阅读说明：本技术 具有增强的持水能力和低基重的纤维素纤维非织造织物 (Cellulosic fiber nonwoven fabric with enhanced water holding capacity and low basis weight ) 是由 汤姆·卡莱尔 米尔科·恩泽曼 吉塞拉·哥德哈姆 M·约翰·海赫斯特 凯瑟琳娜·迈尔 *** 于 2018-03-28 设计创作，主要内容包括：本发明描述了直接从莱赛尔纺丝溶液(104)制造的纤维素纤维非织造织物(102)。织物(102)包括基本上连续的纤维(108)的网络。织物(102)表现出至少850质量％的持水能力。此外,织物(102)每单位面积质量小于25克/平方米。本发明进一步描述了一种用于制造这种织物(102)的方法和装置、包括这种织物的产品或复合材料以及这种织物(102)的各种用途。(Cellulosic fiber nonwoven fabrics (102) made directly from lyocell spinning solution (104) are described. The fabric (102) includes a network of substantially continuous fibers (108). The fabric (102) exhibits a water holding capacity of at least 850 mass%. Further, the fabric (102) has a mass per unit area of less than 25 grams per square meter. The invention further describes a method and an apparatus for manufacturing such a fabric (102), a product or composite comprising such a fabric and various uses of such a fabric (102).)

1. A cellulose fibre nonwoven fabric (102), in particular a cellulose fibre nonwoven fabric manufactured directly from a lyocell spinning solution (104), the fabric (102) comprising:

a network of substantially continuous fibers (108), wherein

The fabric (102) exhibits a water holding capacity of at least 850 mass%, and

the fabric (102) has a mass per unit area of less than 25 grams per square meter.

2. The fabric (102) according to the preceding claim,

the fibers (108) have a copper content of less than 5ppm and/or a nickel content of less than 2 ppm.

3. The fabric (102) according to any one of the preceding claims,

the different fibers (108) are at least partially located in different distinguishable layers (200, 202), of which in particular

The fabric includes at least one of the following features:

the fibers (108) of the different layers (200, 202) are integrally connected at least one interlayer fusion location (204) between the layers (200, 202);

the different fibers (108) at least partially located in different layers (200, 202) differ in fiber diameter, in particular in average fiber diameter;

the fibers (108) of the different layers (200, 202) have the same fiber diameter, in particular substantially the same average fiber diameter;

the network of fibers (108) of different layers (200, 202) provides different functions, wherein the different functions comprise, inter alia, at least one of: different wicking, different anisotropic behavior, different optical properties, different liquid holding capacity, different cleaning capacity, different roughness, different smoothness and different mechanical properties.

4. The fabric (102) according to the preceding claim,

the fiber networks in different layers have different fusion coefficients, or

The fiber networks in the different layers have at least approximately the same fusion coefficient.

5. The fabric (102) according to any one of the preceding claims,

the mass per unit area is between 5 and 25 g/m, in particular between 8 and 20 g/m.

6. The fabric (102) according to any one of the preceding claims,

the fabric (102) exhibits a water holding capacity of at least 900 mass%, in particular at least 950 mass%, and further in particular at least 1000 mass%.

7. The fabric (102) according to any one of the preceding claims,

the fabric (102) exhibits an oil holding capacity of at least 800 mass%, in particular at least 1500 mass%, and further in particular at least 2000 mass%.

8. The fabric (102) according to any one of the preceding claims,

the fiber network includes at least one of the following features:

different portions of the same fiber (108) differ in fiber diameter such that a ratio between a maximum fiber diameter of the fiber (108) and a minimum fiber diameter of the fiber (108) is greater than 1.5;

the different fibers (108) differ in fiber diameter such that the ratio of the maximum fiber diameter of one fiber (108) to the minimum fiber diameter of the other fiber (108) is greater than 1.5.

9. The fabric (102) according to any one of the preceding claims,

the fiber network includes at least one of the following features:

at least 3%, in particular at least 5%, of the fibers (108) have a non-circular cross-sectional shape with a roundness of not more than 90%;

at least 1%, particularly at least 3%, of the fibers (108) have a non-circular cross-sectional shape with a roundness of not more than 80%, particularly not more than 70%.

10. The fabric (102) according to any one of the preceding claims,

at least a part of the fibers (108) is fused into one piece at a fusion location (204), wherein in particular the fusion coefficient of the fibers (108) is in the range of 0.1% -100%, in particular in the range between 0.2% -15%, and further in particular in the range between 0.5% -10%.

11. The fabric (102) according to any one of the preceding claims,

at least some of the individual fibres being intertwined and/or

At least one of the fiber structures is intertwined with another fiber structure.

12. A method of manufacturing a cellulosic fibre nonwoven fabric (102), in particular a fabric (102) according to any one of the preceding claims, directly from a lyocell spinning solution (104), the method comprising:

extruding a lyocell spinning solution (104) through an eductor (122) having an orifice (126) into an atmosphere of a coagulating fluid (106) with the aid of a gas stream (146) to form a substantially continuous fiber (108);

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

adjusting the process parameters of the manufacturing process such that

The fabric (102) exhibits a water holding capacity of at least 850 mass%, and

the fabric (102) has a mass per unit area of less than 25 grams per square meter.

