Composite nonwoven fabric and method for manufacturing a composite nonwoven fabric
By establishing a physical mixing region between spunbond nonwoven fabric and short fibers, the problems of insufficient tensile strength, absorption performance and tactile feel in the existing technology are solved, and high-strength, biodegradable composite nonwoven fabrics are manufactured to meet the needs of the large market and reduce production costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- LENZING AG
- Filing Date
- 2021-02-24
- Publication Date
- 2026-06-16
Smart Images
Figure CN118600646B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a composite nonwoven fabric having at least one spunbond nonwoven fabric and a layer composed of bio-based biodegradable short fibers, wherein the spunbond nonwoven fabric has filaments of regenerated cellulose laid out in a random orientation and substantially continuously.
[0002] Furthermore, the present invention relates to a method for manufacturing a composite nonwoven fabric, wherein cellulose spun material is extruded into filaments through a plurality of nozzle holes of at least one spinning nozzle and the filaments are stretched along the extrusion direction, wherein the filaments are laid in a random orientation on a perforated conveying mechanism in order to form a spunbond nonwoven fabric, and wherein short fibers are added to the spunbond nonwoven fabric in order to form a composite nonwoven fabric. Background Technology
[0003] Spunbond nonwoven fabrics or nonwoven textiles are known in the prior art to be manufactured using both spunbonding and meltblown methods. In the spunbonding method (e.g., GB 2114052A or EP 3088585 A1), filaments are extruded through a nozzle and drawn and stretched by a stretching unit located below the nozzle. Conversely, in the meltblown method (e.g., US 5,080,569A, US 4,380,570 A or US 5,695,377 A), the extruded filaments are entrained and stretched by hot, rapid process air as they exit the nozzle. In both techniques, the filaments are laid out in a random orientation on a laying surface, such as a perforated conveyor belt, to form a nonwoven fabric, conveyed to a post-processing step, and finally wound into a nonwoven roll.
[0004] Spunbond nonwoven fabrics made from molten plastic can be used at concentrations up to 10 g / m² according to the methods mentioned above. 2 They are manufactured to achieve very small weight per unit area and high tensile strength within a certain range. However, such nonwoven fabrics often have too low absorbency for applications where absorbency is critical. Furthermore, these nonwoven fabrics are rarely biodegradable, or even non-biodegradable.
[0005] In contrast, prior art (US 4,755,421, WO 2015 / 000687, US 4,166,001) provides a wet-layout method for manufacturing nonwoven fabrics with high absorbency, in which a low-concentration pulp suspension is prepared and coated onto a conveyor belt. However, such nonwoven fabrics suffer from low tensile and abrasion strength. While the mechanical properties of these products can be partially improved by the use of synthetic adhesives and binders, this in turn negatively impacts biodegradability.
[0006] A large market for nonwoven fabrics exists in applications such as wiping cloths for pharmaceuticals, hygiene, cosmetics, industry, or household use. However, for wiping cloths, especially wet wiping cloths, high requirements are placed on tensile strength and absorbency to obtain reliable products. To mechanically reinforce wet-laid nonwoven fabrics, as described in US2004 / 0013859, synthetic binders and chopped short fibers based on polyethylene, polypropylene, or polyester are incorporated into the suspension to be processed. Nonwoven fabrics manufactured in this way have poor or incomplete biodegradability due to their synthetic fiber content.
[0007] To combine the mechanical stability of plastic-spunbond nonwoven fabrics with the absorbent properties of pulp, EP0333211 describes a method in which synthetic, particularly polyester- or polyolefin-based meltblown nonwoven products are fluidly bonded to short cellulose fibers or to a layer of wet-laid pulp. Further development of this method (US 5,284,703, US 5,587,225, US2009 / 0233049) allows for the manufacture of a wider range of products, particularly cheaper, high-volume products for the wipes market. Thus, in these methods, for example, by combining a modified air-layout method with meltblown technology, absorbent nonwoven products can be manufactured in which pulp fibers are uniformly distributed onto a synthetic polyolefin-fiber matrix. Such products also tolerate their incomplete biodegradability.
[0008] From a contemporary ecological perspective, not only petroleum-based short fibers but also combinations of petroleum-based spunbond nonwovens, such as those made of polyester or polypropylene, with pulp are concerning. Products manufactured for the large market, containing petroleum-based fibers or filaments, are neither fully biodegradable nor have suitable recycling methods. Composite nonwovens made of plastics and pulp are sold globally and end up in landfills, rivers, or oceans after their single use. This generates microplastics, which are absorbed into the food chain, and their impact on life is not fully anticipated. However, significant amounts of microplastics have already been generated during the use of these products, as evidenced by abrasion tests and subsequent microscopic examinations showing clear signs of material removal and fiber breakage.
[0009] Therefore, methods for producing nonwoven fabrics without a plastic component and without chemical binders are also known from existing technology (WO 2012 / 090130). Here, a layer of wet-laid pulp is bonded to a second nonwoven fabric layer of recycled cellulose fibers or cellulose filaments by means of water jet curing. However, the described process is very complex due to process control issues, as the spunbond nonwoven fabric roll must be unrolled and guided to the already produced wet-laid pulp layer via a steering mechanism. It should be noted that the cellulose spunbond nonwoven fabric can also be continuously manufactured as with conventional spunbond methods, bonded to the wet-laid pulp layer via steering rollers, and cured hydraulically; however, how the cellulose spunbond nonwoven fabric layer should be manufactured and the appearance of the apparatus used for this purpose are not described. Also untreated are the material density and bonding density of the spunbond nonwoven fabric components, which are clearly described as key to success in the prior art cited above (EP 0333211, US 5,284,703, US 5,587,225). Incorrect settings of these material density and bonding density can lead to insufficient extrusion or weak anchoring of the pulp fibers in the provided spunbond nonwoven fabric, resulting in poor interlayer bonding.
[0010] Another manufacturing method is known from US 7,432,219, in which a plastic-based spunbonding method is directly combined with a wet layup method. However, this also involves non-biodegradable and therefore non-durable solutions.
