EP3385432A1

EP3385432A1 - Nonwoven cellulose fiber fabric with extremely low heavy metal content

Info

Publication number: EP3385432A1
Application number: EP17164619.3A
Authority: EP
Inventors: Tom Carlyle; Mirko Einzmann; Gisela Goldhalm; Malcolm John Hayhurst; Katharina Mayer; Ibrahim Sagerer Foric
Original assignee: Lenzing AG; Chemiefaser Lenzing AG
Current assignee: Lenzing AG
Priority date: 2017-04-03
Filing date: 2017-04-03
Publication date: 2018-10-10
Also published as: TWI826372B; WO2018184927A1; TW201900971A

Abstract

A nonwoven cellulose fiber fabric (102), in particular directly manufactured from lyocell spinning solution (104), wherein the fabric (102) comprises a network of substantially endless fibers (108), and wherein a heavy metal content of the fibers (108) is not more than 10 ppm for each individual chemical heavy metal element.

Description

Field of the invention

The invention relates to a nonwoven cellulose fiber fabric, a method of manufacturing a nonwoven cellulose fiber fabric, a device for manufacturing a nonwoven cellulose fiber fabric, a product or composite, and methods of use.

Background of the invention

Lyocell technology relates to the direct dissolution of cellulose wood pulp or other cellulose-based feedstock in a polar solvent (for example n-methyl morpholine n-oxide, which may also be denoted as "amine oxide" or "AO") to produce a viscous highly shear-thinning solution which can be transformed into a range of useful cellulose-based materials. Commercially, the technology is used to produce a family of cellulose staple fibers (commercially available from Lenzing AG, Lenzing, Austria under the trademark TENCEL®) which are widely used in the textile industry. Other cellulose products from lyocell technology have also been used.
Cellulose staple fibers have long been used as a component for conversion to nonwoven webs. However, adaption of lyocell technology to produce nonwoven webs directly would access properties and performance not possible for current cellulose web products. This could be considered as the cellulosic version of the meltblow and spunbond technologies widely used in the synthetic fiber industry, although it is not possible to directly adapt synthetic polymer technology to lyocell due to important technical differences.
Much research has been carried out to develop technology to directly form cellulose webs from lyocell solutions (inter alia, WO 98/26122 , WO 99/47733 , WO 98/07911 , US 6,197,230 , WO 99/64649 , WO 05/106085 , EP 1 358 369 , EP 2 013 390 ). Further art is disclosed in WO 07/124521 A1 and WO 07/124522 A1 .

Object and summary of the invention

It is an object of the invention to provide an environmentally compatible, in particular also skin friendly, cellulose-based fiber fabric having adjustable properties.
In order to achieve the object defined above, a nonwoven cellulose fiber fabric, a method of manufacturing a nonwoven cellulose fiber fabric, a device for manufacturing a nonwoven cellulose fiber fabric, a product or composite, and methods of use according to the independent claims are provided.
According to an exemplary embodiment of the invention, a (in particular solution-blown) nonwoven cellulose fiber fabric is provided (which is in particular directly (in particular in an in situ process or in a continuous process executable in a continuously operating production line) manufactured from lyocell spinning solution), and wherein a heavy metal content of the fibers (in particular of the fiber fabric) is not more than 10 ppm (in particular 10 mass ppm, i.e. 10 mg/kg) for each individual chemical heavy metal element.
According to another exemplary embodiment, a method of manufacturing (in particular solution-blown) nonwoven cellulose fiber fabric directly from lyocell spinning solution is provided, wherein the method comprises extruding the lyocell spinning solution through a jet with orifices supported by a gas flow into a coagulation fluid atmosphere (in particular an atmosphere of dispersed coagulation fluid) to thereby form substantially endless fibers, collecting the fibers on a fiber support unit to thereby form the fabric, and selecting operating fluids (for instance the lyocell spinning solution, the coagulation fluid, and/or the gas flow) used during manufacturing the fabric so that, and selecting materials of a manufacturing device which are in contact with at least one of the lyocell spinning solution and the fibers during manufacturing the fabric so that a heavy metal content of the fibers (in particular of the fiber fabric) is not more than 10 ppm (in particular 10 mass ppm, i.e. 10 mg/kg) for each individual chemical heavy metal element.
According to a further exemplary embodiment, a device for manufacturing (in particular solution-blown) nonwoven cellulose fiber fabric directly from lyocell spinning solution is provided, wherein the device comprises a jet with orifices configured for extruding the lyocell spinning solution supported by a gas flow, a coagulation unit configured for providing a coagulation fluid atmosphere for the extruded lyocell spinning solution to thereby form substantially endless fibers, a fiber support unit configured for collecting the fibers to thereby form the fabric, wherein materials of the device which are in contact with at least one of the lyocell spinning solution and the fibers during manufacturing the fabric are selected so that a heavy metal content of the fibers is not more than 10 ppm for each individual chemical heavy metal element. Fibers (in particular the fiber fabric) produced in the described way do/does hence preferably not comprise more than 10 ppm (in particular 10 mass ppm, i.e. 10 mg/kg) for each individual chemical heavy metal element.
According to still another exemplary embodiment, a product or composite is provided which comprises a fabric having the above mentioned properties.
According to yet another embodiment, a nonwoven cellulose fiber fabric having the above-mentioned properties is used for reinforcing at least one of the group consisting of an acoustic damping and a thermal isolation.
According to yet another embodiment, a nonwoven cellulose fiber fabric having the above-mentioned properties is used for at least one of the group consisting of a wipe, a dryer sheet, a filter, a hygiene product, a medical application product, a geotextile, agrotextile, clothing, a product for building technology, an automotive product, a furnishing, an industrial product, a product related to beauty, leisure, sports or travel, and a product related to school or office.
In the context of this application, the term "nonwoven cellulose fiber fabric" (which may also be denoted as nonwoven cellulose filament fabric) may particularly denote a fabric or web composed of a plurality of substantially endless fibers. The term "substantially endless fibers" has in particular the meaning of filament fibers having a significantly longer length than conventional staple fibers. In an alternative formulation, the term "substantially endless fibers" may in particular have the meaning of a web formed of filament fibers having a significantly smaller amount of fiber ends per volume than conventional staple fibers. In particular, endless fibers of a fabric according to an exemplary embodiment of the invention may have an amount of fiber ends per volume of less than 10,000 ends/cm³, in particular less than 5,000 ends/cm³. For instance, when staple fibers are used as a substitute for cotton, they may have a length of 38 mm (corresponding to a typical natural length of cotton fibers). In contrast to this, substantially endless fibers of the nonwoven cellulose fiber fabric may have a length of at least 200 mm, in particular at least 1000 mm. However, a person skilled in the art will be aware of the fact that even endless cellulose fibers may have interruptions, which may be formed by processes during and/or after fiber formation. As a consequence, a nonwoven cellulose fiber fabric made of substantially endless cellulose fibers has a significantly lower number of fibers per mass compared to nonwoven fabric made from staple fibers of the same denier. A nonwoven cellulose fiber fabric may be manufactured by spinning a plurality of fibers and by attenuating and stretching the latter towards a preferably moving fiber support unit. Thereby, a three-dimensional network or web of cellulose fibers is formed, constituting the nonwoven cellulose fiber fabric. The fabric may be made of cellulose as main or only constituent.
In the context of this application, the term "lyocell spinning solution" may particularly denote a solvent (for example a polar solution of a material such as N-methyl-morpholine, NMMO, "amine oxide" or "AO") in which cellulose (for instance wood pulp or other cellulose-based feedstock) is dissolved. The lyocell spinning solution is a solution rather than a melt. Cellulose filaments may be generated from the lyocell spinning solution by reducing the concentration of the solvent, for instance by contacting said filaments with water. The process of initial generation of cellulose fibers from a lyocell spinning solution can be described as coagulation.
In the context of this application, the term "gas flow" may particularly denote a flow of gas such as air substantially parallel to the moving direction of the cellulose fiber or its preform (i.e. lyocell spinning solution) while and/or after the lyocell spinning solution leaves or has left the spinneret.
In the context of this application, the term "coagulation fluid" may particularly denote a non-solvent fluid (i.e. a gas and/or a liquid, optionally including solid particles) which has the capability of diluting the lyocell spinning solution and exchanging with the solvent to such an extent that the cellulose fibers are formed from the lyocell filaments. For instance, such a coagulation fluid may be water mist.
In the context of this application, the term "process parameters" may particularly denote all physical parameters and/or chemical parameters and/or device parameters of substances and/or device components used for manufacturing nonwoven cellulose fiber fabric which may have an impact on the properties of the fibers and/or the fabric, in particular on fiber diameter and/or fiber diameter distribution. Such process parameters may be adjustable automatically by a control unit and/or manually by a user to thereby tune or adjust the properties of the fibers of the nonwoven cellulose fiber fabric. Physical parameters which may have an impact on the properties of the fibers (in particular on their diameter or diameter distribution) may be temperature, pressure and/or density of the various media involved in the process (such as the lyocell spinning solution, the coagulation fluid, the gas flow, etc.). Chemical parameters may be concentration, amount, pH value of involved media (such as the lyocell spinning solution, the coagulation fluid, etc.). Device parameters may be size of and/or distances between orifices, distance between orifices and fiber support unit, speed of transportation of fiber support unit, the provision of one or more optional in situ post processing units, the gas flow, etc.
The term "fibers" may particularly denote elongated pieces of a material comprising cellulose, for instance roughly round or non-regularly formed in cross-section, optionally twisted with other fibers. Fibers may have an aspect ratio which is larger than 10, particularly larger than 100, more particularly larger than 1000. The aspect ratio is the ratio between the length of the fiber and a diameter of the fiber. Fibers may form networks by being interconnected by merging (so that an integral multi-fiber structure is formed) or by friction (so that the fibers remain separate but are weakly mechanically coupled by a friction force exerted when mutually moving the fibers being in physical contact with one another). Fibers may have a substantially cylindrical form which may however be straight, bent, kinked, or curved. Fibers may consist of a single homogenous material (i.e. cellulose). However, the fibers may also comprise one or more additives. Liquid materials such as water or oil may be accumulated between the fibers.
In the context of this document, a "jet with orifices" (which may for instance be denoted as an "arrangement of orifices") may be any structure comprising an arrangement of orifices which are linearly arranged.
In the context of this application, the term "heavy metals" may particularly denote metallic chemical elements having a density of more than 5 g/cm³ and/or an atomic number of at least 24. In particular, heavy metals may include the elements of the following list: Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Cd, Sn, W, Pb, Bi.
The ppm values mentioned in this application may all relate to mass ppm (rather than to volume ppm), i.e. may denote the ratio mg heavy metal / kg fibers.
For determining a heavy metal content of a nonwoven cellulose fiber fabric, chemical extraction can be carried out in accordance with EN 15587-2 (in the latest version as in force at the priority date of the present patent application). The measurement of the heavy metal content can be carried out in accordance with EN 17294-2 (in the latest version as in force at the priority date of the present patent application), in particular by ICP-MS (Inductively Coupled Plasma Mass Spectrometry).
According to an exemplary embodiment, a nonwoven cellulose fiber fabric is provided which has a very small content with heavy metals. It has turned out that a method of manufacturing such a fabric using a lyocell spinning solution composed of a dissolved cellulose source (such as wood pulp), a non-polar solvent (such as N-methyl-morpholine, NMMO) and water is capable of providing a nonwoven cellulose fiber fabric with less than 10 mass ppm (i.e. 10 mg heavy metal content/kg fibers) heavy metal content per chemical element (i.e. in particular less than 10 mass ppm for each individual chemical heavy metal element of the group of chemical elements consisting of Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Cd, Sn, W, Pb, Bi). The manufacturability of such an environmentally friendly cellulose fiber fabric is based on the consideration that it is possible to omit any substantial heavy metal elements in the ingredients of the lyocell spinning solution which can be coagulated in an aqueous coagulation fluid which may thus be also provided substantially free of heavy metal comprising constituents. Moreover, also the process parameters of operating the device as well as the hardware configuration of the device can be set to prevent introduction of significant amounts of heavy metals in the production line and consequently in the obtained fabric. For instance, since bush bearings with heavy metal content in pumps can conventionally be a source of undesired heavy metal carryover into the fabric, corresponding shielding mechanisms may be implemented or alternative hardware may be used for preventing contact between such sources of heavy metals and fibers or preforms thereof. Thus, the advantageous heavy metal depletion of the manufactured nonwoven cellulose fiber fabric can be obtained by omitting heavy metal content in the operating fluids (in particular lyocell spinning solution, coagulation fluid, optional wash liquor, gas flow) involved in the process and in the device components getting into physical contact with the operating fluids and the manufactured fibers. By ensuring compliance with the mentioned small residual amounts of heavy metals in the manufactured fibers or fabric by the described adjustment of the process parameters, a highly biocompatible fabric can be obtained which has a high degree of purity. The fabric is in particular environmentally friendly and skin friendly due to its sustainable sourcing, its biodegradability and the very low heavy metal content. Moreover, the manufactured fabric is of high quality, since substantially no heavy metal content promoting decomposition of the lyocell spinning solution is present. This high degree of purity thus allows to obtain substantially endless fibers with a very small number of fiber ends and with reproducible physical properties. The properties, in particular the mechanical properties, of such a fabric may therefore be adjusted precisely and predictively by controlling the process parameters without mentionable deteriorations by heavy metal impurities.
Thus, materials of the operating fluids (i.e. liquids and/or gases on the basis of which the fibers are formed, and/or which interact with - in particular with physical contact to - the fibers or preforms thereof during the manufacturing process) and materials of the manufacturing device (for instance jets, fiber support unit, fluid containers, etc.) getting into contact with the fibers or preforms thereof during the manufacturing process may be configured to prevent an introduction of heavy metals into the lyocell spinning solution, the fibers and/or the fabric. When taking these measures during the manufacturing process, a nonwoven cellulose fiber fabric with an inherently small heavy metal content can be advantageously obtained. More specifically, it is possible in an embodiment that a raw material pulp as well as the materials inside the plant which are in contact with the cellulose are chosen such that the heavy metal content of the fibers or fabric meets the above-mentioned conditions.

