CN110820058B - Preparation method of civil high-performance polyethylene fiber - Google Patents
Preparation method of civil high-performance polyethylene fiber Download PDFInfo
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- CN110820058B CN110820058B CN201911070707.9A CN201911070707A CN110820058B CN 110820058 B CN110820058 B CN 110820058B CN 201911070707 A CN201911070707 A CN 201911070707A CN 110820058 B CN110820058 B CN 110820058B
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/08—Melt spinning methods
- D01D5/098—Melt spinning methods with simultaneous stretching
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F6/04—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyolefins
Abstract
The invention relates to a preparation method of civil high-performance polyethylene fiber, which comprises the steps of extruding polyethylene raw material which has the weight-average molecular weight of 15-40 ten thousand and is polymerized by a single-activity-center catalyst into polyethylene undrawn protofilament at high temperature through a screw extruder; directly carrying out high-power drafting on the extruded protofilament at normal temperature; the high-power drafted raw silk is subjected to multiple-power drawing again at high temperature through a heat channel; and (3) rolling the polyethylene fiber after high-temperature stretching to obtain the polyethylene fiber with the tensile strength of more than 20 cN/dtex. Compared with the prior art, the fiber product obtained by the invention has the advantages of simple process flow, environmental protection, energy conservation, high safety factor, low production cost and the like under the condition of meeting the requirements of the existing civil high-performance fiber field.
Description
Technical Field
The invention belongs to the technical field of high polymer materials, and particularly relates to a preparation method of high-strength high-modulus polyethylene fibers.
Background
With the rapid development of science and technology, the demand of engineering technology for special fibers is continuously increased, and the high-performance polyethylene fiber has the characteristics of light weight, high strength, long service cycle, wear resistance, high strength, moisture resistance, corrosion resistance and the like, and is widely used for drag ropes, negative force ropes, salvage ropes, anti-cutting gloves and the like. Meanwhile, the high-performance polyethylene fiber can be made into protective clothing materials, helmets, bulletproof materials and the like in military affairs. The composite material of the high-performance polyethylene fiber also has high strength and extremely strong anti-collision performance, and is suitable for wing tip structures, airship structures, buoy airplanes and the like of various airplanes in the aspects of aerospace. In sporting goods, helmets, skis, sailboard, fishing rods, rackets, and bicycles, gliders, ultra lightweight aircraft parts, etc. have been made. Due to the biocompatibility of the ultra-high molecular weight polyethylene fiber composite material, the composite material can also be used for denture bases, artificial limbs, medical gloves and the like in the aspect of medical use.
In recent years, the use of high-performance fibers is gradually increased in the civil field, and at present, the high-performance fibers are mainly applied to ultra-high molecular weight polyethylene fibers or aramid fibers in the civil field, and the two types of high-performance fibers are relatively complex in production process, relatively high in production cost and relatively high in pollution in the production process, so that the expansion of the high-performance fibers in the civil field is limited by the factors, and the high-performance fibers are not widely applied so far.
Narrow molecular weight distribution polyethylene obtained by polymerization with a single-site catalyst has attracted much attention in the industry. The narrow molecular weight distribution polyethylene contains only few low molecular weight parts, so that the performance of the narrow molecular weight distribution polyethylene is a new step compared with the performance of the polyethylene obtained by the polymerization of the traditional Ziegler Natta and chromium-based catalytic systems. In the field of high-strength fibers, compared with ultrahigh molecular weight polyethylene, the single-active-center polyethylene has better processability, so that the single-active-center polyethylene shows a unique surface.
Current methods for polyethylene spinning can be largely divided into three major categories:
the first type comprises that Chinese patent CN200980146604, Chinese patent CN201410264678, international application publication No. W02005/066401A1, U.S. Pat. No. US430577 and the like disclose that high molecular weight polyethylene is firstly swelled and dissolved by solvent and then extruded into polyethylene protofilament. And (3) carrying out solvent extraction, drying and other steps on the protofilaments to remove the solvent, and finally carrying out multi-stage stretching to obtain the high-strength high-modulus polyethylene fiber. The molecular weight of the raw materials used in the method is generally higher than 150 ten thousand, so that the obtained polyethylene fiber has higher strength, and the tensile strength of the obtained polyethylene fiber can reach more than 30cN/dtex according to the difference of the molecular weight. But the production process is complex, the cost is high, the problems of solvent volatilization and recovery and the like in the production process are difficult to solve, and the influence on the environment is large.
