Polyethylene fiber with skin-core structure and manufacturing method and application thereof

Abstract

The invention relates to a polyethylene fiber with a skin-core structure and a manufacturing method and application thereof. The polyethylene fiber of the present invention has a core and a skin covering at least a portion of the surface of the core, in which the skin polyethylene has a viscosity average molecular weight of 300,000-1,500,000, and the core polyethylene has a viscosity average molecular weight of 2-20 times that of the core polyethylene. The problems that the ultra-high molecular weight polyethylene fiber is stiff, not soft and poor in skin fitting performance can be solved.

Description

Technical Field

[0001] The present invention relates to the field of high-performance fibers, and in particular to a polyethylene fiber with a sheath-core structure, a manufacturing method thereof and applications thereof. Background Art

[0002] Ultra-high molecular weight polyethylene fiber itself has a regular structure and excellent mechanical properties, but it lacks comfort in the field of clothing applications. The main manifestations are that the fiber is stiff, not soft, and has poor skin adhesion, which hinders its development in textiles.

[0003] CN218561742U discloses an ultra-high molecular weight polyethylene fiber spandex core-spun yarn. The comfort of ultra-high molecular weight polyethylene fibers is improved by covering ultra-high molecular weight polyethylene short fibers with spandex and cellulose fibers. CN115027109A discloses an intrinsic cool fabric composited with bamboo fiber and ultra-high molecular weight polyethylene fiber and its preparation method, which improves the comfort of ultra-high molecular weight polyethylene fibers by composite of different fibers.

[0004] The research and development of ultra-high molecular weight polyethylene fibers at home and abroad is still mainly based on the high strength and high modulus properties of the fibers. The shortcomings of the comfort of ultra-high molecular weight polyethylene fibers are compensated by post-coating, compounding and other means. The process is cumbersome and does not involve changes to the fiber itself to achieve a soft and comfortable effect. Summary of the invention

[0005] Existing ultra-high molecular weight polyethylene fibers have a regular structure and excellent mechanical properties, but the fibers are stiff, have a strong plastic feel, are not soft, and have poor skin adhesion. Post-process coating, compounding and other means can only slightly compensate for the shortcomings in the comfort of ultra-high molecular weight polyethylene fibers, but the process is cumbersome and cannot fundamentally change them to achieve a soft and comfortable effect.

[0006] Specifically, the present invention relates to the following aspects.

[0007] 1. A polyethylene fiber comprising a core and a sheath covering at least a portion (preferably substantially all) of the surface of the core, wherein the viscosity-average molecular weight of the sheath polyethylene is 300,000-1.5 million (preferably 400,000-800,000), and the viscosity-average molecular weight of the core polyethylene is 2-20 times (preferably 3-10 times) the viscosity-average molecular weight of the core polyethylene.

[0008] 2. The polyethylene fiber according to any one of the preceding or following aspects, wherein the intrinsic viscosity of the core polyethylene is 2 to 20 times (preferably 3 to 10 times) the intrinsic viscosity of the sheath polyethylene.

[0009] 3. The polyethylene fiber of any preceding or following aspect, wherein the intrinsic viscosity of the sheath polyethylene is no greater than 15 g / dl (preferably 4-10 g / dl) and the intrinsic viscosity of the core polyethylene is at least 10 g / dl (preferably 15-25 g / dl).

[0010] 4. The polyethylene fiber described in any of the above or below aspects, wherein the viscosity average molecular weight of the sheath polyethylene is 300,000-1.5 million (preferably 400,000-800,000).

[0011] 5. The polyethylene fiber according to any one of the preceding or following aspects, wherein the average diameter is at most 50 μm (preferably 10-30 μm), and the average diameter of the core is at most 40 μm (preferably 10-25 μm).

[0012] 6. The polyethylene fiber of any preceding or following aspect, wherein the average diameter of the core is 70% to less than 100% (preferably 80% to less than 100%) of the average diameter of the polyethylene fiber.

[0013] 7. The polyethylene fiber of any preceding or following aspect, wherein the sheath covers at least a portion of the surface of the core with a predetermined thickness, and the predetermined thickness has a non-uniformity exceeding 10% (eg exceeding 50%).

