Nonwoven material

Abstract

The invention pertains to a nonwoven material and a method for the production of a nonwoven material. The method comprises at least the steps of suspending fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the nonwoven material. The nonwoven material comprises from 30 % to 95 % per weight natural plant-based fibers and / or man-made cellulosic fibers and from 5 % per weight to 70 % per weight of flat lyocell fibers. The flat lyocell fibers are provided with a flat cross section with a cross-sectional aspect ratio of at least 1.8. The surface of the flat lyocell fibers is free of fibrillation grooves.

Description

Field of the invention

[0001] The present disclosure relates to innovations concerning the production of nonwoven materials and their composition.Description of the Related Art

[0002] It is generally known to add natural plant fibers to the fiber feedstock used to produce nonwoven materials, such as fiber fleeces or papers. The natural plant fiber fraction increase the strength of the so produced material. For example, it is known to add abaca pulp in the production of specialty papers to increase, inter alia, tensile strength and ball-burst strength of the so produced paper. As an alternative to abaca, the use of other natural fibers, such as sisal, hemp, kenaf, esparto or the like, has been suggested, but their performance is inferior to abaca.

[0003] Unfortunately, abaca (also known as manila hemp) is a rather expensive raw material. Also, abaca is a seasonal product that can strongly differ in quality from one season to the next or depending on the origin. This makes it difficult to exactly reproduce paper quality parameters. Other natural products that could be used to substitute abaca come with similar problems.

[0004] It would be desirable to reduce or eliminate the need for the addition of Abaca in the production of strong nonwoven materials, such as specialty papers, and, at the same time, to increase the reproducibility of the quality parameters of such materials.

[0005] WO2022023394 A1 discloses the use of highly fibrillated flat lyocell fibers in nonwoven fiber materials, e.g. for specialty paper for battery separators. The disclosure is based on the specific tendency of flat lyocell fibers to easily fibrillate and form long and fine fibrils while keeping an intact fiber core.Summary

[0006] The present disclosure describes methods and materials that overcome the drawback of known techniques and products.

[0007] According to one aspect, the present application discloses a nonwoven material produced by a method comprising at least the steps of suspending fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the nonwoven material, wherein the nonwoven material comprises from 30 % to 95 % per weight natural plant-based fibers and / or man-made cellulosic fibers and from 5 % per weight to 70 % per weight, preferably from 10 % per weight to 55 % per weight flat lyocell fibers, wherein the flat lyocell fibers are provided with a flat cross section with a cross-sectional aspect ratio of at least 1.8, preferably of at least 4 or even more preferred of at least 6 and wherein the surface of the flat lyocell fibers is free of fibrillation grooves. The so produced nonwoven material reduces or even eliminates the need for natural strengthening fibers, such as abaca pulp, by the use of flat, essentially unfibrillated lyocell fibers. The inventors have found that a very strong nonwoven material of high quality can be produced by using flat lyocell fibers instead of abaca pulp or similar material. Very surprisingly, the beneficial effects can be achieved with essentially unfibrillated flat lyocell fibers. This allows for a reproducible manufacture of nonwoven materials, such as papers or fleeces, with constant quality parameters. Also, the fibers do not need to be fibrillated, so that this rather energy- and resources-consuming processing step can be omitted.

[0008] The term "nonwoven material", as it is used herein, denotes any layer material produced from fibers using any production method comprising at least the steps of suspending the fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the fiber fleece. Depending on the specific properties of the nonwoven material, it can be generally referred to as paper or fleece or both denominations can be applicable for one product.

[0009] If an intentional fibrillation step has been carried out on fibers, this can easily be observed by microscopic imaging of the fibers. Fibers that have been subjected to any intentional fibrillation step show a strong fibrillation and a characteristic pattern of surface irregularities appearing as ripples or grooves. This pattern is herein referred to as "fibrillation grooves". Conversely, if the fiber surface is free of fibrillation grooves, it is obvious that the fibers have not been subjected to any intentional fibrillation step. Fibers that are free of fibrillations grooves have a smooth surface and can also be denoted as essentially unfibrillated fibers (although a small amount of fibrillation can also be observed with essentially unfibrillated fibers).

[0010] Generally speaking, the term "fibrillation grooves", as used herein, denotes surface irregularities that originate from a fibrillation treatment. Fibrillations grooves appear on fibers that have undergone a fibrillation treatment.

[0011] The term "fibrillation treatment", as it is used herein, denotes the application of a shearing force with a so-called refiner. Depending on the desired extend of fibrillation, the fibrillation treatment can be performed from few minutes up to several hours. Different types of refiners are known in the art and can be used to perform a fibrillation treatment. Most common examples for refiners comprise (but are not limited to) disc refiners applying a rotor / stator principle, cone refiners and cylinder refiners. Such a fibrillation treatment step is generally applied to staple fibers before they are being used to produce a nonwoven material.

[0012] The term "essentially unfibrillated", as it is used herein, denotes fibers that have not been subjected to any intentional fibrillation step before being used to produce the nonwoven material. Essentially unfibrillated fibers can have fibrils, but do not have the characteristic fibrillation grooves.

[0013] The term "flat" or "ribbon-like", as it is used herein, generally refers to a fiber having a cross-sectional aspect ratio significantly bigger than 1. The cross-sectional aspect ratio of the fibre is defined as the width to height ratio of a minimum bounding rectangle around the cross section of the fibre. The minimum bounding rectangle is the smallest rectangle circumscribing the perimeter of the fibre cross section. The width of the bounding rectangle thereby is measured along the longer direction of the fibre cross section. By all means, a fiber can be considered flat if its cross section has a cross-sectional aspect ratio of at least 1.8. In preferred embodiments the cross-sectional aspect ratio can be at least 4 or even more preferred at least 6. It has to be noted that an increase of the cross-sectional aspect ratio also increases the costs of the fibers. Therefore the fibers will be chosen not broader than necessary to achieve the desired results so that the costs will be minimized. The optimal value of the cross-sectional aspect ratio is therefore based on an optimization process taking into account the costs and the achieved results.

[0014] The term "natural plant-based fibers" refers to fibers that are produced by separating fibrous material from plant material. Examples for natural plant-based fibers include, but are not limited to, cotton, cotton linters, hemp, abaca, sisal, kenaf, esparto, hardwood pulp, softwood pulp and the like.

[0015] The term "man-made cellulosic fibers" refers to fibers produced from regenerated cellulose. Examples for man-made cellulosic fibers include, but are not limited to fibers produced according to a viscose process, a lyocell process, a cupra process, a cold-alkali process or a similar process.

[0016] The term "natural plant-based fibers and / or man-made cellulosic fibers ", as it is used herein, denotes fibers that are produced directly or indirectly from plants as a raw material or any mixture of such fibers.

[0017] According to a preferred embodiment, the nonwoven fiber fleece can have a dry specific tensile strength (Fmax) of at least 0.15 Nm 2< / g, preferable of at least 0.18 Nm 2< / g or even more preferred of at least 0.2 Nm 2< / g. It has been found that the use of flat, unfibrillated lyocell fibers allows for the production of nonwoven materials having significantly higher specific tensile strength compared to a nonwoven material that only differs in that it has round lyocell fibers of the same titer. Indeed, tests showed that the tensile strength could nearly be doubled just by exchanging round unfibrillated lyocell fibers by flat unfribrillated lyocell fibers without changing any other parameter of the so produced nonwoven.

