Preparation method of ultra-high molecular weight polyethylene coarse denier fiber

Abstract

The invention relates to the field of preparation of high polymer materials, in particular to a preparation method of ultra-high molecular weight polyethylene coarse denier fibers, and discloses a preparation method of ultra-high molecular weight polyethylene coarse denier fibers, which comprises the following steps: extruding a spinning solution through a spinneret plate to obtain gel yarns; cooling the gel yarn twice, preheating, drafting, oiling and rolling to obtain a precursor yarn; and performing multi-stage stretching on the protofilament to obtain the ultra-high molecular weight polyethylene coarse denier fiber. By means of the process of cooling twice and then preheating, the'skin-core 'structure of the fiber appears firstly and then is eliminated, so that a solvent in the gel silk is continuously separated out along with the preparation process, the situations of silk breakage and broken silk caused by the'skin-core' structure of the gel silk in the preparation process are avoided, and the solid gel silk with the'skin-core 'structure basically eliminated is obtained after cooling twice. Preheating to soften and melt the solid gel filaments to prepare stretchable gel filaments; and finally, the ultra-high molecular weight polyethylene coarse denier fiber with large filament number and good mechanical property is prepared.

Description

Technical Field

[0001] The invention relates to the field of polymer material preparation, and in particular to a method for preparing ultra-high molecular weight polyethylene coarse denier fibers. Background Art

[0002] Since the advent of gel spinning technology, the production technology of ultra-high molecular weight polyethylene fiber has achieved rapid development. Currently, the world's mainstream polyethylene fiber production technologies mainly include dry spinning and wet spinning.

[0003] Domestic wet-process technology is relatively mature and has been promoted and applied in dozens of domestic enterprises. The fibers produced by it have the characteristics of coarse denier, good uniformity, high strength and high modulus, which are suitable for application by downstream enterprises. At present, only Yizheng Chemical Fiber has achieved industrialization of dry-process technology, which has the characteristics of fine denier, softness, good uniformity, high strength and high modulus, and is widely used in downstream enterprises.

[0004] Judging from the current development trend of domestic technology and products, the residual solvent in wet-process products is slightly more than that in dry-process products. This is reflected in the fact that wet-process products have a relatively large fineness, the fiber is relatively hard, and it is not easy to fluff during downstream processing. It is easy to process and can be widely used in military and civilian fields. However, in fields such as medical devices that require high solvent residues, further deep processing is required to remove solvent residues. Therefore, in recent years, wet-process technology has been developed in the direction of fine denier, which on the one hand expands the application field, and on the other hand is also a need to improve quality. Since dry-process technology uses volatile solvents, the residual solvent in the product is relatively low, which is reflected in the product that the fineness is relatively fine, the weight is light, and it has the characteristics of high strength and high modulus, which can be widely used in military and civilian facilities. The fiber is soft and comfortable. Due to its fine fineness, it is easy to fluff during downstream processing and is not easy to process. Therefore, in recent years, dry-process technology has been developed in the direction of coarse denier, mainly to improve its easy processing performance in the downstream.

[0005] CN112609250A discloses a method for preparing ultra-high molecular weight polyethylene thick denier fiber monofilament by gel method, wherein ultra-high molecular weight polyethylene powder is mixed with white oil to prepare spinning solution pre-swelling material, and the pre-swelling material is kept in stirring state and heated; the pre-swelling material enters into a twin-screw extruder, and then enters into a spinning assembly to be spun through a spinneret, and cooled in a cooling water tank to obtain ultra-high molecular weight gel precursor; static balance; after spun, the precursor falls into a barrel in a cross-layered circular ring arrangement; the gel precursor after balancing treatment is extracted, dried, and hot-stretched; and finally wound to obtain ultra-high molecular weight polyethylene thick denier fiber monofilament. The preparation method disclosed in the invention can achieve a 10-fold increase in the fineness of the monofilament without reducing the strength, reaching 20-40 deniers, and its diameter is 0.038-0.070 mm. The original method of combining multiple fine denier monofilaments is replaced by thick denier monofilaments, which effectively eliminates the gaps between the fine denier monofilaments and maintains excellent strength and modulus. This method uses wet technology, and the single hole diameter of the spinneret is 1.5-2mm. It adopts a sudden cooling molding method, and then stands for a period of time to eliminate the internal stress of the original fiber before high-multiple stretching.

[0006] CN101575745A discloses a coarse polyester fiber and a production method thereof. The fiber has a single filament fineness range of 7-20 dtex, and the coarse denier polyester fiber does not include a polyester fiber with a total number of single filaments of one. The production method comprises: melting and extruding the dried polyester slices, extruding and shaping through a circular or special-shaped spinneret, cooling and solidifying with side-blown air, then subjecting to oiling and entanglement treatment, and finally winding and forming through a winding device, directly obtaining a finished highly oriented polyester fiber (FDY), or obtaining a semi-finished pre-oriented polyester fiber (POY), and the semi-finished pre-oriented polyester fiber (POY) is further processed to obtain a finished product. In addition, the production method of the product is simple, highly operable, and can also meet the needs of further processing.

