Patent Application
20250034768
This application claims priority to and the benefit of European Patent Application No. 23187168.2, filed Jul. 24, 2023, the entirety of which is incorporated by reference herein.
The present invention relates to a nonwoven fabric as well as to a method for producing the nonwoven fabric.
Nonwovens are widely used for various products, such as wipes, both as dry wipes and wet wipes. In such uses, softness of the material is a desired property. Typically, soft nonwovens are obtained by using fibres made with the lyocell-process, either in a mixture with other fibres or alone. Such fibres are however rather costly, which is undesired in single use applications, such as in cleaning wipes.
It is thus an aim of the present disclosure to provide a nonwoven fabric that has a desired softness while being less expensive than existing fabrics with similar softness. Another aim is to provide a method for producing such nonwoven fabric.
The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.
According to a first aspect, there is provided a nonwoven fabric consisting of viscose fibres, the viscose fibres comprising:
According to another aspect, there is provided method for producing a nonwoven fabric consisting of viscose fibres, the method comprising the steps of:
In the present description, biodegradable material is a material that can be broken down by bacteria so that it can be consumed by the environment. The degradation products are thus harmless. A typical degradation time is from a few weeks to a few years. Biodegradation has been defined for nonwoven materials and can be tested for example using EN 14995:2006. The term man-made fibre in this description is used in the sense that it comprises all chemically produced fibres to distinguish them from the truly natural fibres such as cotton, wool, silk, flax etc. Thus, it encompasses for example fibres made from polymers synthesised from chemical compounds, e.g. acrylic, nylon, polyester, polyethylene, polyurethane, and polyvinyl fibres, modified or transformed natural polymers, e.g. alginic, and cellulose based fibres such as acetates, viscose, lyocell and rayon.
In the present description, the terms nonwoven fabric and nonwoven can be used interchangeably. The unit den (denier) is a direct measure of linear density, given as grams per 9000 metres of yarn. The unit dtex (deci-tex) is also a direct measure of linear density, given as grams per 10000 metres of yarn. The fibres are stable fibres and hence all have the indicated length, within a small error margin due to the cutting of the fibres. Weight percentages (wt-%) are to the total weight of the nonwoven or the mixture of fibres, as case may be.
The present description relates to a nonwoven fabric comprising fibres, the fibres of the nonwoven fabric consisting of viscose fibres, the viscose fibres comprising:
As is shown below in the Experimental part, the softness of the present nonwoven fabric is similar to the softness of a nonwoven fabric containing lyocell-fibres, while other properties are also within the same range. This is believed to be due to the use of the present, rather low, linear density, leading to a higher number of individual fibres per square meter. This leads to a feeling of increased softness. Another advantage of the present nonwoven fabric is also that less energy is needed during hydroentanglement, to obtain sufficient strength, which makes the fabric more sustainable. Indeed, the use of finer fibres in larger number than in comparable products, leads to more binding points (i.e. points where the fibres have entangled with each other), leading to the requirement of less energy for the same strength. The high number of binding points is also believed to contribute to the increased softness of the fabric. The use of two different types of viscose fibres, i.e. viscose fibres having different linear densities, further optimises the softness and strength.
The present nonwoven fabric thus comprises 40-60 wt-% of viscose fibres having a linear density of 1.6-1.8 dtex and a length of 38-42 mm. The linear density and length may be independently selected within these ranges. The linear density can be for example from 1.6 or 1.7 up to 1.7 or 1.8 dtex. The length of this size of viscose fibres can be for example from 38, 39, 40, or 41 mm up to 39, 40, 41, or 42 mm.
The present nonwoven fabric also comprises 40-60 wt-% of viscose fibres having a linear density of 0.9-1.4 dtex and a length of 38-42 mm. The linear density and length may be independently selected within these ranges. The linear density can be for example from 0.9, 1.0, 1.1, 1.2 or 1.3 up to 1.0, 1.1, 1.2, 1.3 or 1.4 dtex. The length of this size of viscose fibres can be for example from 38, 39, 40, or 41 mm up to 39, 40, 41, or 42 mm.