[0018] This effect is quite surprising, as previous experiments and results revealed (also according to the teachings in the relevant state of the art) that the strength of the nonwoven material can only be raised by strongly fibrillating the fibers. Without being bound to this theory, the inventors believe that the strong effect of the essentially unfibrillated, flat lyocell fibers could be due to an increased fiber-to-fiber friction that is achieved by the flat fibers contacting each other on their flat surfaces.

[0019] According to one embodiment, the nonwoven material can have a ball burst strength of at least 2.5 N / 1.5 cm, preferable of at least 3 N / 1.5cm and most preferred of at least 3.5 N / 1.5 cm. Test showed that a relatively high ball burst strength can be reached at low basis weight.

[0020] According to another embodiment, the nonwoven material disclosed herein can have a tearing strength of at least 0.5 N / 75mm. A sufficient tearing strength is needed for many industrial applications and can be achieved according to the teachings herein.

[0021] According to some embodiments discloses herein, the nonwoven material can be produced by a method comprising at least one hydroentanglement step and / or at least one calendaring step. Hydroentanglement significantly increases the fiber bonding within the nonwoven material and so increases the strength of the nonwoven. Nonetheless, it could also be possible to reach the required properties with different and / or additional bonding techniques, such as thermal bonding, the use of binders or the like. In some cases, for example with airlaid material, also needling techniques can be used. Nonetheless, under certain conditions and for specific applications, a step of drying the nonwoven material could already give sufficient bonding so that any additional bonding step can be omitted.

[0022] Calendaring may be used to increase the density of the nonwoven material by reducing the thickness and the pore sizes. This also increases the strength of the nonwoven material.

[0023] According to another embodiment disclosed herein, the flat lyocell fibers of the nonwoven material can have an average cut-length in the range of 2 mm to 20 mm, preferably of 3 mm to 12 mm. The cut-length particularly effects the strength and the appearance of the nonwoven material. A short cut-length results in a nonwoven with reduced mechanical properties, whereas a longer cut-length increases the mechanical performance of the product but reduces the processability of the material. For most nonwoven applications, an optimal balance of the properties can be found at an average cut-length of about 4 mm to about 8 mm.

[0024] The nonwoven material according to another embodiment disclosed herein can have an air permeability in the range of 50 Ls / m 2< to 1000 Ls / m 2< , preferably of 70 Ls / m 2< to 200 Ls / m 2< . Generally, the air-permeability of a nonwoven material can be adjusted in a broad range by changing the main influence factors such as the grammage, the fiber titer, the extend of perforation, the degree of densifying (e.g. by hydroentagling energy or calendaring) and the like. It was found that by adjusting the amount of flat lyocell fibers and / or their properties, such as the cross-sectional aspect ratio, the air-permeability of the nonwoven material can be reproducibly adjusted in a surprisingly broad range. Therefore it is possible to adjust the air-permeability by adjusting the percentage of the flat lyocell fibers and / or their properties, e.g. their cross-sectional aspect ratio and / or their fiber titer and / or their fiber length.

[0025] In one preferred embodiment, the nonwoven material can have a thickness in the range of between 0.02 mm and 2 mm. Very thin nonwoven materials, for example in the range of between 0.02 and 0.08 mm, can, for example, be used for the production of insulation papers and beverage filters, such as coffee filters, teabags, casing paper or the like. Ab bit thicker nonwoven materials, for example in the range of between 0.08 mm and 0.3 mm, can be used, for example for the production of filter media for industrial and automotive applications and wallpaper. Even thicker material can be preferred for other applications, such as padding material for meat packaging.

[0026] In this context, also the production process has an effect on the optimal thickness range. For example, an airlaid process can be optimally used to produce thicker nonwoven materials, e.g. with a thickness in the range of 0.1 mm to 2 mm, preferably from 0.3 to 0.8 mm, whereas wetlaid nonwoven materials can be produced to be very thin, e.g. to have a thickness in the range of 0.02 mm to 0.5 mm.

[0027] The nonwoven material according to one embodiment disclosed herein can comprise supplemental fibers, preferably in a range of between 0 % per weight and 65 % per weight, wherein the supplemental fibers are selected from a group comprising: synthetic fibers, such as polyester fibers, polyethylene fibers, polypropylene fibers, polyamide fibers, elastane fibers, aramid fibers, animal fibers, PLA-fibers or a mixture of two or more of such fibers. The addition of supplemental fibers can be used to achieve very specific and special properties for the nonwoven material.

[0028] Another aspect of the present disclosure pertains to a product comprising a nonwoven material as disclosed herein, wherein the product is selected from the group comprising filter media for beverages, such as tea bags or coffee pods, meat casing paper, automotive or industrial filter media, electrical or insulation papers, security papers, banknote papers, medical papers, packaging papers, food contact papers, food tray absorption layers, wrapping papers, wallpapers, décor or overlay papers, agricultural papers, tobacco papers, tapes, moist toilet tissues, hygienic products, such as pantiliners or sanitary pads. The teachings disclosed herein allow for the production of nonwoven materials with very well adjusted properties that can be accurately adapted to the specific needs of numerous applications.

[0029] In another aspect the present disclosure concerns the use of a nonwoven material disclosed herein for the production of a product, wherein the product is selected from the group comprising filter media for beverages, such as tea bags or coffee pods, meat casing paper, automotive or industrial filter media, electrical or insulation papers, security papers, banknote papers, medical papers, packaging papers, food contact papers, food tray absorption layers, wrapping papers, wallpapers, décor or overlay papers, agricultural papers, tobacco papers, tapes, moist toilet tissues, hygienic products, such as pantiliners or sanitary pads. According to the teachings disclosed herein, the properties of a nonwoven material can be reproducibly and accurately adjusted for a broad range of different applications.

[0030] According to another aspect, the present application discloses a method for the production of a nonwoven material, wherein the method comprises at least the steps of suspending fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the nonwoven material, wherein the nonwoven material comprises from 30 % to 95 % per weight natural plant-based fibers and / or man-made cellulosic fibers and from 5 % per weight to 70 % per weight, preferably from 10 % per weight to 55 % per weight flat lyocell fibers, wherein the flat lyocell fibers are provided with a flat cross section with a cross-sectional aspect ratio of at least 1.8, preferably of at least 4 or even more preferred of at least 6 and wherein the surface of the flat lyocell fibers is free of fibrillation grooves. The method allows for the production of nonwoven materials having specifically adjusted quality parameters in a reproducible way. Negative effects of quality changes of seasonal products, such as Abaca or the like, can be avoided.

[0031] In a preferred embodiment, the method comprises at least one hydroentanglement step and / or at least one calendaring step. The possible range of achievable parameters can be extended even further by using a hydroentanglement step, a calendaring step of a combination of such steps. The processes of hydroentanglement or calendaring are per se known in the art and can therefore easily applied to the nonwovens disclosed herein.

