WO2009119940A1

WO2009119940A1 - Manufacturing method of high tenacity polyethylene fiber and high tenacity polyethylene fiber prepared thereby

Info

Publication number: WO2009119940A1
Application number: PCT/KR2008/002823
Authority: WO
Inventors: Yong Gun Kim
Original assignee: Yong Gun Kim
Priority date: 2008-03-24
Filing date: 2008-05-21
Publication date: 2009-10-01
Also published as: KR20090101766A; EP2286008A1; KR100959867B1; EP2286008A4

Abstract

Disclosed are a method of manufacturing high-tenacity polyethylene fiber and high-tenacity polyethylene fiber manufactured thereby. The method includes mixing polyethylene, having a molecular weight average molecular weight ranging from 200,000 to 5,000,000, with a first solvent, which is a nonvolatile organic compound, thus obtaining a gel solution having an intrinsic viscosity of 17-23 dl/g; spinning the gel solution using a die, thus forming gel fiber; immersing the gel fiber in a second solvent, which is a liquid-phase volatile organic compound, at a high temperature close to the volatile point of the second solvent, and cooling it; and jetting the second solvent, which is a gas-phase volatile organic compound, to the cooled gel fiber, thus extracting the first solvent and drawing the gel fiber at a draw ratio of 30: 1-50: 1. Through this method, high-tenacity polyethylene fiber having superior mechanical properties, including high tenacity and high elongation and excellent chemical resistance, can be manufactured.

Description

MANUFACTURING METHOD OF HIGH TENACITY POLYETHYLENE FIBER AND HIGH TENACITY POLYETHYLENE FIBER PREPARED THEREBY

Technical Field

[1] The present invention relates to a method of manufacturing high-tenacity polyethylene fiber and high-tenacity polyethylene fiber manufactured thereby, and more particularly, to a method of manufacturing high-tenacity polyethylene fiber, which is capable of realizing high-tenacity polyethylene fiber having superior mechanical properties, including high tenacity and high elongation and excellent chemical resistance, and to high-tenacity polyethylene fiber manufactured thereby. Background Art

[2] Conventionally, high-tenacity polyethylene fiber has been widely used in various fields, thanks to its superior mechanical properties, including high tenacity and high elongation, and superior chemical properties, including high chemical resistance.

[3] The preparation of such high-tenacity polyethylene fiber includes an ultra-high drawing method, a solid state extrusion method, a zone drawing method, or a gel spinning method. Among these, particularly useful is a gel spinning method, which makes mass production possible.

[4] Specifically, the gel spinning method is conducted in a manner of mixing ultra- high-molecular- weight polyethylene with a first solvent which is nonvolatile, thus obtaining a gel solution, spinning the gel solution in a cooling bath, thus forming gel fiber, removing the first solvent, which is nonvolatile, from the gel fiber using a second solvent, which is volatile, and drawing the gel fiber.

[5] In this procedure, because ultra-high-molecular-weight polyethylene molecules are aligned lengthwise in the linear form of thin fiber, when an attempt is made to break the fiber, many linkages of the molecules must be cut. Ultimately, the fiber is imparted with high tenacity.

[6] However, the conventional volatile solvent is problematic in that it cannot completely extract the nonvolatile solvent for dissolving the high-tenacity polyethylene fiber and cannot be reused either, because it is difficult to separate from the nonvolatile solvent.

[7] Further, the fiber manufactured through the above method has creep properties and stress internally generated in the course of solidification and drawing, and thus may crack, and as well, does not have sufficient tenacity in the state in which the first solvent is not completely removed therefrom. Disclosure of Invention

Technical Problem

[8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the related art, and provides a method of manufacturing high- tenacity polyethylene fiber having superior mechanical properties including high tenacity and high elongation and excellent chemical resistance using ultra- high-molecular- weight polyethylene having a molecular weight ranging from hundreds of thousands to millions of mol.

[9] In addition, the present invention provides a method of manufacturing high-tenacity polyethylene fiber, which is capable of completely removing a first solvent, which is nonvolatile, and eliminating creep properties and stress from the fiber.

[10] In addition, the present invention provides high-tenacity polyethylene fiber, manufactured through the above method.