The second type mainly comprises Chinese patent CN201010533593, Chinese patent CN201410416669, Chinese patent CN101230501A, etc., low molecular weight polyethylene or polyethylene modified master batch is blended with ultra-high molecular weight polyethylene, then the blended master batch is melted and extruded to form fiber precursor, and the fiber precursor is subjected to multi-stage stretching to obtain polyethylene fiber. In order to ensure the fluidity of the ultra-high molecular weight polyethylene, the low molecular weight polyethylene and the modified master batches are added in large amounts, the weight ratio is generally 5-10% or even higher, and the modified master batches also cause the defect of mechanical property of finished products, so that the strength of the obtained fiber is not high, and is generally 15-25 cN/dtex. Meanwhile, the process flow is also complex, so that the cost is not greatly reduced.
The third category mainly comprises the melt extrusion spinning of polyethylene with the weight average molecular weight of less than 30 ten thousand, such as U.S. Pat. No. 4,4228118 and Chinese patent CN03807737, and the like, and the methods do not need to add flow modified master batches or low molecular weight polyethylene, wherein part of the methods have limited mechanical properties of the obtained fibers due to low molecular weight of the used raw materials, and the other part of the methods do not completely exert the structural characteristics among molecular chains of the high molecular weight polyethylene due to the traditional processing technology, so that the tensile strength of the obtained polyethylene fiber products is only about 15cN/dtex, and the mechanical properties are not ideal as high-performance fibers.
Disclosure of Invention
The invention aims to solve the problems that the existing civil high-performance polyethylene has complex production process, higher production cost and greater environmental pollution, and the strength of the product obtained by the existing polyethylene melt spinning method is generally low, and provides a preparation method of a civil high-performance polyethylene fiber.
The purpose of the invention can be realized by the following technical scheme:
a preparation method of civil high-performance polyethylene fiber comprises the following steps:
(1) extruding polyethylene raw materials which have the weight-average molecular weight of 15-40 ten thousand and are polymerized by a single-activity-center catalyst into polyethylene undrawn protofilaments at high temperature by a screw extruder;
(2) directly carrying out high-power drafting on the extruded protofilament at normal temperature;
(3) the high-power drafted raw silk is subjected to multiple-power drawing again at high temperature through a heat channel;
(4) and (3) rolling the polyethylene fiber after high-temperature stretching to obtain the polyethylene fiber with the tensile strength of more than 20 cN/dtex.
The single-site catalyst is selected from a metallocene catalyst or a late transition metal catalyst.
The ratio of the weight average molecular weight to the number average molecular weight of the polyethylene raw material Mw/Mn is less than 3.0, the number of thousand carbon methyl groups is less than 0.1, and the density of the polyethylene raw material>0.94g/cm3。
The polyethylene raw material does not need to be added with a processing aid in the stage of extruding the raw material into an undrawn protofilament. In the processing of fiber products, a small amount of the auxiliary becomes impurities in the ultrafine fibers, resulting in a decrease in the fiber properties. Compared with the traditional extrusion process of polyethylene, especially high molecular weight polyethylene, the extrusion temperature is often over 200 ℃, so that an antioxidant must be added to prevent the degradation of molecular chains in the processing process, and the performance of extruded fibers is reduced and yellowed. According to the invention, the unique rheological characteristic of the single-active polyethylene at 15-40 ten thousand hours is utilized to control the processing temperature of the polyethylene, and because the molecular weight distribution of a single-active center is narrow and the extremely-high molecular weight part is few, after the melt extrusion is carried out under the processing technology of the invention, the molecular chain degradation phenomenon hardly occurs, the addition of an antioxidant before processing is avoided, the influence of impurities on the fiber stretching process is reduced to the maximum extent, the blending equipment and the processing steps before the addition in the traditional technology are reduced, and the cost is reduced again.
The temperature of the extrusion section is 145-200 ℃, preferably 150-180 ℃, and the temperature of the melt pump to the machine head is 145-220 ℃, preferably 150-180 ℃.
The polyethylene is extruded without cooling, and is directly subjected to high-power stretching, wherein the stretching multiple is 5-30 times, and preferably 10-20 times.
The high-temperature multi-time stretching ratio of the heat shaft is 5-15 times, preferably 7-12 times.
