EP4483003A1

EP4483003A1 - Process of preparing monofilament

Info

Publication number: EP4483003A1
Application number: EP23712774.1A
Authority: EP
Inventors: DeHui YIN; Qinghuai TANG; Huizhi YAN; Yin Zhang; Dian Jun CHEN
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2022-02-24
Filing date: 2023-02-23
Publication date: 2025-01-01
Also published as: JP2025505842A; WO2023161074A1; EP4483006A1; JP2025505867A; US20250171933A1; MX2024010398A; US20250163613A1; CN118742678A; WO2023160618A1; CN118786258A; MX2024010397A

Abstract

Disclosed is a process of preparing a monofilament, comprising, a) melt-spinning a thermoplastic polyurethane and forming a monofilament; b) cooling the monofilament under a temperature of 0 ℃ to 40 ℃; c) stretching the monofilament by at least two groups of rollers; d) heat-setting the monofilament; and e) winding the monofilament, wherein the thermoplastic polyurethane has a Shore hardness of no less than 65D measured according to DIN ISO 7619-1. Also disclosed is a monofilament prepared from the process.

Description

PROCESS OF PREPARING MONOFILAMENT

CROSS-REFERENCE TO RELATED APPLICATIONS
The present disclosure claims benefit to International Application No. PCT/CN2022/077711 filed February 24, 2022.

BACKGROUND

Thermoplastic polyurethane (TPU) materials are being massively used in manu-facturing fibers, fabrics, and garments. One way to process TPU materials is melt-spinning, where the TPU materials are melted and then spun to form rigid monofilaments. The rigid monofilaments are then knitted or woven to make articles of garments, for ex-ample.
One of the issues accompanying the process is that as-spun rigid TPU monofil-aments often express a high boiling water shrinkage (BWS) , often larger than 10%. That property may cause a large shrinkage of an article made from the monofilaments when it is treated by boiling water or steam.
Besides, the as-spun rigid TPU monofilaments express a high elongation at break of 60%to 120%. Due to this property, the monofilaments tension may be difficult to control in the following processing steps where uniformity of skein tension is needed for the monofilaments, such as winding, unwinding, twisting, knitting, and so on. Fluctu-ation of skein tension will then give rise to some defects of the final products, for exam-ple, garments.
US20090311529A1 disclosed a method for manufacturing a high tenacity mono-filament where a thermoplastic elastomer was oriented and dynamically annealed after being melted and extruded. A TPU composition with a Shore hardness of 57D was used. The thermal shrinkage of prepared monofilament was more than 10%.
US 20210238338 A1 disclosed a method for producing a TPU fiber. The TPU fiber was prepared by TPU with Shore hardness in a range of 35D to 75D. The TPU fi-ber still had a high elongation at break, which is larger than 70%.
US 11,136,431 B2 disclosed a method of making a filament. A crystalline ther-moplastic polyurethane composition was extrusion-spun at a speed of at least 1, 500 m/min to form a filament. The filament had a shrinkage of less than 15%after exposure to 80 ℃ for 90 seconds.
SUMMARY
In one aspect of the present disclosure, provided is a process of preparing a monofilament, comprising:
a. melt-spinning a thermoplastic polyurethane and forming a monofilament;
b. cooling the monofilament under a temperature of 0 ℃ to 40 ℃;
c. stretching the monofilament by at least two groups of rollers;
d. heat-setting the monofilament; and
e. winding the monofilament,
wherein the thermoplastic polyurethane has a Shore hardness of no less than 65D measured according to DIN ISO 7619-1.
Through the steps, a monofilament with a low elongation at break and a low boiling water shrinkage can be prepared.
In another aspect of the present disclosure, provided is a monofilament pre-pared according to the process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a process of preparing a monofilament according to some em-bodiments of the present disclosure.
FIG. 2 illustrates a schematic system for preparing a monofilament according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