13. An apparatus (100) for producing a cellulose fiber nonwoven fabric (102) directly from a lyocell spinning solution (104), in particular for producing a fabric according to any of the preceding claims 1 to 11, the apparatus (100) comprising

An injector (122) having an orifice (126) configured for extruding a lyocell spinning solution (104) with the aid of a gas stream (146);

a coagulation unit (128) configured for providing an atmosphere of a coagulation fluid (106) to the extruded lyocell spinning solution (104) thereby forming a substantially continuous fiber (108);

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

a control unit (140) configured for adjusting the process parameter such that

The fabric (102) exhibits a water holding capacity of at least 850 mass%, and

the fabric (102) has a mass per unit area of less than 25 grams per square meter.

14. A method of using the cellulose fiber nonwoven fabric (102) according to any one of claims 1-11, the cellulose fiber nonwoven fabric (102) being used for at least one of: a wipe; a dryer sheet; a filter; a hygiene product; a medical application product; a geotextile; an agricultural fabric; a garment; products for construction technology; automotive products; furniture; industrial products; products related to leisure, beauty, sports or travel; and products associated with schools or offices.

15. A product or composite comprising a cellulosic fiber nonwoven fabric (102) according to any one of the preceding claims 1-11.

Technical Field

The present invention relates to a cellulosic fibrous nonwoven web, a method of making a cellulosic fibrous nonwoven web, an apparatus for making a cellulosic fibrous nonwoven web, a product or composite, and a method of using a web.

Background

Lyocell (Lyocell) technology involves dissolving cellulosic wood pulp or other cellulose-based raw materials directly in a polar solvent (e.g., N-methylmorpholine N-oxide, which may also be referred to as "amine oxide" or "AO") to produce a viscous, high shear, dilute solution that can be converted into a range of useful cellulose-based materials. Commercially, this technique is used to produce a series of cellulosic staple fibers (commercially available from Lenzing AG, Lenzing, Austria, trade mark) widely used in the textile industry). Other cellulose products from lyocell technology are also used.

Cellulosic staple fibers have long been used as a component for conversion into nonwoven webs. However, modifying lyocell technology to directly produce nonwoven webs would result in properties and performance not possible with current cellulosic web products. This can be considered to be a cellulosic version of the meltblown (meltblow) and spunbond techniques widely used in the synthetic fiber industry, however, due to significant technological differences it is not possible to make the synthetic polymer technology directly applicable to lyocell.

Many studies have been carried out to develop techniques for forming cellulose webs directly from lyocell solutions (in particular WO 98/26122, WO 99/47733, WO 98/07911, US 6,197,230, WO 99/64649, WO 05/106085, EP 1358369, EP 2013390). Other techniques are disclosed in WO 07/124521a1 and WO 07/124522 a 1.

Like other cellulosic materials, cellulosic fiber nonwoven fabrics have limited liquid absorption capacity and certain contamination, which is often caused by undesirable contaminants such as heavy metal element contaminants. However, several applications of cellulose fiber nonwoven fabrics require on the one hand a large liquid absorption capacity and on the other hand a high degree of purity with only a very limited contaminant content.

Disclosure of Invention

It may be desirable to improve the water holding capacity of cellulosic fibrous nonwoven fabrics while keeping contamination of the fabrics within minimum acceptable limits.

This need may be met by the subject matter according to the independent claims. The dependent claims describe advantageous embodiments of the invention.

According to a first aspect of the present invention, there is provided a cellulosic fibre nonwoven fabric, in particular made directly from a lyocell spinning solution. The provided fabrics comprise a network of substantially continuous fibers and exhibit a water holding capacity of at least 850 mass%. Further, the fabric is provided with a mass per unit area of less than 25 grams per square meter. Thus, the mass percent water holding capacity described represents the ratio between the mass of water absorbable and the mass of fiber.

The provided fabric is based on the following concept: by using appropriate process parameters (values) for manufacturing a fabric directly from a lyocell spinning solution, it is possible to provide a non-woven cellulosic fibre fabric or web having at least an enhanced liquid-holding capacity compared to known cellulosic products. Thus, even with thinner fabrics having a lower "mass per unit area", enhanced liquid holding capacity can be achieved. For many applications, this increases the efficiency of the corresponding cellulose fiber nonwoven product or opens up new applications for the cellulose fiber nonwoven product.

According to the invention, this extraordinary water holding capacity is achieved for fabrics having a low mass per unit area. Reference to the term "mass per unit area" is also commonly referred to as "basis weight".

Fabrics having such low basis weights (i.e., basis weights less than 25 grams per square meter) and the described greater water holding capacities of at least 850 mass% are useful in a variety of applications, such as applications requiring thin nonwoven fabrics. In this context, it is found that fabrics with a large water holding capacity also generally have a large holding capacity for other liquids. This holds in particular for water-based liquids, i.e. liquids in which water is used as solvent.