[11] The technical problems of the present invention are not limited thereto, and the other technical problems will become more apparent as the description proceeds. Technical Solution

[12] According to the present invention, a method of manufacturing high-tenacity polyethylene fiber may comprise mixing polyethylene, having a molecular weight average molecular weight ranging from 200,000 to 5,000,000, with a first solvent, which is a nonvolatile organic compound, thus obtaining a gel solution having an intrinsic viscosity of 17-23 dl/g; spinning the gel solution using a die, thus forming gel fiber; immersing the gel fiber in a second solvent, which is a liquid-phase volatile organic compound, at a high temperature close to the volatile point of the second solvent, and cooling it; and jetting the second solvent, which is a gas-phase volatile organic compound, to the cooled gel fiber, thus extracting the first solvent and drawing the gel fiber at a draw ratio of 30: 1-50: 1.

[13] In addition, according to the present invention, high-tenacity polyethylene fiber may be manufactured through the above method.

[14] Other embodiments of the present invention are set forth in the detailed description below.

Advantageous Effects

[15] According to the present invention, the method of manufacturing high-tenacity polyethylene fiber enables the manufacture of high-tenacity polyethylene fiber having superior mechanical properties, including high tenacity and high elongation and excellent chemical resistance. Such high-tenacity polyethylene fiber can be widely used in various fields such as bulletproof clothes, safety gloves, medical purposes, various ropes, helmets, and skis. [16] In the method according to the present invention, a first solvent can be completely removed from gel fiber, and simultaneously, creep properties and stress can be eliminated. Mode for the Invention

[17] Hereinafter, a better understanding of the present invention may be obtained through the following embodiments which are set forth to illustrate, but are not to be construed as the limit of the present invention, without departing from the scope of the accompanying claims.

[18] In the description, the term 'ultra high molecular weight¹ indicates a weight average molecular weight of 200,000 or more, and the term 'high tenacity¹ indicates a tenacity of 30 g/d or more, unless otherwise specified.

[19] Further, in the description, the term 'total draw ratio' indicates a value obtained by dividing the maximum speed of any roller, selected from among rollers from an early godet roller to a later winding roller, by the speed of the early godet roller.

[20] According to an embodiment of the present invention, the method of paring high- tenacity polyethylene fiber includes mixing polyethylene, having a molecular weight average molecular weight ranging from 200,000 to 5,000,000, with a first solvent which is a nonvolatile organic compound, thus obtaining a gel solution having an intrinsic viscosity of 17~23 dl/g (Sl), spinning the gel solution using a die, thus forming gel fiber (S2), immersing the gel fiber in a second solvent, which is a liquid- phase volatile organic compound at a high temperature close to a volatile point thereof, and cooling it (S3), and jetting the second solvent, which is a gas -phase volatile organic compound, to the cooled gel fiber, thus extracting the first solvent and drawing the gel fiber at a draw ratio of 30: 1-50: 1.

[21] Below, the method of paring high-tenacity polyethylene fiber according to the present invention is stepwisely described in more detail.

[22] CS 11 Formation of Gel Solution

[23] First, ultra-high-molecular- weight polyethylene is dissolved using the first solvent, which is a nonvolatile organic compound, thus preparing the gel solution (Sl).

[24] The ultra-high-molecular- weight polyethylene is a polyethylene homopolymer composed exclusively of ethylene as a repeating unit, or a polyethylene copolymer resulting from copolymerization of ethylene, substantially constituting a repeating unit with 5 mol% or less of a monomer copolymerizable with the above ethylene, such as alkene.

[25] The ultra-high-molecular- weight polyethylene has a weight average molecular weight of 200,000 or more, and preferably from 200,000 to 5,000,000. If the weight average molecular weight thereof falls below the above range, the number of terminal groups of polymer chains is increased, and such groups act as defects of finished polyethylene fiber, thus making it difficult to realize high tenacity. Hence, the use of polyethylene having a weight average molecular weight within the above range is preferable.

[26] The polyethylene has a ratio (Mw/Mn) of weight average molecular weight to number average molecular weight of 10 or less, and preferably 5-8. When the molecular weight distribution is narrow, as above, polyethylene fiber having superior tenacity can be manufactured.

