Ultra-high molecular weight polyethylene monofilament with ultra-low solvent residual quantity and manufacturing method and application thereof

Abstract

The invention relates to an ultra-high molecular weight polyethylene monofilament with ultra-low solvent residual quantity and a manufacturing method and application thereof. The ultra-high molecular weight polyethylene monofilament of the present invention has a surface carbon atom concentration of 98% or more and a surface oxygen atom concentration of 2% or less, where the surface atom concentrations are measured by XPS analysis, and the content of a spinning solvent is 20000 ppm or less relative to 100 wt% of the total mass of the ultra-high molecular weight polyethylene monofilament. The ultra-high molecular weight polyethylene monofilament has the characteristic of ultra-low solvent residual quantity, and is particularly suitable for manufacturing medical products.

Description

Technical Field

[0001] The present invention relates to the field of high-performance fibers, and specifically, to an ultra-high molecular weight polyethylene monofilament with an extremely low solvent residue, a manufacturing method thereof, and an application thereof. Background Art

[0002] Existing ultra-high molecular weight polyethylene fiber production technologies are divided into two categories: a wet spinning process using white oil as a solvent and a dry spinning process using decalin as a solvent. For the former, since the solvent needs to be extracted first and then volatilized, the process is complex and the solvent residue in the product is high, resulting in an impure product and making it unable to be used in the medical field. For the latter, it is difficult for the existing technology to achieve an extremely low residue level of the solvent inside the fiber through volatilization, so there is still a gap between the product and the application requirements of the medical field. At the same time, for medical applications, to ensure that the fiber is pure enough and does not cause other adverse reactions, no surface treatment can be performed on the fiber surface. Therefore, the fiber monofilament is prone to divergence and has poor cohesion, making the processing in medical applications difficult. Summary of the Invention

[0003] Ultra-high molecular weight polyethylene fibers are prone to static electricity due to friction during the production and processing process. Therefore, during the production process of the fibers, the problem of cohesion is usually solved by adding antistatic agents, surface coating with sizing agents, etc., so as to achieve an ideal processing and use effect of the fibers. However, this method will result in a complex fiber composition and insufficient purity, and for medical applications, especially applications under conditions such as permanent implantation into the human body, it is easy to cause adverse reactions. The fibers of the present invention can reach an ideal cohesive state without surface treatment such as sizing, ensuring the cleanliness of the implant-grade medical ultra-high molecular weight polyethylene fibers.

[0004] The spinning process uses a dry-state solidification method different from the conventional gel spinning method for ultra-high molecular weight polyethylene fibers. There is no cooling gel process during spinning and forming, and no gel-state nascent filaments are formed. It directly enters the flash solidification stage to form dry-state nascent filaments, enabling the solvent residue to reach an extremely low level and ensuring the cleanliness of the product.

[0005] Specifically, the present invention relates to the following aspects.

[0006] 1. An ultra-high molecular weight polyethylene monofilament, wherein the surface carbon atom concentration is above 98% (preferably above 99%, above 99.5% or substantially 100%), the surface oxygen atom concentration is below 2% (preferably below 1%, below 0.5% or not detected), and each surface atom concentration is measured by XPS analysis. And the content of the spinning solvent is below 20000 ppm (preferably below 10000 ppm, more preferably below 100 ppm, below 10 ppm, below 1 ppm) based on 100 wt% of the total mass of the ultra-high molecular weight polyethylene monofilament.

[0007] 2. The ultra-high molecular weight polyethylene monofilament described in any of the foregoing or following aspects, having a monofilament fineness of 0.5 - 10 dtex (preferably 1.0 - 3.0 dtex), and a fiber strength of 5 - 45 cN / dtex (preferably 10 - 20 cN / dtex).

[0008] 3. The ultra-high molecular weight polyethylene monofilament described in any of the foregoing or following aspects, having a polyethylene crystallinity of ≥50% (preferably ≥70%).

[0009] 4. The ultra-high molecular weight polyethylene monofilament described in any of the foregoing or following aspects, having a flat and elongated arc-shaped cross-section in the free state, with an average unfolded width of the cross-section of 10 μm or more (preferably 20 - 100 μm or 30 - 60 μm), an average thickness of the cross-section of 2 μm or more (preferably 3 - 20 μm or 5 - 10 μm), and / or a ratio of the average unfolded width of the cross-section to the average thickness of the cross-section of 2 or more (preferably 3 - 100 or 5 - 20), and / or a ratio of the average central thickness of the cross-section to the average end thickness of the cross-section of less than 1 (preferably ≤0.5).

[0010] 5. The ultra-high molecular weight polyethylene monofilament described in any of the foregoing or following aspects, not containing a spinning finishing agent or its residue.

[0011] 6. An ultra-high molecular weight polyethylene multifilament formed by bundling multiple (such as 2 - 10000, preferably 5 - 400) ultra-high molecular weight polyethylene monofilaments described in any of the foregoing or following aspects, wherein among the ultra-high molecular weight polyethylene multifilaments, more than 50% (preferably more than 60%, 70%, 80% or 90%) of the ultra-high molecular weight polyethylene monofilaments are in a nested and embracing state.

[0012] 7. The ultra-high molecular weight polyethylene multifilament described in any of the foregoing or following aspects, wherein after the bundling, the obtained ultra-high molecular weight polyethylene multifilament is stretched in one or more stages (such as 1 - 8 or 2 - 5 stages) (multifilament stretching), and the operating conditions of the multifilament stretching include: a stretching temperature of 90 - 160°C (preferably 120 - 140°C), and a (total) stretching ratio of 2 - 200 (preferably 10 - 30).

[0013] 8. A method for manufacturing an ultra-high molecular weight polyethylene monofilament, comprising the following steps:

[0014] 1) Mixing ultra-high molecular weight polyethylene and a solvent to prepare a spinning solution,

[0015] 2) Extruding the spinning solution through a spinneret provided with at least one (such as 50 - 100) spinneret holes to form a spinning filament stream,

[0016] 3) The spinning stream is stretched (initially stretched) at an ambient temperature higher than the boiling point of the solvent (preferably 0.1 - 5 °C or 0.5 - 2 °C higher than the boiling point of the solvent), and the solvent is substantially completely removed from the spinning stream (for example, until the content of the solvent in the spinning stream is 20,000 ppm or less, preferably 10,000 ppm or less, more preferably 100 ppm or less, 10 ppm or less, or 1 ppm or less), to obtain a dry precursor filament.

[0017] 4) With or without stretching, purge air is provided to the dry precursor filament to obtain the ultra-high molecular weight polyethylene monofilament (referred to as the nascent monofilament).

[0018] 9. The manufacturing method according to any one of the foregoing or following aspects, wherein in step 1), based on 100 parts by weight of the ultra-high molecular weight polyethylene, the amount of the solvent used is at most 2,000 parts by weight (preferably 1,000 - 1,500 parts by weight).

[0019] 10. The manufacturing method according to any one of the foregoing or following aspects, wherein in step 1), the solvent is selected from at least one of white oil, mineral oil, naphthalene, decalin, tetralin, kerosene, xylene, toluene, petroleum fraction, halogenated hydrocarbon, cycloalkane, and cycloolefin, preferably decalin.

[0020] 11. The manufacturing method according to any one of the foregoing or following aspects, wherein in step 1), the viscosity-average molecular weight of the ultra-high molecular weight polyethylene is 1 million to 9 million (preferably 3 million - 7 million).