[0011] Furthermore, as known from US 4,523,350, short cellulose fibers can be processed into a fiber web using a carding machine and then into a nonwoven fabric using a curing device. However, due to the lower production speed, such methods or equipment are significantly less efficient in terms of production capacity than spunbond and wet-layout equipment. The short cellulose fibers are dried and compressed into bundles during their manufacturing process, mechanically opened in subsequent nonwoven fabric production, re-wetted by water jet curing, and then dried again as a nonwoven fabric. This process deserves further investigation from a global energy conservation perspective. To reduce raw material and drying costs and thereby enable the production of competitive nonwoven products for the large market, such as baby wipes or hygiene wipes, carded nonwoven fabrics are typically made from blends of polyester and viscose fibers. The high proportion of petroleum-based fibers, coupled with their lack of biodegradability, further contributes to the global microplastic problem.
[0012] It is also known from the prior art that spunbond nonwoven fabrics of cellulose are manufactured according to spunbond technology (e.g., US 8,366,988 A) and meltblown technology (e.g., US 6,358,461 A and US 6,306,334 A). Here, lyocell spun material is extruded and stretched according to known spunbond or meltblown methods. However, before being laid into a nonwoven fabric, the filaments are additionally contacted with a coagulant to regenerate the cellulose and produce shape-stable filaments. Finally, the wet filaments are laid into a nonwoven fabric in a random orientation. However, these methods rarely involve the manufacture of thermoplastic spunbond nonwoven fabrics according to conventional spunbond or meltblown methods as described at the beginning. Because the lyocell spun material is a solution with a cellulose content of 7-14%, more solvent is extruded during the manufacture of the spunbond nonwoven fabric, in addition to the cellulose forming the fibers; this solvent is extracted from the nonwoven fabric and recovered in subsequent washing. The compressed air consumption of all lyocell-based spunbond nonwoven fabric methods is significantly higher than that of thermoplastic melt-based spunbond nonwoven fabric methods due to the greatly reduced solids content. To achieve similar productivity to thermoplastic spunbond methods, significantly larger mass flow movements and greater air and energy are required to process lyocell spunbond nonwoven fabrics. Due to the increased energy consumption, the use of such products, with their very fine fiber diameter, is suitable for specialized applications in filtration and hygiene, or for high-priced wipes, but thus falls far short of meeting the demand for inexpensive, pure cellulose, and biodegradable nonwoven fabrics for the broader market, such as baby wipes, household wipes, and hygiene and industrial applications.
[0013] Therefore, existing technologies do not provide a satisfactory solution for manufacturing biodegradable, inexpensive nonwoven fabrics with good tensile strength, absorption and cleaning properties, and a feel that matches the intended use. Summary of the Invention
[0014] Therefore, the objective of this invention is to provide a fully biodegradable composite nonwoven fabric of the type mentioned at the beginning, which has high stability and tensile strength, as well as good absorption and tactile properties, and can be manufactured at low cost.
[0015] The present invention solves the proposed task by having the composite nonwoven fabric having at least one mixing region in which the filaments and staple fibers of the spunbond nonwoven fabric are physically connected to each other.
[0016] It has been surprisingly discovered that by incorporating a mixing region within the composite nonwoven fabric, a particularly reliable and durable bond can be established between the spunbond nonwoven fabric and the staple fibers. This is especially true when no additional adhesive is used for the bond between the filaments and staple fibers of the spunbond nonwoven fabric. In the mixing region, the filaments and staple fibers of the spunbond nonwoven fabric exist in a physically mixed manner, and are therefore able to be physically bonded to each other, especially without the presence of an adhesive. The physical bond between the filaments and staple fibers of the spunbond nonwoven fabric can be formed at least partially through hydrogen bonding, mechanical hooking or looping, friction, etc. In this way, a material-locked bond can be formed between the spunbond nonwoven fabric and the staple fibers, a bond that cannot be easily loosened again without damage.
[0017] Physical mixing between spunbond nonwoven fabrics and short fibers can be achieved, for example, by loading a suspension of short fibers onto the spunbond nonwoven fabric while it is still wet. This allows the filaments and short fibers of the spunbond nonwoven fabric to interpenetrate and thus establish the mixing region.
[0018] Therefore, the composite nonwoven fabric according to the invention is a purely bio-based and fully biodegradable nonwoven fabric. Thus, the invention contributes to preventing environmental pollution. Furthermore, the composite nonwoven fabric exhibits high strength due to the physical mixing or bonding between the spunbond nonwoven fabric and short fibers, as the spunbond nonwoven fabric stabilizes the layer composed of short fibers with typically high strength. Moreover, this stability is surprisingly achieved without adversely affecting the feel of the composite nonwoven fabric. Although composite nonwoven fabrics with adhesives generally have high rigidity, the composite nonwoven fabric according to the invention provides a softer and more flexible composite nonwoven fabric than those of the prior art. Furthermore, the purely bio-based and fully biodegradable composite nonwoven fabric has high absorbency and can be manufactured resource-efficiently.
[0019] In the context of this invention, bio-based fibers refer to natural fibers produced from renewable raw materials and bio-based plastic fibers. The only difference is that biodegradable plastic fibers are not of biological origin and can be made from petroleum-based raw materials. Within the scope of this invention, the concept of "bio-based fibers" specifically excludes the presence of a petroleum-based component in these fibers.
[0020] Within the scope of this invention, biodegradable fiber, in relation to plastic fiber, means fiber that is considered fully compostable according to the guidelines for biodegradable plastics in European Standard EN 13432.
[0021] If the short fibers are cellulose short fibers, the composite nonwoven fabric according to the invention can have a cellulose content of at least 93% (by weight) in an absolutely dry (“atro”) state (i.e., without water), depending on the cellulose short fibers used. Here, residual content can form substances naturally present in pulp, such as lignin, and unavoidable impurities. Such a composite nonwoven fabric has very good and complete biodegradability. Preferably, the absolutely dry composite nonwoven fabric can have a cellulose content of at least 95% (by weight), particularly preferably at least 97% (by weight).
[0022] Advantageously, the composite nonwoven fabric can have cellulose filaments ranging from 10% to 99% by weight and staple fibers ranging from 1% to 90% by weight, typical of spunbond nonwoven fabrics. The composition according to the invention particularly ensures a composite nonwoven fabric with good bonding or high strength between the filaments and staple fibers. Here, the composite nonwoven fabric preferably has cellulose filaments ranging from 15% to 95% by weight, particularly preferably from 20% to 90% by weight, and staple fibers ranging from 5% to 85% by weight, particularly preferably from 10% to 80% by weight.
