JPH07238416A - Production of high-strength polyethylene fiber - Google Patents

Abstract

PURPOSE:To produce a high-strength polyethylene fiber useful as a composite reinforcing material, a rope, a fishing line, a bulletproof material, etc., by blending an ultrahigh-molecular-weight polyethylene with a volatile solvent, heating and dissolving the resultant mixture, spinning the obtained solution, removing the solvent and subsequently drawing it. CONSTITUTION:A slurry containing 5 to 50 pts.wt. ultrahigh-molecular-weight polyethylene and 95 to 5 pts.wt. volatile solvent (decahydronaphthalene, etc.) is heated and dissolved in pn extruder 2 and the resultant solution is discharged through a nozzle 3. Before the discharded yarn is drawn through drawing tanks 5 and 8, etc., >=40% of the solvent is positively removed by using heated gases (a), (b), etc. The drawing tanks 5 are heated up to about the melting point of the material to be drawn and the residual solvent is removed simultaneously with the drawing treatment. The draft ratio in the respective drawing tanks is 2 to 10 times, preferably 3 to 8 times. Thus, the objective high-strength polyethylene fiber having >=35g/d strength can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-strength polyethylene fibers suitable for applications requiring high strength such as composite reinforcing materials, ropes, fishing lines, bulletproof materials and the like.

[0002]

2. Description of the Related Art In the conventional method for producing high-strength polyethylene fibers, a so-called "gel spinning method", in which an ultrahigh molecular weight polymer is dissolved in a solvent and spun, is disclosed in, for example, Japanese Patent Publication No. 60-47922. Japanese Patent Fair 1-2488
No. 7, for example. However, in the prior art, it is necessary to remove the solvent as much as possible in spinning, and when the solvent is actively removed, for example, Japanese Patent Publication No.
As seen in the comparative example of Japanese Patent No. 24887, it has been considered unfavorable for stretching.

As a technique for actively extracting or washing a solvent before stretching, its disclosure is found in Japanese Patent Publication No. 58-5228. However, this prior art is almost always until it is once cooled after being spun. The solvent was not removed.
Since the solvent cannot be substantially removed by such cooling, energy loss becomes large, and an efficient manufacturing method has been demanded. If cooling and winding are performed without removing the solvent, it becomes difficult to completely remove the solvent after the stretching step.

Further, when the drawing is carried out at a high temperature without removing the solvent, fusion occurs, so that it is necessary to lower the temperature of the drawing tank, but at a low temperature it is necessary to obtain a polyethylene fiber having excellent strength. It becomes impossible to stretch at a high stretch ratio. Even if multi-stage stretching is performed, if the stretching ratio cannot be increased in the first stage, it is necessary to stretch at a considerably high stretching ratio in the second and subsequent stages to obtain high strength. There is a problem that the deformation rate becomes larger than the relaxation time and the film cannot be stretched.

[0005]

On the basis of the above-mentioned problems, the present invention provides a manufacturing technique for stably manufacturing polyethylene fibers having high strength.

[0006]

That is, according to the present invention, a mixture containing 5 to 50 parts by weight of an ultra high molecular weight polyethylene polymer and 95 to 50 parts by weight of a volatile solvent is heated and dissolved, and a melt is spun out. Then, the solvent is positively removed and then stretched to provide a method for producing a high-strength polyethylene fiber having a strength of 35 g / d or more.

When removing the solvent in the above production method,
There is provided a method for actively removing a solvent using a heated gas, or a method for producing a high-strength polyethylene fiber in which a solvent is removed by a gas flow adjusted to at least two stages of temperature or wind speed.

Also provided is a method for producing a high-strength polyethylene fiber, which comprises performing the stretching while removing the solvent in the stretching step of the above-mentioned production method.

The ultrahigh molecular weight polyethylene in the present invention is characterized in that its repeating unit is substantially ethylene, and a small amount of another monomer such as α-olefin, acrylic acid and its derivative, vinylsilane and its derivative. May be a copolymer of these, or may be a copolymer of these copolymers, or a blend of ethylene homopolymers and copolymers, and further homopolymers such as other α-olefins, and of course ethylene It may be a single homopolymer.