[0021] 12. The manufacturing method according to any one of the foregoing or following aspects, wherein in step 2), the extrusion temperature is 150 - 220 °C (preferably 170 - 180 °C), the extrusion speed is 2 - 20 m / min (3 - 5 m / min), and / or the cross-sectional shape of the spinneret hole is circular or substantially circular, and / or the equivalent circular diameter of the cross-section of the spinneret hole is 0.1 - 3 mm (preferably 0.5 - 1.5 mm), and / or when multiple are provided, the multiple spinneret holes are annularly distributed on the spinneret plate.

[0022] 13. The manufacturing method according to any one of the foregoing or following aspects, wherein after the spinning stream leaves the spinneret plate, step 3) is immediately carried out.

[0023] 14. The manufacturing method according to any one of the foregoing or following aspects, wherein in step 3), the initial stretching causes the cross-sectional shrinkage rate of the spinning stream to be 10 - 10 6(Preferably 100 - 1000), and / or, the draw ratio of the initial drawing is 1 - 10 (preferably 3 - 5), and / or, the ambient temperature is ≤ 250°C (preferably 188 - 210°C).

[0024] 15. The manufacturing method according to any one of the foregoing or following aspects, wherein step 3) is carried out in a hollow cylinder, the hollow cylinder includes a top opening, a bottom opening, and a side wall (i.e., a housing) connecting the top opening and the bottom opening and formed around the central axis of the hollow cylinder, the top opening is hermetically connected to the spinneret, the dry filament leaves the hollow cylinder through the bottom opening, and a heating member is provided on at least a part of the side wall to make the temperature of the inner cavity of the hollow cylinder reach the ambient temperature.

[0025] 16. The manufacturing method according to any one of the foregoing or following aspects, wherein in step 3), a suction power is provided to the bottom opening to make the solvent leave the hollow cylinder in the form of vapor from the bottom opening, and / or, no air flow is input into the hollow cylinder (for example, no purging air inlet is provided on the side wall).

[0026] 17. The manufacturing method according to any one of the foregoing or following aspects, wherein step 3) is carried out under the condition of substantially no external air flow input (preferably substantially no external lateral air flow input, more preferably no purging air input), and / or, the solvent leaves step 3) in the form of vapor together with the dry filament along a direction substantially parallel to the direction of the initial drawing.

[0027] 18. The manufacturing method according to any one of the foregoing or following aspects, wherein step 4) is carried out immediately after step 3) ends.

[0028] 19. The manufacturing method according to any one of the foregoing or following aspects, wherein in step 4), the purging air is provided to the dry filament from one side, both sides, or in a surrounding manner of the dry filament, preferably the purging air is provided to the dry filament only from one side of the dry filament, and / or, in step 4), the temperature of the purging air is 0 - 5°C (preferably 1 - 2°C) higher than the melting point of the dry filament or the temperature of the purging air is ≥ 138°C (preferably 140 - 150°C), and / or, in step 4), the linear velocity of the purging air is 0.01 - 10 m / s (preferably 0.2 - 1 m / s), and / or, in step 4), the draw ratio is 0 - 10 (preferably 3 - 5).

[0029] 20. The manufacturing method according to any one of the foregoing or following aspects further includes step 5): after step 4) ends, cooling the nascent monofilament at a temperature 1 - 120°C (preferably 30 - 50°C) lower than the melting point of the nascent monofilament.

[0030] 21. The manufacturing method described in any of the foregoing or following aspects, wherein in step 5), stretching is present or absent; if stretching is present, the stretching ratio is 1-10 (preferably 3-5).

[0031] 22. A medical product comprising the ultra-high molecular weight polyethylene monofilament described in any of the foregoing or following aspects, the ultra-high molecular weight polyethylene multifilament described in any of the foregoing or following aspects, or the ultra-high molecular weight polyethylene monofilament manufactured by the manufacturing method described in any of the foregoing or following aspects.

[0032] Technical effects

[0033] The present invention obtains a fiber with an irregular flat and elongated cross-section of the monofilament, in a flat or bent and folded state, and the monofilaments are in a nested and embracing state. This embracing-type fiber has the characteristics of high strength, extremely low solvent residue, and single and pure components, and is particularly suitable for medical use. Description of the drawings

[0034] Figure 1 is the microscopic morphology diagram of the fiber.

[0035] Figure 2 is the schematic structural diagram of the spinning and forming area.

[0036] Figure 3 is the schematic principle diagram of the formation of the fiber cross-section morphology. Detailed implementation manners

[0037] The following details the specific implementation manners of the present invention. However, it should be noted that the protection scope of the present invention is not limited by these specific implementation manners, but is determined by the appended claims.

[0038] All publications, patent applications, patents, and other references mentioned in this specification are hereby incorporated by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0039] When this specification uses prefixes such as "well-known to those skilled in the art", "prior art", or similar terms to derive materials, substances, methods, steps, devices, or components, etc., the objects derived by such prefixes cover those commonly used in the art at the time of filing of this application, but also include those that are not commonly used at present but will become commonly recognized in the art as suitable for similar purposes.

[0040] In the context of the present invention, all numerical values of parameters (e.g., quantities or conditions) should be understood to be modified by the term "about" in all cases, whether or not "about" actually appears before the numerical value.

[0041] In the context of the present invention, without specific clarification, the various devices employed in the present invention may adopt structures conventionally selected in the art and are not particularly limited.

[0042] In the context of the present invention, "substantially" means allowing deviations that are acceptable or considered reasonable to those skilled in the art, such as deviations within ±5%, within ±1%, within ±0.5%, or within ±0.1%.

[0043] In the context of the present invention, the measurement method for surface atomic concentration is carried out using a PhiQuantum 2000 device. Samples are prepared by winding wires around a metal sample holder. In each analysis, multiple wires (defined by the analysis area) are measured. Each sample is measured at two positions. During the measurement, the angle between the axis of the analyzer and the sample surface is 45°; the information depth is then approximately 5 nm. Using monochromatic AlKα radiation, the measurement spot is 100 μm; the measurement area is 800×400 μm. Through wide scan measurements, the elements present on the surface have been identified. The chemical state and concentration of the elements are determined by narrow scan measurements. The peak area is converted into atomic concentration using standard sensitivity factors.

[0044] In the context of the present invention, the measurement method for the spinning solvent content is GB / T41671-2022.

[0045] In the context of the present invention, the measurement method for the fineness of monofilaments includes GB / T3916-2013.

[0046] In the context of the present invention, the measurement method for fiber strength is GB / T19975-2005.

[0047] In the context of the present invention, the measurement method for the crystallinity of polyethylene is to convert the crystallinity through thermal analysis using a Diamond DSC differential scanning calorimeter from PerkinElmer, USA. Weigh 8-9 mg of the sample and conduct the experiment under nitrogen protection. Heat from 40°C to 170°C at a rate of 10°C / min and hold for 5 min to eliminate the thermal history; then cool to 40°C at rates of 2.5, 5, 10, 20, and 40°C / min respectively to obtain the cooling curves; then heat to 160°C at a rate of 10°C / min to obtain the second heating curve. The calculation formula for crystallinity is Xc = ΔH / ΔH0, where ΔH is the melting heat enthalpy of the second heating curve, J / g; ΔH0 is the melting heat enthalpy with a crystallinity of 100%, and ΔH0 = 293 J / g.

