Method for preparing low-titer high-strength high-modulus polyethylene fibre

Abstract

The present invention discloses a process for producing low-titer, high-strength and high-modulus polyethylene fibers, comprising the following steps: dissolving the ultra-high molecular weight polyethylene into paraffin oil with a low viscosity to form a spinning solution with a concentration of 3ˆ¼15%; extruding the spinning solution through a thin spinneret with at least 10 orifices having a diameter ¦ of 0.7ˆ¼0.8mm and a length / diameter ratio of 10ˆ¼12, by applying a high pressure in the range of 2.5±1.0MPa to the spinning solution, such that the fluid in the orifices is extruded at a shear rate of 200ˆ¼3 500sec -1 ; and then performing a jet stretch at a deformation rate of 200ˆ¼5 000min -1 within an air-gap of 10ˆ¼15mm between the spinneret and the quench bath surface; feeding the jet-stretched fluid into the quench bath to form gel filaments; extracting and drying the gel filaments; and performing a multistage ultrahigh post stretch on the dried gel filaments with a stretch ratio of 15 or less. In this process, the solution is extruded at a high rate by using a spinneret with small orifice diameter, thereby achieving a high shear rate and a high deformation rate, so the present process is a novel and effective spinning process.

Description

technical field [0001] The invention relates to a preparation method of low denier, high-strength and high-modulus polyethylene fiber, which belongs to polymer compounds. Background technique [0002] Since the birth of high-strength and high-modulus polyethylene fibers in the 1980s, people have conducted in-depth discussions on gel spinning, and realized that the three keys to preparing high-strength and high-modulus polyethylene fibers by gel spinning are: (1) Ultra-high molecular weight polyethylene solution Untangle; (2) Jelly filament forming (maintenance of UHMW-PE macromolecule unentangled state); (3) Super thermal stretching, resulting in high crystallization and orientation of PE macrofraction chains, accompanied by transformation of PE crystal system . Among them, the molding of jelly filaments has attracted more attention and achieved practical results. [0003] WO01-73173A proposes to use a thick spinneret with an ultra-length-to-diameter ratio (=1mm, L / D≥40) ...

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Problems solved by technology

However, there are three major defects in this method: (1), the super length-to-diameter ratio of the spinneret aperture obviously increases the resistance of the fluid flow, and the extrusion speed of the spinneret hole is only 1ml / min, which makes the spinning efficiency low ; (2) The stretching control range of the nozzle is very narrow (≤6.4mm). In actual spinning, the liquid level fluctuation caused by the circulation of the liquid in the quenching bath not only affects the change of the stretching deformation rate, but even the cooling liquid will affect the (3), in the stretching area of ​​the nozzle, it is difficult to apply a blowing of 0.76m / min, especially when the number of spinneret holes increases, the blowing of this flow rate will lose its significance

However, this method also has three major deficiencies: first, the thickness of the orifice plate is greatly increased due to the introduction of long guide holes, resulting in an increase in the flow resistance of the solution. The specific performance is that the maximum output per hole is only 2.2ml / min. It is unfavorable to high-efficiency spinning; the second is that the stretching of the nozzle can show the effect at a higher ratio (in Example 1.2, the ratio of stretching is 40), but the stretching of the nozzle at a high ratio will endanger the stability of the stretching; the third is that if the nozzle is lowered The stretching ratio will increase the burden of thermal stretching of the jelly filament and the difficulty of equipment

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