Patent Application
20240368813
The present disclosure is related to nonwoven webs, and in particular to nonwoven webs made of crimpable multi-component fibers that are subjected to bonding and hydroentanglement during the nonwoven web manufacturing process.
Spunbonded nonwovens comprising crimped multicomponent fibers are known in the art and early technologies have been described in, e.g., U.S. Pat. No. 6,454,989 B1, EP 2 343 406 B1 and EP 1 369 518 B1. The crimped fibers make these materials high loft with improved softness and flexibility. Generally, the fibers used in these materials are comprised of side-by-side, eccentric sheath-core or similar distribution of two polymers with different characteristics that cause the fibers to helically crimp during the quenching and stretching process.
For example, EP 3 246 444 A1 discloses spunbonded high loft materials made based on a polypropylene homopolymer and a random polypropylene-ethylene copolymer, that achieve high crimp and thereby softness. Other new generation high loft spunbond materials made from crimped fibers are disclosed in, for example, EP 3 246 443, EP 3 121 314, EP 3 165 656 or EP3521495.
The hydroentanglement process is also known in the art and widely used in many various applications—from full consolidation of fabric to 3D shaping, aperturing, and softening.
The combination of crimped fibers and hydroentangling is in general also known. For example, U.S. Patent Application Publication No. 2022/0168157 describes a hydroentangled patterned apertured web with suggested use of crimped filaments to achieve softness, highlighting formation of openings and “cups” that has benefits in softness perception and fluid operation. For example, PCT Publication No. WO2010073149 describes splitting and/or partial splitting of multicomponent self-crimped filaments by water jet energy and advantages of their use. The structures described above deliver desired properties, but in terms of production they represent more demanding processes and, in particular, relatively narrow production windows.
Another combination of crimped filaments and hydroentangle process is described in PCT Publication No. WO2021046088, wherein the described process leads to a soft material by forming a specific structure comprising parts of helically configured crimped portions. The demand of keeping parts of filaments with helical crimp inside of the fabric requires a careful set of production conditions. Also, a proper hydroentangling process requires rather long elements of movable filaments, which are generally prevented in fully bonded fabric with standard bonding area of 10-15%.
A nonwoven fabric according to an exemplary embodiment of the present invention comprises: a plurality of endless crimpable multicomponent filaments; a plurality of loops that extend only in a direction out of a base plane of the nonwoven fabric, the base plane being an imaginary plane through the nonwoven fabric that extends in a machine direction and a cross direction of the nonwoven fabric, each of the plurality of loops made up of at least three of the plurality of filaments, the nonwoven fabric being devoid of loops that extend within the base plane; a plurality of bows that extend in directions within and out of the base plane of the nonwoven fabric, each of the plurality of bows made up of no more than one of the plurality of filaments; and a plurality of fused inter-filamentary conjunctions between at least some of the plurality of filaments.
A nonwoven fabric according to an exemplary embodiment of the present invention comprises: a plurality of endless multicomponent filaments each having a crimp supporting cross-section; a plurality of loops that extend only in a direction out of a base plane of the nonwoven fabric, the base plane being an imaginary plane through the nonwoven fabric that extends in a machine direction and a cross direction of the nonwoven fabric, each of the plurality of loops made up of at least three of the plurality of filaments, the nonwoven fabric being devoid of loops that extend within the base plane; a plurality of bows that extend in directions within and out of the base plane of the nonwoven fabric, each of the plurality of bows made up of no more than one of the plurality of filaments; and a plurality of fused inter-filamentary conjunctions between at least some of the plurality of filaments.
In an exemplary embodiment, the fused inter-filamentary conjunctions are bonding impressions.
In an exemplary embodiment, the bonding impressions are on a surface of the fabric.
In an exemplary embodiment, the fused inter-filamentary conjunctions are bonding points.
In an exemplary embodiment, the nonwoven fabric has a bulkiness of 70 kg/m3 or less.
In an exemplary embodiment, the nonwoven fabric has a thickness to basis weight ratio of at least 10 liter to 1 kg, preferably of at least 12 liter to 1 kg, more preferably of at least 14 liter to 1 kg.
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the machine direction of 2 g to 15 g.
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the machine direction from 2 g to 12 g.
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the machine direction from 2 g to 10 g
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the machine direction from 2 g to 8 g.
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the machine direction from 2 g to 6 g.
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the cross direction from 1 g to 10 g.
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the cross direction from 1 g to 8 g.
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the cross direction from 1 g to 6 g.
In an exemplary embodiment, the nonwoven fabric has a Handle-O-Meter value in the cross direction from 1 g to 5 g.
In an exemplary embodiment, the nonwoven fabric has an Average Handle-O-Meter value of 1 g to 10 g.
In an exemplary embodiment, the nonwoven fabric has an Average Handle-O-Meter value of 1 g to 8 g.
In an exemplary embodiment, the nonwoven fabric has an Average Handle-O-Meter value of 1 g to 6 g.
In an exemplary embodiment, the nonwoven fabric has an Average Handle-O-Meter value of 1 g to 5 g.
In an exemplary embodiment, the nonwoven fabric has a resilience of at least 10%.
In an exemplary embodiment, the nonwoven fabric has a resilience of at least 15%.
In an exemplary embodiment, the nonwoven fabric has a resilience of at least 20%.
In an exemplary embodiment, the nonwoven fabric has a resilience of at least at least 25%.
In an exemplary embodiment, the nonwoven fabric has a resilience of at least 30%.
In an exemplary embodiment, the nonwoven fabric has a recovery of at least 50%.
In an exemplary embodiment, the nonwoven fabric has a recovery of at least 60%.
In an exemplary embodiment, the nonwoven fabric has a recovery of at least 70%.
In an exemplary embodiment, the nonwoven fabric has a recovery of at least 80%.
In an exemplary embodiment, the nonwoven fabric has a recovery of at least 90%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force of at least 15%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force of at least 20%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force of not more than 100%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force of not more than 80%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force of not more than 65%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force in a range of 15% to 50%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force in a range of 15% to 40%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force in a range of 15% to 35%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force in a range of 30% to 100%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force in a range of 30% to 80%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force in a range of 40% to 80%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force in a range of 40% to 70%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation at 5 N force in a range of 50% to 65%.
In an exemplary embodiment, the nonwoven fabric has a cross direction elongation at 5 N force in a range of 25% to 60%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation of at least 60%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation of at least 70%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation of at least 80%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation of at least 90%.
In an exemplary embodiment, the nonwoven fabric has a machine direction elongation of at least 100%.
In an exemplary embodiment, the nonwoven fabric has a cross direction elongation of at least 50%.
In an exemplary embodiment, the nonwoven fabric has a cross direction elongation of at least 60%.
In an exemplary embodiment, the nonwoven fabric has a cross direction elongation of at least 70%.
In an exemplary embodiment, the nonwoven fabric has a cross direction elongation of at least 80%.
In an exemplary embodiment, the nonwoven fabric has a cross direction elongation of at least 90%.
In an exemplary embodiment, the nonwoven fabric has a basis weight of at least 15 gsm.
In an exemplary embodiment, the nonwoven fabric has a basis weight of at least 20 gsm.
In an exemplary embodiment, the nonwoven fabric has a basis weight of at least 25 gsm.
In an exemplary embodiment, the nonwoven fabric has a basis weight of 200 gsm or less.
In an exemplary embodiment, the nonwoven fabric has a basis weight of 100 gsm or less.
In an exemplary embodiment, the nonwoven fabric has a basis weight of 75 gsm or less.
In an exemplary embodiment, the nonwoven fabric has a basis weight of 50 gsm or less.
In an exemplary embodiment, the nonwoven fabric has a basis weight in a range of 200 gsm to 15 gsm.
In an exemplary embodiment, the nonwoven fabric has a basis weight in a range of 100 gsm to 15 gsm.
In an exemplary embodiment, the nonwoven fabric has a basis weight in a range of 85 to 15 gsm.
In an exemplary embodiment, the nonwoven fabric has a basis weight in a range of 50 gsm to 15 gsm,
In an exemplary embodiment, the nonwoven fabric has a basis weight in a range of 50 gsm to 20 gsm.
In an exemplary embodiment, the nonwoven fabric has a basis weight in a range of 50 gsm to 25 gsm.
In an exemplary embodiment, the nonwoven fabric has a normalized machine direction tensile strength of at least 0.26 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a normalized machine direction tensile strength of at least 0.28 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a normalized machine direction tensile strength of at least 0.30 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a normalized machine direction tensile strength of at least 0.30 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a normalized machine direction tensile strength of at least 0.32 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a cross direction tensile strength of at least 2 N/cm.
In an exemplary embodiment, the nonwoven fabric has a normalized cross direction tensile strength of at least 0.13 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a normalized cross direction tensile strength of at least 0.15 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a normalized cross direction tensile strength of at least 0.17 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a normalized cross direction tensile strength of at least 0.19 N·m2/g·cm.
In an exemplary embodiment, the nonwoven fabric has a normalized cross direction tensile strength of at least 0.20 N·m2/g·cm.
In an exemplary embodiment, the plurality of filaments in a natural state have a crimp frequency lower or equal to 25 crimps per inch.
In an exemplary embodiment, the plurality of filaments in a natural state have a crimp frequency lower or equal to 20 crimps per inch.
In an exemplary embodiment, the plurality of filaments in a natural state have a crimp frequency lower or equal to 15 crimps per inch.
In an exemplary embodiment, the plurality of filaments in a natural state have a crimp frequency lower or equal to 10 crimps per inch.
In an exemplary embodiment, plurality of filaments in a natural state have a crimp frequency of at least 2 crimps per inch.
In an exemplary embodiment, the plurality of filaments in a natural state have a crimp frequency of at least 3 crimps per inch.
In an exemplary embodiment, the plurality of filaments in a natural state have a crimp frequency of at least 4 crimps per inch.
In an exemplary embodiment, the plurality of filaments in a natural state have a crimp frequency of at least 5 crimps per inch.
In an exemplary embodiment, the plurality of filaments have an eccentric core-sheath or side by side cross-section.
In an exemplary embodiment, each of the plurality of filaments comprise a first polymer and a second polymer that is a bonding polymer.
In an exemplary embodiment, the first polymer has a melt temperature that is higher than that of the second polymer.
In an exemplary embodiment, a difference between the melt temperature of the first polymer and the melt temperature of the second polymer is at least 5° C.
In an exemplary embodiment, the bonding polymer is present at least on part of each filament surface.
In an exemplary embodiment, the bonding polymer comprises a polymer selected from the group consisting of: polyolefins, low-melting polymers including low-melting polyester grades, copolymers thereof and blends thereof.
In an exemplary embodiment, the first polymer comprises a polymer selected from the group consisting of: polyolefins, polyesters, copolymers thereof, and blends thereof.
In an exemplary embodiment, the first and second polymers form bicomponent polymer pairs selected from the group consisting of: PP1/PP2, PP/PE, PET/PE, PET/PP, PET/PET, PLA/PLA, PLA/PE and PLA/PP, wherein PP, PE, PET and PLA are virgin polymer, copolymer or blends of thereof, and where PP1 is a first type of polypropylene, PP2 is a second type of polypropylene, PE is polyethylene, PET is polyethylene terephthalate and PLA is polylactic acid.