[0014] 8. The polyethylene fiber according to any one of the preceding or following aspects, wherein the sheath is generated in situ by a spinning process, or the sheath has no bonding interface with the core.

[0015] 9. The polyethylene fiber described in any one of the preceding or following aspects, wherein the single-filament fineness is 0.7-5 dtex (preferably 1.7-2.7 dtex).

[0016] 10. The polyethylene fiber described in any of the above or below aspects has a single-filament bending stiffness of 0.05×10-5-3×10-5 (cN×cm2) (preferably 0.1×10-5-2×10-5 (cN×cm2)) and a breaking strength of 10-45 cN / dtex (preferably 20-40 cN / dtex).

[0017] 11. A method for producing polyethylene fiber, comprising the following steps:

[0018] 1) Mixing ultra-high molecular weight polyethylene, low molecular weight polyethylene and solvent to prepare a spinning solution,

[0019] 2) extruding the spinning solution through a spinneret to form a spinning fine stream,

[0020] 3) while stretching the spinning stream, removing at least a portion (e.g., at least 50 wt%, preferably at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt% or at least 97 wt%) of the solvent from the spinning stream to obtain the polyethylene fiber (referred to as spun fiber),

[0021] The ratio of the drawing speed to the extrusion speed of the spinning fine stream is 1-20 (preferably 2-10).

[0022] 12. The manufacturing method described in any of the preceding or following aspects, wherein in step 1), the amount of the low molecular weight polyethylene used is at most 50 parts by weight (preferably 5-20 parts by weight) relative to 100 parts by weight of the ultra-high molecular weight polyethylene, and the amount of the solvent used is at most 2000 parts by weight (preferably 1000-1500 parts by weight).

[0023] 13. The production method described in any of the preceding or following aspects, wherein in step 1), the solvent is selected from at least one of naphthalene and its hydrogenated derivatives, decalin, tetralin, kerosene, xylene, toluene, petroleum fractions, halogenated hydrocarbons, cycloalkanes, and cycloolefins, preferably decalin.

[0024] 14. The manufacturing method described in any of the above or the 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 to 5 million), and the viscosity-average molecular weight of the low molecular weight polyethylene is 100,000 to 2.8 million (preferably 400,000 to 1.5 million).

[0025] 15. The production method described in any of the above or below aspects, wherein the viscosity average molecular weight of the low molecular weight polyethylene is 0.2-0.8 times (preferably 0.3-0.5 times) the viscosity average molecular weight of the ultra-high molecular weight polyethylene.

[0026] 16. The production method described in any of the preceding or following aspects, wherein the intrinsic viscosity of the low molecular weight polyethylene is 0.2-0.8 times (preferably 0.3-0.5 times) the intrinsic viscosity of the ultra-high molecular weight polyethylene.

[0027] 17. The manufacturing method described in any of the above or below aspects, wherein the intrinsic viscosity of the low molecular weight polyethylene is not more than 18 g / dl (preferably 5-10 g / dl), and the intrinsic viscosity of the ultra-high molecular weight polyethylene is 10-45 g / dl (preferably 15-35 g / dl).

[0028] 18. The manufacturing method according to any one of the preceding or following aspects, wherein in step 2), the extrusion temperature is 150-220°C (preferably 160-200°C), and the extrusion speed is 2-20 m / min (3-10 m / min).

[0029] 19. The manufacturing method described in any of the preceding or following aspects, wherein the spinning stream is immediately subjected to step 3) after leaving the spinneret.

[0030] 20. The manufacturing method described in any of the above or the following aspects, wherein in step 3), the operating conditions include: temperature of 70-180°C (preferably 140-160°C), blowing height of not less than 0.2m (preferably 5-15m), air volume of 50-180m3 / h (preferably 90-150m3 / h).

[0031] 21. The manufacturing method described in any of the above or the following aspects, wherein in step 3), the stretching speed is not less than 2 m / min (preferably 5-20 m / min), and the stretching ratio is not less than 2 (preferably 3-10).