According to an embodiment, the viscose fibres comprise:
According to an embodiment, the present nonwoven fabric consists of 50 wt-% of viscose fibres having a linear density of 1.6-1.8 dtex and 50 wt-% of viscose fibres having a linear density of 1.2-1.4 dtex. According to another embodiment, the present nonwoven fabric consists of 50 wt-% of viscose fibres having a linear density of 1.7 dtex and 50 wt-% of viscose fibres having a linear density of 1.3 dtex.
The nonwoven fabric may also comprise other viscose fibres than those listed above, up to a maximum of 20 wt-%, i.e. fibres having a linear density different from 0.9-1.4 and 1.6-1.8 dtex and/or a length different from 38-42 mm. Preferably, the linear density is different from 0.9-1.4 and 1.6-1.8 dtex.
According to an embodiment, the nonwoven fabric has a dry softness value of 0.4-0.7 N/10 cm and a wet softness value of 0.3-0.5 N/10 cm the softness values being measured using a sample of 160×180 mm attached at its central point to a mounting clip, which mounting clip is attached to a machine used for measuring friction factors according to ISO 8295:1995, which samples are thereafter drawn using a speed of 1000 mm/minute and force as in ISO 8295:1995, through an opening in a test plate, which opening has a stadium shape with a size of 45×15 mm with ends having a radius of 7.5.
In the test for softness, the mounting clip is attached to a wire, and the wire is attached to the same attachment point of the load cell as the sledge in the friction factor test according to ISO 8295:1995. The wire is non-extensible, as in test according to ISO 8295:1995. When test results are given for a wet nonwoven fabric, the fabric is wetted using Tergitol™ in a concentration of 0.1% aqueous solution, used in an amount of 3 g/g of nonwoven fabric. The samples (size as indicated above) are cut, arranged on a pile and weighted. The wetting solution is evenly applied on the pile using a pipette. The wetted pile is arranged in a plastic bag, which is hermetically closed. Thereafter, the plastic bag is rolled over to ensure that all samples are evenly wetted. Thereafter, the samples are kept in the plastic bag and stored overnight.
According to another aspect, there is provided a method for producing a nonwoven fabric consisting of viscose fibres, the method comprising the steps of:
The present method comprises the step of carding the fibres and forming a web of fibres on a wire support. The mixture of fibres is preferably prepared prior to the carding, although it is also possible to feed the different types of fibres onto the wire support separately. It is also possible to make layered structures, for example by feeding at least one layer from one carding device. Furthermore, it is also possible to add for example an airlaid or unwind layer between, on top or below one or more carded layers.
Carding separates the fibres and removes any possible impurities, while at the same time aligns and delivers them to be laid down as a web. The fibres in the web are thus aligned with each other predominantly in the same direction, which is mainly the machine direction. Furthermore, it is possible to use a randomizer as part of the card, which turns the fibres more into a cross direction of the web, leading to a higher strength in the cross direction. The fibres may also be randomly oriented in several directions. Further, it is also possible to use a so-called TT card, for example an eXcelle™ TT card by Andritz.
Instead of carding, the web can be formed by a wetlaid process.
After carding, the formed web is hydroentangled. Hydroentanglement is a method of bonding a web of fibres by entangling them by using high-pressure, columnar water jets. As the jets penetrate the web, fibre segments are carried by the highly turbulent fluid and become entangled with each other on a semimicro scale. In the present method, hydroentangling is carried out in the absence of any other component, such as a binder.
The hydroentanglement uses at least a first and a second hydroentangling unit, wherein a cumulative hydroentanglement energy in the first hydroentangling unit is lower than the cumulative hydroentanglement energy in the second hydroentangling unit. The method may further comprise using a third hydroentanglement unit. The optional third hydroentanglement unit may be used for patterning purposes.
