US20180245252A1

US20180245252A1 - Method for producing a structured microfilament nonwoven

Info

Publication number: US20180245252A1
Application number: US15/747,444
Authority: US
Inventors: Robert Groten; Benedicte Beck; Ulrich Jahn; Abdelkader Ameur; Jean-Francois Kerhault
Original assignee: Carl Freudenberg KG
Current assignee: Carl Freudenberg KG
Priority date: 2015-08-10
Filing date: 2016-07-15
Publication date: 2018-08-30
Also published as: DE102015010129A1; WO2017025271A1; TW201706473A; TWI633219B; EP3334857A1; CN107849765A

Abstract

In an embodiment, the present invention provides a method for producing a structured microfilament non-woven, including: forming a non-woven by spinning microfilaments and/or composite filaments that can be split into microfilaments to form at least one fiber layer, stretching the at least one fiber layer, and laying the at least one fiber layer; thermally pre-bonding the non-woven; treating the thermally pre-bonded non-woven using a pressurized medium in order to break the thermal pre-bonding at least in part; and further applying a pressurized medium to the non-woven while the non-woven is resting on a structure-producing surface, so as to obtain a structured microfilament non-woven.

Description

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/EP2016/066857, filed on Jul. 15, 2016, and claims benefit to German Patent Application No. DE 10 2015 010 129.3, filed on Aug. 10, 2015. The International Application was published in German on Feb. 16, 2017 as WO 2017/025271 under PCT Article 21(2).

FIELD

The present invention relates to the field of textiles and the uses thereof.
The invention relates in particular to a method for producing a structured microfilament non-woven, to microfilament non-wovens produced using this method, and to the use of said non-wovens.

BACKGROUND

Non-wovens are textiles fabrics made of individual fibers and can be obtained using a wide range of production methods such as carding (dry laid), melt spinning (spunbonding), melt blowing or aerodynamic fabric laying (air laid).
During melt spinning, a polymer substance is heated in an extruder and pressed through a spinneret by means of viscose pumps. The polymer emerges from the die base as threads (continuous filament) in molten form, is cooled by an airflow, and drawn out of the melt. The airflow conveys the continuous filaments on a belt conveyor that is formed as a screen. The threads can be fixed, forming a fiberwoven fabric, by means of suction under the screen belt. The fiberwoven fabric can be bonded by means of heated rolls (calendaring), by means of a vapor stream, or by (hydro-)mechanical or chemical bonding.
The textile physical properties of non-wovens can be controlled by means of the chemical and textile physical properties of the fibers or filaments that form said non-wovens. In this case, the fiber or filament raw materials are selected according to the desired chemical or physical properties, for example with respect to the colorability thereof, the chemical resistance thereof, the thermoformability thereof or the adsorption power thereof. The modulus and stress-strain properties of the fibers or filaments are dependent on the material properties, which can be controlled by selecting the degree of crystallinity and/or orientation and the cross-sectional geometry in order to influence the flexural strength, the force absorption or the specific surface areas of the individual fibers or filaments.
In order to improve the look, the feel and/or the use, it is further known to provide non-wovens with structuring.
It is known to produce structured non-wovens from staple fibers. On account of their short length, these fibers have a high degree of fiber movability and thus form clear structuring. However, a disadvantage of using staple fibers is that the high movability leads to disintegration of the structure during the mechanics of a washing process. This is counteracted in the art by using adhesive binders, although this is disadvantageous with regard to the textile properties of the fabrics obtained.
DE 102008033253 A1 describes a method and a device for producing structured non-wovens, in which a pressurized medium is applied to the non-woven while said non-woven is resting on a structure-producing surface. The non-woven to be structured is guided over the periphery of a drum while the pressurized medium is applied, the surface of the drum having a surface structuring that produces a herringbone pattern.
A disadvantage of this method is that the structuring pattern of the non-woven is not very resistant, and is negatively affected in particular during treatments causing mechanical stress, such as repeated washing or dyeing processes.
DE 102008061679 A1 discloses a method for pre-bonding a fleece of fibers and/or filaments, the fleece being transported on a backing, using an apparatus for water jet needling, and the apparatus for water jet needling being positioned so as to be at a great distance from the backing that supports the fleece.
The structuring pattern is not very resistant to treatments causing mechanical stress in the non-wovens described in this document either.
The object of the present invention is that of providing structured non-wovens, the structuring pattern of which is resistant even to treatments causing mechanical stress, such as repeated washing or dyeing processes. At the same time, the non-wovens should have good mechanical properties, in particular good permanent wash resistance together with satisfactory performance properties, good thermophysiological comfort, and a pleasant skin feel and look.