[0023] If the composite nonwoven fabric is substantially free of non-natural, especially synthetic, adhesives found in wood, it can provide a composite nonwoven fabric with a particularly advantageous feel, high softness, and flexibility. Such adhesive-free composite nonwoven fabrics according to the invention are particularly well-suited for a variety of applications, such as skin-friendly hygiene products. Conversely, composite nonwoven fabrics containing adhesives may have very high stiffness and low softness, thereby limiting the range of applications for such products.
[0024] As bio-based biodegradable short fibers, all types of chopped cellulose fibers, such as natural cellulose fibers, viscose fibers, modal fibers, lyocell fibers, or cuprammonium fibers, as well as chemically modified cellulose fibers, can be used for the composite nonwoven fabrics according to the present invention. Furthermore, all types of fibers composed of wood-containing pulp, such as mechanically decomposed pulp or wood pulp, such as MP (mechanical pulp), TMP (thermo-mechanical pulp), CTMP (chemo-thermo-mechanical pulp), etc., are suitable as short fibers. In addition, the short fibers can be made from all types of wood-free pulp, such as chemically decomposed pulp CP (chemical pulp), according to nitrite methods, sulfate methods, or other methods. Furthermore, all types of pulp obtained from wood or other plants, such as grass, bamboo, algae, cotton or cottonseed lint, hemp, flax, starch-based fibers, etc., are also possible as short fibers. Furthermore, all types of pulp or recycled cellulose fibers made from recycled fabrics or nonwoven fabrics can also be used as short fibers.
[0025] As an alternative, starch fiber is also suitable as a bio-based, biodegradable short fiber for use in composite nonwoven fabrics according to the present invention.
[0026] If the short fibers have a length between 0.5 mm and 15 mm, a particularly uniform composite nonwoven fabric can be provided. Shorter fibers can no longer be reliably retained in the composite nonwoven fabric, while longer fibers may result in an uneven product. The length of the short fibers is particularly preferably between 1 and 12 mm.
[0027] Furthermore, the composite nonwoven fabric can include non-fibrous functional additives, such as activated carbon, superabsorbents, particulate dyes, and fillers (clay, ground nonwoven fabric, or wood waste). Thus, the composite nonwoven fabric can be equipped with specific additional properties, such as high water absorption.
[0028] Furthermore, before or after drying, the nonwoven fabric can be equipped with auxiliaries that alter product properties or facilitate processing, such as polishing agents or antistatic agents.
[0029] The nonwoven fabric according to the invention can be obtained, in particular, by a method according to any one of claims 8 to 17. If the nonwoven fabric is manufactured according to a method according to the invention as described in any one of claims 8 to 17, the specific properties of the nonwoven fabric are obtained by the method steps described below.
[0030] Furthermore, the objective of this invention is to provide a simple and reliable method of the type mentioned at the beginning for manufacturing composite nonwoven fabrics according to any one of claims 1 to 7.
[0031] The task is addressed methodically by loading short fibers onto the filaments of the spunbond nonwoven fabric while it is still undried.
[0032] In the method, cellulose spun material is extruded into filaments through multiple nozzle orifices of at least one spinning nozzle, and the filaments are stretched along the extrusion direction, wherein the filaments are laid in a random orientation on a perforated conveying mechanism to form a spunbond nonwoven fabric. To form a composite nonwoven fabric, short fibers are added to the spunbond nonwoven fabric in a further step.
[0033] Surprisingly, it has been shown that if short fibers are loaded onto the spunbond nonwoven fabric while it is still undried, i.e., while the filaments of the spunbond nonwoven fabric are still strongly expanded, it is possible to provide a composite nonwoven fabric according to the invention having a mixing region between the filaments and short fibers of the spunbond nonwoven fabric. Due to the softness and deformability of the undried spunbond nonwoven fabric and the weaker bond between the filaments, interpenetration between the filaments and short fibers of the spunbond nonwoven fabric is possible, thereby establishing the mixing region in the composite nonwoven fabric. During the subsequent drying process, hydrogen bonds can be formed between the spunbond nonwoven fabric filaments and the short fibers, ensuring a strong bond and high strength in the composite nonwoven fabric, which is conversely impossible in composite nonwoven fabrics made of thermoplastic nonwoven fabrics and pulp fibers (such as those described in WO 2012 / 090130).
[0034] Therefore, according to this method, it is possible to obtain a material with a concentration exceeding 10 g / m³. 2 A fully biodegradable composite nonwoven fabric per unit area weight. Depending on the positioning of the short fibers and the parameters of the water jet curing that may be added, it is possible to obtain composite nonwoven fabrics in which either a layered structure caused by the process can be identified or the added short fibers are uniformly distributed within the thickness range of the composite nonwoven fabric.
[0035] By loading a suspension of short fibers onto the filaments of the spunbond nonwoven fabric while it is still undried, a particularly simple and reliable method for manufacturing composite nonwoven fabrics can be provided. The short fibers can be easily suspended in an aqueous transport medium, particularly an aqueous solution or water, and therefore can be readily applied to the resulting spunbond nonwoven fabric.
[0036] Preferably, the suspension contains between 0.01% (by weight) and 2.00% (by weight) of short fibers. This prevents transport problems of the suspension, particularly due to blockages in pipes or nozzles. Furthermore, it has been proven that loading such a small amount of short fibers onto the spunbond nonwoven fabric is sufficient to ensure the desired loading of the spunbond nonwoven fabric with the defined amount of short fibers. Therefore, the reliability of the method can be further improved.
[0037] Advantageously, a suspension of short fibers can be loaded onto the filaments of the spunbond nonwoven fabric during washing. Therefore, the short fibers can be directly suspended in the washing solution or washing water, or the suspension can be used as the washing solution in the washing mechanism, thereby integrating the loading of short fibers onto the spunbond nonwoven fabric into common spunbond nonwoven fabric washing equipment. Thus, a particularly economical method can be provided.