It has been found that the wicking action of a nonwoven web of cellulosic fibers has a large effect on the water holding capacity. In this context, it should be appreciated that the capillary action is related to the number and size of (micro) cavities, such as voids, gaps and/or tubes formed between adjacent fibers. Such (micro) cavities provide more or less suitable accommodation for liquid particles, in particular water particles.

The water-holding capacity values mentioned relate to measurements carried out according to standard DIN 53923 (F36_3) and to a mass per unit area or basis weight of 16g/m²And 38g/m²(grams per square meter) of the fabric. In particular, the water holding capacity value relates to measurements made under standard climatic conditions as determined above.

In the context of the present application, the term "cellulose fiber nonwoven web" (which may also be denoted as cellulose filament nonwoven web) may particularly denote a web or web consisting of a plurality of substantially continuous fibers. The term "substantially continuous fibers" has in particular the meaning of filament fibers, which have a significantly longer length than conventional staple fibers. In another expression, the term "substantially continuous fibers" may especially have the meaning of a web formed of filament fibers having a significantly smaller number of fiber ends per volume than conventional staple fibers. In particular, a fabric according to an exemplary embodiment of the inventionThe continuous fibers of the article have a fiber end amount per volume of less than 10,000 ends/cm³Especially less than 5,000 ends/cm³. For example, when staple fibers are used as a substitute for cotton, they may have a length of 38mm (corresponding to the typical natural length of cotton fibers). In contrast, the substantially continuous fibers of the cellulose fiber nonwoven fabric may have a length of at least 200mm, in particular at least 1000 mm. However, those skilled in the art will appreciate the fact that even continuous cellulosic fibers may be disrupted, which may be formed by processes during and/or after fiber formation. Thus, cellulosic fiber nonwoven fabrics made from substantially continuous cellulosic fibers have a significantly lower number of fibers per mass than nonwoven fabrics made from staple fibers of the same denier. Cellulosic fiber nonwoven fabrics can be made by spinning a plurality of fibers and by attenuating (attenuating) the latter and drawing it toward a preferably moving fiber support unit. Thereby forming a three-dimensional web or web of cellulosic fibers, constituting a cellulosic fiber nonwoven fabric. The fabric may be made of cellulose as the main or sole component.

In the context of the present application, the term "lyocell spinning solution" may particularly denote a solvent (e.g. a polar solution of a material such as N-methyl-morpholine, NMMO, "amine oxide" or "AO") in which cellulose (e.g. wood pulp or other cellulose-based raw material) is dissolved. The lyocell spinning solution is a solution rather than a melt. Cellulose filaments may be produced from a lyocell spinning solution by reducing the concentration of solvent, for example by contacting the filaments with water. The process of initially forming the cellulosic fibres from the lyocell spinning solution may be described as coagulation.

In the context of the present application, the term "gas flow" may particularly denote a gas flow (e.g. air) substantially parallel to the direction of movement of the cellulose fibres or the preforms thereof (i.e. the lyocell spinning solution) during and/or after the lyocell spinning solution exits the spinneret or after it has exited the spinneret.

In the context of the present 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 is capable of diluting the lyocell spinning solution and exchanging with a solvent to the extent that cellulose fibres are formed from lyocell filaments. Such a solidified fluid may be, for example, a water mist.

In the context of the present application, the term "process parameters" may particularly denote all physical and/or chemical parameters and/or apparatus parameters of the substances and/or apparatus components used for producing the cellulose fiber nonwoven web, which parameters may have an influence on the properties of the fibers and/or the web, in particular on the fiber diameter and/or the fiber diameter distribution. These process parameters can be automatically adjusted by the control unit and/or manually adjusted by the user to adjust or adjust the properties of the fibers of the cellulosic fibrous nonwoven web. The physical parameters that may affect the properties of the fibre, in particular its diameter or diameter distribution, may be the temperature, pressure and/or density of the various media involved in the process (e.g. lyocell spinning solution, coagulation fluid, gas flow, etc.). The chemical parameters may be the concentration, amount, pH of the medium involved (e.g. lyocell spinning solution, coagulation fluid, etc.). The device parameters may be the size of the orifices and/or the distance between the orifices, the distance between the orifices and the fiber support unit, the transport speed of the fiber support unit, the provision of one or more optional in situ post-treatment units, the gas flow, etc.

The term "fiber" may particularly denote an elongated segment of material comprising cellulose, for example of substantially circular or irregular shape in cross-section, optionally intertwined with other fibers. The aspect ratio of the fibers may be greater than 10, in particular greater than 100, more in particular greater than 1000. The aspect ratio is the ratio between the length of the fiber and the diameter of the fiber. The fibers may be connected to each other by fusion (so that an integral multi-fiber structure is formed) or by friction (so that the fibers remain separated, but are weakly mechanically coupled by friction forces generated when moving the fibers in physical contact with each other), thereby forming a network. The fibers may have a substantially cylindrical shape, however they may be straight, bent (bent), kinked (knotted) or curved (bent). The fibers may be composed of a single homogeneous material (i.e., cellulose). However, the fibers may also include one or more additives. Liquid material such as water or oil may accumulate between the fibers.