In an exemplary embodiment, the plurality of endless multicomponent filaments form at least one layer, and the nonwoven fabric comprises at least one second layer.
A nonwoven web according to an exemplary embodiment of the resent invention has a Handle-O-Meter value in the machine direction from 2 g to 6 g, a Handle-O-Meter value in the cross direction from 1 g to 5 g, a bulkiness of 70 kg/m3 or less, a machine direction elongation at 5 N force in a range of 30% to 100%, and a cross direction elongation at 5 N force in a range of 25% to 60%.
A method of forming a nonwoven fabric according to an exemplary embodiment of the present invention comprises: forming a nonwoven batt formed of endless partially irregularly crimped multicomponent filaments; subjecting the nonwoven batt to thermal pre-consolidation to form fused inter-filamentary conjunctions, wherein at least some of the filaments become more irregularly crimped during the step of forming the batt and/or the step of thermal pre-consolidation; and hydroentangling the pre-consolidated batt to form a nonwoven fabric having a plurality of loops that extend only in a direction out of a base plane of the nonwoven fabric, the base plane being an imaginary plane through the nonwoven fabric that extends in a machine direction and a cross direction of the nonwoven fabric, each of the plurality of loops made up of at least three of the plurality of filaments, the nonwoven fabric being devoid of loops that extend within the base plane, and a plurality of bows that extend in directions within and out of the base plane of the nonwoven fabric, each of the plurality of bows made up of no more than one of the plurality of filaments.
In an exemplary embodiment, the thermal pre-consolidation comprises a first pre-consolidation step and a second pre-consolidation step.
In an exemplary embodiment, the first and second pre-consolidation steps are performed using one or more of the following: compact rollers, calender rolls, hot air knife, and hot air oven.
The term “filament” is here defined as an endless filament, whilst the term “staple fiber” describes a fiber that is cut to a defined length. The terms “fiber” and “filament” are herein used to confer the same meaning. For a short and cut fiber, the term “staple fiber” is used exclusively.
The term “inter-filamentary conjunction” refers to all the possible mutual interactions between individual filaments or individual parts of the filaments, i.e. bonded, partially bonded or non-bonded contact, intersection, interconnection, parallel contact, etc. inter-filamentary conjunction may form a filament-to-filament bond, but also can present two independent filaments touching each other without any limitation to their mutual movement.
The term “mono-component filament” or “mono-component fiber” relates to a filament formed from a single polymer or from a single polymer blend, whereby it is differentiated from a bi-component filament or multi-component filament.
The term “multi-component fiber” or “multi-component filament” designates a fiber or filament the cross-section of which incorporates more than one individual partial component, whilst each of these independent components in the cross-section consists of a different polymeric compound or a different blend of polymeric compounds. The term “multi-component fiber/multi-component filament” is thus a superior term, that includes, but is not limited to “bi-component fiber/bi-component filament”. The different components of multi-component filaments are arranged in clearly defined areas arranged along the cross-section of the filament and extend out continuously along the length of the filament. A multi-component filament may have a cross-section divided into several partial cross-sections consisting of various components of arbitrary shapes or arrangements, including, for example, in a coaxial arrangement of the partial components of the cross-section in an arbitrary mutual arrangement of partial components of the cross-section in the form of core and sheath, radial or so-called islands-in-the-sea, etc.
The design of multi-component filaments has a determining impact on the crimp-ability of these filaments. An effective method to recognize the design of a multi-component filament is to see and evaluate its cross-section which makes visible the position of different components of a filament. Typically, the different components are comprised of different polymer formulations which are selected and characterized by e.g. different melting temperatures and/or different shrinkage properties after spinning, quenching, drawing and final fiber solidification. Typically, rotational symmetric position of filament components in its cross section (e.g. concentric core/sheath) will result in non-crimped filaments, while asymmetric position of filament components (e.g. side by side, or eccentric Core/Sheath) will become the differential, potential crimp force to achieve either self-crimping and/or heat activated crimped filaments. To simplify the language in this application, the terms “crimpable cross-section” and “non-crimpable cross-section” will be used in place of “filaments showing a cross-section which is supporting the crimp” and “filaments showing a cross-section which does not support a crimp”. The term “crimpable cross-section” herein refers to multicomponent fibers, where components with different shrinkage properties are arranged across the cross-section, so that either these filaments will self-crimp during the filament drawing and solidification or, when heated to or above an activation temperature and then slowly cooled down, the fibers crimp, which causes these fibers to follow the vectors of the shrink forces. Thereby, when the fiber is released, it creates a so-called helical crimp, although when contained within a fiber layer the mutual adhesion of the fibers does not permit the creation of ideal helixes. For a multicomponent fiber, the center of mass can be determined for each individual component in the fiber cross-section (considering their areas/positions in the cross-section). Not to be bound by a theory, it is believed that when the centers of gravity of all areas of each of the components are at the same point as described as rotationally symmetric concentric core/sheath, the fiber is “non-crimpable”.
The measurement “filament diameter” is expressed in units of μm. The terms “number of grams of filament per 9000 m” (also denier or den) or “number of grams of filament per 10000 m” (dTex) are used to express the degree of fineness or coarseness of a filament as they relate to the filament diameter (a circular filament cross-section is assumed) multiplied by the density of the material or materials used.
“Machine direction” (MD)—in relation to the production of nonwoven fibrous material and the actual nonwoven fibrous material itself, the term “machine direction” (MD) represents the direction that corresponds to the forward motion direction of the nonwoven fibrous material on the production line on which this material is produced.
“Cross direction” (CD)—in relation to the production of nonwoven fibrous material and the actual nonwoven fibrous material itself, the term “cross direction” (CD) represents the direction that is transversal to the forward motion direction of the nonwoven fibrous material on the production line on which this material is produced, whilst located on the base plane of the nonwoven fibrous material.
“z-direction”—in relation to the production of nonwoven fibrous material is the vertical direction to the planar MD×CD. The extension in z-direction describes the thickness of the nonwoven material.
“Nonwoven material” or “nonwoven fabric” is a belt or fibrous formation produced from directionally or randomly oriented filaments that are first formed during the creation of a layer of filaments and then consolidated together by means of friction or elicitation of cohesive or adhesive forces and finally consolidated by the creation of mutual bonds, whilst this consolidation is accomplished thermally (e.g. by the effect of flowing air, calendaring, effect of ultrasound, etc.), chemically (e.g. using an adhesive), mechanically (e.g. hydroentanglement, etc.), or alternatively by a combination of these methods. The term does not refer to fabrics formed by weaving or knitting or fabrics using yarns or fibers to form bonding stitches. The fibers may be of natural or synthetic origin and may be staple yarns, continuous fibers or fibers produced directly at the processing location. Commercially available fibers have a diameter ranging from less than approximately 0.001 mm to more than approximately 0.2 mm and are supplied in various forms: short fibers (known as staple or cut fibers), continuous individual fibers (filaments or mono-filament fibers), non-twisted bundles of filaments (combed fibers) and twisted bundles of filaments (yarns). A nonwoven fabric can be produced using many methods, including technologies such as meltblown, spunbond, spunmelt, spinning using solvents, electrostatic spinning, carding, film fibrillation, fibrillation, air-laying, dry-laying, wet-laying with staple fibers and various combinations of these processes as known in the art. The basis weight of nonwoven fabrics is usually expressed in grams per square meter (g/m2 or gsm).
The “spunbond”, “spunmelt” or “spunlaid” process is a nonwoven fabric production process, which includes a direct conversion of polymers to filaments, which is directly followed by the deposition of such created filaments, thereby creating a layer of nonwoven filaments containing randomly arranged filaments. This nonwoven layer of filaments is then consolidated to enclose the nonwoven fabric by creating bonds between the filaments. The consolidation process can be performed using various methods, for example by the effect of passing air, calendaring, etc.
The term “batt” refers to materials in the form of filaments that are found in the state prior to bonding, a process that can be performed in several ways, for example, air-through-bonding, calendaring etc. The “batt” consists of individual filaments between which a fixed mutual bond is usually not yet formed even though the filaments may be pre-bonded/pre-consolidated in certain ways, where this pre-consolidation is done in one or more steps. The first of them may occur during or shortly after the laying of the filaments in the spunlaying process. This pre-consolidation, however, still permits many of the filaments to be freely moveable so they can be repositioned. The above mentioned “batt” may consist of several layers created by the deposition of filaments from several spinning beams in the spunlaying process.
The terms “bonds between filaments” or “bonding points” relate to the bonds that usually connect two filaments in a location where these filaments intersect each other or in a location where they come into contact or alternatively where they adjoin each other. By means of bonding points/consolidating bonds it is possible to connect more than two filaments or to connect two parts of the same filament. Thus, the term “bonding point” here represents the connection of two or more fibers/filaments at the point of contact by the interconnection of their components exhibiting lower melting points. In the bonding point, the formed component of the filament with the higher melting point is in general less impacted than the formed component of the filament with the lower melting point. i.e. the sheath melts slightly while the core remains essentially unchanged. Conversely, the term “bonding impression” represents a surface upon which the boss of a calendar roller has acted. A bonding impression has a defined area given by the size of the boss on the bonding roller and compared to the adjacent area typically has a smaller thickness. During the bonding process, the bonding impression's area is typically subjected to significant mechanical pressure, which, along with temperature, may affect the shape of all filament components within the bonding impression's area.
“Fused inter-filamentary conjunctions” as used herein describes both “bonds between filaments” and “bonding impressions”.
The term “fully bonded nonwoven” as used herein is a simplified expression for “fully thermally bonded nonwoven” and refers to a nonwoven that has fibers that are fused to one another. For example, a fully calendar bonded nonwoven has fibers that are fused to one another at bonding impressions via melting and solidification and a fully hot-air bonded nonwoven has fibers fused at bonding points with sufficient density. Such a fabric might be used for various applications, e.g., converted into a diaper, etc., or used as a precursor for further treatment (e.g., hydrophilic spin finish application or hydraulic softening treatment). For example, a fully calendar-bonded nonwoven may be produced by passing a batt through a nip point between two heated rolls under pressure, thereby providing a pattern of fused embossed impressions in the fabric. The pressure and temperature within the nip are sufficient to soften and melt the individual fibers and to then weld them together using a pattern of protrusions on at least one of the heated rolls to create a series of fused bonding impressions where most fibers within the fused bonding impression can no longer be distinguished as individual fibers. The roll temperature and pressure are adjusted dependent upon fabric formulation and basis weight. For example, a 20-25 gsm 100% polypropylene homopolymer spunbond is typically bonded at roll temperatures of >150 deg C. and with a nip pressure greater than 90 N/mm. Temperature/pressure settings are adjusted to handle different basis weights and or line speeds. Higher basis weights and/or line speeds may require increased nip pressures and/or temperatures to achieve a “fully” bonded fabric with fused bond points. It should be appreciated that tack bonding is not within the scope of the definition of “fully bonded” for the purposes of this disclosure.
The term “bond area percentage” as used herein represents a ratio of an area occupied by bonding impressions to a total surface of a nonwoven fabric expressed as a percentage and measured according to the Bond Area Percentage Method set forth herein.