Unless defined otherwise, all technical and scientific terms used herein have the meaning commonly understood by a person skilled in the art to which the present disclo-sure belongs. As used herein, the following terms have the meanings ascribed to them below, unless specified otherwise.
The articles “a” , “an” , and “the” mean one or more of the species designated by the term following said article.
In the context of the present disclosure, any specific values mentioned for a fea-ture (comprising the specific values mentioned in a range as the end point) can be re-combined to form a new range. Further embodiments of the present disclosure are dis-cernible from the claims, the description, and the examples. It will be understood that the aforementioned and hereinbelow still to be elucidated features of the subject matter of the present disclosure are utilizable not only in the particular combination indicated, but also in other combinations without leaving the realm of the present disclosure.
In the present disclosure, the following terms have their respective definitions given below.
“Boiling water shrinkage” refers to a decrease in length of a specimen as a re-sult of thermal treatment in boiling water, expressed as a percentage of its original length. In the present disclosure, boiling water shrinkage is measured under tension be-fore and after treatment according to the standard ASTM D2259-02.
“Elongation at break” refers to the ratio between changed length and initial length after breakage of a test specimen, measured according to the standard ISO2062: 2009, method A.
“Spinning speed” refers to the length of filament produced by melt-spinning per unit time.
“Linear speed” of a rotating object refers to a distance a point on the rotating ob-ject travels within a unit time.
“Linear density” of a filament refers to the mass per unit of length of the filament. In practice, the linear density of a filament is often calculated or denoted in the unit “de-nier” (shortened as “De” ) , measured according to the standard ISO 2060: 1994.
“Stress at 20%strain” refers to the stress when the strain of a material reaches 20%of its original dimension, measured according to the standard DIN 53504-S2.
“Tenacity” of a filament refers to the breaking force of the filament (in gram-force units) divided by the linear density, expressed in centi Newton per decitex (cN/dtex) , measured according to the standard ISO2062: 2009, method A.
Referring to FIG. 1, a process of preparing a monofilament is shown in a flowchart. The process comprises steps 102 through 112.
In step 102, melt-spinning a thermoplastic polyurethane and forming a monofil-ament.
In step 104, cooling the monofilament under a temperature of 0 ℃ to 40 ℃.
In step 106, stretching the monofilament by at least two groups of rollers.
Optionally in step 106, relaxing the monofilament by a group of relaxing rollers.
In step 110, heat-setting the monofilament.
In step 112, winding the monofilament.
FIG. 2 illustrates a chart in which a system for preparing a monofilament accord-ing to some embodiments of the present disclosure is operating. A melt-spinning device 210 melts and spins a thermoplastic polyurethane to form a plurality of monofilaments.
The monofilaments then enter a quench tank 220 filled with cooling water or other coolant. Two directing rollers 224 and 230 are set to change the direction of the monofilaments. The directing roller 224 is set inside the quench tank and submerged within the cooling water or coolant. The directing roller 230 is set outside the quench tank. The directing rollers 224 and 230 pull the monofilaments out of the quench tank and redirect them to the following rollers for being stretched.
Three groups of rollers 242, 244, and 246 are set with different linear speeds R1, R2, and R3, respectively. Two heating devices 252 and 254 are arranged between the group of rollers 242 and 244, and between the group of rollers 244 and 246, respectively. The following requirement is satisfied: R2 is larger than R1, and R3 is larger than R2. The monofilaments are stretched by the groups of rollers 242 and 244, and by the groups of rollers 244 and 246. The heating devices 252 and 254 heat the monofila-ments. Any of the groups of rollers 242, 244, and 246 may include more than one roller, and preferably three rollers. The heating device 252 or 254 may be a hot water tank, a hot air oven, or other heating device. The heating device 252 may be different from the heating device 254. In one embodiment, the heating device 252 is a hot water tank while the heating device 254 is a hot air oven.
After the monofilaments move past the group of rollers 246, they are drawn to a group of relaxing rollers 260. The group of relaxing rollers 260 rotate at a linear speed Rr that is less than R3. The group of relaxing rollers 260 may include more than one roller, and preferably three rollers.
The monofilaments then enter a hot air oven 270 for heat-setting and are wound by a winder 290 to form a bobbin or bobbins after passing a directing roller 280.
Thermoplastic polyurethane
The thermoplastic polyurethane employed in the present disclosure has a Shore hardness of no less than 65D measured according to DIN ISO 7619-1. Preferably, the thermoplastic polyurethane has a Shore hardness of 68D to 90D, more preferably a Shore hardness of 70D to 80D, measured according to DIN ISO 7619-1.
The thermoplastic polyurethane has a stress at 20%strain of not less than 18 MPa, preferably a stress at 20%strain of 22 MPa to 45 MPa, more preferably a stress at 20%strain of 25 MPa to 38 MPa.