[0007] CN101899722A discloses a method for preparing a high-denier polyvinyl alcohol monofilament fiber. The high-strength and high-modulus high-denier polyvinyl alcohol monofilament fiber is prepared by a solid-phase alcoholysis spinning method. The method is characterized in that low-alcoholysis degree polyvinyl alcohol is spun under the plasticization of a small amount of water to prepare the high-denier fiber at a relatively low temperature, thereby avoiding the extraction problem of using a plasticizer and the problem that the wet spinning method cannot produce high-denier (≥1000D) fibers. A small amount of water is added to make it a molten state, and the fiber is extruded by a single screw and then metered by a metering pump and extruded from a spinneret. A small amount of water can be removed by heating. After the fiber is dried, multi-stage stretched (10-16 times), and high-temperature tensile heat-set, a high-strength and high-modulus fiber is obtained, which makes up for the defects of the existing technology and commercially available products and meets the needs of civil engineering for concrete toughening and crack resistance. The method uses a device that is easy to use to swell polyethylene, and then transports it to one of two containers used alternately for stirring, and outputs it through the output port at the bottom of the container. There is still a concentration gradient in the container and there is sedimentation at the bottom. Therefore, the suspension cannot be output evenly and continuously, and the uniformity of the product in the subsequent process cannot be guaranteed.

[0008] CN102154749A discloses a method for preparing a thick and ultra-high molecular weight polyethylene fiber yarn, comprising: spraying a polyethylene solution through a spinneret and then entering a 100°C-150°C coagulation bath to quench into a gel fiber, wherein the spinneret comprises 20-50 groups of spinneret holes, each group of spinneret holes comprises 15-35 spinneret holes with a diameter of 0.7-1.0 mm; then extracting and drying the gel fiber and subsequently heat stretching the gel fiber to obtain the obtained product. The invention is simple to operate and has low requirements on equipment. The single fiber diameter of the prepared thick and ultra-high molecular weight polyethylene fiber yarn is 0.7-1.0 mm. The fiber yarn has high strength and is suitable for making high-strength ropes.

[0009] Due to the volatile nature of the solvent, dry technology can achieve high-speed stretching during the processing process, making the fiber finer. At present, the single-filament fineness of domestic dry-spinning products is basically 0.8-1.3dtex. If you want to obtain products with higher single-filament fineness, you need to make large-scale process adjustments to the existing dry-spinning technology. Summary of the invention

[0010] The purpose of the present invention is to overcome the problem of too fine fiber of ultra-high molecular weight polyethylene fiber prepared by dry spinning, and to provide a preparation method of ultra-high molecular weight polyethylene coarse denier fiber. The "skin-core" structure of the fiber can be first generated and then eliminated by cooling twice and then preheating, so as to avoid broken wire and hairy wire in the preparation process, and finally obtain ultra-high molecular weight polyethylene coarse denier fiber with large single fiber fineness and good mechanical properties.

[0011] In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a method for preparing ultra-high molecular weight polyethylene coarse denier fiber, wherein the spinning solution is extruded through an equipment to obtain gel filaments; the gel filaments are cooled twice, and then preheated, stretched, oiled and wound to obtain raw filaments; the raw filaments are subjected to multi-stage stretching to obtain ultra-high molecular weight polyethylene coarse denier fiber.

[0012] The second aspect of the present invention provides an ultra-high molecular weight polyethylene macrodenier fiber produced by the above method.

[0013] Through the above technical solution, the present invention has the following beneficial effects:

[0014] (1) The present invention uses a specific process, especially a double cooling and preheating process, to first generate and then eliminate the "skin-core" structure of the fiber, so that the solvent in the gel filaments is continuously precipitated during the preparation process, thereby avoiding the occurrence of broken and frizzy fibers caused by the "skin-core" structure of the gel filaments during the preparation process;

[0015] The first cooling is rapid cooling to form a gel filament with a solidified outside and a soft inside that has a "skin-core" structure; the second cooling is high-speed cold air deep cooling, which can solidify the gel filament and accelerate the precipitation of a large amount of solvent inside the gel filament; after two coolings, a solid gel filament with the "skin-core" structure basically eliminated is obtained, and preheating and softening can soften the solid gel filament, allowing the solvent to evaporate more fully, thereby improving the spinnability of the gel filament.

[0016] (2) After the solvent is precipitated, it can be returned to the aforementioned module for reuse, thus realizing the recycling of the solvent.

[0017] (3) The ultra-high molecular weight polyethylene coarse denier fiber finally prepared has large single fiber fineness and good mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of an embodiment of the fiber spinning system in the present invention.

[0019] Description of Reference Numerals

[0020] 1. Metering pump 2. Coagulation bath 3. Cold wire drawing machine 4. Cold wire drying cold box 5. Cold drawing machine 6. Wire drawing machine 7. Preheating tunnel 8. Wire drawing machine 9. Preheating and drying drawing box 10. Cold drawing machine 11. Drafting hot box 12. Cold drawing machine 13. Oiling machine 14. Winding machine DETAILED DESCRIPTION

[0021] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0022] The first aspect of the present invention provides a method for preparing ultra-high molecular weight polyethylene coarse denier fibers, wherein a spinning solution is extruded through an equipment to obtain gel fibers; the gel fibers are cooled twice, and then preheated, drawn, oiled and wound to obtain raw fibers; the raw fibers are subjected to multi-stage stretching to obtain ultra-high molecular weight polyethylene coarse denier fibers.