In the sense used herein, the term “layer” relates to the partial component or element of a fabric. A “layer” may be in the form of multiple filaments produced on a single spinning beam or on two or more consecutively arranged spinning beams, which create alike filaments. For example, two consecutively arranged spinning beams intended for performing the spunbond procedure, have comparable settings and process polymers of the same composition, can combine to produce a single layer. Conversely, two spunbond-type spinning beams of which one produces, for example, single-component filaments and the other produces, for example, bi-component filaments, will form two different layers. The composition of a layer can be ascertained based on knowledge of the individual settings and components determining the resin (polymer) composition used for the creation of the layer or by means of analysis of the nonwoven fabric itself, for example, by using electron microscopy, or alternatively by analysis of the composition used in the production of the filaments contained in the layer using the DSC or NMR methods. Adjacent layers of filaments do not necessarily have to be strictly separated, the layers in the border region may blend in together because of the filaments of a later deposited layer falling into the gaps between the filaments of an earlier deposited layer. Layers may in nonwoven fabric form typical structure (e.g. SMS) or other forms (e.g., combination layers with different crimp frequency, combination of layers with different material composition, etc.)
“Softness” should be understood as a general description of pleasant human feeling induced by both haptic and visual perception of textile. Such softness cannot be expressed by a single measurement. To show softness improvement in values, different methods can be used. For example, Handle-O-Meter can express fabric bendability, compressibility and resilience can express so called soft-loft. Fabric thickness, filaments thickness, type of crimp, elongation at low force, etc. are examples of further measurements describing fabric conditions, that also involve human perception and can influence judgement of softness. Contrary to general expectation, visual aspects of fabric are important to human softness perception. When the fabric is perceived as likely pleasant and soft by the human eye, it is more probable that the subjective softness rating would also be higher. Especially fabric uniformity and opacity can be used to express visual aspects of nonwovens.
The term “compressibility” as used herein relates to the distance in millimeters by which a nonwoven fabric is compressed by the effect of a load defined during the measurement of “elasticity”.
The term “recovery” as used herein relates to the ability of the fabric to recover its initial shape after being compressed. This concerns primarily the ability of regeneration (recovery) of bulkiness based on the ratio between the thickness of the fabric after release of the acting load and the initial thickness of the fabric.
The term “base plane” is an imaginary flat mid-plane in the x y direction through the fabric that visually divides the main bulk of the fabric in half. The main bulk of fabric as well as filaments within the fabric undulate relative to the imaginary mid-plane.
For the purposes of this application the term “loops” refers to looping structures formed by three or more fibers, where the loops extend only in the direction out of the base plane of the nonwoven web. In exemplary embodiments, loops extend out of the base plan substantially in the z-direction, and in exemplary embodiment extend out of the base plane (where the base plane extends in the MD and CD directions) at an angle of at least 15°, preferably at least 30°, even more preferably at least 45°, and most preferably at least 60°. The loops are primarily created by the hydroentanglement process, which pushes the filaments out of the base plane of the web. Hydroentangle loops are typically formed by multiple filaments (approximately 3 to 10) forming loops that extend substantially in the z-direction in the form of a filament “bundle”. Hydroentangled loops are typically formed on that side of nonwoven, where hydroentangle process water leaves the fabric. In the case of both side hydroentanglement (e.g., in two steps, where fabric is exposed to water jets from one side and then from the other side), hydroentangle loops are formed on both sides of fabric.
For the purposes of this application the term “bows” refers to arc-like structures each formed by only one fiber, where the bows may extend in all directions relative to the base plane of the nonwoven web (i.e., in the x, y and z directions, including in the MD and CD directions). The bows are primarily created by the natural tendency of the filaments to crimp, but due to the internal forces within the web, are prevented or partially prevented from crimping, leading to the bows extending in all directions relative to the base plane of the web.
In accordance with exemplary embodiments of the present invention, a bulky and soft nonwoven fabric is achieved by a unique combination of self-crimped, endless filaments, thermal and/or mechanical prebonding and hydroentanglement.
Endless filaments produced by spunmelt process can be winding or can be crimped. For the purposes of this disclosure, filament crimp should be understood as relating to the tendency of free filament to form a regular alpha-helix structure, an example of which is shown in
Endless filaments suitable to form the layer of fabric according to exemplary embodiments of the invention in free form or in their natural state (for example taken from batt before consolidation or bonding steps are applied or for example extracted from disintegrated nonwoven) have a crimp frequency lower or equal to 25 crimps per inch, preferably lower or equal to 20 crimps per inch, more preferably lower or equal to 15 crimps per inch, and even more preferably lower or equal to 10 crimps per inch.
Endless filaments suitable to form the layer of fabric according to exemplary embodiments of the invention in free form or in their natural state (for example taken from batt before bonding steps are applied or for example extracted from disintegrated nonwoven) have a crimp frequency at least 2 crimps per inch, preferably at least 3 crimps per inch, even more preferably at least 4 crimps per inch, and even more preferably at least 5 crimps per inch.
It is well known in the industry that certain combinations of polymers arranged in a so-called crimpable cross-section provide crimping. This can be either immediate self-crimping or latent crimping, where the fibers require activation to exhibit crimps (typically by adding energy to the system—for example by heating the material using hot fluid media, contact rollers, radiant heat, etc). Fibers with a crimpable cross-section and suitable polymer composition provide regular crimps forming a so-called helical crimp (
Fibers with a crimpable cross-section tend to form regular shapes-helical crimps, wherein the fibers tend to regularly bend towards that side of the fiber comprised of the more shrinkable material. Although, they are also limited by their neighboring fibers; the regular force leads them to create well-defined helixes. Not to be bound by theory, it is believed that the greater the inner shrinkage force, the higher will be the ‘crimps per length’ unit on single fibers, and, therefore, there will be more helix parts found on the fabric structure. In contrast, when the crimping level is lower, for example, less than 25 crimps per inch (each single “round” on more than 1 mm of formed helix length), the free space between fiber contact points starts to be insufficient for the formation of a proper part of a helix, whilst the opposing forces caused by fiber contacts also become relatively stronger. It should be appreciated that set crimping numbers are just examples and can differ with various fiber compositions and/or process conditions. Below approximately 15 crimps per inch (each single “round” on more than 2 mm of formed helix length), the parts of helixes are hard to identify and below approximately 10 crimps per inch (each single round on more than approx. 2.5 mm helix length) the regular forces in the fiber are fully overcome by the opposing forces and contrary to the inner shrinkage vector shift and tend towards regular crimp formation, thus the structure may appear to be fully irregular. Examples of structure differences based on a crimp of rayon fibers can be seen in
According to an exemplary embodiment of the invention, spunmelt nonwoven may comprise multicomponent filaments with crimpable cross-section, including, for example, in non-coaxial arrangement of the partial components of the cross-section in an arbitrary mutual arrangement of partial components of the cross-section in the form of for example filaments with eccentric core-sheath cross-section or side by side cross-section.
According to an exemplary embodiment of the invention, spunmelt nonwoven may comprise multicomponent filaments having a bonding polymer on at least a part of its surface. The bonding polymer can be chosen from a group of polyolefins (e.g., polypropylene or polyethylene), low-melting polymers including low-melting polyester grades (e.g., aliphatics such as polylactic acid, or aromatics such as polyethylene terephthalate), copolymers or blends of suitable polymers. It is within the scope of the invention that the bonding polymer is selected from the group of polyesters that also includes polyester copolymers (coPET) or polylactide copolymers (COPLA).
According to an exemplary embodiment of the invention, spunmelt nonwoven may comprise multicomponent filaments having a first polymer with a melt temperature higher than the bonding polymer's melt temperature, preferably the melt temperature difference is at least 5° C. The first polymer can be chosen from a group of polyolefins (e.g., polypropylene or polyethylene), polyesters (e.g., aliphatics such as polylactic acid or aromatics such as polyethylene terephthalate), copolymers or blends of suitable polymers. It is within the scope of the invention that the first polymer is selected from the group of polyesters that also includes polyester copolymers (coPET) or polylactide copolymers (COPLA).
The preferred combinations of components for the bi-component filaments according to the invention are PP1/PP2, PP/PE, PET/PE, PET/PP, PET/PET, PLA/PLA, PLA/PE and PLA/PP, wherein PP, PE, PET and PLA may be virgin polymer, copolymer or blends thereof. For example, a combination of PP in one component and a blend of the same PP with another PP with differing melt-flow-index and/or differing melt temperature are known as good crimping compositions (as described, for example, in U.S. Pat. Nos. 11,021,821 and 10,435,829 and U.S. Patent Application Publication 2019/0233994). The polymer composition can also contain a suitable process additive to enhance crimping, such as, for example, crystalizing agents, slip agent, process agents, etc. For the purposes of this disclosure, “PP” refers to polypropylene, “PE” refers to polyethylene, “PET” refers to polyethylene terephthalate, and “PLA” refers to polylactide.
Nonwovens formed of crimped filaments and compacted by means of thermobonding (e.g., calendering, hot-air bonding) are known in the industry. Also, the combination of crimped filaments and hydro-entangling based compaction is known, as well as a combination of calendering (fabric compaction) and hydro-treatment (e.g., softening of the fabric etc.). In contrast to these known process, exemplary embodiments of the present invention involve a unique combination of thermal pre-bonding to a specified level followed by hydroentangling compaction, which leads to a specific structure with high voluminosity and homogencity of nonwoven fabric, and enhanced softness (especially reported by human respondents) in combination with good mechanical properties (e.g., elongation at low force) and a reasonable abrasion rating. The resulting material is breathable, incompressible, and has a high liquid absorption capacity.
Fabric according to exemplary embodiments of the invention is unique by providing a high level of inner filament-to-filament tension. Not to be bound by a theory, it is believed that the final effect is provided by the synergistic effect of three components. The first tension component is provided by an irregular crimp structure formed during filament laydown (and possibly supported by activation of latent crimp in nonwonven batt or fabric). The second tension component is provided by thermobonding fixation, forming inter-filamentary conjunctions and/or fragile not-fully-through-fused embossed impressions. Thermal pre-consolidation fuses some of the fibers, forming fused inter-filamentary conjunctions. The formed batt must be strong enough to prevent filaments or their substantial parts from free movements leading to untangling of the structure, releasing the filament-to-filament tension and losing the filament or its substantial part from the fabric. On the contrary, too much bonding would lead to solid structure and will prevent desired filament movements and entangling during the hydroentangling compaction step. The third tension component is provided by hydroentangling, which needs to be intensive enough to compact the structure, entangle the filaments in the z-direction to form a stable structure, but mild enough to keep the fabric soft and bulky and does not compress it to a thin solid (e.g. carpet like) structure. All three parts of the process lead to a structure full of loops formed by hydroentangling process (see
In contrast to the structure shown in
Hydroentangle loops, fused interfilamentary conjunctions and crimp-driven bows are even better visible on SEM microscopy pictures, as shown in
Not to be bound by theory, fabric according to the invention formed of self-crimped or heat activated self-crimped filaments when carefully disintegrated, for example torn, can release parts of filaments that when freed can create a helical crimp 104 (as shown in
Not to be bound by theory, it is believed that the fabric structure described herein with inner tension formed of crimping and entangling results in enhanced softness. It is thought that the curl in the crimped fibers adds loft and fluff to the web, enhancing visual and tactile softness signals. Not to be bound by theory, it is believed that the formed irregular structure with bows, loops, looped crossing, loose knots, “finely braided” braids or even full knots are, especially by its structure irregularity at a small scale, provides a higher softness rating based on human haptic perception.