SUMMARY

In an embodiment, the present invention provides a method for producing a structured microfilament non-woven, comprising: forming a non-woven by spinning microfilaments and/or composite filaments that can be split into microfilaments to form at least one fiber layer, stretching the at least one fiber layer, and laying the at least one fiber layer; thermally pre-bonding the non-woven; treating the thermally pre-bonded non-woven using a pressurized medium in order to break the thermal pre-bonding at least in part; and further applying a pressurized medium to the non-woven while the non-woven is resting on a structure-producing surface, so as to obtain a structured microfilament non-woven.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. Other features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:

FIG. 1 shows a perforated microfilament non-woven produced using the method according to the invention.

DETAILED DESCRIPTION

It has been found that microfilament non-wovens having a clearly defined structuring pattern can be produced by means of the method according to the invention, which non-wovens are resistant even to treatments causing mechanical stress, such as repeated washing, in particular industrial hot washing cycles or dyeing processes which cause high stress. At the same time, the non-wovens have excellent mechanical properties, in particular good permanent wash resistance together with satisfactory use properties, good thermophysiological comfort, and a pleasant skin feel and look.
The thermal pre-bonding is an important method step of the method according to the invention. By means of said pre-bonding, the fibers of the non-woven can be transitionally stabilized to such an extent that transfer to a facility for applying a pressurized medium is possible without difficulty. At the same time, the bonding in the non-woven is weak enough to be able to be broken again in a simple manner, by means of the pressurized medium being applied, and is thus reversible at least in part. As a result, the limitation of the fiber movability can be prevented at the time of the structuring. This is advantageous because, in the case of irreversible pre-bonding such as needling, the associated reduction in the fiber movability impedes the structuring step and a clearly structured pattern therefore cannot be achieved. Furthermore, in the case of irreversible pre-bonding, the fibers are provided with a high retractive force which negatively affects the clarity and stability of the structuring pattern. For these reasons, in a preferred embodiment of the invention, the non-woven is not needled for pre-bonding, and more preferably is only thermally pre-bonded.
In contrast, microfilament non-wovens having a clearly defined structuring pattern can be obtained by means of the method according to the invention, which non-wovens in addition surprisingly exhibit a high degree of stability to treatments causing mechanical stress, such as repeated washing or dyeing processes.
It is likely that the advantageous properties of the structured non-wovens produced using the method according to the invention are due at least in part to the reversible thermal pre-bonding of the non-woven. A further positive effect of the thermal pre-bonding is that it allows for transportation, winding up and unwinding, and thus for offline processing. Moreover, the reversible thermal pre-bonding is also advantageous in the case of inline processing, since said pre-bonding makes it possible to hold the fibers stably in a desired structure in the method steps between bonding and structuring.
The thermal pre-bonding can be carried out in the conventional ways that are known to a person skilled in the art, for example using a heated calendar. If a non-woven containing composite filaments is used as the starting material, using a calendar is advantageous in that slight splicing of the filaments can already be achieved, which facilitates the later splitting step and makes a higher yield possible.
Using a hot-air blade, a rapid package drier, for example a hot air tunnel oven, or a drum through which hot air passes, known as a “flow drier”, has also been found to be suitable. An advantage of these methods is that no undesirable compression of the non-woven occurs during the pre-bonding, and pre-bonding within the meaning of pre-felting or through-marling, which can be figuratively seen as “incorrect knots”, can be prevented, which is generally favorable for the subsequent structuring process.
The strength at which the non-woven is thermally pre-bonded can be adjusted by a person skilled in the art on the basis of the materials used, the mass per unit area and the desired degree of bonding. At higher masses per unit area, of over 130 g/m²for example, it may be advantageous to carry out the pre-bonding using passage heating in order to ensure continuous heating of the non-woven, for example in the calendar.
Following the thermal pre-bonding of the non-woven, said non-woven is treated using a pressurized medium. For this purpose, the non-woven can be transferred without difficulty to a facility for applying a pressurized medium. This is possible because the non-woven, as explained above, can be provided with sufficient stability by means of the thermal pre-bonding.
This treatment is used to break the thermal pre-bonding at least in part. As a result, a restriction of the fiber movability can be prevented at the time of the structuring. As explained above, this is advantageous because the non-woven can, as a result, be provided with a clearly structured pattern in the subsequent structuring step.
In this case, the extent to which said pre-bonding is broken can be controlled in a manner known to a person skilled in the art, for example by adjusting the pressure and the treatment duration. It has in principle been found to be favorable for the non-woven to be treated such that the thermal pre-bonding is completely or almost completely broken upon structuring. Specifically, practical tests have shown that the pattern is clearer the more completely the pre-bonding is broken. Nonetheless, it may be expedient to break the pre-bonding only in part, for example in order to obtain a more strongly bonded non-woven.
