ELASTIC NON-WOVEN SHEET

Abstract

The invention relates to elastically stretchable nonwoven sheets comprising an elastically stretchable nonwoven layer and a stretchable facing layer, and to an online method for manufacturing such sheets.

Description

[0001] The invention relates to elastically stretchable nonwoven sheets comprising an elastically stretchable nonwoven layer and an opposing stretchable nonwoven layer, and an online method for manufacturing such sheets.

[0002] Nonwoven sheets are used in the hygiene industry as materials for manufacturing baby diapers and adult incontinence products on a large scale. However, in many cases, for example, to manufacture ear flaps in open diapers or waistband sections in diaper pants, elastically stretchable materials are required, and standard nonwoven sheets do not meet that requirement.

[0003] Traditional approaches to addressing the problem of limited elastic stretch in nonwoven sheets involve incorporating an elastic film between layers of nonwoven material. The resulting laminates may have good elastic performance, but the elastic films are not air-permeable, which can cause discomfort to the wearer. Another approach involves incorporating elastic yarns, commonly referred to as Lycra yarns, into the sheets. The drawback of this method is a localized elastic force, which can also cause discomfort to the wearer, and a tendency for the yarns to break during production.

[0004] Furthermore, the incorporation of an elastic film or yarn makes the sheets elastic, but only within the limits of the maximum stretch of the nonwoven materials associated with the elastic film or yarn. Most traditional nonwoven materials have elongation at break values ​​of around 50–80% in the machine direction (MD) and 70–100% in the cross-machine direction (CD) (WSP 110.4) at most, and usually even less, meaning that they only stretch to a very limited degree before they are destroyed. However, for the applications specified above, the sheets would be required to stretch elastically to 150% of their original dimension (up to 250% of their original dimension), and, depending on the specific application, this requirement may apply to stretch in either the cross-machine or machine direction.For example, to make a traditional open or tape-fastened baby diaper, typical production processes require that the material used for the back tab exhibit an elastic stretch of that magnitude in CD. On the other hand, to manufacture adult or baby diaper pants, typical production processes require that the material used for elastic applications, such as waistbands, exhibit an elastic stretch of that magnitude in MD.

[0005] The traditional approach to addressing the problem of limited stretch in nonwoven materials is to pleat the nonwoven sheets by laminating them to the elastic film or yarn. In this way, the lack of extensibility of the nonwoven material itself is compensated for by storing additional material in each pleat. The disadvantage of pleating, however, is the need for more material during production and the increased thickness of the final product, which is perceived negatively by the consumer due to increased thermal insulation and a more visible appearance.

[0006] The most recent approaches use inherently elastically stretchable nonwoven materials. These sheets ultimately comprise a facing layer of stretchable but not very elastic nonwoven material and an elastic nonwoven layer.

[0007] WO 2020 / 187540 A1 describes an offline process for producing such an elastically stretchable nonwoven sheet. The method comprises using a prefabricated facing layer formed from crimp fibers and depositing elastic fibers onto it in a spunbond process to form a spunbond elastic layer. The sheet is then pre-stretched on a pair of corrugated rollers. The resulting products can be elastically stretched to 150% or more of their original dimension in CD, to the extent that they meet industry requirements, but elastic stretch in MD has proven to be more limited. The potential for achieving higher MD stretches is limited for the offline process because prefabricated facing layers have been shown to lose much of their stretchability when they pass through a production line a second time.

[0008] EP 3 715 517 A1 describes an online process for producing elastically stretchable nonwoven sheets. The method uses a multi-beam spunbond line to manufacture a sheet comprising stretchable facing layers formed from crimp fibers and an elastic layer formed from elastic fibers on the same line before bonding by calendering and pre-stretching the materials. The products resulting from this process have shown satisfactory CD stretchability, but fall short in MD stretchability.

[0009] Therefore, there is still a need in the hygiene industry for nonwoven sheets that have a greater inherent ability to stretch elastically in the machine direction.

[0010] In this context, the present invention proposes an elastically stretchable nonwoven sheet comprising at least two layers of nonwoven materials, wherein one layer is an elastically stretchable nonwoven fabric comprising spun elastic fibers formed from a thermoplastic elastomer polymer material, wherein one layer is a stretchable facing layer comprising spun multicomponent crimp fibers, wherein the adjacent layers are joined together by stamped joining points, and wherein at least one of the components of the multicomponent crimp fibers is a propylene-α-olefin copolymer material.

