CN116529431A

CN116529431A - Nonwoven fabric with improved touch and mechanical properties

Info

Publication number: CN116529431A
Application number: CN202180078173.3A
Authority: CN
Inventors: P·E·小罗林; A·I·阿根提斯; S·S·塔露里; S·德维塔; V·布达拉; A·特杰里佐福尔特斯
Original assignee: ExxonMobil Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 2020-11-19
Filing date: 2021-10-05
Publication date: 2023-08-01
Also published as: US20240011198A1; EP4248004A1; WO2022108673A1

Abstract

Multicomponent fibers for nonwoven fabrics and methods for making and using the same are disclosed. The multicomponent fiber may include a first component comprising a first polypropylene having an MFR of at least 30dg/min and a second polypropylene having an MFR of less than 20 dg/min. The multicomponent fiber may further comprise a second component comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and from about 10 to about 30 weight percent of one or more alpha-olefin derived units based on the total weight of the elastomer, wherein the propylene-based elastomer has an MFR of at least 40dg/min and a heat of fusion (Hf) of from about 3J/g to about 75J/g as determined by DSC.

Description

Nonwoven fabric with improved touch and mechanical properties

Cross Reference to Related Applications

The present application claims priority from USSN 63/116,027 filed 11/19 in 2020, which is incorporated herein by reference.

Technical Field

Embodiments of the present invention generally relate to nonwoven articles and fibers for making nonwoven articles. More particularly, embodiments of the present invention relate generally to multicomponent fibers for use in making nonwovens.

Background

Synthetic fibers and nonwoven fabrics often lack the soft feel or "hand" of natural fibers and fabrics. The different aesthetic sensations are due to the lack of "bulk" or "fluffiness" of the synthetic material, i.e. the space filling properties of natural fibers. Natural fibers are often not planar materials, but rather they exhibit some curl or texture in three dimensions, which leaves room between the fibers. Natural fibers can often be laid on a plane and have surfaces protruding from the plane, which is "three-dimensional".

However, synthetic fibers are substantially planar and therefore lack the bulk and hand of natural fibers. There are many methods to impart "bulk" or "bulk" to synthetic fibers or fabrics, including mechanical treatments such as crimping, air jet texturing, or pleating. These techniques are not readily applicable to spunbond nonwoven fabrics in a cost-effective manner.

Other attempts to increase "bulk" or "bulk" have involved "bicomponent" fibers comprising two different polymers arranged in an organized spatial arrangement such as "side-by-side" or "shell-core" within each fiber. However, there remains a need for bicomponent fibers having better bulk and softness without sacrificing strength.

Summary of The Invention

The present invention provides a multicomponent fiber for a nonwoven and a method of making a fiber for a fabric having suitable thickness and softness. The multicomponent fiber may include a first fiber component comprising a first polypropylene having a Melt Flow Rate (MFR) of at least 30dg/min and a second polypropylene having an MFR of less than 20 dg/min. The multicomponent fiber may further comprise a second fiber component comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and from about 10 to about 30 weight percent of one or more alpha-olefin derived units based on the total weight of the elastomer, wherein the propylene-based elastomer has an MFR of at least 40dg/min and a heat of fusion (Hf) of from about 3J/g to about 75J/g as determined by DSC.

The method of making a fiber for a fabric having a suitable thickness and softness may include forming a first polymer composition comprising a first polypropylene having an MFR of at least 30dg/min and a second polypropylene having an MFR of less than 20 dg/min. A second polymer composition may then be formed comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and from about 10 to about 30 weight percent, based on the total weight of the elastomer, of one or more alpha-olefin derived units and having an MFR of at least 40dg/min and a heat of fusion (Hf) of from about 3J/g to about 75J/g, as determined by DSC. A plurality of fibers configured side-by-side may be formed from the first polymer composition and the second polymer composition, and a fabric may be made from the plurality of fibers. The fabric may have a contact thickness of at least 0.40mm, a total hand of less than 20g, and MD and CD tensile strengths of at least 8N/5 cm.

Brief description of the drawings

So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. It is emphasized that the drawings are not necessarily to scale and that certain features and certain views of the drawings may be shown exaggerated in scale or in schematic in the interest of clarity and/or conciseness.