A very wide range of media can be used as the pressurized medium. Using water is particularly simple and cost-effective. Conventional apparatuses for water jet bonding can be used to apply water.
The adjustment of the application pressure can be varied depending on the materials used and the desired extent to which the thermal pre-bonding is to be broken. Pressures in the range of 200-300 bar have generally been found to be favorable.
The application of the pressurized medium makes it possible to additionally carry out various further processes such as compacting, fiber separation, splitting and/or intertwining of the fibers, depending on the selected starting material and the method conditions set. Expediently, the non-woven is guided over the periphery of a drum, in particular a colander roll, while the pressurized medium is applied. In the process, the non-woven can rest on a structure-producing surface or on a surface that is not structure-producing.
In order to structure the non-woven, according to the invention a pressurized medium is further applied to said non-woven while it is resting on a structure-producing surface, as a result of which a structured microfilament non-woven is obtained. In this case, the structuring pattern can be two-dimensional. It is particularly effective, however, for the pattern to be three-dimensional.
Advantageously, both treatments according to the invention using a pressurized medium can be carried out in the same apparatus, for example in a conventional apparatus for water jet needling. The support surface of a support element can be used as the structure-producing surface and can comprise elevations for this purpose. In this case, the elevations are formed so as to replicate the negative of the desired pattern.
Advantageously, the support surface additionally comprises perforations as drainage openings. Applying a pressurized medium to the non-woven makes it possible for at least some of the fibers of the non-woven, which fibers are positioned on the elevations when the liquid is applied, to be washed downwards off the elevations by the liquid, as a result of which the desired pattern is produced in the non-woven.
In a preferred embodiment of the invention, the support element is formed as a preferably perforated drum. In this embodiment, the non-woven to be structured is expediently guided over a structured belt and in particular over the periphery of the drum while the pressurized medium is applied. This makes it possible to carry out the method in a particularly simple and efficient manner.
In addition to the structuring of the non-woven, other processes such as further breaking of the thermal pre-bonding, fiber separation, compacting, felting and/or intertwining of the fibers can also be carried out. If the non-woven contains composite filaments, the splitting thereof is expediently carried out within the context of this method step.
The method according to the invention makes it possible to produce non-wovens having a very wide range of patterns by means of varying the shape of the elevations on the support surface. The elevations can thus be punctiform, circular, streak-like, linear, wave-like or rhombic for example. It is also conceivable to form the pattern in a representational manner, whereby the non-woven can be provided with images that are comparable to the watermarks known in paper. If perforations are to be formed in the non-woven, the support surface can thus comprise elevations having a polygonal, circular, semi-circular or oval cross section.
The type of structuring pattern made can be selected on the basis of the desired optics. The non-woven can thus be provided with a wave pattern, herringbone pattern, nub pattern or textile patterns such as linen, twill, satin, two-ply fabric and/or jacquard patterns for example. It is also conceivable to provide the non-woven with perforations.
A very wide range of media, and preferably water, can be used as the pressurized medium in this method step too.
The adjustment of the application pressure can be varied depending on the materials used and the desired structuring results. Pressures in the range of 200-300 bar have generally been found to be favorable.
As mentioned above, the support surface preferably comprises perforations as drainage openings in order to remove the medium used as the application medium. Alternatively and/or in addition the medium can, however, also be removed in a separate method step.
When a pressurized medium is applied, whether within the context of breaking the thermal pre-bonding or within the context of structuring, the microfilaments can be intertwined with one another and bonded, as is known to a person skilled in the art.
Microfilaments are characterized by a very low average titer of less than 1 dtex. Using microfilaments is advantageous in that, on account of the low flexural strength of the filaments, particularly clearly defined structuring patterns can be achieved, and the further processing of the structured non-woven is particularly simple.
In a preferred embodiment of the invention, the microfilaments have a titer of between 0.1 dtex and 0.5 dtex, and in particular of from 0.15 to 0.3 dtex. It has been found, in these titer ranges, that good stability of the structuring (slip resistance of the filaments) can be achieved and the structuring does not tend to collapse. Using even finer titers, for example of from 0.05 dtex to 0.3 dtex, can result in even better stability of the structuring, but the tendency of the dimensional structures to collapse also increases on account of the increasingly reduced flexural strength of the microfilaments.
According to the invention, the term “filaments” is intended to mean fibers that, in contrast to staple fibers, have a theoretically limitless length. An advantage of using filaments compared with using staple fibers is the mechanical strength of the non-woven produced therefrom: As the length of the fibers increases, the number of friction (or binding) points to other fibers increases. Short fibers thus have fewer friction points, when the textile is stressed the fibers can be easily displaced and are easily pulled out of the textile.