The temperature of the heat shaft is controlled to be 100-130 ℃, and preferably 110-125 ℃.
The residence time of the fibers in the heat shaft is greater than 5 seconds, preferably greater than 10 seconds, more preferably greater than 20 seconds.
The diameter of a filament outlet hole of a head mouth mold of the screw extruder is 0.5-10 mm.
In order to further improve the performance of products on the premise of ensuring the simplification of a processing technology, polyethylene with the weight-average molecular weight section of 15-40 ten thousand is selected as a raw material, compared with the traditional preparation process of high-performance polyethylene fibers, ultrahigh molecular weight polyethylene with the weight-average molecular weight of more than 100 ten thousand is used as a base material to provide strength, and then the processing performance is improved by adding low molecular weight polyethylene or a processing aid.
The present invention also found particular processing characteristics for 15-40 million single-site polyethylenes are that, for this material, when using conventional processing temperatures, i.e. processing temperatures above 200 ℃, the strands extruded from the head are less stretchable and the fibers require a rapid cooling process before the subsequent steps can be carried out to prevent inter-fiber sticking phenomena. In view of this phenomenon, when the processing temperature can be controlled to a specific temperature below 200 ℃, single-site polyethylene having a weight average molecular weight of 15 to 40 ten thousand is used, the high-power drafting can be directly carried out after the extrusion by the extruder head, the drawing multiplying power can even reach 30 times of the extrusion speed, the high-power drawing machine has excellent ductility and certain melt strength, the phenomenon of filament breakage can not occur, after high-power drafting, the fineness of the polyethylene protofilament can reach below 0.5mm, the problem that the cooling is not timely after extrusion is effectively relieved by the ultrafine protofilament, the cooling effect for the interior of the fiber protofilament is far superior to that of the traditional air cooling or water cooling process, the probability of generating large grains is greatly reduced, the high-temperature high-power drawing difficulty in the later period is reduced, the mechanical property of the fiber product after subsequent high-temperature stretching is greatly improved, the step of cooling after extrusion is omitted, and the investment and processing cost in the traditional process are reduced again.
The invention further discovers that in order to obtain the polyethylene fiber with higher performance by a melt spinning method, when the extruded fiber is subjected to high-power drawing through a hot shaft, the residence time is longer than that of the traditional thermal drawing process of the ultra-high molecular weight polyethylene fiber, and the molecular chain of the obtained fiber can be fully oriented and crystallized under the longer residence time.
The invention relates to a preparation method of civil high-performance polyethylene fiber, which is characterized in that a polyethylene raw material obtained by polymerization of a single-active-site catalyst is directly subjected to high-temperature melt extrusion to prepare the high-performance polyethylene fiber without using a solvent or any processing aid.
At present, the preparation method of the high-strength high-modulus polyethylene fiber generally uses ultra-high molecular weight polyethylene, and improves the performance of the polyethylene fiber by improving the molecular weight of the polyethylene. However, as the molecular weight increases, the processability of the polyethylene decreases substantially. The processing performance can be improved by introducing a large amount of solvent in the processing process, and the introduction of the solvent brings a series of problems of influence of desolventizing on the performance of the product, great increase of preparation cost, environmental protection and the like. It is therefore desirable to find a spinning process that results in high performance fibers without the need for solvent addition.
As is known, the key of influencing the processability is the molecular chain part with high molecular weight in polyethylene, the invention carries out the preparation of fibers by using a high molecular weight polyethylene raw material obtained by polymerization of a single-active-site catalyst, and the single-active-site catalyst has the characteristic that the molecular weight distribution of the polyethylene obtained by polymerization is narrow, and the processability of the polyethylene raw material and the mechanical property of a product are considered. The characteristic is more obvious in single-active-center polyethylene with the weight-average molecular weight of 15-40 ten thousand, and compared with ultrahigh molecular weight polyethylene, the single-active-center polyethylene with the high molecular weight has processability, and the mechanical property is equivalent to that of the ultrahigh molecular weight polyethylene and is better than that of the traditional high molecular weight polyethylene (see table 1).