The thermoplastic polyurethane used in the process of the present disclosure comprises reaction product of (A) a polyol; (B) a diisocyanate; and (C) a chain extender.
The thermoplastic polyurethane used in the process of the present disclosure is generally obtained, without being particularly limited, by allowing the polyol, the diisocy-anate and the chain extender as the essential components to react with each other, if necessary, in the presence of a catalyst and/or an auxiliary agent. The reaction can be a one-stage reaction allowing the whole of the essential components to react with each other in one stage in an embodiment in the presence of the optional components such as an auxiliary agent, or a reaction having a plurality of stages allowing some of the pol-yol and the diisocyanate to react with each other to form a prepolymer and then allowing the prepolymer and the rest of the essential components to react with each other, pref-erably in the presence of an auxiliary agent.
Examples of the auxiliary agent may be selected from, without being particularly limited to an antioxidant, a hydrolysis stabilizer, an ultraviolet absorber, a flame retard-ant, a plasticizer, a flowability improver, or a cross-linking agent; one or more selected from these can be used. The amount of the auxiliary agent can be determined by a skilled person according to practical application.
The thermoplastic polyurethane used in the process of the present disclosure may have a weight-average molecular weight in a range of 50,000 to 400,000 g/mol, preferably 60,000 to 300,000 g/mol, such as 80,000 to 200,000 g/mol.
Polyol
The thermoplastic polyurethane used in the process of the present disclosure has (A) a polyol as one of the raw materials.
As the polyol used in the present disclosure, compounds generally known as isocyanate reactive compounds can be used. In particular, the polyol used in the pre-sent disclosure may be selected from the group consisting of polyester polyols, polyeth-er polyols, and any mixture thereof.
Preferably, the functionality of the polyol used in the present disclosure is in the range from 1.5 to 2.5, preferably 1.8 to 2.3, more preferably 1.9 to 2.1, for example 2.
The polyether polyols may be obtained by known methods, for example by polymerization of alkylene oxides with addition of at least one starter molecule which comprises from 2 to 8, preferably from 2 to 6, reactive hydrogen atoms in the presence of a catalyst. As the catalyst, it is possible to use alkali metal hydroxides such as sodi-um or potassium hydroxide or alkali metal alkoxides such as sodium methoxide, sodium or potassium ethoxide or potassium isopropoxide or, in the case of cationic polymeriza-tion, Lewis acids such as antimony pentachloride, boron trifluoride etherate or bleaching earth as the catalyst. Furthermore, double metal cyanide compounds, known as DMC catalysts, can also be used as the catalyst.
As the alkylene oxide, preference is given to using one or more compounds hav-ing from 2 to 4 carbon atoms in the alkylene radical, e.g., ethylene oxide, 1, 2-propylene oxide, tetrahydrofuran, 1, 2-or 2, 3-butylene oxide, in each case either alone or in the form of mixtures, and preferably ethylene oxide, 1, 2-propylene oxide and/or tetrahydro-furan, most preferably tetrahydrofuran.
Possible starter molecules are, for example, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, pentaerythritol, sugar derivatives such as sucrose, sugar alcohol such as sorbitol, and other dihydric or polyhydric alcohols.
Examples of polyether polyols can also include a ring-opening polymer of tetra-hydrofuran (polytetramethylene glycol, PTMEG) , natural oil-based polyether polyols like alkoxylated castor oil or other polyether polyols based on natural oils or fats, e.g., those obtained by ring opening reaction of epoxidized unsaturated vegetable oils, polyether polyols based on saccharides.
The polyester polyol may be prepared by condensation of polyfunctional alco-hols having from 2 to 12 carbon atoms with polyfunctional carboxylic acids having from 2 to 12 carbon atoms. The polyfunctional alcohols or polyfunctional carboxylic acids may have a functionality of around 2. The examples of the polyfunctional alcohols may be ethylene glycol, diethylene glycol, butanediol, or a combination thereof. The examples of the polyfunctional carboxylic acids may be succinic acid, glutaric acid, adipic acid, su-beric acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, the isomers of naphthalenedicarboxylic acids, or the ester or anhydrides of the acids mentioned.
Preferably, the polyol used in the present disclosure is selected from the group consisting of polyester diols, polyether diols, and any mixture thereof.
Diisocyanate
The thermoplastic polyurethane used in the process of the present disclosure has (B) a diisocyanate as one of the raw materials.
Diisocyanate of the present disclosure may be selected from any organic com-pound having two isocyanate groups per molecule.
Diisocyanate of the present disclosure may be an aliphatic diisocyanate, or ara-liphatic diisocyanate, or cycloaliphatic diisocyanate, or aromatic diisocyanate.
For example, the diisocyanate may contain from 3 to 40 carbon atoms, and in various embodiments, the diisocyanate may contain from 4 to 20, from 5 to 24, or from 6 to 18, carbon atoms. In certain embodiments, the diisocyanate is a symmetrical aliphat-ic or cycloaliphatic diisocyanate.
