Preparation process of energy-saving optimized ultra-high molecular weight polyethylene filament

Abstract

The application discloses a kind of preparation process of energy-saving optimization ultrahigh molecular weight polyethylene fiber, comprising the following steps, first, the mixed solution of white oil, ultrahigh molecular weight polyethylene powder, antioxidant, surfactant is configured, stirring is uniform, after being filtered by double screw shearing, filter, through spinneret, cooling, heating and stretching extrusion preparation gel silk;Gel silk is pre-shrunk for more than 48 hours, and after secondary cold stretching, tertiary hot stretching, extraction, drying and winding are carried out.The energy consumption of the present application is lower than that of the traditional process, the process temperature is more stable, the environmental impact is small, and the product consistency is good.

Description

Technical Field

[0001] This invention relates to a process for preparing ultra-high molecular weight polyethylene (UHMWPE), and more specifically, to a process for preparing energy-saving UHMWPE fiber filaments. Background Technology

[0002] Improving fiber mechanical properties and reducing production costs are the eternal themes of UHMWPE fiber production. The development trend of UHMWPE fiber technology mainly focuses on improving fiber technology, further improving fiber mechanical properties and reducing unevenness; and developing more economical and environmentally friendly production processes to further reduce production costs.

[0003] The 2018 book *Ultra-High Molecular Weight Polyethylene Fiber*, co-authored by Zhao Ying, Wang Dujin, and Yu Junrong, describes how phase separation occurs immediately after the UHMWPE spinning solution is extruded through the spinneret and rapidly cooled in the coagulation bath to form gel fibers. During the subsequent storage of the gel fibers, the solvent in the dilute phase gradually separates out, while the solvent in the concentrated phase remains largely within the filament. Because the glass transition temperature of polyethylene is far below zero degrees Celsius, the phase separation process in gel fibers is relatively slow.

[0004] The article "The Influence of Solution Spinning / Stretching Temperature on Ultra-High Strength Polyethylene Filaments" by Smith P and Lemstra PJ reveals that after the phase separation process, the gel fiber still contains a large amount of solvent, resulting in an extremely loose network structure. The intermolecular forces between polyethylene macromolecules in the network have been broken down by solvent molecules and become very weak. When subjected to tension, especially during high-temperature stretching, the plasticizing effect of the solvent easily leads to relative slippage between macromolecules, resulting in a decrease in tensile stress. This makes it difficult to achieve stable, high-ratio effective stretching and to reach high strength and high modulus. Therefore, a large amount of solvent must be removed before stretching.

[0005] Therefore, the ultra-high strength ultra-high molecular weight polyethylene fiber and its manufacturing method disclosed in Chinese invention patent application CN112111802A, currently employs a widely used process where wet spinning is followed by cold stretching, extraction, drying, hot stretching, and winding into the finished product. However, this process requires a large amount of volatile extractant, resulting in significant air pollution; the large amount of extractant and solvent mixture consumes a significant amount of energy in the distillation section, making it one of the major energy-consuming points of UHMWPE.

[0006] The amount of solvent in the gel fiber before it enters the extraction tank determines the amount of extractant used. The amount of extractant used determines the amount of extractant volatilization during the production process, the heat required for drying, and the energy consumption required for solvent-extractant separation. Therefore, it is necessary to remove as much solvent residue as possible from the gel fiber. Summary of the Invention

[0007] The purpose of this invention is to achieve phase separation of gel fibers as quickly as possible through a production process involving pre-thermal stretching followed by extraction, thereby reducing solvent residue and preventing slippage of oil-containing fibers during thermal stretching. This process also minimizes the solvent content of the fibers entering the extraction tank, thus reducing the amount of extractant used. Compared to traditional processes, this method has a smaller environmental impact, lower energy consumption, more stable process temperature, and better product consistency.

[0008] The technical solution of this invention is:

[0009] An energy-saving and optimized process for preparing ultra-high molecular weight polyethylene filaments includes the following steps:

[0010] S1: Mix white oil, ultra-high molecular weight polyethylene powder and additives in a certain proportion to form a mixture, and preheat it;

[0011] S2: The mixture prepared in step S1 is fed to a screw extruder, filtered, and extruded through a spinneret to obtain molten fibers;

[0012] S3: The molten fibers after being sprayed out are then rapidly cooled by cooling water; after exiting the water tank, the superheated air box makes the white oil liquid, and then passes through the three-roll drawing machine and the filament exiting roller to form a gel filament with the white oil initially removed;

[0013] S4: After the gel filaments prepared in S3 are pre-shrunken to reach equilibrium, they are subjected to two-stage cold stretching. During the stretching process, the extruded white oil and water are collected.

[0014] S5: The frozen gel filaments after S4 cold stretching are repeatedly stretched in three stages to the required fineness in an oil-containing environment at a temperature below 136°C.

[0015] S6: The filament prepared in S5 is extracted in an extraction tank. The extractant is tetrachloroethylene with a purity of 99.99%. The extraction is carried out at room temperature. The extracted filament is then dried in a drying oven to obtain oil-free and dry filament.