[0038] As an alternative to or supplement to the washing method described above, a suspension can also be applied to the filaments of the spunbond nonwoven fabric during its formation. Therefore, for example, the suspension can be applied directly to the newly formed spunbond nonwoven fabric or to newly extruded filaments.
[0039] By loading an airflow containing short fibers onto the filaments of the spunbond nonwoven fabric while it is still undried, a particularly simple and versatile method for manufacturing composite nonwoven fabrics can be provided. The provision of the airflow allows for easy and uniform distribution of the short fibers. Furthermore, the airflow containing short fibers can be reliably introduced at multiple locations within the method, enabling particularly simple processing.
[0040] Therefore, after the filament is extruded from the spinning nozzle, a stretching airflow is applied to it for stretching. Here, the short fibers can be easily mixed into the stretching airflow, thus loading the short fibers into the still-dry spunbond nonwoven fabric filament. Therefore, this method can be technically easily implemented in existing equipment for manufacturing cellulose spunbond nonwoven fabrics without costly modifications.
[0041] After loading short fibers onto the filaments, the composite nonwoven fabric can be subjected to at least one additional processing step. Here, the composite nonwoven fabric can be subjected to washing, for example, to remove the solvent from the spunbond nonwoven fabric of cellulose.
[0042] Furthermore, the composite nonwoven fabric can be subjected to water jet curing in a single processing step, in which the composite nonwoven fabric is additionally cured by (high-pressure) water jets. This water jet curing also helps to improve the physical mixing of the filaments and staple fibers in the mixing region of the composite nonwoven fabric and thus improves the integration of the composite nonwoven fabric.
[0043] Furthermore, the composite nonwoven fabric can be subjected to hydro-emossing or water-jet perforation in a single processing step. Here, patterns, three-dimensional structures, and perforations can be incorporated into the composite nonwoven fabric.
[0044] After washing or water jet curing, the composite nonwoven fabric can also be dried in another processing step to remove residual moisture from the composite nonwoven fabric.
[0045] In optional processing steps, the composite nonwoven fabric can also be subjected to a crease process, thereby giving the composite nonwoven fabric a crease structure.
[0046] If cellulose spun material is extruded into filaments through multiple nozzle orifices of at least one second spinning nozzle and the filaments are stretched along the extrusion direction, wherein the filaments of the second spinning nozzle are randomly oriented and laid on top of a short-fiber-loaded spunbond nonwoven fabric on a conveying mechanism to form a second spunbond nonwoven fabric in a composite nonwoven fabric, a reliable method for manufacturing multilayer composite nonwoven fabrics can be provided. This allows a second cellulose spunbond nonwoven fabric to be laid on a first spunbond nonwoven fabric that has already been formed, the first spunbond nonwoven fabric having short fibers and forming a mixing region with the short fibers.
[0047] In this context, the second cellulose spunbond nonwoven fabric is preferably applied directly onto a layer composed of short fibers and thus forms a purely physical bond with that layer. Preferably, the second cellulose spunbond nonwoven fabric can have different internal and structural properties from the first spunbond nonwoven fabric, namely, particularly different weight per unit area, different air permeability, different filament diameter, etc.
[0048] Furthermore, a second layer composed of short fibers can be applied to the spunbond nonwoven fabric of the second cellulose while it is still damp. This second layer and the second spunbond nonwoven fabric form a second mixing region, in which the filaments of the second spunbond nonwoven fabric and the short fibers of the second layer are physically mixed. Refer to the above description for this. The short fibers of the second layer can also be different from those of the first layer, so that composite nonwoven fabrics with a particularly wide range of applications can be manufactured.
[0049] In the same manner as described above for the second spunbond nonwoven fabric and the second layer composed of short fibers, third and additional cellulose spunbond nonwoven fabrics or layers composed of short fibers can also be applied to the already formed composite nonwoven fabric.
[0050] The method according to the invention is particularly advantageous for manufacturing composite nonwovens having spunbond nonwoven fabrics composed of cellulose spun yarns made of lyocell spinning material. Here, the lyocell spinning material is a solution of cellulose in a direct solvent.
[0051] The direct solvent can preferably be an oxidized tertiary amine in an aqueous solution, preferably N-methylmorpholine-N-oxide (NMMO), or an ionic liquid in which cellulose can be dissolved without chemical derivatization.
[0052] The cellulose content in the spinning material can be between 4% and 17%, preferably between 5% and 15%, and particularly preferably between 6% and 14%.
[0053] Furthermore, if the filaments extruded from the spinning nozzle are at least partially condensed, the internal structure of the spunbond nonwoven fabric can be reliably controlled. For this purpose, a water-containing condensing liquid can preferably be applied to the filaments, preferably in the form of a liquid, gas, mist, steam, etc.
[0054] If NMMO is used as a direct solvent in the lyocell spinning material, the coagulant can be a mixture of completely desalinated water and 0% (by weight) to 40% (by weight) NMMO, preferably 10% (by weight) to 30% (by weight) NMMO, and particularly preferably 15% (by weight) to 25% (by weight) NMMO. Here, particularly reliable coagulation of the extruded filaments can be achieved.
[0055] The method according to the invention can be implemented by an apparatus for manufacturing composite nonwoven fabrics, wherein the apparatus comprises: a spinning material preparation mechanism for preparing cellulose spinning material; at least one spunbond nonwoven fabric apparatus for manufacturing cellulose spunbond nonwoven fabrics composed of spinning material, wherein the spunbond nonwoven fabric apparatus comprises at least one spinning nozzle for extruding the spinning material into filaments, at least one condensation system for at least partially condensing the filaments, and a conveying mechanism for laying the filaments and forming the spunbond nonwoven fabric; a washing mechanism, an optional water jet curing mechanism, a dryer, an optional crepe mechanism, and a winding machine. Furthermore, according to the invention, the apparatus comprises a wet lay-up mechanism or a dry lay-up mechanism for loading short fibers into the cellulose spunbond nonwoven fabric, wherein the wet lay-up mechanism or dry lay-up mechanism for short fibers is disposed between two spunbond nonwoven fabric apparatuses and / or disposed before, within, and / or at the end of the washing mechanism. Attached Figure Description
[0056] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Wherein:
[0057] Figure 1 A schematic diagram of a method for manufacturing composite nonwoven fabrics according to the invention, according to a first embodiment of a variant, is shown.