Softness should be understood as a general description of pleasant human feeling induced by both haptic and visual perception of textile. Such softness cannot be expressed by a single measurement. To show softness improvement in values, different methods can be used. For example, Handle-O-Meter can express fabric bendability, compressibility and resilience can express so called soft-loft. Fabric thickness, filaments thickness, type of crimp, elongation at low force, etc. are examples of further measurements describing fabric conditions, that also involve human perception and can influence judgement of softness. Contrary to general expectation, visual aspects of fabric are important to human softness perception. When the fabric is perceived as likely pleasant and soft by human eye, it is more probable that also subjective softness rating would be higher. Especially fabric uniformity and opacity can be used to express visual aspects of nonwovens.
In an exemplary embodiment, the nonwoven web has a bulkiness of 70 kg/m3 or less.
In an exemplary embodiment, the nonwoven web has a Thickness to Basis weight ratio of at least 10 liter to 1 kg, preferably of at least 12 liter to 1 kg, more preferably of at least 14 liter to 1 kg.
In an exemplary embodiment, the nonwoven web has a Handle-O-Meter value in MD of 2 to 15 g, preferably in the range of 2 to 12 g, more preferred in the range of 2 to 10 g, even more preferred in the range 2 to 8 g, and most preferably in the range of 2 to 6 g.
In an exemplary embodiment, the nonwoven web has a Handle-O-Meter value in CD of 1 to 10 g, preferably in the range of 1 to 8 g, more preferably in the range of 1 to 6 g, and most preferably in the range of 1 to 5 g.
In an exemplary embodiment, the nonwoven web has an Average Handle-O-Meter value of 1 to 10 g, preferably in the range of 1 to 8 g, more preferably in the range of 1 to 6 g, and most preferably in the range of 1 to 5 g.
In an exemplary embodiment, the nonwoven web has a resilience of at least 10%, preferably of at least 15%, more preferably of at least 20%, more preferably of at least 25%, and most preferably of at least 30%.
In an exemplary embodiment, the nonwoven web has a recovery at least 50%, preferably at least 60%, more preferably of at least 70%, even more preferably of at least 80%, and most preferably of at least 90%.
Part of the softness perception is presented also by elongation at low force. Best rated nonwovens typically show a certain level of adaptation to the object they are in contact with (e.g., human body). For example, when touching the nonwoven by hand, a better rating results when the fabric can elongate a bit and felt resistance to the finger is just right. For different applications, different elongation at low force is required.
In an exemplary embodiment, the nonwoven web has an MD elongation at 5 N force of at least 15%, preferably of at least 20%.
In an exemplary embodiment, the nonwoven web has an MD elongation at 5 N force of not more than 100%, preferably of not more than 80%, and most preferably of not more than 65%.
Elongation at low force requirements differ according to the application and can be controlled for example by level of prebonding or hydroentangling.
In an exemplary embodiment, the nonwoven web has an MD elongation at 5 N force in a range of 15% to 50%, preferably of 15% to 40%, more preferably of 15% to 35%.
In other exemplary embodiment, the nonwoven web has an MD elongation at 5 N force in a range of 30% to 100%, preferably of 30% to 80%, more preferably of 40% to 80%, even more preferably of 40% to 70%, and most preferably 50% to 65%.
In an exemplary embodiment, the nonwoven web has an CD elongation at 5 N force of 25 to 60%.
In an exemplary embodiment, the nonwoven web has an MD elongation of at least 60%, preferably of at least 70%, more preferably of at least 80%, even more preferably of 90%, and most preferably of at least 100%.
In an exemplary embodiment, the nonwoven web has an CD elongation of at least 50%, preferably of at least 60%, more preferably of at least 70%, even more preferably of 80%, and most preferably of at least 90%.
Spunmelt nonwoven according to the invention needs to also exhibit a certain level of stability required for conversion to the final product and for use of the final product.
In an exemplary embodiment, the nonwoven web has a basis weight of at least 15 gsm, more preferably at least 20 gsm, and most preferably at least 25 gsm.
In an exemplary embodiment, the nonwoven web has a basis weight of 200 gsm or less, preferably 150 gsm or less, more preferably 100 gsm or less, even more preferably 75 gsm or less, and most preferably 50 gsm or less.
In an exemplary embodiment, the nonwoven web has a basis weight in a range of 200 gsm to 15 gsm, preferably in a range of 100 gsm to 15 gsm, more preferably in a range of 85 to 15 gsm, more preferably in a range of 50 gsm to 15 gsm, more preferably in a range of 50 gsm to 20 gsm, and most preferably in a range of 50 gsm to 25 gsm.
In an exemplary embodiment, the nonwoven web has an MD tensile strength of at least 4 N/cm.
In an exemplary embodiment, the nonwoven web has a normalized MD tensile strength of at least 0.26 N·m2/g·cm, preferably of at least 0.28 N·m2/g·cm, more preferably of at least 0.30 N·m2/g·cm, more preferably of at least 0.30 N·m2/g·cm, and most preferably of at least 0.32 N·m2/g·cm.
In an exemplary embodiment, the nonwoven web has a CD tensile strength of at least 2 N/cm.
In an exemplary embodiment, the nonwoven web has a normalized CD tensile strength of at least 0.13 N·m2/g·cm, preferably of at least 0.15 N·m2/g·cm, more preferably of at least 0.17 N·m2/g·cm, more preferably of at least 0.19 N·m2/g·cm, and most preferably of at least 0.20 N·m2/g·cm.
In an exemplary embodiment, the nonwoven web does not exhibit two sidedness in terms of abrasion rating.
Spunbonded nonwovens are produced on spinning beams from polymer resin or resin mixture where also various additives can be added. In an exemplary embodiment according to the invention, multicomponent filaments with crimpable cross-section are formed comprising at least two components that may have different melt flow rate, melting points, crystallinity, molecular weight distributions, chemistries, and combinations of such differences such that fiber crimp can be obtained.
As shown in
According to an exemplary embodiment of the invention, the second component of formed multicomponent filaments has lower melting temperature (so called bonding polymer) and is present on at least a part of the filament surface.
According to an exemplary embodiment of the invention, the filaments might comprise a bonding polymer forming at least 20% of the area of the filament surfaces, preferably at least 35% of the area of the filament surfaces, even more preferably at least 50% of the area of the filament surfaces.
According to an exemplary invention, filaments might be formed of two components in mutual ratio 90:10 to 10:90, preferably in mutual ratio 70:30 to 30:70, more preferably in mutual ratio 60:40 to 40:60.
The bonding polymer can be chosen from a group of polyolefins (i.e. polypropylene or polyethylene), low-melting polymers including low-melting polyester grades (i.e. aliphatics such as polylactic acid, or aromatics such as polyethylene terephthalate), and copolymers or blends of suitable polymers. It is within the scope of the invention that the bonding polymer is selected from the group of polyesters that also includes polyester copolymers (coPET) or polylactide copolymers (COPLA).
According to the exemplary embodiment of the invention, filaments may have a first component with polymer or polymer mixture of a melt temperature higher than the bonding polymer's melt temperature in second component, preferably the melt temperature difference is at least 5° C., preferably at least 3° C.
The first component polymer or part of the first component polymer mixture can be chosen from a group of polyolefins (e.g., polypropylene or polyethylene), polyesters (e.g., aliphatics such as polylactic acid or aromatics such as polyethylene terephthalate), and copolymers or blends of suitable polymers. It is within the scope of the invention that the first polymer is selected from the group of polyesters that also includes polyester copolymers (coPET) or polylactide copolymers (COPLA).
The preferred combinations of components for the bi-component filaments according to the invention are PP1/PP2, PP/PE, PET/PE, PET/PP, PET/PET, PLA/PLA, PLA/PE and PLA/PP, wherein PP, PE, PET and PLA may include virgin polymer, copolymer or blends of thereof. For example, a combination of PP in one component and blend of the same PP with other PP with different melt-flow-index and/or different melt temperature are known as good crimping compositions (as described for example in U.S. Pat. Nos. 11,021,821 and 10,435,829 and U.S. Patent Application Publication 2019/0233994). Polymer composition can also contain a suitable process additive to enhance crimping, such as, for example, crystalizing agents, slip agent, process agents, etc.
Other formulation changes may also be employed, e.g., addition of CaCO3. One skilled in the art would appreciate many other formulation changes, such as, for example, color additives, process additives, filament surface modulators, such as, for example, softness enhancers, etc., dependent on further requirements of the final fabric properties or specific spunmelt line requirements.
Polymer or polymer mixtures for each filament component are dosed through dosing system 1a, 1b, separately melted in extrusion systems 2a, 2b to form first and second components of the filaments and fed into spinneret nozzles to form the filaments.
Filaments are created by means of spinning in spinnerets 3. The arrangement of the filaments may be optimized by their alternating placement, by means of which a condition can be attained, where each of the individual filaments has a very similar weight and is supplied with cooling air of very similar temperature. The spinnerets 3 may have varying numbers of capillaries and likewise varying diameters (d) and lengths (L) of these capillaries. The length (L) is, as a rule, calculated as the multiple of the diameter of the capillary and the area is selected in the range from 2 to 10 l/d. The number of capillaries needs to be selected on the basis of the required final diameter of the filament and the required or planned total processed amount of polymer together with the required filament spinning speed. The number of capillaries may change in the range of 800-7000 capillaries per meter, at which it is possible to attain filaments with a diameter in the range from 8 to 45 μm. The diameter of the capillaries and the filament speed are selected to achieve the correct level of potential shrinkage of the final filament. The speed of the filament 6 is preferably in the range of 1000 to 10 000 m/min and the diameter of the capillaries is preferably in the range of 200 to 1000 μm, which achieves a suitable process draw ratio in the range of 200 to 1300 in the case of circular capillaries. To achieve the required level of production line productivity, in the case of circular capillaries, it is most advantageous to have a draw ratio in the range from 300 to 800. Non-circular capillaries, as a rule, exhibit higher draw ratio values, which are to a significant degree dependent on the shape of the capillary and on the relative ratio of its surface and volume.
Formed filaments 6 subsequently pass through a cooling device. A monomer suction device 4 is arranged between the spinneret and the cooling device to remove gases in the form of decomposition products, monomers, oligomers and the like generated during the spinning of the fibers. The monomer suctioning device 4 comprises suction openings or suction gaps.
In the cooling device, cooling process air 5 is applied to the fiber curtain from the spinneret from opposite sides. The cooling device may be one or may be divided into two or more sections, which are arranged in series along the flow direction of the fibers. Thus, process air of a relatively higher temperature (for example 60° C.) can be applied to the fibers at an earlier stage in upper chamber section and process air of a relatively lower temperature (for example 30° C.) can be applied to the fibers at a later stage in lower chamber section. The supply of process air takes place via air supply cabins. The cabin pressure within can be more than 3000 Pascal above ambient pressure and is preferably not higher than 9000 Pascal.
