ABSTRACT

The present invention relates to a polyamide fiber with improved comfort management properties. The present invention also discloses a method for obtaining such fiber and articles made therefrom. The polyamide fiber is produced from a hygroscopic polyamide in a multilobal cross section profile. The hygroscopic polyamide fiber is produced preferably from polyamide 5.X, X being an integer from 4 to 16. Most preferably polyamide 5.6, which is a biobased polyamide obtained from pentamethylenediamine and is derived from sugar-based renewable feedstocks. The present invention thus discloses a polyamide fiber and articles made therefrom for sportswear and leisurewear applications, with improved water absorption, wicking and drying properties, wherein the sweat is transported away from the skin and is quickly dried, thereby reducing the wet sensation and chill during activity. The present invention provides freshness and comfort by maintaining a pleasant skin temperature and microclimate.

BACKGROUND

There is an increasing demand for comfort in sportswear and leisurewear clothing. According to the World Sports Activewear, "comfort is the most important thing in clothing", it is number one in consumer expectations. Comfort affects not only the well-being of the wearer but also their performance and efficiency. For instance, if an active sportsperson wears a clothing system with poor breathability, heart rate and rectal temperatures will increase much more rapidly than while wearing breathable sportswear.

Polyamide fiber is the most suitable fiber for improving comfort among the synthetic fibers available in the market. Polyamide is very soft, smooth and pleasant to the skin. The high flexibility, lightness and abrasion resistance provide a very comfortable sensation, in addition to the well-balanced moisture behavior. Polyamide also has high durability, good physical and chemical properties, easy-care and fast drying properties. Polyamide, also known as nylon, is a linear condensation polymer composed of repeated primary bonds of amide group. The amide group -(-CO-NH-)- provides hydrogen bonding between polyamide intermolecular chains. A polyamide fiber is generally produced by melt-spinning extrusion and is available in staple fiber, tow, monofilament, multi-filament, flat or texturized form. Therefore, polyamide is a promising candidate for sportswear, underwear, leisurewear and other next-to-skin applications. The next-to-skin fabric is normally a soft, skin-friendly fabric composed of hydrophilic and/or porous fibers, and is designed to wick the sweat away from the body, maintaining a pleasant skin microclimate. Sweating is a necessary mechanism for body cooling in response to high levels of body heat production. The skin microclimate quickly becomes humid during sweating. For efficient cooling the evaporated sweat needs to be transported as water vapor through the clothing and air layers adjacent to the skin and/or by convection through openings in the clothing.

The next-to-skin fabric controls the microclimate temperature and humidity of the skin. With low metabolic activity the fabric must reduce air movement, as the microclimate is maintained by the still air. With higher metabolic activity, heat and moisture should be transported from the fabric to cool the skin. Moisture control is then performed by absorption, by transportation or by ventilation.

Absorption reduces skin humidity and retains relative comfort in moderate activities with limited sweating, whereas in higher metabolic activities and intensive sweating, the moisture may remain in the clothing system and may be detrimental to heat balance at a later stage as wetting of clothing reduces the effective thermal insulation, what reduces the comfort and causes the post-chilling effect after cessation of the activity. Hence, in higher sweating conditions, the transporting principle should be applied, where the sweating is transported away from the skin by wicking and capillarity, thereby maintaining the skin dry.

Synthetic fibers are durable, easy-care, but are mostly hydrophobic. Using hydrophobic textiles next to skin quickly increases humidity with sweating, hence hydrophobic fabrics need to be engineered to transport water away quickly by capillarity spaces between fibers and yarns. On the other hand, hydrophilic and/or hygroscopic fibers absorb and transport water through the fiber itself and by capillarity, thus facilitating the evaporation.

Highly hygroscopic fibers also lead to a physiologically problematic lengthening of the drying time. If the drying time becomes too long, the post-exercise chill is unavoidable, as the sweat wetted shirt loses its thermal insulation. This mechanism is normally found in natural and regenerated fibers due to their very high hydrophilic properties. In addition, wet skin may cause skin irritations or even moisture-generated dermatoses. For example, wool possesses high absorbing capacity and can handle small amounts of moisture without losing their insulation properties. Wool can be used as a next-to-skin fabric and may keep the skin relatively dry. When the fabric becomes saturated, however, the moisture control is reduced. Cotton has excellent properties for clothing worn in normal wear situation with only a limited amount of sweating. In this situation, cotton can buffer smaller sweat impulses and, hence keeping the microclimate drier and more comfortable. But in the field of sport textiles, which generates higher amount of liquid sweat for prolonged times; cotton is only recommendable at the outer side of two face materials and in combination with a synthetic inner side at the skin. If cotton is used as the only or main fiber component, the textile becomes soaked with moisture and wet rapidly, clinging onto the body. Moisture absorbed in garments gradually reduces thermal insulation. When activity drops and sweating ceases, the drying of wet clothing layers may deprive the body of more heat than is generated by metabolic rate, the results is a post-exercise chilling effect that may endanger heat balance and result in hypothermia. The post-exercise chill can be avoided by a short drying time. Indeed, short drying time is one of the main prerequisites for a good wear comfort for sportswear.

In summary, the textile needs to have a reasonable hydrophilicity, high wicking speed and high drying rate in order to be effective in maintaining a pleasant microclimate and comfort. If the hydrophilicity is too high, as in the case of natural fibers, the drying rate may be delayed as water is absorbed and retained inside the fiber for longer periods. A poor wicking may also lead to saturated regions and reduced transport and drying rates. Therefore, an optimal balance should be achieved among hydrophilicity, wicking and fast drying properties.

There has been a significant amount of research activity for improving the moisture management of polyamide textiles. Several approaches have been adopted, such as adding hydrophilic materials into the fiber matrix or onto the fiber surface like polyvinylpyrrolidone (PVP) and ethoxylated polyamide; or blending polyamide with another hydrophilic polymer in bi-component melt-extrusion. An example of the sheath-core polyamide multifilament is disclosed by JP 2012211406, where a polyalkylene oxide-modified product is used as core material. This approach requires bi-component equipment and the drying rate and wicking speed are not provided.