[0023] In the present invention, through specific processes, especially two cooling and then preheating processes, the "skin-core" structure of the fiber first appears and then disappears, so that the solvent in the gel filaments is continuously precipitated during the preparation process, thereby avoiding the occurrence of process breakage and hairy fibers caused by the "skin-core" structure of the gel filaments during the preparation process. After two coolings, solid gel filaments with the "skin-core" structure basically eliminated are obtained, and preheating causes the solid gel filaments to soften and melt, thereby obtaining stretchable gel filaments.

[0024] According to the present invention, the spinning solution comprises ultra-high molecular weight polyethylene and a solvent.

[0025] According to the present invention, based on the total mass of the spinning solution, the content of the ultra-high molecular weight polyethylene is 5-10wt%, and the content of the solvent is 90-95wt%.

[0026] In the present invention, when the contents of ultra-high molecular weight polyethylene and solvent meet the above ranges, broken and filamentary fibers are less likely to occur during processing, and the performance of the final coarse denier fiber is further improved, achieving a balance between single fiber fineness and processing difficulty.

[0027] Furthermore, based on the total mass of the spinning solution, the content of the ultra-high molecular weight polyethylene is 6-7wt%, and the content of the solvent is 93-94wt%.

[0028] In a particularly preferred embodiment of the present invention, the swelling temperature of the ultra-high molecular weight polyethylene is 95-100°C, preferably 96-98°C.

[0029] According to the present invention, the viscosity average molecular weight of the ultra-high molecular weight polyethylene is 1 million to 10 million g / mol.

[0030] In the present invention, when the viscosity average molecular weight of the ultra-high molecular weight polyethylene meets the above range, the branching degree is low, the polyethylene has good fluidity, and is not prone to breakage during processing.

[0031] Furthermore, the viscosity average molecular weight of the ultra-high molecular weight polyethylene is 4 million to 5 million g / mol.

[0032] According to the present invention, the solvent is selected from compounds containing a benzene ring.

[0033] According to the present invention, the boiling point of the solvent is 180-200°C, preferably 185-195°C.

[0034] According to the present invention, the solvent is selected from at least one of decahydronaphthalene, tetrahydronaphthalene and toluene, preferably decahydronaphthalene.

[0035] In the present invention, the decahydronaphthalene is the decahydronaphthalene commonly used in the art. In a particularly preferred embodiment, the decahydronaphthalene is trans-decahydronaphthalene, which is an isomer of decahydronaphthalene.

[0036] According to the present invention, the equipment comprises a twin-screw extruder, a metering pump, a spinning manifold and a spinneret.

[0037] According to the present invention, the extrusion process includes: the spinning solution is converted into a molten melt by the twin-screw extruder, then accurately metered by the metering pump, flows through the spinning manifold, and finally extruded from the spinneret.

[0038] According to the present invention, the temperature of the molten melt is 140-150°C.

[0039] In the present invention, when the gel filaments meet the temperature range above, more solvent is flashed out at the moment of leaving the spinneret, so that the solvent content in the gel filaments is even lower.

[0040] Furthermore, the molten melt temperature is 145-148°C.

[0041] In the present invention, the temperature of the spinning manifold is not limited. In a particularly preferred embodiment, the temperature of the spinning manifold is 160-200°C, preferably 170-190°C.

[0042] According to the present invention, the diameter of a single hole of the spinneret is 0.5-2 mm, preferably 1.2-1.5 mm.

[0043] According to the present invention, the aspect ratio of the spinneret is 4-10:1, preferably 6-8:1.

[0044] According to the present invention, a nozzle is arranged on the spinneret, and the stretching ratio of the nozzle is 5-20 times.

[0045] In the present invention, when the stretching ratio meets the above range, the content of solvent in the gel filaments can be controlled to be maintained in an appropriate range. When the stretching ratio of the nozzle is less than the above range, the gel filaments contain more solvent; when the stretching ratio of the nozzle is greater than the above range, hairy and broken filaments are likely to occur, affecting the performance of the final fiber.

[0046] Furthermore, the stretching ratio of the nozzle is 10-15 times.

[0047] According to the present invention, the extrusion rate is 2.5-5 m / min, preferably 3-3.5 m / min.

[0048] In the present invention, the assembly pressure in the spinneret is a common pressure in the art. In a particularly preferred embodiment, the assembly pressure in the spinneret is 0-1.8 MPa, preferably 0.5-1 MPa.

[0049] According to the present invention, the two cooling steps include a first cooling step and a second cooling step, wherein the first cooling step is solution cooling and the second cooling step is cold air cooling.

[0050] According to the present invention, the solution is cooled in a coagulation bath, and the temperature of the gel filaments when they are pulled out of the coagulation bath is ≤40°C, preferably ≤20°C.

[0051] In the present invention, the solution is cooled for rapid molding by sudden cooling, and the gel filaments pulled out of the coagulation bath are in an unstable state with solidified surface and soft interior, close to a "skin-core" structure, and as the surface of the gel filaments cools, solvent will continue to precipitate on the surface of the gel filaments.

[0052] In the present invention, the quenching solution in the coagulation bath is a conventional solution incompatible with the spinning aid, preferably selected from water, the solvent included in the spinning solution and a solution insoluble in the solvent, so as to facilitate the subsequent recycling of the solvent.

[0053] According to the present invention, the cold air cooling is carried out in a guide wire cold drawing machine, a guide wire drying cold box, and a cold drawing machine, and an air knife is arranged in the guide wire drying cold box.