[0058] Figure 2 A schematic diagram of a method for manufacturing composite nonwoven fabrics according to the invention, according to a second embodiment of the variant, is shown.
[0059] Figure 3 A schematic diagram of a method for manufacturing composite nonwoven fabrics according to the invention, according to a third embodiment of the variant, is shown.
[0060] Figure 4 Electron microscope images of the first composite nonwoven fabric according to the invention are shown, and
[0061] Figure 5 An electron microscope image of the second composite nonwoven fabric according to the present invention is shown. Detailed Implementation
[0062] Figure 1A method 100 for manufacturing a composite nonwoven fabric 1 according to the invention and an apparatus 200 for carrying out the method 100 are shown, according to a first embodiment of the invention. In the first method step, a spun material 2 is generated from a cellulose raw material and fed to the spinning nozzle 3 of the apparatus 200. The cellulose raw material used to prepare the spun material 2 (the preparation of which is not shown in detail in the figure) can here be a pulp (Zellstoff) suitable for preparing lyocell fibers, composed of wood or other plant materials. However, it is also conceivable that the cellulose raw material is at least partially composed of production waste or recycled fabric from spunbond nonwoven fabric production. The spun material 2 here is a solution of cellulose in NMMO and water, wherein the cellulose content in the spun material 2 is between 3% (by weight) and 17% (by weight).
[0063] Then, in the next step, the spun material 2 is extruded into filaments 4 through multiple nozzle holes of the spinning nozzle 3. The extruded filaments 4 are then accelerated and stretched in a stretching airflow along the extrusion direction, but this is not shown in detail in the accompanying drawings.
[0064] In one embodiment, the stretching airflow can be discharged between the nozzle orifices of the spinning nozzle 3. In another embodiment, the stretching airflow can alternatively be discharged around the nozzle orifices. However, this is not shown in detail in the accompanying drawings. Such a spinning nozzle 3 having a stretching mechanism for generating the stretching airflow is known from the prior art (US 3,825,380 A, US 4,380,570 A, WO 2019 / 068764 A1).
[0065] Furthermore, in the preferred embodiment shown, a coagulant from the coagulation mechanism 5 is loaded onto the extruded and stretched filaments 4. This coagulant is typically water or an aqueous solution in the form of a liquid, mist, or vapor. Through contact between the filaments 4 and the coagulant, the filaments 4 are at least partially coagulated or regenerated, which in particular reduces adhesion between the individual extruded filaments 4.
[0066] The stretched and at least partially condensed filaments 4 are then laid in a random orientation on the laying rack 6 of the conveying mechanism 7 to form a spunbond nonwoven fabric 8 of cellulose.
[0067] After formation, the spunbond nonwoven fabric 8 is guided through the washing mechanism 10 by the conveyor belt 9, where it is washed to remove solvent residues, i.e., NMMO contained in the spinning material 2. In a preferred embodiment, the washing mechanism 10 is a multi-stage countercurrent washing mechanism with multiple washing stages 11, wherein fresh washing solution 12 is conveyed to the last stage and the increasingly consumed washing solution of each washing stage 11 is continuously conveyed to the preceding washing stages 11.
[0068] Following the washing unit 10, the spunbond nonwoven fabric 8 is guided through the wet lay-up unit 13, where short cellulose fibers 14 are loaded onto the still-dry spunbond nonwoven fabric 8. These short fibers 14 are in a suspension 15, which is applied or sprayed onto the spunbond nonwoven fabric 8. Here, the suspension 15 has a content of short fibers 14 between 0.01% and 2.00% (by weight). By providing a separate wet lay-up unit 13 in the method 100 or apparatus 200, the operation of the short fiber conveying process, independent of the surrounding spunbond nonwoven fabric production, can be ensured.
[0069] During the application of the suspension 15 containing short fibers 14 to the still undried spunbond nonwoven fabric 8, a layer of short fibers 14 is formed on the surface of the spunbond nonwoven fabric 8, thereby forming a composite nonwoven fabric 1. Furthermore, a mixing region is formed in the composite nonwoven fabric in which the filaments and short fibers 14 of the spunbond nonwoven fabric 8 are present in a purely physical mixture and thus bonded together without chemical reaction.
[0070] Following the wet lay-up mechanism 13, the composite nonwoven fabric 1 is then subjected to water jet curing 16 in the next step. During this water jet curing 16, further bonding is performed between the spunbond nonwoven fabric 8 and the layer composed of short fibers 14, wherein the physical bond between the filaments of the spunbond nonwoven fabric 8 and the short fibers 14 is further enhanced through mixing, especially through hooking, looping, static friction, etc.
[0071] In order to finally remove residual moisture from the composite nonwoven fabric 1 and obtain a composite nonwoven fabric 1 ready for packaging, the composite nonwoven fabric 1 is subjected to drying 17 immediately after water jet curing 16.
[0072] Finally, the method 200 concludes with optional winding 18 and / or packaging of the finished composite nonwoven fabric 1.
[0073] Figure 2A second implementation variation of the method 101 or apparatus 201 according to the invention is shown as an alternative. Here, relative to... Figure 1 The embodiment shown in the figure does not deliver the suspension 15 containing short fibers 14 to a separate wet-laying mechanism 13. Instead, the short fibers 14 of the washing solution 12 are delivered to at least one washing stage 11 of the washing mechanism 10, preferably the most recent washing stage 11, so that the spunbond nonwoven fabric 8 is washed and the short fibers 14 are loaded thereon during the washing process 10. For other features, see the section on... Figure 1 Explanation.
[0074] This forms the technically simplest and also the most economical implementation variant of the invention, since it is only necessary to modify the washing mechanism 10 of the existing spunbond nonwoven fabric equipment so that one or more of the existing washing stages 11, in addition to their original function of uniformly distributing and coating the washing solution 12, are also used to load the spunbond nonwoven fabric 8 with a suspension 15 composed of short fibers 14.
[0075] Here, the suspension 15 has short fibers 14 with a concentration range between 0.01% (by weight) and 2.00% (by weight) and a fiber length of 0.5 mm to 20 mm. In another embodiment, not shown in the figures, the short fibers 14 can also be mechanically fibrillated fibers or pulp fibers, wherein a fine grinding mill is additionally required for fibrillating the short fibers.
