CN113474495B - Method for producing thermoplastic polyurethane fibers with low shrinkage and use of the fibers - Google Patents

Abstract

The present invention relates to a method for producing thermoplastic polyurethane (TPU) fibers with low shrinkage, especially at high spinning speeds, and the use of the resulting fibers in fabrics, especially in clothes and shoes. The invention combines a high-speed spinning process with a thermal deformation process. This allows the production of TPU fibers at high productivity, which can greatly reduce costs. In addition, the resulting TPU fiber has a very low shrinkage of <10%, which makes it very suitable as a main raw material in fabrics.

Description

Method for producing thermoplastic polyurethane fibers with low shrinkage and use of the fibers

Technical Field

The present invention relates to a method for producing thermoplastic polyurethane (TPU) fibers having low shrinkage, especially at high spinning speeds, and the use of the fibers.

background

Most TPU fibers on the market have high elasticity and low modulus. High elastic TPU fibers have been used in fabrics in the form of auxiliary materials commonly known as spandex and cannot be used as the main raw material in fabrics due to their performance problems. It is used as an elastic component in fabrics. In contrast, low elasticity and high modulus TPU fibers can be used as the main raw material in fabrics. Low elasticity and high modulus TPU fibers have similar rigidity to polyamide and polyester fibers, and have high toughness, high modulus and low elongation, which allows them to be used in the same application fields as polyamide and polyester fibers.

Low elasticity and high modulus TPU fiber can be used as both auxiliary and main materials in fabrics. When used as an auxiliary material, it provides designers with more fabric design ideas/potentials. On the other hand, when used as a main material, it can produce full TPU (100% TPU) products such as uppers to replace popular PA and PET uppers. 100% TPU uppers can be 100% recycled, and have better wear resistance than uppers made of PA or PET fibers. This can broaden the application areas of TPU fibers. Therefore, low elasticity and high modulus TPU fibers are now receiving more and more attention.

The method for preparing high modulus TPU fibers requires a high take-up speed (winding speed) (see WO 2018/146192). However, the TPU fibers produced by the high-speed (>2000m/min) melt spinning process will shrink significantly (usually 20-35%) when treated with boiling water or steam. Products knitted from these fibers will also shrink significantly (usually 20-40%) during the steaming or ironing process. This large shrinkage will destroy the original good touch of the products and make them feel like plastic. In addition, this large shrinkage will also severely reduce the original product size, making the product dense and hard. Therefore, it is necessary to reduce the shrinkage rate of TPU fibers.

Many methods for obtaining low shrinkage fibers have been disclosed in the prior art.

US 2009/0311529 A1 discloses the production of high toughness and high modulus TPU monofilaments (hard TPU monofilaments) with reduced shrinkage as low as 10% at 140°C by an extrusion process, followed by an orientation process and finally a dynamic annealing process. The monofilaments produced by this method have a very high denier of 80-20,000. In this method, the extrudates have a diameter of 0.95 mm. After quenching in water, they go to an orientation process. This means that these two steps are not continuous. In addition, the invention does not involve the high-speed spinning technology at all.

KR 100587903 discloses a low shrinkage PU fiber obtained by a dry spinning process. In a heat treatment device (14), such as a heating tube or a heating roller with a length of 20-30 cm, the elastic fiber subjected to the spinning process is heat treated at 100° C. or above for 0.01-0.05 seconds. After being treated in a hot air oven at 100° C. for 1 hour, the resulting PU elastic fiber has a boiling water shrinkage of less than 7% and a heat shrinkage of less than 5%. In this application, a dry spinning process is used. There is no mention of a melt spinning process, especially a melt spinning process at a high speed.

US 5066439 discloses a continuous spin-draw process for preparing dimensionally stable polyester fibers having high strength and low shrinkage by melt spinning polyethylene terephthalate, stretching, applying a commingling treatment and then applying a relaxation heat treatment. During the stretching step, a heating plate at a temperature of 250-500° C. is used to help relax the fiber.

US 2009/0124149 A1 discloses a multifilament polyamide yarn with high tenacity and low shrinkage and a method for preparing the yarn, which comprises spinning molten nylon, relaxing and controlling the yarn tension, and then winding the yarn.

CN 102168319 B discloses a high strength, high modulus and low shrinkage polyester industrial yarn and a method for preparing these yarns. The method includes relaxing the yarn after spinning.

The prior art has not disclosed a method for preparing TPU fibers with low shrinkage and high toughness, especially with a shrinkage of less than 10%, at a high spinning speed.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a method for producing TPU fibers having low shrinkage, comprising (a) melt spinning a composition comprising a TPU resin at a spinning rate of 2000-5000 m/min; and (b) heat setting the obtained fibers.

Another object of the present invention is to provide a fiber obtainable by this method.

Another object of the present invention is to provide a fabric comprising the fiber.

