed of 200 mm / min. Subsequently, they were set at 120℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0082] Comparative Example 1

[0083] A method for preparing polypropylene microporous hollow fibers, comprising the following steps:

[0084] Homopolymer polypropylene with a melt index of 10 g / 10 min is added to a single-screw extruder and extruded through a circular nozzle die (die temperature is 260℃). The extruded melt enters a water bath for cooling. The cooling water temperature in the water bath is 5℃, and the distance between the water surface and the die is 100 mm. The cooled fibers are drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers are annealed at 145℃ for 30 min, stretched at 60℃ at a speed of 200 mm / min to 140% strain, and then set at 70℃ for 10 min to obtain polypropylene microporous hollow fibers.

[0085] Comparative Example 2

[0086] A method for preparing poly(4-methyl-1-pentene) microporous hollow fibers, comprising the following steps:

[0087] Homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min was added to a single-screw extruder and extruded through a circular nozzle die (die temperature 260°C). The extruded melt was cooled in a water bath at a water temperature of 5°C, with a water surface 100 mm away from the die. The cooled fibers were then drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145°C for 30 min, stretched to 140% strain at 60°C at a speed of 200 mm / min, and then set at 70°C for 10 min to obtain poly(4-methyl-1-pentene) microporous hollow fibers.

[0088] Comparative Example 3

[0089] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0090] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were stretched to 140% strain at 60℃ and a speed of 200 mm / min, and then set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0091] Comparative Example 4

[0092] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0093] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 10 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 60℃ at a speed of 200 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0094] Comparative Example 5

[0095] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0096] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 50 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 60℃ at a speed of 200 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0097] Comparative Example 6

[0098] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0099] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 50℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 60℃ at a speed of 200 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0100] Comparative Example 7

[0101] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0102] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 60℃ at a speed of 1 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0103] Comparative Example 8

[0104] A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, comprising the following steps:

[0105] Homopolymer polypropylene with a melt index of 10 g / 10 min and homopolymer poly(4-methyl-1-pentene) with a melt index of 20 g / 10 min were added to different extruders and co-extruded through a circular nozzle die (die temperature 260℃). The homopolymer polypropylene was located in the inner layer and the homopolymer poly(4-methyl-1-pentene) was located in the outer layer. The extruded melt was cooled in a water bath at a water temperature of 5℃ and the distance between the water surface and the die was 100 mm. The cooled fibers were drawn by a traction mechanism at a speed of 300 m / min and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were annealed at 145℃ for 30 min and then stretched to 140% strain at 60℃ at a speed of 500 mm / min. Subsequently, they were set at 70℃ for 10 min to obtain co-extruded polypropylene / poly(4-methyl-1-pentene) microporous hollow fibers.

[0106] Performance testing:

[0107] The properties of the microporous hollow fibers prepared in Examples 1-9 and Comparative Examples 1-8 were characterized, and the characterization test results are shown in Table 1 and 2. Figures 1-3 .

[0108] Table 1 Performance Test Results

[0109]

[0110] Figure 1 and Figure 2 The images shown are scanning electron microscope (SEM) images of the inner and outer surfaces of the co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber in Example 3.

[0111] Figure 3This is a scanning electron microscope image of the outer surface of the polypropylene microporous hollow fiber in Comparative Example 1.

[0112] By comparing the properties of Examples 1-9 and Comparative Examples 1-8 in Table 1, it can be seen that the yield strength of the co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber obtained by introducing higher-strength polypropylene as the inner layer is higher than that of the poly4-methyl-1-pentene microporous hollow fiber. This allows the fiber to maintain its condition better during weaving, packaging, and service, thus extending its service life. Meanwhile, from... Figure 1-3 It can be seen that when stretched above the glass transition temperature, the outer surface of the poly4-methyl-1-pentene spherulites of co-extruded polypropylene / poly4-methyl-1-pentene hollow fibers can maintain a dense skin layer, which greatly improves the anti-plasma leakage time of co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers.

[0113] In summary, the yield strength, gas permeability, and anti-plasma leakage properties of the co-extruded polypropylene / poly4-methyl-1-pentene hollow fiber obtained by this invention meet the requirements for use of hollow fibers in ECMO.

[0114] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers, characterized in that, Includes the following steps: Polypropylene and poly4-methyl-1-pentene are plasticized and melted using two extruders respectively, and then co-extruded through concentric double-ring dies. Polypropylene is located in the inner layer and poly4-methyl-1-pentene is located in the outer layer. The extruded melt is cooled by water, drawn, and wound to obtain co-extruded hollow nascent fibers. The co-extruded hollow nascent fibers were subjected to annealing heat treatment to obtain heat-treated co-extruded hollow fibers. The heat-treated co-extruded hollow fibers were subjected to hot stretching and heat setting to obtain the co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fibers. The polypropylene is homopolymer polypropylene with a melt index of 6-15 g / 10 min; The poly4-methyl-1-pentene is a homopolymer poly4-methyl-1-pentene with a melt index of 12-32 g / 10 min; The temperature of the die head is 260-290℃; The temperature of the cooling water is 5-25℃, and the distance between the water surface and the mold head is 10-100mm. The traction speed is 60-600 m / min; The specific operation steps of the hot stretching are as follows: the heat-treated co-extruded hollow fiber is hot-stretched at 50-90℃, with a stretching ratio of 120-200% and a stretching speed of 10-300mm / min. The specific steps for heat setting are as follows: heat set for 10-30 minutes at a temperature 10-30°C above the stretching temperature; The annealing heat treatment was performed at a temperature of 145°C for 30 minutes.

2. A co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber prepared by the preparation method of claim 1, characterized in that, It includes an inner layer and an outer layer; the inner layer is a polypropylene microporous layer, and the outer layer is a poly4-methyl-1-pentene dense skin layer.

3. An oxygenator, characterized in that, It comprises the co-extruded polypropylene / poly4-methyl-1-pentene microporous hollow fiber as described in claim 2.

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