Such ultra-high molecular weight polyethylene is generally spun by the above-mentioned "gel spinning method". For example, extruding the melt through a spinning nozzle gives a drawing filament. The solvent is removed from the extruded melt by heating gas. The temperature of the heated gas is preferably 50 ° C to 130 ° C, more preferably 60 ° C to 120 ° C. If the temperature is lower than the above range, the removal of the solvent will be insufficient, and fusion will easily occur in the stretching step. Further, it becomes impossible to perform drawing at a high draw ratio in the drawing tank because it is necessary to lower the drawing tank temperature. Further, if the temperature is higher than the above range, the physical properties of the fiber deteriorate. The wind speed is 0.2 m / sec to 2.0 m / sec, more preferably 0.5 m / sec to 1.5 m / sec. When the wind speed is lower than the above range, it becomes difficult to remove the solvent, and when the wind speed is high, the unevenness of the fiber becomes large.

When the gas flow is used in two or more stages of temperature and wind speed, the temperature of the first stage gas flow is 10 ° C to 50 ° C.
C., more preferably 20.degree. C. to 40.degree. It is difficult for the equipment to lower the temperature from the above range, and the nozzle may be cooled. Further, if the gas flow temperature is higher than the above range, it becomes difficult to obtain fibers having excellent strength. The gas flow temperature after the first step is 60 ° C to 130
C., and more preferably 90.degree. C. to 120.degree. If the temperature is lower than the above range, the removal of the solvent is insufficient and the fusion is apt to occur in the stretching step. When the temperature is higher than the upper range, it causes deterioration of the polymer. Wind speed is 0.2
m / sec to 2.0 m / sec, more preferably 0.5 m / sec
It is preferable to use it at a rate of 1 to 1.5 m / sec. When the wind speed is lower than the above range, it becomes difficult to remove the solvent, and when the wind speed is high, the irregularities of the fibers become large.

The positive removal of the solvent referred to in the present production method means removal of 40% or more, preferably 50% or more. If the solvent content is higher than the above regulation, it will be easy to fuse in the stretching step, and if the temperature of the stretching bath is lowered to prevent fusion, the stretchability will decrease, and the stretching speed in the first stretching step cannot be increased. High strength fibers cannot be obtained.

The unstretched molded body thus obtained is stretched. In the present invention, the stretching operation is carried out in multiple stages of one stage or two or more stages. The draw ratio is 2 to 10 in each draw tank.
It is possible to carry out the stretching operation at a fold, particularly 3 to 8 times. When performing multi-stage drawing of two or more stages, the temperature is usually set higher than the temperature of the pre-drawing tank.

An example of the method for producing the high-strength polyethylene fiber of the present invention is shown in the process chart of FIG. In FIG. 1, reference numeral 3 denotes a nozzle, and the ultra-high molecular weight polyethylene melted by heating and the volatile solvent solution are spun out from 3 and the solvent is positively removed by 40% or more by heating gas before stretching. The filaments that have passed through the spinning cylinder are sent online to the drawing tank through the driving roller 4 (4). The stretching tank is heated to near the melting point of the stretched object, the residual solvent is removed at the same time as stretching,
It is wound up by the drive roller 6. If necessary, the wound polyethylene filament is further stretched in one or more stages in multiple stages.

FIG. 2 shows a process chart of another preferred example of the method for producing polyethylene fiber of the present invention. The arrangement of the spinning nozzle, driving roller, and stretching tank in FIG. 2 is the same as that in FIG. 1, but the feature of this example is that when the melt immediately after spinning passes through the spinning tube, two stages of temperature and wind speed are applied. The solvent is removed by the conditioned gas flow. According to this method, by setting the gas temperature of the first stage lower than that of the second stage, it solidifies in the state of containing a large amount of solvent, and then by positively setting the temperature of the gas flow of the second stage high. Since the solvent is removed, a better fiber structure is formed, and it becomes possible to draw at a high draw ratio in a drawing tank. The evaluation items used in the present invention were performed in the following procedure.

(Strength) The strength in this specification is "Tensilon" manufactured by Orientec Co., Ltd., and the strain-stress curve is measured at an ambient temperature of 2 with a sample length of 200 mm and a stretching speed of 100% / min.
The stress was measured at 0 ° C. and 65% relative humidity, and the stress at the breaking point of the curve was determined as the strength (g / d). In addition, each value used the average value of the measured value of 10 times.

(Intrinsic Viscosity) The specific viscosity of various dilute solutions was measured with an Ubbelohde-type capillary viscous tube at 135 ° C. decalin, and the line outside the origin of the straight line obtained by the least square approximation of the plot of the viscosity concentration was measured. The intrinsic viscosity was determined from the interpolated points. In the case of measurement, when the raw material polymer is powdery, the shape is kept as it is, and when the powder is lumpy or filamentous sample, the sample is divided or cut into a length of about 5 mm, and 1 wt% of the polymer is prevented from oxidation. Agent (trade name "Yoshinox BHT" made by Yoshitomi Pharmaceutical Co., Ltd.) was added, and 135
A measurement solution was prepared by dissolving with stirring at ℃ for 4 hours.