[0048] In the context of the present invention, the free state refers to the observation state of the fiber under completely undisturbed conditions.

[0049] In the context of the present invention, the average unfolding width refers to straightening the cross-section of a single fiber filament to form the maximum width, measuring the maximum widths of ten single filaments, and taking the average value as the average width.

[0050] In the context of the present invention, the central average thickness refers to straightening the cross-section of a single fiber filament to form the maximum width, taking two parallel tangents at the maximum thickness along the thickness direction of the outer contour of the single filament interface, and measuring the distance between the parallel lines as the thickness of this single filament. Measuring the thicknesses of ten single filaments and taking the average value as the average thickness.

[0051] In the context of the present invention, the end average thickness refers to taking the average value of the thicknesses at both ends in the width direction of a single fiber filament.

[0052] In the context of the present invention, nested interlocking means that the single fiber filaments are not laid flat together but are nested and crossed with each other, as Figure 1 shown.

[0053] In the context of the present invention, non-detection means that the detected amount is lower than the detection limit, usually less than 1 ppm.

[0054] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight, and the pressure is gauge pressure.

[0055] In the context of the present invention, any two or more embodiments or aspects of the present invention can be arbitrarily combined, and the technical solutions formed thereby belong to a part of the original public content of this specification and also fall within the protection scope of the present invention.

[0056] According to an embodiment of the present invention, it relates to a ultra-high molecular weight polyethylene single filament. According to the present invention, the surface carbon atoms of the ultra-high molecular weight polyethylene single filament are more than 98% (preferably more than 99%, more than 99.5% or substantially 100%), and the surface oxygen atom concentration is 2% or less (preferably 1% or less, 0.5% or less or non-detection). The lower the concentration of oxygen atoms, the cleaner the fiber surface, and the more suitable it is for medical applications. More preferably, the ultra-high molecular weight polyethylene single filament does not contain a spinning finish or its residue on its surface or inside.

[0057] According to an embodiment of the present invention, the content of the spinning solvent of the ultra-high molecular weight polyethylene single filament is 20000 ppm or less (preferably 10000 ppm or less, more preferably 100 ppm or less, 10 ppm or less, 1 ppm or less), based on 100 wt% of the total mass of the ultra-high molecular weight polyethylene single filament. Solvent residue easily causes damage to the cell wall and rupture, resulting in the failure of the cytotoxicity test, and the fiber cannot meet the medical requirements. Therefore, the lower the solvent residue, the purer the fiber, and the more suitable it is for medical applications.

[0058] According to an embodiment of the present invention, the filament fineness of the ultra-high molecular weight polyethylene monofilament is 0.5-10 dtex (preferably 1.0-3.0 dtex), and its fiber strength is 5-45 cN / dtex (preferably 20-40 cN / dtex). Without surface treatment of the fiber, it is difficult to perform high-fold stretching, and it will break during the stretching process due to problems such as static electricity and fuzzing, making it difficult to form filaments. This problem is well solved by the technology of the present invention. Not only can filaments be formed, but the monofilaments are nested and self-locked with each other to form high-strength monofilaments during the drawing process, meeting medical applications, especially for use in braided sutures, and can withstand greater tensile forces during use.

[0059] According to an embodiment of the present invention, the polyethylene crystallinity of the ultra-high molecular weight polyethylene monofilament is ≥50% (preferably ≥70%). The higher the crystallinity of the monofilament, the higher the fiber strength. In the case where the fiber has no surface treatment, through the nested self-locking of the monofilaments, high-fold drawing can be tolerated to achieve high crystallinity.

[0060] According to an embodiment of the present invention, the cross-section (original cross-section) of the ultra-high molecular weight polyethylene monofilament in the free state is a flat and long arc. This flat and long arc is naturally formed during the manufacturing process of the monofilament and is not caused by later processing or treatment. The cross-section of the monofilament is arc-shaped, making it easy to nest and cross each other, and through high-fold stretching, a tight bonding effect can be achieved.

[0061] According to an embodiment of the present invention, the average unfolded width of the cross-section is 10 μm or more (preferably 20-100 μm or 30-60 μm), and the average thickness of the cross-section is 2 μm or more (preferably 3-20 μm or 5-10 μm). The cross-sections of ultra-high molecular weight polyethylene fibers produced by existing process technologies are generally circular or nearly circular, with a fiber diameter of 16 μm or more, and the monofilaments cannot nest with each other. The monofilaments of the present invention are smaller in thickness than in width, are easily concave and curved, form mutual nesting and self-locking, and at the same time increase the surface area of the monofilaments, have a large solvent evaporation surface, and extremely low solvent residues.

[0062] According to an embodiment of the present invention, the ratio of the average unfolded width of the cross-section of the ultra-high molecular weight polyethylene monofilament to the average thickness of the cross-section is 2 or more (preferably 3-100 or 5-20).

[0063] According to an embodiment of the present invention, the ratio of the average thickness at the center of the cross-section of the ultra-high molecular weight polyethylene monofilament to the average thickness at the end of the cross-section is less than 1 (preferably ≤0.5). The fiber cross-section presents a shape that is thick at both ends and thin in the middle, making it easier to achieve concavity and mutual nesting.

[0064] According to an embodiment of the present invention, there is also provided an ultra-high molecular weight polyethylene multifilament, which is formed by bundling multiple (such as 2 - 10,000, preferably 5 - 400) ultra-high molecular weight polyethylene monofilaments described in any aspect of the foregoing or following of the present invention. According to the present invention, among the ultra-high molecular weight polyethylene multifilaments, more than 50% (preferably more than 60%, more than 70%, more than 80% or more than 90%) of the ultra-high molecular weight polyethylene monofilaments are in a nested and embracing state. The monofilaments are blown laterally, and the cross-section is arc-shaped, making it easy for them to nest and cross each other. Then, through high-magnification stretching, a tight embracing effect is achieved. The nested and embracing state between the monofilaments solves the problem that the fibers are prone to divergence and fuzzing without surface treatment, making the fibers have excellent processability.

[0065] Figure 1 The schematic microscopic morphology diagram of the fiber of the present invention shows clearly the tight nested state between the fiber monofilaments.

[0066] According to an embodiment of the present invention, after the bundling, the obtained ultra-high molecular weight polyethylene multifilament is stretched (multifilament stretching) in one or more stages (such as 1 - 8 or 2 - 5 stages). Multifilament stretching can enable the monofilaments to be stretched in a nested and embracing state, improving the tensile resistance of the monofilaments under high-magnification stretching conditions. At the same time, due to high-magnification stretching, the cross-section of the monofilaments becomes narrower, and they are tightly squeezed, achieving a better embracing effect.

[0067] According to an embodiment of the present invention, the operating conditions of the multifilament stretching include: the stretching temperature is 90 - 160 °C (preferably 120 - 140 °C), and the (overall) stretching ratio is 2 - 200 (preferably 10 - 30).

[0068] According to an embodiment of the present invention, there is also provided a manufacturing method of an ultra-high molecular weight polyethylene monofilament. According to the present invention, the manufacturing method can be used to manufacture the ultra-high molecular weight polyethylene monofilament of the present invention, but the manufacturing method of the ultra-high molecular weight polyethylene monofilament of the present invention is not limited thereto.

[0069] According to an embodiment of the present invention, the manufacturing method of the ultra-high molecular weight polyethylene monofilament includes step 1) mixing ultra-high molecular weight polyethylene and a solvent to prepare a spinning solution.