The volume and temperature of the cooling process air 5 is set in such a way to achieve the correct draw ratio and correct cooling conditions. It has been found that in respect to exemplary embodiments of this invention, it is useful when the ratio of the cooling air volume to the spun polymer is in the range of 20:1 to 45:1. The volume and temperature of the cooling air are controlled in the cooler (6). This temperature can be set in the range of 10° C. to 90° C., preferably in the range of 15° C. to 80° C., so that the cooling conditions can be used in specific cases to support filaments self-crimping. In an exemplary embodiment, polyolefin filaments are produced with cooling process air in a range of 15° C. to 40° C. The cooling conditions determine how quickly the filaments during the spinning process cool down from the melting temperature to the glass transition temperature. For example, setting a higher cooling air temperature results in a delayed cooling of the filaments. In practice, for the purposes of this invention, achieving the required and usable cooling air temperature range is easier when the cooling process air 5 is divided into two zones in which the temperature range can be controlled separately. In the first zone, which is located in the vicinity of the spinneret, the temperature can be set in the range of 10° C. to 90° C., preferably in the range of 15° C. to 80° C. and most preferably in the range of 15° C. to 70° C. In the second zone, which is located in the direct vicinity of the first zone, the temperature can be set in the range of 10° C. to 80° C., preferably in the range of 15° C. to 70° C. and most preferably from 15° C. to 45° C.
According to an exemplary embodiment of the invention, the pressure difference between the ambient pressure and the pressure in the process air cabin is at least 3000 Pascal, preferably at least 3400 Pa, with advantage at least 3800 Pascal.
According to an exemplary embodiment of the invention, the pressure difference between the ambient pressure and the pressure in the process air cabin is at most 9000 Pascal, preferably at most 8000 Pa, even more preferably at most 7000 Pascal, and most preferably at most 6500 Pascal.
According to an exemplary embodiment of the invention, the pressure difference between the ambient pressure and the pressure in the process air cabin is within the range of 3000 Pascal to 9000 Pascal, preferably in the range of 3400 Pascal to 7000 Pascal, more preferably in the range of 3400 Pascal to 6500 Pascal, even more preferably in a range of 3800 Pascal to 6500 Pascal, and most preferably in the range of 3800 Pascal to 5000 Pascal.
A drawing device to draw and stretch the fibers is arranged below the cooling device. The drawing device includes an intermediate channel, which preferably converges and gets narrower with increasing distance from the spinnerette. In one embodiment the converging angle of the intermediate channel can be adjusted. After the intermediate channel the fiber curtain enters the lower channel.
The volume and temperature of the cooling process air 5 is set to achieve the correct draw ratio and correct cooling conditions. It has been found that in respect to this invention, it is useful when the ratio of the cooling air volume to the spun polymer is in the range of 20:1 to 45:1. The volume and temperature of the cooling air are controlled. This temperature can be set in the range of 10° C. to 90° C., preferentially in the range of 15° C. to 80° C., so that the cooling conditions can be used in specific cases to control self-crimping of the filaments. The cooling conditions determine how quickly the filaments during the spinning process cool down from the melting temperature towards the glass transition temperature. For example, setting a higher cooling air temperature results in a delayed cooling of the filaments. In practice, for the purposes of this invention, achieving the required and usable cooling air temperature range is easier when the cooler is divided into two zones in which the temperature range can be controlled separately. In the first zone, which is located in the vicinity of the spinneret, the temperature can be set in the range of 10° C. to 90° C., preferentially in the range of 15° C. to 80° C. and most preferentially in the range of 15° C. to 70° C. In the second zone, which is located in the direct vicinity of the first zone, the temperature can be set in the range of 10° C. to 80° C., preferentially in the range of 15° C. to 70° C. and most preferentially in the range of 15° C. to 45° C.
The cooling device and the drawing device, including intermediate channel and lower channel, are together formed as a closed integral structure, meaning that over the entire length of the integral structure, no major air flow can enter from the outside and no major process air supplied in the cooling device can escape to the outside. Some fume extraction devices directly under the spinneret extracting a minor air volume can be incorporated.
Inside the cooling and drawing device, the filaments 6 are usually cooled by means of a flowing fluid, primarily by means of cooling process air 5. As stated above, it is necessary that the potential crimping of filaments is evenly distributed throughout the entire range of length, width and thickness of the batt. The characteristics related to the filament 6 can be modified by adaptation of the draw ratio, cooling air/polymer ratio, and the speed of the filament, whilst, according to the invention, these parameters are practically identical for each individual filament.
The filaments 6 leaving the drawing device are then passed through a laying unit, which comprises a diffuser having a convergent section and an adjoining divergent section. The diffuser angles, in particular the diffuser angles in the divergent regions are adjustable. Also, the position of the diffusers and distance from the conveyor belt 10 can be adjusted. Two diffusers might be used, with one diffuser following another diffuser in the filament path. Between the diffusers there might be a gap through which ambient air is sucked into the fiber flow space.
After passing through the laying unit, the fibers 6 are deposited as nonwoven batt 7 on a conveyor belt 10. A suctioning device 8 is arranged below the laydown area of the conveyor belt 10 to suck off process air. Specifically, a plurality of suctioning devices 8 can be arranged in series along the moving direction of the conveyor belt 10. The suctioning device 8 sitting directly below the laydown area is set to the highest air extraction speed, the subsequent suctioning device the second highest, and so forth.
In an embodiment according to the invention utilizing self-crimping filaments, these filaments upon leaving the diffuser are released from the aerodynamic drawing forces and subsequently laid down in the vacuum supported web formation zone, where the filaments crimp as soon as the vacuum is at its lowest force at the edge of the suction zone—in the MD—and by means of such crimped filaments a resulting gain of thickness of the fabric can be achieved.
A subsequent step of applying heat through the batt might be performed to consolidate the filament orientation and 3-dimensional structure, which in turn creates the thickness/bulkiness of the fabric batt. The parameter settings for hot fluid/hot air temperature, penetration speed and volume are mainly dependent upon:
Once deposited, the nonwoven layer undergoes a first thermal pre-consolidation step 9. In one exemplary embodiment according to the invention, the batt is guided through the gap between a pair of pre-consolidation rollers. In other exemplary embodiments according to the invention a hot air knife or through-hydrodynamic unit can be used. The pre-consolidation step can serve also as a heat applying step described above.
The amount of energy transferred to the filament batt 7 is controlled by a process parameter that enables the filaments to be softened or pre-melted only to a certain degree, which ensures the attainment of good cohesion between the individual filaments. After the necessary cohesion between the filaments is attained, the fibrous batt can be transported on the formation belt without affecting or risking destruction/damage by the effect of forces that arise during this transport. This first pre-consolidation procedure is, likewise, sufficient for moving the filament batt to a different deposition zone on a production line made up of multiple spinning beams or to, for example, a second pre-bonding unit to perform a second pre-consolidation step incorporated in the production line. The energy transferred to the filaments may be also sufficient for activation of self-crimping of the filaments.
In an exemplary embodiment according to the invention, the batt is guided through the gap between a pair of pre-consolidation rollers having a temperature of 20-100° C. lower than the melting temperature of bonding polymer in the filament, and preferably 30-80° C. lower than melting temperature of bonding polymer in the filament.
In a particular exemplary embodiment according to the invention, the polyolefin-based batt is guided through the gap between a pair of pre-consolidation rollers having a temperature in a range of 50° C. to 180° C., preferably in a range of 80° C. to 150° C., and more preferably of 110° C. to 130° C.
In an exemplary embodiment according to the invention, the first pre-consolidation of the batt is performed by application of hot air. The method according to the invention includes the determination of balance between the pre-consolidation parameters: pre-consolidation temperature, pre-consolidation air speed and the pre-consolidation time. Pre-consolidation time should be understood to mean the time during which the batt of filaments is modified by the pre-consolidation air.
The pre-consolidation time of the filament batt may be in the range of 1 to 10000 ms, preferentially in the range of 2 to 1000 ms and most preferably in the range of 4 to 200 ms.
The speed of the pre-consolidation air that is used in this pre-consolidation unit is set to the range of 0.1 to 10 m/s, and preferably in the range of 0.8 to 4 m/s. The consolidation temperature during pre-consolidation may be in the range of 80° C. to 200° C., and preferably in the range of 100° C. to 180° C. In an exemplary embodiment, the pre-consolidation temperature is in the range of 90° C. to 150° C., preferably 110° C. to 140° C.
Without being bound by theory, it is believed that the described process conditions leads to formation of an irregular crimp structure. The formed, cooled, and drawn filaments have energy to form regular crimp (alpha helix type), but being under tension during cooling and forming, they are typically narrower and become crimped earliest during or after laydown, when due to filament-to-filament interaction an irregular crimp structure with crimp-driven bows is created. Without being bound by theory, it is believed that conflict of opposing forces of filament-to-filament interaction and regular forces created by crimpable cross-sections provides one component of the inner tension in the nonwoven according to the invention.
Once the nonwoven batt is deposited from all beams in the production line and after the first pre-consolidation step 9, the batt may undergo a second pre-consolidation step 11. Second pre-consolidation step 11 uses heat for pre-consolidation before hydroentanglement bonding 12. The second pre-consolidation step 11 creates a higher level of filament-to-filament bonding, for example in a form of bonding points (e.g., when hot air is used) or in a form of bonding impression by applying heat and pressure (e.g., when calender rollers are used). The level of prebonding may be set based on requirements for the nonwoven according to the invention. For example, for absorbent nonwoven products with very low requirements on abrasion and tensile, the second pre-consolidation step might not be used at all. For example, for wipes with medium requirements on abrasion and tensile, the second pre-consolidation step may be applied at a lower level. For example, for nonwoven in hygiene applications, with higher requirements on abrasion and tensile, the second pre-consociation step may be applied at a higher level. After all the pre-consolidation steps, the batt still permits substantial parts of the filaments to be freely moveable such that they can be repositioned.
In an exemplary embodiment according to the invention, second pre-consolidation 11 of the batt 7 is performed by means of hot air. The process settings and the machinery used to apply hot air to bond the filamentary batt comprising crimped filaments should be capable of providing the needed hot air by means of constant flow rates and temperature both in the CD as well as in the MD, which also means that they are constant over the time. This requirement applies for all hot air supply devices such as the hot air knife, hot airfield, thermobonding oven with drums, flat belt oven or combinations of drum bonding and flat belt bonding. Process condition settings are dependent on many parameters including, for example, chosen technology, character of batt, line speed, etc. The process conditions may be set to reach homogenously pre-bonded batt, with no strata (as described in PCT Publication WO2022089676) formed in the fabric. In other words, the interfilamentary conjunction density is homogenous through each layer and there is no “skin” formed at the surface of the nonwoven batt.