TABLE 1 comparison of mechanical Properties of Single-site polyethylene
The invention obtains the high-performance polyethylene fiber product by using the polyethylene raw material with reasonable molecular weight distribution and molecular weight range and a targeted processing technology without adding an auxiliary agent, and the performance index of the product is suitable for the current high-performance civil fiber. Compared with the existing preparation method of the high-performance civil fiber, the preparation method of the high-performance civil fiber disclosed by the patent has the following advantages in the technical scheme under the condition of meeting the performance requirement of the existing high-performance civil fiber:
1) and a solvent is not needed in the spinning process, and the mixing and cooling processes are avoided, so that the spinning process of the high-performance polyethylene fiber is greatly simplified.
2) Greatly reducing the production cost caused by treating the solvent and recycling the solvent.
3) The production process is in a solvent-free state, so that the safety factor in the production process is greatly improved.
4) No hazardous waste is generated in the production process, so that the production process of the high-strength high-modulus polyethylene fiber is more environment-friendly.
5) The production process has no swelling step, so that the production process is more stable.
6) During processing, no processing aid is required to be added, the influence of impurities on the fiber drawing process is reduced to the maximum extent, and the blending equipment and process steps before material adding in the traditional process are reduced
7) The temperature of the extrusion process is greatly reduced, and energy is greatly saved in the production process.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.
A preparation method of civil high-performance polyethylene fiber comprises the following steps:
(1) extruding polyethylene raw material with weight-average molecular weight of 15-40 ten thousand obtained by polymerization of single active site catalyst, such as metallocene catalyst or late transition metal catalyst, into polyethylene undrawn protofilament at high temperature by screw extruder, wherein the ratio of weight-average molecular weight to number-average molecular weight of polyethylene raw material Mw/Mn is less than 3.0, the number of methyl groups is less than 0.1, and the density is less than>0.94g/cm3In the extrusion process, no processing aid is required to be added, the temperature of an extrusion section is 145-200 ℃, the temperature of a melt pump to a machine head is 145-220 ℃, and the diameter of a wire outlet hole of a machine head mouth die of the screw extruder is 0.5-10 mm;
(2) extruded raw yarn is directly subjected to 5-30 times high-power drafting at normal temperature without being cooled;
(3) carrying out 5-15 times of multi-time stretching on the high-power drafted precursor at high temperature through a heat shaft at 100-130 ℃;
(4) and (3) rolling the polyethylene fiber after high-temperature stretching to obtain the polyethylene fiber with the tensile strength of more than 20 cN/dtex.
The following are more detailed embodiments, and the technical solutions and the technical effects obtained by the present invention will be further described by the following embodiments.
The characterization data of the polyethylene feedstock in the examples were obtained by the following method:
tensile Properties
The finished filaments were tested for tensile strength and tensile modulus using the method and apparatus of ASTM D885M.
Example 1
Taking the post-transition metal catalyst for polymerization to obtain a product with the weight average molecular weight of 15 ten thousand, the Mw/Mn of 2.8, the number of methyl groups of less than 0.1 and the density of 0.945g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging temperature is145-180 ℃, the rotating speed is 90 r/min, and the aperture of the extrusion neck ring mold is 0.5 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 10 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 7 times, and the temperature of the heat channel is 100 ℃.
The fiber after high-temperature multiple drawing is tested to obtain the high-performance fiber with the tensile strength of 21.19 cN/dtex.
Example 2
The weight average molecular weight obtained by polymerization of the metallocene catalyst is 20 ten thousand, the Mw/Mn is 2.9, the number of methyl groups is less than 0.1, and the density is 0.943g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging temperature is 145-190 ℃, the rotating speed is 90 r/min, and the aperture of the extrusion neck ring mold is 0.9 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 15 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 8 times, and the temperature of the heat channel is 110 ℃.
And testing the fiber subjected to high-temperature multiple drawing to obtain the high-performance fiber with the tensile strength of 23.32 cN/dtex.
Example 3
The weight average molecular weight obtained by polymerization of the metallocene catalyst is 40 ten thousand, the Mw/Mn is 2.9, the number of methyl groups is less than 0.1, and the density is 0.941g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging temperature is 145-190 ℃, the rotating speed is 110 r/min, and the aperture of the extrusion neck ring mold is 1 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 5 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 9 times, and the temperature of the heat channel is 120 ℃.
And testing the fiber subjected to high-temperature multiple drawing to obtain the high-performance fiber with the tensile strength of 25.92 cN/dtex.