[0076] The suspension 15 is preferably formed by suspending the short fibers 14 in fresh water. Preferably, the suspension 15 is applied to the spunbond nonwoven fabric 8 only within the last two washing stages 11, so as to minimize the impact on the concentration distribution of the solvent in the washing solution throughout the washing unit 10 and thereby avoid as much as possible the additional technical requirements and increased operating costs associated with the treatment or concentration of solvent-containing washing water. Furthermore, by supplying the suspension 15 to the washing unit 10, the demand for the washing solution 12 in the washing unit 10 can be reduced to a corresponding extent.
[0077] In another way Figure 2 In the embodiment variant shown in dashed lines, a second spinning nozzle 23 can be provided after the first spinning nozzle 3, through which the spun material 2 is also extruded into filaments 24. Here, the filaments 24 are laid on top of the first spunbond nonwoven fabric 8 on the conveying mechanism 7 to form the second spunbond nonwoven fabric.
[0078] Here, the suspension 15 containing short fibers 14 is applied between the first spinning nozzle 3 and the second spinning nozzle 23 onto the first spunbond nonwoven fabric 8 to create a layer composed of short fibers 14. The second spunbond nonwoven fabric is then laid directly onto the layer 14 composed of short fibers, thereby forming a multilayer composite nonwoven fabric 1 consisting of a spunbond nonwoven fabric 8 having multiple cellulose fibers and short fibers 14. Here, as described above, it is possible to optionally add additional short fibers 14 to the composite nonwoven fabric 10 in the washing mechanism 10.
[0079] In another implementation variation, the multilayer composite nonwoven fabric 1 is treated in a subsequent water jet curing mechanism 16 such that the layer structure consisting of alternating spunbond nonwoven fabric 8 and short fibers 14 is as indistinguishable as possible, and thus a larger mixing region is formed in the composite nonwoven fabric 1.
[0080] Therefore, compared with the prior art, significant savings in energy and fresh water requirements are achieved for all the foregoing embodiments of methods 100 and 101 according to the present invention, because
[0081] a) Using a spunbond nonwoven fabric 8 that is already wet and has never been dried, and by adding short fibers 14 in the form of a suspension 15, the substrate that has not been dried is made wet again.
[0082] b) Compared to spunbond nonwoven fabrics with an equal amount of undried cellulose, the addition of 14 wet short fibers per unit mass of cellulose results in less water being added to the still-wet nonwoven fabric product.
[0083] c) It can reduce the demand for washing solution 12 in washing unit 10 by the amount of water delivered as suspension 15, and
[0084] d) Wastewater from water jet solidification 16 can be used as fresh water for washing unit 10 or for preparing suspension 15.
[0085] Furthermore, in another implementation variation, the equipment costs of method 101 can be further simplified by having the water jet curing 16 performed together with washing 10 on conveyor belt 9. Here, the latter can additionally have a three-dimensional embossed structure that can be transferred to the spunbond nonwoven fabric by water jet treatment.
[0086] Figure 3 A third embodiment of the method 102 and apparatus 202 according to the invention is shown. Here, in conjunction with... Figure 1 and 2The illustrated variant differs in that the short fibers 14 are not applied to the spunbond nonwoven fabric 8 in the form of a suspension 15, but rather in the form of an airflow 26 using an air-layout technique. For other features of method 102, refer to the section on... Figure 1 and Figure 2 Explanation.
[0087] The airflow 26 containing short fibers 14 can be delivered toward the spunbond nonwoven fabric 8 between the two spinning nozzles 3, 23 and before, within and / or after the washing mechanism 10.
[0088] In order to achieve uniform distribution of the short fibers 14 in the airflow 26 and to transport the short fibers 14 all the way to the application position, a special unit is provided for making fiber openings and for transporting the short fibers 14; however, the special unit is not shown in detail in the accompanying drawings.
[0089] In another embodiment, not shown in detail in the accompanying drawings, the short fibers 14 can be directly fed to the stretching mechanism in the spinning nozzles 3, 23, and thus the stretching airflow directly impacts the filaments 4 of the spunbond nonwoven fabric 8. Here, the short fibers 14 are directly mixed with the filaments 4 in the spunbond nonwoven fabric, thereby providing a mixing region extending over the entire thickness of the composite nonwoven fabric 1. For this purpose, in one embodiment, a secondary airflow containing the short fibers 14 can be introduced, for example, below the spinning nozzles 3, 23, thereby merging the secondary airflow with the stretching airflow to load the short fibers 14 onto the filaments 4.
[0090] In another embodiment, not shown in the accompanying drawings, a multilayer spunbond nonwoven fabric 8 is manufactured using two sequentially arranged spinning nozzles 3, 23. However, it is separated into two spunbond nonwoven fabric layers before the application of short fibers 14, wherein the short fibers 14 are subsequently added between the two spunbond nonwoven fabric layers (either as a suspension 15 or dried in an air stream 26). The two spunbond nonwoven fabric layers are then joined together, and the resulting composite nonwoven fabric 1 is cured in a water jet curing mechanism 16.
[0091] In order to ensure the complete biodegradability of the composite nonwoven fabric 1 according to the invention, the short cellulose fibers added by means of the above-described implementation of the variant are composed only of industrially prepared pulp, pulp recovered from a recycling process, chopped cellulose fibers, natural cellulose fibers, or all conceivable combinations of these material groups.
[0092] exist Figure 4 and 5Electron microscope images of composite nonwoven fabrics 51 and 61 manufactured according to the present invention are shown.
[0093] Figure 4 A composite nonwoven fabric 51 is shown in which a limited mixing region 56 is formed between a layer 52 composed of short fibers 53 (in this case, pulp fibers) and a spunbond nonwoven fabric 54 of cellulose (lyocell spunbond nonwoven fabric). In the mixing region 56, the filaments 55 of the spunbond nonwoven fabric 54 are physically mixed with the short fibers 53.