Detailed description of embodiments of the invention

In the following, further exemplary embodiments of the nonwoven cellulose fiber fabric, the method of manufacturing a nonwoven cellulose fiber fabric, the device for manufacturing a nonwoven cellulose fiber fabric, the product or composite, and the methods of use are described.
With the described low heavy metal content of the manufactured fabric, it is possible to obtain a density of fiber ends in the fabric of less than 10,000 fiber ends per cm³, in particular of less than 5,000 fiber ends per cm³. Therefore, the mechanical integrity and therefore stability of the manufactured fabric is very high.
In an embodiment, an overall heavy metal content of the fibers (in particular of the fiber fabric) is not more than 30 ppm (in particular 30 mass ppm, i.e. 30 mg/kg). In other words, a sum of all heavy metals of the individual chemical elements in the fabric may be at or below a level of 30 ppm. Thus, the entire heavy metal content of the fabric integrated over all heavy metal elements (in particular including summed contributions from the chemical elements of the group consisting of Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Cd, Sn, W, Pb, Bi) may be kept below 30 ppm. With this small overall heavy metal concentration in the fabric it can be ensured that no undesired decomposition of the lyocell spinning solution occurs during manufacturing the fibers. This has a positive impact on fiber quality, reproducibility of the manufacturing process and a pronounced endless character of the obtained fibers while simultaneously an ecological footprint can be further reduced.
In an embodiment, the fibers have (in particular the fiber fabric has) a copper content of less than 5 ppm (in particular 5 mass ppm, i.e. 5 mg/kg) and/or have a nickel content of less than 2 ppm (in particular 2 mass ppm, i.e. 2 mg/kg). Due to the use of a lyocell spinning solution as a basis for the formation of the endless fiber-based fabric (in particular when involving a solvent such as N-methyl-morpholine, NMMO), the content of the fabric with the mentioned particularly harmful heavy metals copper (which may be harmful to health for human beings, in particular for children, when exceeding a certain dose) and/or nickel (which may cause allergic reactions of a user) may be kept extremely small. In particular, the very small amount of copper content can be ensured by omitting a copper salt solution for preparing the spinning solution.
In an embodiment, at least part of (in particular at least 10% of) the fibers are integrally merged at merging positions. In the context of this application, the term "merging" may particularly denote an integral interconnection of different fibers at the respective merging position which results in the formation of one integrally connected fiber structure composed of the previously separate fiber preforms. Merging may be denoted as a fiber-fiber connection being established during coagulation of one, some or all of the merged fibers. Interconnected fibers may strongly adhere to one another at a respective merging position without a different additional material (such as a separate adhesive) so as to form a common structure. Separation of merged fibers may require destruction of the fiber network or part thereof. According to the described embodiment, a nonwoven cellulose fiber fabric is provided in which some or all of the fibers are integrally connected to one another by merging. Merging may be triggered by a corresponding control of the process parameters of a method of manufacturing the nonwoven cellulose fiber fabric. In particular, coagulation of filaments of lyocell spinning solution may be triggered (or at least completed) after the first contact between these filaments being not yet in the precipitated solid fiber state. Thereby, interaction between these filaments while still being in the solution phase and then or thereafter converting them into the solid-state phase by coagulation allows to properly adjust the merging characteristics. A degree of merging is a powerful parameter which can be used for adjusting the properties of the manufactured fabric. In particular, mechanical stability of the network is the larger the higher the density of merging positions is. By an inhomogeneous distribution of merging positions over the volume of the fabric, it is also possible to adjust regions of high mechanical stability and other regions of low mechanical stability. For instance, separation of the fabric into separate parts can be precisely defined to happen locally at mechanical weak regions with a low number of merging positions. In a preferred embodiment, merging between fibers is triggered by bringing different fiber preforms in form of lyocell spinning solution in direct contact with one another prior to coagulation. By such a coagulation process, single material common precipitation of the fibers is executed, thereby forming the merging positions.
Due to the concept of direct merging of fibers under certain conditions adjustable by process control, no extra material (such as a binder or the like) needs to be introduced in the process for interconnecting the fibers. This keeps impurities of the fabric very low. Thus, interconnecting fibers by merging rather than adhering them using a separate adhesive material additionally contributes to the high degree of purity of the manufactured fabric and promotes the efforts to keep heavy metals content very low.
In an embodiment, the merging positions consist of the same material as the merged fibers. Thus, the merging positions may be formed by cellulose material resulting directly from the coagulation of lyocell spinning solution. This not only renders the separate provision of a fiber connection material (such as an adhesive or a binder) dispensable, but also keeps the fabric clean and made substantially of a single material.
In an embodiment, different ones of the fibers are located at least partially in different distinguishable (i.e. showing a visible separation or interface region in between the layers on a scanning electroscopic image) layers. More specifically, fibers of different layers are integrally merged at at least one merging position between the layers. Hence, different ones of the fibers being located at least partially in different distinguishable layers (which may be identical or which may differ concerning one or more parameters such as merging factor, fiber diameter, etc.) may be integrally connected at at least one merging position. For instance, two (or more) different layers of a fabric may be formed by serially aligning two (or more) jets with orifices through which lyocell spinning solution is extruded for coagulation and fiber formation. When such an arrangement is combined with a moving fiber support unit (such as a conveyor belt with a fiber accommodation surface), a first layer of fibers is formed on the fiber support unit by the first jet, and the second jet forms a second layer of fibers on the first layer when the moving fiber support unit reaches the position of the second jet. The process parameters of this method may be adjusted so that merging points are formed between the first layer and the second layer. In particular, fibers of the second layer under formation being not yet fully cured or solidified by coagulation may for example still have exterior skin or surface regions which are still in the liquid lyocell solution phase and not yet in the fully cured solid state. When such pre-fiber structures come into contact with one another and fully cure into the solid fiber state thereafter, this may result in the formation of two merged fibers at an interface between different layers. The higher the number of merging positions, the higher is the stability of the interconnection between the layers of the fabric. Thus, controlling merging allows to control rigidity of the connection between the layers of the fabric. Merging can be controlled, for example, by adjusting the degree of curing or coagulation before pre-fiber structures of a respective layer reach the fiber support plate on an underlying layer of fibers or pre-fiber structures. By merging of fibers of different layers at an interface there between, undesired separation of the layers may be prevented. In the absence of merging points between the layers, peeling off one layer from the other layer of fibers may be made possible.
In an embodiment, the merging between the different layers is adjusted so that pulling on the layers in opposite directions results in a separation of the fabric at an interface between the different layers. This can be achieved when the merging is adjusted so that merging-based adhesion between the different layers is smaller than merging based adhesion within a respective one of the different layers. In particular, a number of merging points or merging positions per volume may be larger in an interior of a respective one of the connected layers than at in an interface region between the layers. This can be manufactured by controlling the relation between inter-layer coagulation and intra-layer coagulation.
In an embodiment, an average diameter of the fibers of one of the layers is different from an average diameter of the fibers of another one of the layers. For instance, a ratio between the average diameter of the fibers of the one layer and the average diameter of the fibers of the other layer may be at least 1.5, in particular may be at least 2.5, more particularly may be at least 4. Thus, a nonwoven cellulose fiber fabric may be provided which can be manufactured as a network of substantially endless cellulose fibers showing a pronounced inhomogeneity in terms of fiber diameter between different layers (but additionally or alternatively also within one layer). It has turned out that the distribution of diameters of the fibers of the nonwoven cellulose fiber fabric is a powerful design parameter for adjusting the physical properties, in particular the mechanical properties, of the obtained fabric. Without wishing to be bound to a specific theory, it is presently believed that such an inhomogeneous distribution of fiber thicknesses results in a self-organization of the fiber network which inhibits mutual motion of the individual fibers relative to one another. In contrast to this, the fibers tend to clamp together, thereby obtaining a compound with a high rigidity. Descriptively speaking, introducing a certain inhomogeneity in the fiber manufacturing process may translate into an inhomogeneity of the thickness or diameter distribution of the fibers in the fabric as a whole. However, it should be mentioned that by varying fiber diameter as a design parameter for a fabric, fiber physics may be adjusted in a more general way allowing to vary physical properties of the fabric over a broad range (wherein reinforcing stiffness is only one option or example). For instance, fiber diameter variation can also be a powerful tool for tuning moisture management of the manufactured fabric.
In an embodiment, the fibers comprise or consists of microfibrillar cellulose. Such a microfibril may be denoted as a very fine fibril, or fiber-like strand, consisting of cellulose. Cellulose fibers may be built up of fiber bundles, which may be composed of smaller elements called microfibrils. Through a fibrillation process, the cellulose fibers may be converted into a three-dimensional network of microfibrils with a high surface area. As a result of the high purity and low heavy metals content of the fiber material, also the accurate formation of a microfibrillar structure is promoted.
In an embodiment, the fabric is configured as a lotion delivery system. In view of the biocompatible properties of the manufactured fabric due to the low heavy metal content (see for instance the anti-allergic effect of a low nickel content), the manufactured fabric is highly appropriate for cosmetic applications such as facial masks, make-up removal pads, or the like. Lotion may be stored or retained in an interior of the fabric and may be released when applying pressure during use or operation.
In an embodiment, the fiber network comprises certain functions, in particular at least one of the group consisting of wicking, anisotropic behavior, oil retention, water retention, cleanability, and roughness. Such a functionalization may be obtained by an adjustment of physical properties of the fibers and the fabric composed thereof, in particular by an adjustment of a merging factor, an adjustment of a multilayer configuration of a fabric, an adjustment of fiber thickness and an adjustment of the fabric density corresponding to number and dimension of hollow spaces in an interior of the fabric. Secondly, such a functionalization can be performed with a multilayer fabric so that, in an embodiment, the fibers located in multiple layers may be provided with different functionalities. Different functionalities of different layers may be the result of different fiber diameters and/or different fiber diameter distributions and/or different fiber density and/or merging properties. For example, the (in particular different) functionalities may be wicking properties (in particular different fluid distribution properties when sucking fluid), anisotropic behavior (in particular different mechanical, chemical and/or hydrodynamic properties in different directions of the fabric), oil absorbing capability (in particular a strong capability of absorbing oil in one layer, and a lower oil absorbing capability in another layer), water absorbing capability (in particular a strong capability of absorbing water in one layer, and a lower water absorbing capability in another layer), cleanability (in particular a stronger capability of cleaning dirt from a surface by the fabric in one layer, and a less pronounced capability of cleaning in another layer), and/or roughness (for instance one rougher surface layer and one smoother surface layer).
In an embodiment, the lyocell spinning solution is free of copper salt, in particular is free of any heavy metal salt. This promotes purity of the manufactured fiber and results in a high quality of the formed endless fibers.
In an embodiment, the method further comprises further processing the fibers and/or the fabric after collection on the fiber support unit but preferably still in situ with the formation of the nonwoven cellulose fiber fabric with endless fibers. Such in situ processes may be those processes being carried out before the manufactured (in particular substantially endless) fabric is stored (for instance wound by a winder) for shipping to a product manufacture destination. For instance, such a further processing or post processing may involve hydroentanglement. Hydroentanglement may be denoted as a bonding process for wet or dry fibrous webs, the resulting bonded fabric being a nonwoven. Hydroentanglement may use fine, high pressure jets of water which penetrate the web, hit a fiber support unit (in particular a conveyor belt) and bounce back causing the fibers to entangle. A corresponding compression of the fabric may render the fabric more compact and mechanically more stable. Additionally or alternatively to hydroentanglement, steam treatment of the fibers with a pressurized steam may be carried out. Additionally or alternatively, such a further processing or post processing may involve a needling treatment of the manufactured fabric. A needle punching system may be used to bond the fibers of the fabric or web. Needle punched fabrics may be produced when barbed needles are pushed through the fibrous web forcing some fibers through the web, where they remain when the needles are withdrawn. If sufficient fibers are suitably displaced the web may be converted into a fabric by the consolidating effect of these fibers plugs. Yet another further processing or post processing treatment of the web or fabric is an impregnating treatment. Impregnating the network of endless fibers may involve the application of one or more chemicals (such as a softener, a hydrophobic agent, an antistatic agent, etc.) on the fabric. Still another further processing treatment of the fabric is calendering. Calendering may be denoted as a finishing process for treating the fabric and may employ a calender to smooth, coat, and/or compress the fabric.
A nonwoven cellulose fiber fabric according to an exemplary embodiment of the invention may also be combined (for instance in situ or in a subsequent process) with one or more other materials, to thereby form a composite according to an exemplary embodiment of the invention. Exemplary materials, which can be combined with the fabric for forming such a composite may be selected from a group of materials comprising, but not being limited to, the following materials or combinations thereof: fluff pulp, a fiber suspension, a wetlaid nonwoven, an airlaid nonwoven, a spunbond web, a meltblown web, a carded spunlaced or needlepunched web or other sheet like structures made of various materials. In an embodiment, the connection between the different materials can be done by (but not limited to) one or a combination of the following processes: merging, hydroentanglement, needle punching, hydrogen bonding, thermobonding, gluing by a binder, laminating, and/or calendering.
In the following, exemplary advantageous products comprising, or uses of, a nonwoven cellulose fiber fabric according to exemplary embodiments of the invention are summarized:

Particular uses of the webs, either 100% cellulose fiber webs, or for example webs comprising or consisting of two or more fibers, or chemically modified fibers or fibers with incorporated materials such as anti-bacterial materials, ion exchange materials, active carbon, nano particles, lotions, medical agents or fire retardants, or bicomponent fibers may be as follows:
- The nonwoven cellulose fiber fabric according to exemplary embodiments of the invention may be used for manufacturing wipes such as baby, kitchen, wet wipes, cosmetic, hygiene, medical, cleaning, polishing (car, furniture), dust, industrial, duster and mops wipes.