Example 4
Taking metallocene catalystThe weight average molecular weight obtained by polymerization was 20 ten thousand, Mw/Mn was 2.7, the number of methyl groups per thousand was less than 0.1, and the density was 0.943g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging temperature is 145-190 ℃, the rotating speed is 200 r/min, and the aperture of the extrusion neck ring mold is 5 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 30 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 9 times, and the temperature of the heat channel is 125 ℃.
And testing the fiber subjected to high-temperature multiple drawing to obtain the high-performance fiber with the tensile strength of 24.39 cN/dtex.
Example 5
Taking the late transition metal catalyst for polymerization to obtain a product with the weight average molecular weight of 40 ten thousand, the Mw/Mn of 2.4, the number of methyl groups of less than 0.1 and the density of 0.941g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging temperature is 145-200 ℃, the rotating speed is 220 r/min, and the aperture of the extrusion neck ring mold is 10 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 27 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 15 times, and the temperature of the heat shaft is 130 ℃.
The fiber after high-temperature multiple drawing is tested to obtain the high-performance fiber with the tensile strength of 28.21 cN/dtex.
Example 6
Taking the late transition metal catalyst for polymerization to obtain a product with the weight average molecular weight of 30 ten thousand, the Mw/Mn of 2.0, the number of methyl groups of less than 0.1 and the density of 0.95g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging temperature is 145-200 ℃, the rotating speed is 220 r/min, the temperature of the melt pump to the head is 145-220 ℃, and the aperture of the extrusion neck ring is 5 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 25 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 10 times, the temperature of the heat tunnel is 100 ℃, and the retention time of the fiber in the heat tunnel is 10 s.
The fiber after high-temperature multiple drawing is tested to obtain the high-performance fiber with the tensile strength of 26.10 cN/dtex.
Example 7
Taking the post-transition metal catalyst for polymerization to obtain a polymer with the weight average molecular weight of 15 ten thousand, the Mw/Mn of 2.5, the number of methyl groups of thousand less than 0.1 and the density of 0.942g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging section is 150-180 ℃, the rotating speed is 200 r/min, the temperature of the melt pump to the machine head is 150-180 ℃, and the aperture of the extrusion neck ring mold is 0.5 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 5 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 5 times, the temperature of the heat tunnel is 110 ℃, and the retention time of the fiber in the heat tunnel is 15 s.
And testing the fiber subjected to high-temperature multiple drawing to obtain the high-performance fiber with the tensile strength of 25.33 cN/dtex.
Example 8
Taking the late transition metal catalyst for polymerization to obtain a product with the weight average molecular weight of 25 ten thousand, the Mw/Mn of 2.8, the number of methyl groups of less than 0.1 and the density of 0.945g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging section is 150-180 ℃, the rotating speed is 200 r/min, the temperature of the melt pump to the machine head is 150-180 ℃, and the aperture of the extrusion neck ring mold is 0.5 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 20 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 12 times, the temperature of the heat shaft is 125 ℃, and the retention time of the fiber in the heat shaft is 25 s.
And testing the fiber subjected to high-temperature multiple drawing to obtain the high-performance fiber with the tensile strength of 25.31 cN/dtex.
Example 9
Taking the weight average molecule obtained by the polymerization of the late transition metal catalystThe amount of the catalyst was 40 ten thousand, the Mw/Mn was 2.6, the number of methyl groups per thousand was less than 0.1, and the density was 0.945g/cm3Feeding the polyethylene into a screw extruder for melt extrusion. The temperature of the double screw from the feeding section to the discharging section is 150-170 ℃, the rotating speed is 200 r/min, the temperature of the melt pump to the machine head is 150-200 ℃, and the aperture of the extrusion neck ring is 10 mm.
And (3) directly carrying out multiple stretching and rolling on the extruded protofilament, wherein the stretching multiplying power is 30 times of the extrusion rate. And (3) performing high-temperature multiple stretching on the wound fiber again, wherein the stretching ratio is 15 times, the temperature of the heat shaft is 130 ℃, and the retention time of the fiber in the heat shaft is 22 s.
And testing the fiber subjected to high-temperature multiple drawing to obtain the high-performance fiber with the tensile strength of 24.22 cN/dtex.
Comparative example 1
The preparation method comprises the steps of selecting ultra-high molecular weight polyethylene powder resin with the molecular weight of 150-200 ten thousand as a raw material, adding 3-8% (weight ratio) of polyethylene modified master batch, performing melt extrusion spinning and super-drawing by a screw with the length-diameter ratio of 1: 40 to obtain high-strength and high-elongation polyethylene fiber, wherein the fiber strength is 15-25 CN/dtex, and the elongation at break is 5-8%.