[0032] According to another preferred embodiment of the method disclosed herein, the suspension fluid is a liquid, preferably an aqueous solution or water. Such a method is commonly also known as "wetlaid process" and is especially well-known from the area of paper production. In a wetlaid process, the raw material fibers (in paper production commonly paper pulp is used) is suspended in an aqueous medium, e.g. water, to for a slurry. The slurry can also comprise other fibers, e.g. it is known to add synthetic fibers to the slurry. The slurry is then deposited on a moving permeable screen, where the water is drained to form the nonwoven material. The material is further dewatered, e.g. by pressing between rollers, and dried. It has been found that by combining these well-known techniques with the teachings disclosed herein, nonwoven materials with exceptional properties can be produces.

[0033] According to another preferred embodiment of the method disclosed herein, the suspension fluid can be a gaseous medium, preferably air. Such a method is per-se known in the art as an "airlaid process". The airlaid process can be implemented by feeding the raw-material fibers (which are generally relatively short) into a forming head by an airstream. By air again, a controlled part of the fibre mix leaves the forming head and is deposited on a moving belt, where a randomly oriented web is formed. Compared to the wetlaid process, airlaid webs have a lower density, a greater softness and a higher thickness. Airlaid webs offer great versatility in terms of the fibres and fibre blends that can be used. Further, the airlaid process allows for a very homogeneous mixture of the fibers in case different fiber types are used as the raw-material.

[0034] It has been found, that the use of essentially unfibrillated flat lyocell fibers in a airlaid process allows for the production of nonwoven material with surprising properties. Such nonwovens performed extremely well in a slosh-box-test which indicates a very good flushability of the material. At the same time, the nonwoven had a high wet tensile strength. Such properties are highly desirable for flushable wipes. Therefore, the use of flat fibers in an airlaid process allow for the production of nonwoven materials that could pass most stringent flushability guidelines, such as IWSFG, even with high wet tensile strength.Brief Description of the Figures

[0035] Hereinafter, exemplary embodiments of the invention are described with reference to the drawings, wherein Fig. 1is a microscopic image of flat lyocell fibers free of fibrillation grooves, Fig. 2is another microscopic image of flat, unfibrillated lyocell fibers in a sectional view showing the cross-sections of the fibers, Fig. 3is a microscopic image of flat lyocell fibers that have been subjected to a fibrillation step, Fig. 4is a higher resolution microscopic image of flat lyocell fibers that have been subjected to a fibrillation step and Fig. 5is a microscopic image showing a cross-section of a nonwoven material comprising flat, unfibrillated lyocell fibers and pulp fibers. Detailed description of the Figures

[0036] The microscopic images shown in Fig. 1 and 2 were taken with an electron microscope of the type Phenom Pro X with the software Phenom Pro Suite at a magnification of 500x (Fig. 1) and 650x (Fig. 2).

[0037] The microscopic images shown in Fig. 3, 4 and 5 were taken with an electron microscope of the type FEI Quanta 450 with the software FEI Quanta Microscope Control, v6.2.10, at a magnification of 500x (Fig. 3 and 5) and 1000x (Fig. 4).

[0038] Fig. 1 shows a cluster of flat, unfibrillated lyocell fibers. The fibers have a smooth surface free of any fibrillation grooves which clearly shows that they have not undergone any fibrillation step. Nonetheless, some minor fibrills can be seen as they normally occur on any lyocell fibers. The fibers shown are quite uniform having a width of about 20 - 30 µm and a thickness of about 5-10 µm. In this case, the cross-sectional aspect ratio of the fibres, which is defined as the width to height ratio of a minimum bounding rectangle around the cross section of the fibre, would probably be in the range of 3-4. An exact determination cannot be made from this view but it is known in the art how to assess and measure an average value of the cross-sectional aspect ratio with an adequate accuracy.

[0039] Fig. 2 shows another view of a cluster of flat, unfibrillated lyocell fibers, but this time in a cross-sectional view focused on the fiber-cross-sections. The flat cross-section can be clearly observed in this view. The cross-section differs from one fiber to another, which is also partly due to the cutting angle.

[0040] As a comparison, Fig. 3 shows a cluster of fibrillated flat lyocell fibers. It can be observed that the fibrillation not only produced a high number of fibrills, but also affected the surface of the fibers, which are no longer smooth and even, but show a distinctive pattern of fibrillation grooves.

[0041] In Fig. 4, which shows fibrillated fibers in a higher resolution, the fibrillation grooves can be seen as a pattern of lines running mainly parallelly to the main axis of the fibers.

[0042] Fig. 5 shows a microscopic image of a fiber mixture comprising flat, unfibrillated lyocell fibers and pulp fibers. The pulp fibers show an irregular form and an uneven surface, whereas the lyocell fibers show their typically smooth surface and have a very uniform cross-section.Examples

[0043] Several Samples of nonwoven materials were produced according to the same production method but with different material compositions.Production method

[0044] All nonwoven samples were produced using two different fibrous raw materials, a wood pulp fraction (Canfor) and a fiber fraction (either lyocell fibers, abaca or PSPI). All nonwovens were produced using a Rapid-Köthen Sheet Former (Type RK-2A).

[0045] For all samples the wood pulp was first teared into coarse pieces and left to soak in water for a few minutes at a ratio of approximately 1 / 15. The soaked, softened pulp was then mixed with a propeller mixer at 800-1500 rpm until a homogeneous paste was obtained. The resulting pulp solution was then transferred to a G2 frit and slipped off without applying pressure. The filter cake was then transferred to a large plate, carefully plucked and dried overnight at 60°C in a vacuum drying oven. The dried pulp was finely plucked and conditioned overnight in the laboratory before it was used for further processing.

[0046] The moisture content of the fiber fraction and of the conditioned, dried pulps were determined before they were weighed for sheet production.

[0047] The prepared pulp and fibers were weighed into single sample vails. Distilled water was added to soften the material at least 4 hours before paper manufacturing. Further processing at this stage took place within 2 days maximum.

[0048] For the paper preparation, a whipping beaker was filled with 2 liters of tap water and the precisely weighed pulp was added to the water. The so produced pulp suspension was mixed in the beaker at 3000 rpm for 2 minutes. The beaker was then opened and the previously weighed fibers were added. The beaker was locked again, and mixing procedure was repeated for 15 seconds at 3000 rpm.

[0049] A sieve was placed in the sheet former and tightly closed. The forming process was started. When the water covers the spray nozzles of the leaf former, the entire fine suspension of the beaker (with pulp and fiber mix) were emptied into the leaf former and the stirring cup was quickly rinsed with a spray bottle.

[0050] The sheet former was opened, the sieve with the hand-paper on it was placed in the drying unit and covered with a protective plastic film.

[0051] The drying unit was closed, and vacuum was applied. The round paper was dried for 10 minutes at 90°C.