Examples of suitable diisocyanates of the present disclosure include isomers of diphenylmethane diisocyanates, 1, 5-naphthylene diisocyanate, isomers of tolylene diiso-cyanates, 3, 3'-dimethyldiphenyl diisocyanate, 1, 2-diphenylethane diisocyanate, phe-nylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pen-tamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, 2-methylpentamethylene-1, 5-diisocyanate, 2-ethylbutylene-1, 4-diisocyanate, isophorone diisocyanate, isomers of bis(isocyanatomethyl) cyclohexanes, 1-methyl-2, 4-cyclohexane diisocyanate, 1-methyl-2, 6-cyclohexane diisocyanate, 4, 4'-dicyclohexylmethane diisocyanate, 2, 4'-dicyclohexylmethane diisocyanate, 2, 2'-dicyclohexylmethane diisocyanate, and any mix-ture thereof; more preferably the diisocyanate is selected from the group consisting of isomers of diphenylmethane diisocyanates, 1, 5-naphthylene diisocyanate, isomers of tolylene diisocyanates, hexamethylene diisocyanate, isophorone diisocyanate, and any mixture thereof; in particular, the diisocyanate is diphenylmethane diisocyanate, hexa-methylene diisocyanate, and any mixture thereof, especially 4, 4’ -diphenylmethane diiso-cyanate.
In an embodiment of the present disclosure, one diisocyanate is used.
Chain extender
The thermoplastic polyurethane used in the process of the present disclosure has (C) a chain extender as one of the raw materials.
Chain extender of the present disclosure may comprise aliphatic, araliphatic, ar-omatic, and/or cycloaliphatic compounds having two functional groups. For example, the chain extender suitable for the present disclosure may be selected from bifunctional alcohols, in particular diols, such as alkanediols having from 2 to 10 carbon atoms in the alkylene radical.
As examples of the chain extender suitable for the present disclosure, it may be mentioned ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 2-pentanediol, 1, 3-pentanediol, 1, 10-decanediol, 1, 2-dihydroxycyclohexane, 1, 3-dihydroxycyclohexane, 1, 4-dihydroxycyclohexane, diethylene glycol and triethylene gly-col, dipropylene glycol and tripropylene glycol, 1, 6-hexanediol and bis (2-hydroxyethyl) hydroquinone; triols such as 1, 2, 4-trihydroxycyclohexane, 1, 3, 5-trihydroxycyclohexane, glycerol and trimethylolpropane. A particularly preferable chain extender includes 1, 3-propanediol, 1, 4-butanediol, or 1, 6-hexanediol. In certain cases, it is possible to use the mixture of two chain extenders.
Preferably, in order to form the thermoplastic polyurethane of the present dis-closure, the polyol, the diisocyanate, and the chain extender are used with the molar ra-tio of isocyanate groups from the diisocyanate to the isocyanate-reactive groups from both the polyol and the chain extender, in the range from 0.9: 1.0 to 1.1: 1.0, preferably from 0.95: 1.0 to 1.05: 1.0, and more preferably from 0.97: 1.0 to 1.03: 1.0.
The process of preparing a monofilament is given below in details.
In step (a) , the thermoplastic polyurethane is passed through a spinneret, which is operating under a spinning temperature. The spinning temperature may be more than 150 ℃, preferably in a range of 180 ℃ to 250 ℃, more preferably in a range of 200 ℃to 240 ℃. The spinning temperature may keep the thermoplastic polyurethane in a mol-ten state.
The thermoplastic polyurethane has a Shore hardness of no less than 65D, preferably, a Shore hardness of 68D to 90D, more preferably a Shore hardness of 70D to 80D, measured according to DIN ISO 7619-1.
Step (a) of the process of the present disclosure is not particularly limited and can be carried out by a skilled person. Melt-spinning is a technique in which a raw ma-terial composition in a molten state obtained by heating the raw material composition to a temperature equal to or higher than the melting point by using an extruder or the like is discharged from a spinneret into a quenching tank. The positioning of the spinneret is not limited. However, it is preferable to direct the spinneret downward so that the molten composition (the molten filament) is discharged downward (drawn down) . The dis-charged monofilament is cooled and solidified in the atmosphere while being made fine, and then is taken up at a certain speed.
Preferably, in step (a) , the thermoplastic polyurethane is melt-spun at a spinning speed of less than 500 m/min.
In step (b) , the monofilament is cooled under a temperature of 0 ℃ to 40 ℃. The cooling may be realized by employing a quench tank filled with water, iced water, or other coolant.
Preferably, the monofilament is cooled under a temperature of 4 ℃ to 30 ℃.
In step (c) , the monofilament is stretched by at least two groups of rollers. The groups of rollers may rotate with different linear speeds. The rollers may be heated or not. The rollers are preferably driving rollers, which is to say, the rollers are not driven by the monofilament.
In some embodiments, the at least two groups of rollers comprise a first group of rollers rotating at a first linear speed R1 and a second group of rollers rotating at a second linear speed R2 in sequence. R2 is no less than R1, and each group of rollers comprises at least three rollers. The first group of rollers is closer to the spinneret, while the second group of rollers is farther to the spinneret. The difference of linear speeds at which the first and second groups of rollers rotate causes the monofilament to stretch.
In some embodiments, the rollers are godet rollers. The first and/or second group of rollers comprises three, five, or more rollers.
Preferably, R1 is in a range of 10-100 m/min.