Fig. 1 depicts a graphical representation of complex viscosity (Pa x s) versus temperature (°c) for various samples prepared according to one or more embodiments provided herein.

FIG. 2 depicts a graphical representation of Tanδ versus temperature (. Degree. C.) for a sample prepared according to one or more embodiments provided herein.

Fig. 3 is a schematic cross-sectional view of a bulk characterization test method in accordance with one or more embodiments of the present invention.

FIG. 4 is a plot of normal force versus gap for various materials, produced by a bulk characterization test method, in accordance with one or more embodiments of the present invention.

Detailed Description

It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures or functions of the invention. Exemplary embodiments of components, arrangements and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided as examples only and are not intended to limit the scope of the invention. Further, the present disclosure may repeat reference numerals and/or letters in the various embodiments and figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations. Moreover, forming a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features are not in direct contact. Finally, the embodiments presented below may be combined in any combination, i.e. any element from one embodiment may be used in any other embodiment without departing from the scope of the disclosure.

In addition, certain terms are used in the following description and claims to refer to particular components. As will be appreciated by those of skill in the art, various entities may refer to the same components by different names, and thus the naming convention of the elements described herein is not intended to limit the scope of the present invention unless specifically defined otherwise herein. Moreover, the naming convention used herein is not intended to distinguish between components that differ in name but not function. In addition, in the following discussion and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to.

In the following discussion and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. The phrase "consisting essentially of means that the described/claimed composition does not include any other components that would substantially alter its characteristics by more than 5% of the characteristics, and in any event does not include any other components to a level of greater than 3% by mass. The phrase "consisting of" means that the described/claimed composition does not include any other components.

Unless expressly specified otherwise herein, the term "or" is intended to include both exclusive and inclusive cases, i.e., "a or B" is intended to be synonymous with "at least one of a and B". The indefinite articles "a" and "an" mean both the singular (i.e. "one") and the plural (i.e. one or more) unless the context clearly dictates otherwise. For example, embodiments using "an olefin" include embodiments in which one, two, or more olefins are used, unless specified to the contrary or the context clearly indicates that only one olefin is used.

The term "wt%" refers to weight percent, "vol%" refers to volume percent, "mol%" refers to mole percent, "ppm" refers to parts per million, and "ppm wt" and "wppm" are used interchangeably and refer to parts per million by weight. All concentrations herein are expressed on a total amount of the composition in question, unless otherwise indicated.

A detailed description of the multicomponent fibers for nonwoven fabrics and methods of using the same will now be provided. Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references to the "invention" may in some cases refer to only certain specific embodiments. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims. Each of the inventions will be described in greater detail below, including specific embodiments, variations, and examples, but the inventions are not limited to these embodiments, variations, or examples, which are included in the present disclosure to enable one of ordinary skill in the art to make and use the inventions when information in the present disclosure is combined with publicly available information and technology.

The multicomponent fiber can include at least a first fiber component and a second fiber component. The first fiber component may include at least one low MFR (i.e., 20MFR or less) polymer and at least one higher MFR (i.e., 30MFR or greater) polymer. The second fiber component may include at least one higher MFR (i.e., 30MFR or greater) polymer and at least one propylene-based elastomer (PBE). The one or more low MFR polymers and the one or more higher MFR polymers may be a polyolefin and/or a polyolefin copolymer. In certain embodiments, the one or more low MFR polymers and the one or more higher MFR polymers are both polypropylene (PP). In certain embodiments, the higher MFR polymer in the second fiber component is the same as the higher MFR polymer in the first fiber component.

It has surprisingly been found that by blending at least one low MFR (i.e. 20MFR or less) polymer with at least one higher MFR (i.e. 30MFR or more) polymer and using the blend on one side of the side-by-side fibers and the same blend of higher MFR polymer with at least one propylene-based elastomer (PBE) on the other side of the fibers, it is possible to produce a fabric having not only an increased z-direction thickness but also a significantly increased softness. It has also surprisingly been found that these PBE modified fabrics are stronger than fabrics without the PBE. In fact, the fabric produced provides exceptional softness while maintaining high tensile strength.