As the fiber length increases, the slip resistance and the force required for pulling the fibers out of the composite also increase together with the number of friction (or binding) points. In the case of a very long fiber length it is no longer possible to pull out said fibers at all, and therefore the textile can be destroyed only by tearing the fibers.
The materials of which the microfilaments and/or composite filaments consist can be selected depending on the desired properties of the structured non-woven produced therefrom. It is important to the method according to the invention that the filaments should be able to be thermally bonded, at least in part. This is advantageous because it is thus possible to dispense with pre-braiding and/or needling or chemical bonding of the fibers.
Microfilaments and/or composite filaments that contain thermoplastic polymers such as polyolefins, in particular polyethylene, and/or consist of thermoplastic polymers, in particular the above-mentioned thermoplastic polymers, have been found to be suitable for a very wide range of applications.
In order to be able to reliably carry out the thermal pre-bonding industrially, it is advantageous for the microfilaments and/or composite filaments to comprise at least two different polymers, the melting points of which differ by at least 10° C., for example from 10° C. to 30° C., more preferably by at least 15° C., for example from 15° C. to 25° C., and in particular by at least 20° C., for example from 20° C. to 25° C., such as PET (256° C.) and PA6 (225° C.). In this case, it is advantageous for the method described above for the polymers used to be incompatible, non-miscible and thus also not able to adhere to one another.
In order to achieve a sufficient level of thermal pre-bonding, it is further advantageous for the proportion of thermoplastic polymers in the non-woven to be at least 20 wt. %, preferably from 25 wt. % to 100 wt. %, more preferably from 40 wt. % to 100 wt. %, more preferably from 50 wt. % to 100 wt. %, more preferably from 60 wt. % to 100 wt. %, more preferably from 70 wt. % to 100 wt. %, more preferably from 80 wt. % to 100 wt. % and in particular from 90 wt. % to 100 wt. %.
In order to achieve sufficient influence of the microfilaments, it is advantageous to use microfilaments and/or composite filaments in such a type and amount, and optionally to adjust the degree of splitting such that the proportion of microfilaments is at least 70 wt. %, preferably from 70 wt. % to 100 wt. %, and in particular approximately 100 wt. % based on the total weight of the non-woven.
It is in principle conceivable for the non-woven to also comprise further fibers that are not microfilaments. In this case it is advantageous, however, not to set the proportion of further fibers too high, since the ability of the fibers to cling to the structure-producing surface reduces as the fiber titer increases. Against this background, the proportion of further fibers having a titer of more than 1 dtex, if present, and according to the invention preferably at most 25 wt. %, more preferably at most 10 wt. %, and in particular no further fibers are present.
According to the invention, the non-woven is preferably produced from composite filaments that can be split into microfilaments. In particular, the proportion of composite filaments in the non-woven is preferably more than 70 wt. %, more preferably more than 80 wt. %, more preferably more than 90 wt. %, and more preferably more than 95 wt. %. Composite filaments consist of at least two elementary filaments and can be split into microfilaments and bonded by means of a pressurized medium being applied, for example by means of water jet needling, as is known to a person skilled in the art.
In this case, the microfilaments obtained by splitting have a titer of less than 1 dtex, preferably of between 0.1 dtex and 0.5 dtex, and in particular of from 0.15 to 0.3 dtex. It has been found, in these titer ranges, that good stability of the structuring (slip resistance of the filaments) can be achieved and the structuring does not tend to collapse. As described above, it is also possible to use even finer titers, for example of from 0.05 dtex to 0.3 dtex.
Using composite filaments as the starting material for producing the microfilaments is advantageous in that the titer of the microfilaments produced therefrom can be adjusted in a simple manner, by varying the number of microfilaments contained in the composite filaments. In this case, the titer of the composite filaments can remain constant, and this is advantageous in terms of the process.
Another advantage of using the composite filaments is that the production of the non-woven can be carried out without using solvents, chemical binders and using a minimum of process steps. Since it is also possible to dispense with the use of solvents during the structuring, it is thus possible to advantageously carry out the method according to the invention in a very environmentally friendly and cost-effective manner. It is thus possible to comply with the requirements of OEKO-TEX Standard 100, product class 1 using the non-wovens according to the invention.
Another advantage of using the composite filaments is that said filaments can be easily split and bonded within the context of breaking the thermal pre-bonding and/or within the context of structuring, by means of the pressurized medium being applied. In this case, the proportion of composite filaments in the non-woven is advantageously more than 70 wt. %, more preferably more than 80 wt. %, more preferably more than 90 wt. %, and more preferably more than 95 wt. %.
In an embodiment of the invention, after thermal pre-bonding, the non-woven is wound up, optionally stored temporarily, and made available for further processing (offline processing). It is also conceivable, however, to carry out the treatment using the pressurized medium immediately after the thermal pre-bonding (online processing).