[0052] For each setup, 10 identical papers were produced.Raw material fibers

[0053] The following fiber types were used for the production of the samples: Lyocell shortcut 8 mm flat ("1.7dtex / 8 mm flat") Aspect ratio of fiber: 3.4. Produced in house (i.e. at Lenzing AG, Austria) in pilot line scale, finished and cut using a laboratory guillotine. Lyocell shortcut 6 mm flat ("1.7dtex / 6mm flat") Aspect ratio of fiber: 3.4. Produced in house in pilot line scale, finished and cut using a laboratory guillotine Lyocell shortcut 8 mm round ("1.7dtex / 6mm round") Produced in house in pilot line scale, finished and cut using a laboratory guillotine. Lyocell shortcut 6 mm round ("1.7dtex / 8mm round") Produced in house in pilot line scale, finished and cut using a laboratory guillotine. Canfor IC90 pulp ("Canfor") Softwood long fiber pulp. Abaca AEU05 ("Abaca") Abaca pulp market sample obtained from Specialty Pulp Manufacturing Inc (SPMI), 358 Quezon Avenue, Quezon City, 1113 Philippines. PSPI 100 pulp ("PSPI") Abaca pulp market sample obtained from Pulp Specialties Philippines Inc (PSPI), 8741 Paseo de Roxas, Makati City, 1200 Philippines. Parameter measurements

[0054] Before taking measurements, all samples were conditioned according to NWSP 003.0.R0 (15).

[0055] On all conditioned samples parameters were measured according to the following protocols: Thickness (THK) - [mm]: Edana Nonwovens Standard Procedure (NWSP) 120.6.R0 (15) [EN] Basis Weight (BW) - [g / m 2< ]: NSWP 130.1.R0(15) [EN] Bulkiness (BULK) - [kg / m 3< ] - was calculated according to the formula: bulk kg / m 3 = basis weight gsm / thickness mm Dry specific tensile strength (Fspec) - [Nm 2< / g]: NWSP 110.4.R0 (15) [EN] Tearing strength (TEAR) - [N / 75mm]: NWSP 100.2.R1 (15) [EN] Ball burst strength (BBURST) - [N / 1.5cm]: NWSP110.5.(15) Air permeability (Perm) - [L*s / m 2< ]: DIN ISO 9237 - 1995 Sample properties

[0056] All samples were produced according to the production method described above. The percentages given in Table 1 below all refer to % per weight of the fiber blend of the raw material fibers. Table 1 - Raw material compositionsSAMPLE PULP FRACTION FIBER FRACTION Sample 1 40% Lyocell shortcut 6 mm flat 60% Canfor IC90 Sample 2 (Comparison)40% Lyocell shortcut 6 mm round60% Canfor IC90Sample 3 (Comparison)40% PSPI 10060% Canfor IC90Sample 4 (Comparison)40% Abaca AEU0560% Canfor IC90Sample 5 30% Lyocell shortcut 8 mm flat 70% Canfor IC90 Sample 6 (Comparison)30% Lyocell shortcut 8 mm round70% Canfor IC90Sample 7 (Comparison)30% PSP 10070% Canfor IC90Sample 8 (Comparison)30% Abaca AEU0570% Canfor IC90 Results and discussion

[0057] Measurement results for the different samples are shown in Table 2 below. Comparison Samples that did not comprise any flat lyocell fibers are marked with (C). Table 2 - Parameter comparison of nonwoven samplesSample code Fiber blend THK [mm] BW [g / m 2< ] BULK [kf / m 3< ] Fspec [Nm 2< / g] TEAR [N / 75mm] BBURST [N / 1.5cm] Perm [Ls / m 2< ] Sample 140% 1.7 / 6 flat0.12433080.250.84.5208E33_23_0668_1460% CanforSample 2 (C)40% 1.7 / 6 round0.14433060.130.52.4350E33_23_0668_1360 % CanforSample 3 (C)40% PSPI0.13473620.2817.677E33_23_0666_1960% CanforSample 4 (C)40% Abaca0.14473380.221.18297E33_23_0668_2160% CanforSample 530% 1.7 / 8 flat0.1333260.220.83.1300E33_23_0666_0770% CanforSample 6 (C)30% 1.7 / 8 round0.11332950.120.41432E33_23_0666_0870% CanforSample 7 (C)30% PSPI0.09313490.210.83.1204E33_23_0666_1870% CanforSample 8 (C)30% Abaca0.11322860.180.82.4157E33_23_0666_2070%Canfor

[0058] The results show that nonwoven materials comprising flat, unfibrillated lyocell fibers (i.e. Samples 1 and 5) show a significantly elevated tensile strength, tearing strength and ball burst strength than the direct comparison samples (Samples 2 and 6, respectively). Further, the results show that nonwoven materials that comprise flat, unfibrillated lyocell fibers show properties that are comparable to state of the art nonwoven materials comprising Abaca (Comparison Samples 4 and 8) or PSP (Comparison Samples 3 and 7).

Examples

examples

Examples

[0043]Several Samples of nonwoven materials were produced according to the same production method but with different material compositions.

Production method

[0044]All nonwoven samples were produced using two different fibrous raw materials, a wood pulp fraction (Canfor) and a fiber fraction (either lyocell fibers, abaca or PSPI). All nonwovens were produced using a Rapid-Köthen Sheet Former (Type RK-2A).

[0045]For all samples the wood pulp was first teared into coarse pieces and left to soak in water for a few minutes at a ratio of approximately 1 / 15. The soaked, softened pulp was then mixed with a propeller mixer at 800-1500 rpm until a homogeneous paste was obtained. The resulting pulp solution was then transferred to a G2 frit and slipped off without applying pressure. The filter cake was then transferred to a large plate, carefully plucked and dried overnight at 60°C in a vacuum drying oven. The dried pulp was finely plucked and conditioned overnight in the laboratory befo...

Field of the invention

[0001] The present disclosure relates to innovations concerning the production of nonwoven materials and their composition.Description of the Related Art

[0002] It is generally known to add natural plant fibers to the fiber feedstock used to produce nonwoven materials, such as fiber fleeces or papers. The natural plant fiber fraction increase the strength of the so produced material. For example, it is known to add abaca pulp in the production of specialty papers to increase, inter alia, tensile strength and ball-burst strength of the so produced paper. As an alternative to abaca, the use of other natural fibers, such as sisal, hemp, kenaf, esparto or the like, has been suggested, but their performance is inferior to abaca.

[0003] Unfortunately, abaca (also known as manila hemp) is a rather expensive raw material. Also, abaca is a seasonal product that can strongly differ in quality from one season to the next or depending on the origin. This makes it difficult to exactly reproduce paper quality parameters. Other natural products that could be used to substitute abaca come with similar problems.

[0004] It would be desirable to reduce or eliminate the need for the addition of Abaca in the production of strong nonwoven materials, such as specialty papers, and, at the same time, to increase the reproducibility of the quality parameters of such materials.

[0005] WO2022023394 A1 discloses the use of highly fibrillated flat lyocell fibers in nonwoven fiber materials, e.g. for specialty paper for battery separators. The disclosure is based on the specific tendency of flat lyocell fibers to easily fibrillate and form long and fine fibrils while keeping an intact fiber core.Summary

[0006] The present disclosure describes methods and materials that overcome the drawback of known techniques and products.