By "low MFR" is meant 20dg/min or less as measured according to ASTM D-1238 (2.16 kg load, 230 ℃). For example, the MFR of the low MFR polymer may be 20dg/min or less, 18dg/min or less, or 16dg/min or less. The MFR of the low MFR polymer may also range from as low as about 3, 5 or 7dg/min to as high as about 15, 18 or 20 dg/min.

By "higher MFR" is meant 30dg/min or greater as measured according to ASTM D-1238 (2.16 kg load, 230 ℃). For example, the MFR of the high MFR polymer may be 35dg/min or more, 40dg/min or more, or 45dg/min or more. The MFR of the high MFR polymer may also range from as low as about 25, 28 or 33dg/min to as high as about 38, 48 or 58 dg/min.

The term "monomer" or "comonomer" as used herein may refer to monomers used to form the polymer, such as unreacted compounds in the pre-polymerization form, as well as monomers after having been incorporated into the polymer, also referred to herein as "[ monomer ] derived units.

The term "copolymer" is intended to include polymers having two or more monomers, optionally with other monomers, and may refer to interpolymers, terpolymers, and the like. The term "polymer" as used herein includes, but is not limited to, homopolymers, copolymers, terpolymers, etc., and alloys and blends thereof. The term "polymer" as used herein also includes impact, block, graft, random and alternating copolymers. The term "polymer" shall further include all possible geometric configurations unless explicitly stated otherwise. Such configurations may include isotactic, syndiotactic and random symmetries.

The term "polymer" refers to any two or more identical or different repeating units/mer units or units. The term "homopolymer" refers to polymers having identical units. The term "copolymer" refers to a polymer having two or more units different from each other, and includes terpolymers and the like. The term "terpolymer" refers to a polymer having three units that differ from one another. When referring to units, the term "different" indicates that the units differ from each other by at least one atom or are isomerically different. Likewise, the definition of polymer as used herein includes homopolymers, copolymers, and the like. For example, when a copolymer is said to have a "propylene" content of 10wt% to 30wt%, it is understood that the repeat units/mer units (or simply units) in the copolymer are derived from propylene in the polymerization reaction, and that the derived units are present in an amount of 10wt% to 30wt%, based on the weight of the copolymer.

The term "elastomer" refers to any polymer that exhibits a degree of elasticity, where elasticity is the ability of a material that is deformed by a force (e.g., stretching) to at least partially return to its original dimensions after the force is removed.

The term "alpha-olefin" or "alpha olefin" refers to any linear or branched carbon and hydrogen compound having at least one double bond between the alpha and beta carbon atoms. For the purposes of this specification and the appended claims, when a polymer or copolymer is referred to as comprising an alpha-olefin, such as a polyalphaolefin, the alpha-olefin present in such a polymer or copolymer is the polymerized form of the alpha-olefin.

Polypropylene

The term "polypropylene" as used herein includes homopolymers and copolymers of propylene, or mixtures thereof. Products comprising one or more propylene monomers polymerized with one or more additional monomers may more commonly be referred to as Random Copolymers (RCP) or Impact Copolymers (ICP). Impact copolymers may also be referred to in the art as heterophasic copolymers. As used herein, "propylene-based" is intended to include any polymer containing propylene alone or in combination with one or more comonomers, where propylene is the major component (e.g., greater than 50 wt% propylene).

As used herein, "reactor grade" refers to a polymer that has not been chemically or mechanically treated or blended after polymerization to alter the average molecular weight, molecular weight distribution, or viscosity of the polymer. Especially excluded from those polymers described as reactor grade are those polymers that have been visbroken or otherwise treated or coated with peroxides or other prodegradants. However, for purposes of this disclosure, reactor grade polymers include those polymers that are reactor blends.

As used herein, "reactor blend" refers to a highly dispersed and mechanically inseparable blend of two or more polymers, either in situ due to sequential or parallel polymerization of one or more monomers in a series of reactors to form one polymer in the presence of another polymer, or by solution blending separately prepared polymers in parallel reactors. The reactor blend may be produced in a single reactor, a series reactor, or a parallel reactor, and is a reactor grade blend. The reactor blend may be produced by any polymerization process, including batch, semi-continuous, or continuous systems. Specifically excluded from "reactor blending" polymers are blends of two or more polymers wherein the polymers are blended ex situ, such as by physical or mechanical blending in a mixer, extruder or other similar device.