According to one embodiment of the invention, the fibers have a copper content of less than 5ppm and/or have a nickel content of less than 2 ppm.

The ppm values referred to herein relate to mass (rather than volume). In addition, the heavy metal contamination of the fiber or fabric may not exceed 10ppm for each individual heavy metal element. Due to the use of lyocell spinning solution as the main component for forming continuous fibre based fabrics (especially when solvents such as N-methyl-morpholine, NMMO are involved), contamination of the fabric by heavy metals such as copper or nickel (which may cause allergic reactions in the user) may be kept to a minimum.

According to another embodiment of the invention, the different fibers are at least partially located in different distinguishable layers, and the fabric comprises in particular at least one of the following features: (a) the fibers of the different layers are integrally connected at least one interlaminar fusion location between the layers; (b) the different fibers at least partly located in different layers differ in fiber diameter, in particular in average fiber diameter; (c) the fibers of the different layers have the same fiber diameter, in particular substantially the same average fiber diameter; (d) the fiber networks of the different layers provide different functions, wherein the different functions comprise in particular at least one of the following: different wicking, different anisotropic behavior, different optical properties, different liquid holding capacity, different cleaning capacity, different roughness, different smoothness and different mechanical properties.

Herein, "different fibers are at least partially located in different distinguishable layers" may mean that the respective layers show a visible separation or interface region between the layers at least within an image captured, for example, by electron microscopy. As described in feature (a) above, the different layers may be integrally connected at least one fusion site. Thus, for example, two (or more) different layers of fabric may be formed by arranging two (or more) jets having orifices through which a lyocell spinning solution is extruded for coagulation and fibre formation in series. When this arrangement is combined with a moving fiber support unit (e.g., a conveyor belt having a fiber receiving surface), a first layer of fibers is formed on the fiber support unit by a first injector, and when the moving fiber support unit reaches the position of a second injector, the second injector forms a second layer of fibers on the first layer. The process parameters of the method may be adjusted so that a fusion point is formed between the first layer and the second layer. As already mentioned above, "fusion" may mean the integral interconnection of different fibers at the respective fusion locations, which results in the formation of an integrally connected fiber structure consisting of two separate fibers previously associated with the different layers. In particular, for example, the fibers of the second layer, which have not yet been fully solidified or solidified by coagulation during formation, may still have an outer skin or surface region in the liquid lyocell solution phase and not yet in the fully solidified solid state. When such pre-fiber structures are brought into contact with each other and then fully cured to a solid fiber state, this may result in the formation of two fused fibers at the interface between the different layers.

As stated in feature (b) above, the different fibers at least partly in different layers differ in their fiber diameter, in particular in their average fiber diameter. When the different layers of the fabric are formed of fibres having different average diameters, the mechanical properties of the different layers may be adjusted separately and differently. For example, one of the layers may be provided with rigid features by using fibers having a relatively high thickness or diameter, while the other layer may be provided with smooth or elastic features (e.g. by using fibers having a relatively small diameter). For example, a wipe may be manufactured having a rougher surface for cleaning by mechanical removal of dirt and having a smoother surface for wiping, i.e., configured for absorbing water or the like from a surface to be cleaned.

However, as described above in feature (c), the fibers of the different layers may also have the same diameter, in particular the same average diameter. In such embodiments, adjacent layers may have similar or identical physical properties. The fusion points between them may be strongly or weakly connected. The number of such fusion points per interface region may define the strength of the bond between adjacent layers. The user can easily separate the layers due to the low bonding strength. By virtue of the high bonding strength, the layers can remain permanently attached to one another.

It was found that the attachment of adjacent layers to each other within the described multilayer structure does not require any additional adhesive material, such as an adhesive. As a result, the liquid can diffuse through the layer interfaces without hindrance.

According to another embodiment of the invention, the fiber networks in the different layers have different fusion coefficients. This may help to improve the mechanical stability of the fabric, wherein the stability is in particular the stability against twisting of the fabric. Alternatively, the fiber networks in the different layers have at least approximately the same fusion coefficient. This may result in a fabric having a high degree of homogeneity, particularly in a direction perpendicular to the main plane of the layer

In particular, by varying the fusion coefficient in the height direction or z-direction perpendicular to the plane of the layers, a certain pretension can be achieved when the continuous fibers come down in contact with the fiber support unit collecting the fibers during the manufacturing of the fabric. Thus, the height-dependent distribution of the different fusion coefficients may allow to establish a high mechanical stability and to effectively prevent collapse of capillary cavities or voids formed within the fabric under pressure of adhesive forces when embedding liquid particles within the fabric. In general, high mechanical stability is a beneficial property of high liquid-holding capacity.

According to another embodiment of the invention, the mass per unit area is between 5 and 25 g/m, in particular between 8 and 20 g/m.

According to another embodiment of the invention, the fabric exhibits a water holding capacity of at least 900 mass%, in particular at least 950 mass%, and further in particular at least 1000 mass%.