[0070] According to an embodiment of the present invention, in step 1), with respect to 100 parts by weight of the ultra-high molecular weight polyethylene, the amount of the solvent used is at most 2000 parts by weight (preferably 1000 - 1500 parts by weight).

[0071] According to an embodiment of the present invention, in step 1), the solvent is selected from at least one of white oil, mineral oil, naphthalene, decalin, tetralin, kerosene, xylene, toluene, petroleum fraction, halogenated hydrocarbon, cycloalkane, and cycloolefin, and preferably decalin.

[0072] According to an embodiment of the present invention, in step 1), the viscosity-average molecular weight of the ultra-high molecular weight polyethylene is 1 million to 9 million (preferably 3 million - 7 million).

[0073] According to an embodiment of the present invention, the method for manufacturing the ultra-high molecular weight polyethylene monofilament includes step 2) extruding the spinning solution through a spinneret provided with at least one (such as 50 - 500) spinneret holes to form a spinning stream.

[0074] According to an embodiment of the present invention, in step 2), the extrusion temperature is 150 - 220 °C (preferably 170 - 180 °C), and the extrusion speed is 2 - 20 m / min (3 - 5 m / min).

[0075] According to an embodiment of the present invention, in step 2), the cross-sectional shape of the spinneret hole is circular or substantially circular. Such a spinneret hole makes the fibers isotropic and the cross-section nearly circular after exiting the spinneret. Under the action of a lateral wind, the morphology between the monofilaments can be made more uniform. Preferably, the equivalent circular diameter of the cross-section of the spinneret hole is 0.1 - 3 mm (preferably 0.5 - 1.5 mm). Additionally, when multiple spinneret holes are provided, preferably the multiple spinneret holes are annularly distributed on the spinneret.

[0076] According to an embodiment of the present invention, the method for manufacturing the ultra-high molecular weight polyethylene monofilament includes step 3) stretching (initial stretching) the spinning stream at an ambient temperature higher than the boiling point of the solvent (preferably 0.1 - 5 °C or 0.5 - 2 °C higher than the boiling point of the solvent) to substantially completely remove the solvent from the spinning stream and obtain a dry raw filament. This step is completely different from the general gel spinning method. By quickly evaporating a large amount of the solvent, the macromolecular chains lose the plasticizing effect of the solvent small molecules and lose their mobility within a short time, achieving the purpose of solidification and entanglement resolution, without introducing other components. Without this step, the macromolecular chains still maintain high motility and will quickly re-entangle, resulting in the inability to further perform high-fold stretching. Here, by way of example, the ambient temperature is generally ≤250 °C (preferably 188 - 210 °C).

[0077] According to the present invention, the so-called substantially complete removal of the solvent means, for example, until the content of the solvent in the spinning stream is 20,000 ppm or less, preferably 10,000 ppm or less, more preferably 100 ppm or less, 10 ppm or less, or 1 ppm or less.

[0078] According to an embodiment of the present invention, after the spinning filament leaves the spinneret plate, step 3) is immediately carried out.

[0079] According to an embodiment of the present invention, in step 3), the initial stretching causes the cross-sectional shrinkage rate of the spinning filament to be 10 - 10 6 (preferably 100 - 1000). A high cross-sectional shrinkage rate will cause the solvent to rapidly migrate to the surface. If the shrinkage rate is too low, the solvent migration is insufficient and there is a lot of residue. If the shrinkage rate is too high, the monofilament cannot withstand high-fold stretching and breaks. By way of example, the stretching ratio of the initial stretching is generally 1 - 10 (preferably 3 - 5).

[0080] According to an embodiment of the present invention, step 3) is carried out under conditions where there is basically no external air flow input, preferably under conditions where there is basically no external lateral air flow input, and more preferably under conditions where there is no purge air input. Under the condition of no air disturbance, the cross-section of the monofilament is isotropic and nearly circular. In the next step of blowing and plasticizing, the difference between the monofilaments will be small and more uniform, reducing the unevenness rate. If there is an air disturbance condition, the monofilaments are weaker here and prone to deformation. In the further process of blowing and plasticizing, the unevenness of the monofilament cross-section will be aggravated, ultimately resulting in poor consistency of the fibers. In addition, the solvent leaves step 3) in the form of vapor along a direction substantially parallel to the direction of the initial stretching together with the dry precursor filament.

[0081] According to an embodiment of the present invention, step 3) is carried out in a hollow cylinder. Here, the hollow cylinder includes a top opening, a bottom opening, and a side wall (i.e., a housing) connecting the top opening and the bottom opening and formed around the central axis of the hollow cylinder. According to an embodiment of the present invention, the top opening can be hermetically connected to the spinneret plate, whereby the dry precursor filament passes through the bottom opening and leaves the hollow cylinder. In addition, a heating member can be provided on at least a part of the side wall to make the temperature of the inner cavity of the hollow cylinder reach the ambient temperature. Preferably, a suction power is provided to the bottom opening so that the solvent leaves the hollow cylinder in the form of vapor from the bottom opening. More preferably, no air flow is input into the hollow cylinder, such as no purge air inlet is provided on the side wall.

[0082] Figure 2 Schematically shown as a schematic diagram of the spinning and forming process, which is divided into three regions. The spinning solution is extruded from the spinneret plate and then enters the evaporation zone to remove the solvent, then enters the blowing and plasticizing zone for cross-section recovery, and finally enters the stretching and setting zone to form ultra-high molecular weight polyethylene monofilaments (referred to as primary monofilaments).

[0083] According to one embodiment of the present invention, the method for manufacturing the ultra-high molecular weight polyethylene monofilament comprises step 4) providing a purge wind to the dry precursor with or without stretching to obtain the ultra-high molecular weight polyethylene monofilament (referred to as nascent monofilament). According to the present invention, for the convenience of implementation, the purge wind can be provided to the dry precursor along a direction that is at a certain angle (such as 30-150°, preferably 60-120°, and particularly preferably substantially 90°) to the traveling direction of the dry precursor, without any particular limitation.

[0084] According to one embodiment of the present invention, after the step 3) is completed, the step 4) is immediately performed.

[0085] According to one embodiment of the present invention, in step 4), there is no particular limitation on the way of providing the purge wind to the dry precursor. The purge wind can be provided to the dry precursor from one side, both sides (such as opposite sides), or in a circumferential manner. However, in order to obtain the specific cross-sectional shape of the monofilament of the present invention (especially the flat and long arc shape), it is preferred to provide the purge wind (also called lateral wind) to the dry precursor only from one side of the dry precursor. The dry primary precursor has a certain plasticity under high temperature conditions, and its initial state is nearly circular. The lateral blowing forms a pressure difference in the radial direction perpendicular to the fiber, with a large pressure in the middle and a small pressure on both sides. While forming a flat shape, the fiber simultaneously bends inward to form an arc shape. Figure 3 The schematic representation is a schematic diagram of the formation principle of a single-filament cross section.

[0086] According to one embodiment of the present invention, in step 4), the temperature of the purge air is 0-5°C higher than the melting point of the dry precursor (preferably 1-2°C higher) or the temperature of the purge air is ≥138°C (preferably 140-150°C). The temperature of the purge air should be above the melting point of the dry precursor. If it is too high, the dry precursor will melt, and if it is too low, the dry precursor will have no plasticity.