Another object of the present invention is to provide a product comprising the fabric, wherein the product is a shoe, a trouser, a T-shirt, a chair net, a watch band or a hair band.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a method for producing TPU fibers, comprising (a) melt spinning a raw material composition comprising a TPU resin at a spinning rate of 2000-5000 m/min; and (b) heat setting the obtained fibers.

Each step is explained in detail below.

Step (a): melt spinning

Melt spinning is a technique in which a raw material composition in a molten state obtained by heating the raw material composition to a temperature equal to or higher than the melting point using an extruder or the like is discharged from a spinneret into a gas phase (e.g., air or, if necessary, cooled air). The arrangement of the nozzle is not limited. However, it is preferred that the nozzle is directed downward so that the molten composition (fiber) is discharged downward (pulled downward). The discharged molten fiber is cooled and solidified while being thinned in the gas phase, and then wound up at a certain speed.

It is also possible to melt the main component (TPU) of the raw material composition separately from the other components of the raw material composition so that the molten main component is mixed with the other components just before being discharged from the nozzle.

The apparatus for melt spinning is not particularly limited and an example thereof is shown in Fig. 1. The apparatus for producing fibers includes an extruder (not shown), a spinning pack 1 and a winder 2. The spinning pack is known in the art and is mainly composed of a melt reservoir and a spinneret.

For example, the raw material composition or its main component in the form of pellets is fed from a feeder to an extruder, melted in the extruder, and then the molten fibers are discharged from the nozzles (spinnerets) of the spinning pack into the gas phase.

When one or more additives (other components) such as a crosslinking agent are used, at least one mixer such as a static or dynamic mixer, preferably a static mixer, may be provided in the apparatus. In this case, the main component comprising TPU, in a preferred embodiment consisting of TPU, is melted in an extruder separately from the crosslinking agent; the crosslinking agent is mixed with the molten main component by using a mixer; and the mixed composition is then discharged from the nozzle of the spinning head in a molten state (i.e., the raw material composition in a molten state). The TPU of the raw material composition is crosslinked with a crosslinking agent during the melt spinning process. Alternatively, dry TPU granules are melted in an extruder and a crosslinking agent (0-20%) is fed at the end of the extruder. The blend of the crosslinking agent and the TPU melt passes through a mixer and a melt line, and after metering, it is pressed into a spinning assembly and finally comes out of a spinneret.

After exiting the spinneret, the extruded TPU fibers are stretched or oriented by passing through a series of godet rolls (such as GR1, GR2, and GR3 in FIG. 1) set at different linear speed ratios. It should be noted that the number of godet rolls is not limited to 3, and in fact can be 2 or more, but not more than 6, such as 2, 3, 4, 5, or 6. However, preferably there are 3 godet rolls.

During the spinning process, the fibers are subjected to a shrinkage control treatment, which is performed by heating the godet rollers to a certain surface temperature to fix the orientation in the TPU fibers, thereby controlling the shrinkage caused by high-speed spinning, for example, to less than 30%.

The surface temperature and velocity of GR1, GR2 and GR3 can be as follows:

GR1: temperature is 30-150°C, preferably 60-100°C, and independently, speed is 1000-6000 m/min, preferably 1000-4500 m/min,

GR2: temperature is 60-200°C, preferably 100-160°C, and independently, speed is 2000-6000m/min, preferably 2000-4500m/min,

GR3: temperature is 30-150°C, preferably 60-100°C, and independently, speed is 2000-6000 m/min, preferably 2000-4500 m/min.

In the present invention, speed relates to the peripheral speed of the godet rolls, unless otherwise indicated.

As the final step of the melt spinning process, the TPU fiber is wound onto a bobbin by a winder 2 (shown in FIG. 1 ) at a high winding speed of 2000-6500 m/min, preferably 2000-5000 m/min.

In the present invention, the spinning rate refers to the take-up (winding) speed.

In addition, the fibers can be oiled after exiting the spinneret and before reaching the godet rolls. This oiling step can lubricate the fibers and reduce friction between the fibers and the metal/ceramic components of the spinning line; allow static charges generated by the fibers' contact with machine components to dissipate; and hold the fibers together, making unwinding from the spun cake easier. The fibers can be oiled by any conventional spin finish.

The gas phase of melt spinning is not particularly limited and may be various gas phases such as an inert gas atmosphere and an air atmosphere, preferably an air atmosphere (air) from a cost perspective. The temperature of the gas phase may be any temperature lower than the melting point of the raw material composition and is -10°C to 50°C, more preferably 10-40°C, in consideration of cost.

The spinning conditions other than the spinning rate are not particularly limited, but are preferably set as follows.