Moreover, the units may be located on either side of the web, or the web may be turned such that the water jets are directed to the web from both sides of the web. In one embodiment, a first unit is located above the web, a second below the web and a third unit again above the web. Directing the hydroentanglement water jets from two opposite directions leads to even further improved properties of the finished nonwoven fabric. In one embodiment, the web, at the hydroentangling units, are not in contact with the wire support but rather, in contact with a drum against which the hydroentangling is carried out.
According to an embodiment, the hydroentanglement energy at the first unit is 30-40% of the total hydroentanglement energy and the hydroentanglement energy at the second unit is 60-70% of the total hydroentanglement energy.
According to one embodiment, the hydroentanglement energy per injector at the first unit is 40-50 kW·h/ton of water and at the second unit 70-90 kW·h/ton. In case a third unit is used after the second unit, the hydroentanglement energy per injector at the third unit is typically lower than at the second unit. Furthermore, in case hydroentanglement in carried out on both sides of the web, typically 40-60% of the cumulative energy is used on both sides, i.e. the cumulative energy from one side is close to the cumulative energy from the other side. The quantity of energy used at different units can of course be different from the above. The cumulative energy used at the first unit is typically in the order of 20-30% of the total energy used and the cumulative energy used at the second unit is typically in the order of 40-50% of the total. In case of only two units, the cumulative energy at the first unit is about 30-40% of the total and the cumulative energy at the second unit is about 60-70% of the total energy used. By cumulative energy is here meant the combined energy of the injectors of the unit. Indeed, each unit comprises typically 1-5 injectors, which extend over the width of the web. Each injector has a strip having a large number of nozzles, typically in the hundreds.
The method may further comprise additional steps after dewatering and drying, such as calendaring the dried web, slitting it and/or winding it. The method may also comprise some additional steps in the beginning, such as pre-wetting the fibres after carding and before hydroentangling, to enhance the hydroentangling and compressing the web. In case pre-wetting is used, the cumulative energy is in the order of 1-2% of the total energy in the process (including hydroentanglement and drying). The purpose of pre-wetting is thus to compact the fluffy fibre web, remove the air in the web, and effectively absorb the energy of water jet, so as to enhance the fibre entanglement effect.
According to yet another embodiment, the present description relates to a nonwoven fabric obtainable by the method described above. The various embodiments and variants disclosed above in connection with the method apply mutatis mutandis to the nonwoven fabric.
The present nonwoven fabrics may be used for example in baby wipes, cosmetic wipes, perinea wipes, disposable washcloths, kitchen wipes, bath wipes, hard surface wipes, glass wipes, mirror wipes, leather wipes, electronics wipes, disinfecting wipes, surgical drapes, surgical gowns, wound care products, protective coveralls, sleeve protectors, diapers and incontinent care and feminine care articles, nursing pads, air filters, water filters, oil filters, furniture or upholstery backing.
In the following Experimental part, some examples are given to further illustrate the invention.
Different fibres and fibre mixtures were tested and the manufactured nonwoven fabrics were tested and compared each other.
The fibres used were:
The production line was as illustrated in
The nonwoven fabric according to the present invention, Fabric 1, consisted of 50 wt-% of viscose fibres 1 and 50 wt-% of viscose fibres 2. Two comparative nonwoven fabrics were also prepared, Comparative fabric 1 consisting of only viscose 1 fibres and Comparative fabric 2 consisting of 50 wt-% of viscose fibres 1, 40 wt-% of viscose fibres 2 and 10 wt-% of lyocell-fibres.
The obtained nonwoven fabrics were submitted to several tests. The following tests were carried out. For most of the tests, from six to twelve parallel samples were tested and the results given as a numerical average of the parallel results. Results of the tests are given in Table 1 below. MD stands for machine direction, CD for cross direction.