[0011] Compared to the nonwoven sheets described in EP 3 715 517 Al, which use polypropylene for both components of the two-component facing fibers, bblrC Ln / Zznz / E / YIAI, the use of a propylene-to-olefin copolymer (co-PP) in at least one of the two-component fiber components surprisingly leads to a significant increase in the overall elasticity of the sheet, especially in the machine direction (MD). Specifically, target elongation at break values ​​of more than 150%, preferably more than 200%, have been achieved when measured in accordance with WSP 100.4 for such sheets in MD.

[0012] The sheets according to the invention preferably exhibit beneficial elastic behavior, especially in the machine direction.

[0013] In one embodiment, the permanent deformation in the machine direction measured in accordance with ASTM D5459 after the first cycle is less than 15%, preferably less than 10%, more preferably less than 5%.

[0014] In one embodiment, the area between the increasing and decreasing directional stress-strain curves of a hysteresis chart on a second cycle of an ASTM D5459 test, as expressed in the relative size of the area between the curves (A) in relation to the total area under the initial increasing curve (A+B), expressed as % [A / (A+B)xl00|, is less than 40%, preferably less than 30%.

[0015] The two or more components of two-component fibers are arranged asymmetrically over the fiber's cross-section. In a preferred embodiment, multicomponent fibers are two-component fibers. A standard and in many cases preferred option is side-by-side two-component fibers, but the inventive concept is not limited to side-by-side fibers and can also be achieved with other cross-sections such as, for example, core-sheath-eccentric.

[0016] The nonwoven materials of both the facing layer and the elastic layer are spunbond nonwoven materials, and the nonwoven sheet is preferably as a whole a spunbond nonwoven sheet.

[0017] The α-olefin that jointly forms the copolymer with propylene is preferably ethylene. In other words, the copolymer is preferably a poly(propylene-ethylene) copolymer. Also, preferably, the copolymer is a random copolymer.

[0018] The comonomer content in the propylene-α-olefin copolymer, or the ethylene content in the poly(propylene-ethylene) copolymer, is preferably >1% by weight, more preferably >2% by weight. As an upper limit, the comonomer content may be <8% by weight, preferably <6% by weight.

[0019] The other component of the multicomponent crimp fiber is preferably a polypropylene (PP) homopolymer. It is understood herein that a polypropylene homopolymer has a monomer purity greater than 99.5% by weight, preferably greater than 99.8% by weight, and more preferably greater than 99.9% by weight. bblrC Ln / Zznz / E / YILI

[0020] It has been experimentally demonstrated that the use of two-component fibers using polypropylene as one component and a poly(propylene-ethylene) copolymer as the other component leads to a marked increase in MD stretch.

[0021] In another preferred embodiment, the molecular weight distribution, expressed by the polydispersity (Mw / Mn), of the propylene-α-olefin copolymer is wider than the molecular weight distribution of the other components of the crimped multicomponent fibers, preferably the polypropylene homopolymer used in the other component of the two-component fiber.

[0022] In terms of concrete numbers, the difference in Mw / Mn between the two polymers is preferably >1, very preferably >2, and most preferably >3. On the other hand, the difference in Mw / Mn between the two polymers is preferably <10 and preferably <8. Suitable absolute numbers for Mw / Mn can vary, for example, from 2.5 to 7.5 for polypropylene and from 4 to 10 for the propylene-α-olefin copolymer.

[0023] The co-PP or homo-PP of the multicomponent fiber components may be mixed with additional polymers or other additives such as slip agents, filler materials or color masterbatches, but they must represent more than 50% by weight of the respective component, preferably more than 75% and more preferably more than 90%.

[0024] Within two-component crimp fibers, the weight ratio of the coPP component to the other component, preferably the homo-PP component in two-component fibers, is preferably between 20 / 80 and 80 / 20, more preferably between 30 / 70 and 70 / 30, and even more preferably between 40 / 60 and 60 / 40.

[0025] The thermoplastic elastomer material formed for elastic fibers may comprise a thermoplastic polyolefin elastomer (TPE-o), preferably a thermoplastic polyolefin elastomer comprising propylene-to-olefin copolymers. TPE-o materials suitable for use in the context of the present invention are described in EP 2 342 075 A1. Alternatively or in addition, i.e., as a blend, other thermoplastic elastomer materials, such as especially thermoplastic polyurethanes (TPU) or stretch-block copolymers (TPE-s), may be used. In one embodiment, up to 20% by weight, and preferably up to 10% by weight, of a thermoplastic olefin, such as a homopolypropylene, may be contained in the thermoplastic elastomer material along with the thermoplastic elastomer. Additives such as fillers, slip agents, or color master batches can also be added.In one embodiment, a two-component elastic fiber can be formed from two different thermoplastic elastomers, arranged, for example, in a side-by-side or core-sheath configuration.