In an exemplary embodiment according to the invention, second pre-consolidation 11 of the batt 7 is performed by means of a hot pair of calender rolls. Process condition settings are dependent on many parameters including, for example, chosen technology, character of batt, line speed, etc. The process conditions may be set to obtain bonding impressions that are not fused through the fabric thickness. In other words, bonding impressions are present on both sides of fabric with the bonding impressions connected by parts of filaments. In this regard,
In an exemplary embodiment according to the invention, bonding impressions on both side of fabric creates a space inside the fabric, increasing inner void volume of the fabric (see the difference of inner volume on
First and second pre-consolidation steps 9, 11 can each be performed using one or more units and can be combined. For example, first pre-consolidation step 9 can be performed by compact rollers and the second pre-consolidation step 11 can be performed by calender rolls. For example, first pre-consolidation step 9 can be performed by hot air knife and the second by calender rolls. For example, first pre-consolidation step can be performed by compact rollers and the second by hot air oven. For example, first pre-consolidation step can be performed by hot air knife and the second by hot air oven. For example, first pre-consolidation step can be performed using compact rolls followed by hot air knife. For example, second pre-consolidation step can be performed by hot air oven followed by calender rolls or vice versa.
In general, it should be appreciated that the number and configuration of spinning beams is not limited to that shown and described herein, and in other exemplary embodiments, the number and configuration of beams may be varied to achieve different web structures. For example, a single spunbond beam may be used to form nonwoven batt 7 on conveyor belt 10 having a single spunbond layer, or multiple spunbond beams may be used to form batt 7 having a multi-spundbond layer structure, such as, for example SS, SSS, SSSS, etc. Layers formed by multiple beams might be the same or very similar to each other in terms of filament-type, process parameters, etc. so that the layers are substantially indistinguishable from one another to thereby form what appears to be a single layer structure or they might be produced differently from one another thereby forming an evidently layered nonwoven product.
In another exemplary embodiment, only spunbond beam and meltblown beam are used to form nonwoven batt 7 on conveyor belt 10. According to further exemplary embodiments of the invention, plural elements may be incorporated in the system to form batt 7 with multiple respective layers, such as, for example SM, SMM, SSM, SSMM etc. Again, layers formed by multiple beams, typically multiple beams of same type, might be the same or very similar to each other in terms of filament-type, process parameters, etc. so that the layers are substantially indistinguishable from one another to thereby form what appears to be a single layer structure or they might be produced differently from one another thereby forming an evidently layered nonwoven product 13.
A meltblown layer may be deposited by a meltblown mechanism (or “beam”), preferably between spunbond layers. The meltblown (“MB”) layer can be formed by a meltblown process but may be formed by a variety of other known processes. For example, the meltblowing process includes inserting a thermoplastic polymer into a die. The thermoplastic polymer material is extruded through a plurality of fine capillaries in the die to form fibers. The fibers stream into a high velocity gas (e.g. air) stream which attenuates the streams of molten thermoplastic polymer material to reduce their diameter, which may be to the microfiber diameter. The meltblown fibers are quasi-randomly deposited by beam 3 over the moving web or moving web with spunbond layer laid by spinning beam 2 to form a meltblown layer. One, two or more meltblown blocks may be used in tandem to increase the coverage of fibers. The meltblown fibers can be tacky when they are deposited, which generally results in some bonding between the meltblown fibers of the web.
In accordance with an exemplary embodiment of the invention, nonwoven web 13 is consolidated from the pre-consolidated nonwoven batt 7 using one or more water jet injectors 12-1 in hydroentangle unit 12. Simplified water streams from water jet injector 12-1 are shown as 12-2. It should be noted that there can be one, two or more rows of water jets from one water jet injector. Also, water jets may be arranged in rows and may also be arranged in different patterns.
Combinations of spunbond layers of monocomponent filaments and one or more layers of self-crimping filaments are also within the scope of the present invention. The entire composite of such layers might be thermaly consolidated together and hydro-treated. Layers of moconomponent filaments will form typical loops formed by hydro-treatment, layers of self-crimping filaments will form both loops and crimp-driven bows according to the invention. With advantage the self-crimping layer is placed on top of non-crimping layers.
As shown in
According to an exemplary embodiment of the invention, belt 10 may incorporate one or more screens (not shown) each of them with a predetermined pattern for supporting precursor nonwoven batt 7 while it is being hydraulically bonded by one or more respective water injectors 12-1. As explained in further detail below, the one or more screens may be replaced with one or more drums, that can be provided with a screen sleeve 10-1 (
As described above, filaments in the fabric 13 according to the invention has the natural tendency to form regular crimp (alpha helix type), but due to filament-to-filament interaction during and after laydown, they are not able to form regular crimp, but only irregular bows, loops, looped crossing, loose knots etc., what leads to constant inner tension. The irregular structure is partially fixed by thermal pre-bonding, preventing the formed structure from loosening, and preventing filaments from becoming free and forming helixes. Mechanical energy added to the system by hydroentangling even increases this inner tension by entangling the filaments. Parts of filaments might be pushed through the formed structure of other fibers, forming structures like loose knots, braids etc. and most typically forming hydroentagled loops. The combination of proper thermal pre-bonding and appropriate levels of hydroentangling leads to nonwoven fabrics with characteristics that are different from those of standard spunbond or calender bonded structures of crimped filaments. Formed inner fabric tension leads to bulky, soft nonwoven fabric with a high rating of “touch”-subjective haptic feedback from human respondents. Examples of structure of the fabric according to the invention are shown on
In accordance with a particular exemplary embodiment of the invention, the screen(s) or sleeves may comprise for example a pattern of pins for imparting apertures to the precursor nonwoven batt 7.
In accordance with an exemplary embodiment of the invention, the use of one or more drums, each drum being associated with one or more water injectors, results in a plurality of steps of water injection. The desired water pressure at each step depends on a number of parameters, including the number of water injection steps and the line speed. In general, the more water injection steps used in the process, the less pressure is required at each step to achieve the desired fabric properties. In other words, the energy flux attained using a number of water injectors each applying an amount of water pressure can also be attained by increasing the number of water injectors and decreasing the amount of water pressure applied by each injector. The desired water pressure at each step also depends at least partially on the line speed. Higher line speed requires higher pressure to maintain constant flux. In other words, the energy flux attained using a line speed and injector pressure can also be attained by reducing both the line speed and injector pressure.
Without being bound by theory, it is believed the preferred total water jet pressure applied to the precursor batt 7 may be expressed in terms of energy flux. In accordance with an exemplary embodiment, the preferred energy flux applied to the precursor batt 7 is at least 0.2 kWh/kg, preferably at least 0.3 kWh/kg, preferably at least 0.5 kWh/kg, preferably within the range of 0.2-3.0 kWh/kg, preferably within the range of 0.3-1.9 kWh/kg and also preferably within the range of 0.5-1.9 kWh/kg. The desired energy flux may be obtained by, for example, varying machine speed and/or water pressure at each water injector. Preferably, the desired energy flux is achieved by using one or more water injectors at a relatively lower pressure rather than less water injectors at a higher pressure. Energy flux may be calculated using the following formula:
where:
Preferred exemplary embodiments of the present invention involve the use of a relatively large amount of water injectors. Without being bound by theory, the use of a larger amount of injectors allows for higher line speed without having to increase injector pressure.
In an exemplary embodiment, the plurality of steps of water injection may include exposing the nonwoven precursor batt 7 to a plurality of water injectors with each water injector applying a pressure of 180 bar, preferably 200 bar or greater. In exemplary embodiments, the basis weight of the precursor nonwoven batt 7 is 15 gsm to 45 gsm and the line speed is 150 to 450 meters/minute, with a more specific example in which the precursor web has a basis weight of 25 gsm and the line speed is 200 meters/minute.
In an exemplary embodiment, the plurality of steps of water injection may include exposing the fully calender-bonded polyolefin based nonwoven precursor web 7 to two water injectors with each water injector applying a pressure of 250 bar, preferably 300 bar or greater. In exemplary embodiments, the basis weight of the precursor web 7 is 15 gsm to 45 gsm and the line speed is 150 to 450 meters/minute, with a more specific example in which the precursor web has a basis weight of 25 gsm and the line speed is 200 meters/minute.
In an exemplary embodiment, the plurality of steps of water injection may include exposing the fully calender-bonded polyolefin based nonwoven precursor web 7 to at least four water injectors with each water injector applying a pressure of 150 bar or greater. In exemplary embodiments, the basis weight of the precursor web 7 is 15 gsm to 45 gsm and the line speed is 150 to 450 meters/minute, with a more specific example in which the precursor web has a basis weight of 25 gsm and the line speed is 200 meters/minute.
In exemplary embodiments involving a combination of spunbond layers of monocomponent filaments and one or more layers of self-crimping filaments and in which the entire composite structure may be thermally pre-consolidated, the plurality of steps of water injection may include exposing the fully calender-bonded polyolefin based nonwoven precursor web 7 to four water injectors with each water injector applying a pressure of 80 bar or greater, preferably 100 bar or greater. In exemplary embodiments, the basis weight of the precursor web 7 is 15 gsm to 45 gsm and the line speed is 150 to 450 meters/minute, with a more specific example in which the precursor web has a basis weight of 40 gsm and the line speed is 275 meters/minute.
It should be noted that even though the energy from water jets is in the same range for hydroentagling as it described for hydroenhancing process in prior applications WO2006031656, WO2018112259; WO2022235652 or, but not limited to US 90/613013, the result is different. The key to this difference is the combination of a sleeve with increased rebound energy (for example MPC type) for hydroentangling in contrast to a sleeve with low rebound energy for softening the material (for example Wiremesh). As various types of machines are available in the field, a person skilled in the art would understand which combination of energy, pressure, jet unit design and sleeve design to use to reach a desired level of hydroentangling.
Hydroentangling consolidation step 12 might be followed by further treatment. For example, one or more hydroentangling units can be added to the process, performing hydro-enhancement of the fabric, including softening, aperturing, 3D shaping etc., as described for example in patent families WO2006031656, WO2018112259; WO2022235652.
The following Examples and Comparative Examples illustrate advantages of the present invention.
A 35 gsm spunmelt type nonwoven batt was produced online in a continuous process from a bicomponent filaments with side-by-side cross-section and an average fiber diameter of 20 μm. During the process, the filaments were produced and subsequently collected on a moving belt at a speed of 320 m/min.
Process settings:
A first side component was formed of a polypropylene (type 3155E5 from Exxon).
The other, second side component was formed of a mixture of two polypropylene resins with different melt-flow indices. The mixture was comprised of Exxon 3155E5 and Exxon 3684HL.
The batt was produced on REICOFIL 5 technology (Reifenhäuser Reicofil GmbH & Co. KG, Troisdorf, Germany) with three spunbond beams.
Formed batt was pre-consolidated in two steps.
First pre-consolidation step was performed by a compact roll at a temperature of 120° C.
Second pre-consolidation step was performed by a pair of heated rollers, where one roller had a raised regular homogenous pattern forming bonding impressions. Overall bonding area was 13.9%, with each one bonding impression having a surface area of 4.318 mm2 and with 3.2 bonding impression per 1 cm2. The temperature of the calender rollers (smooth roller/patterned roller) was 115° C./115° C. and the bonding pressure was 35 N/mm.
The pre-consolidated batt was hydroentangled with two drums having MPC screens and two injectors at each drum, each applying water pressure of 235 bar.
