Polyethylene resin for melt spinning, preparation thereof, and use thereof

Abstract

The present invention relates to a polyethylene resin for melt spinning, a preparation thereof, and a use thereof. The preparation method for a polyethylene resin comprises the following steps: (1) adding starting materials comprising a main catalyst, a cocatalyst, a diluent, and ethylene into a reactor for a polymerization reaction, and obtaining a slurry-like blend containing a resin and the diluent; (2) washing the slurry-like blend with a purified diluent during discharge, followed by solid-liquid separation; and (3) drying the resin after solid-liquid separation, and obtaining a polyethylene resin product. Compared with the existing technology, the polyethylene resin prepared by the present invention has a low crystallization point and is resistant to filament breakage during subsequent spinning. Moreover, said resin can be directly stretched and oriented in a hot passage at a spinneret outlet to obtain a final fiber product, or is further processed by multi-stage hot roll stretching to obtain a fiber product. The fiber product can achieve a strength greater than 15 cN / dtex, further improving the efficiency of melt spinning high-performance fibers.

Description

A polyethylene resin for melt spinning, its preparation and application Technical Field

[0001] This invention belongs to the field of polymer material preparation technology, and relates to a polyethylene resin for melt spinning, its preparation and application. Background Technology

[0002] In recent years, the use of high-performance fibers in the civilian sector has gradually increased, and they can be applied to high-end fiber products, with wide applications in medical, fishing, and protective equipment fields. Commonly used ultra-high molecular weight polyethylene fibers are relatively limited in civilian applications due to high cost, diluent residue, and complex processing. Meanwhile, low-cost, diluent-free medium-strength fiber products are increasingly favored in the civilian high-performance fiber sector. These medium-strength fiber products are mainly obtained using melt spinning technology.

[0003] Currently, Chinese patents CN1646739A, CN109521054B, CN111494976B, CN115339088A, and CN115029810A have all disclosed methods for preparing high-performance fibers using polyethylene resin with a narrow molecular weight distribution. However, these methods all require multi-stage stretching after the fibers are ejected from the spinneret, wound, cooled, and then heated. The fiber preparation process is lengthy, and there are also crystal point problems during subsequent melt spinning. In the process of spinning coarse denier fibers, this type of spinning method only affects the spinning performance, but in the process of spinning fine denier fibers, it may even directly lead to fiber breakage. This is the main reason why the fiber preparation methods described in these patents have not yet been industrialized in China.

[0004] Therefore, to address the above issues, it is necessary to develop a high-performance polyethylene fiber melt spinning resin that is suitable for industrial production, has low impurity content in raw materials, and can further simplify the spinning process. Summary of the Invention

[0005] The purpose of this invention is to provide a polyethylene resin for melt spinning, its preparation and application, which significantly reduces crystal points and fiber breakage rate during the spinning process, and enables a stable high-performance fiber melt spinning production process.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing polyethylene resin for melt spinning, comprising the following steps:

[0008] (1) Raw materials including main catalyst, co-catalyst, diluent and ethylene are added to the reactor to carry out polymerization reaction to obtain a slurry-like blend containing resin and diluent.

[0009] (2) The slurry-like blend is washed with a purified diluent during the discharge process, and then the solid and liquid are separated.

[0010] (3) After the solid-liquid separation, the resin is dried to obtain polyethylene resin product.

[0011] Furthermore, the main catalyst is one or a combination of several of the following: a single-active-center catalyst and a Ziegler-Natta system catalyst.

[0012] The co-catalyst is one or a mixture of several of triethylaluminum, triisobutylaluminum, and diethylaluminum chloride;

[0013] The diluent is a saturated hydrocarbon with a boiling point of -20°C to 70°C.

[0014] In this invention, by further optimizing the catalyst and other components, a polyethylene resin with a narrower molecular weight distribution can be polymerized. This allows for the provision of certain melt strength and spinnability during the post-spinning process, while simultaneously achieving higher mechanical properties of the fiber products, thus enabling the products to meet the requirements for use in the field of higher performance fibers.

