JPH0418043B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing polyethylene fibers,
More specifically, by spinning a polyethylene solution,
The present invention relates to a method for producing high strength, high modulus, and thick fibers. Conventionally, a known method for producing high-strength, high-modulus polyethylene fibers is to spin a polyethylene solution with a large average molecular weight, cool it to produce gel-like fibers, and then heat and draw the fibers. However, the problem with this method is that the thicker the final fiber is, the lower its tensile strength and modulus tend to be.
It has been difficult to obtain highly modulus fibers. Therefore, it is extremely difficult to use this method to produce polyethylene fibers having a cross-sectional area of 0.01 mm ² or more, high strength, and high elastic modulus, which can be used as tensile strength wires, for example. The present invention makes it possible to produce thick, high-strength, and high-modulus polyethylene fibers by adding new improvements to such methods. The inventors of the present invention paid special attention to the fact that the thicker the gel-like fibers spun from a solution, the more difficult it is to draw them at a high magnification, and as a result, it is difficult to achieve high strength and high elastic modulus. We have arrived at the present invention which solves the above problems. That is, the present invention is a method for producing polyethylene fibers, which comprises aligning two or more gel-like fibers obtained by spinning a polyethylene solution, fusing them while heating, and then taking them off. The polyethylene solution of the present invention is preferably prepared by heating polyethylene having an average molecular weight (clay method) of 200,000 or more in a solvent. As a solvent, decalin or liquid paraffin can be used. Generally speaking, the higher the average molecular weight of polyethylene, the more suitable it is for obtaining high strength and high modulus.
If it is less than 10,000, it becomes difficult to obtain high strength and high modulus fibers. Spinning is performed by extruding a heated polyethylene solution through pores and solidifying it while containing the solvent by cooling. Two or more of the resulting gel-like fibers are drawn together, heated, and fused by applying the necessary force to bring them together into a single piece. Select the number of gel-like fibers to be drawn so that the thickness matches. The thicker the original gel fiber is, the more difficult it is to draw it at a high magnification, so in order to draw it at a high magnification as much as possible to obtain high strength and high modulus fibers, it is necessary to make the original gel fiber thinner. is preferable. However, the thinner the original gel-like fibers are, the greater the number of fibers that must be drawn in order to obtain drawn fibers of the required thickness, which requires more equipment and labor. Therefore, the practically preferable thickness of the gel-like fibers is determined by these balances. The fusion of the aligned gel-like fibers is carried out by heating and applying force to bring the aligned gel-like fibers together. Any method of applying force to bring the aligned gel fibers together may be used as long as it is convenient for fusing them, but in order to create fibers with a circular cross section and well fused, Particularly suitable is the method of drawing through a die with circular holes having a cross-sectional area smaller than the sum of the cross-sectional areas. Of course, it is also possible to pass through holes of any cross-sectional shape to produce fibers of any cross-sectional shape. It is also possible to actively stretch the fibers during take-off by utilizing the resistance when passing through the holes. The smaller the cross-sectional area of the pores is compared to the cross-sectional area of the gel-like fibers, the stronger the fusing force is, but it is limited to the extent that the pulling resistance increases and the fibers do not break. If the hole is provided with a conical introduction part, the purpose can be achieved more smoothly. FIG. 1 is a schematic diagram showing an example of a method for converging and integrating two or more gel-like fibers using a hole (die) having a conical introduction section. As a method of applying force to pull the gel-like fibers and bundle them together, there is also a method of running the gel-like fibers while pressing them between rollers. FIG. 2 is a schematic diagram showing an example of a method for converging and integrating two or more gel-like fibers while pressing them between rollers. If you heat it when fusing, it will be easier to fuse,
It is also advantageous for stretching. The heating temperature is preferably as high as possible within a range that does not reduce the strength and modulus of the drawn fibers. If necessary, the fused fibers can be further subjected to hot stretching to produce the desired polyethylene fiber. As the stretching method, methods such as stretching in a heated air tank or liquid heat medium, dielectric heating stretching, and drawing stretching using a heating die can be used. As a method for complete fusion, there is a method of combining two or more liquid fibers immediately after spinning but before solidifying, but there is no big difference between spinning one fiber corresponding to the combined thickness and the present invention. No such effect was observed. It is clear that it is difficult to obtain a high modulus with a fused yarn that is incompletely fused even if a large number of fibers are aligned. As