Each injector had two rows of holes, with the holes within each row spaced a distance of 0.6 mm from one another.
The resulting nonwoven web had material properties as shown in Tables 1-4.
A 40 gsm spunmelt type nonwoven batt was produced online in a continuous process from a bicomponent filaments with side-by-side crossection and a fiber diameter of 21 μm. During the process, the filaments were produced and subsequently collected on a moving belt at a speed of 320 m/min.
Process settings:
A first side component was formed of a mixture of a polypropylene resin (type 3155E5 from Exxon) with whitener (SCC-20790 PF from Standridge Color Corporation) and soft enhancing additives (Vistamaxx 7050BF from Exxon and slip aid from Americhem 65945-D1-200).
The other, second side component was formed of a mixture of two polypropylene resins with different melt-flow indices. The mixture was comprised of Exxon 3155E5 and Exxon 3684HL.
Formed batt was pre-consolidated in two steps.
First pre-consolidation step was performed by a compact roll at a temperature of 120° C.
Second pre-consolidation step was performed by a pair of heated rollers, where one roller had a raised regular homogenous pattern forming bonding impressions. Overall bonding area was 13.9%, with each one bonding impression having a surface area of 4.318 mm2 and 3.2 bonding impression per 1 cm2. The temperature of the calender rollers (smooth roller/patterned roller) was 115° C./115° C. and the bonding pressure was 35 N/mm.
The pre-consolidated batt was hydroentangled with two drums having MPC screens and two injectors at each drum, each applying water pressure of 235 bar.
Bonded batt was hydro-enhanced using one more drums having wire mesh screens and two injectors applying water pressure of 100 bar each.
Each injector had two rows of holes, with the holes within each row spaced a distance of 0.6 mm from one another.
The resulting nonwoven web had material properties as shown in Tables 1-4.
A 35 gsm spunmelt type nonwoven batt was produced online in a continuous process from a bicomponent filaments with side-by-side cross-section and an average fiber diameter of 20 μm. During the process, the filaments were produced and subsequently collected on a moving belt at a speed of 320 m/min.
Process settings:
A first side component was formed of a polypropylene (type 3155E5 from Exxon).
The other, second side component was formed of a mixture of two polypropylene resins with different melt-flow indices. The mixture was comprised of Exxon 3155E5 and Exxon 3684HL.
The batt was produced on REICOFIL 5 technology (Reifenhäuser Reicofil GmbH & Co. KG, Troisdorf, Germany) with three spunbond beams.
Formed batt was pre-consolidated in two steps.
First pre-consolidation step was performed by a compact roll at a temperature of 120° C.
Second pre-consolidation step was performed by a pair of heated rollers, where one roller had a raised regular homogenous pattern forming bonding impressions. The overall bonding area was 13.9%, with each one bonding impression having a surface area of 4.318 mm2 and 3.2 bonding impression per 1 cm2. The temperature of the calender rollers (smooth roller/patterned roller) was 115° C./115° C. and the bonding pressure was 35 N/mm.
The pre-consolidated batt was hydroentangled with two drums having MPC screens and two injectors at each drum, each applying water pressure of 235 bar.
The bonded batt was hydro-enhanced using one more drums having wire mesh screens and two injectors applying water pressure of 100 bar each.
Each injector had two rows of holes, with the holes within each row spaced a distance of 0.6 mm from one another.
The resulting nonwoven web had material properties as shown in Tables 1-4.
A 35 gsm spunmelt type nonwoven batt was produced online in a continuous process from a bicomponent filaments with side-by-side cross-section and an average fiber diameter of 20 μm. During the process, the filaments were produced and subsequently collected on a moving belt at a speed of 320 m/min.
Process settings:
A first side component was formed of a polypropylene (type 3155E5 from Exxon).
The other, second side component was formed of a mixture of two polypropylene resins with different melt-flow indices. The mixture was comprised of Exxon 3155E5 and Exxon 3684HL.
The batt was produced on REICOFIL 5 technology (Reifenhäuser Reicofil GmbH & Co. KG, Troisdorf, Germany) with three spunbond beams.
Formed batt was pre-consolidated in two steps.
First pre-consolidation step was performed by a compact roll at a temperature of 120° C.
Second pre-consolidation step was performed by a pair of heated rollers, where one roller had a raised regular homogenous pattern forming bonding impressions. Overall bonding area was 13.9%, with each one bonding impression having a surface aca of 4.318 mm2 and 3.2 bonding impression per 1 cm2. The temperature of the calender rollers (smooth roller/patterned roller) was 115° C./115° C. and the bonding pressure was 35 N/mm.
The pre-consolidated batt was hydroentangled with two drums having MPC screens and two injectors at each drum, each applying water pressure of 235 bar.
Bonded batt was hydro-enhanced using one more drums having wire mesh screens and two injectors applying water pressure of 200 bar each.
Each injector had two rows of holes, with the holes within each row spaced a distance of 0.6 mm from one another.
The resulting nonwoven web had material properties as shown in Tables 1-4.
A 33 gsm spunmelt type nonwoven batt was produced online in a continuous process from a bicomponent filaments with side-by-side cross-section and an average fiber diameter of 20 μm. During the process, the filaments were produced and subsequently collected on a moving belt at a speed of 320 m/min.
Process settings:
A first side component was formed of a polypropylene (type 3155E5 from Exxon).
The other, second side component was formed of a mixture of two polypropylene resins with different melt-flow indices. The mixture was comprised of Exxon 3155E5 and Exxon 3684HL.
The batt was produced on REICOFIL 5 technology (Reifenhäuser Reicofil GmbH & Co. KG, Troisdorf, Germany) with three spunbond beams.
Formed batt was pre-consolidated in two steps.
First pre-consolidation step was performed by a compact roll at a temperature of 120° C.
Second pre-consolidation step was performed by a pair of heated rollers, where one roller had a raised regular homogenous pattern forming bonding impressions. Overall bonding area was 13.9%, with each one bonding impression having a surface area of 4.318 mm2 and 3.2 bonding impression per 1 cm2. The temperature of the calender rollers (smooth roller/patterned roller) was 115° C./115° C. and the bonding pressure was 35 N/mm.
The pre-consolidated batt was hydroentangled with two drums having MPC screens and two injectors at each drum each applying water pressure of 235 bar.
The bonded batt was hydro-enhanced using one more drum having wire mesh screen and two injectors applying water pressure of 150 bar each.
Each injector had two rows of holes, with the holes within each row spaced a distance of 0.6 mm from one another.
The resulting nonwoven web had material properties as shown in Tables 1-4.
A 35 gsm spunmelt type nonwoven batt was produced online in a continuous process from a bicomponent filaments with side-by-side cross-section and an average fiber diameter of 20 μm. During the process, the filaments were produced and subsequently collected on a moving belt at a speed 320 m/min.
Process settings:
A first side component was formed of a polypropylene (type 3155E5 from Exxon).
The other, second side component was formed of a mixture of two polypropylene resins with different melt-flow indices. The mixture was comprised of Exxon 3155E5 and Exxon 3684HL.
The batt was produced on REICOFIL 5 technology (Reifenhäuser Reicofil GmbH & Co. KG, Troisdorf, Germany) with three spunbond beams.
Formed batt was pre-consolidated in one step.
The pre-consolidation step was performed by a compact roll at a temperature of 120° C.
The pre-consolidated batt was bonded by a pair of heated rollers, where one roller had a raised regular homogenous pattern forming bonding impressions. Overall bonding area was 13.9%, with each one bonding impression having a surface area of 4.318 mm2 and 3.2 bonding impressions per 1 cm2. The temperature of the calender rollers (smooth roller/patterned roller) was 167° C./162° C. and the bonding pressure was 75 N/mm.
The resulting nonwoven web had material properties as shown in Table 1-4.
A 35 gsm spunmelt type nonwoven batt was produced online in a continuous process from a monocomponent polypropylene filament. During the process, filaments with an average fiber diameter of 21 μm were produced and subsequently collected on a moving belt.
First pre-consolidation step was performed by a compact roll at a temperature of 125° C.
Second pre-consolidation step was performed by a pair of heated rollers, where one roller had a raised regular homogenous pattern forming bonding impressions. Overall bonding area was 13.9%, with each one bonding impression having a surface area of 4.318 mm2 and 3.2 bonding impression per 1 cm2. The temperature of the calender rollers (smooth roller/patterned roller) was 125° C./125° C. and the bonding pressure was 35 N/mm.
The pre-consolidated batt was hydroentangled with two drums having MPC screens and two injectors at each drum, each applying water pressure of 235 bar.
A 40 gsm spunmelt type nonwoven batt was produced online in a continuous process from a bicomponent filaments with side-by-side cross-section and an average fiber diameter of 18 μm. During the process, the filaments were produced and subsequently collected on a moving belt at a speed of 275 m/min.
Process settings:
A first side component was formed of a polypropylene (type 3155E5 from Exxon).
The other, second side component was formed of a mixture of two polypropylene resins with different melt-flow indices. The mixture was comprised of Exxon 3155E5 and Exxon 3684HL.
The batt was produced on REICOFIL 5 technology (Reifenhäuser Reicofil GmbH & Co. KG, Troisdorf, Germany) on three spunbond beams. The third beam was running composition as described above, while the first and second beams provided monocomponent filaments (without any selfcrimp potential). The only component in the monocomponent filament was formed of a polypropylene (type 3155E5 from Exxon).
Formed batt was pre-consolidated in two steps.
First pre-consolidation step was performed by a compact roll at a temperature of 120° C.
Second pre-consolidation step was performed by a pair of heated rollers, where one roller had a raised regular homogenous pattern forming bonding impressions. Overall bonding area was 20.5%. The temperature of the calender rollers (smooth roller/patterned roller) was 115° C./115° C. and the bonding pressure was 35 N/mm.
The pre-consolidated batt was hydroentangled with four drums having MPC screens and two injectors at each drum each applying water pressure of 100 bar.
Each injector had two rows of holes, with the holes within each row spaced a distance of 0.6 mm from one another.
The resulting nonwoven web had material properties as shown in Tables 1-4.
As observed from tables 1 to 4, process conditions on hydroentangle bonding have a mild influence on final properties of the fabric, with the most noticeable effect on abrasion resistance. Although bonding is primarily performed on the 1st two drums, the tables above show that increased pressure on the third drum improves bonding. With increasing bonding intensity, lower abrasion values represent an improved fiber “tie-down.” Abrasion values of 80 cycles can be achieved, which is often appropriate for hygiene applications. In general, it can be said, that for e.g., for diapers, there should be reached at least a rating of 1 to 2 at 80 cycles. For less safety sensitive applications lower cycle counts are often used for testing, further improving the overall abrasion rating. For example, Example 3 shows results at 32 cycles.
Machine direction and cross direction handle-o-meter (HOM) were also inversely proportional to drum 3 injector pressures. This shows that increased pressure improves bonding and drape. Lower HOM is known to translate to an improved perceived softness and haptic feel. It should be noted that comparative fabric has higher HOM values and perceived softness is more coarse and less drapable-like a standard nonwoven material. On the contrary, fabric according to the inventions is felt as superior.