[0016] S7: Wind the filaments prepared in S6 into the finished product.

[0017] The energy-saving and optimized preparation process of ultra-high molecular weight polyethylene filament is further designed as follows: 100 parts of 76# white oil, 8 parts of ultra-high molecular weight polyethylene powder, 0.5 parts of antioxidant, and 0.05 parts of dispersant are taken in S1, stirred and mixed evenly, and preheated to 90°C.

[0018] The energy-saving and optimized preparation process of ultra-high molecular weight polyethylene filament is further designed in that the ultra-high molecular weight polyethylene has a molecular weight of 4 million.

[0019] The energy-saving and optimized preparation process of ultra-high molecular weight polyethylene filament is further designed as follows: In step S2, the mixture prepared in step S1 is sent to the twin-screw feed inlet, and the temperatures of each zone of the screw are set to 150℃, 170℃, 190℃, 210℃, 220℃, 230℃, 240℃, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, 285℃, and 285℃ respectively. The screw speed is adjusted to 150 r / min, and the filament is ejected from the spinneret after passing through the filter.

[0020] The energy-saving and optimized preparation process of ultra-high molecular weight polyethylene filament is further designed in that the pre-shrinkage time in S4 is not less than 48 hours to reach the equilibrium state.

[0021] The energy-saving and optimized preparation process of ultra-high molecular weight polyethylene filament is further designed in that the temperatures of the three-stage hot stretching chambers are 115±2℃, 125±2℃, and 125±2℃, respectively.

[0022] The energy-saving and optimized preparation process of ultra-high molecular weight polyethylene filament is further designed as follows: In S6, the extractant is tetrachloroethylene with a purity of 99.99%, the extraction is performed at room temperature for 3 minutes, and the extracted filament is dried in a drying oven at a temperature of 50°C, a wind speed of 0.5 m / s, and a time of 2 minutes to obtain oil-free and dry filament.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. The entanglement and a small amount of crystallization of the frozen gel fiber have been solidified and shaped by the rapid cooling. The ratio between the drawing roller and the water tank guide roller is adjusted to a certain extent. Heating and stretching the frozen gel fiber is conducive to the movement of solvent molecules. Installing an oil pressure roller on the drawing roller can accelerate the phase separation process of the frozen gel fiber, so that more solvent molecules are squeezed out in this process.

[0025] 2. After 48 hours of pre-shrinkage, the gel filaments reach equilibrium. They undergo two stages of cold stretching, followed by hot stretching in an oil-containing state. After hot stretching to the desired fineness, they are extracted and dried. Following 48 hours of free shrinkage, a large number of white oil molecules are released from the polyethylene network structure, increasing the intermolecular forces between polyethylene macromolecules. This is completely different from the state of nascent gel fibers. At this point, most of the white oil molecules exist between adjacent polyethylene macromolecular chains rather than between individual polyethylene molecules, thus reducing intermolecular slippage. The gel filaments can withstand more than 7 times the cold stretching ratio. During this process, more entanglements are broken, and adjacent molecular chains form an axial alignment.

[0026] A small number of white oil molecules between polyethylene macromolecular chains can increase lubrication, reduce the strong interaction between macromolecular chains, facilitate the unentanglement of adjacent molecular chains, and make it easier to achieve uniform distribution of amorphous regions and weak points during hot stretching, thereby improving the strength of the finished yarn.

[0027] 3. Traditional hot stretching requires controlling the temperatures of three heat chambers to achieve a final drawing speed of 45 m / min or higher: 136℃±2℃ for heat chamber one, 146℃±2℃ for heat chamber two, and 148℃±2℃ for heat chamber three. This invention involves stretching in an oil-containing state. Since the thermal conductivity of white oil is greater than that of air, this solution only requires controlling the temperatures of three heat chambers: 115℃±2℃ for heat chamber one, 125℃±2℃ for heat chamber two, and 125℃±2℃ for heat chamber three.

[0028] The temperature required for this process is 20°C lower than that of the previous process, and the conditions for deorientation cannot be met during hot stretching.

[0029] White oil has better thermal conductivity than air, allowing fibers to quickly and stably reach the set temperature in the heating chamber, resulting in orderly stretching. The fineness and strength of the fibers are more stable than those produced by previous processes, leading to better product consistency. The lower fineness of the monofilaments after hot stretching makes them easier to extract, reducing the amount of extractant used, thus reducing environmental pollution and lowering production costs. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the internal structure of the fiber before hot stretching, showing the partial removal of white oil molecules.

[0031] Figure 2 This is a schematic diagram of the internal structure of the fiber before extraction using existing technology. Implementation

[0032] The present invention will be further described below with reference to embodiments, but the scope of the present invention is not limited to these examples.

[0033] Example 1: A process for preparing energy-saving and optimized ultra-high molecular weight polyethylene filament, comprising the following steps:

[0034] S1: Take 100 parts of 76# white oil, 8 parts of ultra-high molecular weight polyethylene powder, 0.5 parts of antioxidant, and 0.05 parts of dispersant, stir and mix evenly, and preheat to 90℃. In this step, the ultra-high molecular weight polyethylene has a molecular weight of 4 million.