-Spinning temperature

The spinning temperature is defined, for example, as the heating temperature not only in the extruder, but also in the polymer line and the spinning assembly. The spinning temperature is not particularly limited and can be appropriately changed according to the melting point of the raw material composition; from the perspective of spinnability, the spinning temperature is generally 180°C or higher, preferably 200°C or higher, more preferably 220°C or higher, but preferably not higher than 240°C. Especially when a TPU having a high hardness (e.g., Shore 60D or greater) is used, a higher spinning temperature (e.g., greater than 220°C, preferably 225°C or higher) makes it possible to spin at a higher spinning rate. From the perspective of suppressing thermal decomposition of the raw material composition, the spinning temperature is generally 240°C or lower, preferably 235°C or lower.

- Raw material composition

The raw material may include a resin comprising TPU, more preferably substantially consisting of TPU. The term "substantially consisting of" means that the resin includes TPU and, optionally, unintentional materials such as residues, contaminants, etc. In other words, the resin includes 95% by weight or more of TPU, preferably 99% by weight or more or preferably 99.5% by weight or more, especially 99.9% by weight or more, or even 100% by weight of TPU. TPU is not limited and one or more TPUs can be used. Useful TPUs are explained below.

TPU

There are no particular requirements for the TPU used in the present invention. The TPU is generally obtained by reacting (a) isocyanate, preferably organic diisocyanate, (b) polyol and (c) chain extender (polyol having a shorter chain length than long-chain polyol, usually short-chain diol) as essential components with each other without particular limitation in the presence of (d) catalyst and/or (e) auxiliary agent (adjuvant). In a preferred embodiment, the chain extender has a molecular weight of 50-499 g/mol. The polyol also called long-chain polyol has a number average molecular weight of 500-8×10 ³ g/mol. The reaction may be a one-step reaction allowing all the essential components (a) to (c) to react with each other in the presence of optional components (d) and (e) in a preferred embodiment, or a reaction having multiple steps allowing two or more components of (a) and (b) to react with each other to form a prepolymer and then reacting the prepolymer with the remaining essential components, preferably reacting with each other in the presence of components (d) and (e).

The hardness of the TPU is measured according to DIN ISO 7619-1, and is generally Shore 80A to Shore 80D, preferably Shore 80A to Shore 74D, and more preferably Shore 90A to Shore 70D.

The weight average molecular weight (Mw) of TPU is not limited, and is usually 50,000-800,000, preferably 80,000-600,000, and more preferably 80,000-400,000.

As (a) isocyanate, commonly known aromatic, aliphatic and/or araliphatic isocyanates can be used, preferably diisocyanates. Specifically, for example, one or more selected from the following can be used: 2,2'-, 2,4'- and/or 4,4'-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), 2,4- and/or 2,6-toluene diisocyanate (TDI), diphenylmethane diisocyanate, 3,3'-dimethylbiphenyl diisocyanate, 1,2-diphenylethane diisocyanate and/or benzene diisocyanate, tri-, tetra-, penta-, hexa-, hepta- and/or octamethylene diisocyanate, 2-methylpentamethylene-1,5-diisocyanate, 2-ethylhexylene diisocyanate, 1,2-diphenylethane diisocyanate and/or benzene diisocyanate, tri-, tetra-, penta-, hexa-, hepta- and/or octamethylene diisocyanate, 2-methylpentamethylene-1,5-diisocyanate, 2-ethylhexylene diisocyanate, 1,2-diphenylethane diisocyanate and/or benzene diisocyanate. 1,4-butylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,4-butylene diisocyanate, 1-diisocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate, IPDI), 1,4- and/or 1,3-bis(isocyanatomethyl)cyclohexane (HXDI), 1,4-cyclohexane diisocyanate, 1-methyl-2,4- and/or -2,6-cyclohexane diisocyanate and/or 4,4'-, 2,4'- and 2,2'-dicyclohexylmethane diisocyanate. More preferred isocyanates are 2,2′-, 2,4′- and/or 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), 2,4- and/or 2,6-toluene diisocyanate (TDI), hexamethylene diisocyanate (HDI) and/or IPDI, especially MDI and/or HDI, the most preferred isocyanate being MDI.

As (b) polyol, compounds generally known as isocyanate-reactive compounds can be used. For example, polyester polyols, polyether polyols, polycaprolactone polyols and/or polycarbonate polyols can be used; these are generally covered by the term "polyol". Preferably, component (b) can be a polyether polyol or a polyester polyol. In some cases, a mixture of a polyether polyol and a polyester polyol can be used. Commonly used polyols have, for example, a number average molecular weight of 500-8,000 g/mol, preferably 600-6,000 g/mol, more preferably 700-4,000 g/mol, and even more preferably 800-3,000 g/mol. The molecular weight of the polyol herein is the number average molecular weight.

Among such polyols, polyether polyol or polyester polyol may be preferably used, and among these two polyols, polyether polyol may be preferably used in view of microorganism corrosion resistance and water resistance, while polyester polyol may be preferably used in view of mechanical properties.