The specific production process comprises the following implementation steps:
first step preparation of polyethylene modified master batch:
1. selecting LDPE low-density polyethylene or LLDPE linear low-density polyethylene as a raw material, adding (by weight ratio) 7-15% of POE polyolefin elastomer, 3-5% of PE foaming agent and 5-10% of ethylene propylene rubber EPDM or SEBS for uniform blending;
2. and (3) uniformly mixing the polymers, mixing and granulating by a double screw: the temperature of each section of the double-screw rod is between 150 and 220 ℃, the rotating speed of the double-screw rod is controlled to be 200 to 250 revolutions per minute, and the polyethylene modified master batch is prepared.
The compound polyethylene modified master batch has the excellent functions of low melting point, low viscosity, good lubricity and fluidity, easy dispersion and the like.
And the second step of melt spinning preparation of ultra-high molecular weight polyethylene:
1. selecting ultra-high molecular weight polyethylene resin with the molecular weight of 150-200 ten thousand, and adding 3-8% (weight ratio) of compounded polyethylene modified master batch to be uniformly mixed;
2. conveying the mixture into a screw to extrude, melt and spin: the length-diameter ratio of the screw is 1: 40, the temperature of each section of the screw is 150-250 ℃, the extrusion speed of the screw is 200-250 rpm, the holes of a spinneret plate are 100-150, the hole diameter is 0.5-0.8 mm, the temperature of a spinning melt is controlled at 200-220 ℃, and the drafting of a nozzle is 5-15 m/min; cooling the sprayed primary fiber in a water bath, wherein the temperature of the water bath is controlled to be 20-25 ℃; cooling the fibers in a water bath to wind the fibers into a cylinder;
3. and then carrying out two times of super-stretching, drying and shaping on the fiber wound into a cylinder, and finally preparing a finished product fiber: stretching the first super-stretching step by using a water bath, wherein the water bath temperature is 80-95 ℃, and the stretching multiple is 5-10 times; secondly, drawing by using superheated steam, wherein the steam temperature is 110-130 ℃, and the drawing multiple is 3-6 times; drying after super-stretching, and circularly drying by using hot air at the drying temperature of 120-130 ℃ and the tension of 1.1-1.2 times; then shaping is carried out, wherein the shaping temperature is 130-145 ℃, and the shaping linear speed is 20-40 meters per minute; finally, preparing ultra-high molecular weight polyethylene finished fibers; and (6) rolling. The fiber strength of the prepared ultra-high molecular weight polyethylene fiber is 15CN/dtex to 20 CN/dtex.
Comparative example 2
Polyethylene having a weight average molecular weight of 15 ten thousand and an Mw/Mn of 5.1 was extruded through a spinneret having a diameter of 0.8mm at 270 ℃ at a single-hole discharge rate of 0.5 g/min. The extruded fiber passes through a heat preservation interval of 15cm, is quenched and cooled at 20 ℃ and 0.5m/s, and is wound.
And cooling the extruded protofilament by air, and then, performing post-stretching at the first-stage stretching temperature of 25 ℃ by 2 times. The second stage stretching temperature is 100 ℃, and the stretching time is 7 times. After multi-stage drawing, the strength of the polyethylene fiber is 12.5cN/dtex, and the modulus is 503 cN/dtex.
Comparative example 3
Taking high-density polyethylene with weight-average molecular weight of 30 ten thousand and weight-average molecular weight to number-average molecular weight ratio of 4.5, adding antioxidant to carry out spinning, wherein the temperature of a screw extrusion section is 230 ℃, the temperature of an extruder head is 290 ℃, and high-power stretching cannot be directly carried out after extrusion. And cooling the high-temperature fiber by water cooling, rolling and performing high-power drawing again, wherein the drawing ratio is 6 times, and the obtained fiber has the tensile strength of 7 cN/dtex.