Preferably, a ratio of R2 to R1 is in a range of 1.5-5. The larger the ratio of R2 to R1 is, the stronger stretching the monofilament is subject to between the first and second groups of rollers.
Preferably, the monofilament is heated under a temperature of 70 ℃ to 100 ℃after the monofilament passes the first group of rollers and before the monofilament passes the second group of rollers. The heating may be realized by passing the mono-filament through a tank filled with hot water or an oven filled with hot air.
In some embodiments, the at least two groups of rollers further comprise a third group of rollers operating at a third linear speed R3, R3 is no less than R2, and the third group of rollers comprises at least three rollers.
Preferably, a ratio of R3 to R1 is in a range of 1.5-10. The larger the ratio of R3 to R1 is, the stronger the overall stretching the monofilament is subject to between the first and third groups of rollers.
Preferably, the monofilament is heated under a temperature of 100 ℃ to 130 ℃after the monofilament passes the second group of rollers and before the monofilament passes the third group of rollers. The heating is realized by passing the monofilament through an oven filled with hot air or steam. Alternatively, the heating is accomplished by contacting the monofilament with a heated surface.
Optionally, after being stretched by the at least two group of rollers in step (c) and before being heat-set in step (d) , the monofilament is relaxed by a group of relaxing rollers in step (f) . The group of relaxing rollers is rotating at a relaxing linear speed that is lower than the linear speed at which the last group of the at least two group of rollers is rotating. For example, if the monofilament is stretched by three groups of rollers that are rotating at linear speeds R1, R2, and R3 in sequence, the linear speed of the group of relaxing rollers Rr is lower than that of the third group of rollers R3. The decrease of the linear speeds may cause the monofilament to relax and the stress along and/or with-in the monofilament to be alleviated.
The group of relaxing rollers may comprise three or more rollers.
In step (d) , the monofilament is heat-set, preferably under a temperature of 130 ℃ to 170 ℃. The heat-setting may cause the monofilament to retain its dimension and properties. Heat-setting may be realized by employing a hot air oven.
The monofilament is wound to form a bobbin or bobbins in step (e) , which can be collected and packaged for transportation or storage.
In some embodiments, the monofilament has a linear density of 70 deniers to 700 deniers, measured according to ISO 2060: 1994.
In some embodiments, the monofilament has a boiling water shrinkage of no more than 10%, preferably no more than 9%, measured according to ASTM D2259-02.
In some embodiments, the monofilament has a bi-component structure or a hol-low structure.
Examples
The below table lists the relevant testing methods:
Table 1
The TPU materials used in the examples were as follows.
TPU 1 (obtained from BASF with a hardness of Shore 64 D) had a weight-average molecular weight of 80,000-160,000 based on poly (1, 4-butylene adipate) with number-average molecular weight of 1,000 g/mol, methylene diphenyl diisocyanate (MDI) , and 1, 4-butanediol was used for preparing the monofilaments.
TPU 2 (obtained from BASF with a hardness of Shore 74 D) with weight-average molecular weight of 80,000-160,000 based on poly (1, 4-butylene adipate) with number-average molecular weight of 1,000 g/mol, MDI and 1, 4-butanediol was used for preparing the monofilaments.
TPU 3 (obtained from BASF with a hardness of Shore 78 D) with weight-average molecular weight of 80,000-160,000 based on poly (1, 4-butylene adipate) with number-average molecular weight of 1,000 g/mol, MDI, and 1, 4-butanediol was used for preparing the monofilaments.
TPU 4 (obtained from BASF with a hardness of Shore 74 D) with weight-average molecular weight of 80,000-160,000 based on poly (tetramethylene ether) glycol with number-average molecular weight of 1,000 g/mol, MDI, and 1, 4-butanediol was used for preparing the monofilaments.
TPU 5 (obtained from BASF with a hardness of Shore 78 D) with weight-average molecular weight of 80,000-160,000 based on poly (tetramethylene ether) glycol with number-average molecular weight of 1,000 g/mol, MDI, and 1, 4-butanediol was used for preparing the monofilaments.
The TPU materials were melt-spun by a spinning machine operating at a tem-perature of 220-240 ℃ and monofilaments were formed. The monofilaments were then cooled in a quench tank filled with water of 25 ℃. After being cooled, the monofila-ments then passed through a first, second, and third groups of rollers, rotating at linear speeds R1, R2, and R3, respectively. Between the first and second groups of rollers, the monofilaments were heated by a first hot water tank under a temperature of 80 ℃. Between the second and third groups of rollers, the monofilaments were heated by a second hot air oven under a temperature of 110 ℃. The monofilaments were then heat-set under a temperature of 145 ℃.
The table below lists the parameters and testing data of the TPU materials and monofilaments prepared therefrom.
Table 2
From the above data, it is suggested that the hard TPU having a Shore hard-ness higher than 65D, after being melt-spun and processed, can result in monofilaments that have low boiling water shrinkage and elongation at break. Besides, the process is simple and production cost of the monofilament is low, compared with sophisticated and energy-consuming processes.

