CN-122011462-A - Nascent UHMWPE entanglement degree regulating and controlling method

Abstract

The invention discloses a method for regulating and controlling entanglement degree of nascent UHMWPE, and relates to the field of polyethylene resin preparation. According to the invention, nascent ultra-high molecular weight polyethylene powder is placed in an annealing furnace, the time of raw materials in a temperature field is accurately regulated, and then the system is slowly quenched to room temperature, so that ultra-high molecular weight polyethylene is obtained. By precisely controlling the annealing temperature and time, the ultra-high molecular weight polyethylene is promoted to overcome the nucleation energy barrier of crystals, the enthalpy drives molecular chains in an amorphous region to participate in crystallization, meanwhile, the difficult-to-open braiding entanglement in the amorphous region is converted into easy-to-open non-braiding entanglement by overcoming the energy barrier, the entanglement molecular chain content in the amorphous region is reduced, the topological constraint structure formed by the mutual penetration of the molecular chains is reduced, the processing difficulty of the ultra-high molecular weight polyethylene in compression molding, solution spinning and extrusion molding is reduced, and the yield and the high-quality product rate of ultra-high molecular weight polyethylene products are improved.

Inventors

• LI WEI
• WANG LANG
• DI YUTAO
• SHI XUANYU
• WANG JINGDAI
• YANG YONGRONG

Assignees

• 浙江大学宁波国际科创中心

Dates

Publication Date

20260512

Application Date

20260204

Claims (9)

1. 1. A method for regulating and controlling entanglement degree of nascent ultra-high molecular weight polyethylene is characterized by comprising the following steps of placing nascent ultra-high molecular weight polyethylene powder in an inert gas protection or vacuum environment, setting the temperature to be within a range of 90-140 ℃, regulating and controlling the acting time of the nascent ultra-high molecular weight polyethylene powder in a temperature field, and then slowly quenching the system to room temperature by a programmed cooling path to obtain annealed ultra-high molecular weight polyethylene, so as to regulate and control entanglement degree, wherein the acting time of the powder in the temperature field is 2-60 hours.
2. 2. The method for controlling the entanglement degree of nascent ultra-high molecular weight polyethylene according to claim 1, wherein the viscosity average molecular weight of the nascent ultra-high molecular weight polyethylene powder is 1.0X10 6 -2.0×10 7 g/mol.
3. 3. The method for controlling the entanglement degree of nascent ultra high molecular weight polyethylene according to claim 1, wherein the vacuum degree of the vacuum environment is set in a range of 10 -3 Pa to 10 -1 Pa, and the temperature of the vacuum environment is set in a range of 120-140 ℃.
4. 4. The method for controlling the entanglement degree of nascent ultra-high molecular weight polyethylene according to claim 1, wherein the inert gas used in the inert gas protecting environment is one or a mixture of more of nitrogen, helium, neon, argon, krypton and xenon, and the pressure of the inert gas protecting environment is 0.5 to 2 atm.
5. 5. The method for controlling entanglement degree of nascent ultra high molecular weight polyethylene according to claim 1, wherein the time of the annealing treatment is in the range of 12 to 60 hours.
6. 6. The method for controlling the entanglement degree of nascent ultra high molecular weight polyethylene according to claim 1, wherein the cooling rate of the programmed cooling path is 5 to 30 ℃.
7. 7. An ultra-high molecular weight polyethylene obtainable by the process according to any one of claims 1 to 6.
8. 8. The ultra-high molecular weight polyethylene according to claim 7, wherein the entanglement degree of the ultra-high molecular weight polyethylene is characterized by a DSC warm-up and warm-down procedure, wherein the ultra-high molecular weight polyethylene is first warmed up from 30 ℃ to 5-10 ℃ below the melting point, then is kept warm for 30-60min, then is cooled down to 30 ℃, then is warmed up to 170-180 ℃ for the second time and is cooled down to 30 ℃, and the warm-up and warm-down rates are 10 ℃/min; The secondary temperature rise curve of the ultra-high molecular weight polyethylene obtained by DSC temperature rise and drop program is in bimodal distribution, and the peak area ratio A1 of the low temperature melting peak at 110-138 ℃ is 40-90%.
9. 9. The ultra-high molecular weight polyethylene according to claim 8, wherein the entanglement degree (1-A1/(a1+a2)) of the ultra-high molecular weight polyethylene after the annealing treatment is reduced by 10 to 60% as compared with the nascent ultra-high molecular weight polyethylene powder, wherein A2 is a peak area of a melting peak at 135 to 155 ℃ in a secondary temperature rising curve.