[0026] The elastic and coating layers of the sheet may comprise elastic or two-component fibers as defined respectively, in addition to other fibers, but preferably bfrlrC Ln / Zznz / E / YIAI consist of elastic or two-component fibers as defined.

[0027] In one embodiment, the sheet comprises at least one facing layer on each side of the elastic layer and, therefore, at least three layers in total. This configuration is advantageous for covering the inherently sticky elastic layer on both sides.

[0028] In some configurations, the additional facing layer can be set up as described above for the first facing layer. The facing layers on different sides of the elastic layer can be the same, but they can also be different. For example, one of the nonwoven facing layers can be a spunbond nonwoven fabric and the other nonwoven facing layer can be a different spunbond nonwoven fabric or a meltblown nonwoven fabric.

[0029] The basis weight of each facing layer may be between 5 and 40 g / m2, preferably between 5 and 40 g / m2, very preferably between 10 and 25 g / m2 and most preferably between 15 and 20 g / m2. The basis weight of the elastic layer may be between 10 and 140 g / m2, preferably between 20 and 120 g / m2 and most preferably between 25 and 100 g / m2.

[0030] The sheets normally comprise a pattern of macroscopic bonding points. In a preferred embodiment, the number of bonding points per cm2 of tissue surface may be less than 100 and preferably less than 80 and, on the other hand, preferably greater than 20. The total area of ​​the tissue surface occupied by the bonding points per area in one embodiment is less than 18% and preferably less than 15%, meaning that the bonding pattern is preferably relatively open.

[0031] In one embodiment, although the sheets of the invention already have an inherently high machine-direction stretching capacity, the sheet can be further activated by machine-direction pre-stretching as described in more detail below.

[0032] The invention further proposes a method for manufacturing an elastically stretchable nonwoven sheet according to the invention, comprising the following in-line steps: (a1) spinning crimped multicomponent fibers, wherein at least one of the components of the crimped multicomponent fibers is a propylene-α-olefin copolymer, and placing them on a rotating moving belt to form a fabric; (a2) spinning elastic fibers formed from a thermoplastic elastomer polymer material and laying them on the surface of the fabric formed in step (a1) to form another fabric; (b) joining the adjacent fabrics to form the elastically stretchable spunbond nonwoven sheet.

[0033] The spinning in steps (a1) and (a2) involves extruding, rapidly cooling, and stretching the fibers in a spunbond machine. The fibrous fabrics formed in steps (a1), etc., are unbonded precursors of the nonwoven materials formed for the facing and elastic layers, respectively, of the nonwoven sheet after the bonding step (b).

[0034] The joining in step (b) is most preferably embossed. Specifically, the joining may comprise embossing of the joining points on the sheet, wherein the embossing is carried out by means of embossing projections arranged on the surface of at least one calender cylinder. The embodiments comprise ultrasonic joining, wherein ultrasonic vibrations are introduced into the embossing projections. Other embodiments use thermal joining, wherein the embossing projections are heated.

[0035] In a preferred variant, the number of bonding points per cm2 of fabric surface may be less than 100. The total area of ​​the fabric surface occupied by the bonding points is preferably less than 18% and more preferably less than 15%, which means that the bonding pattern is relatively open.

[0036] In one embodiment, the method further comprises a step (a3) ​​of spinning additional fibers, preferably multicomponent crimp fibers, wherein very preferably at least one of the components of the multicomponent crimp fibers is a propylene-α-olefin copolymer, and placing them onto the surface of the fabric formed in step (a2) to form a further fabric. In this embodiment of the method, sheets are provided according to preferred embodiments of the invention, having a sandwich structure of an elastic layer interposed between two facing layers.

[0037] In one embodiment, the method further comprises pre-compaction of the facing layer fabric(s). Preferably, there is a pre-compaction step after each corresponding step, i.e., step (a1) and, if applicable, step (a3). The pre-compaction preferably comprises passing the fabric(s) between two flat pre-compaction rollers. The applied linear pressure is preferably between 3-5 N / mm. The roller temperature can be between 50 and 110°C and more preferably between 60 and 100°C. Due to the inherent stickiness of the fibers formed from thermoplastic elastomers, pre-compaction is neither necessary nor feasible after step (a2).

[0038] In one embodiment, the method further comprises a step (c) of pre-stretching the sheet in the machine direction.