[0007] According to one aspect, the present application discloses a nonwoven material produced by a method comprising at least the steps of suspending fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the nonwoven material, wherein the nonwoven material comprises from 30 % to 95 % per weight natural plant-based fibers and / or man-made cellulosic fibers and from 5 % per weight to 70 % per weight, preferably from 10 % per weight to 55 % per weight flat lyocell fibers, wherein the flat lyocell fibers are provided with a flat cross section with a cross-sectional aspect ratio of at least 1.8, preferably of at least 4 or even more preferred of at least 6 and wherein the surface of the flat lyocell fibers is free of fibrillation grooves. The so produced nonwoven material reduces or even eliminates the need for natural strengthening fibers, such as abaca pulp, by the use of flat, essentially unfibrillated lyocell fibers. The inventors have found that a very strong nonwoven material of high quality can be produced by using flat lyocell fibers instead of abaca pulp or similar material. Very surprisingly, the beneficial effects can be achieved with essentially unfibrillated flat lyocell fibers. This allows for a reproducible manufacture of nonwoven materials, such as papers or fleeces, with constant quality parameters. Also, the fibers do not need to be fibrillated, so that this rather energy- and resources-consuming processing step can be omitted.

[0008] The term "nonwoven material", as it is used herein, denotes any layer material produced from fibers using any production method comprising at least the steps of suspending the fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the fiber fleece. Depending on the specific properties of the nonwoven material, it can be generally referred to as paper or fleece or both denominations can be applicable for one product.

[0009] If an intentional fibrillation step has been carried out on fibers, this can easily be observed by microscopic imaging of the fibers. Fibers that have been subjected to any intentional fibrillation step show a strong fibrillation and a characteristic pattern of surface irregularities appearing as ripples or grooves. This pattern is herein referred to as "fibrillation grooves". Conversely, if the fiber surface is free of fibrillation grooves, it is obvious that the fibers have not been subjected to any intentional fibrillation step. Fibers that are free of fibrillations grooves have a smooth surface and can also be denoted as essentially unfibrillated fibers (although a small amount of fibrillation can also be observed with essentially unfibrillated fibers).

[0010] Generally speaking, the term "fibrillation grooves", as used herein, denotes surface irregularities that originate from a fibrillation treatment. Fibrillations grooves appear on fibers that have undergone a fibrillation treatment.

[0011] The term "fibrillation treatment", as it is used herein, denotes the application of a shearing force with a so-called refiner. Depending on the desired extend of fibrillation, the fibrillation treatment can be performed from few minutes up to several hours. Different types of refiners are known in the art and can be used to perform a fibrillation treatment. Most common examples for refiners comprise (but are not limited to) disc refiners applying a rotor / stator principle, cone refiners and cylinder refiners. Such a fibrillation treatment step is generally applied to staple fibers before they are being used to produce a nonwoven material.

[0012] The term "essentially unfibrillated", as it is used herein, denotes fibers that have not been subjected to any intentional fibrillation step before being used to produce the nonwoven material. Essentially unfibrillated fibers can have fibrils, but do not have the characteristic fibrillation grooves.

[0013] The term "flat" or "ribbon-like", as it is used herein, generally refers to a fiber having a cross-sectional aspect ratio significantly bigger than 1. The cross-sectional aspect ratio of the fibre is defined as the width to height ratio of a minimum bounding rectangle around the cross section of the fibre. The minimum bounding rectangle is the smallest rectangle circumscribing the perimeter of the fibre cross section. The width of the bounding rectangle thereby is measured along the longer direction of the fibre cross section. By all means, a fiber can be considered flat if its cross section has a cross-sectional aspect ratio of at least 1.8. In preferred embodiments the cross-sectional aspect ratio can be at least 4 or even more preferred at least 6. It has to be noted that an increase of the cross-sectional aspect ratio also increases the costs of the fibers. Therefore the fibers will be chosen not broader than necessary to achieve the desired results so that the costs will be minimized. The optimal value of the cross-sectional aspect ratio is therefore based on an optimization process taking into account the costs and the achieved results.

[0014] The term "natural plant-based fibers" refers to fibers that are produced by separating fibrous material from plant material. Examples for natural plant-based fibers include, but are not limited to, cotton, cotton linters, hemp, abaca, sisal, kenaf, esparto, hardwood pulp, softwood pulp and the like.

[0015] The term "man-made cellulosic fibers" refers to fibers produced from regenerated cellulose. Examples for man-made cellulosic fibers include, but are not limited to fibers produced according to a viscose process, a lyocell process, a cupra process, a cold-alkali process or a similar process.

[0016] The term "natural plant-based fibers and / or man-made cellulosic fibers ", as it is used herein, denotes fibers that are produced directly or indirectly from plants as a raw material or any mixture of such fibers.

[0017] According to a preferred embodiment, the nonwoven fiber fleece can have a dry specific tensile strength (Fmax) of at least 0.15 Nm 2< / g, preferable of at least 0.18 Nm 2< / g or even more preferred of at least 0.2 Nm 2< / g. It has been found that the use of flat, unfibrillated lyocell fibers allows for the production of nonwoven materials having significantly higher specific tensile strength compared to a nonwoven material that only differs in that it has round lyocell fibers of the same titer. Indeed, tests showed that the tensile strength could nearly be doubled just by exchanging round unfibrillated lyocell fibers by flat unfribrillated lyocell fibers without changing any other parameter of the so produced nonwoven.

[0018] This effect is quite surprising, as previous experiments and results revealed (also according to the teachings in the relevant state of the art) that the strength of the nonwoven material can only be raised by strongly fibrillating the fibers. Without being bound to this theory, the inventors believe that the strong effect of the essentially unfibrillated, flat lyocell fibers could be due to an increased fiber-to-fiber friction that is achieved by the flat fibers contacting each other on their flat surfaces.

[0019] According to one embodiment, the nonwoven material can have a ball burst strength of at least 2.5 N / 1.5 cm, preferable of at least 3 N / 1.5cm and most preferred of at least 3.5 N / 1.5 cm. Test showed that a relatively high ball burst strength can be reached at low basis weight.

[0020] According to another embodiment, the nonwoven material disclosed herein can have a tearing strength of at least 0.5 N / 75mm. A sufficient tearing strength is needed for many industrial applications and can be achieved according to the teachings herein.

[0021] According to some embodiments discloses herein, the nonwoven material can be produced by a method comprising at least one hydroentanglement step and / or at least one calendaring step. Hydroentanglement significantly increases the fiber bonding within the nonwoven material and so increases the strength of the nonwoven. Nonetheless, it could also be possible to reach the required properties with different and / or additional bonding techniques, such as thermal bonding, the use of binders or the like. In some cases, for example with airlaid material, also needling techniques can be used. Nonetheless, under certain conditions and for specific applications, a step of drying the nonwoven material could already give sufficient bonding so that any additional bonding step can be omitted.

[0022] Calendaring may be used to increase the density of the nonwoven material by reducing the thickness and the pore sizes. This also increases the strength of the nonwoven material.

[0023] According to another embodiment disclosed herein, the flat lyocell fibers of the nonwoven material can have an average cut-length in the range of 2 mm to 20 mm, preferably of 3 mm to 12 mm. The cut-length particularly effects the strength and the appearance of the nonwoven material. A short cut-length results in a nonwoven with reduced mechanical properties, whereas a longer cut-length increases the mechanical performance of the product but reduces the processability of the material. For most nonwoven applications, an optimal balance of the properties can be found at an average cut-length of about 4 mm to about 8 mm.