[0032] 22. The manufacturing method described in any of the preceding or following aspects, wherein in step 3), the stretching and the solvent removal are carried out simultaneously, and the duration is not less than 2 minutes (preferably 3-10 minutes).

[0033] 23. The manufacturing method described in any of the preceding or following aspects, wherein after step 3), the spun fiber is stretched in one or more stages (such as 1-8 or 2-5 stages) (referred to as post-stretching).

[0034] 24. The manufacturing method described in any of the above or below aspects, wherein the operating conditions of the post-stretching include: the stretching temperature is 90-160°C (preferably 130-150°C), and the (overall) stretching ratio is 2-30 (preferably 5-15).

[0035] 25. A fabric comprising the polyethylene fiber described in any one of the preceding or following aspects, or made of the polyethylene fiber described in any one of the preceding or following aspects, or made of the polyethylene fiber described in any one of the preceding or following aspects and other fibers.

[0036] 26. The fabric described in any one of the preceding or following aspects further comprises at least one other fiber selected from natural plant fibers, natural animal fibers, artificial regenerated fibers, synthetic fibers and inorganic fibers.

[0037] Technical Effects

[0038] The purpose of the present invention is to manufacture an ultra-high molecular weight polyethylene fiber with a core-skin structure in view of the shortcomings of the prior art, so as to solve the problem that the ultra-high molecular weight polyethylene fiber is stiff but not soft and has poor skin adhesion. During the spinning process, the high molecular weight polyethylene is stretched at a high multiple and fully crystallized along the axial direction to form a rigid core layer, which provides high strength for the fiber, and the low molecular weight polyethylene migrates to the surface with the evaporation of the solvent to form a soft skin layer, thereby achieving the effect of softening the ultra-high molecular weight polyethylene fiber and improving comfort. DETAILED DESCRIPTION

[0039] The specific embodiments of the present invention are described in detail below, but it should be pointed out that the protection scope of the present invention is not limited by these specific embodiments, but is determined by the claims in the appendix.

[0040] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definitions in this specification shall prevail.

[0041] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0042] In the context of the present invention, all numerical values ​​for parameters (eg amounts or conditions) are to be understood as being modified in all instances by the term "about", regardless of whether "about" actually appears before the numerical value.

[0043] In the context of the present invention, the average diameter is measured by microscopic measurement, and the average value is taken from 5 measurements of the maximum diameter.

[0044] In the context of the present invention, the thickness unevenness rate is measured by scanning and measuring using a Keyence VR6000 3D profile measuring instrument, the number of measurements is 10 times, and the unevenness rate calculation formula is:

[0045] In the context of the present invention, the method for measuring the monofilament fineness is GB / T 14343.

[0046] In the context of the present invention, the method for measuring the bending stiffness of a single fiber is to take a fiber sample of 50mm-70mm, place the fiber vertically, and clamp the upper and lower ends by the upper and lower clamps respectively. Before the lower clamp is closed, the fixed weight tension clamp ensures that the fiber is in a straight but not stretched state. The upper clamp in the device is fixed and connected to a force sensor, so that the axial stress magnitude and the bending force of the fiber can be obtained in real time. The lower clamp is connected to a transmission mechanism and can move at a constant speed in the vertical direction under the drive of a stepper motor. In the single fiber bending test, the lower clamp first rises at a constant speed at a set speed, and the fiber is subjected to an axial bending force. As the displacement of the lower clamp gradually increases, the fiber is compressed in the axial direction to bend, and the bending deformation gradually increases.

[0047] In the context of the present invention, the measuring method of breaking strength is GB / T 19975.

[0048] In the context of the present invention, the softness and comfort test is a physical test by 10 professionals, and the physical sensation is scored into 5 levels from low to high, recorded as 1-5 points.

[0049] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this specification are based on weight and pressure is gauge pressure.

[0050] In the context of the present invention, any two or more embodiments or aspects of the present invention may be arbitrarily combined, and the technical solutions thus formed belong to part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0051] According to one embodiment of the present invention, it is related to a polyethylene fiber, comprising a core and a sheath covering at least a portion (preferably substantially all) of the surface of the core. According to the present invention, the sheath is generated in situ by a spinning method, and is not additionally coated on the core by a coating method or the like. To this end, according to the present invention, the sheath has no bonding interface with the core, and the two form a whole.