[0039] Pre-stretching in the machine direction can be carried out, for example, by pulling the material in the machine direction over sets of rollers with different speeds.

[0040] Another option for performing a pre-stretch in the machine direction comprises mechanically activating the sheet in a mill comprising a pair of interacting rollers whose surfaces comprise interlocking annular ribs and grooves (ring rolling) or interlocking transverse ribs and grooves.

[0041] The pre-stretching in the machine direction of step (c) can be carried out in-line or, alternatively, as a separate process.

[0042] The extent of prestretching of the sheet in the machine direction during step (c) can influence the degree to which the final sheet can be elastically stretched in the machine direction. In one embodiment, during step (c), the sheet is prestretched in the machine direction. The degree of prestretching in the machine direction can be such that, for example, the sheet is stretched by 40-160%, preferably 60-140%, and more preferably 80-120% of its original dimension.

[0043] In an alternative embodiment, the method is devoid of pre-stretching in the machine direction. Due to the particular choice of polymers in the two-component fibers, pre-stretching in the machine direction may not even be necessary to obtain suitable machine-direction stretch properties, unlike materials of the prior art.

[0044] The invention is not limited to a sheet of two or three layers. There may be more than three layers by having an additional elastic layer or additional facing layers or inelastic layers. Also, within each layer, there may be two or more sublayers of identical or similar type formed by separate stages of fiber laying in the production process.

[0045] Nonwoven sheets according to the invention are particularly suitable for use in the manufacture of hygiene articles. For example, nonwoven sheets can be used for the manufacture of a diaper comprising the sheet as an elastic waistband material. Typical production processes currently employed in the industry for that application would require the material to be elastically stretchable in MD.

[0046] Further details and advantages of the invention will become apparent from the figures and examples described below. The figures show:

[0047] Figure 1: a schematic cross section of an elastically stretchable nonwoven sheet according to the invention.

[0048] Figure 2: An exemplary machine configuration for carrying out a method of the invention.

[0049] Figure 3: A schematic illustration of a unit for activating, by stretching in the machine direction, the sheet.

[0050] Figure 4: A schematic illustration of a unit of Figure 3 in operation.

[0051] Figure 5: MD (stress-strain) tensile curves of an isolated face spinning bond layer according to a comparative configuration.

[0052] Figure 6: MD (stress-strain) tensile curves of an isolated facing spindle bonding layer according to an inventive configuration.

[0053] Figure 7: An MD (stress-strain) tensile curve of another isolated facing spindle bonding layer according to an inventive configuration.

[0054] Figure 8: A tensile MD (stress-strain) curve of an isolated elastic bblzC Ln / Zznz / E / YIAI spunbond nonwoven layer.

[0055] Figure 9: MD tensile (stress-strain) curves superimposed on a sheet according to the invention, an isolated facing layer of the sheet and an isolated elastic layer of the sheet.

[0056] Figure 10: A schematic illustration of a tensile (stress-strain) diagram and increasing and decreasing curves of subsequent stress-strain cycles, representing the ASTM D5459 standard tests.

[0057] Figure 11: Tensile (stress-strain) graph in the machine direction for Sample 5-1 of Example 5, showing a hysteresis curve for this material.

[0058] Figure 1 shows a schematic cross-section of an elastically stretchable nonwoven sheet 100 according to the invention, wherein an elastic nonwoven layer comprising elastic fibers 130 is sandwiched between the first and second facing nonwoven layers 120.

[0059] Figure 2 shows an example of a machine configuration for manufacturing an elastically stretchable nonwoven sheet 100 according to the invention.

[0060] The installation comprises one conveyor belt 10 and three yarn joining machines 20, 30 and 40 arranged in a line on the conveyor belt.

[0061] In each of the spun bonding machines, a molten thermoplastic polymer is extruded through the holes of a die. The extracted fiber strands are then rapidly cooled and pulled / stretched to form endless fibers, which are then placed onto conveyor belt 10 or onto a belt that has been previously laid down on it.

[0062] The first spunbond machine 20 deposits a fabric of two-component crimped fibers onto the conveyor belt 10. The two polymer feeds are symbolized at the top of the first spunbond machine 20. The middle spunbond machine 30 deposits a fabric of fibers formed from a thermoplastic elastomer onto the previously formed fabric. The last spunbond machine 40 deposits another fabric of two-component crimped fibers onto the elastic fiber fabric. Each of the spunbond machines 20 and 40 is followed by a pair of pre-compaction rollers 21 and 41, respectively, to pre-compact the respective fabrics.