Compared to other examples according to the invention, Example 2 had the highest perception of softness. Although Example 5 with the highest pressure (4×235 bar and 2×200 bar) had a lower HOM on average, Example 2 felt softer via a haptic hand-panel study. This was likely due to the presence of the softening additives. An increase in basis weight was also realized at the same throughput and belt speed as compared to the other examples. This was due to the presence of Vistamaxx, which causes the web to neck in and shift basis weight upward. It is possible that softness can be improved with a reduction in basis weight and the use of injectors on softening drum C3.
Contrary to standard spunbonds that contain Vistamaxx, an increase in thickness was realized in Example 2 as compared to Examples 1 and 3-5. This may have been due to a lower level of bonding. The increased thickness resulted in the perception of a premium and cushiony material. The higher elasticity in the Vistamaxx containing fibers likely affected the ability to bond at comparable pressures. Due to this, the abrasion value was rated a maximum of 5. With some process optimization, Example 5 would likely have a lower HOM than others with improved abrasion resistance.
Example 8 differs from all previous examples according to the invention in that it includes a layer according to an exemplary embodiment of the invention in combination with two layers of monocomponent filaments. It should be highlighted, that even one layer according to the invention can improve overall softness and other desired properties of nonwovens. For example, the bulk of the layered fabric, combining thickness and basis weight, may be improved. The presence of two monocomponnent layers decreases elongation at 5 N in the MD direction to the level of the comparative example 7. To reach a desired value according to the invention, the crimped layer itself would need to be measured.
All examples according to the invention were analyzed using SEM microscopy (see some examples on
The “basis weight” of a nonwoven fabric was measured using testing methodology according to norm EN ISO 9073-1:1989 (corresponding to methodology WSP 130.1). For measurement, 10 layers of nonwoven fabric were used, whilst the sample size was 10×10 cm2.
The “tensile strength” and “elongation” of a nonwoven fabric were measured using testing methodology according to WSP 110.4.R4 (12) standard. Tensile strength can be expressed also as “MDT” for MD direction and “CDT” for CD direction. Accordingly, elongation can be also expressed as “MDE” for MD direction and “CDE” for CD direction. Normalized tensile strength or normalized elongation refers to tensile strength or elongation divided by nonwoven basis weight.
“Thickness” or “measured height” of a nonwoven material was determined by means of a testing measurement methodology pursuant to European norm EN ISO 9073-2:1995 (corresponds to methodology WSP 120.6), which is modified in the following manner:
1. The material is to be measured by using a sample that is taken from production without being subjected to higher deformation forces or without being subjected to the effect of pressure for longer than a day (for example by the pressure exerted by the roller on the production equipment), whilst otherwise the material must be left for at least 24 hours laying freely on a surface.
2. The total weight of the top arm of the measuring machine including additional ballast is 130 g.
“Bulk”, “bulkiness” or “bulk density” of a nonwoven fabric is expressed in kg/m3 and is calculated by dividing the “basis weight” in g/m2 by “thickness” in mm.
“Thickness to Basis Weight ratio” of a nonwoven fabric is expressed in dm3/kg or 1 (litres) to 1 kg and is calculated as “thickness” in mm*1000 divided by “basis weight” in g/m2.
The “stiffness” of a nonwoven fabric is expressed by the measurement “Handle-O-Meter” (HOM) and was determined according to the international norm WSP 90.3. The size of the sample, unless noted otherwise for the measured value, is 100×100 mm. HOM is measured in the MD and in the CD direction separately. Unless the MD or CD direction is specified, the arithmetic mean of these two values is taken.
The term “regeneration” or “recovery” of bulkiness here relates to the ratio between the thickness of the fabric after the release of the acting load and the initial thickness of this fabric. The thickness of a fabric was measured pursuant to norm EN ISO 9073-2:1995 whilst using a preliminary load force equivalent to a pressure of 0.5 kPa. The procedure for the measurement of regeneration consists of the following steps:
1. Preparation of fabric samples of dimensions 10×10 cm
2. Measurement of the thickness of 1 piece of fabric
3. Measurement of the thickness of 5 pieces of fabric placed on top of each other by using a preliminary load force equivalent to a pressure of 0.5 kPa (Ts)
4. Application of a load on to 5 pieces of fabric placed on top of each other (by a pressure of 2.5 kPa) on a thickness measurement device for 5 minutes
5. Release the device and wait for 5 minutes
6. Measurement of the thickness of 5 pieces of fabric placed on top of each other
by using a preliminary load force equivalent to a pressure of 0.5 kPa (Tr)
7. Calculation of regeneration according to the following equation:
Regeneration=Tr/Ts (without unit)
The term “compressibility” here relates to the distance in millimetres by which a nonwoven fabric is compressed by the effect of a load defined during the measurement of “flexibility”. It can be calculated also as the product of resilience (without unit)*thickness (mm). The “elasticity” or “resilience” of a nonwoven fabric was measured using testing methodology according to norm EN ISO 964-1, which is modified in the following manner:
1. The thickness of one fabric layer is measured.
2. Several samples of the fabric are prepared so that their total thickness after being stacked on top of each other is at least 4 mm, ideally 5 mm. The group of fabric pieces stacked on top of each other contain at least 1 piece of fabric.
3. The thickness of these stacked fabric samples is measured
4. A force of magnitude 5 N is allowed to act on to this group of stacked fabric samples at a load speed of 5 mm/min
5. The distance corresponding to the movement of the clamping elements is measured
6. Resilience is calculated according to this equation:
R (without unit)=T1 (mm)/T0 (mm)
or
R (%)=T1 (mm)/T0 (mm)*100%
“Martindale Average Abrasion Resistance Grade Test” or “Martindale”
Martindale Average Abrasion Resistance Grade of a nonwoven was measured using a Martindale Abrasion Tester. The test is conducted dry.
“Abrasion-weight loss” was measured according to the description in patent application U.S. Pat. No. 5,589,258 with amendment in weight loading: Abrasion resistance was measured on a Martindale abrasion tester using the test fabric as the abradent (i.e. fabric on fabric abrasion) and using weight loadings of 9 kPa. The average weight losses of the samples plus abradent after various numbers of abrasion cycles was measured and expressed as %.
“Type of fiber cross-section” is known from the process conditions, defined by the fiber forming die. In the event that the process conditions are unknown, the following estimation can be used:
A sample of the fabric is taken and pictures of the cross-sections of at least 20 fibers are taken. The cross-section is measured on the free part of the fiber, not in the bonding point or in a place of contact with another fiber, where deformation can be expected. For each cross-section, the component surface is marked out on the image separately for each component. The centre of mass is determined for each component based on the centroid or geometric center determination of the planar object and its position is recorded using the Cartesian coordinate system with the centre [0; 0] in the geometrical centre of the fiber cross-section. The deflection (D) of the centre of mass for each component in each fiber cross-section is calculated according to the following equation:
D=absolute value (x*y), where x and y are the coordinates of the centre of mass. When one of the x, y values is equal to 0 and not the other, the sample is discarded from evaluation)
The average value and standard deviation is calculated for each component.
The fiber is considered non-crimpable when the ((average deflection) plus (standard deviation)) to total fiber cross-section surface ratio is less than 5%.
The fiber is expected to be non-crimpable when the ratio ((average deflection) minus (standard deviation)) to total fiber cross-section surface ratio is less than 10%.
“Bond Area Percentage” was determined using ImageJ software (Vs. 1.43u, National Institutes of Health, USA) by identifying a single repeat pattern of bond impressions and unbonded areas and enlarging the image such that the repeat pattern fills the field of view. In ImageJ draw a box that encompasses the repeat pattern. Calculate area of the box and record to the nearest 0.01 mm2. Next, with the area tool, trace the individual bond impressions or portions thereof entirely within the box and calculate the areas of all bond impressions or portions thereof that are within the box. Record to the nearest 0.01 mm2. Calculate as follows:
Percent Bond Area=(Sum of areas of bond impressions within box)/(area of box)×100%
Repeat for a total of five non-adjacent ROI's randomly selected across the total specimen. Record as Percent Bond Area to the nearest 0.01%. Measurements are made on both specimens from each article. A total of three identical articles are measured for each sample set. Calculate the average and standard deviation of all 30 of the percent bond area measurements and report to the nearest 0.001 units.
Bond Area Percentage can be alternatively taken also from calender pattern technical specification, wherein overall bonding area is often defined.
The “Crimp frequency” of free filament was determined by simple measurement method. One filament of at least 3 inches in length in the free state (without any tension applied) was attached by one end to the holder so that it hangs freely in the space. A gauge was placed next to the filament with a zero-value starting approximately 0.5 inch below the filament attachment to the holder and capable of reading the length to the nearest 0.1 inch. The free-hanging fiber extended at least to 2.25-inch value on the gauge.
The suspended fiber was allowed to settle for 30 seconds under standard laboratory conditions and then the number of crimps, as shown in
The number of arcs read was converted to crimp frequency by dividing by the length read and reported in crimps per inch. The value was rounded to one decimal place. For example, as shown at the
At least 30 single filaments were measured and an average value (arithmetic mean) was calculated.
Providing the filament was extracted from the nonwoven or nonwoven batt, each filament independently shall be placed on the table and leave at standard conditions for 24 hours to reach its natural state. A filament in its natural state cannot comprise damaged areas—for example melted parts (for example from bonding impression) or parts where filament components are split one from each other. A person skilled in the art would understand what damages are contradictory to filament natural state. Filament in its natural state shall be measured in the same way as free filament.
The “AirPerm” or “AirPermeability” of a nonwoven fabric was measured using testing methodology according to norm ASTM D737-96.
The “Absorption Capacity” of a nonwoven fabric was measured using testing methodology according to norm EDANA 10.2-96.
The invention is applicable wherever a bulky nonwoven fabric with high level of softness is required—for example in the hygiene industry as various components of absorbent hygiene products (e.g. baby diapers, incontinence products, female hygiene products, changing pads, etc.), household (e.g. different types of wipes, parts of cleaning devices etc.) or in healthcare, for example, as a part of wound sponges and/or protective garments, surgical cover sheets, underlays and other barrier material products. Further uses are also possible in industrial applications, for example, as wipes, as a part of protective garments, in filtration, insulation, packaging, sound adsorption, footwear industry, automotive, furniture, etc. The invention is usable with advantage particularly in applications, where there is a requirement for increased softness combined with a requirement for endless fibers.
The invention is also with advantage applicable wherever the inner force is required—for example in filtration, insulation, sound absorption etc. In such applications, softness itself is not required, but for example stable void volume or defined pore distribution, shape stability etc. may be desirable. Such applications can take advantage of other enhanced parameters provided by this invention, which may or may not have been highlighted herein.
Now that embodiments of the present invention have been shown and described in detail, various modifications and improvements thereon can become readily apparent to those skilled in the art. Accordingly, the exemplary embodiments of the present invention, as set forth above, are intended to be illustrative, not limiting. The spirit and scope of the present invention is to be construed broadly.
This application claim priority to and the benefit of U.S. Provisional Application No. 63/459,380, entitled NONWOVEN FABRIC AND METHOD OF FORMING THE SAME and filed Apr. 14, 2023, the contents of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63459380 | Apr 2023 | US |