It is also possible that the nonwoven cellulose fiber fabric according to exemplary embodiments of the invention is used for manufacturing a filter. For instance, such a filter may be an air filter, a HVAC, air condition filter, flue gas filter, liquid filters, coffee filters, tea bags, coffee bags, food filters, water purification filter, blood filter, cigarette filter; cabin filters, oil filters, cartridge filter, vacuum filter, vacuum cleaner bag, dust filter, hydraulic filter, kitchen filter, fan filter, moisture exchange filters, pollen filter, HEVAC/HEPA/ULPA filters, beer filter, milk filter, liquid coolant filter and fruit juices filters.
In yet another embodiment, the nonwoven cellulose fiber fabric may be used for manufacturing absorbent hygiene products. Examples thereof are an acquisition layer, a coverstock, a distribution layer, an absorbent cover, sanitary pads, topsheets, backsheets, leg cuffs, flushable products, pads, nursing pads, disposal underwear, training pants, face masks, beauty facial masks, cosmetic removal pads, washcloths, diapers, and sheets for a laundry dryer releasing an active component (such as a textile softener).
In still another embodiment, the nonwoven cellulose fiber fabric may be used for manufacturing a medical application product. For instance, such medical application products may be disposable caps, gowns, masks and shoe cover, wound care products, sterile packaging products, coverstock products, dressing materials, one way clothing, dialyses products, nasal strips, adhesives for dental plates, disposal underwear, drapes, wraps and packs, sponges, dressings and wipes, bed linen, transdermal drug delivery, shrouds, underpads, procedure packs, heat packs, ostomy bag liners, fixation tapes and incubator mattresses.
In yet another embodiment, the nonwoven cellulose fiber fabric may be used for manufacturing geotextiles. This may involve the production of crop protection covers, capillary matting, water purification, irrigation control, asphalt overlay, soil stabilisation, drainage, sedimentation and erosion control, pond liners, impregnation based, drainage channel liners, ground stabilisation, pit linings, seed blankets, weed control fabrics, greenhouse shading, root bags and biodegradable plant pots. It is also possible to use the nonwoven cellulose fiber fabric for a plant foil (for instance providing a light protection and/or a mechanical protection for a plant, and/or providing the plant or soil with dung or seed).
In another embodiment, the nonwoven cellulose fiber fabric may be used for manufacturing clothing. For example, interlinings, clothing insulation and protection, handbag components, shoe components, belt liners, industrial headwear/foodwear, disposable workwear, clothing and shoe bags and thermal insulation may be manufactured on the basis of such fabric.
In still another embodiment, the nonwoven cellulose fiber fabric may be used for manufacturing products used for building technology. For instance, roofing and tile underlay, underslating, thermal and noise insulation, house wrap, facings for plaster board, pipe wrap, concrete moulding layers, foundations and ground stabilisation, vertical drainages, shingles, roofing felts, noise abatement, reinforcement, sealing material, and damping material (mechanical) may be manufactured using such fabric.
In still another embodiment, the nonwoven cellulose fiber fabric may be used for manufacturing an automotive product. Examples are a cabin filter, boot liners, parcel shelves, heat shields, shelf trim, moulded bonnet liners, boot floor covering, oil filter, headliners, rear parcel shelves, decorative fabrics, airbags, silencer pads, insulation materials, car covers, underpadding, car mats, tapes, backing and tufted carpets, seat covers, door trim, needled carpet, and auto carpet backing.
Still another field of application of fabric manufactured according to exemplary embodiments of the invention are furnishings, such as furniture, construction, insulator to arms and backs, cushion thicking, dust covers, linings, stitch reinforcements, edge trim materials, bedding constructions, quilt backing, spring wrap, mattress pad components, mattress covers, window curtains, wall coverings, carpet backings, lampshades, mattress components, spring insulators, sealings, pillow ticking, and mattress ticking.
In yet another embodiment, the nonwoven cellulose fiber fabric may be used for manufacturing industrial products. This may involve electronics, floppy disc liners, cable insulation, abrasives, insulation tapes, conveyor belts, noise absorbent layers, air conditioning, battery separators, acid systems, anti-slip matting stain removers, food wraps, adhesive tape, sausage casing, cheese casing, artificial leather, oil recovery booms and socks, and papermaking felts.
Nonwoven cellulose fiber fabric according to exemplary embodiments of the invention is also appropriate for manufacturing products related to leisure and travel. Examples for such an application are sleeping bags, tents, luggage, handbags, shopping bags, airline headrests, CD-protection, pillowcases, and sandwich packaging.
Still another field of application of exemplary embodiment of the invention relates to school and office products. As examples, book covers, mailing envelopes, maps, signs and pennants, towels, and flags shall be mentioned.

Brief description of the drawings

The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited:

Figure 1 illustrates a device for manufacturing nonwoven cellulose fiber fabric which is directly formed from lyocell spinning solution being coagulated by a coagulation fluid according to an exemplary embodiment of the invention.
Figure 2 to Figure 4 show experimentally captured images of nonwoven cellulose fiber fabric according to an exemplary embodiment of the invention in which merging of individual fibers has been accomplished by a specific process control.
Figure 5 and Figure 6 show experimentally captured images of nonwoven cellulose fiber fabric according to an exemplary embodiment of the invention in which swelling of fibers has been accomplished, wherein Figure 5 shows the fiber fabric in a dry non-swollen state and Figure 6 shows the fiber fabric in a humid swollen state.
Figure 7 shows an experimentally captured image of nonwoven cellulose fiber fabric according to an exemplary embodiment of the invention in which formation of two superposed layers of fibers has been accomplished by a specific process implementing two serial bars of nozzles.
Figure 8 shows a schematic image of a nonwoven cellulose fiber fabric according to still another exemplary embodiment of the invention composed of two stacked and merged layers of interconnected fibers having different fiber thicknesses.
Figure 9 illustrates a part of a device for manufacturing nonwoven cellulose fiber fabric composed of two stacked layers of endless cellulose fiber webs according to an exemplary embodiment of the invention.
Figure 10 shows a schematic image of nonwoven cellulose fiber fabric according to an exemplary embodiment of the invention composed of three stacked layers with different diameters of fibers.