[0063] The pre-compacted fabric is then calendered in a calendering unit 50 comprising a pair of counter-rotating embossing rollers 51, 52 to form a non-woven sheet. Calendering is followed by an activation stage in the activation unit 60, comprising a pair of counter-rotating activation rollers 61, 62 whose surfaces comprise interlocking structural elements, as described in more detail below. At the end of the overall online process, the product sheet is collected onto the product roll 70.

[0064] Figure 3 shows an embodiment of the drive rollers 61, 62 of a drive unit 60 configured to increase elasticity in the machine direction. Specifically, the image in Figure 3 is a cross-section enlarged along a radial plane perpendicular to the roller axis. Both rollers 61 and 62 comprise a plurality of regularly spaced ribs 63 on their drive surfaces, between which grooves 65 are formed. The ribs 63 are oriented transversely to the machine and extend axially over the surfaces of rollers 61 and 62. The width of the ribs 63 is designated by the letter a, the engagement depth by the letter b, and the distance between adjacent ribs by the letter c.

[0065] Figure 4 shows a unit like the one shown in Figure 3 in operation. From left to right in Figure 4, the unactivated precursor sheet, comprising two facing layers with an interposed elastic layer, enters the activation process. As the sheet enters the contact point of the two rollers 61, 62, the activation process begins, with the sheet being locally stretched between the meshing ribs 63. The elastic layer will elongate during this process due to its elastic properties. The parameters a, b, and c can be varied as needed, depending on the desired elongation property of the nonwoven sheet.

[0066] Even without activation, the use of a combination of a polypropylene homopolymer with a relatively narrow molecular weight distribution and a random ethylene-propylene copolymer with a relatively wider molecular weight distribution in two-component crimped fibers has been shown to produce sheets that can be stretched without breaking in the machine direction to a significant degree, in some embodiments up to 300%. This is sufficient to meet any industry standard and to match the high elongation properties of a nonwoven elastic layer such as that used in the sheets of the invention, which in some embodiments can be elastically stretched from 400 to 500%.

[0067] The beneficial properties of the sheets of the invention are demonstrated in the following examples. bbbC Ln / ZZnZ / E / YIAl

[0068] A series of facing layers joined by spinning were prepared using juxtaposed two-component crimped fibers using the materials specified below. Table 1: Materials used: Type Polymer 1 Polymer 2 Ratio Ex. 1 (comp.) PP / PP 511A 511A (60%) / HP522N (40%) 70 / 30 Ex.2 PP / CoPP 511A RP248R 50 / 50 Ex.3 PP / CoPP 511A QR674K 50 / 50 bblrC Ln / Zznz / E / YIAI

[0069] Polymer 511A is a polypropylene homopolymer from Sabic with a narrow polymer weight distribution (Mw / Mnes of 3.8), an MFR of 25 g / 10min and a Tm of 161°C.

[0070] The HP552N polymer is a polypropylene homopolymer from LyondellBasell with a wide polymer weight distribution (Mw / Mnes of 6.8), an MFR of 13 g / l0min and a Tm of 161°C.

[0071] The RP248R polymer is a random ethylene-propylene copolymer from the company LyondellBasell with an MFR of 30 g / l0min, a medium molecular weight distribution (Mw / Mnes of 5.2) and a Tm of 148°C. It also contains a clarifier and a flake agent.

[0072] The QR674K polymer is a random ethylene-propylene copolymer from Sabic with an MFR of 40 g / 10 min, a wide molecular weight distribution (Mw / Mnes of 8.5) and a Tm of 150°C. It also contains a clarifier and a slip agent.

[0073] Melt flow indices (MFR) as used herein should be understood as determined in accordance with ISO 1133 under conditions of 230°C and 2.16 kg.

[0074] Melting temperatures (Tm) as used herein should be understood as determined by DSC in accordance with ISO 11357-3.

[0075] The values ​​for molecular weight averages (Mwy Mn) and the resulting values ​​for molecular weight distribution (MWD, Mw / Mn) as used herein shall be understood to be determined by GPC in accordance with ISO 16014-1:2003, ISO 16014-2:2003, ISO 16014-4:2003 and ASTM D 6474-12 using the following formulas: M -1 ln Vfi.A; “ Σίϊ / Α, / Λί; ) (1) M ΣΜ.ίΑ.Λ- .Vf.) = M, = Σ:ί,(A. λ λγ i ΣΓί / 4^1 (3)

[0076] For a constant elution volume interval AV¡, wherein A, and M¡ are the chromatographic peak cutoff area and the molecular weight of the polyolefin (MW), associated respectively with the elution volume, V¡, wherein N is equal to the number of data points obtained from the chromatogram between the integration limits.