[0024] The nonwoven material according to another embodiment disclosed herein can have an air permeability in the range of 50 Ls / m 2< to 1000 Ls / m 2< , preferably of 70 Ls / m 2< to 200 Ls / m 2< . Generally, the air-permeability of a nonwoven material can be adjusted in a broad range by changing the main influence factors such as the grammage, the fiber titer, the extend of perforation, the degree of densifying (e.g. by hydroentagling energy or calendaring) and the like. It was found that by adjusting the amount of flat lyocell fibers and / or their properties, such as the cross-sectional aspect ratio, the air-permeability of the nonwoven material can be reproducibly adjusted in a surprisingly broad range. Therefore it is possible to adjust the air-permeability by adjusting the percentage of the flat lyocell fibers and / or their properties, e.g. their cross-sectional aspect ratio and / or their fiber titer and / or their fiber length.

[0025] In one preferred embodiment, the nonwoven material can have a thickness in the range of between 0.02 mm and 2 mm. Very thin nonwoven materials, for example in the range of between 0.02 and 0.08 mm, can, for example, be used for the production of insulation papers and beverage filters, such as coffee filters, teabags, casing paper or the like. Ab bit thicker nonwoven materials, for example in the range of between 0.08 mm and 0.3 mm, can be used, for example for the production of filter media for industrial and automotive applications and wallpaper. Even thicker material can be preferred for other applications, such as padding material for meat packaging.

[0026] In this context, also the production process has an effect on the optimal thickness range. For example, an airlaid process can be optimally used to produce thicker nonwoven materials, e.g. with a thickness in the range of 0.1 mm to 2 mm, preferably from 0.3 to 0.8 mm, whereas wetlaid nonwoven materials can be produced to be very thin, e.g. to have a thickness in the range of 0.02 mm to 0.5 mm.

[0027] The nonwoven material according to one embodiment disclosed herein can comprise supplemental fibers, preferably in a range of between 0 % per weight and 65 % per weight, wherein the supplemental fibers are selected from a group comprising: synthetic fibers, such as polyester fibers, polyethylene fibers, polypropylene fibers, polyamide fibers, elastane fibers, aramid fibers, animal fibers, PLA-fibers or a mixture of two or more of such fibers. The addition of supplemental fibers can be used to achieve very specific and special properties for the nonwoven material.

[0028] Another aspect of the present disclosure pertains to a product comprising a nonwoven material as disclosed herein, wherein the product is selected from the group comprising filter media for beverages, such as tea bags or coffee pods, meat casing paper, automotive or industrial filter media, electrical or insulation papers, security papers, banknote papers, medical papers, packaging papers, food contact papers, food tray absorption layers, wrapping papers, wallpapers, décor or overlay papers, agricultural papers, tobacco papers, tapes, moist toilet tissues, hygienic products, such as pantiliners or sanitary pads. The teachings disclosed herein allow for the production of nonwoven materials with very well adjusted properties that can be accurately adapted to the specific needs of numerous applications.

[0029] In another aspect the present disclosure concerns the use of a nonwoven material disclosed herein for the production of a product, wherein the product is selected from the group comprising filter media for beverages, such as tea bags or coffee pods, meat casing paper, automotive or industrial filter media, electrical or insulation papers, security papers, banknote papers, medical papers, packaging papers, food contact papers, food tray absorption layers, wrapping papers, wallpapers, décor or overlay papers, agricultural papers, tobacco papers, tapes, moist toilet tissues, hygienic products, such as pantiliners or sanitary pads. According to the teachings disclosed herein, the properties of a nonwoven material can be reproducibly and accurately adjusted for a broad range of different applications.

[0030] According to another aspect, the present application discloses a method for the production of a nonwoven material, wherein the method comprises at least the steps of suspending fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the nonwoven material, wherein the nonwoven material comprises from 30 % to 95 % per weight natural plant-based fibers and / or man-made cellulosic fibers and from 5 % per weight to 70 % per weight, preferably from 10 % per weight to 55 % per weight flat lyocell fibers, wherein the flat lyocell fibers are provided with a flat cross section with a cross-sectional aspect ratio of at least 1.8, preferably of at least 4 or even more preferred of at least 6 and wherein the surface of the flat lyocell fibers is free of fibrillation grooves. The method allows for the production of nonwoven materials having specifically adjusted quality parameters in a reproducible way. Negative effects of quality changes of seasonal products, such as Abaca or the like, can be avoided.

[0031] In a preferred embodiment, the method comprises at least one hydroentanglement step and / or at least one calendaring step. The possible range of achievable parameters can be extended even further by using a hydroentanglement step, a calendaring step of a combination of such steps. The processes of hydroentanglement or calendaring are per se known in the art and can therefore easily applied to the nonwovens disclosed herein.

[0032] According to another preferred embodiment of the method disclosed herein, the suspension fluid is a liquid, preferably an aqueous solution or water. Such a method is commonly also known as "wetlaid process" and is especially well-known from the area of paper production. In a wetlaid process, the raw material fibers (in paper production commonly paper pulp is used) is suspended in an aqueous medium, e.g. water, to for a slurry. The slurry can also comprise other fibers, e.g. it is known to add synthetic fibers to the slurry. The slurry is then deposited on a moving permeable screen, where the water is drained to form the nonwoven material. The material is further dewatered, e.g. by pressing between rollers, and dried. It has been found that by combining these well-known techniques with the teachings disclosed herein, nonwoven materials with exceptional properties can be produces.

[0033] According to another preferred embodiment of the method disclosed herein, the suspension fluid can be a gaseous medium, preferably air. Such a method is per-se known in the art as an "airlaid process". The airlaid process can be implemented by feeding the raw-material fibers (which are generally relatively short) into a forming head by an airstream. By air again, a controlled part of the fibre mix leaves the forming head and is deposited on a moving belt, where a randomly oriented web is formed. Compared to the wetlaid process, airlaid webs have a lower density, a greater softness and a higher thickness. Airlaid webs offer great versatility in terms of the fibres and fibre blends that can be used. Further, the airlaid process allows for a very homogeneous mixture of the fibers in case different fiber types are used as the raw-material.

[0034] It has been found, that the use of essentially unfibrillated flat lyocell fibers in a airlaid process allows for the production of nonwoven material with surprising properties. Such nonwovens performed extremely well in a slosh-box-test which indicates a very good flushability of the material. At the same time, the nonwoven had a high wet tensile strength. Such properties are highly desirable for flushable wipes. Therefore, the use of flat fibers in an airlaid process allow for the production of nonwoven materials that could pass most stringent flushability guidelines, such as IWSFG, even with high wet tensile strength.Brief Description of the Figures

[0035] Hereinafter, exemplary embodiments of the invention are described with reference to the drawings, wherein Fig. 1is a microscopic image of flat lyocell fibers free of fibrillation grooves, Fig. 2is another microscopic image of flat, unfibrillated lyocell fibers in a sectional view showing the cross-sections of the fibers, Fig. 3is a microscopic image of flat lyocell fibers that have been subjected to a fibrillation step, Fig. 4is a higher resolution microscopic image of flat lyocell fibers that have been subjected to a fibrillation step and Fig. 5is a microscopic image showing a cross-section of a nonwoven material comprising flat, unfibrillated lyocell fibers and pulp fibers. Detailed description of the Figures

[0036] The microscopic images shown in Fig. 1 and 2 were taken with an electron microscope of the type Phenom Pro X with the software Phenom Pro Suite at a magnification of 500x (Fig. 1) and 650x (Fig. 2).