The polyether polyols can be obtained by known methods, for example by polymerizing alkylene oxides in the presence of a catalyst with addition of at least one initiator molecule containing 2 to 8, preferably 2 to 6, reactive hydrogen atoms. As catalysts, alkali metal hydroxides such as sodium or potassium hydroxide or alkali metal alkoxides such as sodium methoxide, sodium or potassium ethoxide or potassium isopropoxide can be used, or in the case of cationic polymerization, Lewis acids such as antimony pentachloride, boron trifluoride etherate or bleaching earth can be used as catalysts. In addition, double metal cyanides, known as DMC catalysts, can also be used as catalysts.

As alkylene oxides, preference is given to using one or more compounds having 2 to 4 carbon atoms in the alkylene group, for example ethylene oxide, 1,3-propylene oxide, tetrahydrofuran, 1,2- or 2,3-butylene oxide, in each case alone or in the form of a mixture, preferably ethylene oxide, 1,2-propylene oxide and/or tetrahydrofuran, most preferably tetrahydrofuran.

Possible starter molecules are, for example, ethylene glycol, diethylene glycol, glycerol, trimethylolpropane, pentaerythritol, sugar derivatives such as sucrose, sugar alcohols such as sorbitol, methylamine, ethylamine, isopropylamine, butylamine, benzylamine, aniline, toluidine, toluenediamine, naphthylamine, ethylenediamine, diethylenetriamine, 4,4′-methylenedianiline, 1,3-propylenediamine, 1,6-hexanediamine, ethanolamine, diethanolamine, triethanolamine and other di- or polyols or mono- or polyfunctional amines.

Examples of the polyether polyol may also include a ring-opening polymer of tetrahydrofuran (polytetramethylene glycol, PTMEG), a natural oil-based polyol such as castor oil, or an alkoxylated-modified natural oil or fatty acid.

Polyester polyol can be prepared by condensation of polyfunctional alcohol with 2-12 carbon atoms and polyfunctional carboxylic acid with 2-12 carbon atoms. Polyfunctional alcohol or polyfunctional carboxylic acid can have a functionality of about 2. Examples of polyfunctional alcohol can be ethylene glycol, diethylene glycol, butanediol or a combination thereof. Examples of polyfunctional carboxylic acid can be succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, isomers of naphthalene dicarboxylic acid or esters or anhydrides of the acid.

The polyether polyol or polyester polyol used herein has a hydroxyl value of about 15-225 mg KOH/g, preferably about 20-190 mg KOH/g, more preferably about 30-160 mg KOH/g, and most preferably about 40-140 mg KOH/g.

As (c) chain extenders, difunctional or trifunctional amines and alcohols can be used, in particular diols, triols or both. Such difunctional compounds are referred to as chain extenders and trifunctional or higher functional compounds are referred to as crosslinkers. As examples, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 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 glycol, dipropylene glycol and tripropylene glycol, 1,6-hexanediol and di(2-hydroxyethyl)hydroquinone; triols, such as 1,2,4-trihydroxycyclohexane, 1,3,5-trihydroxycyclohexane, glycerol and trimethylolpropane. Particularly preferred (c) chain extenders include 1,3-propylene glycol, 1,4-butanediol or 1,6-hexanediol. In some cases, a mixture of two chain extenders may be used.

In order to adjust the hardness of TPU, the molar ratio between the constituent unit components (b) and (c) can be changed within a relatively wide molar ratio range. The molar ratio of the total amount of component (b) to the chain extender (c) is 10:1-1:10, and a particularly useful range is 1:1-1:5, and as the content of (c) increases, the hardness of TPU increases.

Examples of the optional component (d) catalyst include, but are not particularly limited to, trimethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethylaminoethoxy)ethanol, diazabicyclo(2,2,2)octane and the like; in addition, organometallic compounds such as titanates; iron compounds such as iron(III) acetylacetonate; tin compounds such as tin diacetate, tin dioctoate and tin dilaurate; and dialkyltin salts of aliphatic carboxylic acids such as dibutyltin diacetate and dibutyltin dilaurate and their equivalents. The catalyst is usually used in an amount of 0.0001 to 0.1 parts by mass relative to 100 parts by mass of the (b) long-chain polyol.

Examples of optional component (e) auxiliary agents include: surfactants, nucleating agents, gliding and demoulding aids, dyes, pigments, antioxidants (e.g., with respect to hydrolysis, light, heat and discoloration), ultraviolet absorbers, flame retardants, reinforcing agents, plasticizers or fluidity improvers and crosslinking agents; one or more selected from these can be used.

The TPU used may be a polyether or polyester-based TPU. The term "polyether-based TPU" herein refers to a TPU prepared by using one or more polyether polyols as the main component (e.g., 50 wt % or more) of the (b) long-chain polyol. This also applies to polyester-based TPU.

As TPU produced from components (a) to (c) and optionally (d) and (e), it is also possible to use commercially available products, such as TPU from BASF TPU.