This further improvement in the value of the water holding capacity of the described fabric can be achieved by a suitable choice of (the value of) the above-mentioned process parameters for the coagulation of the lyocell spinning solution. In several tests of the fabrics produced under the coagulation conditions optimized so far, the water holding capacity reached 1100 mass% or even higher.

According to another embodiment of the invention, the fabric exhibits an oil holding capacity of at least 800 mass%, in particular at least 1500 mass%, and further in particular at least 2000 mass%. Thus, the mass percentage of oil holding capacity represents the ratio between the mass of oil that can be absorbed and the mass of fiber.

To determine the oil-holding capacity (or liquid-holding capacity) of the fabric, an evaluation analysis regarding oil absorption and absorption of fatty liquids can be carried out using engine oils according to the Edana standard NWSP 010.4.R0 (15). For analysis, a fabric sample having dimensions of 10cm x 10cm can be formed by stamping. The weight of the sample was determined and then the sample was attached diagonally to the ruler by string. The sample is then placed in a container containing oil. The time required to wet the fabric with oil was measured. Subsequently, the fabric was immersed in the oil for 120 seconds. The fabric is then lifted out of the oil by lifting the ruler. After this time, the oil was allowed to drip from the fabric for 30 seconds. The weight of the fabric is determined and the oil holding capacity is calculated therefrom.

The described relatively large oil holding capacity may provide the following advantages: the described fabric can be used, for example, as a wipe, which can effectively absorb various liquids. In particular, not only water-based liquids but also oil-based liquids can be absorbed. In this context, the term "oil-based liquid" may particularly denote any liquid in which an oil is used as a solvent. Further, the term "oil-based liquid" may refer to an emulsion in which at least one component is an oil.

The volume and spacing of the active fiber surface and the gaps between adjacent fibers can be adjusted according to the adjustment of the fiber diameter and/or the intra-fiber and/or inter-fiber diameter non-uniformity and/or the absolute value of the fabric density. This has an effect on the ability of liquid to accumulate in the gap.

In more detail, the described liquid-holding capacity can be based on the following facts: a nonwoven web or fabric can be considered to represent a structure that includes cavities or voids formed between various adjacent fibers. In the original, non-saturated state of the fabric, these voids are filled with air. When the fabric absorbs liquid, the voids will fill with liquid.

According to another embodiment of the invention, the fiber network comprises at least one of the following features: (a) the fiber diameters of different portions of the same fiber are different such that the ratio between the maximum fiber diameter of the fiber and the minimum fiber diameter of the fiber is greater than 1.5; (b) the different fibers differ in fiber diameter such that the ratio of the maximum fiber diameter of one fiber to the minimum fiber diameter of the other fiber is greater than 1.5.

In the present context, the term "ratio between the maximum fiber diameter and the minimum fiber diameter is greater than 1.5" or the equivalent term "difference in fiber diameter from the minimum diameter is greater than 50%" may particularly denote that the ratio between the maximum fiber diameter and the minimum fiber diameter is multiplied by 100% and the 100% is subtracted from the obtained result, giving a value of greater than 50%. In other words, the ratio between the maximum fiber diameter and the minimum fiber diameter may be greater than 1.5.

The "difference in fiber diameters of different portions of the same fiber" as described in the above feature (a) may mean that the unevenness relating to the diameters may be a variation in the fiber inner diameter. In such embodiments, each fiber itself may exhibit fiber diameter non-uniformity. Without wishing to be bound by a particular theory, it is presently believed that when such fibers form a network in the fabric, the non-uniformity of the diameters of the respective fibers has a large effect on the capillary action, in particular increasing the number and type of cavities within the fabric, such that the water holding capacity can be adjusted.

The "difference in fiber diameter of different fibers" as described in the above feature (b) may mean that the unevenness in thickness may be variation in thickness among fibers. In such embodiments, the difference in fiber thickness between different fibers is mandatory by fiber comparison, although individual fibers may themselves exhibit uniformity or non-uniformity in thickness. Also in this case, the interaction between fibres of different diameters/thicknesses or different diameter/thickness distributions may lead to variations in the number and size of the cavities between the fibres, as described above, while the capillaries themselves have a great influence on the water holding capacity.

According to another embodiment of the invention, the fiber network comprises at least one of the following features: (a) at least 3%, particularly at least 5%, of the fibers have a non-circular cross-sectional shape with a roundness of no more than 90%; (b) at least 1%, particularly at least 3%, of the fibers have a non-circular cross-sectional shape with a roundness of not more than 80%, particularly not more than 70%.

In the present context, the term "roundness" may particularly denote the ratio between the inscribed circle and the circumscribed circle of the fiber cross-section, i.e. the maximum dimension and the minimum dimension of a circle just sufficient to fit inside the fiber cross-section to enclose or be enclosed by the fiber cross-section. To determine the roundness, a cross-section perpendicular to the extension direction of the fiber may intersect the fiber. Thus, the roundness can be expressed as a measure of how close the cross-sectional shape of each fiber approaches the cross-sectional shape of a circle having a roundness of 100%.