[0052] According to one embodiment of the present invention, the viscosity average molecular weight of the skin polyethylene is 300,000-1.5 million (preferably 400,000-800,000), and the viscosity average molecular weight of the core polyethylene is 2-20 times (preferably 3-10 times) the viscosity average molecular weight of the core polyethylene. If the molecular weight of the skin polyethylene is too high, it is not easy to migrate to the surface during the evaporation of the solvent and it is difficult to form a skin layer. If the molecular weight of the skin polyethylene is too low, it is difficult to solidify into a stable skin layer after migrating to the surface.

[0053] According to one embodiment of the present invention, the intrinsic viscosity of the core polyethylene is 2-20 times (preferably 3-10 times) the intrinsic viscosity of the sheath polyethylene.

[0054] According to one embodiment of the present invention, the intrinsic viscosity of the sheath polyethylene is not more than 15 g / dl (preferably 4-10 g / dl), and the intrinsic viscosity of the core polyethylene is at least 10 g / dl (preferably 15-25 g / dl).

[0055] According to one embodiment of the present invention, the viscosity average molecular weight of the skin polyethylene is 300,000-1.5 million (preferably 400,000-800,000).

[0056] According to one embodiment of the present invention, the average diameter of the polyethylene fibers is at most 50 μm (preferably 10-30 μm).

[0057] According to one embodiment of the present invention, the average diameter of the core is at most 40 μm (preferably 10-25 μm).

[0058] According to one embodiment of the present invention, the average diameter of the core is 70% to less than 100% (preferably 80% to less than 100%) of the average diameter of the polyethylene fiber. If the diameter of the core is too large, the skin layer is too thin and easily damaged and falls off. If the core layer is too small, the mechanical properties of the fiber are poor.

[0059] According to one embodiment of the present invention, the skin covers at least a portion of the surface of the core with a predetermined thickness, and the unevenness of the predetermined thickness exceeds 10% (such as more than 50%). The skin layer is generated in situ, and is different from the post-processing coating, and its thickness unevenness is relatively large.

[0060] According to one embodiment of the present invention, the skin is generated in situ by a spinning method, or the skin has no bonding interface with the core.

[0061] According to one embodiment of the present invention, the single filament fineness of the polyethylene fiber is 0.7-5 dtex (preferably 1.7-2.7 dtex).

[0062] According to one embodiment of the present invention, the single-filament bending stiffness of the polyethylene fiber is 0.05×10-5-3×10-5 (cN×cm2) (preferably 0.1×10-5-2×10-5 (cN×cm2)), and the breaking strength is 10-45 cN / dtex (preferably 20-40 cN / dtex).

[0063] According to one embodiment of the present invention, a method for manufacturing polyethylene fiber is also provided, comprising the following steps:

[0064] 1) Mixing ultra-high molecular weight polyethylene, low molecular weight polyethylene and solvent to prepare a spinning solution,

[0065] 2) extruding the spinning solution through a spinneret to form a spinning fine stream,

[0066] 3) while stretching the spinning stream, removing at least a portion (e.g., at least 50 wt%, preferably at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt% or at least 97 wt%) of the solvent from the spinning stream to obtain the polyethylene fiber (referred to as spun fiber).

[0067] According to one embodiment of the present invention, the ratio of the stretching speed to the extrusion speed of the spinning fine stream is 1-20 (preferably 2-10). If the ratio of the stretching speed to the extrusion speed is too large, the filaments are easily broken and it is difficult to form fibers. If the ratio of the stretching speed to the extrusion speed is too small, the solvent volatilization speed is too slow, and the skin polyethylene is not easy to migrate to the surface solidified skin layer.

[0068] According to one embodiment of the present invention, in step 1), the amount of the low molecular weight polyethylene is at most 50 parts by weight (preferably 5-20 parts by weight) relative to 100 parts by weight of the ultra-high molecular weight polyethylene, and the amount of the solvent is at most 2000 parts by weight (preferably 1000-1500 parts by weight).