[0037] The microscopic images shown in Fig. 3, 4 and 5 were taken with an electron microscope of the type FEI Quanta 450 with the software FEI Quanta Microscope Control, v6.2.10, at a magnification of 500x (Fig. 3 and 5) and 1000x (Fig. 4).

[0038] Fig. 1 shows a cluster of flat, unfibrillated lyocell fibers. The fibers have a smooth surface free of any fibrillation grooves which clearly shows that they have not undergone any fibrillation step. Nonetheless, some minor fibrills can be seen as they normally occur on any lyocell fibers. The fibers shown are quite uniform having a width of about 20 - 30 µm and a thickness of about 5-10 µm. In this case, the cross-sectional aspect ratio of the fibres, which is defined as the width to height ratio of a minimum bounding rectangle around the cross section of the fibre, would probably be in the range of 3-4. An exact determination cannot be made from this view but it is known in the art how to assess and measure an average value of the cross-sectional aspect ratio with an adequate accuracy.

[0039] Fig. 2 shows another view of a cluster of flat, unfibrillated lyocell fibers, but this time in a cross-sectional view focused on the fiber-cross-sections. The flat cross-section can be clearly observed in this view. The cross-section differs from one fiber to another, which is also partly due to the cutting angle.

[0040] As a comparison, Fig. 3 shows a cluster of fibrillated flat lyocell fibers. It can be observed that the fibrillation not only produced a high number of fibrills, but also affected the surface of the fibers, which are no longer smooth and even, but show a distinctive pattern of fibrillation grooves.

[0041] In Fig. 4, which shows fibrillated fibers in a higher resolution, the fibrillation grooves can be seen as a pattern of lines running mainly parallelly to the main axis of the fibers.

[0042] Fig. 5 shows a microscopic image of a fiber mixture comprising flat, unfibrillated lyocell fibers and pulp fibers. The pulp fibers show an irregular form and an uneven surface, whereas the lyocell fibers show their typically smooth surface and have a very uniform cross-section.Examples

[0043] Several Samples of nonwoven materials were produced according to the same production method but with different material compositions.Production method

[0044] All nonwoven samples were produced using two different fibrous raw materials, a wood pulp fraction (Canfor) and a fiber fraction (either lyocell fibers, abaca or PSPI). All nonwovens were produced using a Rapid-Köthen Sheet Former (Type RK-2A).

[0045] For all samples the wood pulp was first teared into coarse pieces and left to soak in water for a few minutes at a ratio of approximately 1 / 15. The soaked, softened pulp was then mixed with a propeller mixer at 800-1500 rpm until a homogeneous paste was obtained. The resulting pulp solution was then transferred to a G2 frit and slipped off without applying pressure. The filter cake was then transferred to a large plate, carefully plucked and dried overnight at 60°C in a vacuum drying oven. The dried pulp was finely plucked and conditioned overnight in the laboratory before it was used for further processing.

[0046] The moisture content of the fiber fraction and of the conditioned, dried pulps were determined before they were weighed for sheet production.

[0047] The prepared pulp and fibers were weighed into single sample vails. Distilled water was added to soften the material at least 4 hours before paper manufacturing. Further processing at this stage took place within 2 days maximum.

[0048] For the paper preparation, a whipping beaker was filled with 2 liters of tap water and the precisely weighed pulp was added to the water. The so produced pulp suspension was mixed in the beaker at 3000 rpm for 2 minutes. The beaker was then opened and the previously weighed fibers were added. The beaker was locked again, and mixing procedure was repeated for 15 seconds at 3000 rpm.

[0049] A sieve was placed in the sheet former and tightly closed. The forming process was started. When the water covers the spray nozzles of the leaf former, the entire fine suspension of the beaker (with pulp and fiber mix) were emptied into the leaf former and the stirring cup was quickly rinsed with a spray bottle.

[0050] The sheet former was opened, the sieve with the hand-paper on it was placed in the drying unit and covered with a protective plastic film.

[0051] The drying unit was closed, and vacuum was applied. The round paper was dried for 10 minutes at 90°C.

[0052] For each setup, 10 identical papers were produced.Raw material fibers

[0053] The following fiber types were used for the production of the samples: Lyocell shortcut 8 mm flat ("1.7dtex / 8 mm flat") Aspect ratio of fiber: 3.4. Produced in house (i.e. at Lenzing AG, Austria) in pilot line scale, finished and cut using a laboratory guillotine. Lyocell shortcut 6 mm flat ("1.7dtex / 6mm flat") Aspect ratio of fiber: 3.4. Produced in house in pilot line scale, finished and cut using a laboratory guillotine Lyocell shortcut 8 mm round ("1.7dtex / 6mm round") Produced in house in pilot line scale, finished and cut using a laboratory guillotine. Lyocell shortcut 6 mm round ("1.7dtex / 8mm round") Produced in house in pilot line scale, finished and cut using a laboratory guillotine. Canfor IC90 pulp ("Canfor") Softwood long fiber pulp. Abaca AEU05 ("Abaca") Abaca pulp market sample obtained from Specialty Pulp Manufacturing Inc (SPMI), 358 Quezon Avenue, Quezon City, 1113 Philippines. PSPI 100 pulp ("PSPI") Abaca pulp market sample obtained from Pulp Specialties Philippines Inc (PSPI), 8741 Paseo de Roxas, Makati City, 1200 Philippines. Parameter measurements

[0054] Before taking measurements, all samples were conditioned according to NWSP 003.0.R0 (15).

[0055] On all conditioned samples parameters were measured according to the following protocols: Thickness (THK) - [mm]: Edana Nonwovens Standard Procedure (NWSP) 120.6.R0 (15) [EN] Basis Weight (BW) - [g / m 2< ]: NSWP 130.1.R0(15) [EN] Bulkiness (BULK) - [kg / m 3< ] - was calculated according to the formula: bulk kg / m 3 = basis weight gsm / thickness mm Dry specific tensile strength (Fspec) - [Nm 2< / g]: NWSP 110.4.R0 (15) [EN] Tearing strength (TEAR) - [N / 75mm]: NWSP 100.2.R1 (15) [EN] Ball burst strength (BBURST) - [N / 1.5cm]: NWSP110.5.(15) Air permeability (Perm) - [L*s / m 2< ]: DIN ISO 9237 - 1995 Sample properties

[0056] All samples were produced according to the production method described above. The percentages given in Table 1 below all refer to % per weight of the fiber blend of the raw material fibers. Table 1 - Raw material compositionsSAMPLE PULP FRACTION FIBER FRACTION Sample 1 40% Lyocell shortcut 6 mm flat 60% Canfor IC90 Sample 2 (Comparison)40% Lyocell shortcut 6 mm round60% Canfor IC90Sample 3 (Comparison)40% PSPI 10060% Canfor IC90Sample 4 (Comparison)40% Abaca AEU0560% Canfor IC90Sample 5 30% Lyocell shortcut 8 mm flat 70% Canfor IC90 Sample 6 (Comparison)30% Lyocell shortcut 8 mm round70% Canfor IC90Sample 7 (Comparison)30% PSP 10070% Canfor IC90Sample 8 (Comparison)30% Abaca AEU0570% Canfor IC90 Results and discussion