[0087] According to one embodiment of the present invention, in step 4), the linear velocity of the purge air is generally 0.01-10 m / s (preferably 0.2-1 m / s). If the purge air velocity is too high, it will damage the dry raw silk, destroy the mechanical strength of the fiber or make it impossible to form a yarn. If it is too low, it will not form a sufficient pressure difference and it will not form an ideal cross section.

[0088] According to one embodiment of the present invention, in step 4), stretching is optional, and the stretching ratio is generally 0-10 (preferably 3-5).

[0089] According to one embodiment of the present invention, the manufacturing method further comprises step 5): after step 4), cooling the spun monofilament at a temperature 1-120° C. (preferably 30-50° C. lower) than the melting point of the spun monofilament.

[0090] According to an embodiment of the present invention, in step 5), stretching is present or absent. If stretching is present, the stretching ratio is 1 - 10 (preferably 3 - 5).

[0091] According to a preferred embodiment of the present invention, during the entire manufacturing process of the ultra-high molecular weight polyethylene monofilament or multifilament, no spinning finishing agent or similar chemical agent is applied to the ultra-high molecular weight polyethylene monofilament or multifilament. As the spinning finishing agent, specifically, chemicals such as silicone oil, polyvinyl alcohol, and polyacrylamide, which have functions such as increasing the cohesion, can be cited. These agents generally contain oxygen atoms. These agents are not allowed for medical devices, especially medical devices implanted into the human body, and the products cannot pass the biocompatibility evaluation. The present invention does not use other components except ultra-high molecular weight polyethylene, ensuring that the fibers are pure enough, and achieving the purpose of bundling through the self-locking and nesting of monofilaments.

[0092] According to an embodiment of the present invention, it also relates to a medical product, comprising the ultra-high molecular weight polyethylene monofilament described in any aspect before or after of the present invention, the ultra-high molecular weight polyethylene multifilament described in any aspect before or after of the present invention, or the ultra-high molecular weight polyethylene monofilament manufactured by the manufacturing method described in any aspect before or after of the present invention. The fibers of the present invention can achieve the purpose of improving the cohesion through the nesting between fiber monofilaments without adding any components. It not only maintains the sufficient purity of the fibers, but also enables the fibers to have good processability, and further eliminates manual processing steps such as cleaning in the subsequent processing of the fibers.

[0093] Examples

[0094] The present invention will be further described in detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0095] Example 1

[0096] The ultra-low solvent residue ultra-high molecular weight polyethylene fiber of this example is obtained through the following process:

[0097] Ultra-high molecular weight polyethylene and a solvent are mixed to form a spinning solution. The viscosity-average molecular weight of the ultra-high molecular weight polyethylene is 6 million. 100 parts by weight of ultra-high molecular weight polyethylene and 1300 parts by weight of the solvent are used. The solvent is decalin. The above components are mixed to form a spinning solution. The spinning solution is extruded through a spinneret plate with 50 spinneret holes to form spinning filaments. The extrusion temperature is 175°C, the extrusion speed is 4 m / min. The cross-sectional shape of the spinneret holes is circular, with a diameter of 1 mm, and the spinneret holes are annularly distributed on the spinneret plate.

[0098] After the spinning solution exits the spinneret holes, it is immediately subjected to solvent removal and stretching (initial stretching) at 195 °C, and the stretching ratio of the initial stretching is 4. After the solvent in the spinning solution is substantially completely removed, dry precursor filaments are obtained. Purge air is provided from one side of the dry precursor filaments, the temperature of the purge air is 149 °C, the purge angle is 90°, the linear velocity is 0.8 m / s, and the stretching ratio is 4, to obtain ultra-high molecular weight polyethylene monofilaments (referred to as nascent monofilaments).

[0099] The ultra-high molecular weight polyethylene multifilaments obtained by cooling the nascent monofilaments at 120 °C and bundling are subjected to multifilament stretching in 3 stages, the stretching temperature is 130 °C, and the total stretching ratio is 15.

[0100] Finally, ultra-high molecular weight polyethylene fibers are obtained, with a residual solvent content of 0.1 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.1 dtex, a fiber strength of 36 cN / dtex, and a crystallinity of 77.8%. The average unfolded width of the cross-section is 42 μm, the average thickness is 5 μm, the ratio of the average thickness at the center to the average thickness at the end is 0.3. Among the multifilaments, more than 90% of the monofilaments are in a nested and embracing state.

[0101] The above fibers can be used as braided threads for implant-grade suture anchors.

[0102] Example 2

[0103] The same as Example 1, except that the extrusion temperature is 180 °C, the extrusion speed is 5 m / min, the cross-sectional shape of the spinneret holes is circular, and the diameter is 0.75 mm. The obtained ultra-high molecular weight polyethylene fibers have a residual solvent content of 2 ppm, a surface carbon atom concentration ≥ 99.6%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.0 dtex, a fiber strength of 34 cN / dtex, and a crystallinity of 75.0%. The average unfolded width of the cross-section is 36 μm, the average thickness is 6 μm, the ratio of the average thickness at the center to the average thickness at the end is 0.2. Among the multifilaments, more than 88% of the monofilaments are in a nested and embracing state.

[0104] The above fibers can be used as braided threads and composite components for sports medicine devices.

[0105] Example 3

[0106] Same as Example 1, except that the extrusion temperature is 170 °C, the extrusion speed is 3 m / min, the cross-sectional shape of the spinneret holes is circular with a diameter of 1.5 mm. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 10 ppm, a surface carbon atom concentration ≥ 99.5%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.9 dtex, a fiber strength of 30 cN / dtex, and a crystallinity of 70.2%. The average unfolded width of the cross-section is 55 μm, the average thickness is 7 μm, the average thickness ratio of the center to the end is 0.5. Among the multifilaments, more than 80% of the monofilaments are in a nested and embracing state.

[0107] The above fibers can be used as braided threads and composite components for sports medicine instruments.

[0108] Example 4

[0109] Same as Example 1, except that the extrusion temperature is 160 °C, the extrusion speed is 2.2 m / min, the cross-sectional shape of the spinneret holes is circular with a diameter of 1.9 mm. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 280 ppm, a surface carbon atom concentration ≥ 98.2%, no detectable surface oxygen atom concentration, a monofilament fineness of 3.2 dtex, a fiber strength of 25 cN / dtex, and a crystallinity of 67%. The average unfolded width of the cross-section is 63 μm, the average thickness is 11 μm, the average thickness ratio of the center to the end is 0.6. Among the multifilaments, more than 71% of the monofilaments are in a nested and embracing state.

[0110] Example 5

[0111] Same as Example 1, except that the extrusion temperature is 150 °C, the extrusion speed is 1.8 m / min, the cross-sectional shape of the spinneret holes is circular with a diameter of 2.8 mm. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 1500 ppm, a surface carbon atom concentration ≥ 98.0%, no detectable surface oxygen atom concentration, a monofilament fineness of 4.0 dtex, a fiber strength of 20 cN / dtex, and a crystallinity of 61%. The average unfolded width of the cross-section is 71 μm, the average thickness is 15 μm, the average thickness ratio of the center to the end is 0.7. Among the multifilaments, more than 65% of the monofilaments are in a nested and embracing state.