[0054] In the present invention, the high-speed airflow generated by the wind knife in the cold air cooling deeply cools the gel filaments and blows away the solvent precipitated on the surface of the gel filaments, so that the solvent content inside the gel filaments is greatly reduced, the "skin-core" structure is basically eliminated, and solid gel filaments are obtained.

[0055] According to the present invention, the air outlet temperature of the air knife is -10°C to 10°C.

[0056] In the present application, the outlet air temperature of the specific air knife can cause the filaments to rapidly undergo deep cooling and solidification to form stable gel filaments, thereby accelerating the precipitation of a large amount of solvent inside the gel filaments.

[0057] Furthermore, the air outlet temperature of the air knife is -5°C to 0°C.

[0058] According to the present invention, the outlet wind speed of the wind knife is 50-100 m / s.

[0059] In the present application, the outlet wind speed of the specific air knife can remove the quenching solvent brought out from the coagulation bath on the fiber surface, and also dry the solvent precipitated from the gel fiber due to the cooling and shrinkage.

[0060] Furthermore, the outlet wind speed of the wind knife is 70-75m / s.

[0061] According to the present invention, the drafting ratio of the cold drafting machine is 0.8-1.2 times.

[0062] In the present invention, since the gel yarn will shrink to a certain extent in terms of long diameter after deep cold treatment, the specific drawing ratio of the cold drawing machine can prevent the yarn from breaking and hairy during the production process.

[0063] Furthermore, the drafting ratio of the cold drafting machine is 0.9-1 times.

[0064] According to the present invention, the preheating is carried out in a preheating tunnel, and the preheating temperature is 40-100°C.

[0065] In the present invention, the preheating can preheat and soften the solidified gel filaments, which is convenient for subsequent solvent volatilization and directional stretching, and improves the spinnability of the gel filaments.

[0066] Furthermore, the preheating temperature is 70-80°C.

[0067] According to the present invention, the stretching is carried out in a preheating and drying stretching box and a stretching hot box, and the stretching machine in the preheating and drying stretching box is a hot stretching machine provided with hot stretching rollers.

[0068] According to the present invention, the temperature of the preheating drying drawing box is 60-150°C, preferably 100-140°C.

[0069] In the present invention, the hot stretching roller is located inside the preheating and drying stretching box, and the temperatures of the two rollers are the same in the later stage.

[0070] According to the present invention, the stretching ratio of the hot stretching machine is 1-1.5 times, preferably 1-1.2 times.

[0071] According to the present invention, the temperature of the drawing hot box is 100-140°C, preferably 120-130°C.

[0072] According to the present invention, the stretching ratio of the stretching hot box is 1-2 times, preferably 1.2-1.5 times.

[0073] According to the present invention, the multi-stage stretching includes primary stretching, secondary stretching and tertiary stretching; the total stretching ratio of the multi-stage stretching is 7-10 times.

[0074] According to the present invention, the ratio of the primary stretching is 3-6 times, preferably 4-5 times; the temperature of the primary stretching is 138-142°C, preferably 140-142°C.

[0075] According to the present invention, the ratio of the secondary stretching is 1.2-1.6 times, preferably 1.3-1.5 times; the temperature of the secondary stretching is 142-145°C, preferably 143-144°C.

[0076] According to the present invention, the three-stage stretching ratio is 1-1.4 times, preferably 1.05-1.2 times; the three-stage stretching temperature is 144-148°C, preferably 145-148°C.

[0077] The second aspect of the present invention provides an ultra-high molecular weight polyethylene macrodenier fiber produced by the above method.

[0078] According to the present invention, the ultra-high molecular weight polyethylene coarse denier fiber has a solvent content of 900-14500 ppm, a single fiber fineness of 1-51 dtex, a breaking strength of ≥30 cN / dtex, and a Young's modulus of ≥1200 cN / dtex.

[0079] In the present invention, the solvent content increases the linear density of the fiber, thereby increasing the weight per unit length of the fiber. The solvent in the fiber will slowly evaporate in the later stage, resulting in a decrease in the linear density of the fiber. A high solvent content makes it easy to obtain a coarse denier fiber with a large single fiber fineness, but the solvent content is only one of the factors affecting the single fiber fineness.

[0080] Furthermore, the ultra-high molecular weight polyethylene coarse denier fiber has a solvent content of 3000-10000 ppm, a single fiber fineness of 1.5-3.8 dtex, a breaking strength of ≥35 cN / dtex, and a Young's modulus of ≥1300 cN / dtex.

[0081] Figure 1It is a structural diagram of a fiber spinning system. After the metering pump 1 meters the polyethylene spinning solution, it is extruded through a specific spinneret. The extruded gel filaments enter a coagulation bath 2 for rapid cooling; the cooled gel filaments are cooled twice in a guide wire cold drawing machine 3, a guide wire drying cold box 4 and a cold drawing machine 5; after two coolings, the gel filaments flow through a guide wire machine 6 and enter a preheating tunnel 7 for preheating and heating; they flow through a guide wire machine 8 and enter a preheating drying drawing box 9, and enter a drawing hot box 11 through a cold drawing machine 10 for drawing and solvent removal; the gel filaments after solvent removal flow through a cold drawing machine 12 and enter an oiling machine 13 for oiling, and are wound in a winder 14 to obtain raw filaments; the prepared raw filaments are then subjected to multi-stage stretching to ultimately be made into ultra-high molecular weight polyethylene coarse denier fibers.