[0015] Furthermore, the diluent is one or a mixture of several of the following: n-hexane, isobutane, isopentane, and cyclohexane.

[0016] Furthermore, the polymerization temperature is 50℃-90℃, and the pressure is 0.8-4MPa.

[0017] Furthermore, in step (2), the purification process of the diluent includes deweighting and distillation, so that the purity of the diluent reaches 99.8% or higher. Here, the specific processes and related parameters of deweighting and distillation are conventional techniques in the field.

[0018] Furthermore, in step (2), the amount of purified diluent used is more than 10 wt% of the output of the slurry-like blend.

[0019] Furthermore, solid-liquid separation can be achieved through pressure filtration or centrifugation.

[0020] Furthermore, the drying process can be carried out using any one of the following methods: hot nitrogen drying, drying after extraction with a low-boiling-point oil, or drying after washing with a fresh diluent. Specifically, the drying temperature can be between 60 and 130°C.

[0021] Furthermore, the diluent obtained after solid-liquid separation is purified and then recycled to step (2) for washing the discharged material.

[0022] Furthermore, the reactor can be a loop reactor or a batch reactor, etc.

[0023] On the other hand, the present invention provides a polyethylene resin for melt spinning, which is prepared by any of the preparation methods described above. Specifically, the obtained polyethylene resin product (7) meets the molecular structure requirements of a weight-average molecular weight of 150,000 to 900,000 and a molecular weight distribution of less than 4.0.

[0024] In a third aspect, the present invention provides an application of a polyethylene resin for melt spinning in the preparation of high-performance polyethylene fiber products.

[0025] In a fourth aspect, the present invention provides a method for preparing high-performance polyethylene fibers based on melt spinning, comprising the following steps:

[0026] (1) Raw materials including main catalyst, co-catalyst, diluent and ethylene are added to the reactor to carry out polymerization reaction to obtain a slurry-like blend containing resin and diluent.

[0027] (2) The slurry-like blend is washed with a purified diluent during the discharge process, and then the solid and liquid are separated.

[0028] (3) After the solid-liquid separation, the resin is dried to obtain polyethylene resin product;

[0029] (4) The obtained polyethylene resin product is used as polyethylene raw material, and after being compounded with processing aids including antioxidants and lubricants, it is fed into a screw extruder for melt extrusion. The fibers are then extruded through a spinneret and directly stretched and oriented in a hot channel connected to the outlet of the spinneret to obtain fiber products.

[0030] Furthermore, the raw materials used in the process of preparing the polyethylene resin product can be selected from the aforementioned methods.

[0031] Furthermore, the processing aids used here can be those commonly used in the preparation of polyethylene fibers. For example, antioxidants can be 2,6-di-tert-butyl-p-cresol, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], etc., and lubricants can be zinc stearate, calcium stearate, etc. In addition to antioxidants and lubricants, other processing aids can be introduced as needed.

[0032] Furthermore, the temperature of the spinneret is 220–260°C.

[0033] Furthermore, the heated passage is preferably divided into two spaced-apart sections, which can be continuous temperature sections or spaced 1-5m apart. More preferably, two or more spaced-apart sections are used. When there are two spaced-apart sections, the temperature of the first section is higher than the temperature of the second section, and the temperature of the second section can be divided into variable multi-level temperatures. For example, the temperature of the first section can be 150-170°C, and the temperature of the second section can be a three-level temperature of 90-160°C. Simultaneously, the fiber residence time in the first section is 0.5-120 seconds, and the fiber residence time in the second section is 0.5-180 seconds.

[0034] Furthermore, after direct orientation stretching in the hot tunnel, it can be further stretched in multiple stages by hot rollers.