Claims

A process of preparing a monofilament, comprising:

(a) melt-spinning a thermoplastic polyurethane and forming a monofilament;

(b) cooling the monofilament under a temperature of 0 ℃ to 40 ℃;

(c) stretching the monofilament by at least two groups of rollers;

(d) heat-setting the monofilament; and

(e) winding the monofilament,

wherein the thermoplastic polyurethane has a Shore hardness of no less than 65D measured according to DIN ISO 7619-1.
The process of claim 1, wherein the thermoplastic polyurethane has a Shore hardness of 68D to 90D, preferably a Shore hardness of 70D to 80D, measured according to DIN ISO 7619-1.
The process of claim 1, wherein in step (a) , the thermoplastic polyurethane is melt-spun at a spinning speed of less than 500 m/min.
The process of claim 1, wherein the thermoplastic polyurethane has a stress at 20%strain of not less than 18 MPa, preferably a stress at 20%strain of 22 MPa to 45 MPa, more preferably a stress at 20%strain of 25 MPa to 38 MPa, measured according to DIN 53504-S2.
The process of claim 1, wherein the monofilament is cooled under a temperature of 4 ℃ to 30 ℃ in step (b) .
The process of claim 1, wherein the at least two groups of rollers comprise a first group of rollers rotating at a first linear speed R1 and a second group of rollers rotating at a sec-ond linear speed R2 in sequence, R2 is no less than R1, and each group of rollers com-prises at least three rollers.
The process of claim 6, wherein R1 is in a range of 10-100 m/min.
The process of claim 6, wherein a ratio of R2 to R1 is in a range of 1.5-5.
The process of claim 6, wherein the monofilament is heated under a temperature of 70 ℃ to 100 ℃ after the monofilament passes the first group of rollers and before the monofilament passes the second group of rollers.
The process of claim 6, wherein the at least two groups of rollers further comprise a third group of rollers operating at a third linear speed R3, R3 is no less than R2, and the third group of rollers comprises at least three rollers.
The process of claim 10, wherein a ratio of R3 to R1 is in a range of 1.5-10.
The process of claim 6, wherein the monofilament is heated under a temperature of 100 ℃ to 130 ℃ after the monofilament passes the second group of rollers and before the monofilament passes the third group of rollers.
The process of claim 1, further comprising, after step (c) and before step (d) , step (f) relaxing the monofilament by a group of relaxing rollers.
The process of claim 6, wherein the monofilament is heat-set under a temperature of 130 ℃ to 170 ℃ in step (d) .
A monofilament prepared according to a process of any of claims 1 through 12.
The monofilament of claim 15 having a linear density of 70 deniers to 700 deniers, measured according to ISO 2060: 1994.
The monofilament of claim 15 having a boiling water shrinkage of no more than 10%, preferably no more than 9%, measured according to ASTM D2259-02.
The monofilament of claim 15 having a bi-component structure or a hollow structure.