[0082] The present invention will be described in detail below through examples.

[0083] Gel fiber diameter detection method: The equipment uses Cai Kang microscope CKC2000, eyepiece 10 times, and particle size analysis software DL-3000. Gel fiber samples are taken at the nozzle outlet, coagulation bath outlet, wire guide drying cold box outlet, preheating tunnel outlet, preheating drying drafting box outlet, drafting hot box outlet, winding outlet, and finished fiber winding outlet, and the diameter of the single fiber is measured under a 250 times field of view.

[0084] The method for detecting the mass ratio of ultra-high molecular weight polyethylene to solvent in gel yarn is as follows: 100 g of bundled gel yarn sample is taken at the nozzle outlet, coagulation bath outlet, wire guide drying cold box outlet, preheating tunnel outlet, preheating drying drawing box outlet, drawing hot box outlet, winding outlet, and finished fiber winding outlet, and dried for 3 hours under vacuum conditions of 140°C (the temperature is higher than the glass transition point of polyethylene, which will cause the polyethylene to melt and the internal solvent will not evaporate easily, resulting in distorted measurement results). After taking out, cool to room temperature and weigh, recorded as m1, the solvent content is 100-m1, and calculated according to the following formula:

[0085] Solvent:

[0086] The test method of single filament fineness of gel yarn and ultra-high molecular weight polyethylene coarse denier fiber is as follows: GB / T / 19975-2005 is used for testing, and the linear density of the bundle is measured to calculate the fineness of the single filament, and the fineness of the single filament = the fineness of the bundle fiber obtained by the test / the number of holes in the spinneret.

[0087] The detection method of the solvent content is as follows: the mass ratio of the ultra-high molecular weight polyethylene to the solvent in the gel filament is detected by three measurements and the average value is taken.

[0088] Testing method for breaking strength and Young's modulus of ultra-high molecular weight polyethylene coarse denier fiber: GB / T19975-2005 method is used for testing.

[0089] Ultra-high molecular weight polyethylene (average particle size of 250 μm, viscosity-average molecular weight of 4.25 million g / mol) was purchased from Shanghai Lianle Company;

[0090] The solvent was decahydronaphthalene (≧98% industrial grade, cis-trans ratio of 2:8), purchased from Zhongneng Chemical Company;

[0091] Deionized water and nitrogen were purchased from the external pipeline network of Nanhua Company.

[0092] Example 1

[0093] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 5 times, and the nozzle extrusion rate is 3.25m / min.

[0094] The temperature of the gel yarn when it is drawn out of the gel bath is 10°C, the air outlet temperature of the wind knife is -10°C, the air outlet speed of the wind knife is 50m / s, the stretching ratio of the cold stretching machine is 0.8 times, and it is preheated in the preheating tunnel at a preheating temperature of 100°C. The temperature of the preheating and drying stretching box is 130°C, the stretching ratio of the hot stretching machine is 1.1 times, the temperature of the stretching hot box is 140°C, and the stretching ratio of the stretching hot box is 1.2 times to obtain the raw yarn.

[0095] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0096] The analysis and test results of the gel silk / precursor silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 1.

[0097] Table 1

[0098]

[0099] Example 2

[0100] The spinneret has a length-to-diameter ratio of 6:1, 70 holes, a single hole diameter of 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 20 times, and the nozzle extrusion rate is 3.25m / min.

[0101] The temperature of the gel yarn when it is drawn out of the gel bath is 20°C, the air outlet temperature of the air knife is 10°C, the air outlet speed of the air knife is 80m / s, the stretching ratio of the cold stretching machine is 1, and it is preheated in the preheating tunnel at a temperature of 70°C. The temperature of the preheating and drying stretching box is 60°C, the stretching ratio of the hot stretching machine is 1.1, the temperature of the stretching hot box is 120°C, and the stretching ratio of the stretching hot box is 1.6 to obtain the raw yarn.

[0102] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 5 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.6 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.2 times, and the temperature of the tertiary stretching is 145°C.

[0103] The analysis and test results of the gel silk / precursor silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 2.

[0104] Table 2

[0105]

[0106] Example 3

[0107] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.2 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 8 times, and the nozzle extrusion rate is 3.25m / min.

[0108] The temperature of the gel yarn when it is drawn out of the gel bath is 10°C, the air outlet temperature of the wind knife is 0°C, the air outlet speed of the wind knife is 60m / s, the stretching ratio of the cold stretching machine is 0.9 times, and it is preheated in the preheating tunnel at a preheating temperature of 80°C. The temperature of the preheating and drying stretching box is 120°C, the stretching ratio of the hot stretching machine is 1.2 times, the temperature of the stretching hot box is 140°C, and the stretching ratio of the stretching hot box is 1.5 times to obtain the raw yarn.

[0109] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4.5 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.1 times, and the temperature of the tertiary stretching is 145°C.

[0110] The analysis and test results of the gel silk / precursor silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 3.

[0111] Table 3

[0112]

[0113] Example 4

[0114] The aspect ratio of the spinneret is 3:1, the number of holes is 70, the diameter of a single hole is 2 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.23MPa, the stretching ratio of the nozzle is 5 times, and the nozzle extrusion rate is 3.25m / min.