[0069] According to one embodiment of the present invention, in step 1), the solvent is selected from at least one of naphthalene and its hydrogenated derivatives decalin, tetralin, kerosene, xylene, toluene, petroleum fractions, halogenated hydrocarbons, cycloalkanes, and cycloolefins, preferably decalin.

[0070] According to one 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 to 5 million), and the viscosity average molecular weight of the low molecular weight polyethylene is 100,000 to 2.8 million (preferably 400,000 to 1.5 million).

[0071] According to one embodiment of the present invention, the viscosity average molecular weight of the low molecular weight polyethylene is 0.2-0.8 times (preferably 0.3-0.5 times) the viscosity average molecular weight of the ultra-high molecular weight polyethylene.

[0072] According to one embodiment of the present invention, the intrinsic viscosity of the low molecular weight polyethylene is 0.2-0.8 times (preferably 0.3-0.5 times) the intrinsic viscosity of the ultra-high molecular weight polyethylene.

[0073] According to one embodiment of the present invention, the intrinsic viscosity of the low molecular weight polyethylene is not more than 18 g / dl (preferably 5-10 g / dl), and the intrinsic viscosity of the ultra-high molecular weight polyethylene is 10-45 g / dl (preferably 15-35 g / dl).

[0074] According to one embodiment of the present invention, in step 2), the extrusion temperature is 150-220° C. (preferably 160-200° C.), and the extrusion speed is 2-20 m / min (3-10 m / min).

[0075] According to one embodiment of the present invention, the spinning stream is immediately subjected to step 3) after leaving the spinneret.

[0076] According to one embodiment of the present invention, in step 3), the operating conditions include: temperature of 70-180°C (preferably 140-160°C), blowing height of not less than 0.2m (preferably 5-15m), air volume of 50-180m3 / h (preferably 90-150m3 / h).

[0077] According to one embodiment of the present invention, in step 3), the stretching speed is not less than 2 m / min (preferably 5-20 m / min), and the stretching ratio is not less than 2 (preferably 3-10).

[0078] According to one embodiment of the present invention, in step 3), the stretching and the solvent removal are carried out simultaneously, and the duration is not less than 2 minutes (preferably 3-10 minutes).

[0079] According to one embodiment of the present invention, after step 3), the spun fiber is stretched in one or more stages (such as 1-8 or 2-5 stages) (referred to as post-stretching).

[0080] According to one embodiment of the present invention, the post-stretching operation conditions include: a stretching temperature of 90-160° C. (preferably 130-150° C.), and an (overall) stretching ratio of 2-30 (preferably 5-15).

[0081] According to one embodiment of the present invention, it also relates to a fabric, comprising the polyethylene fiber described in any one of the preceding or subsequent aspects of this specification, or made of the polyethylene fiber described in any one of the preceding or subsequent aspects of this specification, or made of the polyethylene fiber described in any one of the preceding or subsequent aspects of this specification and other fibers.

[0082] According to one embodiment of the present invention, the fabric further comprises at least one other fiber selected from natural plant fibers, natural animal fibers, artificial regenerated fibers, synthetic fibers and inorganic fibers.

[0083] Example

[0084] The present invention is further described in detail below using examples and comparative examples, but the present invention is not limited to these examples.

[0085] Example 1

[0086] The polyethylene fiber with skin-core structure in this embodiment is obtained by the following process:

[0087] The core ultra-high molecular weight polyethylene with a viscosity average molecular weight of 4.8 million, the skin polyethylene with a viscosity average molecular weight of 600,000 and decalin are mixed and swollen in a ratio of 100:10:1300 to form a suspension, which is then sheared and dissolved by a screw, and extruded at 180°C and an extrusion speed of 4m / min to form a spinning fine stream. After leaving the spinneret, the spinning fine stream is immediately desolventized to remove at least 98% of the solvent. The temperature is 150°C, the blowing height is 10m, and the air volume is 120m3 / h. During the desolventization, the stretching speed is 16m / min, the stretching ratio is 4, and the stretching is carried out simultaneously with the desolventization, and the experience time is 5min to form the initial raw silk. The initial raw silk is stretched in 3 stages, the stretching temperature is 130°C, and the stretching ratio is 13, to make the finished silk. The average diameter of the finished silk core is 92% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 58%.