[0035] This invention, through research, has discovered that a major problem in existing melt spinning processes lies in the crystal point issue caused by impurities in the resin raw materials. Therefore, this invention employs a slurry reactor to polymerize polyethylene, adding a purified diluent at the discharge line for washing, followed by solid-liquid separation to separate the diluent before high-temperature drying. This invention has found that the melt-spinning-specific resin obtained through this method significantly reduces trace impurities generated during the ethylene polymerization reaction in the spinning resin. Furthermore, the polyethylene resin treated using this method results in a significantly reduced crystal point content and a substantial decrease in filament breakage rate in the spun fibers.

[0036] Furthermore, this invention reveals a surprising discovery: the polyethylene resin polymerized using the above process exhibits significantly enhanced fiber melt strength after exiting the spinneret during melt spinning. After the polyethylene melt is extruded from the spinneret, it can directly pass through a hot tunnel at high temperature, where it can undergo orientation stretching. Following orientation stretching, it can be directly wound to obtain a high-performance melt-spun fiber product. This eliminates the need for cooling and solidifying the melt after exiting the spinneret, followed by multi-stage stretching to obtain the fiber product, thus greatly simplifying the overall process.

[0037] Meanwhile, in the spinning process of the polyethylene resin prepared by this invention, if the length of the hot channel is insufficient, the problem of insufficient stretching ratio can be further compensated by hot roller stretching. Taking advantage of the improved resin melt strength, the floor space required for the entire melt spinning process can be significantly reduced, the process can be simplified, and the preparation cost of high-performance fiber melt spinning can be further reduced.

[0038] In the solid-liquid separation unit of this invention, low-boiling-point diluents can be separated using low-temperature and high-pressure methods to prevent vaporization during the separation process.

[0039] In this invention, the amount of washing diluent used in the discharge line is more than 10% of the discharge mass ratio. As the amount of washing diluent added increases, the spinnability of the obtained resin increases accordingly.

[0040] The resin synthesized in this invention has the following advantages over existing melt spinning resins:

[0041] 1) The number of crystal points and the breakage rate are greatly reduced during the spinning process, which can form a stable high-performance fiber melt spinning production process.

[0042] 2) Improvements in resins have enabled a simplified melt spinning process, significantly reducing the production cost and floor space required for high-performance fiber melt spinning.

[0043] 3) Improved resin preparation process significantly enhances the quality of high-performance fibers obtained through spinning. Attached Figure Description

[0044] Figure 1 is a picture of the fiber product prepared in Comparative Example 3;

[0045] Figure 2 shows a picture of the fiber product prepared in Comparative Example 2;

[0046] Figure 3 is a picture of the fibers entering the hot channel from the spinneret in Example 1. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0048] In the following embodiments, polyethylene resin can be obtained by ethylene polymerization using a single-active-center polyethylene catalyst, including supported and unsupported metallocene catalysts or non-metallocene catalysts. The catalysts described in patents CN109306029A and CN116535548A can be used. Specifically, the preparation process of the polyethylene raw material in this embodiment is as follows:

[0049] (1) Add methanol and original support Mg(OH)2 in a 5:1 ratio to a reaction flask, heat to 100℃, add diisobutyl phthalate, stir at high speed (500 rpm) for 4 hours, and after the reaction is complete, quickly press the resulting mixture into a large amount of -15℃ hexane to solidify, obtaining a solid. Place the obtained solid under a nitrogen atmosphere and heat to 60℃ for 5 hours to obtain the desired support Mg1, with an average particle size of 150 μm and a specific surface area of ​​450 m² / g. Dissolve the metal catalyst in toluene, add triethylaluminum, and stir evenly to obtain a catalyst solution; add the support Mg1 and stir evenly to obtain the supported catalyst C1.

[0050] (2) Weigh 0.5g of ammonium bifluoride and dissolve it in 20mL of water. Add the resulting colorless and clear liquid dropwise to 10g of silica gel (Sylopol 955) and dry it in an oven at 100℃. After the water has evaporated, calcine the mixture at 600℃ under a nitrogen atmosphere for 3 hours. After cooling, add 0.2g of triethylaluminum and continue the reaction to obtain the active silica gel carrier S1.