[0077] A high-temperature GPC instrument, equipped with an infrared (IR) detector (IR4 or The chromatographic system was operated using a PolymerChar 1R5 (Valencia, Spain) or an Agilent Technologies differential refractometer (RI) equipped with three Agilent-PLgel Olexis and one Agilent-PLgel Olexis Guard. 1,2,4-Trichlorobenzene (TCB) stabilized with 250 mg / L of 2,6-Di-tert-butyl-4-methylphenol was used as the solvent and mobile phase. The chromatographic system was operated at 160 °C and a constant flow rate of 1 inL / min. 200 pL of sample solution were injected per analysis. Data collection was performed using Agilent Cirrus software version 3.3 or PolymerChar GPC-1R control software.

[0078] The column assembly was calibrated using universal calibration (in accordance with ISO 16014-2:2003) with 19 narrow MWD polystyrene (PS) standards in the range of 0.5 kg / mol to 11,500 kg / mol. The PS standards were dissolved at room temperature for several hours. The conversion of the maximum molecular weight of polystyrene to polyolefin molecular weights is achieved using the Mark Houwink equation and the following Mark Houwink constants: KPS = 19 x 10.3mL / g, aPS = 0.655 KPE = 39 x 103mL / g, aPE = 0.725 KPP = 19 x 103mL / g, aPP = 0.725

[0079] A third-order polynomial fit was used to fit the calibration data.

[0080] All samples were prepared in the concentration range of 0.5-1 mg / ml and dissolved at 160 °C for 2.5 hours.

[0081] Table 2 below shows the properties obtained for spun-jointed facing sheets of 20 gsm insulated from these materials. bblrC Ln / Zznz / E / YIAI Table 2: Properties obtained: Basis weight (gsm) Thickness* (mm) Tensile strength at break in MD** (N / 50mm) Ex. 1 19.0 0.78 9.9 Ex. 2 18.6 0.61 14.3 Ex. 3 19.9 0.46 12.5 Table 2 (cont.): Properties obtained: Elongation at break in MD** (%) Tensile strength at break in CD** (N / 50mm) Elongation at break in CD** (%) Ex. 1 167 6.3 199 Ex. 2 188 9.7 210 Ex.3 270 8.2 278 *Determined in accordance with WSP 120.6 **Determined in accordance with WSP 100.4 bblrC Ln / Zznz / E / YIAI

[0082] In particular, none of the samples have been activated in a mill as shown in Figures 3 to 4, which had an open spot bonding pattern of 12% of the bonding area with 24 bonding sites per cm2.

[0083] Example 1 is a comparative example. Examples 2-3 are inventive examples. The MD (stress-strain) tensile curves of the samples in Comparative Examples 1-3 are shown in Figures 5 to 7, respectively, where Figures 5 and 6 show curves from several measurements that are then averaged, and Figure 7 shows only one already averaged curve.

[0084] As is evident from the values ​​in Table 2 and the curves in Figures 5-7, the MD elongation of the facing layer in Example 2 is already noticeably greater (around 20%) than the elongation of the facing layer in Comparative Example 1. For the facing layer according to the specifically preferred configuration of Example 3, where the molecular weight distribution of the Co-PP is broader and the MWD difference between the PP and Co-PP is greater than in Example 2, the effect becomes very significant (another 80% improvement). MD elongation at break values ​​of nearly 200% (Example 2), not to mention well over 250% (Example 3), even without activation / pre-stretching, are unique for spunbond materials where the fiber orientation is typically primarily machine-directed.It is also worth noting that the thickness of the facing plies often correlates to some extent with the level of crimp, but the thicknesses of the facing plies in Examples 2 and 3, despite having the same basis weight, are lower than the thickness of the facing ply in Comparative Example 1, so that apparently there are other effects beyond the simple level of crimp that govern the ability of the facing plies spun according to the invention to elongate in the machine direction.