The microfilaments and the composite filaments used as the starting material for producing the microfilaments can be produced in a manner known to a person skilled in the art. Suitable methods are in particular melt spinning (spunbonding).
In order to produce the microfilaments and/or the composite filaments, polymer substances can be heated under pressure, for example in extruders, and pressed through two-component or multi-component dies, resulting in continuous filaments. After emerging from the extrusion die, the continuous filaments can be stretched and positioned on a belt conveyor so as to be deflected in the transverse direction, and so as to form a fiber layer, by means of a dynamic laying process. Positioning the continuous filaments so as to be deflected in the transverse direction is advantageous in that the isotropy of the mechanical properties of the non-woven is increased thereby.
The composite filaments can have a very wide range of cross sections that are known for producing split fibers, for example a cross section having a multi-segment structure in the manner of an orange or also referred to as a “pie” structure, it being possible for the segments to contain different, alternately incompatible, polymers.
In this case, the pie arrangement of the fibers can for example comprise 2, 4, 8, 16, 24, 32 segments or 64 segments, such that the composite filaments correspondingly consist of 2, 4, 8, 16, 24, 32 or 64 microfilaments. Hollow pie structures that can also comprise a cavity that extends axially in an asymmetrical manner are also suitable. Pie structures, in particular hollow pie structures, can be split particularly easily.
In this case, the microfilaments can be n-cornered or multilobal in cross section.
In a preferred embodiment of the invention, the composite filaments comprise different filaments that contain at least two preferably incompatible thermoplastic polymers. As a result, particularly simple splitting can be achieved and a multi-component non-woven can be obtained at the same time.
Incompatible polymers are to be understood as those polymers which, when combined, result in pairings that do not adhere or adhere only in a limited manner and/or with difficulty. A composite filament of this kind is easy to split into microfilaments and produces a favorable ratio of strength to mass per unit area. Another advantage of using incompatible polymers is that the adhesion achieved during the thermal pre-bonding can be more easily broken during the subsequent treatment using a pressurized medium and leads to improved structurability of the non-woven on account of the increased fiber movability thus achieved.
It is also advantageous in the embodiment according to the invention in which the non-woven already contains microfilaments for the microfilaments to comprise at least two types of microfilaments that consist of different incompatible polymers.
The composite filaments preferably contain at least one incompatible polymer pair. Preferably polyolefins, polyesters, polyamides and/or polyurethanes are used as incompatible polymer pairs in a combination such that pairings are produced that do not adhere, adhere only in a limited manner and/or adhere only with difficulty. Pairings that adhere only in a limited manner and/or with difficulty are present when the composite filaments comprising said pairings are split more easily than is the case for a composite filament that consists of just one of the polymers used.
The polymer pairs used are particularly preferably selected from polymer pairs comprising at least one polyolefin and/or at least one polyamide, preferably with polyethylene, such as polypropylene/polyethylene, polyamide 6/polyethylene or polyethylene terephthalate/polyethylene, or with polypropylene, such as polypropylene/polyethylene, polyamide 6/polypropylene or polyethylene terephthalate/polypropylene.
Polymer pairs comprising at least one polyester and/or at least one polyamide are most particularly preferred.
Polymer pairs comprising at least one polyamide or comprising at least one polyethylene terephthalate are preferred on account of the limited adhesive properties thereof, and polymer pairs comprising at least one polyolefin are particularly preferably used on account of said pairs adhering only with difficulty.
Polyesters, preferably polyethylene terephthalate, polylactic acid and/or polybutylene terephthalate, on the one hand, and polyamide, preferably polyamide 6, polyamide 66, polyamide 46, on the other hand, optionally in combination with one or more further polymers that are incompatible with the above-mentioned components, preferably selected from polyolefins, have been found to be particularly expedient as particularly preferred components. This combination has an excellent splitting ability. The combination of polyethylene terephthalate and polyamide 6, or of polyethylene terephthalate and polyamide 66, is most particularly preferred.
The polymers used to produce the microfilaments and/or composite filaments can contain from 150 ppm to 10 wt. % of at least one additive selected from the group consisting of color pigments, antistatic agents, antimicrobial agents, such as copper, silver gold, or hydrophilizing additives or water-repellent additives. Using the mentioned additives in the polymers used makes it possible to adapt to client-specific requirements.
It is conceivable to provide the surface with an antistatic finish and to provide said surface with care products. It is also conceivable to retrospectively provide the non-woven with hydrophilic, water-repellent or antistatic spin finishes and to provide said non-woven with care products. It is also conceivable to already introduce additives for surface modification into an extruder during production of the continuous filament. Even in the event of bulk coloring, retrospective coloring is not required since pigments can already be introduced into an extruder during production of the continuous filament.