Detailed description of the drawings

The illustrations in the drawings are schematic. In different drawings similar or identical elements are provided with the same reference labels.
Figure 1 illustrates a device 100 according to an exemplary embodiment of the invention for manufacturing nonwoven cellulose fiber fabric 102 which is directly formed from lyocell spinning solution 104. The latter is at least partly coagulated by a coagulation fluid 106 to be converted into partly-formed cellulose fibers 108. By the device 100, a lyocell solution blowing process according to an exemplary embodiment of the invention may be carried out. In the context of the present application, the term "lyocell solution-blowing process" may particularly encompass processes which can result in essentially endless filaments or fibers 108 of a discrete length or mixtures of endless filaments and fibers of discrete length being obtained. As further described below, nozzles each having an orifice 126 are provided through which cellulose solution or lyocell spinning solution 104 is ejected together with a gas stream or gas flow 146 for manufacturing the nonwoven cellulose fiber fabric 102 according to an exemplary embodiment of the invention.
As can be taken from Figure 1, wood pulp 110, other cellulose-based feedstock or the like may be supplied to a storage tank 114 via a metering unit 113. Water from a water container 112 is also supplied to the storage tank 114 via metering unit 113. Thus, the metering unit 113, under control of a control unit 140 described below in further detail, may define relative amounts of water and wood pulp 110 to be supplied to the storage tank 114. A solvent (such as N-methyl-morpholine, NMMO) accommodated in a solvent container 116 may be concentrated in a concentration unit 118 and may then be mixed with the mixture of water and wood pulp 110 or other cellulose-based feedstock with definable relative amounts in a mixing unit 119. Also the mixing unit 119 can be controlled by the control unit 140. Thereby, the water-wood pulp 110 medium is dissolved in the concentrated solvent in a dissolving unit 120 with adjustable relative amounts, thereby obtaining lyocell spinning solution 104. The aqueous lyocell spinning solution 104 can be a honey-viscous medium composed of (for instance 5 mass % to 15 mass %) cellulose comprising wood pulp 110 and (for instance 85 mass % to 95 mass %) solvent.
The lyocell spinning solution 104 is forwarded to a fiber formation unit 124 (which may be embodied as or which may comprise a number of spinning beams or jets 122). For instance, the number of orifices 126 of the jets 122 may be larger than 50, in particular larger than 100. In one embodiment, all orifices 126 of a fiber formation unit 124 (which may comprise a number of spinnerets or jets 122) of orifices 126 of the jets 122 may have the same size and/or shape. Alternatively, size and/or shape of different orifices 126 of one jet 122 and/or orifices 126 of different jets 122 (which may be arranged serially for forming a multilayer fabric) may be different.
When the lyocell spinning solution 104 passes through the orifices 126 of the jets 122, it is divided into a plurality of parallel strands of lyocell spinning solution 104. A vertically oriented gas flow, i.e. being oriented substantially parallel to spinning direction, forces the lyocell spinning solution 104 to transform into increasingly long and thin strands which can be adjusted by changing the process conditions under control of control unit 140. The gas flow may accelerate the lyocell spinning solution 104 along at least a part of its way from the orifices 126 to a fiber support unit 132.
While the lyocell spinning solution 104 moves through the jets 122 and further downward, the long and thin strands of the lyocell spinning solution 104 interact with non-solvent coagulation fluid 106. The coagulation fluid 106 is advantageously embodied as a vapor mist, for instance an aqueous mist. Process relevant properties of the coagulation fluid 106 are controlled by one or more coagulation units 128, providing the coagulation fluid 106 with adjustable properties. The coagulation units 128 are controlled, in turn, by control unit 140. Preferably, respective coagulation units 128 are provided between the individual nozzles or orifices 126 for individually adjusting properties of respective layers of fabric 102 being produced. Preferably, each jet 122 may have two assigned coagulation units 128, one from each side. The individual jets 122 can thus be provided with individual portions of lyocell spinning solution 104 which may also be adjusted to have different controllable properties of different layers of manufactured fabric 102.
When interacting with the coagulation fluid 106 (such as water), the solvent concentration of the lyocell spinning solution 104 is reduced, so that the cellulose of the former e.g. wood pulp 110 (or other feedstock) is at least partly coagulated as long and thin cellulose fibers 108 (which may still contain residual solvent and water).
During or after initial formation of the individual cellulose fibers 108 from the extruded lyocell spinning solution 104, the cellulose fibers 108 are deposited on fiber support unit 132, which is here embodied as a conveyor belt with a planar fiber accommodation surface. The cellulose fibers 108 form a nonwoven cellulose fiber fabric 102 (illustrated only schematically in Figure 1). The nonwoven cellulose fiber fabric 102 is composed of continuous and substantially endless filaments or fibers 108.
Although not shown in Figure 1, the solvent of the lyocell spinning solution 104 removed in coagulation by the coagulation unit 128 and in washing in a washing unit 180 can be at least partially recycled.
While being transported along the fiber support unit 132, the nonwoven cellulose fiber fabric 102 can be washed by washing unit 180 supplying wash liquor to remove residual solvent and may then be dried. It can be further processed by an optional but advantageous further processing unit 134. For instance, such a further processing may involve hydro-entanglement, needle punching, impregnation, steam treatment with a pressurized steam, calendering, etc.
The fiber support unit 132 may also transport the nonwoven cellulose fiber fabric 102 to a winder 136 on which the nonwoven cellulose fiber fabric 102 may be collected as a substantially endless sheet. The nonwoven cellulose fiber fabric 102 may then be shipped as roll-good to an entity manufacturing products such as wipes or textiles based on the nonwoven cellulose fiber fabric 102.
As indicated in Figure 1, the described process may be controlled by control unit 140 (such as a processor, part of a processor, or a plurality of processors). The control unit 140 is configured for controlling operation of the various units shown in Figure 1, in particular one or more of the metering unit 113, the mixing unit 119, the fiber formation unit 124, the coagulation unit(s) 128, the further processing unit 134, the dissolution unit 120, the washing unit 118, etc. Thus, the control unit 140 (for instance by executing computer executable program code, and/or by executing control commands defined by a user) may precisely and flexibly define the process parameters according to which the nonwoven cellulose fiber fabric 102 is manufactured. Design parameters in this context are air flow along the orifices 126, properties of the coagulation fluid 106, drive speed of the fiber support unit 132, composition, temperature and/or pressure of the lyocell spinning solution 104, etc. Additional design parameters which may be adjusted for adjusting the properties of the nonwoven cellulose fiber fabric 102 are number and/or mutual distance and/or geometric arrangement of the orifices 126, chemical composition and degree of concentration of the lyocell spinning solution 104, etc. Thereby, the properties of the nonwoven cellulose fiber fabric 102 may be properly adjusted, as described below. Such adjustable properties (see below detailed description) may involve one or more of the following properties: diameter and/or diameter distribution of the fibers 108, amount and/or regions of merging between fibers 108, a purity level of the fibers 108, properties of a multilayer fabric 102, optical properties of the fabric 102, fluid retention and/or fluid release properties of the fabric 102, mechanical stability of the fabric 102, smoothness of a surface of the fabric 102, cross-sectional shape of the fibers 108, etc.
Although not shown, each spinning jet 122 may comprise a polymer solution inlet via which the lyocell spinning solution 104 is supplied to the jet 122. Via an air inlet, a gas flow 146 can be applied to the lyocell spinning solution 104. Starting from an interaction chamber in an interior of the jet 122 and delimited by a jet casing, the lyocell spinning solution 104 moves or is accelerated (by the gas flow 146 pulling the lyocell spinning solution 104 downwardly) downwardly through a respective orifice 126 and is laterally narrowed under the influence of the gas flow 146 so that continuously tapering cellulose filaments or cellulose fibers 108 are formed when the lyocell spinning solution 104 moves downwardly together with the gas flow 146 in the environment of the coagulation fluid 106.
Thus, processes involved in the manufacturing method described by reference to Figure 1 may include that the lyocell spinning solution 104, which may also be denoted as cellulose solution is shaped to form liquid strands or latent filaments, which are drawn by the gas flow 146 and significantly decreased in diameter and increased in length. Partial coagulation of latent filaments or fibers 108 (or preforms thereof) by coagulation fluid 106 prior to or during web formation on the fiber support unit 132 may also be involved. The filaments or fibers 108 are formed into web like fabric 102, washed, dried and may be further processed (see further processing unit 134), as required. The filaments or fibers 108 may for instance be collected, for example on a rotating drum or belt, whereby a web is formed.
As a result of the described manufacturing process and in particular the choice of solvent used, the fibers 108 have a copper content of less than 5 ppm and have a nickel content of less than 2 ppm. This advantageously improves purity of the fabric 102.
The lyocell solution blown web (i.e. the nonwoven cellulose fiber fabric 102) according to exemplary embodiments of the invention preferably exhibits one or more of the following properties:

(i) The dry weight of the web is from 5 to 300 g/m², preferably 10-80 g/m²
(ii) The thickness of the web according to the standard WSP120.6 respectively DIN29073 (in particular in the latest version as in force at the priority date of the present patent application) is from 0.05 to 10.0 mm, preferably 0.1 to 2.5 mm
(iii) The specific tenacity of the web in MD according to EN29073-3, respectively ISO9073-3 (in particular in the latest version as in force at the priority date of the present patent application) ranges from 0.1 to 3.0 Nm²/g, preferably from 0.4 to 2.3 Nm²/g
(iv) The average elongation of the web according to EN29073-3, respectively ISO9073-3 (in particular in the latest version as in force at the priority date of the present patent application) ranges from 0.5 to 100%, preferably from 4 to 50%.
(v) The MD/CD tenacity ratio of the web is from 1 to 12
(vi) The water retention of the web according to DIN 53814 (in particular in the latest version as in force at the priority date of the present patent application) is from 1 to 250%, preferably 30 to 150%
(vii) The water holding capacity of the web according to DIN 53923 (in particular in the latest version as in force at the priority date of the present patent application) ranges from 90 to 2000%, preferably 400 to 1100%.
(viii) Metal residue levels of copper content of less than 5 ppm and nickel content of less than 2 ppm, according to the standards EN 15587-2 for the substrate decomposition and EN 17294-2 for the ICP-MS analysis (in particular in the latest version as in force at the priority date of the present patent application).

Most preferably, the lyocell solution-blown web exhibits all of said properties (i) to (viii) mentioned above.
As described, the process to produce the nonwoven cellulose fiber fabric 102 preferably comprises:

(a) Extruding a solution comprising cellulose dissolved in NMMO (see reference numeral 104) through the orifices 126 of at least one jet 122, thereby forming filaments of lyocell spinning solution 104
(b) Stretching said filaments of lyocell spinning solution 104 by a gaseous stream (see reference numeral 146)
(c) Contacting said filaments with a vapor mist (see reference numeral 106), preferably containing water, thereby at least partly precipitating said fibers 108. Consequently, the filaments or fibers 108 are at least partly precipitated before forming web or nonwoven cellulose fiber fabric 102.
(d) Collecting and precipitating said filaments or fibers 108 in order to form a web or nonwoven cellulose fiber fabric 102
(e) Removing solvent in wash line (see washing unit 180)
(f) Optionally bonding via hydro-entanglement, needle punching, etc. (see further processing unit 134)
(g) Drying and roll collection