[0085] Hereafter, as Example 4, three sheets of the invention (Samples 4-1, 4-2, and 4-3), comprising an elastic yarn-bonded layer sandwiched between two facing layers configured according to the invention, are manufactured on a line as shown in Figure 2, except for the mill for activating the material (the sheet remained unactivated). The layers were prepared and configured as specified below. Samples 4-1, 4-2, and 4-3 differ only in the basis weights of their layers. Table 3: Materials used / configuration in Example 4: Type Polymer 1 Polymer 2 Ratio Basis Weight (gsm) 4-1 | 4-2 | 4-3 Facing layer 1 PP / CoPP 511A QR674K 50 / 50 20|15 | 10 Th-El elastic cape. Vistamax 7050BF 40|30|20 Facing layer 2 PP / CoPP 511A QR674K 50 / 50 20 | 15 | 10 bblrC Lnzzznz / E / YIAI

[0086] Both facing layers of the sheet in Sample 4-1 correspond to the facing layers investigated in isolation in Example 3. The bonding pattern was as described above for isolated facing layers.

[0087] The elastic layer was manufactured from a single commercially available TPE material Vistamaxx™ 7050FL from ExxonMobil, which is a propylene-based thermoplastic elastomer copolymer with an ethylene content of 13% by weight and a melt flow index of 45 g / 10 min. The bonding pattern, again, was as described above.

[0088] Table 4 below shows the properties that have been obtained for the three samples from Example 4. Table 4: Properties obtained: Basis weight (gsm) Thickness* (mm) Tensile strength at break in MD** (N / 50mm) Sample 4-1 77.8 0.78 30.5 Sample 4-2 63.2 0.68 24.1 Sample 4-3 44.8 0.56 18.7 Table 4 (cont.): Properties obtained: Elongation at break in MD** (%) Tensile strength at break in CD** (N / 50mm) Elongation at break in CD** (%) Sample 4-1 249 20.8 321 Sample 4-2 203 16.6 270 Sample 4-3 192 7.5 274 *Determined in accordance with WSP120.6 **Determined in accordance with WSP 100.4

[0089] As a variation to Example 4, in another Example 5, the same materials as in Example 4 were produced, with the difference that they were pre-stretched in the machine direction and activated in an activation unit 60 as shown in Figures 3 and 4. Specifically, upon entering the space between the rollers of the activation unit 60, the materials were pre-stretched in the machine direction by 100% (to 200% of their original length) by varying the translation speed on the line. In the activation unit, the coupling depth “b” was 2 mm (at a total rib height of 5 mm).

[0090] Table 5 below shows the properties that have been obtained for the three samples from Example 5. bblrC Ln / Zznz / E / YIAI Table 5: Properties obtained: Basis weight (gsm) Thickness (mm) Tensile strength at break in MD* (N / 50mm) Sample 5-1 76.8 0.88 28.3 Sample 5-2 61.2 0.75 26.3 Sample 5-3 42.3 0.60 17.2 Table 5 (cont.): Properties obtained: Elongation at break in MD** (%) Tensile strength at break in CD** (N / 50mm) Elongation at break in CD** (%) Sample 5-1 209 12.7 295 Sample 5-2 202 11.2 346 Sample 5-3 188 6.0 325 'Determined in accordance with WSP120.6 ''Determined in accordance with WSP 100.4

[0091] In addition to inventive examples 4 and 5, such as Example 6, the isolated elastic layer of Example 4, Sample 4-1 was also centrifuged and investigated.

[0092] Figure 8 shows a tensile curve in MD (stress-strain) of this 40 g / m2 elastic spunbond nonwoven isolated layer from Example 6. The material can elongate significantly in MD before breaking, specifically more than 500%, when a tension of 20-25N / 50mm is applied.

[0093] Figure 9 shows superimposed MD (stress-strain) tensile curves of the sheet of the invention of Example 4, Sample 4-1, the facing layer of Example 3, and the elastic layer of Example 6. As is evident from the superimposed curves, the facing layers do not impose a limitation on the elastic profile of the elastic layer before reaching a stretch greater than 300%. The sheet has high elongation and is elastic, meaning that it will retract to its original state once relaxed.

[0094] The curves shown in Figures 8 and 9, such as the curve in Figure 7, are already an averaged curve over several measurements.

[0095] Another important parameter for the elastic materials described herein is their permanent deformation, determined according to ASTM D5459. Permanent deformation is the increase in length, expressed as a percentage of the original length, by which an elastic material fails to return to its original length after being subjected to the extensions prescribed in the ASTM D5459 test procedure. The lower the percentage of permanent deformation, the better the elastic property of the material.

[0096] Figure 10 shows a schematic illustration of a tensile (stress-strain) diagram and increasing and decreasing curves of subsequent stress-strain cycles, representing the ASTM D5459 test. Permanent strain is the value of (AD / AE)xl00.