[27] The first solvent includes a nonvolatile organic compound, in particular, a hydrocarbon-based organic compound having a boiling point of 35O⁰C or higher, and preferably from 35O⁰C to 500⁰C under atmospheric pressure. The first solvent having such properties is responsible for dissolving the ultra-high-molecular- weight polyethylene, and can be easily extracted by the second solvent in the subsequent extraction process. Moreover, the first solvent can be reused, with ease of handling due to no danger of fire.

[28] Specific examples of the first solvent include aromatic hydrocarbons, such as xylene, toluene, or fluorene; aromatic chlorinated hydrocarbons, such as trichlorobenzene; decalin; tetralin; paraffin; petroleum mineral oil; and mineral oil.

[29] In the preparation of the gel solution, the ultra-high-molecular-weight polyethylene is used in an amount of 5~20 parts by weight based on 100 parts by weight of the first solvent. If the amount of ultra-high-molecular- weight polyethylene is less than the above lower limit, the properties of finished polyethylene fiber, including tenacity and elongation, may be deteriorated. Conversely, if the amount of ultra- high-molecular- weight polyethylene is greater than the above upper limit, the solubility may be decreased. Thus, the ultra-high-molecular- weight polyethylene is preferably used within the above range in terms of the properties of finished high- tenacity polyethylene fiber and the solubility of ultra-high-molecular- weight polyethylene.

[30] Further, the ultra-high-molecular- weight polyethylene is preferably dissolved at

135~150°C. When the dissolution process is performed within the above temperature range, the solubility of the ultra-high-molecular-weight polyethylene in the first solvent is very high.

[31] The gel solution of ultra-high-molecular- weight polyethylene thus prepared has an intrinsic viscosity of 17-23 dl/g. When the intrinsic viscosity of the gel solution is within the above range, it has high crystallinity, and is thus efficiently drawn. Also, high tenacity and elongation may be ensured.

[32] CS21 Formation of Gel Fiber

[33] Next, the gel solution thus prepared is spun using the die, thus obtaining the gel fiber (S2).

[34] The formation of the gel fiber may be conducted by spinning the gel solution through a plurality of spinning nozzles formed in the die using an extruder.

[35] In the spinning process, the spinning temperature is set to 12O⁰C or higher, and preferably to 120~210°C. Further, the spinning pressure is set to 5 kPa or less, and preferably to 1.5 kPa or less. More specifically, the temperature of the extruder is maintained at 160- 18O⁰C, and the temperature of the die is maintained at 190-210⁰C.

[36] The die has a ratio (L/D) of length to diameter ranging from 25: 1 to 60: 1. When the

L/D ratio is within the above range, the gel solution passing through the spinning nozzles of the die may be maintained at an optimal intrinsic viscosity, thus resulting in polyethylene fiber having high tenacity and elongation.

[37] (S3) Immersion and Cooling of Gel Fiber

[38] The gel fiber exiting from the spinning nozzles of the die is immersed in the second solvent, which is a liquid-phase volatile organic compound, and is then cooled (S3).

[39] The gel fiber exiting from the spinning nozzles is passed through the air gap defined between the die head and the surface of the second solvent before being immersed in the second solvent. The air gap is preferably 2-10 mm long. Further, air, preferably an inert gas such as N , is blown into the air gap at a rate of 1 m/min, in order to prevent oxidation.

[40] The second solvent includes a volatile organic compound which does not change the gel structure of polyethylene and is harmless to the human body, and preferably a liquid-phase volatile organic compound having a boiling point of 60~80°C under atmospheric pressure. When the boiling point of the second solvent is within the above range, it may remain on the surface of the gel fiber for a desired period of time without concern about early evaporation, and may then be easily removed without concern about residue thereon.

[41] Specific examples of the second solvent include alcohols such as ethanol, ethers such as diethylether, ketones, such as acetone, cyclohexanone, and 2-methylpentanone, alkanes such as ethane and n-hexane, haloalkanes, such as dichloromethane and trichlorotrifluoroethane, and mixtures thereof.

[42] In the cooling of the gel fiber, the second solvent has a high temperature close to the volatile point thereof, and preferably the temperature thereof is set at ± 1O⁰C of the volatile point of the second solvent.