For example, the cross-section of the individual fibers may have an oval (in particular elliptical) shape or may have a polygonal shape. More generally, the trajectory defining the outer limits of the cross section of the fiber may be any closed plane line showing a deviation from a circle. The cross-section of each fiber may be completely circular or may have one or more sharp or rounded edges.

Illustratively, the fibers of the fabric according to this embodiment deviate significantly from the overall cylindrical shape. From a mechanical point of view, this also has the following consequences: the preferred bending direction of the fiber in the presence of mechanical loads is defined by the design of the fiber cross section. For example, where the fiber has an elliptical cross-sectional shape and the two major axes (i.e., major and minor) have different lengths, bending will occur with the minor axis predominantly as the bend line under the application of force. The bending behaviour of such a fibrous web is therefore no longer statistical and unpredictable, but on the contrary it increases the defined order of the cellulose-fibre nonwoven. Thus, by simply influencing the cross-sectional geometry of the individual fibers, defined mechanical properties of the fabric can be adjusted in a simple manner. By adjusting the deviation of some or substantially all of the fibers from the ideal circle, the mutual spreading behavior or network behavior of the fibers can also be adjusted. Furthermore, when the non-round cylindrical fibers are arranged in an ordered or partially ordered manner, a nonwoven web of cellulose fibers having anisotropic mechanical properties can be produced.

According to another embodiment of the invention, at least a part of the fibers are fused into one piece at the fusion location, wherein in particular the fusion coefficient of the fibers is in the range of 0.1% to 100%, in particular in the range between 0.2% to 15%, and further in particular in the range between 0.5% to 10%.

In the present context, the term "fusion" may particularly denote an integral interconnection of different fibers at respective fusion locations, which results in the formation of one integrally connected fiber structure consisting of a previously separated fiber preform. Fusion may be represented as a fiber-fiber connection established during the solidification of one, some or all of the fused fibers. The interconnected fibers may be firmly adhered to each other at the respective fusion sites without the need for different additional materials (e.g., separate adhesives) to form a common structure. Separation of the fused fibers may require disruption of the fiber network or portions thereof.

The fusing can be triggered by a corresponding control of the process parameters of the process for producing the cellulose fiber nonwoven. In particular, after a first contact between the filaments of the lyocell spinning solution which are not yet in the state of fibrids, the coagulation of these filaments can be triggered (or at least completed). Thus, the interaction of these filaments while still in the solution phase and then or later converting them into the solid phase by coagulation enables the fusion characteristics to be suitably adjusted. The degree of fusion is a powerful parameter that can be used to tune the properties of the fabric being manufactured.

In this respect it should be clear that the number or density of the fusion points in the fabric also influences the number and (average) size of the cavities suitable for containing water.

The fusion between the fibres can be triggered by bringing the different fibre preforms in the form of lyocell spinning solutions into direct contact with each other before coagulation. By this solidification treatment, the single materials of the fibers are collectively precipitated, thereby forming the fusion site.

The described fusion coefficient is a highly characteristic parameter of the network structure (networking) between the different fibers of a fiber network for a fabric. A fusion factor of zero corresponds to a fabric with no fusion points, i.e. completely separated fibers that interact with each other only by friction. A one hundred percent fusion factor corresponds to a fabric consisting of fused spots, i.e. fully integrated fibers forming a continuous structure such as a membrane. By adjusting the fusion coefficient, it is also possible to precisely adjust the physical properties of the respective fabric (water holding capacity described in the context of the invention described herein).

To determine the fusion coefficient (which may also be referred to as an area fusion coefficient) of the fabric, the following determination process may be performed: a square sample of the fabric can be optically analyzed. A circle is drawn around each fusion position (in particular the fusion point and/or the fusion line) of the fibres that intersect at least one diagonal of the square sample, the diameter of which must remain completely inside the square sample. The circle is sized such that the circle contains a fusion zone between the fused fibers. An arithmetic mean of the determined diameter values of the circles is calculated. The fusion coefficient is calculated as the ratio between the average diameter value and the diagonal length of the square sample and can be given as a percentage.

Depending on the specific structure, in particular on the fusion coefficients, the fusion positions may include: (a) a fusion point at which fibers are fused by point contact; (b) a fused line along which the fibres are arranged in parallel with each other over at least a part of their length to form a high-grade fibre structure. The fusion points may be point-like structures made of the same material as the interconnecting fibers. A fused line can be considered as a fusion site with an oval shaped line having a diameter that is significantly larger than the diameter of the fibers connected along the fused line. Thus, a fused line may be an extended structure connecting fibers along a length of fiber that extends parallel or side-by-side along the length of fiber.

According to another embodiment of the invention at least some of the individual fibres are entangled with each other and/or at least one fibre structure is entangled with another fibre structure. This may significantly improve the mechanical stability of the fabric.

In the context of this document, a "fibrous structure" may be any arrangement of fibers comprising at least two fibers. Thus, the fibers may be individual fibers that are at least partially in contact with each other. Alternatively or in combination, the fiber structure may also comprise at least two fibers, which are integrally connected at least one fusion site.