The raw material composition may contain the above-mentioned TPU as a main component. However, other additives may also be used in the raw material composition. The additives are not particularly limited; however, one or more additives used in the fiber field, such as flame retardants, fillers, pigments, dyes, antioxidants, ultraviolet absorbers, and light stabilizers may be added and used.

Among the additives, a crosslinking agent may be used together with TPU. Any type of crosslinking agent may be used, but it is preferred to use one or more crosslinking agents selected from reacted compounds prepared from one or more (i) polyols; one or more (ii) isocyanates, and optionally, other compounds. Considering the properties of the final product (fiber), it is preferred to use one or more of polyether or polyester crosslinking agents. The molecular weight of the crosslinking agent is generally lower than that of the above-mentioned TPU.

The crosslinkers used are NCO-terminated prepolymers having a functionality of 1.5 to 3, preferably 1.6 to 2.5, more preferably 1.8 to 2.1. The prepolymers have an NCO content of 3 to 15% by weight, preferably 4 to 10% by weight, more preferably 4 to 8% by weight.

The polyether crosslinking agent is prepared by using (i) polyols in which at least 50% by weight, preferably at least 80% by weight, more preferably at least 95% by weight of (i) polyol is selected from one or more polyether polyols. In other words, the polyether crosslinking agent contains one or more units derived from polyether polyols (polyether polyol units).

Although not particularly limited, the (i) polyether polyol may be selected from tetrahydrofuran (polytetramethylene glycol, PTMEG), alkylene oxides (especially ethylene oxide, propylene oxide and mixtures of these) and ring-opening polymers of alcohol adducts. More preferably, the (i) polyether polyol has a number average molecular weight (Mn) of 500-4.0×10 ³ g/mol, more preferably 600-3.0×10 ³ g/mol, particularly 0.8×10 ³ -2.0×10 ³ g/mol.

The polyester crosslinking agent is prepared by using (i) polyols wherein at least 50% by weight, preferably at least 80% by weight, more preferably at least 95% by weight of (i) polyol is selected from one or more polyester polyols. In other words, the polyester crosslinking agent contains one or more units derived from polyester polyols (polyester polyol units).

Preferably, the (i) polyester polyol has a number average molecular weight (Mn) of 600-4.0×10 ³ g/mol, more preferably 800-3.0×10 ³ g/mol, particularly 1.0×10 ³ -3.0×10 ³ g/mol.

(ii) isocyanate is not particularly limited, but can be selected from aromatic, aliphatic or alicyclic diisocyanates. For example, (ii) isocyanate can be selected from the compounds explained above for (a) isocyanate of preferred TPU. Among isocyanates, MDI can be preferably used for the crosslinking agent.

The amount of the polyether or polyester crosslinking agent is not limited, but is preferably set to 1 wt % or more, 3 wt % or more, or even 5 wt % or more based on the total amount of the raw material composition. When the main component (TPU resin) and other components (one or more crosslinking agents and/or one or more other additives) are melted separately, the total amount of the raw material composition can be obtained by adding up the amounts of the main component and other components.

The upper limit of the amount of the crosslinking agent is not particularly limited, but in a preferred embodiment the upper limit is 25 wt % or less, 20 wt % or less, more preferably 15 wt % or less based on the total amount of the raw material composition.

It is also possible to use non-polyether or non-polyester crosslinkers in which at least 50% by weight of (i) the polyol is selected from non-polyether polyols (polyols other than polyether polyols) or non-polyester polyols (polyols other than polyester polyols), such as polycaprolactone- and/or polycarbonate-polyols.

In a preferred embodiment of the present invention, the TPU is prepared from (a) PTMEG, (b) MDI and (c) 1,4-butanediol.

Step (b): Heat setting

After melt spinning of the TPU, the fibers are heat set.

Heat setting can be performed in two modes: off-line mode (mode A) and on-line mode (mode B).

In mode A, the bobbin containing the melt-spun TPU fiber is maintained in a heated oven to allow shrinkage to occur. During the heat setting process, the bobbin containing the melt-spun TPU fiber is placed on a rack and a heating medium is optionally passed through the oven. The oven can be vacuum or have an atmosphere such as air, nitrogen ( _N2 ) or water vapor. The heating medium can be steam, dry air or dry nitrogen. The heat setting temperature of the offline mode can be 70-130°C, preferably 80-120°C, more preferably 90-110°C; and the heat setting time of the offline mode can be 30-240 minutes, preferably 60-200 minutes, more preferably 60-180 minutes.

The TPU fibers produced by Mode A show very low shrinkage of less than 6%, preferably 0-3%.

In mode B, the TPU fiber produced by the melt spinning process is passed through a set of hot godet rollers without further stretching or orientation, wherein the number of godet rollers is, for example, 2 or more, but preferably not more than 6, and then the fiber is rewound on another bobbin. An example of an apparatus for mode B is shown in FIG2 . The set of hot godet rollers 3 (including 3 godet rollers, referred to as GR4, GR5 and GR6) is heated to a certain surface temperature to shrink the TPU fiber. Since the shrinkage occurs gradually as the TPU fiber passes through each roller, the rotation speed of the rollers and the winder is set to: GR4≥GR5≥GR6≥winder, and the surface temperature of the rollers and the winder is set to: GR5≥GR6≥GR4≥winder.