Constituents of the nonwoven cellulose fiber fabric 102 may be bonded by merging, intermingling, hydrogen bonding, physical bonding such as hydroentanglement or needle punching, and/or chemical bonding.
In order to be further processed, the nonwoven cellulose fiber fabric 102 may be combined with one or more layers of the same and/or other materials, such as (not shown) layers of synthetic polymers, cellulosic fluff pulp, nonwoven webs of cellulose or synthetic polymer fibers, bicomponent fibers, webs of cellulose pulp, such as airlaid or wetlaid pulp, webs or fabrics of high tenacity fibers, hydrophobic materials, high performance fibers (such as temperature resistant materials or flame retardant materials), layers imparting changed mechanical properties to the final products (such as Polypropylene or Polyester layers), biodegradable materials (e.g. films, fibers or webs from Polylactic acid), and/or high bulk materials.
It is also possible to combine several distinguishable layers of nonwoven cellulose fiber fabric 102, see for instance Figure 7.
The nonwoven cellulose fiber fabric 102 may essentially consist of cellulose alone. Alternatively, the nonwoven cellulose fiber fabric 102 may comprise a mixture of cellulose and one or more other fiber materials. The nonwoven cellulose fiber fabric 102, furthermore, may comprise a bicomponent fiber material. The fiber material in the nonwoven cellulose fiber fabric 102 may at least partly comprise a modifying substance. The modifying substance may be selected from, for example, the group consisting of a polymeric resin, an inorganic resin, inorganic pigments, antibacterial products, nanoparticles, lotions, fire-retardant products, absorbency-improving additives, such as superabsorbent resins, ion-exchange resins, carbon compounds such as active carbon, graphite, carbon for electrical conductivity, X-ray contrast substances, luminescent pigments, and dye stuffs.
Concluding, the cellulose nonwoven web or nonwoven cellulose fiber fabric 102 manufactured directly from the lyocell spinning solution 104 allows access to value added web performance which is not possible via staple fiber route. This includes the possibility to form uniform lightweight webs, to manufacture microfiber products, and to manufacture continuous filaments or fibers 108 forming a web. Moreover, compared to webs from staple fibers, several manufacturing procedures are no longer required. Moreover, nonwoven cellulose fiber fabric 102 according to exemplary embodiments of the invention is biodegradable and manufactured from sustainably sourced raw material (i.e. wood pulp 110 or the like). Furthermore, it has advantages in terms of purity and absorbency. Beyond this, it has an adjustable mechanical strength, stiffness and softness. Furthermore, nonwoven cellulose fiber fabric 102 according to exemplary embodiments of the invention may be manufactured with low weight per area (for instance 10 to 30 g/m²). Very fine filaments down to a diameter of not more than 5 µm, in particular not more than 3 µm, can be manufactured with this technology. Furthermore, nonwoven cellulose fiber fabric 102 according to an exemplary embodiment of the invention may be formed with a wide range of web aesthetics, for instance in a flat crispy film-like way, in a paper-like way, or in a soft flexible textile-like way. By adapting the process parameters of the described process, it is furthermore possible to precisely adjust stiffness and mechanical rigidity or flexibility and softness of the nonwoven cellulose fiber fabric 102. This can be adjusted for instance by adjusting a number of merging positions, the number of layers, or by after-treatment (such as needle punch, hydro-entanglement and/or calendering). It is in particular possible to manufacture the nonwoven cellulose fiber fabric 102 with a relatively low basis weight of down to 10 g/m² or lower, to obtain filaments or fibers 108 with a very small diameter (for instance of down to 3 to 5 µm, or less), etc.
Figure 2, Figure 3 and Figure 4 show experimentally captured images of nonwoven cellulose fiber fabric 102 according to an exemplary embodiment of the invention in which merging of individual fibers 108 has been accomplished by a corresponding process control. The oval markers in Figure 2 to Figure 4 show such merging regions where multiple fibers 108 are integrally connected to one another. At such merging points, two or more fibers 108 may be interconnected to form an integral structure.
Figure 5 and Figure 6 show experimentally captured images of nonwoven cellulose fiber fabric 102 according to an exemplary embodiment of the invention in which swelling of fibers 108 has been accomplished, wherein Figure 5 shows the fiber fabric 102 in a dry non-swollen state and Figure 6 shows the fiber fabric 102 in a humid swollen state. The pore diameters can be measured in both states of Figure 5 and Figure 6 and can be compared to one another. When calculating an average value of 30 measurements, a decrease of the pore size by swelling of the fibers 108 in an aqueous medium up to 47% of their initial diameter could be determined.
Figure 7 shows an experimentally captured image of nonwoven cellulose fiber fabric 102 according to an exemplary embodiment of the invention in which formation of two superposed layers 200, 202 of fibers 108 has been accomplished by a corresponding process design, i.e. a serial arrangement of multiple spinnerets. The two separate, but connected layers 200, 202 are indicated by a horizontal line in Figure 7. For instance, an n-layer fabric 102 (n≥2) can be manufactured by serially arranging n spinnerets or jets 122 along the machine direction.
Specific exemplary embodiments of the invention will be described in the following in more detail:
Figure 8 shows a schematic cross sectional view of a nonwoven cellulose fiber fabric 102 according to an exemplary embodiment of the invention composed of two stacked and merged layers 200, 202 of interconnected fibers 108 having different fiber thicknesses d and D>d (see the lower two details of Figure 8). More specifically, different ones of the fibers 108 being located in the different layers 200, 202 differ concerning an averaged fiber diameter (i.e. averaged over the fibers 108 of the respective layer 200, 202). Fibers 108 of the respective layers 200, 202 are also merged at merging positions 204, compare the lower two details of Figure 8. A further detail of the interface between the layers 200, 202 is shown as well, where a merging point 204 is visible which integrally couples fibers 108 of both layers 200, 202 at the interface for increasing stability of the fabric 102 at the interface (see the upper detail of Figure 8). Additionally, different ones of the fibers 108 being located in the different layers 200, 202 are integrally connected at at least one respective merging position 204.
Merging properties may be adjusted to obtain desired properties. For instance, a number of merging points 204 per volume of fabric 102 may be adjusted separately within the respective one of the layers 200, 202 and/or between the layers 200, 202. This can be done by adjusting the coagulation properties (in particular coagulation of filaments of lyocell spinning solution 104 upstream of the fiber accommodation surface of the fiber support unit 132, coagulation of filaments of lyocell spinning solution 104 after lay down of the filaments on the fiber accommodation surface of the fiber support unit 132, etc.). The merging between the different layers 200, 202 may be adjusted so that pulling on the layers 200, 202 in opposite directions results in a separation of the fabric 102 at an interface between the different layers 200, 202. In other words, merging-based adhesion between the different layers 200, 202 may be adjusted to be smaller than merging based adhesion within a respective one of the different layers 200, 202.
The fibers 108 located in the different layers 200, 202 and being formed with different average diameter and different merging properties may be provided with tailored functionalities. Such tailored functionalities may be achieved by the different average diameters, but may also be further promoted by a respective coating or the like. Such different functionalities may for instance be a different behavior in terms of wicking, anisotropic behavior, different oil absorbing capability, different water absorbing capability, different cleanability, and/or different roughness.
The multilayer nonwoven cellulose fiber fabric 102 according to Figure 8 can be directly manufactured from lyocell spinning solution 104 using the device 100 and corresponding manufacturing method described below referring to Figure 9. Advantageously, the partial heavy metal contents of the fibers 108 of the fabric 102 according to Figure 8 are not more than 10 ppm for each individual chemical heavy metal element (i.e. not more than 10 ppm for copper, not more than 10 ppm for nickel, not more than 10 ppm for cadmium, etc.). Beyond this, an overall or entire heavy metals content of fabric 102 summed up for all heavy metal chemical elements together (i.e. in particular for Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Mo, Cd, Sn, W, Pb, Bi) is not more than 30 ppm. Apart from this, the fibers 108 have a copper content of less than 5 ppm and have a nickel content of less than 2 ppm. This is a consequence of the operating fluids (in particular lyocell spinning solution 104, coagulation fluid 106, washing liquor, gas flow 146, etc.) which are used during the manufacturing process and which may be substantially free of heavy metal sources such as copper salt. As a result of this design of the manufacturing process, the fibers 108 may be of high quality and may substantially consist of pure microfibrillar cellulose. The absence of any mentionable heavy metal impurities in the manufacturing process prevents highly undesired decomposition of involved media (in particular of the lyocell spinning solution 104) and therefore allows to obtain highly reproducible and highly pure cellulose fabric 102. More specifically, operating fluids (see in particular reference numerals 104, 106, 146, 180) used during manufacturing the fabric 102 are selected so that, and materials of a manufacturing device 100 which are in contact with at least one of the lyocell spinning solution 104 and the fibers 108 during manufacturing the fabric 102 are selected so that a heavy metal content of the fibers 108 is not more than 10 ppm for each individual chemical heavy metal element.