Moreover, the non-woven can undergo chemical bonding or finishing, for example anti-pilling treatment, hydrophilizing, antistatic treatment, treatment for improving the fire-resistance and/or for changing the tactile properties or the shine, mechanical treatment or treatment in a tumble drier and/or treatment for changing the appearance, such as coloring or printing.
The invention further relates to a structured non-woven that can be produced by means of the method according to the invention. As explained above, the non-woven is characterized in particular in that the structuring pattern thereof is very clearly outlined and is in addition also resistant to treatments causing mechanical stress such as repeated washing or dyeing processes. It has thus been possible to determine that example non-wovens according to the invention still have structuring patterns that can be easily identified visually and/or haptically even after 30 domestic washing cycles at 90° C. in accordance with DIN EN ISO 6330.
Moreover, on account of the microfilaments, the non-woven has good mechanical properties, even at low masses per unit area, the structuring withstands a mechanically demanding coloring process (jet dyeing), good permanent wash resistance together with satisfactory performance properties, good thermophysiological comfort, high fineness, density, excellent cleaning performance, great lightness, sound-absorbing properties, and a pleasant skin feel and look.
Compared with non-wovens in which no pre-bonding is carried out, the non-woven according to the invention is characterized in that the structurings are very clearly embossed. Thus, in the case of perforations as the structuring pattern for example, it can be seen that said perforations are substantially free of fibers that cover and/or bridge the holes. Surprisingly, this effect can also be observed when the thermal pre-bonding has been completely broken prior to embossing. In a preferred embodiment of the invention, the non-woven according to the invention is present in a non-needled state and/or bonded using a binder.
Compared with structurings that are thermally produced retrospectively, the non-woven can furthermore be provided with a structuring pattern that is not hardened compared with the remainder of the non-woven. The fibers are also not destroyed by this structuring process, but instead the undamaged filaments are merely pushed to the edge of the hole structures and felted together there, in a manner comparable to reinforcement of buttonholes. As a result, said filaments can thus continue to fully contribute to the mechanical strength of the textile. The non-woven can comprise a very wide range of structurings, for example a wave pattern, herringbone pattern, nub pattern or textile patterns such as linen, twill, satin, two-ply fabric and/or jacquard patterns and/or perforations.
According to the invention, the non-woven preferably comprises composite filaments that are split at least in part into microfilaments having an average titer of less than 1 dtex, preferably of between 0.1 dtex and 0.5 dtex, and in particular of 0.15-0.3 dtex, and intertwined with one another. In this case, the proportion of split microfilaments is preferably at least 70 wt. %, preferably from 70 wt. % to 100 wt. %, and in particular approximately 100 wt. %, based on the total weight of the non-woven.
As explained above, the non-woven preferably comprises microfilaments and/or composite filaments that are split at least in part, which filaments contain thermoplastic polymers such as polyolefins, in particular polyethylene, and/or consist of thermoplastic polymers, in particular the above-mentioned thermoplastic polymers.
As described above, the microfilaments and/or the composite filaments that are split at least in part advantageously contain different, alternately incompatible polymers. The microfilaments and/or composite filaments preferably comprise at least two incompatible polymers, as described above.
It is also advantageous for the proportion of thermoplastic polymers in the non-woven to be at least 20 wt. %, preferably from 25 wt. % to 100 wt. %, more preferably from 40 wt. % to 100 wt. %, more preferably from 50 wt. % to 100 wt. %, more preferably from 60 wt. % to 100 wt. %, more preferably from 70 wt. % to 100 wt. %, more preferably from 80 wt. % to 100 wt. % and in particular from 90 wt. % to 100 wt. %.
In a preferred embodiment of the invention, the mass per unit area of the non-woven is less than 50 g/m², for example from 20 to 50 g/m², more preferably 20 to 40 g/m²and in particular from 25 to 35 g/m². According to the invention, the mass per unit area is measured in accordance with DIN EN 29073.
In this very lightweight category, the structuring pattern can have a particularly positive effect on the uniformity of the distribution of the microfilaments and can facilitate processing. This makes it possible to produce three-dimensional structured non-wovens that are significantly lighter weight than lightweight cloths having comparable performance properties from different production methods. On account of the fineness and density of the microfilaments, said non-wovens also, if desired, have excellent cleaning performance despite their low mass per unit area.
In a further preferred embodiment of the invention, the mass per unit area of the non-woven is more than 50 g/m², for example from 50 to 130 g/m², more preferably 70 to 120 g/m², more preferably from 80 to 110 g/m². In this medium weight category, non-wovens can be produced in which the three-dimensional structuring can recreate the feel and look of wovens. Thus, for example towels can be produced that are strong, light-weight and effective, as well as having the textile look known to users.
The present invention further relates to the use of the microfilament non-woven according to the invention as a cleaning cloth, towel, cloth for sanitation purposes, bed linen, upholstery fabric or lining material.
The invention is explained in greater detail below by means of an example.