[0112] Example 6

[0113] Same as Example 1, except that the extrusion temperature is 190 °C, the extrusion speed is 8 m / min, the cross-sectional shape of the spinneret hole is circular with a diameter of 0.45 mm. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 585 ppm, a surface carbon atom concentration ≥ 98.3%, no detectable surface oxygen atom concentration, a single filament fineness of 1.1 dtex, a fiber strength of 19.4 cN / dtex, and a crystallinity of 57%. The average unfolded width of the cross-section is 48 μm, the average thickness is 4.1 μm, the average thickness ratio of the center to the end is 0.6. Among the multifilaments, more than 62% of the single filaments are in a nested and embracing state.

[0114] Example 7

[0115] Same as Example 1, except that the extrusion temperature is 220 °C, the extrusion speed is 18 m / min, the cross-sectional shape of the spinneret hole is circular with a diameter of 0.2 mm. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 682 ppm, a surface carbon atom concentration ≥ 98.0%, no detectable surface oxygen atom concentration, a single filament fineness of 1.1 dtex, a fiber strength of 10.1 cN / dtex, and a crystallinity of 52%. The average unfolded width of the cross-section is 30 μm, the average thickness is 8 μm, the average thickness ratio of the center to the end is 0.6. Among the multifilaments, more than 50% of the single filaments are in a nested and embracing state.

[0116] Example 8

[0117] Same as Example 1, except that after the spinning solution exits the spinneret hole, solvent removal and stretching (initial stretching) are carried out at 190 °C. The stretching ratio of the initial stretching is 5, the temperature of the purging air is 145 °C, the purging angle is 80°, the linear velocity is 0.5 m / s, and the stretching ratio is 5. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 15 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a single filament fineness of 1.5 dtex, a fiber strength of 35 cN / dtex, and a crystallinity of 76.2%. The average unfolded width of the cross-section is 35 μm, the average thickness is 5 μm, the average thickness ratio of the center to the end is 0.4. Among the multifilaments, more than 92% of the single filaments are in a nested and embracing state.

[0118] The above fibers can be used as braided wires and composite components for sports medicine devices.

[0119] Example 9

[0120] Same as Example 1, except that after the spinning solution exits the spinneret holes, solvent removal and stretching (initial stretching) are carried out at 210 °C. The stretching ratio of the initial stretching is 3, the temperature of the purging air is 142 °C, the purging angle is 85°, the linear velocity is 1.0 m / s, and the stretching ratio is 3. Ultra-high molecular weight polyethylene fibers are obtained with a residual solvent content of 8 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 2.1 dtex, a fiber strength of 34 cN / dtex, and a crystallinity of 77.0%. The average unfolded width of the cross-section is 50 μm, the average thickness is 8 μm, the average thickness ratio of the center to the end is 0.3. Among the multifilaments, more than 90% of the monofilaments are in a nested and embracing state.

[0121] The above fibers can be used as braided wires and composite components for sports medicine instruments.

[0122] Example 10

[0123] Same as Example 1, except that after the spinning solution exits the spinneret holes, solvent removal and stretching (initial stretching) are carried out at 230 °C. The stretching ratio of the initial stretching is 2, the temperature of the purging air is 138 °C, the purging angle is 70°, the linear velocity is 1.5 m / s, and the stretching ratio is 0. Ultra-high molecular weight polyethylene fibers are obtained with a residual solvent content of 105 ppm, a surface carbon atom concentration ≥ 99.5%, no detectable surface oxygen atom concentration, a monofilament fineness of 2.2 dtex, a fiber strength of 28 cN / dtex, and a crystallinity of 67.0%. The average unfolded width of the cross-section is 53 μm, the average thickness is 9 μm, the average thickness ratio of the center to the end is 0.6. Among the multifilaments, more than 75% of the monofilaments are in a nested and embracing state.

[0124] Example 11

[0125] Same as Example 1, except that after the spinning solution exits the spinneret holes, solvent removal and stretching (initial stretching) are carried out at 170 °C. The stretching ratio of the initial stretching is 8, the temperature of the purging air is 162 °C, the purging angle is 60°, the linear velocity is 0.1 m / s, and the stretching ratio is 7. Ultra-high molecular weight polyethylene fibers are obtained with a residual solvent content of 3500 ppm, a surface carbon atom concentration ≥ 98.0%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.1 dtex, a fiber strength of 27 cN / dtex, and a crystallinity of 65%. The average unfolded width of the cross-section is 28 μm, the average thickness is 3.8 μm, the average thickness ratio of the center to the end is 0.8. Among the multifilaments, more than 67% of the monofilaments are in a nested and embracing state.

[0126] Example 12

[0127] Same as Example 1, except that after the spinning solution exits the spinneret holes, solvent removal and stretching (initial stretching) are carried out at 230 °C. The stretching ratio of the initial stretching is 2, the temperature of the purging air is 139 °C, the purging angle is 100°, the linear velocity is 10 m / s, and the stretching ratio is 8. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 1805 ppm, a surface carbon atom concentration ≥ 98.0%, no detectable surface oxygen atom concentration, a monofilament fineness of 3.5 dtex, a fiber strength of 22 cN / dtex, and a crystallinity of 60%. The average unfolded width of the cross-section is 71 μm, the average thickness is 12 μm, and the average thickness ratio of the center to the end is 0.9. Among the multifilaments, more than 52% of the monofilaments are in a nested and embracing state.

[0128] Example 13

[0129] Same as Example 1, except that multifilament stretching is carried out in 2 stages, the stretching temperature is 120 °C, and the total stretching ratio is 10. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 1.5 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.0 dtex, a fiber strength of 38 cN / dtex, and a crystallinity of 79.2%. The average unfolded width of the cross-section is 30 μm, the average thickness is 5 μm, and the average thickness ratio of the center to the end is 0.2. Among the multifilaments, more than 92% of the monofilaments are in a nested and embracing state.

[0130] The above fibers can be used as braided wires and composite components for sports medicine instruments.

[0131] Example 14

[0132] Same as Example 1, except that multifilament stretching is carried out in 4 stages, the stretching temperature is 137 °C, and the total stretching ratio is 27. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 0.5 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.0 dtex, a fiber strength of 37 cN / dtex, and a crystallinity of 78.1%. The average unfolded width of the cross-section is 38 μm, the average thickness is 5.5 μm, and the average thickness ratio of the center to the end is 0.1. Among the multifilaments, more than 95% of the monofilaments are in a nested and embracing state.

[0133] The above fibers can be used as braided wires and composite components for sports medicine instruments.

[0134] Example 15

[0135] Same as Example 1, except that multifilament stretching is carried out in 5 stages, the stretching temperature is 140 °C, and the total draw ratio is 30. Ultra-high molecular weight polyethylene fibers are obtained with a residual solvent content of 0.1 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.3 dtex, a fiber strength of 35 cN / dtex, and a crystallinity of 77.0%. The average unfolded width of the cross-section is 50 μm, the average thickness is 5.0 μm, the average thickness ratio of the center to the end is 0.1. Among the multifilaments, more than 90% of the monofilaments are in a nested and embracing state.

[0136] The above fibers can be used as braided wires and composite components for sports medicine instruments.

[0137] Example 16

[0138] Same as Example 1, except that multifilament stretching is carried out in 1 stage, the stretching temperature is 150 °C, and the total draw ratio is 8. Ultra-high molecular weight polyethylene fibers are obtained with a residual solvent content of 210 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 3.1 dtex, a fiber strength of 20 cN / dtex, and a crystallinity of 65.0%. The average unfolded width of the cross-section is 65 μm, the average thickness is 12 μm, the average thickness ratio of the center to the end is 0.8. Among the multifilaments, more than 60% of the monofilaments are in a nested and embracing state.