[43] The gel fiber is immersed in the second solvent at a high temperature and is then cooled, such that the gel fiber is slowly cooled in the range from the core portion to the outer portion, consequently preventing the generation of stress and creep properties.

[44] (84^s) Jetting and Drawing

[45] Next, the second solvent, which is a gas-phase volatile organic compound, is jetted to the cooled gel fiber, thus extracting the first solvent and drawing the gel fiber (S4).

[46] The extraction of the first solvent using the second solvent is conducted by jetting the second solvent when passing the cooled gel fiber through a roller, in order to draw the fiber.

[47] In this way, the extraction of the first solvent and the drawing of the fiber are simultaneously conducted through jetting, thereby eliminating internal stress and creep properties, consequently increasing fiber uniformity. Further, yarn breakage may be prevented in the drawing process, thus improving workability. Also, the orientation of fiber, which is directly related to tenacity thereof, may be improved through jetting.

[48] The drawing process is preferably conducted at a total draw ratio of 30: 1-50: 1. The drawing process may be performed through a single step, but is preferably carried out through two or more steps to prevent the generation of yarn breakage in the drawing process and to realize uniform drawing. More preferably, the drawing process is conducted in three or more steps.

[49] For example, in the case where the drawing process is performed in three steps, it includes primarily drawing the fiber while jetting the second solvent at a high temperature (volatile point of second solvent + 50~80°C) greatly exceeding the volatile point thereof, secondarily drawing the primarily drawn fiber while jetting the second solvent at an intermediate temperature (volatile point of second solvent + 20~50°C) slightly exceeding the volatile point thereof, and tertiarily drawing the secondarily drawn fiber at a low temperature (volatile point of second solvent + 5~20°C).

[50] The primary drawing process is conducted by jetting the second solvent at a high temperature greatly exceeding the volatile point of the second solvent when passing the fiber through a first roller. Specifically, the temperature of the second solvent is set to 120- 15O⁰C. When the temperature of the second solvent is within the above range, the rapid cooling of the surface of the fiber attributable to the volatilization of the first solvent remaining in the drawn fiber is prevented.

[51] The jetting speed of the second solvent is preferably 10-20 times as fast as the drawing speed. In the case where the jetting speed falls outside of the above range and is much faster than the drawing speed, fiber may be damaged. Conversely, when the jetting speed is too slow, annealing effects are exhibited only for a short distance.

[52] The temperature of the roller is very high, and is preferably set to 120~150°C. As such, it is preferred that the draw ratio be 70% or more of the total draw ratio.

[53] Subsequently, the primarily drawn gel fiber is secondarily drawn.

[54] The secondary drawing is conducted by jetting the second solvent at an intermediate temperature slightly exceeding the volatile point of the second solvent when passing the fiber through a second roller. The jetting speed of the second solvent is preferably 20-40 times as fast as the spinning speed. [55] In this case, the roller has an intermediate temperature, which is set to 100~130°C.

The draw ratio is 20% or less of the total draw ratio.

[56] Subsequently, the secondarily drawn gel fiber is passed through a third roller (at a low temperature) without jetting, thereby realizing tertiary drawing.

[57] In the tertiary drawing, the temperature of the roller is low, and is specifically set to

80- 120⁰C.

[58] Further, the second solvent, at a high temperature greatly exceeding the volatile point thereof, is jetted to the fiber at a speed 5-10 times as fast as the drawing speed, thus facilitating the connection of ethylene molecules broken due to annealing.

[59] The high-tenacity polyethylene fiber thus manufactured has superior mechanical properties, including high tenacity and elongation, and excellent chemical resistance. Specifically, tenacity of 30 g/d or more and high elongation of 3% or more are realized.

[60] In addition, according to another embodiment of the present invention, high-tenacity polyethylene fiber is provided. The high-tenacity polyethylene fiber has high mechanical properties and chemical resistance, and thus can be used in various fields such as cables, canvases, bulletproof clothes, safety gloves, medical purposes, various ropes, helmets, skis, sports and automobile products, and construction materials.

[61] A better understanding of the present invention may be obtained through the following examples which are set forth to illustrate, but are not to be construed as the limit of the present invention.