In still another approach, cooling agents are inserted in the polyamide fiber matrix in order to improve the cooling and moisture management properties. Chinese patent applications CN 104178839 and CN 103088459 disclose this method. Disadvantages of this approach include lack of fast drying rate, water absorption and wicking speed. The cooling mechanism may also lead to uncomfortable sensation during active sweating, such as hypothermia due to excessive cooling.

Chinese patent application CN103882550 also proposes a cooling polyamide fiber with the use of a cooling agent, such as inorganic metal oxide particles, but adds PVP to the fiber with the intention to improve the water absorption. A drawback of the use of PVP is the fact that the occurrence of pyrrolidone as a by-product tend to causes fiber yellowing, thereby affecting the desired mechanical and chemical properties for textile applications. In addition, the fast wicking and drying behavior are not demonstrated and could cause discomfort during excessive sweating and sports activities.

A few patents have attempted to provide a moisture management polyamide fiber by solely altering the fiber cross section. Filament with cross sections other than circular are commonly proposed for aesthetic effects, moisture management and lightness. Examples of non-circular profiles include "dogbone", "trilobal", "zig-zag", "king", "flat" and "hollow". This approach aims to increase the capillarity effect by introducing grooves and micro-channels lengthwise the filament to generate spaces within the fiber and among the fibers. For instance, the trilobal profile (also known as Y) is well known and widely used for providing luster and brightness to the article; however, it does not increase capillarity, softness and surface area, as they do not provide deep micro-channels. JP5206640 discloses a modified cross section polyamide with radial lobes; however, water absorption, wicking and drying rate are not assessed or improved.

US 2015013047 disclosed a cooling polyamide yarn, with the use of cooling inorganic additives, modified cross section and low crimp module. The disclosed cross section is a flat cross section. A disadvantage of this cross section is the fact that a flat fiber profile leads to more skin coverage, lower insulation, less entrapped air and more contact points with the skin what may reduce the skin sensorial wear comfort. It does not offer capillarity and does not increase wicking speed and drying rate, hence not being suitable for high sweating activity. In addition, the flat cross section evaluated in the experiments of the present invention has shown poor processing behavior, what suggests that a flat cross section may be more difficult to be processed by melt-spinning. Last, EP 2554721 discloses a hygroscopic polyamide 5.6 fiber; however, without the additional advantage of high wicking speed and drying rate as are offered by the present invention. Hence, patent number EP 2554721 does not offer a solution for comfort management of sportswear textiles, where wicking and higher drying rates are desired. There is still no existing fiber in the market that offers at the same time hydrophilic properties, cooling effect, and wicking.

In view of the above, there is a need for a synthetic fiber with intrinsically improved comfort management properties that mimics the softness and comfort of natural fibers with the additional advantage of fast drying and wicking properties.

There is also a need to provide a solution for having a comfortable polyamide textile including:

Optimal hygroscopicity, for absorbing sweat without feeling wet, and maintaining the ideal microclimate insulation.

- Enhanced wicking speed, for efficiently transporting the sweat away from the skin.

Fast drying rate, for maintaining the skin dry and avoiding uncomfortable post-exercise chilling sensation.

Sensorial skin comfort, for obtaining a pleasant touch due to texturized multifilament yarns having a plurality of very fine filaments.

Therefore, it is an object of the present invention to provide a polyamide fiber, process thereof and articles made therefrom with superior comfort management properties, thereby improving the skin microclimate and generating a pleasant sensation during sports and high sweating activities. BRIEF DESCRIPTION OF THE INVENTION

The present invention is a solution for obtaining highly comfortable and refreshing polyamide fibers in order to provide a pleasant feeling for the wearer.

The present invention thus provides a polyamide fiber with improved comfort management comprising a hygroscopic polyamide, being an aliphatic biobased polyamide selected from the group consisting of polyamide 5.X, X being an integer from 4 to 16 and mixtures thereof, said fiber having a multilobal cross section characterized by having at least 2 coalescent centers and at least 5 equally dimensioned oblong lobes, each coalescent center connecting at least 3 equally dimensioned oblong lobes according to an angular symmetry between the adjacent equally dimensioned oblong lobes.

It has been surprisingly found that such a polyamide fiber shows substantially higher hygroscopicity, water drying rate, water spreading rate and water absorption compared to non-hygroscopic polyamide with round cross section. It has been proven that by enhancing the water absorption, wicking and dryings rates, which leads to a better moisture management, comfort is also substantially improved.

The present invention also aims at a method for obtaining said polyamide fiber with improved comfort management, wherein the polyamide fiber is obtained by melt-spinning extrusion of a polyamide composition comprising the hygroscopic polyamide, for example by using a new multilobal cross sections spinneret.

Also, the present invention proposes a polyamide article comprising the polyamide fiber with improved comfort management as defined above and below in the following paragraphs; and a method for obtaining such a polyamide article, wherein the polyamide fiber of the invention is transformed by texturizing, drawing, warping, knitting, weaving, nonwoven processing, garment manufacturing or a combination thereof.

Then, another object of the present invention is the use of said polyamide fiber with improved comfort management as defined above and below in the following paragraphs in order to increase the comfort management of polyamide articles made therefrom, notably for textile articles.

DETAILED DESCRIPTION OF THE INVENTION Definitions

The expression "polyamide fiber" in the sense of the present invention is the generic term including the following spun articles: a fiber, a monofilament, a multifilament and a yarn. A "polyamide article" according to the invention is a transformed or treated polyamide fiber and includes staple fibers, any flock or any textile composition made of polyamide fiber, especially fabrics and/or garments. In the below description, the terms "fiber", "yarn" and "filament" can be used indifferently without changing the meaning of the invention. Polyamide fiber with improved comfort management

The present invention provides a polyamide fiber with improved comfort management, comprising a hygroscopic polyamide, being an aliphatic biobased polyamide selected from the group consisting of polyamide 5.X, X being an integer from 4 to 16 and mixtures thereof, said fiber having a multilobal cross section characterized by having at least 2 coalescent centers and at least 5 equally dimensioned oblong lobes, each coalescent center connecting at least 3 equally dimensioned oblong lobes according to an angular symmetry between the adjacent equally dimensioned oblong lobes.