[0139] Example 17

[0140] Same as Example 1, except that multifilament stretching is carried out in 7 stages, the stretching temperature is 100 °C, and the total draw ratio is 108. Ultra-high molecular weight polyethylene fibers are obtained with a residual solvent content of 2.0 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.0 dtex, a fiber strength of 25 cN / dtex, and a crystallinity of 60%. The average unfolded width of the cross-section is 25 μm, the average thickness is 3 μm, the average thickness ratio of the center to the end is 0.8. Among the multifilaments, more than 58% of the monofilaments are in a nested and embracing state.

[0141] The above fibers can be used as braided wires and composite components for sports medicine instruments.

[0142] Example 18

[0143] Same as Example 1, except that multifilament stretching is not carried out. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 200 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a single filament fineness of 5.6 dtex, a fiber strength of 4.2 cN / dtex, and a crystallinity of 35%. The average unfolded width of the cross-section is 125 μm, the average thickness is 22 μm, the average thickness ratio of the center to the end is 0.8, and among the multifilaments, more than 18% of the single filaments are in a nested and embracing state.

[0144] Example 19

[0145] Same as Example 1, except that stretching is not carried out when purging air is provided to the dry filaments. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 12 ppm, a surface carbon atom concentration ≥ 99.8%, no detectable surface oxygen atom concentration, a single filament fineness of 1.2 dtex, a fiber strength of 35 cN / dtex, and a crystallinity of 77.3%. The average unfolded width of the cross-section is 45 μm, the average thickness is 6.5 μm, the average thickness ratio of the center to the end is 0.8, and among the multifilaments, more than 92% of the single filaments are in a nested and embracing state.

[0146] Example 20

[0147] Same as Example 1, except that the spinneret holes are flat arc-shaped. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 205 ppm, a surface carbon atom concentration ≥ 99.8%, a single filament fineness of 1.5 dtex, no detectable surface oxygen atom concentration, a fiber strength of 18.5 cN / dtex, and a crystallinity of 56.3%. The average unfolded width of the cross-section is 110 μm, the average thickness is 2.1 μm, the average thickness ratio of the center to the end is 0.6, and among the multifilaments, more than 35% of the single filaments are in a nested and embracing state.

[0148] Example 21

[0149] Same as Example 1, except that after the spinning solution exits the spinneret plate, it first passes through an air layer and then enters the solvent removal area. In this example, a serious shell layer is formed on the fiber surface, and the decalin inside cannot escape, resulting in the inability to form fibers.

[0150] Example 22

[0151] Same as Example 1, except that purge air is provided immediately after the spinning solution exits the spinneret. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 318 ppm, a surface carbon atom concentration of ≥99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.8 dtex, a fiber strength of 4.8 cN / dtex, and a crystallinity of 35.1%. The average unfolded width of the cross-section is 150 μm, the average thickness is 2.5 μm, and the average thickness ratio of the center to the end is 0.8. Among the multifilaments, more than 38% of the monofilaments are in a nested and embracing state.

[0152] Example 23

[0153] Same as Example 1, except that the dry precursor filaments are not immediately provided with purge air for shaping. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 150 ppm, a surface carbon atom concentration of ≥99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.5 dtex, a fiber strength of 30.5 cN / dtex, and a crystallinity of 62.3%. The average unfolded width of the cross-section is 24.3 μm, the average thickness is 15.9 μm, close to circular, and more than 9% of the monofilaments are in a nested and embracing state..

[0154] Example 24

[0155] Same as Example 1, except that purge air is provided from both sides. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 5.6 ppm, a surface carbon atom concentration of ≥99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.5 dtex, a fiber strength of 33.8 cN / dtex, and a crystallinity of 65.6%. The cross-section is nearly dumbbell-shaped, and 65% of the multifilaments are in a nested and embracing state.

[0156] Example 25

[0157] Same as Example 1, except that purge air is provided circumferentially. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 4.6 ppm, a surface carbon atom concentration of ≥99.8%, no detectable surface oxygen atom concentration, a monofilament fineness of 1.5 dtex, a fiber strength of 34.2 cN / dtex, and a crystallinity of 67.1%. The cross-section is nearly dumbbell-shaped, and 68% of the multifilaments are in a nested and embracing state.

[0158] Comparative Example 1

[0159] Same as Example 1, except that the extrusion temperature is 130 °C, the extrusion speed is 1.8 m / min, the cross-sectional shape of the spinneret holes is circular with a diameter of 3.2 mm. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 18500 ppm, a surface carbon atom concentration ≥ 98.0%, no detectable surface oxygen atom concentration, a single filament fineness of 4.5 dtex, a fiber strength of 7.8 cN / dtex, and a crystallinity of 44%. The average unfolded width of the cross-section is 105 μm, the average thickness is 15 μm, the average thickness ratio of the center to the end is 0.8. Among the multifilaments, more than 45% of the single filaments are in a nested and embracing state.

[0160] Comparative Example 2

[0161] Same as Example 1, except that the extrusion temperature is 230 °C, the extrusion speed is 22 m / min, the cross-sectional shape of the spinneret holes is circular with a diameter of 0.5 mm. Ultra-high molecular weight polyethylene fiber cannot be obtained in this example.

[0162] Comparative Example 3

[0163] Same as Example 1, except that after the spinning solution exits the spinneret holes, solvent removal and stretching (initial stretching) are carried out at 270 °C, the stretching ratio of the initial stretching is 12, the temperature of the purge air is 130 °C, the purge angle is 180°, the linear velocity is 15 m / s, and the stretching ratio is 8. Fibers cannot be formed in this example.

[0164] Comparative Example 4

[0165] Same as Example 1, except that after the spinning solution exits the spinneret holes, solvent removal and stretching (initial stretching) are carried out at 250 °C, the stretching ratio of the initial stretching is 1, the temperature of the purge air is 125 °C, the purge angle is 30°, the linear velocity is 13 m / s, and the stretching ratio is 10. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 12080 ppm, a surface carbon atom concentration ≥ 98.0%, no detectable surface oxygen atom concentration, a single filament fineness of 3.2 dtex, a fiber strength of 18 cN / dtex, and a crystallinity of 50%. The average unfolded width of the cross-section is 65 μm, the average thickness is 9 μm, the average thickness ratio of the center to the end is 0.9. Among the multifilaments, more than 44% of the single filaments are in a nested and embracing state.

[0166] Comparative Example 5

[0167] Same as Example 1, except that multifilament stretching is carried out in 10 stages, the stretching temperature is 80 °C, and the total stretching ratio is 245. Ultra-high molecular weight polyethylene fiber cannot be produced in this example.

[0168] Comparative Example 6

[0169] Same as Example 1, except that the spinning dope stream does not pass through the solvent removal zone. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 23500 ppm, the fiber cross-section is nearly circular, and there is no coalescence state.

[0170] Comparative Example 7

[0171] Same as Example 1, except that after the spinning dope stream passes through the solvent removal zone, the residual solvent is more than 40000 ppm. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 21800 ppm.

[0172] Comparative Example 8

[0173] Same as Example 1, except that there is no stretching when the spinning dope stream passes through the solvent removal zone. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 18300 ppm.