Description

Nascent UHMWPE entanglement degree regulating and controlling method Technical Field The invention belongs to the field of high polymer material performance regulation and control, and particularly relates to a method for regulating and controlling entanglement degree of nascent UHMWPE. Background Ultra High Molecular Weight Polyethylene (UHMWPE) is often referred to as linear polyethylene having a viscosity average molecular weight greater than 100X 10 4 g/mol. The extremely high molecular weight makes the composite material have excellent mechanical property, strong chemical inertness, biocompatibility, high wear resistance and self-lubricating property, so that the composite material is widely applied to the special fields of bulletproof armor, cutting-resistant gloves, electric wires and cables, lithium battery diaphragms and the like. At present, the nascent state UHMWPE has extremely large molecular chain length, a large number of chain entanglement is formed among molecular chains, so that the orientation, diffusion and relaxation behaviors of the molecular chains are limited, the melt viscosity of the UHMWPE is extremely large, the melt processing is extremely difficult, the mechanical property of the UHMWPE is only 1/3 of the theoretical value, and the expected performance is not achieved. In addition, because of the high melt viscosity of UHMWPE, the solution method processing of UHMWPE in industry needs to use a large amount of organic solvent such as white oil or decalin, and the UHMWPE is swelled and dissolved by using a small molecular solvent, so that the processing performance of the UHMWPE is improved. In the process of UHMWPE solution method processing, the mass fraction of UHMWPE is generally only about 10%, which makes the production efficiency lower. In order to reduce the degree of nascent entanglement of UHMWPE and thereby improve processability, conventional methods have been to regulate polymerization processes, such as modifying catalysts to produce low entanglement polyethylenes, and lowering polymerization temperatures, among others. To this end, the invention of CN103193908B discloses a process for preparing low entanglement UHMWPE and a catalyst related thereto, which prepares low entanglement ultra-high molecular weight polyethylene by loading a homogeneous catalyst on Polysilsesquioxane (POSS) particles having a size of 0.01-10nm, and then on a porous support, and increasing the distance of active centers by using steric hindrance of the POSS, suppressing the overlapping effect of molecular chains in the polymerization process. However, this technique involves catalyst design and preparation, and the procedure is more complicated. Patent CN104053684B issued a process for polymerizing low entanglement UHMWPE at 25-50 ℃ by preparing low entanglement UHMWPE at a milder temperature using an optimized ratio of FI catalyst/cocatalyst. However, the reduced temperature process employed in this process is not suitable for conventional Ziegler-Natta catalysts because it reduces ethylene polymerization activity, resulting in reduced molecular weight and yield. Disclosure of Invention Aiming at the current state of the art, the invention provides a method for regulating and controlling the entanglement degree of nascent UHMWPE, which reduces the entanglement degree of the nascent UHMWPE through a high-temperature vacuum annealing process, so that the nascent UHMWPE has more excellent processing performance, and can use higher processing concentration in solution processing, thereby improving the production efficiency, and having important significance for reducing the industrial production cost. The method can regulate the entanglement degree of UHMWPE in a larger range, and is applicable to UHMWPE with different molecular weights. In order to achieve the aim, the first aspect of the invention provides a method for regulating and controlling the entanglement degree of nascent ultra-high molecular weight polyethylene, which comprises the following steps of placing nascent ultra-high molecular weight polyethylene powder in an inert gas protection or vacuum environment, setting the temperature to be within a range of 90-140 ℃, regulating and controlling the acting time of the nascent ultra-high molecular weight polyethylene powder in a temperature field, and then slowly quenching the system to room temperature by a programmed cooling path to obtain annealed ultra-high molecular weight polyethylene, so as to regulate and control the entanglement degree, wherein the acting time of the powder in the temperature field is 2-60 hours. Further, the viscosity average molecular weight of the nascent ultra-high molecular weight polyethylene powder is 1.0X10 6 -2.0×107 g/mol. Alternatively, when a vacuum atmosphere is employed, the vacuum degree of the vacuum atmosphere is set in the range of 10 -3 Pa to 10 -1 Pa, and the temperature of the vacuum atmosphere is preferably set in the range of 120-140 ℃