mentioned above, although the conventional method of hot-drawing gel-like fibers obtained by spinning a polyethylene solution is suitable for producing high-strength, high-modulus fibers, it is difficult to obtain thick fibers. There is a problem that the strength and elastic modulus of the obtained fibers decrease as the fibers increase, making it impossible to achieve the intended purpose. The reason for this is that the spun gel fiber contains a large amount of solution, so its cross-sectional area becomes extremely large.The thicker the gel fiber is, the more the gel fiber is formed by spinning. It is presumed that this is because fiber unevenness in the cross-sectional direction of the fibers, that is, differences between inner and outer layers, and other unevenness tend to occur. The present invention makes it possible to obtain a drawn yarn of the required thickness by spinning relatively thin gel-like fibers and fusing a large number of them. The effect of this fusion is different from the conventionally known fused yarn, which fuses only the surfaces of fibers, and the effect of the fusion can be achieved by applying the force necessary to fuse the fibers and by the action of the solvent contained in the fibers. It is possible to form a shape and involves almost complete integration. According to the present invention, polyethylene fibers that are thick and have high strength and high modulus can be produced relatively easily. For example, the cross-sectional area of monofilament is 0.01 mm ² or more, the tensile strength is 180 Kg/mm ² or more, and the tensile modulus is 3500 Kg/mm 2 or more.
Polyethylene fibers larger than mm ² can be produced more easily than with conventional techniques. The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. Example 1 A solution consisting of 4% by weight of polyethylene with an average molecular weight (viscosity method) of 2×10 ⁶ and 96% by weight of decalin,
After extruding through the holes of a spinneret, the fibers were cooled and solidified to prepare gel-like fibers. At that time, the temperature of the solution was 130℃, and the cooling solidification was
It was carried out in water at 30℃. The pore diameter of the spinneret was 0.7 mm, and the gel-like fibers obtained had 180 filaments, and each filament had an average cross-sectional area of 0.71 mm ² in a state containing 94.5% by weight of decalin. This gel-like fiber was passed through a die having holes in the shape shown in FIG. 1 and drawn while being stretched to double its length. At that time, the die temperature was maintained at 100°C. Subsequently, the fiber was stretched 8.8 times through a heated air bath at 130°C, and then stretched 2 times through a heated air bath at 140°C to obtain a drawn fiber substantially free of decalin with a total stretching ratio of 35 times. . During the manufacturing process, all of the monofilaments constituting the original gel-like fibers of the drawn fiber were fused to have a completely single circular cross section, and the cross-sectional area was 0.205 mm ² . In addition, the tensile strength of the drawn fiber is 301Kg/ ^mm2 ,
The tensile modulus was 8400 Kg/mm ² and it also showed sufficient resistance to bending. Examples 2 to 4 Polyethylene with an average molecular weight (viscosity method) of 2×10 ⁶
A gel-like fiber was prepared by extruding a solution consisting of 3.5% by weight of decalin and 96.5% by weight of decalin through the holes of a spinneret, and cooling and solidifying the solution. At that time, the temperature of the solution was 130℃, and the cooling solidification was 30℃.
It was carried out in water at ℃. Subsequently, gel-like fibers consisting of a large number of filaments were fused together and further drawn in the same manner as in Example 1. The cross-sectional area of the hole in the die used for fusion corresponded to 70-90% of the cross-sectional area of the gel-like fibers. The number of filaments of the gel-like fibers, the cross-sectional area of each filament of the gel-like fibers, the total stretching ratio, the cross-sectional area of the drawn fibers, the tensile strength, and the tensile modulus of the drawn fibers were as shown in Table 1. Comparative Example Gel fibers were obtained by spinning in the same manner as in Examples 2 to 4, but in this case, the number of filaments of the gel fiber was 1.
The cross-sectional area was particularly large compared to other examples. This gel-like fiber was similarly drawn, but the drawing ratio that could be stably achieved was lower than in the other examples, and both the tensile strength and tensile modulus of the drawn fiber were low. Those values are shown in Table 1 as in Examples 2-4. 【table】

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of a method for converging and integrating two or more gel-like fibers using a hole having a conical introduction section. FIG. 2 is a schematic diagram showing an example of a method of converging and integrating two or more gel-like fibers while pressing them between rollers. A...Conical introduction part, B...Gel-like fiber, D...
...Take-off direction, d...Diameter of hole, R, R'...Roller.

Claims (1)

[Scope of Claims] 1. A method for producing polyethylene fibers, which comprises aligning two or more gel-like fibers obtained by spinning a polyethylene solution, fusing them while heating, and taking them off. 2. A method of fusing two or more fibers and pulling them together is
The method for producing polyethylene fibers according to claim 1, wherein the gel-like fibers are drawn by passing through holes having a cross-sectional area smaller than the total cross-sectional area of the gel-like fibers.