[0115] The temperature of the gel yarn when it is drawn out of the gel bath is 10°C, the air outlet temperature of the wind knife is -10°C, the air outlet speed of the wind knife is 70m / s, the stretching ratio of the cold stretching machine is 0.8 times, and it is preheated in the preheating tunnel at a preheating temperature of 100°C. The temperature of the preheating and drying stretching box is 135°C, the stretching ratio of the hot stretching machine is 1.1 times, the temperature of the stretching hot box is 140°C, and the stretching ratio of the stretching hot box is 1.2 times to obtain the raw yarn.

[0116] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.4 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0117] The analysis and test results of the gel silk / precursor silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 4.

[0118] Table 4

[0119]

[0120] Example 5

[0121] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 5 times, and the nozzle extrusion rate is 3.25m / min.

[0122] The temperature of the gel yarn when it is drawn out of the gel bath is 30°C, the air outlet speed of the wind knife is 50m / s, the air outlet temperature of the wind knife is -10°C, the stretching ratio of the cold stretching machine is 0.8 times, and it is preheated in the preheating tunnel at a preheating temperature of 100°C. The temperature of the preheating and drying stretching box is 130°C, the stretching ratio of the hot stretching machine is 1.1 times, the temperature of the stretching hot box is 140°C, and the stretching ratio of the stretching hot box is 1.2 times to obtain the raw yarn.

[0123] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0124] The analysis and test results of the gel silk / raw silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 5.

[0125] Table 5

[0126]

[0127] Example 6

[0128] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 5 times, and the nozzle extrusion rate is 3.25m / min.

[0129] The temperature of the gel yarn when it is drawn out of the gel bath is 10°C, the air outlet temperature of the wind knife is -10°C, the air outlet speed of the wind knife is 120m / s, the stretching ratio of the cold stretching machine is 0.8 times, and it is preheated in the preheating tunnel at a preheating temperature of 100°C. The temperature of the preheating and drying stretching box is 130°C, the stretching ratio of the hot stretching machine is 1.1 times, the temperature of the stretching hot box is 140°C, and the stretching ratio of the stretching hot box is 1.2 times to obtain the raw yarn.

[0130] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0131] The analysis and test results of the gel silk / precursor silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 6.

[0132] Table 6

[0133]

[0134] Example 7

[0135] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 10 times, and the nozzle extrusion rate is 3.25m / min.

[0136] The temperature of the gel yarn when it is drawn out of the gel bath is 10°C, the air outlet temperature of the wind knife is -10°C, the air outlet speed of the wind knife is 50m / s, the stretching ratio of the cold stretching machine is 0.8 times, and it is preheated in the preheating tunnel at a preheating temperature of 100°C. The temperature of the preheating and drying stretching box is 130°C, the stretching ratio of the hot stretching machine is 1.1 times, the temperature of the stretching hot box is 140°C, and the stretching ratio of the stretching hot box is 1.2 times to obtain the raw yarn.

[0137] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0138] The analysis and test results of the gel silk / raw silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 7.

[0139] Table 7

[0140]

[0141]

[0142] Example 8

[0143] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 140°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 10 times, and the nozzle extrusion rate is 3.25m / min.

[0144] The temperature of the gel yarn when it is drawn out of the gel bath is 10°C, the air outlet temperature of the wind knife is -10°C, the air outlet speed of the wind knife is 50m / s, the stretching ratio of the cold stretching machine is 0.8 times, and it is preheated in the preheating tunnel at a preheating temperature of 100°C. The temperature of the preheating and drying stretching box is 130°C, the stretching ratio of the hot stretching machine is 1.1 times, the temperature of the stretching hot box is 140°C, and the stretching ratio of the stretching hot box is 1.2 times to obtain the raw yarn.

[0145] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0146] The analysis and test results of the gel silk / raw silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 8.

[0147] Table 8

[0148]

[0149]

[0150] Comparative Example 1

[0151] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 5 times, and the nozzle extrusion rate is 3.25m / min.

[0152] The temperature of the gel yarn when it is pulled out of the gel bath is 10°C, and it is preheated in the preheating tunnel at a temperature of 100°C. The temperature of the preheating drying drawing box is 130°C, the drawing ratio of the hot drawing machine is 1.1 times, the temperature of the drawing hot box is 140°C, and the drawing ratio of the drawing hot box is 1.2 times to obtain the original yarn.

[0153] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0154] The analysis and test results of the gel silk / precursor silk / ultra-high molecular weight polyethylene coarse denier fiber are shown in Table 9.

[0155] Table 9

[0156]

[0157] The fiber is entangled in the preheating box of the tunnel. As the solvent on the fiber surface is brought to the drafting roller, the occasional broken filaments of the tow will be entangled on the drafting roller due to the surface tension of the solvent on the drafting roller, causing entanglement and breakage. At the same time, without the second cooling, the residual solvent in the fiber increases significantly, which cannot meet the fiber application requirements and also reduces the solvent recovery rate.

[0158] Comparative Example 2

[0159] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 5 times, and the nozzle extrusion rate is 3.25m / min.