As used herein, "visbreaking" is the process of reducing the molecular weight of a polymer by subjecting the polymer to chain scission. The visbreaking process also increases the MFR of the polymer and may reduce its molecular weight distribution. Several different types of chemical reactions are available for visbreaking propylene-based polymers. One example is pyrolysis, which is accomplished by exposing the polymer to elevated temperatures, such as in an extruder at 270 ℃ or higher. Other methods are exposure to strong oxidants and exposure to ionizing radiation. Another approach to visbreaking is to add a prodegradant to the polymer. A prodegradant is a substance that promotes chain scission when mixed with a polymer and then heated under extrusion conditions. Examples of prodegradants that may be used include peroxides, such as alkyl hydroperoxides and dialkyl peroxides. These materials initiate free radical chain reactions at elevated temperatures, leading to cleavage of the polypropylene molecules. The terms "prodegradant" and "visbreaker" are used interchangeably herein. Polymers that undergo chain scission by a visbreaking process are referred to herein as "visbroken". Such visbroken polymer grades, particularly polypropylene grades, are often referred to in the industry as "controlled rheology" or "CR" grades.

As used herein, "catalyst system" refers to a combination of one or more catalysts with one or more activators and optionally one or more support compositions. An "activator" is any compound or component that is capable of increasing the ability of one or more catalysts to polymerize monomers into a polymer.

The polypropylene may have a weight average molecular weight (Mw) of 50,000 to 3,000,000g/mol, alternatively 90,000 to 500,000g/mol, and a molecular weight distribution (MWD, equal to the weight average molecular weight divided by the number average molecular weight, mw/Mn) in the range of 1.5 to 2.5 or 3.0 or 4.0 or 5.0 or 20.0. The polypropylene may have an MFR (2.16 kg/230 ℃) in the range of 10 or 15 or 18 to 30 or 35 or 40 or 50 dg/min.

Propylene-based elastomer (PBE)

The PBE contains propylene and from about 5wt% to about 30wt% of one or more alpha-olefin derived units, such as ethylene and/or C4-C12 alpha-olefins. In some examples, the alpha-olefin derived units or comonomers may be ethylene, butene, pentene, hexene, 4-methyl-1-pentene, octene, or decene. In one or more examples, the comonomer is ethylene. In some embodiments, the PBE consists essentially of, or consists of, propylene and ethylene alone. Some of the embodiments described below are discussed with reference to ethylene as the comonomer, but these embodiments are equally applicable to PBEs with other alpha-olefin comonomers. In this regard, the copolymer may be referred to simply as PBE, referring to ethylene as the α -olefin.

The PBE may comprise at least about 5wt%, at least about 6wt%, at least about 7wt%, at least about 8wt%, at least about 9wt%, at least about 10wt%, at least about 12wt%, or at least about 15wt% of alpha-olefin derived units, wherein the weight percentages are based on the total weight of the propylene derived units and alpha-olefin derived units. The PBE may comprise up to about 30wt%, up to about 25wt%, up to about 22wt%, up to about 20wt%, up to about 19wt%, up to about 18wt%, or up to about 17wt% of alpha-olefin derived units, wherein the weight percentages are based on the total weight of the propylene derived units and alpha-olefin derived units. In some embodiments, the PBE may contain from about 5wt% to about 30wt%, from about 6wt% to about 25wt%, from about 7wt% to about 20wt%, from about 10wt% to about 19wt%, from about 12wt% to about 18wt%, or from about 15wt% to about 17wt% of the alpha-olefin derived units, wherein the weight percentages are based on the total weight of the propylene derived units and alpha-olefin derived units.

The PBE may comprise at least about 70wt%, at least about 75wt%, at least about 78wt%, at least about 80wt%, at least about 81wt%, at least about 82wt%, or at least about 83wt% propylene-derived units, wherein the weight percentages are based on the total weight of the propylene-derived units and alpha-olefin-derived units. The PBE may comprise up to about 95wt%, up to about 94wt%, up to about 93wt%, up to about 92wt%, up to about 91wt%, up to about 90wt%, up to about 88wt%, or up to about 85wt% propylene-derived units, wherein the weight percentages are based on the total weight of the propylene-derived units and alpha-olefin-derived units.