Hygroscopic polyamide

The hygroscopic polyamide is an aliphatic polyamide composed of polyamide 5.X, X being an integer from 4 to 16 or mixtures thereof. Polyamide 5.X is made of pentamethylenediamine and an aliphatic dicarboxylic acid(s) as raw materials. The list of potential dicarboxylic acids is the following: butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), heptanedioic acid (pimelic acid), octanedioic acid (suberic acid), nonanedioic acid (azelaic acid), decanedioic acid (sebacic acid), undecanedioic acid, dodecanedioic acid, brassylic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid. All those diacids are commercially available.

Polyamides 5.X have the advantage of being able to be manufactured from biomass according to ASTM6866. As pentamethylenediamine can also be prepared from bio-resources according to ASTM6866, the resulting polyamide can be produced from 40% to 100% of bio-resources.

The amino terminal groups (ATG) content of those biobased polyamides is advantageously from 25 to 60 equivalent/ton, and the carboxyl terminal groups (CTG) is advantageously from 45 to 90 equivalent/ton. Those amino/carboxyl end groups contents are measured according to the methodology explained hereinafter in the experimental part.

The hygroscopic polyamide is preferably polyamide 5.X, with X being an even integer from 4 to 16, such as polyamide 5.4, polyamide 5.6, polyamide 5.8, polyamide 5.10, polyamide 5.12, polyamide 5.14, polyamide 5.16 and mixtures thereof. Even more preferably X is 6 or 10, and advantageously 6 such as polyamide 5.6 (Nylon 5.6), also called poly(pentamethylene adipamide), which is made by polycondensation reaction of pentamethylenediamine and adipic acid as raw materials. The preferred polyamide 5.6 may have a viscosity index (IVN) in the range of 100 to 200 ml/g, preferably between about 120 and 170. This IVN is measured according to the standard ISO 307, which is explained hereinafter in the experimental part. A particularly preferred polyamide 5.6 according to the present invention has an IVN (viscosity index) of from 138 to 142, and ATG (amine terminal groups) from 38 to 42.

The hygroscopic behavior of the polyamide 5.6 is at least 4%, as measured according to the methodology explained hereinafter in the experimental part. The hygroscopic feature is due to the odd/even configuration of the diamine (5 carbons) and diacid (6 carbons), what leads to misalignment of intermolecular bonds, resulting is less hydrogen bonds and hence more water-friendly accessible sites within the molecules.

The polyamide fiber according to the invention comprises advantageously more than 75% by weight of hygroscopic polyamide, preferably more than 85% by weight and even more preferably more than 95% by weight, based on the total weight of the fiber.

Indeed, the polyamide fiber according to the invention can contains other polymers such as PA 6.6, PA 6.10 and PA 6 and/or additives like plasticizers, antioxidants, stabilizers such as heat or light stabilizers, colorants, pigments, nucleating agents such as talc, matifying agents such as titanium dioxide or zinc sulphide, processing aids, biocides, viscosity modifiers, cooling agents, catalysts, Far Infrared Rays emitting minerals, anti-static additives, functional additives, optical brightening agents, nanocapsules, anti-bacterial, anti-mite, anti-fungi or other conventional additives.

Generally, the amount of additives in the fiber represents up to 25 %by weight, more preferably up to 10% by weight. In a further embodiment of the present invention, a cooling agent or thermo regulating agent is employed. The cooling agent may comprise any far infrared ceramic powder, inorganic fillers such as inorganic metal oxides (ex: Ti02, Zr02, MgO, Sn02, ZnO, BaO), jade powder, zirconia powder, silica powder, mica, boron nitride, calcium carbonate, barium carbonate, magnesium carbonate, aluminum silicate, alumina, zeolite and talc. The thermo regulating agent also comprises phase change materials such as paraffin or endothermic substances such as sugar alcohol like xylitol or erythritol. Cooling or thermo regulating agents provide good thermal conductivity, fast heat conduction through the body to produce cool contact feeling, through slow endothermic and fast heat dissipation characteristics.

Multilobal cross section

The polyamide fiber of the present invention has multilobal transversal cross section characterized by having at least 2 coalescent centers and at least 5 equally dimensioned oblong lobes, each coalescent center connecting at least 3 equally dimensioned oblong lobes according to an angular symmetry between the adjacent equally dimensioned oblong lobes. In the polyamide fiber according to the invention, a "lobe" is understood to be the oblong part/section of the fiber cross section that is connected to at least one coalescent center.

In the polyamide fiber according to the invention, a "coalescent center" is understood to be the converging point of at least 3 lobes.

According to a preferred embodiment, the multilobal cross section has 2 to 6 coalescent centers, preferably 2 or 3 coalescent centers, each coalescent center connecting symmetrically 3 or 4 equally dimensioned oblong lobes according an angle of 120° or 90° respectively between adjacent lobes, and the best results are obtained when each coalescent center connects symmetrically 3 equally dimensioned oblong lobes according to an angle of 120°between adjacent lobes.

A schematic example of multilobal cross section is illustrated in Figure 1. On Figure 1, there are 3 coalescent centers shown by letter a, b represents a lobe and in this particular example there are 7 lobes, and c represents the 120° angle that is reproduced between each adjacent lobe.

Others cross section profiles are illustrated in figure 3, in which profiles according to the present invention are exemplified by "A" to "F" (120° symmetry) and "I" and "J" (90° symmetry). The profiles "G", "H", and "K" are given for comparison only. When we have a multilobal cross section having at least 2 coalescent centers and 3 lobes arranged by 120° angular symmetry, it means that all adjacent lobes are connected by an angle of 120°. For instance, 2 coalescent centers have a total number of 5 lobes, 3 coalescent centers have a total number of 7 lobes, and so forth. For any "N" number of coalescent centers, the number of lobes is "(N*2)+l". The multilobal cross section having at least 2 coalescent centers of 4 lobes that are arranged by 90° angular symmetry means that any adjacent lobes are connected by 90°. For instance, 2 coalescent centers connects 7 lobes, 3 coalescent centers connects 10 lobes, and so forth. For any "M" number of coalescent center, the number of lobes is "(M*3)+l". The lobes are symmetrically angular, which means any adjacent lobes are connected by 90°.

Therefore, the total number of lobes of the cross section can be from 5 (image "A" of figure 3) to 13 (image "F" of figure 3). The best cross section sharpness and processability is achieved with cross section having angle of 120° between adjacent lobes and more specifically, with the cross section containing 2 (image "A" of figure 3) and 3 (image "B" of figure 3) coalescent centers having 5 lobes and 7 lobes respectively.