[0088] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0089] Example 2

[0090] Same as Example 1, except that the molecular weight of the core ultra-high molecular weight polyethylene is 4 million, the molecular weight of the sheath polyethylene is 400,000, and the viscosity average molecular weight of the core polyethylene is 10 times the viscosity average molecular weight of the core polyethylene. The average diameter of the finished silk core is 95% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 60%.

[0091] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0092] Example 3

[0093] Same as Example 1, except that the molecular weight of the core ultra-high molecular weight polyethylene is 3.2 million, the molecular weight of the sheath polyethylene is 800,000, and the viscosity average molecular weight of the core polyethylene is 4 times the viscosity average molecular weight of the core polyethylene. The average diameter of the finished silk core is 80% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 50%.

[0094] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0095] Example 4

[0096] Same as Example 1, except that the molecular weight of the core ultra-high molecular weight polyethylene is 3.7 million, the molecular weight of the sheath polyethylene is 1.5 million, and the viscosity average molecular weight of the core polyethylene is 2.5 times the viscosity average molecular weight of the core polyethylene. The average diameter of the finished silk core is 70% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 20%.

[0097] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0098] Example 5

[0099] Same as Example 1, except that the molecular weight of the core ultra-high molecular weight polyethylene is 3.5 million, the molecular weight of the sheath polyethylene is 300,000, and the viscosity average molecular weight of the core polyethylene is 15 times the viscosity average molecular weight of the core polyethylene. The average diameter of the finished silk core is 72% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 21%.

[0100] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0101] Example 6

[0102] The same as Example 1, except that the temperature during solvent removal is 160°C, the blowing height is 5m, and the air volume is 150m3 / h. The average diameter of the finished fiber core is 83% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 61%.

[0103] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0104] Example 7

[0105] The same as Example 1, except that the temperature during solvent removal is 140°C, the blowing height is 15m, and the air volume is 90m3 / h. The average diameter of the finished fiber core is 90% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 52%.

[0106] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0107] Example 8

[0108] The same as Example 1, except that the drawing speed is 1.5 times the extrusion speed. The average diameter of the finished filament core is 71% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the non-uniformity of the predetermined thickness is 37%.

[0109] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0110] Example 9

[0111] Same as Example 1, except that the drawing speed is 15 times the extrusion speed. The average diameter of the finished filament core is 70% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 15%.

[0112] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0113] Example 10

[0114] The same as Example 1, except that the solvent removal residence time is 1 minute. The average diameter of the finished fiber core is 73% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 20%.

[0115] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the skin layer is covered outside the fiber core, and there is no bonding interface between the skin layer and the fiber core.

[0116] Comparative Example 1

[0117] Same as Example 1, except that the molecular weight of the ultra-high molecular weight polyethylene is 1.5 times that of the low molecular weight polyethylene.

[0118] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, no sheath layer covering the fiber core can be seen.

[0119] Comparative Example 2

[0120] Same as Example 1, except that the molecular weight of the ultra-high molecular weight polyethylene is 25 times that of the low molecular weight polyethylene.

[0121] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, no sheath layer covering the fiber core can be seen.

[0122] Comparative Example 3

[0123] Same as Example 1, except that the stretching speed is 0.5 times the extrusion speed.

[0124] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, no sheath layer covering the fiber core can be seen.

[0125] Comparative Example 4

[0126] Same as Example 1, except that the stretching speed is 25 times the extrusion speed.

[0127] The ratio is too large, resulting in many broken threads and poor yarn formation.

[0128] Comparative Example 5

[0129] The same as Example 1, except that low molecular weight polyethylene is not added, and a layer of polyurethane coating is applied on the surface after the finished filament is made. The average diameter of the finished filament core is 52% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 5%.

[0130] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, it can be seen that the fiber core is covered with a skin layer, and the skin layer and the fiber core have a bonding interface.

[0131] Comparative Example 6

[0132] The fiber is commercially available LY25 400D ultra-high molecular weight polyethylene fiber.