[0051] Under argon protection, 5.0 g of active silica gel support S1 was suspended in 5 mL of toluene in a 100 mL reaction flask. 10.0 mg of phenoxyimine zirconium complex Zr5 and 10.0 mg of bis(cyclopentadienyl)zirconia dichloride were weighed and dissolved in 5.0 mL of toluene. This mixture was added to the toluene suspension of active silica gel support S1, and the reaction was stirred at room temperature for 1 hour. After filtration, the mixture was washed twice with toluene and dried under vacuum to obtain catalyst powder C2.

[0052] The antioxidant used was obtained by mixing antioxidant 1010 and antioxidant PS802 at a mass ratio of 2:8.

[0053] Test method for fiber tensile properties: The tensile properties of the fiber are tested according to the method of GB / T19975-2005.

[0054] Unless otherwise specified, all other raw materials or processing techniques are commercially available and conventional in the field.

[0055] Example 1

[0056] Polyethylene catalyst, triethylaluminum, and n-hexane were added to 7m 3 In a batch reactor, 30g of catalyst C1, 540g of triethylaluminum, and 3.6 tons of n-hexane were used. After stirring, the reactor was heated to 80°C, and ethylene gas was introduced to maintain a reactor pressure of 1 MPa. After 3 hours of reaction, the ethylene supply was stopped, and after the pressure decreased, the slurry reactants were transferred to a filter press. Purified n-hexane solvent was added at a rate of 10 tons / hour before the filter press. The purified n-hexane solvent and the slurry reactants were then subjected to solid-liquid separation through the filter press. The separated wet polyethylene material was dried by nitrogen purging at 90°C to obtain dry polyethylene material. The weight-average molecular weight of the obtained dry material was 150,000, and the molecular weight distribution was 2.5.

[0057] Polyethylene dry material is compounded with antioxidant, zinc stearate, and calcium stearate in a ratio of 99:0.4:0.3:0.3 (by mass) and then fed into a screw extruder for extrusion. The screw extruder barrel is divided into five sections, each with a temperature of 100℃, 190℃, 190℃, 190℃, and 190℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two continuous sections. The first section has a temperature of 160℃ and a length of 8m. The second section has three temperature levels: 160℃, 140℃, and 120℃, with lengths of 3m, 4m, and 4m respectively. After passing through the spinneret and hot runner, the fibers are directly wound at a speed of 500m / min, without the need for cooling or multi-stage stretching processes to obtain the final fiber product. The fiber tensile strength reaches 15cN / dtex.

[0058] Example 2

[0059] The loop reactor was filled with isobutane and heated to 70°C, with a reactor pressure of 4.1 MPa. The axial flow pump was started, and ethylene, catalyst C1, triisobutylaluminum, and isobutane were added simultaneously. The ethylene addition rate was 3 tons / hour, isobutane 5.5 tons / hour, catalyst 0.4 kg / hour, and triisobutylaluminum 0.4 kg / hour. The loop slurry discharge rate was approximately 8.5 tons / hour. Purified isobutane was injected at the discharge port at a rate of 10 tons / hour, and the slurry was subjected to solid-liquid separation by pressure filtration. The separated wet material entered a flash tank for flash evaporation and then entered a degassing chamber. After purging with 60°C nitrogen, the material was discharged. The dry material had a weight-average molecular weight of 250,000 and a molecular weight distribution of 2.5.

[0060] Polyethylene dry material is compounded with antioxidants, zinc stearate, and calcium stearate in a ratio of 99:0.4:0.3:0.3 and then fed into a screw extruder for extrusion. The screw extruder barrel is divided into five sections, each with a temperature of 100℃, 190℃, 190℃, 190℃, and 190℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two sections 1m apart. The first section has a temperature of 160℃ and a length of 6m, while the second section has a temperature of 130℃ and a length of 8m. After passing through the spinneret and hot runner, the fibers are directly wound at a speed of 300m / min, without the need for cooling or multi-stage stretching processes to obtain the final fiber product. The fiber tensile strength reaches 18cN / dtex.