Non-symmetric cross sections, such as sample "G" and "H" of figure 3, exhibit poor processability and should be avoided. These cross sections are shown for comparison only, as well as sample "K" of figure 3, which is the conventional circular cross section and does not belong to the present invention. In general, flat cross sections like "G" and "H" of figure 3 are more difficult to be processed.

The specific multilobal cross sections of the invention generate special micro and continuous concavities lengthwise the fibers. The capillarity and higher surface area of the fibers of the invention increase the water absorption, spreading and drying rates, thereby improving the moisture management and comfort of the textiles made therefrom. A less compact yarn is obtained, contributing to more air space within the filaments which increases the insulation, capillarity, and thermoregulation of the textiles made therefrom. The higher surface area of the cross sections of the present invention allow the sweat to spread out, what significantly contributes to faster sweat evaporation, so the textile article made therefrom dries quicker and the wearer remains comfortable and dry while exercising. The thermal insulation of the textile article made therefrom is thus maintained, which avoids the post-exercising chilling effect of wet clothes. The handle and softness are also significantly improved because of the lower flexural rigidity generated by the irregular and preferred bending direction of the cross section, as opposite to the resilient behavior of round and trilobal cross section (Y shapes). Similar phenomenon of softness is also observed in the "bean" shape cross section of cotton fiber. For instance, "image "B" of Figure 3 has a preferred bending direction towards the deeper concavity.

The polyamide fiber according to the invention has advantageously an overall dtex of about 40 to 300, and a dpf (dtex per filament) of about 0.1 to 5, a tenacity (at break) from 20 to 80 cN/Tex and an elongation (at break) from 20% to 90%. Process for obtaining a polyamide fiber with improved comfort management

First embodiment: FLAT YARNS

The invention also provides a method for obtaining the polyamide fiber with improved comfort management as described above. The polyamide fiber is obtained by melt-spinning extrusion. The "melt-spinning extrusion" is understood to mean the extrusion process of converting the polyamide into polyamide fibers. The polyamide(s) may be fed to the melt-spinning device in pellet, powder or melt form. The method includes any conventional extrusion spinning means suitable for melt-spinning extrusion of polyamides, these means being well known by a person skilled in the art, such as single-screw extruder, double-screw extruder, bi-component extruder and grid spinning head. The melt-spinning extrusion can be further defined as being LOY (low- oriented yarn), POY (partially oriented yarn), FDY (fully drawn yarn), FOY (fully oriented yarn), LDI (Low denier Industrial) or HDI (High denier Industrial).

The melt-spinning extrusion advantageously comprises the following steps: al. Feeding the polyamide composition comprising the hygroscopic polyamide in the form of a melt, pellet or powder into the inlet of a screw extruder,

a2. Melting, homogenizing and pressurizing the polyamide composition,

a3. Spinning the molten polyamide composition into a fiber,

a4. Cooling down the fiber and winding.

In step al the hygroscopic polyamide is advantageously continuously introduced as a melt, pellet or powder into the inlet of a screw extruder. In step a2, the polyamide is preferably melted, homogenized and pressurized inside the screw extruder, preferably at a temperature from 260 to 310?C, which is above the melting temperature of the polyamide, and at an extrusion pressure from 30 to 70 bar.

Then, according to step a3, the molten polyamide is spun into fibers (or yarns or filaments) preferably at a temperature from 260 to 3102C, spinning pack pressure from 150 to 250 Bar and a spinning pack flow rate from 3 to 8 kg/h, with the use of a spinning screen-pack containing filtering elements and a spinneret.

A special spinneret should be used during step a3 to obtain the multilobal cross section having coaiescent centers, equally dimensioned oblong lobes and angular symmetry.

A spinneret is a metal plate containing orifices which are used for extruding the polymer into the desired cross section and size.

The special spinneret comprises multilobal orifices, each orifice having at least 2 coaiescent centers, at least 5 equally dimensioned oblong lobes and an angular symmetry between adjacent equally dimensioned oblong lobes.

The multilobal orifices have preferably 2 to 6 coaiescent centers, each coaiescent center connecting symmetrically 3 or 4 equally dimensioned oblong lobes according an angle of 120° or 90° respectively between adjacent lobes.

The best results are obtained for multilobal orifices having 2 to 6 coaiescent centers, preferably 2 or 3 coaiescent centers, each coaiescent center connecting symmetrically 3 equally dimensioned oblong lobes according to an angle of 120°between adjacent lobes. A schematic example of orifice of the special spinneret is given on figure 2. On Figure 2, there are 3 coaiescent centers shown by letter a, b represents a lobe and in this particular example there are 7 lobes, and c represents the 120° angle that is reproduced between each adjacent lobe.

For each orifice of the spinneret according to the invention, a "lobe" is understood to be a section, orifice or hole, where the molten polymer passes through during extrusion to form solid filaments upon cooling and which is going to form the oblong part/section of the fiber cross section. For each orifice of the spinneret according to the invention, a "coalescent center" is understood to be the point of at least 3 lobes where the molten polymer does pass through during extrusion, but that is going to connect the at least 3 lobes after coalescence. The coalescent centers and equally dimensioned oblong lobes of the orifices of the spinneret are necessary for obtaining a good polymer distribution in the orifice upon extrusion; whereas, the angular symmetry ensures stability, shape and sharpness of the cross section, enhancing the grooves and capillarity of the fibers.

The multilobal cross section having coalescent centers of 3 lobes connected by angles of 120° are illustrated in images "A" to "F" of figure 3. The multilobal cross section having coalescent centers of 4 lobes connected by angles of 90° are illustrated in images "I" and "J" of figure 3.

The phenomenon of coalescence is well understood by those skilled in the art, it is a process by which two or more separate sections (also called lobes) merge during contact to form a single section. Therefore, the lobes are not connected within each other in the spinneret; instead, the lobe sections are merged upon extrusion to form a single continuous filament. A coalescent center is then the center of separate lobes, especially 3 or 4 lobes, according to the present invention.

The best cross section sharpness and processability is achieved with symmetric profile having angle of 120° between adjacent lobes. More specifically, the cross section of 2 (sample "A") and 3 (sample "B") coalescent centers, having "5 lobes" and "7 lobes" respectively.