The PBE may be characterized by a melting point (Tm) that may be determined by Differential Scanning Calorimetry (DSC). For purposes of this disclosure, the maximum of the highest temperature peak is considered the melting point of the polymer. The "peak" is defined herein as the general slope of the DSC curve (heat flow versus temperature curve) changing from positive to negative, forming a maximum, while the baseline of the DSC curve is drawn without an offset, so the endothermic reaction will be shown as a positive peak. The Tm of the PBE (as determined by DSC) may be below 120 ℃, below 115 ℃, below 110 ℃ or below 105 ℃.

The PBE can be characterized by its heat of fusion (Hf) as determined by DSC. The PBE can have a Hf of at least about 0.5J/g, at least about 1.0J/g, at least about 1.5J/g, at least about 3.0J/g, at least about 4.0J/g, at least about 5.0J/g, at least about 6.0J/g, or at least about 7.0J/g. The PBE may be characterized by a Hf of less than 75J/g, or less than 70J/g, or less than 60J/g, or less than 50J/g. In one or more examples, the PBE has a melting temperature of less than 120 ℃ and a heat of fusion of less than 75J/g.

The PBE may have a triad tacticity (mm tacticity) of three propylene units of 75% or greater, 80% or greater, 85% or greater, 90% or greater, 92% or greater, 95% or greater, or 97% or greater, as determined by 13C Nuclear Magnetic Resonance (NMR). For example, the triad tacticity may be in the range of about 75% to about 99%, about 80% to about 99%, about 85% to about 99%, about 90% to about 97%, or about 80% to about 97%. Triad tacticity may be determined by the method described in U.S. patent No. 7,232,871.

The PBE may have a tacticity index m/r ranging from a lower limit of 4 or 6 to an upper limit of 8 or 10 or 12. The tacticity index, denoted "m/r" herein, was determined by 13C NMR. The tacticity index m/r is calculated as defined in H.N.Cheng, vol.17, MACROMLECULES, pp.1950-1955 (1984), incorporated herein by reference. The designation "m" or "r" describes the stereochemistry of adjacent propylene pairs, where "m" refers to meso and "r" refers to racemic. An m/r ratio of 1.0 generally describes syndiotactic polymers and an m/r ratio of 2.0 describes atactic materials.

The PBE may have a percent crystallinity of from about 0.5% to about 40%, from about 1% to about 30%, or from about 5% to about 25%, as determined by DSC procedure. The crystallinity can be determined by dividing the Hf of the sample by the Hf of the 100% crystalline polymer, assuming that the Hf of the isotactic polypropylene is 189J/g.

The PBE may have a g/cm of about 0.84g/cm at room temperature (about 23 ℃) ³ To about 0.92g/cm ³ About 0.85g/cm ³ To about 0.90g/cm ³ Or about 0.85g/cm ³ To about 0.87g/cm ³ Is measured according to ASTM D-1505 test method.

The PBE can have a Melt Index (MI) of less than or equal to about 100dg/min, less than or equal to about 555dg/min, less than or equal to about 25dg/min, less than or equal to about 10dg/min, less than or equal to about 8.0dg/min, less than or equal to about 5.0dg/min, or less than or equal to about 3.0dg/min, as determined according to ASTM D-1238 (2.16 kg, at 190 ℃).

The PBE may have an MFR of greater than 0.5dg/min, greater than 1.0dg/min, greater than 1.5dg/min, greater than 2.0dg/min, or greater than 2.5dg/min, as determined in accordance with ASTM D-1238 (2.16 kg load, at 230 ℃). The PBE may have an MFR of less than 100dg/min, less than 55dg/min, less than 25dg/min, less than 15dg/min, less than 10dg/min, less than 7dg/min, or less than 5 dg/min. In some embodiments, the PBE can have an MFR in the range of about 0.5 to about 10dg/min, about 1.0 to about 7dg/min, or about 1.5 to about 5 dg/min.

The PBE may have a g 'index value of 0.95 or greater, or at least 0.97, or at least 0.99, where g' is measured at the weight average molecular weight (Mw) of the polymer using the intrinsic viscosity of the isotactic polypropylene as a baseline. For use herein, the g' index is defined as: g' =ηb/η1, where ηb is the intrinsic viscosity of the polymer and η1 is the intrinsic viscosity of a linear polymer having the same viscosity average molecular weight (Mv) as the polymer. η1= KMv α, where K and α are measurements of linear polymers and should be obtained on the same instrument as that used for g' index measurement.