[0061] Example 3

[0062] The loop reactor was filled with n-hexane and heated to 60°C, with a reactor pressure of 2 MPa. An axial flow pump was started, and ethylene, catalyst C2, and diethylaluminum chloride were added simultaneously. The ethylene addition rate was 3 tons / hour, the n-hexane addition rate was 5.5 tons / hour, the catalyst addition rate was 0.4 kg / hour, and the diethylaluminum chloride addition rate was 0.4 kg / hour. The loop slurry discharge rate was approximately 8.5 tons / hour. Purified n-hexane was injected at the discharge port at a rate of 8 tons / hour, and the slurry was separated into solid and liquid phases by centrifugation. The separated wet material entered a ribbon dryer. 120°C steam was introduced into the ribbon and wall jacket of the dryer, while 90°C nitrogen was introduced into the dryer. The dryer discharged the material, which was then pneumatically conveyed to obtain dry material. The weight-average molecular weight of the dry material was 900,000, and the molecular weight distribution was 3.2.

[0063] Polyethylene dry material is compounded with antioxidants, zinc stearate, calcium stearate, and polyethylene wax in a ratio of 98:0.4:0.3:0.3:1 and then fed into a screw extruder for extrusion. The screw extruder barrel temperature is divided into five sections, each with a temperature of 100℃, 200℃, 200℃, 200℃, and 200℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two continuous sections. The first section has a temperature of 190℃ and a length of 10m. The second section has three temperature levels: 140℃, 150℃, and 130℃, with lengths of 5m, 7m, and 6m respectively. After passing through the spinneret and the hot runner, the fibers are stretched by hot rollers at a temperature of 130℃, stretched 2.5 times, and then wound at a speed of 200m / min. The final fiber product can be obtained without cooling and multi-stage stretching processes in a hot box. The fiber tensile strength reaches 23 cN / dtex.

[0064] Example 4

[0065] Polyethylene catalyst, triethylaluminum, n-hexane, and other raw materials were added to 7m 3 In a batch reactor, 30g of catalyst C2, 240g of triisobutylaluminum, 300g of triethylaluminum, and 3.6 tons of n-hexane were added. After stirring, the reactor was heated to 80°C, ethylene gas was introduced, and the reactor pressure was maintained at 4 MPa. After 3 hours of reaction, the ethylene supply was stopped, and the slurry reactants were transferred to a filter press. Purified isobutane solvent was added at a rate of 10 tons / hour before the filter press. The purified isobutane solvent and the slurry reactants were extracted and separated into solid and liquid phases by passing them through the filter press. The separated wet polyethylene material was flash-evaporated in a flash tank and then dried by nitrogen purging at 90°C to obtain dry polyethylene material. The weight-average molecular weight of the obtained dry material was 400,000, and the molecular weight distribution was 3.9.

[0066] Polyethylene dry material is compounded with antioxidants, zinc stearate, calcium stearate, and white oil in a ratio of 98.5:0.4:0.3:0.3:0.5 and then fed into a screw extruder for extrusion. The screw extruder barrel temperature is divided into five sections, each with a temperature of 100℃, 190℃, 190℃, 190℃, and 190℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two sections 2m apart. The first section has a temperature of 160℃ and a length of 8m. The second section has two consecutive temperature levels of 140℃ and 120℃, with lengths of 4m and 4m respectively. After passing through a spinneret and a heated tunnel, the fibers are stretched by hot rollers at a temperature of 130°C, increasing in length by 1.5 times. They are then wound at a speed of 300 m / min, obtaining the final fiber product without the need for cooling or multi-stage stretching processes. The fiber tensile strength reaches 18 cN / dtex.