Each set of lobes from the samples of figure 3 correspond to a single continuous filament upon extrusion, which are joined by the coalescence phenomenon. The total number of orifices (sets of lobes) in the spinneret can be designed to produce yarns from 10 to 200 filaments. The lobes have oblong shape and are of exactly same dimensions.

Step a4 is the step of cooling down the fibers (or yarns or filaments) until the solidified form and winding the polyamide fibers into bobbins. A spinning oil can also be added onto the fiber at this step. The winding speed is from 3000 m/min to 6500 m/min.

In the present invention, the extruder can be equipped with a metering system for introducing polymers and optionally additives such as masterbatches into the main polymer, at step al and/or a2 and/or a3. Additional additives can be introduced during the method of the invention or may be present in the hygroscopic polyamide polymer. The additives listed above. These additives are generally added in the polymer or at step al and/or a4 of the melt-spinning extrusion, in an amount of 0,001% to 10% by weight of the polyamide fiber. In a further embodiment of the present invention, a cooling agent or thermo regulating agent is introduced also at step al, separately from the hygroscopic polyamide, with the use of a dosing apparatus such as gravimetric or volumetric feeding pump. The cooling or thermo regulating agent may be in the form of powder, liquid or solid masterbatch. The cooling or thermo regulating agent is advantageously introduced in an amount of 0.5% to 20.0%, preferably 1.0 to 5.0% by weight of the total weight of the polyamide fiber.

Second embodiment: TEXTURED YARNS According to a second embodiment of the present invention, the polyamide fiber obtained from the first embodiment is then texturized to produce textured yarns with higher elasticity, volume and softness. This process comprises any technology known by those skilled in the art such as false-twist texturizing, false-twist - fixed texturizing and air-jet texturizing. Most preferably false-twist texturing. The method can include the following steps:

bl. The fiber is removed from the package and passes to the delivery rolls.

b2. The fiber passes through a heater, then to a cold zone.

b3. The fiber passes through a spindle containing rotating discs (friction aggregates)

b4. intermingling points and coning oil are applied to the fiber.

b5. The fiber is wound into bobins.

Wherein a drawing ratio is given to the fiber by altering the speed ratio of the bl and b5.

In step bl, the fiber is advantageously placed in a creel and is unwound from the bobbins to the delivery roll. Step b2 preferably involves passing the fiber inside a heater, with temperature from 120°C to 400°C, in order to assist the mechanical action of stretching and twisting the fibers by softening (making more malleable). The fiber is then cooled.

Step b3 is where the twist, volume, crimp and texture are generated in the fiber. The amount of twist is changed by altering the speed of the discs, discs arrangement and the D/Y relationship. The D/Y ratio changes the ratio of speeds between the friction discs and the linear speed of the fiber. This ratio is preferably from 1.0 to 2.8. The disc arrangement is advantageously from 1/2/1 to 1/8/1, being guide disc/work disc/guide disc.

According to step b4, intermingling points and coning oil are applied to the fiber in order to provide lubrication and to improve physical and aesthetic features, in the case of the intermingling. The interlaces per meter are preferably at least 30 per meter. Step b5. is the winding process, where the fiber is wound into bobbins; the winding speed can vary from 150 m/min to 1500 m/min. The drawing ratio is given to the fiber by altering the speed ratio of step bl and step b5, and is an important parameter of the process for achieving the desired linear density. The drawing ratio is advantageously from 1.10 to 4.00. Yarns of more than 1 ply is possible, such as from 1 to 8 plies. Polyamide article

The polyamide fiber according to the invention can then be transformed into a polyamide article, notably a textile fabric and/or garment. A polyamide article according to the invention is preferably a fiber, a multifilament yarn, a flock, a woven, a knitted or non-woven fabric or a textile article made from the polyamide fiber of the invention (defined above) or obtained from the process according to the invention.

The textile article may be any textile article known in the art including, but not limited to woven fabric, knitted fabric, nonwoven fabric, ropes, cords, sewing thread, and so forth. In the case of clothing, the best results are achieved on fabric with mass per unit area of less than 200 g/m ² , most preferably less than 150 g/m ² .

Method for obtaining a polyamide article

The methods for transforming the polyamide fiber into a polyamide article like a textile fabric or garment are well known by the skilled person in the art. Indeed, the polyamide fiber can be transformed into a polyamide article by texturizing, drawing, warping, knitting, weaving, nonwoven processing, garment manufacturing or a combination thereof. These articles are subsequently used in a large number of applications, in particular in hosiery, underwear, sportswear, outerwear and leisurewear.

ADVANTAGES

Further advantages of the polyamide fibers with improved comfort management and articles made therefrom, according to the present invention, are highlighted below:

A novel polyamide 5.6 fiber with intrinsic hygroscopicity and capillarity effect is disclosed in the present invention. As opposite to the chemically modified hydrophilic polyamides offered in the market.

- Novel multilobal cross section profiles are disclosed in the present invention.

The polyamide articles exhibit higher rate of water absorption, wicking and drying, when compared to non-hygroscopic polyamides with round cross sections.

The synergy among hygroscopicity, capillarity and higher surface area of the cross section speeds up the water drying rate so that the wearer feel dry and comfortable even after intense sweating.

- The mechanical and chemical properties of the polyamide article are not significantly changed.

The current method is simple and makes use of conventional and well-kwon extrusion machinery. The cross section profile of the present invention improves handle and softness of the fiber because of the lower flexural rigidity due to the irregular and preferred bending direction, as opposite to the resilient behavior of round and triloba! cross section. Similar phenomenon is observed in the "bean" shape cross section of cotton fiber.

Wear comfort background and assessment methods

Wear comfort is a complex phenomenon but in general it can be divided into four different main aspects: a) Thermophysiological wear comfort influences a person ^' s thermoregulation, it comprises heat and moisture transport processes through the clothing. Key notions include thermal insulation, breathability and moisture management; b) Skin sensorial wear comfort characterizes the mechanical sensations that a textile causes at direct contact with the skin, pleasant perceptions include smoothness and softness, whereas unpleasant would be scratchy, too stiff, or clings to sweat-wetted skin; c) Ergonomic wear comfort deals with the fit of the clothing and the freedom of movement it allows. It is mainly dependent on the garment ^' s pattern and the elasticity of the materials; d) Psychological wear comfort is affected by fashion, personal preferences, ideology etc.