TABLE 2
| Weight average molecular weight of ten thousand | Mw/Mn | Strength cN/dtex | Content of auxiliary agent% | |
| Example 1 | 15 | 2.8 | 21.19 | 0 |
| Example 2 | 20 | 2.9 | 23.32 | 0 |
| Example 3 | 40 | 2.9 | 25.92 | 0 |
| Example 4 | 20 | 2.7 | 24.39 | 0 |
| Example 5 | 40 | 2.4 | 28.21 | 0 |
| Example 6 | 30 | 2.0 | 26.10 | 0 |
| Example 7 | 15 | 2.5 | 25.33 | 0 |
| Example 8 | 25 | 2.8 | 25.31 | 0 |
| Example 9 | 40 | 2.6 | 24.22 | 0 |
| Comparative example 1 | 150～200 | - | 15～20 | 3～8 |
| Comparative example 2 | 15 | 5.1 | 12.5 | 0 |
| Comparative example 3 | 82 | 4.5 | - | 0 |
As can be seen from the above table, the method uses a weight average molecular weight of 15 to 40 ten thousand and a density of more than 0.94g/cm3After polyethylene obtained by polymerization of a single-active-site catalyst is used as a raw material and is subjected to melt extrusion, the prepared polyethylene fiber is superior to low-molecular-weight polyethylene used in a comparative example in mechanical property and a melt spinning product of ultra-high-molecular-weight polyethylene fiber obtained by blending the polyethylene fiber with modified master batches by a targeted processing process, and the cost, the process complexity and the environmental protection are far superior to those of a method for preparing high-performance fiber by using a solution dissolving and current melt extrusion method.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The embodiments described above are intended to facilitate the understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (15)
1. A preparation method of civil high-performance polyethylene fiber is characterized by comprising the following steps:
(1) extruding polyethylene raw material which has the weight-average molecular weight of 15-40 ten thousand and is obtained by polymerization of a single-active-center catalyst into polyethylene undrawn protofilament at high temperature by a screw extruder, wherein the temperature of an extrusion section is 145-200 ℃;
(2) cooling is not needed after the polyethylene is extruded, and high-power drafting is directly carried out on extruded precursor at normal temperature, wherein the stretching multiple is 5-30 times;
(3) the high-power drafted raw silk is subjected to multiple-power drawing again at high temperature through a heat channel;
(4) and (3) rolling the polyethylene fiber after high-temperature stretching to obtain the polyethylene fiber with the tensile strength of more than 20 cN/dtex.
2. The method for preparing a civil high-performance polyethylene fiber according to claim 1, wherein the single-site catalyst is selected from a metallocene catalyst or a late transition metal catalyst.
3. The process for preparing high-performance polyethylene fiber for civil use according to claim 1, wherein the ratio of weight average molecular weight to number average molecular weight of the polyethylene raw material, Mw/Mn, is less than 3.0, the number of methyl groups per thousand carbon is less than 0.1, and the density is less than 0.1>0.94g/cm3。
4. The method for preparing civil high-performance polyethylene fiber according to claim 1, wherein the polyethylene raw material is extruded into undrawn precursor without adding processing aid.
5. The method of claim 1, wherein the melt pump to head temperature is 145 ℃ to 220 ℃.
6. The method of claim 5, wherein the melt pump to head temperature is 150 ℃ to 180 ℃.
7. The preparation method of the civil high-performance polyethylene fiber according to claim 1, wherein the polyethylene is directly subjected to high-power drawing without cooling after extrusion, and the drawing ratio is 10-20 times.
8. The method for preparing civil high-performance polyethylene fiber according to claim 1, wherein the high-temperature multi-drawing ratio of the heat shaft is 5-15 times.
9. The method for preparing civil high-performance polyethylene fiber according to claim 8, wherein the high-temperature multi-drawing ratio of the heat shaft is 7-12.
10. The method for preparing the civil high-performance polyethylene fiber according to claim 1, wherein the temperature of the heat shaft is controlled to be 100-130 ℃.
11. The method for preparing a civil high-performance polyethylene fiber according to claim 10, wherein the temperature of the heat shaft is controlled to be 110-125 ℃.
12. The process for preparing a high performance polyethylene fiber for civil use according to claim 1, wherein the residence time of the fiber in the heat shaft is more than 5 seconds.
13. The method for preparing a civil high-performance polyethylene fiber according to claim 12, wherein the residence time of the fiber in the heat shaft is more than 10 seconds.
14. The method for preparing a civil high-performance polyethylene fiber according to claim 12, wherein the residence time of the fiber in the heat shaft is more than 20 seconds.
15. The preparation method of the civil high-performance polyethylene fiber according to claim 1, wherein the diameter of the filament outlet of the head die of the screw extruder is 0.5-10 mm.
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