[0097] Another important parameter is the area between the increasing and decreasing stress-strain curves of a hysteresis plot in a second cycle of an ASTM D5459 test, as expressed as the relative size of the area between the curves (A) relative to the total area under the initial increasing curve (A+B), expressed as a percentage [A / (A+B) x 100 J]. This is used to calculate the percentage of energy dissipated due to internal friction. When the graphs during loading and unloading do not coincide, as is often observed in real-world materials, this means that a certain amount of energy is lost. The lower the percentage, the better the elastic property of the material.

[0098] Figure 11 shows a machine-direction stress-strain diagram for Sample 5-1 of Example 5 obtained from an ASTM D5459 test, first and second cycles. The hysteresis curve shows highly desirable elastic properties for this material in the machine direction. Specifically, the permanent strain after the first cycle is only 1.28%, and the area between the rising and falling curves in the second cycle is only 24.8%.

Claims

1. An elastically stretchable nonwoven sheet comprising at least two layers of nonwoven materials, wherein one layer is an elastically stretchable nonwoven fabric comprising spun elastic fibers formed from a thermoplastic elastomer polymer material, wherein one layer is a stretchable facing layer comprising spun multicomponent crimp fibers, and wherein the adjacent layers are bonded together by raised bonding points, characterized in that at least one of the components of the multicomponent crimp fibers is a propylene-α-olefin copolymer material.

2. The sheet according to claim 1, characterized in that the elongation at break of the sheet in the machine direction is greater than 150% and preferably greater than 200% when measured according to WSP 100.

4.

3. The sheet in conformity with any of the preceding claims, characterized in that the permanent deformation in the machine direction, measured in accordance with ASTM D5459, after the first cycle is less than 15%, preferably less than 10%.

4. The sheet in accordance with any of the preceding claims, characterized in that the area between the increasing and decreasing directional stress-strain curves of a hysteresis chart in a second cycle of an ASTM D5459 test, as expressed in the relative size of the area between the curves (A) in relation to the total area under the initial increasing curve (A+B), expressed in % |A / (A+B)xl00| is less than 40%, preferably less than 30%.

5. The sheet according to any of the preceding claims, characterized in that an additional component of the curled multicomponent fibers is a polypropylene homopolymer material.

6. The sheet according to claim 5, characterized in that the propylene-a-olefin copolymer is a random copolymer of poly(propylene-ethylene).

7. The sheet according to any of the preceding claims, characterized in that the molecular weight distribution of the propylene-α-olefin copolymer is broader than the molecular weight distribution of the other components of the crimped multicomponent fibers. bblrC Ln / Zznz / E / YIAI 8. The sheet according to any of the preceding claims, characterized in that the curled multicomponent fibers are two-component fibers, preferably two-component fibers side by side.

9. The sheet according to any of the preceding claims, characterized in that the thermoplastic elastomer polymer material formed for the elastic fibers is a thermoplastic polyolefin elastomer, preferably comprising propylene-to-olefin copolymers.

10. The sheet according to any of the preceding claims, characterized in that the sheet comprises a sandwich structure of elastically stretchable nonwoven material between at least one facing layer on each side thereof, wherein the sheet preferably consists of these elastic and facing layers.

11. The sheet in accordance with any of the preceding claims, characterized in that the basis weight of each facing layer is between 5 and 40 g / m2 and / or wherein the basis weight of the elastic layer is between 10 and 140 g / m2.

12. A method for manufacturing the elastically stretchable nonwoven sheet according to any of the preceding claims, the method being characterized in that it comprises the following in-line steps: (a1) spinning crimped multicomponent fibers, wherein at least one of the components of the crimped multicomponent fibers is a propylene-α-olefin copolymer, and laying them on a rotating, moving belt to form a fabric; (a2) spinning elastic fibers formed from a thermoplastic elastomer polymer material and laying them on the surface of the fabric formed in step (a1) to form another fabric; (a3) ​​optionally, spinning crimped multicomponent fibers, wherein at least one of the components of the crimped multicomponent fibers is a propylene-α-olefin copolymer, and laying them on the surface of the fabric formed in step (a2) to form another fabric; (b) joining the adjacent fabrics together to form the elastically stretchable spunbond nonwoven sheet.

13. The method according to claim 12, characterized in that it further comprises an online or offline step (c) of pre-stretching the sheet in the machine direction.

14. The method according to claim 13, characterized in that, during step (c), the sheet is pre-stretched in the machine direction by 40-160%, preferably 60-140%, more preferably 80-120% of its original dimension.

15. Use of the elastically stretchable nonwoven sheet according to any of claims 1-11 in the manufacture of hygiene articles, preferably in the manufacture of a diaper comprising the sheet as an elastic waistband material.