[0174] Comparative Example 9

[0175] This example is a gel process. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 206 ppm, the cross-section is nearly circular, and there is almost no coalescence.

[0176] Comparative Example 10

[0177] Same as Example 1, except that there is no air-blowing shaping zone. The obtained ultra-high molecular weight polyethylene fiber has a residual solvent content of 218 ppm, the cross-section is nearly circular, and there is almost no coalescence.

Claims

1. A ultra-high molecular weight polyethylene monofilament, having a surface carbon atom concentration of 98% or more (preferably 99% or more, 99.5% or more, or substantially 100%), a surface oxygen atom concentration of 2% or less (preferably 1% or less, 0.5% or less, or not detected), wherein each surface atom concentration is measured by XPS analysis, and the content of the spinning solvent is 20,000 ppm or less (preferably 10,000 ppm or less, more preferably 100 ppm or less, 10 ppm or less, 1 ppm or less), based on 100 wt% of the total mass of the ultra-high molecular weight polyethylene monofilament.

2. The ultra-high molecular weight polyethylene monofilament according to claim 1, having a monofilament fineness of 0.5 - 10 dtex (preferably 1.0 - 3.0 dtex), a fiber strength of 5 - 45 cN / dtex (preferably 20 - 40 cN / dtex), and a polyethylene crystallinity of ≥50% (preferably ≥70%).

3. The ultra-high molecular weight polyethylene monofilament according to claim 1, having a flat and elongated arc-shaped cross-section in the free state, the average unfolded width of the cross-section being 10 μm or more (preferably 20 - 100 μm or 30 - 60 μm), the average thickness of the cross-section being 2 μm or more (preferably 3 - 20 μm or 5 - 10 μm), and / or the ratio of the average unfolded width of the cross-section to the average thickness of the cross-section being 2 or more (preferably 3 - 100 or 5 - 20), and / or the ratio of the average thickness at the center of the cross-section to the average thickness at the end of the cross-section being less than 1 (preferably ≤0.5).

4. The ultra-high molecular weight polyethylene monofilament according to claim 1, not containing a spinning finishing agent or its residue.

5. A ultra-high molecular weight polyethylene multifilament formed by bundling multiple (such as 2 - 10,000, preferably 5 - 400) ultra-high molecular weight polyethylene monofilaments according to claim 1, wherein among the ultra-high molecular weight polyethylene multifilaments, more than 50% (preferably 60% or more, 70% or more, 80% or more, or 90% or more) of the ultra-high molecular weight polyethylene monofilaments are in a nested and embracing state.

6. The ultra-high molecular weight polyethylene multifilament according to claim 5, wherein after the bundling, the obtained ultra-high molecular weight polyethylene multifilament is stretched in one or more stages (such as 1 - 8 or 2 - 5 stages) (multifilament stretching), and the operating conditions of the multifilament stretching include: The stretching temperature is 90 - 160°C (preferably 120 - 140°C), and the (overall) stretching ratio is 2 - 200 (preferably 10 - 30).

7. A method for manufacturing a ultra-high molecular weight polyethylene monofilament, comprising the following steps: 1) Mixing ultra-high molecular weight polyethylene and a solvent to form a spinning solution, 2) Extruding the spinning solution through a spinneret provided with at least one (such as 50 - 500) spinneret holes to form a spinning filament stream. 3) Stretch (initial stretching) the spinning stream at an ambient temperature higher than the boiling point of the solvent (preferably 0.1 - 5 °C or 0.5 - 2 °C higher than the boiling point of the solvent), and substantially completely remove the solvent from the spinning stream (for example, until the content of the solvent in the spinning stream is 20,000 ppm or less, preferably 10,000 ppm or less, more preferably 100 ppm or less, 10 ppm or less, or 1 ppm or less) to obtain a dry precursor filament. 4) With or without stretching, provide purge air to the dry precursor filament to obtain the ultra-high molecular weight polyethylene monofilament (referred to as the nascent monofilament).

8. The manufacturing method according to claim 7, wherein in step 2), the extrusion temperature is 150 - 220 °C (preferably 170 - 180 °C), the extrusion speed is 2 - 20 m / min (3 - 5 m / min), and / or the shape of the cross-section of the spinneret hole is circular or substantially circular, and / or the equivalent circular diameter of the cross-section of the spinneret hole is 0.1 - 3 mm (preferably 0.5 - 1.5 mm), and / or when multiple are provided, the multiple spinneret holes are annularly distributed on the spinneret plate.

9. The manufacturing method according to claim 7, wherein step 3) is carried out immediately after the spinning stream leaves the spinneret plate.

10. The manufacturing method according to claim 7, wherein in step 3), the initial stretching causes the cross-sectional shrinkage rate of the spinning stream to be 10-10 6 (preferably 100-1000), and / or, the stretching ratio of the initial stretching is 1-10 (preferably 3-5), and / or, the ambient temperature is ≤250°C (preferably 188-210°C).

11. The manufacturing method according to claim 7, wherein step 3) is carried out in a hollow cylinder, the hollow cylinder includes a top opening, a bottom opening, and a side wall (i.e., a housing) connecting the top opening and the bottom opening and formed around the central axis of the hollow cylinder, the top opening is sealingly connected to the spinneret plate, the dry precursor filament passes through the bottom opening and leaves the hollow cylinder, and a heating member is provided on at least a part of the side wall to make the temperature of the inner cavity of the hollow cylinder reach the ambient temperature.

12. The manufacturing method according to claim 11, wherein in step 3), suction power is provided to the bottom opening to make the solvent leave the hollow cylinder in the form of vapor from the bottom opening, and / or no air flow is input into the hollow cylinder (for example, no purge air inlet is provided on the side wall).

13. The manufacturing method according to claim 7, wherein step 3) is carried out under the condition of substantially no external air flow input (preferably substantially no external lateral air flow input, more preferably no purge air input), and / or the solvent leaves step 3) in the form of vapor together with the dry precursor filament along a direction substantially parallel to the direction of the initial stretching.

14. The manufacturing method according to claim 7, wherein step 4) is carried out immediately after the end of step 3).

15. The manufacturing method according to claim 7, wherein in step 4), the purge air is supplied to the dry raw filaments from one side, both sides, or in a surrounding manner of the dry raw filaments, preferably the purge air is supplied to the dry raw filaments only from one side of the dry raw filaments, and / or, in step 4), the temperature of the purge air is 0 - 5 °C higher (preferably 1 - 2 °C higher) than the melting point of the dry raw filaments or the temperature of the purge air is ≥ 138 °C (preferably 140 - 150 °C), and / or, in step 4), the linear velocity of the purge air is 0.01 - 10 m / s (preferably 0.2 - 1 m / s), and / or, in step 4), the draw ratio is 0 - 10 (preferably 3 - 5).

16. The manufacturing method according to claim 7, further comprising step 5): after the end of step 4), cooling the nascent monofilaments at a temperature 1 - 120 °C lower (preferably 30 - 50 °C lower) than the melting point of the nascent monofilaments.

17. The manufacturing method according to claim 16, wherein in step 5), there is stretching or no stretching; if there is stretching, the draw ratio is 1 - 10 (preferably 3 - 5).

18. A medical product comprising the ultra-high molecular weight polyethylene monofilaments according to claim 1, the ultra-high molecular weight polyethylene multifilaments according to claim 5, or ultra-high molecular weight polyethylene monofilaments manufactured by the manufacturing method according to claim 7.

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