Thermophysiological comfort is based on the principle of energy conservation. All the energy produced within the body by metabolism, has to be dissipated in exactly the same amount from the body, by the respiratory heat loss (breathing), the dry heatflux comprising radiation, conduction, convection, and the evaporative heatflow caused by sweating. If more energy is produced than dissipated, the body suffers from hyperthermia. And too high a heat loss leads to hypothermia.

Wear comfort is never the consequence of only one single parameter; instead it is a result of fiber composition, fabric structure, clothing layering system, chemical finishing and so forth. Several research studies have proven that fabric constructional parameters and chemical finishing are as important as fiber composition. For instance, lightweight, porous and thin fabrics are desirable for sports textiles, in addition to hydrophilic and quick-drying properties. The water vapor is diffused through the inter-yarn spaces, through inter-fiber spaces, through the fiber substance itself, and through the free air spaces within textiles.

Chemical finishing includes mainly hydrophilic topic treatments and is intended to increase the hydrophilic behavior of hydrophobic textiles. The drawback of chemical finishing is the fact that it is a non-durable treatment and may last a few home-washing cycles only, whereas fibers with intrinsic moisture management properties last the entire life time of the textile article.

Regarding the yarn composition, the use of filament yarns leads to too smooth and flat textile surfaces directly at the skin. This structure shows too many contact points with the skin, and the fabric is perceived as too smooth and clinging to sweat-wetted skin. Flat filament yarns provide poor skin sensorial perception, whereas spun yarns or textured yarns provide better skin sensation. Textured yarns provide less contact points with the skin and higher insulation, softness and pleasant touch. Protruding fiber ends are generated, as well as a more 3D structure, in spun yarns and textured yarns, which act as spacers between skin and textile. Yarn cross section with grooves, pores and capillarity channels along the filament are also important to increase the wicking speed and surface area, what leads to wicking and faster drying rate. Air is also an important characteristic for clothes. Air is welcome not only for lightness but also for temperature regulation. A layer of air between garment and skin helps to reduce temperature variations. By reducing the contact points between the skin and garment, air circulates freely and lets the body breath.

Moisture management properties are normally assessed by water absorption, vertical wicking, horizontal wicking, air permeability, water vapour transmission, thermal resistance and drying rate. The standard AATCC

195 from "American Association of Chemists and Colorists" can be used for measuring liquid moisture management properties of textiles. Water absorbance can be assessed by AATCC 79. Vertical wicking of textiles is normally evaluated by AATCC 197, whereas horizontal wicking can be measured by AATCC 198.

AATCC 199 and AATCC 200 can be used to measure the drying time of textiles at different conditions, using a gravimetric moisture analyzer. Apart from the methods above, thermo-physiological and sensorial tests are also available for assessing comfort, such as using a heated hot plate (ASTM F 1868; ISO 5085-1, 1989; ISO

11092, 1993), thermal mannequin, as well as human trials.

Other details or advantages of the invention will become more clearly apparent in the light of the examples given below.

EXAMPLES

A series of polyamide articles, including comparative polyamide articles and control polyamide articles are formed and evaluated for process ability, water wicking rate, water absorption rate, water drying rate, hygroscopicity, mechanical properties, IVN (viscosity index), ATG (terminal amino groups) and CTG (carboxylic terminal groups). Table 1 summarizes the samples.

Amino terminal group content (ATG)

The amino end group (ATG) content was determined by a potentiometric titration method. The quantity of 2 grams of polyamide is added to about 70 ml of phenol 90%wt. The mixture is kept under agitation and temperature of 409C until complete dissolution of the polyamide. The solution is then titrated by 0.1N HCI at about 25?C The result is reported as equivalent/ton (eq/ton). In the case of analyzing fibers and articles, any residue or spin-finish must be previously removed.

Solution viscosity (IVN) The determination of the solution viscosity (IVN) is performed according to ISO 307. The polyamide is dissolved in formic acid 90%wt at 252C at a concentration of 0.005g/ml, and its flow time is measured. The result is reported as ml/g. Carboxylic terminal group content (CTG)

The carboxylic terminal group (CTG) content was determined by a titration method. The quantity of 4 grams of polyamide is added to about 80 ml of benzyl alcohol. The mixture is kept under agitation and temperature of 200?C until complete dissolution of the polyamide. The solution is then titrated by 0.1N of potassium hydroxide in ethylene glycol. The result is reported as equivalent/ton (eq/ton). In the case of analyzing fibers and articles, any residue or spin-finish must be previously removed.

AATCC 195 - Liquid moisture management of textiles (evaluation of horizontal water wicking speed and water absorption time)

The liquid moisture management properties are evaluated by placing a fabric specimen between two horizontal (upper and lower) electrical sensors. A predetermined amount of test solution that aids the measurement of electrical conductivity changes are dropped onto the center of the upward-facing test specimen surface. The test solution is free to move in three directions: radial spreading on the top surface, movement through the specimen from top surface to the bottom surface, and radial spreading on the bottom surface of the specimen. During the test, changes in electrical resistance of specimen are measured and recorded. A moisture management tester (MMT) is used with this method. The results of water absorption (seconds) and water spreading speed (mm/second) are given by this method.

AATCC 199 Liquid water drying speed

Water is applied to the test specimen (0.1 ml), the specimen is then placed on a scale and is allowed to dry for 40 minutes. The rate of drying is continuously monitored and recorded by the Drying Tester software. The results is reported by mg of water per minute times the area of specimen (mg/min*inch ² ).

AATCC 197 Vertical wicking of textiles

The rate (distance per unit of time) liquid travels along and/or through a vertical fabric specimen is visually observed, manually timed and recorded at specified intervals. This test method considers the influence of gravity when assessing wicking.

Hvgroscopicitv

About 2 grams of sample is placed in a weighing bottle and dried for 2 hr at 105 ° C (weight W3). The weighing bottle is then placed into a climatic chamber for 24 hr at 20 ° C and 65% RH. The weight of the samples is measured again (weight Wl). The weighting bottle is then placed into a climatic chamber for 24 hr at 30 ° C and 90% RH. The weight of the sample is measured again (weight W2). The hygroscopicty delta is measured by the following equation: MRl = (Wl - W3) / W3, MR2 = (W2 - W3) / W3. The Moisture absorption rate difference is obtained by Λ MR (%) = MR2 - MRl.