When test results are given for a wet nonwoven fabric, the fabric was wetted using Tergitol™ 15-S-9 from Acros organics, in a concentration of 0.1% aqueous solution, used in an amount of 3 g/g of nonwoven fabric. The samples (size as indicated for each test) were cut, arranged on a pile and weighted.
Application of the Tergitol™-solution was carried out slightly differently depending on the test. For the tests where the samples were drawn (i.a. tensile strength, elongation), a pile of samples was arranged in a container, and Tergitol™-solution was poured over the pile, in an amount sufficient to wet the samples. After one hour, the pile of samples was removed from the container, extra solution is carefully removed by squeezing the samples and further by pressing between dry sheets of fabric.
For the test on wet friction and wet softness, the wetting solution was evenly applied on the pile using a pipette. The wetted pile was arranged in a plastic bag, which was hermetically closed. Thereafter, the plastic bag was rolled over to ensure that all samples are evenly wetted. Thereafter, the samples were kept in the plastic bag and stored overnight.
For the test on wet thickness, the samples (10×10 cm), with a total weight of at least 1 g, were immersed in distilled water for one minute, while being attached to a mesh, thereafter the samples were let drip dry during 2 minutes. Thus, in this test, no Tergitol™-solution was used, only distilled water.
The basis weight in g/m2 of the nonwoven fabric was measured using the method NWSP 130.1.R0 (20).
The thickness in mm of the nonwoven fabric was measured using the method NWSP 120.6.R0 (15).
The dry bulk and the wet bulk in m3/g of the nonwoven fabric was determined by calculating the dry thickness divided by basis weight multiplied by 1000 (dry thickness/basis weight*1000).
The tensile strength in both machine direction (MD) and cross direction (CD) for dry and wet nonwoven fabric, in N/5 cm was measured according to NWSP 110.4.R0 (20).
The maximum elongation in % in both machine direction (MD) and cross direction (CD) for dry and wet nonwoven fabric was measured according to NWSP-110.4.R0 (20).
The absorption capacity (in g/g) with water of the nonwoven fabric was measured according to NWSP 010.1.R0 (20) and EN 1644-1:1997, with the exception that the samples are not conditioned for 24 hours prior to testing and the test is not carried out in a room with standard humidity.
The bending length (in mm) in both machine direction (MD) and cross direction (CD) and for both sides of the nonwoven fabric was measured according to SFS-EN ISO 9073-7:1998 and NWSP 090.5.R0 (20), with the exception that the samples were not conditioned prior to testing.
The Atlas pilling (in %) of the nonwoven fabric was measured according to the standard SFS 3378:2002.
The softness value in N/10 cm for dry and wet nonwoven fabric was measured using a sample of 160×180 mm (160 mm in MD, 180 mm in CD) attached at its central point to a mounting clip, which mounting clip is attached to a machine used for measuring friction factors according to ISO 8295:1995, which samples are thereafter drawn using a speed of 1000 mm/minute and force as in ISO 8295:1995, through an opening in a test plate, which opening has a stadium shape with a size of 45×15 mm with ends having a radius of 7.5.
Table 1 gives the results for the different nonwoven fabrics.
Concerning the softness-measurements, the Comparative fabric 1 is not comparable to Fabric 1 and Comparative fabric 2, due to the thickness difference. The difference in thickness between Comparative fabric 1 and Fabric 1 is almost the double of the difference in thickness between Comparative fabric 2 and Fabric 1. This difference in thickness also influences the bending length values.
When comparing Fabric 1 and Comparative fabric 2 (containing lyocell-fibres), it can be seen that similar results are obtained for the softness values. The present material thus achieves the softness that is typically obtained only with the use of lyocell-fibres. The other properties are either similar or within acceptable ranges.
It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.
Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention.
The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of “a” or “an”, i.e. a singular form, throughout this document does not exclude a plurality.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23187168.2 | Jul 2023 | EP | regional |