Figure 9 illustrates a part of a device 100 for manufacturing nonwoven cellulose fiber fabric 102 composed of two stacked layers 200, 202 of endless cellulose fibers 108 according to an exemplary embodiment of the invention. A difference between the device 100 shown in Figure 9 and the device 100 shown in Figure 1 is that the device 100 according to Figure 9 comprises two serially aligned jets 122 and respectively assigned coagulation units 128, as described above. In view of the movable fiber accommodation surface of the conveyor belt-type fiber support unit 132, the upstream jet 122 on the left-hand side of Figure 9 produces layer 202. Layer 200 is produced by the downstream jet 122 (see right hand side of Figure 9) and is attached to an upper main surface of the previously formed layer 202 so that a double layer 200, 202 of fabric 102 is obtained.
According to Figure 9, the control unit 140 (controlling the jets 122 and the coagulation units 128) is configured for adjusting process parameters so that the fibers 108 of the different layers 200, 202 differ concerning fiber diameter by more than 50% in relation to a smallest diameter (see for example Figure 8). Adjusting the fiber diameters of the fibers 108 of the layers 200, 202 by the control unit 140 may comprise adjusting an amount of coagulation fluid 106 interacting with the lyocell spinning solution 104. Additionally, the embodiment of Figure 9 adjusts the process parameters for adjusting fiber diameter by serially arranging multiple jets 122 with orifices 126 (optionally with different properties) along the movable fiber support unit 132. For instance, such different properties may be different orifice 126 diameters and or shapes, different speed of gas flow 146, different amounts of gas flow 146, and/or different gas flow 146 pressure. Although not shown in Figure 9, it is possible to further process the fibers 108 after collection on the fiber support unit 132 by hydroentangling, needling, impregnating, and/or calendering.
Still referring to the embodiment illustrated in Figure 9, one or more further nozzle bars or jets 122 may be provided and may be arranged serially along a transport direction of fiber support unit 132. The multiple jets 122 may be arranged so that further layer 200 of fibers 108 may be deposited on top of the previously formed layer 202, preferably before the coagulation or curing process of the fibers 108 of the layer 202 and/or of the layer 200 is fully completed, which may trigger merging. When properly adjusting the process parameters, this may have advantageous effects in terms of the mechanical properties of a multilayer fabric 102.
The device 100 according to Figure 9, which is configured for the manufacture of multilayer fabric 102, implements a high number of process parameters which can be used for designing shape and/or diameter or diameter distribution of the fibers 108 as well as of fiber layers 200, 202. This is the result of the serial arrangement of multiple jets 122, each of which being operable with individually adjustable process parameters.
With device 100 according to Figure 9, it is in particular possible to manufacture a fabric 102 composed of at least two layers 200, 202 (preferably more than two layers). The fibers 108 of the different layers 200, 202 may have different values of the average fiber diameter and may be formed in one continuous process. By taking this measure, a highly efficient production of the nonwoven cellulose fiber fabric 102 can be ensured, which in particular allows to transfer the obtained multilayer fabric 102 in one transport procedure to a destination for further processing.
By the defined layer separation of a multilayer fabric 102, it is also possible to later separate the multilayer fabric 102 into the different individual layers 200, 202 or into different multilayer sections. According to exemplary embodiments of the invention, both intra-layer adhesion of the fibers 108 of one layer 200, 202 as well as inter-layer adhesion of the fibers 108 between adjacent layers 200, 202 (for instance by merging and/or by intermingling or friction generating contact) may be properly and individually adjusted. A corresponding separate control for each layer 200, 202 individually may be in particular obtained when the process parameters are adjusted so that coagulation or curing of the fibers 108 of one layer 202 is already completed when the other layer 200 of fibers 108 is placed on top thereof. All this can be obtained for a fabric 102 having a very low heavy metals content due to the adjusted lack of heavy metal sources along the process line.
Figure 10 shows a schematic image of nonwoven cellulose fiber fabric 102 according to another exemplary embodiment of the invention composed of three stacked layers 202, 200, 200 with different diameters of fibers 108. According to Figure 10, an intermediate sandwich layer 200 has significantly smaller diameters of fibers 108 than the two exterior layers 200, 202 above and below.
The multilayer fabric 102 shown in Figure 10 is particularly appropriate for applications such as medical appliances, agricultural textiles, cosmetic application, etc. For instance, an active substance or a lotion may be stored in the inner layer 200 showing a high capillary action. The exterior layers 200, 202 may be designed in terms of rigidity and surface haptic. This is advantageous for cleaning and medical applications. For agricultural applications, the fiber layer design may be specifically configured in terms of evaporation properties and/or root penetration.
In another application, the multilayer fabric 102 shown in Figure 10 may be used as facial mask, industrial wipe, etc., wherein the central layer 200 may have a specifically pronounced fluid retaining capability. The cover layers 200, 202 may be configured for adjusting fluid release properties. The diameters of the fibers 108 of the respective layer 200, 200, 202 may be used as a design parameter for adjusting these functions. In particular, the multilayer fabric 102 shown in Figure 10 may be configured as a lotion delivery system.
As mentioned above, an exemplary embodiment of the invention provides a nonwoven cellulose fiber fabric 102 with a very low content with heavy metal elements. This is promoted on the one hand by the above described configuration of lyocell spinning solution 104 and other media used along the production line which are by themselves substantially heavy metal element free. Simultaneously, also the hardware configuration of the device 100 may be configured so that substantially no re-contamination of the processed lyocell spinning solution 104 and the manufactured fibers 108 with heavy metal impurities occurs along the line. Thus, a biocompatible and biodegradable nonwoven cellulose fiber fabric 102 may be obtained.
In particular, also integral interconnection of fibers 108 of the fabric 102 by the formation of merging points 204 on the basis of lyocell spinning solution 104 (rather than by a separate adhesive or binder made of one or more additional materials) contributes significantly to the purity of the manufactured fabric 102. Thus, no highly disturbing heavy metals comprising connection points of separate adhesive or binder material need to be formed as a result of the process flow described referring to Figure 1 and Figure 9. The formation of merging positions 204 between fibers 108 of the fabric 102 can be accomplished by merely bringing filaments of lyocell spinning solution 104 in direct physical contact with one another prior to coagulation, i.e. before precipitation of solid fibers 108. This allows to obtain pure cellulose fabric 102 without additional adhesive material, with a precisely adjustable (in particular a strong) inter-fiber connection, with a moderate bulk density, and with very low residual amount of heavy metal elements and compounds. Thereby, a fabric 102 can be obtained which advantageously has a low environmental impact and which is not harmful to health for a user.
By the described cellulose filament production on the basis of lyocell spinning solution 104 it can be ensured that no production related heavy metal impurities accumulate in the manufactured fabric 102. This is particularly advantageous for post processing of such fabric 102 and when a correspondingly manufactured product gets into contact with human beings or natural organisms. The opportunity to manufacture nonwoven cellulose fiber fabric 102 with low heavy metal content (in particular low copper content) by a corresponding process control allows to prevent copper-based inhibiting or even toxic effects on microorganisms. Moreover, toxicity of copper may be reinforced by other heavy metals such as Hg, Sn, Cd. Thus, not only the low copper content, but also the low entire or overall heavy metal content of the fabric 102 manufactured with the above described manufacturing method is advantageous.