Hand Evaluation

The assessment of tactile properties was subjectively evaluated using the "HESC Standard of Hand Evaluation - Second Edition", which is a method developed by the "Hand Evaluation and Standardization Committee" from "The Textile Machinery Society of Japan". The specimens are assessed by comparing the sensations felt by the fingers during handling the sample with standard reference samples of the methodology. These properties include stiffness, smoothness, fullness, softness, crispness, compression and etc. A THV (Total Hand Value) grade from 1 to 5 is given, being 5 very good and 1 very poor.

EXAMPLE A TO I - STUDY OF THE MULTILOBAL CROSS SECTIONS

Different multilobal cross sections were investigated according to the melt-spinning process ability. Polyamide 6.6 pellet was used for the samples. The polyamide 6.6 pellet was produced from the polymerization of a nylon salt containing mainly hexamethylenediamine and adipic acid. The IVN (viscosity index) is from 128 to 132, and ATG (amine terminal groups) from 40 to 45, measured according to the methodology disclosed herein. Multifilament yarns were produced. A summary of the samples is showed at Table 2. EXAMPLES 1 TO 8 - FLAT YARN SAMPLES

PA 5.6 - examples 1. 2, 3 and 6

A polyamide 5.6 fiber was produced by melt-spinning extrusion from polyamide 5.6 pellets, using a spinneret containing multilobal cross section for examples 2 and 3, or a spinneret containing round orifices for examples 1 and 6. The polyamide 5.6 pellet is a commercially available polyamide from Cathay Biotech under the trademark Terryl ^® . The IVN is from 138 to 142, ATG from 38 to 42, and CTG from 65 to 75 measured according to the methodology disclosed herein.

In step al, the polyamide composition was fed into the inlet of the screw extruder in the form of dried pellets. In step a2, the polyamide was melted, homogenized and pressurized inside the screw extruder at a temperature of around 2902C and at an extrusion pressure of around 50 bars. Then, according to step a3, the molten polyamide blend was spun into multi-filament yarn at a spinning pack pressure of around 200 bars and at a spinning pack flow rate of around 5 kg/h. At Step a4, the polyamide fiber blend was solidified and wound into bobbins at around 4200 m/min.

PA 6,6 - examples 4, 5 and 7 A polyamide 6.6 fiber was produced by melt-spinning extrusion from polyamide 6.6 pellets and with the same process as described in example 1, 2, 3 and 6 above, using a spinneret containing multilobal cross section orifices for example 5, or a spinneret containing round orifices for examples 4 and 7. The polyamide 6.6 pellet was produced from the polymerization of a nylon salt containing mainly hexamethylenediamine and adipic acid. The IVN (viscosity index) is from 128 to 132, and ATG (amine terminal groups) from 40 to 45, measured according to the methodology disclosed herein.

PA 6.10 - example 8

A polyamide 6.10 fiber was produced by melt-spinning extrusion from polyamide 6.10 pellets and with the same process as described in example 1, 2, 3, and 6 above, using a spinneret containing round orifices. The polyamide 6.10 pellet is a commercially available polyamide from Solvay Group under the trademark STABAMID ^® . The IVN is from 102 to 118, ATG from 49 to 57 measured according to the methodology disclosed herein.

EXAMPLES 1.1 TO 4.2 - TEXTURED YARN SAMPLES

The multi-filament yarns (samples 1, 2, 4, 5, 6 and 7), obtained above, are further texturized into linear density of Ix80f68 dtex (examples 1.1, 2.1, 4.1, 5.1, 6.1 and 7.1). The multi-filament yarns (samples 1 and 4), obtained above, are further texturized into linear density of 2x80f68 dtex (examples 1.2 and 4.2).

In all of the examples above, a similar knitted fabric is produced in order to accomplish the moisture management tests. A summary of the sample details and mechanical results are given in the table below.

TABLE 1- List of samples

SAMPLE Polymer Titre Cross Yarn Elongation Tenacity

(dtex) Section Type [%] [cN/Tex]

Control 1 PA 5.6 100f68 O FLAT 72.40 28.90

Invention 2 PA 5.6 100f64 7 lobes FLAT 74.40 28.50

Invention 3 PA 5.6 100f88 5 lobes FLAT 66.20 30.50

Control 4 PA 6.6 100f68 O FLAT 76.10 33.70

Control 5 PA 6.6 100f64 7 lobes FLAT 76.50 33.20

Comparative 6 PA 5.6 100f23 O FLAT 81.40 32.90

Comparative 7 PA 6.6 100f23 O FLAT 91.50 31.70

Comparative 8 PA 6.10 100f68 O FLAT 76.10 33.70

Control 1.1 PA 5.6 Ix80f68 O TXT 20.77 28.23

Invention 2.1 PA 5.6 Ix80f64 7 lobes TXT 20.57 26.95

Control 4.1 PA 6.6 Ix80f68 O TXT 20.14 28.61

Control 5.1 PA 6.6 Ix80f64 7 lobes TXT 20.02 27.32

Comparative 6.1 PA 5.6 Ix78f23 O TXT 27.23 34.59

Comparative 7.1 PA 6.6 Ix78f23 O TXT 32.04 29.55

Comparative 1.2 PA 5.6 2x80f68 O TXT 28.60 30.00

Comparative 4.2 PA 6.6 2x80f68 O TXT 28.80 31.50 RESULTS

1- Study of the processability of multilobal cross-section

TABLE 2- Processability results of multilobal cross sections

Sample Coalescent Lobe Angle Spinning

center number between lobes Processabili

A 2 5 120° Good

B 3 7 120° Good

C 4 9 120° Good

D 4 9 120° Good

E 4 9 120° Regular

F 6 13 120° Good

G 4 5 90°/270° Poor

H 6 7 907270° Poor

Study of the hygroscopicity of polvamides

TABLE 3- Hygroscopicity

Hygroscopicity

[delta%]

PA 5.6 5.1

PA 6.6 3.1

PA 6.10 1.2

3- Study of the moisture management of FLAT yarn samples

TABLE 4- Moisture management resujts of FLAT samples

FLAT YARN Titre Cross Water Drying Water absorption Water wicking

Sample Section [mg/min*inch ² ] time [s] speed [mm/s]