According to another aspect of the present invention there is provided a process for the manufacture of a cellulosic fibre nonwoven fabric, particularly a fabric as hereinbefore described, directly from a lyocell spinning solution. The provided method comprises the following steps: (a) extruding the lyocell spinning solution through an eductor having an orifice into a coagulating fluid atmosphere with the aid of a gas stream to form a substantially continuous fiber; (b) collecting the fibers on a fiber support unit, thereby forming the fabric; and (c) adjusting the process parameters of the manufacturing process such that (c1) the fabric exhibits a water holding capacity of at least 850 mass%, and (c2) the fabric has a mass per unit area of less than 25 grams per square meter.

The described method is based on the idea that, by appropriate selection or process parameters, it is possible to manufacture in an efficient and reliable manner cellulose fiber nonwoven fabrics improved in many respects as described above.

In the context of this document, an "injector with orifices" (which may for example be referred to as "arrangement of orifices") may be any structure comprising an arrangement of linearly arranged orifices.

It has also been found that the variation in diameter of the different fibres can be produced by coagulation of fibres arranged at least substantially parallel to each other. In other words, at least two different fibers initially aligned in at least approximately parallel directions can at least merge with one another (along a common merging line) so that fibers of significantly increased diameter will be produced. By controlling (the value of) the process parameters, the possibility of such fiber fusion can be selected. As a result, the ratio between the fused (coarser) fibres and the original (finer) fibres can be adjusted, for example by adjusting the distance between adjacent orifices of the jet through which the viscous lyocell spinning solution is extruded. In this respect, it should be clear that the smaller the distance, the greater the probability of fusion between the two fibers.

Furthermore, when the air promoting the coagulation process is treated separately using a turbulent coagulation fluid flow, the spatial distance between the different fibers that have not yet (fully) coagulated may be disturbed, so that the probability that two fibers meet each other en route from the ejector to the fiber support unit may be increased.

It has also been found that fusion of three or more initially separate fibers can also be achieved. As a result, even thicker fibers can be produced, so that fiber diameter variations will increase.

With regard to the correlation of "fusion" with the main properties of the fabrics described herein (i.e. water holding capacity), reference is made to the above explanatory physical theory section which illustrates the dependence of these main properties on fusion.

According to another embodiment of the present invention, there is provided an apparatus for making a cellulosic fibre nonwoven fabric directly from a lyocell spinning solution, and in particular for making a fabric as described above. The provided apparatus includes: (a) an injector having an orifice configured for extruding a lyocell spinning solution with the aid of a gas stream; (b) a coagulation unit configured to provide a coagulation fluid atmosphere to the extruded lyocell spinning solution, thereby forming a substantially continuous fiber; (c) a fiber support unit configured to collect fibers, thereby forming the fabric; and (d) a control unit configured to adjust the process parameters such that (d1) the fabric exhibits a water holding capacity of at least 850 mass%, and (d2) the fabric has a mass per unit area of less than 25 grams per square meter.

The described apparatus is based on the idea that the control unit allows to carry out the above-described method for manufacturing the above-described cellulose fiber nonwoven fabric in a reliable manner.

The cellulosic fiber nonwoven fabric according to exemplary embodiments of the present invention may also be combined (e.g., in situ or in a subsequent process) with one or more other materials to form a composite material according to exemplary embodiments of the present invention. Exemplary materials that may be combined with the fabric to form such a composite material may be selected from materials including, but not limited to, the following or combinations thereof: fluff pulp, fiber suspensions, wet-laid nonwovens, air-laid nonwovens, spunbond webs, meltblown webs, carded spunlace or needle-punched webs or other sheet-like structures made of various materials. In one embodiment, the connection between the different materials may be accomplished by (but is not limited to) one or a combination of the following methods: fusion, hydroentanglement, needling, hydrogen bonding, thermal bonding, gluing by adhesive, lamination and/or calendering.

According to another embodiment of the present invention, there is provided a method of using the cellulose fiber nonwoven fabric for wipes (wipe); a dryer sheet; a filter; a hygiene product; a medical application product; a geotextile; agrotextile (agrotextile); a garment; products for construction technology; automotive products; furniture; industrial products; products related to leisure, beauty, sports or travel; and products associated with schools or offices.

According to another aspect of the present invention there is provided a product or composite comprising a non-woven fabric of cellulose fibres as described above.

Specific uses of webs (100% cellulosic fibrous webs or webs comprising or consisting of, for example, two or more fibers, or chemically modified fibers or fibers with incorporated materials (e.g., antimicrobial materials, ion exchange materials, activated carbon, nanoparticles, emulsions, medicaments or flame retardants), or bicomponent fibers) may be as follows:

the nonwoven fabric of cellulose fibers according to exemplary embodiments of the present invention can be used to make wipes such as baby wipes, kitchen wipes, wet wipes, cosmetic wipes, sanitary wipes, medical wipes, cleaning wipes, polishing (automotive, furniture) wipes, dust wipes, industrial wipes, dust collectors, and mop wipes.