Moreover, wherein biodegradable nonwoven cellulose fiber fabric 102 decomposes after use, non-biodegradable heavy metal content thereof will not decompose and will therefore accumulate. Thus, fabric 102 according to an exemplary embodiment of the invention being poor in terms of heavy metal content is particularly appropriate for biodegradation after use without mentionable ecological footprint.
According to an exemplary embodiment of the invention, not only the implemented media (in particular lyocell spinning solution 104, coagulation fluid 106, wash liquor, etc.) for manufacturing the nonwoven cellulose fiber fabric 102 are provided substantially free of heavy metal contents, but additionally also the process environment may be adjusted so as to suppress an additional contamination of the process with heavy metal contents. Due to the high chemical reactivity of the dope or lyocell spinning solution 104, all constituents of the device 100 shown in Figure 1 or Figure 9 may be configured for preventing heavy metal content impurities of these constituents to be introduced in the lyocell spinning solution 104, the manufactured fibers 108 and the manufactured fabric 102. For instance, the mentioned constituents of the device 100 may undergo a surface treatment (for instance a passivating coating) preventing that the contact surfaces of the device 100 getting in physical contact with the lyocell spinning solution 104, the fibers 108 or the fabric 102 introduce heavy metals into the manufactured goods. This may also involve a corresponding conditioning of pressurized air, air guide system, washing system, etc.
In particular an exemplary embodiment of the invention combining a heavy metal depleted fabrication of fabric 102 and the fabrication of multilayer fabric 102 allows to obtain biodegradable fabric 102 manufacturable with a high yield on an industrial scale. By the multilayer architecture of the high purity fabric 102 manufacturing method, additional design parameters for precisely adjusting various physical properties of the manufactured fabric are involved (in particular in terms of fiber diameter distribution, merging properties, shaping of the fibers 102, thickness control of fabric 102 or individual layers 200, 202 thereof, etc.).
For applications with specific haptic properties, it is possible to combine specific base properties of a fabric 102 (for instance a specific liquid management) with a softening agent applied to the fabric 102 according to an exemplary embodiment of the invention.
A significant advantage of exemplary embodiments is the capability to form a fabric 102 with multiple merging positions 204 but without the additional use of binders or adhesive material at the transition or interface between different fibers 108 or fiber regions with different physical properties.
Merging variation in the vertical or thickness direction of a fabric 102 is in particular advantageous for a fabric 102 made from endless cellulose, since such a fabric type allows to manufacture different material properties (by specific functionalizations) in a similar process parameter window of the production (for instance swelling capability, hydrophilic character, oleophilic character, wicking, fluid retention capability, etc.).
What concerns filter technology, it is thereby for instance possible to manufacture multiple-filter fabric 102 in one manufacturing process. For instance, a fabric 102 providing a pre-filter capability and a fine-filter capability may therefore be manufactured.
In an exemplary embodiment of the invention, the fabric 102 can be hence used for manufacturing a filter. In such a filter comprising the fabric 102, multiple layers 200, 202 of fibers 108 are combined for manufacturing a pre-filter and a main filter having different fiber diameters or different values of titer in the different layers 200, 202. As a result of the low copper impurities (less than 5 ppm) of such a fabric 102, it is possible to use such a filter in an environment of easily oxidizable compounds such as sulfur-II-compounds (for instance thiol carboxylic acid) or other easily oxidizable chemicals (for instance ascorbic acid). In particular in such a chemical environment, copper impurities may catalyze oxidation of the mentioned substances by molecular oxygen. In a fabric 102 according to an exemplary embodiment of the invention with low heavy metal impurities, such undesired effects are efficiently suppressed.
In another exemplary embodiment of the invention, the fabric 102 with the mentioned low heavy metal impurities can be used as a (in particular multilayer) fabric 102 specifically adapted for high temperature filters. An upper temperature limit above which such a filter cannot be used any longer is defined by a temperature at which decomposition of cellulose (in particular by separation of water) starts. It has been found that, the higher the purity of the fibers 108 of the fabric 102, the higher is the starting temperature at which decomposition of the cellulose starts. Without wishing to be bound to a specific theory, it is presently believed that heavy metal impurities may function as a parasitic catalytic substance promoting undesired cellulose decomposition at higher temperatures. By keeping the heavy metals content of the fabric 102 low according to an exemplary embodiment, filter performance can be made substantially more robust.
Moreover, it is believed that the mentioned decomposition of cellulose (which is disturbing for many different applications of fabric 102, including but not only concerning filters) can further be triggered by unconnected ends of fibers (as occurs in a high concentration in fabrics made of staple fibers). It is believed that such unconnected fiber ends may function as microscopic starting points for decomposition. By using endless fibers 108 in the heavy metal depleted nonwoven cellulose fiber fabric 102 according to an exemplary embodiment of the invention, the number of free fiber ends can be dramatically decreased (for instance less than 10,000 ends/cm³, in particular less than 5,000 ends/cm³ in a fabric with a density of 0.1 g/cm³ compared to staple fibers. Thereby, the combination of endless fibers 108 with a non-catalytic low heavy metal content provides significant improvements in terms of protection of the fabric 102 against undesired cellulose decomposition.
As mentioned above, the combination of non-catalytic heavy metal depleted fabric 102 with a multilayer architecture and intra-fiber and/or inter-fiber merging provides a sufficient number of design parameters for adjusting desired properties (for instance different fiber diameters) of the fabric 102 and in combination allows to obtain a fabric 102 which is appropriate for high temperature applications.
A nonwoven cellulose fiber fabric 102 according to an exemplary embodiment of the invention having the mentioned very low heavy metal impurities is particularly advantageous for improving the lifetime of products formed on the basis of such a fabric 102. Heavy metal impurities may have an undesired catalytic effect for decomposing cellulose, for instance by triggering oxidation, dehydration, etc. By suppressing such parasitic effects as a result of the low heavy metal impurity concentration of fabric 102 according to an exemplary embodiment of the invention, it is possible to significantly increase the lifetime of such products. This particularly holds when heat and/or light is present in an environment of the fabric-based products, which can further accelerate the mentioned cellulose decomposition processes resulting from heavy metal impurities. In view of the foregoing, the heavy metal depleted fabric 102 according to an exemplary embodiment of the invention is particularly appropriate for use with products coming into light contact during use, such as agrotextile, covers, filters, packages, and clothes.
In another exemplary embodiment of the invention, the nonwoven cellulose fiber fabric 102 is used for a biodegradable product. After biodegradation, no binder material or adhesive material remains. In particular, no significant amount of heavy metals forms part of such a biodegradable product.
According to another exemplary embodiment of the invention, pronounced acoustic wave absorbing properties of cellulose may be advantageously used and further refined. By combining different layers 200, 202 of fibers 108 with different properties (for instance in terms of fiber diameter, cross sectional shape of fibers 108 having a circular shape or deviating from a circular shape, merging properties, etc.), a fabric 102 according to an exemplary embodiment of the invention may be formed in which the acoustic wave absorbing properties of the cellulose may be refined in terms of a desired absorption frequency range and/or a selective damping strength.
According to still another exemplary embodiment of the invention, the thermally insulating properties of cellulose may be advantageously used and further refined. By combining different layers 200, 202 of fibers 108 with different properties (for instance in terms of fiber diameter, cross sectional shape of fibers 108 having a circular shape or deviating from a circular shape, merging properties, etc.), a fabric 102 according to an exemplary embodiment of the invention may be formed in which the thermal insulation properties of the cellulose may be refined. To obtain a fabric 102 according to an exemplary embodiment of the invention with a high thermal insulation, it is possible to take a provision that the cellulose fibers 108 do not become excessively wet. For instance, this may be accomplished by impregnating an exterior surface of the fabric with a hydrophobic material.
Summarizing, in particular one or more of the following adjustments may be made according to exemplary embodiments of the invention:

a low homogeneous fiber diameter may allow to obtain a high smoothness of the fabric 102
multilayer fabric 102 with low fiber diameter may allow to obtain a high fabric thickness at a low fabric density
equal absorption curves of the functionalized layers can allow to obtain a homogeneous humidity and fluid accommodation behavior, as well as a homogenous behavior in terms of fluid release
the described connection of layers 200, 202 of fabric 102 allows to design products with low linting upon layer separation
- it is also possible to differently functionalize single layers 200, 202 so that products with anisotropic properties are obtained (for instance for wicking, oil take-up, water absorption, cleanability, roughness).

Finally, it should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be capable of designing many alternative embodiments without departing from the scope of the invention as defined by the appended claims. In the claims, any reference signs placed in parentheses shall not be construed as limiting the claims. The words "comprising" and "comprises", and the like, do not exclude the presence of elements or steps other than those listed in any claim or the specification as a whole. The singular reference of an element does not exclude the plural reference of such elements and vice-versa. In a device claim enumerating several means, several of these means may be embodied by one and the same item of software or hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

A nonwoven cellulose fiber fabric (102), in particular directly manufactured from lyocell spinning solution (104), wherein the fabric (102) comprises a network of substantially endless fibers (108), and wherein a heavy metal content of the fibers (108) is not more than 10 ppm for each individual chemical heavy metal element.
The fabric (102) according to claim 1, comprising at least one of the following features:
wherein an overall heavy metal content of the fibers (108) is not more than 30 ppm;

wherein the fibers (108) have a copper content of less than 5 ppm;

wherein the fibers (108) have a nickel content of less than 2 ppm.
The fabric (102) according to claim 1 or 2, wherein at least part of the fibers (108) are integrally merged at merging positions (204).
The fabric (102) according to any of claims 1 to 3, wherein different ones of the fibers (108) are located at least partially in different distinguishable layers (200, 202).
The fabric (102) according to claim 4, wherein fibers (108) of different layers (200, 202) are integrally merged at at least one merging position (204) between the layers (200, 202).
The fabric (102) according to claim 5, comprising at least one of the following features:
wherein the merging between the different layers (200, 202) is adjusted so that pulling on the layers (200, 202) in opposite directions results in a separation of the fabric (102) at an interface between the different layers (200, 202);

wherein the merging is adjusted so that merging-based adhesion between the different layers (200, 202) is smaller than merging based adhesion within a respective one of the different layers (200, 202).
The fabric (102) according to any of claims 4 to 6, wherein an average diameter of the fibers (108) of one of the layers (200, 202) is different from an average diameter of the fibers (108) of another one of the layers (200, 202).
The fabric (102) according to any of claims 1 to 7, comprising at least one of the following features:
the fabric (102) is configured as a lotion delivery system;

wherein the fibers (108) comprise or consists of microfibrillar cellulose.
A method of manufacturing nonwoven cellulose fiber fabric (102) directly from lyocell spinning solution (104), wherein the method comprises
extruding the lyocell spinning solution (104) through at least one jet (122) of orifices (126) supported by a gas flow (146) into a coagulation fluid (106) atmosphere to thereby form substantially endless fibers (108);
collecting the fibers (108) on a fiber support unit (132) to thereby form the fabric (102);
wherein operating fluids (104, 106, 146) used during manufacturing the fabric (102) are selected so that, and materials of a manufacturing device (100) which are in contact with at least one of the lyocell spinning solution (104) and the fibers (108) during manufacturing the fabric (102) are selected so that a heavy metal content of the fibers (108) is not more than 10 ppm for each individual chemical heavy metal element.
The method according to claim 9, wherein the lyocell spinning solution (104) is essentially free of copper salt, in particular is essentially free of any heavy metal salt.
The method according to claim 9 or 10, wherein the method further comprises further processing the fibers (108) and/or the fabric (102) in situ after collection on the fiber support unit (132), in particular by at least one of the group consisting of hydro-entanglement, needle punching, impregnation, steam treatment with a pressurized steam, gas treatment with a pressurized gas, and calendering.
A device (100) for manufacturing nonwoven cellulose fiber fabric (102) directly from lyocell spinning solution (104), wherein the device (100) comprises:
at least one jet (122) of orifices (126) configured for extruding the lyocell spinning solution (104) supported by a gas flow (146);

a coagulation unit (128) configured for providing a coagulation fluid (104) atmosphere for the extruded lyocell spinning solution (104) to thereby form substantially endless fibers (108);

a fiber support unit (132) configured for collecting the fibers (108) to thereby form the fabric (102);

wherein materials of the device (100) which are in contact with at least one of the lyocell spinning solution (104) and the fibers (108) during manufacturing the fabric (102) are configured so that a heavy metal content of the fibers (108) is not more than 10 ppm for each individual chemical heavy metal element.
A method of using a nonwoven cellulose fiber fabric (102) according to any of claims 1 to 8 for at least one of the group consisting of damping acoustic waves, and thermally insulating between two spaces at different temperature levels.
A method of using a nonwoven cellulose fiber fabric (102) according to any of claims 1 to 8 for at least one of the group consisting of a wipe, a dryer sheet, a filter, a hygiene product, a medical application product, a geotextile, agrotextile, clothing, a product for building technology, an automotive product, a furnishing, an industrial product, a product related to beauty, leisure, sports or travel, and a product related to school or office.
A product or composite, comprising a fabric (102) according to any of claims 1 to 8.