[0160] The air outlet speed of the wind knife is 50m / s, the air outlet temperature of the wind knife is -10℃, the stretching ratio of the cold stretching machine is 0.8 times, and it is preheated in the preheating tunnel at a preheating temperature of 100℃. The temperature of the preheating and drying stretching box is 130℃, the stretching ratio of the hot stretching machine is 1.1 times, the temperature of the stretching hot box is 140℃, and the stretching ratio of the stretching hot box is 1.2 times to obtain the raw silk.

[0161] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0162] Normal production is impossible. The tension of the gel filament is extremely low under high temperature conditions. Affected by the high-speed wind direction of the wind knife, the gel filament breaks directly and the stretching conditions cannot be maintained.

[0163] Comparative Example 3

[0164] The aspect ratio of the spinneret is 6:1, the number of holes is 70, the diameter of a single hole is 1.5 mm, and based on the total mass of the spinning solution, the content of ultra-high molecular weight polyethylene is 6wt%, and the content of the solvent is 94wt%; the swelling temperature of the ultra-high molecular weight is 98°C; the melt temperature is 145°C; the assembly pressure is 1.25MPa, the stretching ratio of the nozzle is 5 times, and the nozzle extrusion rate is 3.25m / min.

[0165] The temperature of the gel yarn when it is drawn out of the gel bath is 10°C, the air outlet speed of the wind knife is 50m / s, the air outlet temperature of the wind knife is -10°C, the stretching ratio of the cold stretching machine is 0.8 times, the temperature of the stretching hot box is 140°C, and the stretching ratio of the stretching hot box is 1.2 times to obtain the raw yarn.

[0166] The raw silk is then subjected to a multi-stage stretching process, wherein the ratio of the primary stretching is 4 times, and the temperature of the primary stretching is 140°C; the ratio of the secondary stretching is 1.5 times, and the temperature of the secondary stretching is 144°C; the ratio of the tertiary stretching is 1.05 times, and the temperature of the tertiary stretching is 145°C.

[0167] The device could not run stably and the gel filaments were directly broken. The main reason was that the gel filaments were not softened and were in a "skin-core" structure. The inside was not dissolved, which caused the gel filaments to break once they were stretched in the subsequent stretching hot box.

[0168] The properties of the ultra-high molecular weight polyethylene coarse denier fibers obtained in the examples and comparative examples were tested, and the results are shown in Table 10.

[0169] Table 10

[0170] Solvent content (ppm) Breaking strength (cN / dtex) Young's modulus (cN / dtex) Example 1 5000 34.1 1330 Example 2 3500 35.3 1315 Example 3 4800 33.6 1302 Example 4 14000 29.8 1205 Example 5 7000 33.5 1258 Example 6 4800 34.7 1305 Example 7 900 36.8 1360 Example 8 1200 35.1 1325 Comparative Example 1 15000 28.9 1159 Comparative Example 2 - - - Comparative Example 3 - - -

[0171] “-” means that the preparation was not successful and could not be tested.

[0172] Comparing the embodiment with the comparative example, the ultra-high molecular weight polyethylene coarse denier fiber prepared by the present invention has large single filament fineness and good mechanical properties.

[0173] Comparing Example 1 with Example 4, when a coarser spinneret aperture is used, the single filament fineness can still be increased, but the residual solvent content in the fiber also increases, and the spinnability of the fiber decreases.

[0174] Compared with Example 5, the temperature of the condensation bath is high, which is not conducive to the rapid precipitation of the solvent, and will cause the residual solvent content of the raw silk and the subsequent finished fiber to increase. The single fiber fineness can meet the demand, but the high residual solvent content causes poor spinnability of the product, increased solvent loss, and reduced performance indicators, which is not conducive to maximizing product cost.

[0175] Comparing Example 1 with Example 6, the increased speed of the wind knife is beneficial to solvent recovery. The increased wind speed increases the precipitation and volatilization of solvent on the fiber surface, which is beneficial to improving the breaking strength of the product. However, if the wind speed is too high, it will increase the fiber variation rate, which will cause a decrease in product quality indicators.

[0176] Comparing Example 1 with Example 7, by increasing the nozzle stretching ratio, the mass ratio of the solvent to the ultra-high molecular weight polyethylene in the obtained coarse denier fiber decreases, and the solvent content in the final fiber is less, which is beneficial to solvent recovery. However, with the increase in the nozzle stretching ratio, the fiber fineness will also decrease, which is not conducive to the preparation of monofilaments with large fineness.

[0177] Comparing Example 7 with Example 8, lowering the spinning melt temperature is not conducive to the rapid flash volatilization of the solvent, resulting in an increase in the solvent content in the gel filaments, an increase in the mass ratio of the solvent to the ultra-high molecular weight polyethylene in the obtained coarse denier fiber, and an increase in the final solvent residue in the fiber.

[0178] Comparative Example 1 does not perform the second cooling step, Comparative Example 2 does not perform the first cooling step, and Comparative Example 3 does not perform the preheating step.

[0179] It can be seen from the results in the table that the double cooling and preheating adopted in the present invention can make the "skin-core" structure of the fiber appear first and then disappear in the preparation process, so that the solvent in the gel filaments is continuously precipitated during the preparation process, thereby avoiding the process of broken and frizzy filaments caused by the "skin-core" structure of the gel filaments during the preparation process. The ultra-high molecular weight polyethylene coarse denier fiber finally prepared has a large single filament fineness, a low solvent content in the fiber, and good mechanical properties, and can also realize the recovery and utilization of the solvent.