The PBE can have a Mw of about 50,000 to about 1,000,000g/mol, or about 75,000 to about 500,000g/mol, about 100,000 to about 350,000g/mol, about 125,000 to about 300,000g/mol, about 150,000 to about 275,000g/mol, or about 200,000 to about 250,000g/mol, as measured by DRI.

The PBE can have a Mn of about 5,000 to about 500,000g/mol, about 10,000 to about 300,000g/mol, about 50,000 to about 250,000g/mol, about 75,000 to about 200,000g/mol, or about 100,000 to about 150,000g/mol, as measured by DRI.

The PBE can have a z-average molecular weight (Mz) of about 50,000 to about 1,000,000g/mol, or about 75,000 to about 500,000g/mol, or about 100,000 to about 400,000g/mol, about 200,000 to about 375,000g/mol, or about 250,000 to about 350,000g/mol, as measured by MALLS.

The MWD of the PBE may range from about 0.5 to about 20, from about 0.75 to about 10, from about 1.0 to about 5, from about 1.5 to about 4, or from about 1.8 to about 3.

Optionally, the PBE may further comprise one or more dienes. The term "diene" is defined as a hydrocarbon compound having two sites of unsaturation, for example, a compound having two double bonds linking carbon atoms. The term "diene" as used herein broadly refers to either a diene monomer prior to polymerization (e.g., forming part of the polymerization medium), or a diene monomer after initiation of polymerization (also referred to as a diene monomer unit or diene-derived unit), depending on the context. In some embodiments, the diene may be selected from 5-ethylidene-2-norbornene (ENB); 1, 4-hexadiene; 5-methylene-2-norbornene (MNB); 1, 6-octadiene; 5-methyl-1, 4-hexadiene; 3, 7-dimethyl-1, 6-octadiene; 1, 3-cyclopentadiene; 1, 4-cyclohexadiene; vinyl Norbornene (VNB); dicyclopentadiene (DCPD) and combinations thereof. In embodiments wherein the PBE composition contains a diene, the diene may be present at a level of from 0.05wt% to about 6wt%, from about 0.1wt% to about 5.0wt%, from about 0.25wt% to about 3.0wt%, from about 0.5wt% to about 1.5wt% diene-derived units, wherein the weight percentages are based on the total weight of propylene-derived units, alpha-olefin derived units, and diene-derived units.

Optionally, the PBE may be grafted (e.g., "functionalized") using one or more grafting monomers. The term "grafted" as used herein means that the grafted monomer is covalently bonded to the polymer chain of the PBE. The grafting monomer may be or include at least one ethylenically unsaturated carboxylic acid or acid derivative, such as an anhydride, ester, salt, amide, imide, or acrylate. Exemplary grafting monomers include, but are not limited to, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, maleic anhydride, 4-methylcyclohexene-1, 2-dicarboxylic anhydride, bicyclo (2.2.2) octene-2, 3-dicarboxylic anhydride, 1,2,3,4,5,8,9,10-octahydronaphthalene-2, 3-dicarboxylic anhydride, 2-oxa-l, 3-diketopiro (4.4) nonene, bicyclo (2.2.1) heptene-2, 3-dicarboxylic anhydride, maleopimaric acid, tetrahydrophthalic anhydride, norbornene-2, 3-dicarboxylic anhydride, 4-norbornene-1, 2-dicarboxylic anhydride (nadic anhydride), methylnadic anhydride, bicycloheptene dicarboxylic anhydride, methylbicycloheptene dicarboxylic anhydride, and 5-methylbicyclo (2.2.1) heptene-2, 3-dicarboxylic anhydride. Other suitable grafting monomers include methyl and higher alkyl acrylates, methyl and higher alkyl methacrylates, acrylic acid, methacrylic acid, hydroxymethyl methacrylate, hydroxyethyl methacrylate and higher hydroxyalkyl methacrylates, and glycidyl methacrylate. Maleic anhydride is a grafting monomer. In some embodiments, the grafting monomer may be or include maleic anhydride, and the maleic anhydride concentration in the grafted polymer is in the range of about 1 wt% to about 6 wt%, for example at least about 0.5 wt%, or at least about 1.5wt%.