The cellulose fiber nonwoven fabric according to the exemplary embodiment of the present invention may also be used to manufacture a filter. For example, such a filter may be an air filter, HVAC, air conditioning filter, smoke filter, liquid filter, coffee filter, tea bag, coffee bag, food filter, water purification filter, blood filter, cigarette filter; cabin filters, oil filters, cartridge filters, vacuum cleaner bags, dust filters, hydraulic filters, kitchen filters, fan filters, moisture exchange filters, pollen filters, HEVAC/HEPA/ULPA filters, beer filters, milk filters, liquid coolant filters, and juice filters.

In another embodiment, the cellulosic fiber nonwoven fabric may be used in the manufacture of absorbent hygiene products. Examples thereof are acquisition layers, covers, distribution layers, absorbent covers, sanitary pads, cover sheets, back sheets, leg cuffs, flushable products, pads, care pads, handling undergarments, training pants, facial masks, cosmetic removal pads, towels, diapers, and active ingredient (e.g. fabric softeners) releasing sheets for dryers.

In another embodiment, the cellulosic fiber nonwoven fabric may be used in the manufacture of products for medical applications. For example, such medical application products may be disposable caps, surgical gowns, masks and shoe covers, wound care products, sterile packaging products, health and hygiene breathable fabric products (coverstock products), dressing materials, one way clothing, dialysis products, nasal strips, dental plate adhesives, treatment undergarments, curtains, wraps and packaging, sponges, dressings and wipes, bedding, transdermal medications, gowns, pads, surgical packs, hot packs, ostomy bag liners, securing straps, and incubator mattresses.

In another embodiment, the cellulosic fiber nonwoven fabric may be used to make geotextiles. This may involve the production of crop protection covers, capillary mats, water purification materials, irrigation control materials, asphalt mulch, soil stabilization, drainage materials, sedimentation and erosion control materials, pond liners, impregnated foundations, drainage channel liners, ground stabilization materials, pit liners, seed blankets, weed control fabrics, greenhouse sun protection materials, root bags, and biodegradable plant pots. It is also possible to use the cellulose fiber nonwoven fabric for plant foils (e.g. to provide photoprotection and/or mechanical protection to plants and/or to provide manure or seeds to plants or soil).

In another embodiment, the cellulosic fiber nonwoven fabric may be used to make garments. For example, liners, garment warmth and protection, handbag components, shoe components, belt liners, industrial footwear hats, disposable work wear, bags for garments and shoes, and warmth can be manufactured on the basis of such fabrics.

In another embodiment, the cellulosic fiber nonwoven fabric may be used in the manufacture of products for use in construction technology. Such as roof and tile underlayments, slate shingles (understating), thermal and acoustical insulation, house wrap, gypsum board facings, pipe wrap, concrete molding, foundation and ground stabilizing materials, vertical drainage, roofing shingles, roofing felts, noise reducing materials, reinforcing materials, sealing materials, and damping materials (machinery) can be made using this fabric.

In another embodiment, the cellulosic fiber nonwoven fabric may be used in the manufacture of automotive products. Examples are cabin filters, trunk liners, parcel shelves, heat shields, shelf decorations, molded hood liners, trunk floor coverings, oil filters, headliners, back-parcel shelves, decorative fabrics, airbags, sound-deadening mats, insulation, car covers, basemats, car mats, tapes, backings and tufted carpets, seat covers, door trims, needle punched carpets and car carpet backings.

Another field of application for fabrics made according to exemplary embodiments of the present invention is interior furnishings such as furniture, buildings, arm and back insulation (insulators to arms and backs), thickened mats, dust covers, linings, stitch reinforcement, upholstery materials, bedding construction, quilt backings, spring covers, mattress components, mattress covers, window coverings, wall coverings, carpet backings, light covers, mattress components, spring insulators, seals, pillow covers, and mattress covers.

In another embodiment, the cellulosic fiber nonwoven fabric may be used to make industrial products. This may involve electronics, floppy disk liners, cable insulation, abrasives, insulating tapes, conveyor belts, sound absorbing layers, air conditioners, battery separators, acid systems, slip-resistant matting detergents, food packaging, tapes, sausage casings, cheese casings, artificial leather, oil recovery bars and socks, and paper felts.

The cellulosic fiber nonwoven fabrics according to exemplary embodiments of the present invention are also suitable for use in the manufacture of leisure and travel-related products. Examples of such applications are sleeping bags, tents, luggage, handbags, shopping bags, airline headrests, CD protectors, pillow cases and sandwich packaging.

Yet another field of application of exemplary embodiments of the present invention relates to school and office products. Examples which may be mentioned are book covers, mailing envelopes, maps, logos and flags, towels and flags .

It has to be noted that embodiments of the present invention have been described with reference to different subject-matters. In particular, some embodiments have been described with reference to apparatus type claims, while other embodiments have been described with reference to method type claims (or use claims). However, a person skilled in the art will gather from the above and the following description that, unless other notified, in addition to any combination of features belonging to one type of subject-matter also any combination between features relating to different subject-matters, in particular between features of the apparatus type claims and features of the method type claims, is considered to be disclosed with this text.

The aspects defined above and further aspects of the invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.