[0067] Example 5

[0068] The loop reactor was filled with n-hexane and heated to 60°C, with a reactor pressure of 4 MPa. The axial flow pump was started, and ethylene, catalyst C2, and diethylaluminum chloride were added simultaneously. The ethylene addition rate was 3 tons / hour, the n-hexane addition rate was 5.5 tons / hour, the catalyst addition rate was 0.4 kg / hour, and the diethylaluminum chloride addition rate was 0.4 kg / hour. The loop reactor slurry discharge rate was approximately 8.5 tons / hour. Purified isobutane was injected at the discharge port at a rate of 20 tons / hour, and the slurry was separated into solid and liquid phases by centrifugation. The separated wet material entered a flash tank for flash evaporation and then entered a degassing chamber. After purging with 60°C nitrogen gas, the dry material was obtained by pneumatic conveying. The weight-average molecular weight of the dry material was 900,000, and the molecular weight distribution was 3.2.

[0069] Polyethylene dry material is compounded with antioxidants, zinc stearate, calcium stearate, and polyethylene wax in a ratio of 98:0.4:0.3:0.3:1 and then fed into a screw extruder for extrusion. The screw extruder barrel temperature is divided into five sections, each with a temperature of 100℃, 200℃, 200℃, 200℃, and 200℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two continuous sections. The first section has a temperature of 160℃ and a length of 5m. The second section has three temperature levels: 140℃, 130℃, and 90℃, with lengths of 3m, 4m, and 5m respectively. After passing through the spinneret and the hot runner, the fibers are stretched by hot rollers at a temperature of 130℃, stretched 2.5 times, and then wound at a speed of 200m / min. The final fiber product can be obtained without cooling and multi-stage stretching processes in a hot box. The fiber tensile strength reaches 25 cN / dtex.

[0070] Comparative Example 1

[0071] The same polyethylene resin raw material polymerization method as in Example 1 was used, but purified n-hexane was not added to the discharge end, and other parameters and operations were the same.

[0072] Polyethylene dry material is compounded with antioxidants, zinc stearate, and calcium stearate in a ratio of 99:0.4:0.3:0.3 and then fed into a screw extruder for extrusion. The screw extruder barrel temperature is divided into five sections, each with a temperature of 100℃, 190℃, 190℃, 190℃, and 190℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two continuous sections. The first section has a temperature of 160℃ and a length of 8m. The second section has three temperature levels: 160℃, 140℃, and 120℃, with lengths of 3m, 4m, and 4m respectively. Fiber breakage occurs after passing through the spinneret and hot runner, making direct winding impossible.

[0073] After passing through the spinneret, the fiber is wound directly at a speed of 200 m / min without going through the heating tunnel. Then, the wound fiber is unwound at a speed of 10 m / min and passed through the first heating box (temperature 120℃, length 15m), then wound at a speed of 30 m / min. The wound fiber is then unwound at a speed of 20 m / min and passed through the second heating box (temperature 130℃, length 18m), then wound at a speed of 46 m / min, resulting in a multi-stage stretched fiber with a stretch ratio of 7. The tensile strength of the obtained fiber is 15 cN / dtex.

[0074] Comparative Example 2

[0075] Using the same polyethylene resin raw material polymerization method as in Example 2, the slurry reactants and the supplemented purified isobutane were directly subjected to flash evaporation and degassing to obtain the dried raw material without solid-liquid separation.

[0076] Polyethylene dry material is compounded with antioxidants, zinc stearate, and calcium stearate in a ratio of 99:0.4:0.3:0.3 and then fed into a screw extruder for extrusion. The screw extruder barrel temperature is divided into five sections, each with a temperature of 100℃, 190℃, 190℃, 190℃, and 190℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two sections 1m apart. The first section has a temperature of 160℃ and a length of 6m, while the second section has a temperature of 130℃ and a length of 8m. Fiber breakage occurs after passing through the spinneret and the hot runner, making direct winding impossible.

[0077] After passing through the spinneret, the fiber is wound directly at a speed of 200 m / min without going through the heating tunnel. Then, the wound fiber is unwound at a speed of 10 m / min and passed through the first heating box (heating box temperature 120℃, length 12m), then wound at a speed of 30 m / min. The wound fiber is then unwound at a speed of 20 m / min and passed through the second heating box (heating box temperature 125℃, length 18m), then wound at a speed of 46 m / min, resulting in multi-stage stretched fiber with a stretch ratio of 7. The fiber contains a small number of crystal points and a small number of broken fibers.