[0180] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing ultra-high molecular weight polyethylene coarse denier fiber, characterized in that: The spinning solution is extruded through the equipment to obtain gel filaments; the gel filaments are cooled twice, and then preheated, drawn, oiled and rolled to obtain raw filaments; the raw filaments are stretched in multiple stages to obtain ultra-high molecular weight polyethylene coarse denier fibers.

2. The preparation method according to claim 1, wherein The spinning solution comprises ultra-high molecular weight polyethylene and a solvent; Preferably, based on the total mass of the spinning solution, the content of the ultra-high molecular weight polyethylene is 5-10wt%, and the content of the solvent is 90-95wt%; preferably, the content of the ultra-high molecular weight polyethylene is 6-7wt%, and the content of the solvent is 93-94wt%; Preferably, the viscosity average molecular weight of the ultra-high molecular weight polyethylene is 1 million to 10 million g / mol, preferably 4 million to 5 million g / mol; Preferably, the solvent is selected from compounds containing a benzene ring; Preferably, the boiling point of the solvent is 180-200°C, preferably 185-195°C; Preferably, the solvent is selected from at least one of decahydronaphthalene, tetrahydronaphthalene and toluene, preferably decahydronaphthalene.

3. The preparation method according to claim 1 or 2, wherein The equipment comprises a twin-screw extruder, a metering pump, a spinning manifold and a spinneret; Preferably, the extrusion process includes: the spinning solution is converted into a molten melt by the twin-screw extruder, then accurately metered by the metering pump, flows through the spinning manifold, and finally extruded from the spinneret; Preferably, the temperature of the molten melt is 140-150°C, preferably 145-148°C; Preferably, the single hole diameter of the spinneret is 0.5-2 mm, preferably 1.2-1.5 mm; Preferably, the aspect ratio of the spinneret is 4-10:1, preferably 6-8:1; Preferably, a nozzle is provided on the spinneret, and the stretching ratio of the nozzle is 5-20 times, preferably 10-15 times; Preferably, the extrusion rate is 2.5-5 m / min, preferably 3-3.5 m / min.

4. The preparation method according to any one of claims 1 to 3, wherein The two cooling steps include a first cooling and a second cooling, wherein the first cooling is solution cooling, and the second cooling is cold air cooling.

5. The preparation method according to claim 4, wherein: The solution is cooled in a coagulation bath, and the temperature of the gel filaments when they are pulled out of the coagulation bath is ≤40°C, preferably ≤20°C.

6. The preparation method according to claim 4, wherein The cold air cooling is carried out in the guide wire cold drawing machine, the guide wire drying cold box, and the cold drawing machine, and the guide wire drying cold box is provided with an air knife; Preferably, the air outlet temperature of the wind knife is -10°C to 10°C, preferably -5°C to 0°C; the air outlet speed of the wind knife is 50-100m / s, preferably 70-75m / s; Preferably, the drafting ratio of the cold drafting machine is 0.8-1.2 times, preferably 0.9-1 times.

7. The preparation method according to any one of claims 1 to 6, wherein: The preheating is carried out in a preheating tunnel, and the preheating temperature is 40-100°C, preferably 70-80°C.

8. The preparation method according to any one of claims 1 to 7, wherein: The drawing is carried out in a preheating and drying drawing box and a drawing hot box, and the drawing machine in the preheating and drying drawing box is a hot drawing machine provided with a hot drawing roller; Preferably, the temperature of the preheating drying drafting box is 60-150°C, preferably 100-140°C; Preferably, the stretching ratio of the hot stretching machine is 1-1.5 times, preferably 1-1.2 times; Preferably, the temperature of the drawing hot box is 100-140°C, preferably 120-130°C; Preferably, the stretching ratio of the stretching hot box is 1-2 times, preferably 1.2-1.5 times.

9. The preparation method according to any one of claims 1 to 8, wherein: The multi-stage stretching includes primary stretching, secondary stretching and tertiary stretching; the total stretching ratio of the multi-stage stretching is 7-10 times; Preferably, the ratio of the primary stretching is 3-6 times, preferably 4-5 times; the temperature of the primary stretching is 138-142°C, preferably 140-142°C; Preferably, the ratio of the secondary stretching is 1.2-1.6 times, preferably 1.3-1.5 times; the temperature of the secondary stretching is 142-145°C, preferably 143-144°C; Preferably, the three-stage stretching ratio is 1-1.4 times, preferably 1.05-1.2 times; the three-stage stretching temperature is 144-148°C, preferably 145-148°C.

10. An ultra-high molecular weight polyethylene macrodenier fiber obtained by the method for preparing an ultra-high molecular weight polyethylene macrodenier fiber according to any one of claims 1 to 9; Preferably, the ultra-high molecular weight polyethylene coarse denier fiber has a solvent content of 900-14500 ppm, a single filament fineness of 1-5 dtex, a breaking strength of ≥30 cN / dtex, and a Young's modulus of ≥1200 cN / dtex; Preferably, the ultra-high molecular weight polyethylene coarse denier fiber has a solvent content of 3000-10000 ppm, a single fiber fineness of 1.5-3.8 dtex, a breaking strength of ≥35 cN / dtex, and a Young's modulus of ≥1300 cN / dtex.

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