[62] <Example 1>

[63] 95 wt% of ultra-high-molecular- weight polyethylene (Mw: 2,000,000, Mw/Mn = 5) and 5 wt% of hydrocarbon-based paraffin oil having a boiling point of 35O⁰C as a first solvent were mixed to thus prepare a slurry solution, which was then placed in a stirrer at 14O⁰C, thus obtaining a gel solution having an intrinsic viscosity of 20 dl/g.

[64] The gel solution thus obtained was spun through spinning nozzles of a die having a ratio of L/D of 25:1 using an extruder at 170 + 1O⁰C, immersed in trichlorotriflu- oroethane, as a second solvent, at 70 ± 1O⁰C, and then cooled, thus forming gel fiber. The air gap defined between the die and the second solvent was set to 3 mm, into which N gas was then blown.

[65] Subsequently, while trichlorotrifluoroethane, as a second solvent, at 15O⁰C, was jetted at a speed 10 times as fast as the draw speed to the cooled gel fiber, the fiber was passed through a roller at 135⁰C, thus primarily drawing the fiber at a draw ratio of 70%.

[66] Subsequently, the primarily drawn fiber was passed through a roller at 115°C while jetting trichlorotrifluoroethane, as a second solvent, at 120⁰C at a speed 20 times as fast as the drawing speed, thus secondarily drawing the fiber at a draw ratio of 20%, after which the fiber thus drawn was passed through a roller at 80⁰C without additional jetting, thereby tertiarily drawing the fiber. [67] Further, to the polyethylene fiber drawn at a total draw ratio of 30: 1 through three steps of drawing, trichlorotrifluoroethane at 9O⁰C was jetted at a speed 5 times as fast as the drawing speed, thus preparing high-tenacity polyethylene fiber. [68] <Example 2>

[69] High-tenacity polyethylene fiber was manufactured in the same manner as in

Example 1, with the exception that the total draw ratio was set to 40: 1 through three steps of drawing. [70] <Example 3>

[71] High-tenacity polyethylene fiber was manufactured in the same manner as in

Example 1, with the exception that the total draw ratio was set to 50: 1 through three steps of drawing. [72] The polyethylene fiber of Example 1 was measured for tenacity and elongation through the following methods. [73] The tensile properties were measured under conditions of a tensile speed of 300 mm/ min, a sample length of 250 mm, 2O⁰C and 65% RH, using an Instron material test system, and the denier of the sample was measured using a denier creel and was used to calculate tenacity. [74] As the results, all of the polyethylene fibers of Examples 1 to 3 could be confirmed to have tenacity of 30 g/d or more and high elongation of 3% or more. [75] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

[1] A method of manufacturing high-tenacity polyethylene fiber, comprising: mixing polyethylene, having a molecular weight average molecular weight ranging from 200,000 to 5,000,000, with a first solvent, which is a nonvolatile organic compound, thus obtaining a gel solution having an intrinsic viscosity of 17-23 dl/g; spinning the gel solution using a die, thus forming gel fiber; immersing the gel fiber in a second solvent, which is a liquid-phase volatile organic compound, at a high temperature close to a volatile point of the second solvent, and cooling it; and jetting the second solvent, which is a gas-phase volatile organic compound, to the cooled gel fiber, thus extracting the first solvent and drawing the gel fiber at a draw ratio of 30: 1-50:1.

[2] The method according to claim 1, wherein the first solvent is a hydrocarbon- based solvent having a boiling point of 35O⁰C or higher under atmosphere pressure.

[3] The method according to claim 1, wherein the second solvent is a liquid-phase volatile organic compound having a boiling point of 60~80°C or higher under atmosphere pressure.

[4] The method according to claim 1, wherein the drawing comprises: primarily drawing the fiber while jetting the second solvent at a high temperature greatly exceeding the volatile point thereof at a speed 10-20 times as fast as a drawing speed; secondarily drawing the primarily drawn fiber while jetting the second solvent at an intermediate temperature slightly exceeding the volatile point thereof; and tertiarily drawing the secondarily drawn fiber at a low temperature.

[5] A high-tenacity polyethylene fiber having tenacity of 30 g/d or more and high elongation of 3% or more, manufactured through the method of any one of claims 1 to 4.