The surface temperature and speed of GR4, GR5 and GR6 can be as follows, wherein the above relationship between the surface temperature and speed of the godet roller must be followed:

GR4: temperature is 70-150°C, preferably 100-130°C, and independently, speed is 300-900m/min, preferably 400-800m/min,

GR5: temperature is 100-180°C, preferably 130-160°C, and independently, speed is 300-800m/min, preferably 400-700m/min,

GR6: temperature is 80-140°C, preferably 130-160°C, and independently, speed is 200-800 m/min, preferably 350-650 m/min.

The speed and temperature of the winding machine are not limited as long as they satisfy the above relationship. For example, the winding machine may have room temperature and a speed of 300-600 m/min.

The TPU fibers produced by Mode B show very low shrinkage of less than 10%, preferably less than 5%.

After heat setting, the TPU fiber is rewound again. During this period, oil can be applied to the fiber to facilitate processing in the subsequent twisting process.

After oiling, the TPU fiber is usually twisted in the S or Z direction to reduce friction in the subsequent knitting process. The twisting process can also be omitted according to different knitting techniques and performance requirements.

The TPU fiber having a DPF (denier per fiber) in the range of 3-50 produced by the method of the present invention has a low shrinkage of less than 10%, preferably less than 6%, a high tenacity of greater than 1.5 cN/dtex, preferably greater than 2.0 cN/dtex, and a breaking elongation of less than 150%, preferably less than 100%, more preferably less than 80%. In addition, the TPU fiber of the present invention has a DPF of 3-50, preferably 5-30, and more preferably 6-20 DPF.

Therefore, the present invention relates in a second aspect to a fiber obtainable by this method. The fiber of the invention has the advantageous properties described above.

Such properties make the fiber very suitable for making fabrics. The fabrics can be used in shoes, trousers, T-shirts, chair nets, watch straps, etc. The fabrics prepared by the process of the present invention show a shrinkage of less than 10%, preferably less than 5%.

The present invention combines a high-speed spinning process and a heat setting process. This allows the production of TPU fibers at a high productivity, which can greatly reduce costs. In addition, the resulting TPU fiber has a very low shrinkage of <10%, which makes it very suitable as a main raw material in fabrics. Therefore, the size, performance and touch of the fabric produced from the fiber can be well controlled during the steaming or ironing process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of an apparatus for melt spinning, wherein reference numeral 1 denotes a spinning pack, 2 denotes a winder, and GR1, GR2, and GR3 are godet rolls.

FIG. 2 illustrates an example of equipment for mode B, wherein reference numeral 3 denotes a set of heated rollers GR4, GR5 and GR6 and 4 denotes a winder.

Example

Measurement and test methods

The measurement and test methods are shown in Table 1.

Table 1

In addition, the shrinkage rate of the fabric is measured as follows: a piece of fabric with a size of 50 cm×50 cm is taken as a sample; two marks are drawn on the sample with a crayon; the distance between the two marks is measured and represented as L ₀ ; the sample is ironed for 15 seconds by using a commercial steam iron under the condition of ironing synthetic fibers; then cooled to room temperature, the distance between the two marks is measured and represented as L ₁ ; the fabric shrinkage rate is calculated according to the formula: shrinkage rate=(L ₀ -L ₁ )/L ₀ ×100%.

Material

The materials used in the examples are as follows.

A polyether-based polymer with a weight average molecular weight of 80 000-200 000 based on PTMEG, MDI and 1,4-butanediol is prepared. The product SP9519 (obtained from BASF, Shore D hardness 60-64) was used to prepare the fibers.

Finish oil: Finish oil (obtained from Takemoto Oil & Fat Co., Ltd) was used during the spinning process.

General Description of the Processes Used in the Examples

By using the apparatus shown in FIG1 , TPU was spun from a spinning pack at a temperature of 230° C. and the spun fiber was passed through godet rollers GR1, GR2 and GR3 having temperatures and speeds as shown in Table 2. The resulting fiber was then heat set in modes A and B, respectively, and the conditions and results are shown in Tables 3 and 4, respectively. The fiber was oiled after being spun from the spinning pack and before reaching the godet roller GR1; furthermore, the fiber was oiled again after heat setting to facilitate processing in the subsequent twisting process.

Table 2

table 3

Table 4

In Example 1, the fiber is subjected to shrinkage control treatment only during the spinning process and is not subjected to heat setting treatment after spinning; in Example 2, the fiber is subjected to shrinkage control treatment during the spinning process and is subjected to heat setting treatment in mode A, and in Example 3, the fiber is subjected to shrinkage control treatment during the spinning process and is subjected to heat setting treatment in mode B.