EXAMPLE

Using 2 extruders, 70% PET and 30% PA6 are melted and combined in a spinneret for bicomponent filaments, extruded together in the form of continuous PIE16 filaments, and stretched at approximately 3500 m/min to a titer in the non-split state of approximately 2.4 dtex, and laid on a laying belt to form a fleece of 37 g/m². The fleece is stabilized by applying an, optionally also heated, airflow from above, through the fleece and through a laying belt, which is in turn suctioned from below. When there is free sagging of just a few centimeters, the fleece is guided into a colander that is operated at a line pressure of 33 daN/cm and a temperature of the two rolls of 150° C. The thermally pre-bonded non-woven is wound up, can thus be handled (wound up and unwound), and is fed to a water jet bonding facility at another location.
During the water jet bonding, which is implemented using four drums, the steps of breaking the pre-bonding, splitting the bicomponent filaments into polyamide and polyester segments, causing the filaments to cling to the suctioned water drum structures, and felting the filaments in the turbulent flows between the water jet and the backing (suction drum) overlap.
In the test arrangement, fine mesh structures, i.e. suction drums that are as smooth as possible, were found to be advantageous for the first three passes, while the fourth suction drum is the structure-producing drum. The first 3 passes are carried out moderately, pressure being applied alternately to the sides (ABA): the structure-producing screen drum undergoes at least two passes on the same side (BB) and high pressures are applied thereto. Subsequently, drying is carried out using a through-suction drier, and the non-woven is wound into a roll at low traction (winding pressure).
During this second step of the production process, depending on the structure, the width of the product shrinks by 7-15% and the mass per unit area also increases by 7-10%. In the specific case, this increase is from 37 g/m²following the thermal pre-bonding in step 1 to 40 g/m²after water jet bonding and drying.
The product can thus undergo dispersion dyeing in the jet and maintain its structuring.
FIG. 1 shows a perforated microfilament non-woven produced using the method according to the invention. It is clearly visible that the perforation made has a very clearly defined edge and only very few fibers pass therethrough.
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.
The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.