1 PA 5.6 100f68 O 348 4.5 6.6

2 PA 5.6 100f64 7 lobes 373 2.7 8.2

3 PA 5.6 100f88 5 lobes - 3.1 8.2

4 PA 6.6 100f68 O 208 23.8 0.3

5 PA 6.6 100f64 7 lobes 215 11.5 0.6

6 PA 5.6 100f23 O 303 2.3 7.9

7 PA 6.6 100f23 O 229 59.4 0.1

8 PA 6.10 100f68 O 168 102 0.03

Study of the moisture management of TEXTURED yam samples

TABLE 5- Moisture management results of TEXTURED samples

TEXTURED YARN Titre Cross Water Drying Water absorption Water wicking

Sample Section [mg/min*inch ² ) time [s] speed [mm/s]

1.1 PA 5.6 Ix80f68 O 223 2.8 5.6

2.1 PA 5.6 Ix80f64 7 lobes 242 2.5 6.0

4.1 PA 6.6 Ix80f68 O 211 3.2 4.1

5.1 PA 6.6 Ix80f64 7 lobes 216 3.0 4.9

6.1 PA 5.6 Ix78f23 O 257 2.7 6.4 PA 6.6 Ix78f23 0 213 3.9 3.8

PA 5.6 2x80f68 0 151 2.7 5.1

PA 6.6 2x80f68 O 136 3.2 4.0

5- Vertical wickine of textiles

TABLE 6- wicking distance

Sample Height (cm)

Control 1 PA 5.6 O 14

Invention 2 PA 5.6 7 lobes 18

6- Study of the impact of the cross section on handling properties.

TABLE 7- Hand evaluation

Cross section Total Hand Value

! grade

Circular ≤4.6

Multilobal - 7 lobes 5.0

Conclusion

Firstly, several cross sections were investigated in order to choose the most appropriate considering processability (Table 2). Multilobal arrangements of 120° angle between lobes showed the best melt-spinning performance (samples A,B,C,D,F). Whereas flat cross section or less symmetric cross sections showed poor processability (samples E,G,H). Therefore, samples "A" and "B" were used for the comfort management experiments of the present invention.

Secondly, the hygroscopicity of three polyamides was analyzed and polyamide 5.6 showed the best result. In fact, the hygroscopicity was found to be surprisingly high (5.1% on Table 3, sample 1.2).

Then, the moisture management properties named water absorption, water drying and water wicking were investigated in FLAT YARNS and the results are summarized on Table 3. When comparing sample 2 (invention) to sample 4 (comparative), it is possible to observe that the water drying rate increased 79%, the water absorption improved 89% and the water wicking speed increased 26 times (or 2600%). Yarns of fewer and coarser filaments such as 100f23 (higher dtex per filament) tend to be less pleasant to the skin than yarns with more and thinner filaments (100f68). However, the results of samples 6 and 7 (100f23), showed very good moisture management due to the hygroscopic characteristic of polyamide 5.6, e.g. 96% higher in water absorption and 78 times higher in water wicking speed and are expected to be even higher with the addition of multilobal cross section. Therefore, the wicking properties improved drastically.

The modified multilobal cross section played a significant role in this improvement, by comparing sample 1 (control) and sample 2 (invention), it was found that the water drying rate increased 9%, the water absorption 40% and the water wicking speed 24%. The result of polyamide 6.10 (sample 8) was also given as comparison; very poor results were obtained due to the very low hydrophilicity. With regards to TEXTURED YARNS (Table 5), the same properties were analyzed. Textured yarns possess more crimp, texture, volume, elongation and twist; hence they provide more softness, comfort, thermal insulation and are more pleasant to the skin. The results of samples 2.1 (invention) and 4.1 (comparison) indicated an improvement of 15% in water drying rate, 22% in water absorption, 46% in water wicking speed. The multilobal cross section also contributed to this increase by comparing sample 1.1 and 2.1, with increases of 9% in water drying rate, 11% in water absorption and 7% in wicking speed. The results of yarns with fewer filaments (6.1) and 2x plies (1.2) showed significant improvement in relation to samples 7.1 and 4.2 respectively. The term 2x80f68 means that two yarns were joined during the texturizing process; hence the resulting linear density is twice the linear density of Ix80f68. In addition, the vertical wicking test was also performed to further analyze the wicking property, taking into consideration the gravity, in order to understand the influence of the multilobal cross section, and again a substantial improvement was observed by comparing the results of Table 6 (sample 1 and 2), where a surprisingly increase of 29% was obtained.

From the results of table 7, it is also possible to conclude that the cross section profile of the present invention improves handling sensation and softness of the fiber because of the lower flexural rigidity, preferred bending direction and lower yarn package density.

Therefore, according to the results it is possible to confirm that a novel polyamide with intrinsic hygroscopic and comfort properties is disclosed in the present invention, where the polyamide articles exhibit higher rate of water absorption, wicking and drying, when compared to non-hygroscopic polyamides with round cross sections. Moreover, the synergy between hygroscopicity and cross section having high surface area and capillarity speeds up the water drying rate so that the wearer feel dry and comfortable even after intense sweating. The results are summarized below:

Water drying speed

PA 5.6 7 lobes »> PA 6.6 O FLAT

PA 5.6 7 lobes » PA 6.6 O TXT

Water absorption time

PA 5.6 7 lobes »> PA 6.6 O FLAT

PA 5.6 7 lobes » PA 6.6 O TXT

Water wicking speed

PA 5.6 7 lobes »»> PA 6.6 O FLAT

PA 5.6 7 lobes »> PA 6.6 O TXT

The overall advantages of the polyamide fiber and articles produced therefrom include:

Optimal hygroscopicity, for absorbing sweat without feeling wet, and maintaining the ideal microclimate insulation.

Enhanced wicking speed, for efficiently transporting the sweat away from the skin.

- Fast drying rate, for maintaining the skin dry and avoiding uncomfortable post-exercise chilling sensation. The mechanical and chemical properties of the polyamide article are not significantly changed.

The current method is simple and makes use of conventional and well-kwon extrusion machinery. The cross section profile of the present invention also improves the handle and softness of the fiber because of the characteristics of the novel multilobal cross sections disclosed.