As can be seen from the above, the shrinkage of the fibers obtained from Examples 2 and 3 is much lower than that of Example 1, while the elongation at break of the fibers obtained from Examples 2 and 3 is higher than that of Example 1.

Claims (31)

1. A process for producing TPU fibers comprising:

(a) Melt spinning a composition comprising a TPU resin into fibers; and

(B) The fibers are heat-set and the resulting fibers,

Wherein the melt spinning is carried out at a spinning rate of 2000-6500m/min,

Wherein step (a) comprises passing the fibers through 2 or more, but no more than 6 godets, and heating the godets,

Wherein there are 3 godet rolls, GR1, GR2 and GR3,

Wherein GR1 is at 30-150deg.C; the temperature of GR2 is 60-200 ℃; and the temperature of GR3 is 30-150 c,

Wherein the GR1 speed is 1000-6000m/min; the GR2 speed is 2000-6000m/min; and the GR3 speed is 2000-6000m/min,

Wherein the hardness of the TPU resin is measured according to DIN ISO 7619-1 as Shore 80A to Shore 74D,

Wherein the TPU fibers have a shrinkage of less than 10%, wherein said shrinkage is shrinkage in boiling water measured according to GB/T6505-2008.

2. The process according to claim 1, wherein the melt spinning is carried out at a spinning rate of 2000-5000 m/min.

3. The method according to claim 1, wherein the temperature of GR1 is 60-100 ℃; the temperature of GR2 is 100-160 ℃; and the GR3 temperature is 60-100deg.C.

4. The method according to claim 2, wherein the temperature of GR1 is 60-100 ℃; the temperature of GR2 is 100-160 ℃; and the GR3 temperature is 60-100deg.C.

5. The method according to claim 1, wherein the GR1 is at a speed of 1000-4500m/min; the GR2 speed is 2000-4500m/min; and GR3 has a speed of 2000-4500m/min.

6. The method according to claim 2, wherein the GR1 is at a speed of 1000-4500m/min; the GR2 speed is 2000-4500m/min; and GR3 has a speed of 2000-4500m/min.

7. A method according to claim 3, wherein the GR1 is at a speed of 1000-4500m/min; the GR2 speed is 2000-4500m/min; and GR3 has a speed of 2000-4500m/min.

8. The method according to claim 4, wherein the GR1 speed is 1000-4500m/min; the GR2 speed is 2000-4500m/min; and GR3 has a speed of 2000-4500m/min.

9. The method according to any one of claims 1-8, wherein the heat setting is performed by holding the fibers in a heated oven.

10. The method according to claim 9, wherein the heat-setting temperature is 70-130 ℃; and the heat setting time is 30 to 240 minutes.

11. The process according to any one of claims 1-8, wherein the heat setting is performed without further stretching or orientation by passing the fibers through a set of heated godets.

12. The method of claim 11, wherein the number of thermally conductive godets is 2 or more, but not more than 6.

13. The method according to claim 11, wherein there are 3 heated godet rolls, GR4, GR5 and GR6.

14. The method according to claim 12, wherein there are 3 heated godet rolls, GR4, GR5 and GR6.

15. The method according to claim 13 or 14, wherein the temperature of GR4 is 70-150 ℃; the temperature of GR5 is 100-180 ℃; and the temperature of GR6 is 80-140 ℃.

16. The method according to claim 13 or 14, wherein the GR4 speed is 300-900m/min; the GR5 speed is 300-800m/min; and the GR6 speed is 200-800m/min.

17. The method according to claim 15, wherein the GR4 speed is 300-900m/min; the GR5 speed is 300-800m/min; and the GR6 speed is 200-800m/min.

18. The process according to any one of claims 1-8, wherein the hardness of the TPU resin is measured according to DIN ISO 7619-1 as shore 90A to shore 70D.

19. The process according to claim 17, wherein the hardness of the TPU resin is measured according to DIN ISO 7619-1 as shore 90A to shore 70D.

20. The process according to any one of claims 1 to 8, wherein the TPU resin is the reaction product of the following components (a) - (c), optionally in the presence of components (d) and (e):

(a) The isocyanate group is used as a reactive component,

(B) A polyhydric alcohol is used in the preparation of a polyol,

(C) The chain extender is used for the preparation of the chain extender,

(D) The catalyst is used for preparing the catalyst,

(E) And (5) an auxiliary agent.

21. A process according to claim 19, wherein the TPU resin is the reaction product of the following components (a) - (c), optionally in the presence of components (d) and (e):

(a) The isocyanate group is used as a reactive component,

(B) A polyhydric alcohol is used in the preparation of a polyol,

(C) The chain extender is used for the preparation of the chain extender,

(D) The catalyst is used for preparing the catalyst,

(E) And (5) an auxiliary agent.