[0035] S2: The mixture prepared in step S1 is fed to the twin-screw feed inlet. The temperatures of each zone of the screw are set to 150℃, 170℃, 190℃, 210℃, 220℃, 230℃, 240℃, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, 285℃, and 285℃ respectively. The screw speed is adjusted to 150 r / min, and the mixture is ejected from the spinneret after passing through the filter.

[0036] S3: The molten fibers after being sprayed out are then rapidly cooled by cooling water. After exiting the water tank, they pass through a heated air box, a three-roll drawing machine, and an exiting roller to form a semi-finished gel fiber that has undergone preliminary solvent removal.

[0037] S4: After the gel filaments prepared in S3 are pre-shrunken for more than 48 hours to reach equilibrium, they are subjected to two-stage cold stretching. During the stretching process, the extruded white oil and water are collected.

[0038] S5: The frozen rubber filaments after cold stretching from S4 are passed through a stretching oven and a seven-roller stretching machine in an oil-containing state, and repeatedly stretched in three stages to the required fineness. The oven temperatures are set at 115℃, 125℃, and 125℃ respectively.

[0039] S6: The filaments prepared in S5 are extracted in an extraction tank. The extractant is tetrachloroethylene with a purity of 99.99%. The extraction is carried out at room temperature for 3 minutes. The extracted filaments are then dried in a drying oven at a temperature of 50°C, a wind speed of 0.5 m / s, and a time of 2 minutes to obtain oil-free and dry filaments.

[0040] S7: Wind the filaments prepared in S6 into the finished product.

[0041] The ultra-high molecular weight polyethylene filaments prepared using Example 1 achieved a strength of 36 cN / dtex, a modulus of 1500 cN / dtex, and a fineness deviation of no more than 5% per meter, with excellent hand feel. Long-term monitoring showed a 13.3% reduction in extractant volatilization, a 41% reduction in drying energy consumption, a 31.8% reduction in distillation energy consumption, and a 15.6% reduction in overall cost.

Claims

1. A process for preparing energy-saving and optimized ultra-high molecular weight polyethylene filaments, characterized in that: Includes the following steps: S1: Mix white oil, ultra-high molecular weight polyethylene powder and additives in a certain proportion to form a mixture, and preheat it; S2: The mixture prepared in step S1 is sent to a screw extruder, filtered, and then extruded through a spinneret to obtain molten fibers; S3: The extruded molten fibers are then rapidly cooled by cooling water; after exiting the water tank, they are passed through a superheated air box to make the white oil liquid, and then passed through a three-roll drawing machine and a fiber exiting roller to form a preliminarily de-whitened gel fiber; S4: The gel fiber prepared in S3 is pre-shrunken to reach an equilibrium state and then subjected to two-stage cold stretching. During the stretching process, some of the extruded white oil and water are collected; S5: The gel fiber after cold stretching in S4 is subjected to three-stage repeated stretching in an oil-containing state at a temperature below 136°C to the required fineness. The hot box temperatures for the three-stage hot stretching are 115±2°C, 125±2°C, and 125±2°C, respectively. S6: The filament prepared in S5 is extracted in an extraction tank. The extractant is tetrachloroethylene with a purity of 99.99%. The extraction is carried out at room temperature. The extracted filament is then dried in a drying oven to obtain oil-free and dry filament. S7: Wind the filaments prepared in S6 into the finished product.

2. The preparation process of energy-saving optimized ultra-high molecular weight polyethylene filament according to claim 1, characterized in that: Take 100 parts of 76# white oil, 8 parts of ultra-high molecular weight polyethylene powder, 0.5 parts of antioxidant, and 0.05 parts of dispersant from S1, stir and mix evenly, and preheat to 90℃.

3. The preparation process of energy-saving optimized ultra-high molecular weight polyethylene filament according to claim 2, characterized in that: The ultra-high molecular weight polyethylene has a molecular weight of 4 million.

4. The preparation process of energy-saving optimized ultra-high molecular weight polyethylene filament according to claim 1, characterized in that: In step S2, the mixture prepared in step S1 is fed to the twin-screw feed inlet. The temperatures of each zone of the screw are set to 150℃, 170℃, 190℃, 210℃, 220℃, 230℃, 240℃, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, 285℃, and 285℃ respectively. The screw speed is adjusted to 150 r / min, and the mixture is ejected from the spinneret after passing through the filter.

5. The preparation process of energy-saving optimized ultra-high molecular weight polyethylene filament according to claim 1, characterized in that: In S4, the pre-retraction time is no less than 48 hours to reach equilibrium.

6. The preparation process of energy-saving optimized ultra-high molecular weight polyethylene filament according to claim 1, characterized in that: In S6, the extractant is tetrachloroethylene with a purity of 99.99%, and the extraction is carried out at room temperature for 3 minutes. The extracted filaments are then dried in a drying oven at a temperature of 50°C, a wind speed of 0.5 m / s, and a time of 2 minutes to obtain oil-free and dry filaments.

Images