[0133] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, there is no skin-core structure.

[0134] Comparative Example 7

[0135] The same as Example 1, except that the gel spinning method is used. After the spinning solution exits the spinneret, the solvent is not removed immediately, but it is first cooled, the cooling temperature is 30°C, and the cooling time is ≤1min. The average diameter of the finished fiber core is 45% of the average diameter of the ultra-high molecular weight polyethylene fiber, and the unevenness of the predetermined thickness is 10%.

[0136] By observing the cross section of the ultra-high molecular weight polyethylene fiber of this example, no sheath layer covering the fiber core can be seen.

[0137]

Claims

1. A polyethylene fiber comprising a core and a sheath covering at least a portion (preferably substantially all) of the surface of the core, wherein the viscosity-average molecular weight of the sheath polyethylene is 300,000-1.5 million (preferably 400,000-800,000), and the viscosity-average molecular weight of the core polyethylene is 2-20 times (preferably 3-10 times) the viscosity-average molecular weight of the core polyethylene.

2. The polyethylene fiber of claim 1, wherein the intrinsic viscosity of the core polyethylene is 2 to 20 times (preferably 3 to 10 times) the intrinsic viscosity of the sheath polyethylene.

3. The polyethylene fiber of claim 1, wherein the intrinsic viscosity of the sheath polyethylene is no greater than 15 g / dl (preferably 4-10 g / dl) and the intrinsic viscosity of the core polyethylene is at least 10 g / dl (preferably 15-25 g / dl).

4. The polyethylene fiber of claim 1, wherein the viscosity-average molecular weight of the sheath polyethylene is 300,000-1.5 million (preferably 400,000-800,000).

5. The polyethylene fiber of claim 1, which has an average diameter of at most 50 μm (preferably 10-30 μm), and the average diameter of the core is at most 40 μm (preferably 10-25 μm).

6. The polyethylene fiber of claim 5, wherein the average diameter of the core is 70% to less than 100% (preferably 80% to less than 100%) of the average diameter of the polyethylene fiber.

7. The polyethylene fiber of claim 1, wherein the sheath covers at least a portion of the surface of the core with a predetermined thickness, and the predetermined thickness has a non-uniformity of more than 10% (such as more than 50%).

8. The polyethylene fiber of claim 1, wherein the sheath is generated in situ by a spinning process, or the sheath has no bonding interface with the core.

9. A method for producing polyethylene fiber, comprising the following steps: 1) Mixing ultra-high molecular weight polyethylene, low molecular weight polyethylene and solvent to prepare a spinning solution, 2) extruding the spinning solution through a spinneret to form a spinning fine stream, 3) while stretching the spinning stream, removing at least a portion (e.g., at least 50 wt%, preferably at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt% or at least 97 wt%) of the solvent from the spinning stream to obtain the polyethylene fiber (referred to as spun fiber), The ratio of the drawing speed to the extrusion speed of the spinning fine stream is 1-20 (preferably 2-10).

10. The manufacturing method according to claim 9, wherein in step 2), the extrusion temperature is 150-220°C (preferably 160-200°C), and the extrusion speed is 2-20 m / min (3-10 m / min).

11. The manufacturing method according to claim 9, wherein the spinning stream is immediately subjected to step 3) after leaving the spinneret.

12. The manufacturing method of claim 9, wherein in step 3), the operating conditions include: The temperature is 70-180°C (preferably 140-160°C), the blowing height is not less than 0.2m (preferably 5-15m), and the air volume is 50-180m3 / h (preferably 90-150m3 / h).

13. The manufacturing method according to claim 9, wherein in step 3), the stretching speed is not less than 2 m / min (preferably 5-20 m / min), and the stretching ratio is not less than 2 (preferably 3-10).

14. The manufacturing method according to claim 9, wherein in step 3), the stretching and the solvent removal are carried out simultaneously, and the duration is not less than 2 minutes (preferably 3-10 minutes).

15. A fabric comprising the polyethylene fiber of claim 1, or made of the polyethylene fiber of claim 1, or made of the polyethylene fiber of claim 1 and other fibers.

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