[0094] Figure 5 A composite nonwoven fabric 61 is shown, which no longer has a visible layered structure. Here, the cellulose spunbond nonwoven fabric 64 (lyocell spunbond nonwoven fabric) penetrates substantially completely through the layer 62 composed of short fibers 63 (pulp fibers). The mixing region 66 thus extends over the entire thickness of the composite nonwoven fabric 61. The short fibers 63 are therefore uniformly distributed on the composite nonwoven fabric 61.
[0095] Example
[0096] The advantages of the present invention will be described below by way of various examples.
[0097] The following measurement methods were used to determine the various parameters of the resulting composite nonwoven fabric.
[0098] Weight per unit area
[0099] The weight per unit area indicates the mass of the composite nonwoven fabric per unit area. The weight per unit area is determined according to standard NWSP 130.1.R0(15).
[0100] Tensile strength / elongation
[0101] The tensile strength value provides an indication of the durability of the wiping cloth during wiping or when removed from the packaging. Therefore, increased tensile strength results in greater resistance to damage under tensile loads. Low elongation facilitates removal of the wiping cloth from the packaging and helps to keep the wiping cloth properly in the wiping hand. The tensile strength or elongation is determined according to DIN EN 29073 Part 3 / ISO 9073-3 (1992 version).
[0102] Core suction
[0103] The rise height test (wicking) provides an indication of the distribution rate of liquid or washing liquid on the nonwoven fabric surface along the machine direction and transverse direction. The values listed below pertain to the rise height of water in the nonwoven fabric over a 300-second time period. The rise height is determined according to NWSP 010.1.R0(15).
[0104] Non-woven fabric adjustment
[0105] Before each measurement, the sample was conditioned for 24 hours at 23°C (±2°C) and 50% (±5%) relative humidity.
[0106] electron microscope
[0107] Electron microscope images were obtained using a Thermo Fisher Quanta 450 (5kV, Spot 3, WD10, EDT) or a Thermo Fisher Scientific, Phenom ProX type measuring instrument. Position selection was based on a random principle.
[0108] The composite nonwoven fabric described below was manufactured according to the method of the present invention, thereby producing a product with a density of 20-45 g / m². 2 A single layer of Lyocell spunbond nonwoven fabric is prepared per unit area weight and loaded with a 0.8-1.5% pulp suspension within a washing unit by means of a separately installed wet-laying mechanism. Finally, the composite nonwoven fabric is treated by water jet curing at three pressure levels (between 40 bar and 100 bar), dried to a final moisture content of less than 10%, and has a density of 30-80 g / m². 2 The curing is achieved by using rolls of fabric with a unit area weight. The nozzle strips used in the waterjet curing mechanism exhibit a single-row perforation pattern with a hole diameter of 0.12 mm and a hole spacing of 13 holes / cm.
[0109] The detailed parameters of the tests performed and the measured properties of the composite nonwoven fabrics are shown in Table 1 below.
[0110] Table 1: Test Parameters and Product Performance
[0111] Examples / Products 1 2 3 4 5 <![CDATA[Grammage of the substrate [g / m 2 > 45 20 20 20 20 Solid content of suspension [%) 0.5 0.7 0.8 1.0 1.2 Water jet curing pressure p1 [bar] 40 70 40 40 40 Water jet curing pressure p2 [bar] 40 80 40 40 40 Water jet curing pressure p3 [bar] 60 100 70 40 40 <![CDATA[Unit weight per unit area of the final product [g / m 2 > 70 45 45 45 60 Tensile strength (dry, MD) [N / 5cm] 45 16 30 33 40 Tensile strength (dry, CD) [N 5cm] 18 7 10 12 15 Tensile strength (wet, MD) [N / 5cm] 14 6 10 11 8 Tensile strength (wet, CD) [N 5cmm] 6 3 5 5 5 Elongation (dry, MD) [% / 5cm] 4 4 4 4 4 Elongation (dry, CD) [% / 5cm] 7 7 7 7 7 Elongation (wet, MD) [% / 5cm] 14 8 8 8 8 Elongation (wet, CD) [% 5cm] 27 28 18 20 25 Core suction MD [mm] 146 161 149 150 152 Core-loaded CD [mm] 122 139 132 131 133 .
[0112] In parallel with the composite nonwoven fabric manufactured according to the present invention, based on a polypropylene nonwoven fabric substrate having the added pulp, at 45 g / m 2The mechanical properties of commercially common composite nonwoven fabrics were studied in terms of total area weight. The commercial product exhibits a dry tensile strength comparable to Example Product 4 cited in Table 1, with a dry tensile strength of 33 N / 5 cm along the machine direction (MD) and 13 N / 5 cm along the transverse direction (CD). These strength values provide an indication of the wiping cloth's durability during wiping or upon removal from packaging, wherein the composite nonwoven fabric according to the invention cited is sufficient without the use of a synthetic carrier nonwoven fabric. Conversely, paper products with comparable area weights that are simply wet-laid exhibit a lower wet tensile strength of 4-8 N / 5 cm, which is hardly sufficient for common applications as wet wiping cloths.
[0113] Also based on a polypropylene nonwoven fabric substrate with added pulp, at 45 g / m 2 The ability of the previously cited commercially common composite nonwoven fabric to absorb liquid was studied in terms of total unit area weight: according to the wicking test, a significantly lower rise height of 94 mm along MD and 73 mm along CD was measured, which gives a significant advantage to the product of the invention in terms of the loading speed of the washing liquid during the conversion process compared to commercial wet wipes. That is, the dry roll fabric absorbs the washing liquid significantly faster during the loading process, and the uniformly distributed liquid in the closed wipe package shows the formation of the loading gradient significantly slower due to the weight-induced drop of the liquid.