[0078] Comparative Example 3

[0079] The same polyethylene resin raw material polymerization method as in Example 1 was used, but there was no deweighting treatment at the back end of the hexane separation (i.e., it was directly recycled and washed without purification treatment), and other parameters and operations were the same.

[0080] Polyethylene dry material is compounded with antioxidants, zinc stearate, and calcium stearate in a ratio of 99:0.4:0.3:0.3 and then fed into a screw extruder for extrusion. The screw extruder barrel temperature is divided into five sections, each with a temperature of 100℃, 190℃, 190℃, 190℃, and 190℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two continuous sections. The first section has a temperature of 160℃ and a length of 8m. The second section has three temperature levels: 160℃, 140℃, and 120℃, with lengths of 3m, 4m, and 4m respectively. Fiber breakage occurs after passing through the spinneret and hot runner, making direct winding impossible.

[0081] In addition, after the fiber passes through the spinneret, it is directly wound at a speed of 200 m / min without going through the heated tunnel. The wound fiber is then unwound at a speed of 10 m / min and passed through the first heated box (temperature 120°C, length 15 m), wound at a speed of 20 m / min, and then unwound again at a speed of 20 m / min and passed through the second heated box (temperature 125°C, length 18 m, winding at a speed of 50 m / min). This process yields multi-stage stretched fibers with a stretch ratio of 5, resulting in fibers with numerous crystal points and a large number of broken fibers.

[0082] Comparative Example 4

[0083] The same polyethylene resin raw material polymerization method as in Example 1 was used, with a polymerization temperature of 90°C and all other parameters and operations being identical. A resin with a weight-average molecular weight of 100,000 and a molecular weight distribution of 2.8 was obtained.

[0084] Polyethylene dry material is compounded with antioxidants, zinc stearate, and calcium stearate in a ratio of 99:0.4:0.3:0.3 and then fed into a screw extruder for extrusion. The screw extruder barrel temperature is divided into five sections, each with a temperature of 100℃, 190℃, 190℃, 190℃, and 190℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two continuous sections. The first section has a temperature of 160℃ and a length of 8m. The second section has three temperature levels: 160℃, 140℃, and 120℃, with lengths of 3m, 4m, and 4m respectively. The fibers are directly wound after passing through the spinneret and hot runner, without the need for cooling or multi-stage stretching processes to obtain the final fiber product. The fiber tensile strength is only 11cN / dtex.

[0085] Comparative Example 5

[0086] Ethylene polymerization was carried out in a gas-phase fluidized bed reactor, with ethylene, catalyst C1, triisobutylaluminum, isobutane, and other raw materials added. The ethylene addition rate was 3 tons / hour, the catalyst addition rate was 0.4 kg / hour, and the triisobutylaluminum addition rate was 0.4 kg / hour. After degassing, the dry material obtained from the gas-phase reactor had a weight-average molecular weight of 230,000 and a molecular weight distribution of 2.7.

[0087] Polyethylene dry material is compounded with antioxidants, zinc stearate, and calcium stearate in a ratio of 99:0.4:0.3:0.3 and then fed into a screw extruder for extrusion. The screw extruder barrel temperature is divided into five sections, each with a temperature of 100℃, 190℃, 190℃, 190℃, and 190℃. Fibers are extruded through a spinneret at a temperature of 240℃. The spinneret outlet connects to a hot runner, which is divided into two continuous sections. The first section has a temperature of 160℃ and a length of 8m. The second section has three temperature levels: 160℃, 140℃, and 120℃, with lengths of 3m, 4m, and 4m respectively. Fiber breakage occurs after passing through the spinneret and hot runner, making direct winding impossible.