[0057] Measurement results for the different samples are shown in Table 2 below. Comparison Samples that did not comprise any flat lyocell fibers are marked with (C). Table 2 - Parameter comparison of nonwoven samplesSample code Fiber blend THK [mm] BW [g / m 2< ] BULK [kf / m 3< ] Fspec [Nm 2< / g] TEAR [N / 75mm] BBURST [N / 1.5cm] Perm [Ls / m 2< ] Sample 140% 1.7 / 6 flat0.12433080.250.84.5208E33_23_0668_1460% CanforSample 2 (C)40% 1.7 / 6 round0.14433060.130.52.4350E33_23_0668_1360 % CanforSample 3 (C)40% PSPI0.13473620.2817.677E33_23_0666_1960% CanforSample 4 (C)40% Abaca0.14473380.221.18297E33_23_0668_2160% CanforSample 530% 1.7 / 8 flat0.1333260.220.83.1300E33_23_0666_0770% CanforSample 6 (C)30% 1.7 / 8 round0.11332950.120.41432E33_23_0666_0870% CanforSample 7 (C)30% PSPI0.09313490.210.83.1204E33_23_0666_1870% CanforSample 8 (C)30% Abaca0.11322860.180.82.4157E33_23_0666_2070%Canfor

[0058] The results show that nonwoven materials comprising flat, unfibrillated lyocell fibers (i.e. Samples 1 and 5) show a significantly elevated tensile strength, tearing strength and ball burst strength than the direct comparison samples (Samples 2 and 6, respectively). Further, the results show that nonwoven materials that comprise flat, unfibrillated lyocell fibers show properties that are comparable to state of the art nonwoven materials comprising Abaca (Comparison Samples 4 and 8) or PSP (Comparison Samples 3 and 7).

Examples

examples

Examples

[0043]Several Samples of nonwoven materials were produced according to the same production method but with different material compositions.

Production method

[0044]All nonwoven samples were produced using two different fibrous raw materials, a wood pulp fraction (Canfor) and a fiber fraction (either lyocell fibers, abaca or PSPI). All nonwovens were produced using a Rapid-Köthen Sheet Former (Type RK-2A).

[0045]For all samples the wood pulp was first teared into coarse pieces and left to soak in water for a few minutes at a ratio of approximately 1 / 15. The soaked, softened pulp was then mixed with a propeller mixer at 800-1500 rpm until a homogeneous paste was obtained. The resulting pulp solution was then transferred to a G2 frit and slipped off without applying pressure. The filter cake was then transferred to a large plate, carefully plucked and dried overnight at 60°C in a vacuum drying oven. The dried pulp was finely plucked and conditioned overnight in the laboratory befo...

Claims

1. Nonwoven material produced by a method comprising at least the steps of suspending fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the nonwoven material, wherein the nonwoven material comprises from 30 % to 95 % per weight natural plant-based fibers and / or man-made cellulosic fibers and from 5 % per weight to 70 % per weight, preferably from 10 % per weight to 55 % per weight flat lyocell fibers, wherein the flat lyocell fibers are provided with a flat cross section with a cross-sectional aspect ratio of at least 1.8, preferably of at least 4 or even more preferred of at least 6 and wherein the surface of the flat lyocell fibers is free of fibrillation grooves.

2. Nonwoven material according to Claim 1, wherein the nonwoven fiber fleece has a dry specific tensile strength (Fmax) of at least 0.15 Nm2 / g, preferable of at least 0.18 Nm2 / g or even more preferred of at least 0.2 Nm2 / g.

3. Nonwoven material according to Claim 1 or 2, wherein the nonwoven material has a ball burst strength of at least 2.5 N / 1.5 cm, preferable of at least 3 N / 1.5cm and most preferred of at least 3.5 N / 1.5 cm.

4. Nonwoven material according to any of the Claims 1 to 3, wherein the nonwoven material has a tearing strength of at least 0.5 N / 75mm.

5. Nonwoven material according to any of the Claims 1 to 4, wherein the nonwoven material is produced by a method comprising at least one hydroentanglement step and / or at least one calendaring step.

6. Nonwoven material according to any of the Claims 1 to 5, wherein the flat lyocell fibers have an average cut-length in the range of 2 mm to 20 mm, preferably of 3 mm to 12 mm.

7. Nonwoven material according to any of the Claims 1 to 6, wherein the nonwoven material has an air permeability in the range of 50 Ls / m2 to 1000 Ls / m2, preferably of 70 Ls / m2 to 200 Ls / m2.

8. Nonwoven material according to any of the Claims 1 to 7, wherein the nonwoven material has thickness in the range of between 0.02 mm and 2 mm.

9. Nonwoven material according to any of the Claims 1 to 8, wherein the nonwoven material comprises supplemental fibers, preferably in a range of between 0 % per weight and 65 % per weight, wherein the supplemental fibers are selected from a group comprising: synthetic fibers, such as polyester fibers, polyethylene fibers, polypropylene fibers, polyamide fibers, elastane fibers, aramid fibers, animal fibers, PLA-fibers or a mixture of two or more of such fibers.

10. Product comprising a nonwoven material according to any of the Claims 1 to 9, wherein the product is selected from the group comprising filter media for beverages, such as tea bags or coffee pods, meat casing paper, automotive or industrial filter media, electrical or insulation papers, security papers, banknote papers, medical papers, packaging papers, food contact papers, food tray absorption layers, wrapping papers, wallpapers, décor or overlay papers, agricultural papers, tobacco papers, tapes, moist toilet tissues, hygienic products, such as pantiliners or sanitary pads.

11. Use of a nonwoven material according to any of the Claims 1 to 9 for the production of a product, wherein the product is selected from the group comprising filter media for beverages, such as tea bags or coffee pods, meat casing paper, automotive or industrial filter media, electrical or insulation papers, security papers, banknote papers, medical papers, packaging papers, food contact papers, food tray absorption layers, wrapping papers, wallpapers, décor or overlay papers, agricultural papers, tobacco papers, tapes, moist toilet tissues, hygienic products, such as pantiliners or sanitary pads.

12. Method for the production of a nonwoven material, wherein the method comprises at least the steps of suspending fibers in a liquid or gaseous suspension fluid and laying-down the fibers to form the nonwoven material, wherein the nonwoven material comprises from 30 % to 95 % per weight natural plant-based fibers and / or man-made cellulosic fibers and from 5 % per weight to 70 % per weight, preferably from 10 % per weight to 55 % per weight flat lyocell fibers, wherein the flat lyocell fibers are provided with a flat cross section with a cross-sectional aspect ratio of at least 1.8, preferably of at least 4 or even more preferred of at least 6 and wherein the surface of the flat lyocell fibers is free of fibrillation grooves.

13. Method according to Claim 12, wherein the method comprises at least one hydroentanglement step and / or at least one calendaring step.

14. Method according to Claim 12 or 13, wherein the suspension fluid is a liquid, preferably an aqueous solution or water.

15. Method according to Claim 12 or 13, wherein the suspension fluid is a gaseous medium, preferably air.

Images