22. The process according to claim 20, wherein the isocyanate is selected from the group consisting of 2,2' -, 2,4' -and/or 4,4' -diphenylmethane diisocyanate (MDI), 1, 5-Naphthalene Diisocyanate (NDI), 2, 4-and/or 2, 6-Toluene Diisocyanate (TDI), diphenylmethane diisocyanate, 3' -dimethylbiphenyl diisocyanate, 1, 2-diphenylethane diisocyanate and/or benzene diisocyanate, tri, tetra, penta, hexa, hepta and/or octamethylene diisocyanate, 2-methylpentamethylene-1, 5-diisocyanate, 2-ethylbutylene-1, 4-diisocyanate, 1, 5-pentamethylene diisocyanate, 1, 4-butylene diisocyanate, 1-diisocyanato-3, 5-trimethyl-5-isocyanatomethyl cyclohexane (IPDI), 1, 4-and/or 1, 3-bis (isocyanatomethyl) cyclohexane (di), 1, 4-cyclohexane diisocyanate, 1-methyl-2, 4-cyclohexane diisocyanate and/or 1, 4-cyclohexane and/or 1, 2' -cyclohexane and 2,4' -diisocyanate and 2,4' -cyclohexane.

23. The process according to claim 21, wherein the isocyanate is selected from the group consisting of 2,2' -, 2,4' -and/or 4,4' -diphenylmethane diisocyanate (MDI), 1, 5-Naphthalene Diisocyanate (NDI), 2, 4-and/or 2, 6-Toluene Diisocyanate (TDI), diphenylmethane diisocyanate, 3' -dimethylbiphenyl diisocyanate, 1, 2-diphenylethane diisocyanate and/or benzene diisocyanate, tri, tetra, penta, hexa, hepta and/or octamethylene diisocyanate, 2-methylpentamethylene-1, 5-diisocyanate, 2-ethylbutylene-1, 4-diisocyanate, 1, 5-pentamethylene diisocyanate, 1, 4-butylene diisocyanate, 1-diisocyanato-3, 5-trimethyl-5-isocyanatomethyl cyclohexane (IPDI), 1, 4-and/or 1, 3-bis (isocyanatomethyl) cyclohexane (di), 1, 4-cyclohexane diisocyanate, 1-methyl-2, 4-cyclohexane diisocyanate and/or 1, 4-cyclohexane and/or 1, 2' -cyclohexane and 2,4' -diisocyanate and 2,4' -cyclohexane.

24. The method according to claim 20, wherein the polyol is selected from the group consisting of polyester polyols, polyether polyols, polycaprolactone polyols and/or polycarbonate polyols.

25. The method according to any one of claims 21-23, wherein the polyol is selected from the group consisting of polyester polyols, polyether polyols, polycaprolactone polyols and/or polycarbonate polyols.

26. The method according to claim 20, wherein the chain extender is selected from the group consisting of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-pentanediol, 1, 3-pentanediol, 1, 10-decanediol, 1, 2-dihydroxycyclohexane, 1, 3-dihydroxycyclohexane, 1, 4-dihydroxycyclohexane, di-and triethylene glycol, dipropylene glycol and tripropylene glycol, 1, 4-butanediol, 1, 6-hexanediol and di (2-hydroxyethyl) hydroquinone; 1,2, 4-trihydroxycyclohexane, 1,3, 5-trihydroxycyclohexane, glycerol and trimethylolpropane.

27. The method according to any one of claims 21-24, wherein the chain extender is selected from the group consisting of ethylene glycol, 1, 2-propanediol, 1, 3-propanediol, 1, 2-pentanediol, 1, 3-pentanediol, 1, 10-decanediol, 1, 2-dihydroxycyclohexane, 1, 3-dihydroxycyclohexane, 1, 4-dihydroxycyclohexane, diethylene glycol and triethylene glycol, dipropylene glycol and tripropylene glycol, 1, 4-butanediol, 1, 6-hexanediol and di (2-hydroxyethyl) hydroquinone; 1,2, 4-trihydroxycyclohexane, 1,3, 5-trihydroxycyclohexane, glycerol and trimethylolpropane.

28. The method according to claim 25, wherein the chain extender is selected from the group consisting of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 2-pentanediol, 1, 3-pentanediol, 1, 10-decanediol, 1, 2-dihydroxycyclohexane, 1, 3-dihydroxycyclohexane, 1, 4-dihydroxycyclohexane, di-and triethylene glycol, dipropylene glycol and tripropylene glycol, 1, 4-butanediol, 1, 6-hexanediol and di (2-hydroxyethyl) hydroquinone; 1,2, 4-trihydroxycyclohexane, 1,3, 5-trihydroxycyclohexane, glycerol and trimethylolpropane.

29. A TPU fiber obtainable by the process according to any one of claims 1 to 28.

30. A fabric comprising TPU fibers of claim 29.

31. A product comprising the fabric according to claim 30, wherein the product is a shoe, a pant, a T-shirt, a chair net, a watchband, or a hairband.