Claims
1. A method for manufacturing a composite nonwoven fabric (1), comprising at least one spunbond nonwoven fabric (8, 54, 64) and at least one layer (52, 62) composed of bio-based biodegradable short fibers (14, 53, 63), said spunbond nonwoven fabric having filaments (4, 55, 65) of regenerated cellulose laid out in a random orientation and substantially continuously, wherein said composite nonwoven fabric (1, 51, 61) has at least one mixing region (56, 66) in which the filaments (4, 55, 65) of said spunbond nonwoven fabric (8, 54, 64) and said short fibers (14, 53, 63) are physically connected to each other, wherein a spun material (2) comprising cellulose is passed through at least one first spinning nozzle (3). Multiple nozzle orifices are extruded into first filaments (4) and multiple nozzle orifices of at least one second spinning nozzle (23) are extruded into second filaments (24) and the filaments (4, 24) are stretched along the extrusion direction, wherein the filaments (4) of the first spinning nozzle (3) are laid in a random orientation on a perforated conveying mechanism (7) to form a first spunbond nonwoven fabric (8), and wherein short fibers (14) are added to the filaments (4) of the first spunbond nonwoven fabric (8) in a undried state, and wherein the filaments (4) of the second spinning nozzle are laid in a random orientation on the spunbond nonwoven fabric loaded with short fibers on the conveying mechanism in a undried state to form a second spunbond nonwoven fabric and to form a composite nonwoven fabric (1).
2. The method according to claim 1, characterized in that, While still wet, a suspension (15) consisting of short fibers (14) is loaded onto the filament (4) of the first spunbond nonwoven fabric (8).
3. The method according to claim 2, characterized in that, The suspension (15) contains short fibers (14) at 0.01% (by weight) to 2.00% (by weight).
4. The method according to claim 2, characterized in that, The suspension (15) is loaded onto the filaments (4) of the spunbond nonwoven fabric (8) during the formation of the spunbond nonwoven fabric (8).
5. The method according to claim 1, characterized in that, An airflow (26) containing short fibers (14) is applied to the filament (4) of the spunbond nonwoven fabric (8) while it is still wet.
6. The method according to claim 1, characterized in that, After loading short fibers (14) onto the filament (4), the composite nonwoven fabric (1) is subjected to at least one processing step, wherein the processing step is selected from the group consisting of: water jet curing (16), water jet embossing, water jet perforation, washing (10), and drying (17).
7. The method according to claim 1, characterized in that, The spinning material (2) is a solution of cellulose in a direct solvent.
8. The method according to claim 7, characterized in that, The direct solvent is a tertiary amine oxide.
9. The method according to claim 1, characterized in that, The filament (4) is at least partially condensed after being extruded from the at least one spinning nozzle (3).
10. The method according to claim 1, characterized in that, The short fibers (14, 53, 63) are cellulose short fibers (14, 53, 63) and the composite nonwoven fabric (1, 51, 61) has a cellulose content of at least 93% (by weight) in an absolutely dry state.
11. The method according to claim 10, characterized in that, The short fibers (14, 53, 63) are cellulose short fibers (14, 53, 63) and the composite nonwoven fabric (1, 51, 61) has a cellulose content of at least 95% (by weight) in an absolutely dry state.
12. The method according to claim 10 or 11, characterized in that, The short fibers (14, 53, 63) are cellulose short fibers (14, 53, 63) and the composite nonwoven fabric (1, 51, 61) has a cellulose content of at least 97% (by weight) in an absolutely dry state.
13. The method according to claim 1, characterized in that, The composite nonwoven fabrics (1, 51, 61) have cellulose filaments (4, 55, 65) of spunbond nonwoven fabrics (8, 54, 64) in the range of 10% (by weight) to 99% (by weight) and short fibers (14, 53, 63) in the range of 1% (by weight) to 90% (by weight).
14. The method according to claim 13, characterized in that, The composite nonwoven fabrics (1, 51, 61) have cellulose filaments (4, 55, 65) of spunbond nonwoven fabrics (8, 54, 64) in a ratio between 15% (by weight) and 95% (by weight).
15. The method according to claim 13, characterized in that, The composite nonwoven fabrics (1, 51, 61) have cellulose filaments (4, 55, 65) of spunbond nonwoven fabrics (8, 54, 64) in a ratio between 20% (by weight) and 90% (by weight).
16. The method according to any one of claims 13 to 14, characterized in that, The composite nonwoven fabrics (1, 51, 61) have short fibers (14, 53, 63) ranging from 5% (by weight) to 85% (by weight).
17. The method according to claim 16, characterized in that, The composite nonwoven fabrics (1, 51, 61) have short fibers (14, 53, 63) in the range of 10% (by weight) to 80% (by weight).
18. The method according to claim 1, characterized in that, The composite nonwoven fabrics (1, 51, 61) are essentially free of adhesives that are not naturally present in wood.
19. The method according to claim 1, characterized in that, The short fibers (14, 53, 63) are selected from the following groups, which include: natural cellulose fibers, pulp fibers, viscose fibers, modal fibers, cuprammonium fibers and lyocell fibers, chemically modified cellulose fibers, recycled cellulose fibers, and starch fibers.
20. The method according to claim 1, characterized in that, The short fibers (14, 53, 63) have a length between 0.5 mm and 15 mm.
21. The method according to claim 20, characterized in that, The short fibers (14, 53, 63) have a length between 1 and 12 mm.
22. A composite nonwoven fabric comprising at least two spunbond nonwoven fabrics (8, 54, 64) and at least one layer (52, 62) composed of bio-based biodegradable short fibers (14, 53, 63), said spunbond nonwoven fabric having filaments (4, 55, 65) of regenerated cellulose laid out in a random orientation and substantially continuously, characterized in that, The composite nonwoven fabrics (1, 51, 61) can be obtained by the method (100, 101, 102) according to claim 1.
23. An apparatus for carrying out the method according to claim 1, comprising: A spinning material preparation mechanism for preparing cellulose spinning material; at least two spunbond nonwoven fabric devices for manufacturing cellulose spunbond nonwoven fabrics composed of spinning material, each spunbond nonwoven fabric device having at least one spinning nozzle (3, 23) for extruding the spinning material into filaments (4, 24), at least one condensation system for at least partially condensing the filaments, and a conveying mechanism for laying the filaments and forming the spunbond nonwoven fabric; a washing mechanism, a dryer, and a winding machine, characterized in that the device has a wet lay-up mechanism or a dry lay-up mechanism for loading short fibers into the cellulose spunbond nonwoven fabric, the wet lay-up mechanism or dry lay-up mechanism for the short fibers being disposed between the two spunbond nonwoven fabric devices.
24. The apparatus according to claim 23, wherein, The spunbond nonwoven fabric equipment has a water jet curing mechanism.
25. The apparatus according to claim 23 or 24, wherein, The spunbond nonwoven fabric equipment has a crepe-forming mechanism.