[0088] After passing through the spinneret, the fiber is wound directly at a speed of 200 m / min without going through the heating tunnel. The wound fiber is then unwound at a speed of 10 m / min, passed through the first heating box (heating box temperature 120℃, length 12 m), and wound at a speed of 30 m / min. The wound fiber is then unwound again at a speed of 20 m / min, passed through the second heating box (heating box temperature 130℃, length 18 m), and wound at a speed of 46 m / min, resulting in a multi-stage stretched fiber with a stretch ratio of 7. The resulting fiber contains a small number of crystal points and a small number of broken fibers.

[0089] Table 1 Performance data of each embodiment and comparative example Note: The circled areas in Figure 2 represent regions with obvious crystal points.

[0090] As can be seen from the table above and Figures 1 and 2, the resin polymerized using the specific polymerization method of this invention can significantly simplify the melting spinning process. It transforms the production model from one extrusion line plus more than ten post-spun yarns to a model where production can be completed with just one extrusion line, reducing costs and eliminating the problems of crystal points and filament breakage during spinning, thus solving the industrialization problem of high-performance fiber melting spinning. In contrast, resins polymerized using traditional gas-phase reactors or methods not employed in this invention suffer from crystal points and filament breakage, affecting fiber quality and hindering further industrialization of fiber products.

[0091] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing polyethylene resin for melt spinning, characterized in that, Includes the following steps: (1) Raw materials including main catalyst, co-catalyst, diluent and ethylene are added to the reactor to carry out polymerization reaction to obtain a slurry-like blend containing resin and diluent. (2) The slurry-like blend is washed with a purified diluent during the discharge process, and then the solid and liquid are separated. (3) After the solid-liquid separation, the resin is dried to obtain polyethylene resin product.

2. The method for preparing polyethylene resin for melt spinning according to claim 1, characterized in that, The main catalyst is one or a combination of several of the following: a single active site catalyst and a Ziegler-Natta system catalyst. The co-catalyst is one or a mixture of several of triethylaluminum, triisobutylaluminum, and diethylaluminum chloride; The diluent is a saturated hydrocarbon with a boiling point of -20°C to 70°C.

3. The method for preparing polyethylene resin for melt spinning according to claim 1, characterized in that, The diluent is one or a mixture of several of the following: n-hexane, isobutane, isopentane, and cyclohexane.

4. The method for preparing polyethylene resin for melt spinning according to claim 1, characterized in that, In step (2), the purification process of the diluent includes deweighting and distillation to achieve a diluent purity of 99.8% or higher.

5. The method for preparing polyethylene resin for melt spinning according to claim 1, characterized in that, In step (2), the amount of purified diluent used is more than 10 wt% of the output of the slurry-like blend.

6. The method for preparing polyethylene resin for melt spinning according to claim 1, characterized in that, Solid-liquid separation methods include pressure filtration or centrifugation; The drying process can be any one of the following: hot nitrogen drying, drying after extraction with low-boiling-point oil, or drying after washing with fresh diluent.

7. The method for preparing polyethylene resin for melt spinning according to claim 1, characterized in that, After solid-liquid separation, the diluent obtained is purified and then recycled to step (2) for washing the output.

8. A polyethylene resin for melt spinning, which is prepared by the preparation method according to any one of claims 1-7.

9. The application of the polyethylene resin for melt spinning as described in claim 8 in the preparation of high-performance polyethylene fiber products.

10. A method for preparing high-performance polyethylene fibers based on melt spinning, characterized in that, Includes the following steps: (1) Raw materials including main catalyst, co-catalyst, diluent and ethylene are added to the reactor to carry out polymerization reaction to obtain a slurry-like blend containing resin and diluent. (2) The slurry-like blend is washed with a purified diluent during the discharge process, and then the solid and liquid are separated. (3) After the solid-liquid separation, the resin is dried to obtain polyethylene resin product; (4) The obtained polyethylene resin product is used as polyethylene raw material, and after being compounded with processing aids including antioxidants and lubricants, it is fed into a screw extruder for melt extrusion. The fibers are sprayed out through the spinneret and directly oriented and stretched in the hot channel connected to the outlet of the spinneret to obtain fiber products.

Images