[0018]

EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to the examples. Example 1 A screw-type slurry liquid obtained by mixing 10 parts by weight of ultra-high molecular weight polyethylene having an intrinsic viscosity of 18.5 and 0.8 methyl branch per 1000 main chain carbon atoms with 90 parts by weight of decahydronaphthalene. Extruder (30m
mφ). Subsequently, the melt was melted to 0.
It was extruded at a temperature of 175 ° C. from a nozzle having 7 holes and 96 holes.
After that, the spun yarn was spun at a temperature of 90 ° C. in a spinning tube with a length of 1 m.
The solvent was removed by applying a heated gas having a wind speed of 1.0 m / sec, and the solvent was removed at 75 m / min by a driving roller. The solvent content of the yarn discharged from the spinning cylinder was 76 parts by weight, and 65% of the original solvent could be removed. The undrawn yarn thus obtained was drawn at a draw ratio of 3 times while removing the solvent in a single-stage drawing tank set at a temperature of 135 ° C. online. The residual solvent of the obtained drawn yarn was 1% or less. When the yarn drawn in the first step was further drawn in a two-step drawing tank adjusted to 145 ° C at a high drawing speed of 250 m / min, it could be drawn up to 5.5 times and had a strength of 4
A high strength polyethylene fiber of 5 g / d was obtained.

Example 2 Slurry preparation and extrusion conditions were as shown in Example 1, but spinning was carried out by dividing the gas flow temperature into two stages in solvent removal. That is, a gas stream having a temperature of 30 ° C. and a wind speed of 1 m / sec was sprayed onto the yarn immediately after spinning at a temperature of 30 ° C. and a wind speed of 1 m / sec.
A second gas stream was blown through a spinning tube 1 m long. The solvent content of the undrawn yarn after exiting the spinning cylinder was 75 parts, and 60% of the original content could be removed. This is Example 1
When stretched under the same conditions as above, it was possible to stretch up to 6.5 times, and high-strength polyethylene fiber having a strength of 50 g / d could be obtained.

Comparative Example 1 After the melt was extruded from a nozzle under the same conditions as in Example, a gas having a temperature of 25 ° C. and a wind speed of 1.0 m / sec was blown in a spinning cylinder. Immediately after leaving the spinning tube, the undrawn yarn contained 85 parts by weight of solvent. When this undrawn yarn was drawn under the conditions shown in Example 1, it was fused. In addition, the temperature of the drawing tank is 1
When the temperature was lowered to 00 ° C., it was impossible to stretch at a stretch ratio of 3 times. Therefore, the film was drawn in a single-stage drawing tank at a temperature of 100 ° C. and a draw ratio of 2 times. When this was subjected to two-stage drawing under the same drawing conditions as in the example, it was possible to draw up to a draw ratio of 6 times, but the total draw ratio (one-step draw ratio x two-step draw ratio) Only low strength is obtained, strength 33
Only g / d polyethylene fibers could be obtained.

[0021]

INDUSTRIAL APPLICABILITY In the dry spinning method in which the polymer solution is spun into gas from the spinneret of the present invention to form a yarn,
By positively removing the solvent in the spinning tube before performing the drawing in the drawing tank, it is possible to stably produce fibers having physical properties superior to those of the conventionally known techniques.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing apparatus according to a manufacturing method of the present invention.

FIG. 2 is a schematic view of a manufacturing apparatus according to the manufacturing method of the present invention.

[Explanation of symbols]

1: Slurry tank, 2: Extruder, 3: Nozzle, 4,
6, 7, 9: Drive roller 5: First stretching tank, 8: Second stretching tank, A: heated gas, a:
Heating gas 1, b: Heating gas 2

Claims (4)

[Claims] 1. A mixture containing 5 to 50 parts by weight of an ultra high molecular weight polyethylene polymer and 95 to 50 parts by weight of a volatile solvent is heated and dissolved, and the melt is spun out, and then the solvent is positively removed. A method for producing a high-strength polyethylene fiber, which is then stretched and has a strength of 35 g / d or more. 2. The method for producing a high-strength polyethylene fiber according to claim 1, wherein the solvent is positively removed by using heated gas. 3. The high-strength polyethylene fiber according to claim 2, wherein when the solvent is positively removed, the solvent is removed by a gas flow adjusted to at least two stages of temperature or wind speed. Production method. 4. The method for producing a high-strength polyethylene fiber according to claim 1, wherein the stretching is performed while removing the solvent.