Claims

1. A method for producing a structured microfilament non-woven, comprising:

forming a non-woven by spinning microfilaments and/or composite filaments that can be split into microfilaments to form at least one fiber layer, stretching the at least one fiber layer, and laying the at least one fiber layer;

thermally pre-bonding the non-woven;

treating the thermally pre-bonded non-woven using a pressurized medium in order to break the thermal pre-bonding at least in part; and

further applying a pressurized medium to the non-woven while the non-woven is resting on a structure-producing surface, so as to obtain a structured microfilament non-woven.

2. The method according to claim 1, wherein the non-woven is not needled or adhesively bonded for the purpose of pre-bonding.

3. The method according to claim 1, wherein the thermal pre-bonding is carried out using a heated calendar.

4. The method according to claim 1, wherein the treatment using a pressurized medium for breaking the thermal pre-bonding, and the treatment using a pressurized medium for structuring the non-woven are carried out in the same apparatus.

5. The method according to claim 1, wherein the treatments using a pressurized medium for breaking the thermal pre-bonding and/or for structuring the non-woven split composite filaments into microfilaments at least in part and intertwine said filaments with one another.

6. A structured microfilament non-woven produced using the method according to claim 1.

7. The structured microfilament non-woven according to claim 6, wherein a structuring pattern of the structured microfilament non-woven can be identified visually and/or haptically after 30 domestic washing cycles at 90° C. in accordance with DIN EN ISO 6330.

8. A structured microfilament non-woven according to claim 6, wherein a mass per unit area of the non-woven is less than 50 g/m².

9. The structured microfilament non-woven according to claim 6, wherein the microfilaments contain thermoplastic polymers in a proportion of at least 20 wt. % based on the total weight of the non-woven.

10. The structured microfilament non-woven according to claim 6, wherein a proportion of microfilaments is at least 70 wt. % based on a total weight of the non-woven.

11. The structured microfilament non-woven according to claim 6, wherein a proportion of composite filaments in the microfilament non-woven that are split at least in part into microfilaments and intertwined is over 70 wt. %.

12. The structured microfilament non-woven according to claim 6, wherein a degree of splitting of the composite filaments is over 80%.

13. The structured microfilament non-woven according to claim 6, wherein the composite filaments and/or the microfilaments contain at least two incompatible thermoplastic polymers selected from polyester, preferably polyethylene terephthalate, polylactic acid and/or polybutylene terephthalate, on the one hand, and polyamide, preferably polyamide 6, polyamide 66 or polyamide 46, on the other hand.

14. The structured microfilament non-woven according to claim 6, wherein the composite filaments contain at least one polymer pair consisting of at least one polyester and at least one polyamide.

15. Use of the structured microfilament non-woven according to claim 6 as a cleaning cloth, towel, cloth for sanitation purposes, bed linen, upholstery fabric, or lining material.

16. The structured microfilament non-woven according to claim 10, wherein the proportion of microfilaments is from 70 wt. % to 100 wt. % based on the total weight of the non-woven.

17. The structured microfilament non-woven according to claim 16, wherein the proportion of microfilaments is approximately 100 wt. % based on the total weight of the non-woven.

18. The structured microfilament non-woven according to claim 12, wherein the degree of splitting of the composite filaments is over 95%.

19. The structured microfilament non-woven according to claim 13, wherein the at least one polyester comprises polyethylene terephthalate, polylactic acid, and/or polybutylene terephthalate.

20. The structured microfilament non-woven according to claim 13, wherein the at least one polyamide comprises polyamide 6, polyamide 66, or polyamide 46.