In some embodiments, the PBE is a reactor blended polymer as defined herein. That is, the PBE is a reactor blend of a first polymer component and a second polymer component. Thus, the comonomer content of the PBE can be adjusted by adjusting the comonomer content of the first polymer component, adjusting the comonomer content of the second polymer component and/or adjusting the ratio of the first polymer component to the second polymer component present in the PBE.

In embodiments wherein the PBE is a reactor blended polymer, the alpha-olefin content of the first polymer component may be greater than 5wt% alpha-olefin, greater than 7wt% alpha-olefin, greater than 10wt% alpha-olefin, greater than 12wt% alpha-olefin, greater than 15wt% alpha-olefin, or greater than 17wt% alpha-olefin, wherein the weight percentages are based on the total weight of propylene-derived units and alpha-olefin-derived units of the first polymer component. The alpha-olefin content of the first polymer component may be less than 30wt% alpha-olefin, less than 27wt% alpha-olefin, less than 25wt% alpha-olefin, less than 22wt% alpha-olefin, less than 20wt% alpha-olefin, or less than 19wt% alpha-olefin, wherein the weight percentages are based on the total weight of propylene-derived units and alpha-olefin derived units of the first polymer component. In some embodiments, the alpha-olefin content of the first polymer component can be in the range of 5wt% to 30wt% alpha-olefin, 7wt% to 27wt% alpha-olefin, 10wt% to 25wt% alpha-olefin, 12wt% to 22wt% alpha-olefin, 15wt% to 20wt% alpha-olefin, or 17wt% to 19wt% alpha-olefin. In some examples, the first polymer component contains or comprises propylene and ethylene, and in some embodiments the first polymer component consists only of propylene and ethylene derived units.

In embodiments wherein the PBE is a reactor blended polymer, the alpha-olefin content of the second polymer component may be greater than 1.0wt% alpha-olefin, greater than 1.5wt% alpha-olefin, greater than 2.0wt% alpha-olefin, greater than 2.5wt% alpha-olefin, greater than 2.75wt% alpha-olefin, or greater than 3.0wt% alpha-olefin, wherein the weight percentages are based on the total weight of propylene-derived units and alpha-olefin derived units of the second polymer component. The alpha-olefin content of the second polymer component may be less than 10wt% alpha-olefin, less than 9wt% alpha-olefin, less than 8wt% alpha-olefin, less than 7wt% alpha-olefin, less than 6wt% alpha-olefin, or less than 5wt% alpha-olefin, wherein the weight percentages are based on the total weight of propylene-derived units and alpha-olefin derived units of the second polymer component. In some embodiments, the alpha-olefin content of the second polymer component may be in the range of 1.0wt% to 10wt% alpha-olefin, or 1.5wt% to 9wt% alpha-olefin, or 2.0wt% to 8wt% alpha-olefin, or 2.5wt% to 7wt% alpha-olefin, or 2.75wt% to 6wt% alpha-olefin, or 3wt% to 5wt% alpha-olefin. In some examples, the second polymer component contains propylene and ethylene, and in some embodiments the first polymer component consists only of propylene and ethylene derived units.

In certain embodiments, the PBE contains propylene derived units and about 5wt% to about 30wt% alpha-olefin derived units and has a melting temperature of less than 120 ℃ and a heat of fusion of less than 75J/g.

In certain embodiments, the PBE contains propylene-derived units and from about 10wt% to about 30wt% of one or more alpha-olefin-derived units, and has an MFR of at least 40dg/min and a heat of fusion (Hf) of from about 3J/g to about 75J/g, as determined by DSC.

In embodiments where the PBE is a reactor blended polymer, the PBE may contain 1wt% to 25wt% of the second polymer component, 3wt% to 20wt% of the second polymer component, 5wt% to 18wt% of the second polymer component, 7wt% to 15wt% of the second polymer component, or 8wt% to 12wt% of the second polymer component, based on the weight of the PBE. The PBE may contain 75 to 99wt% of the first polymer component, 80 to 97wt% of the first polymer component, 85 to 93wt% of the first polymer component, or 82 to 92wt% of the first polymer component, based on the weight of the PBE.

In one or more embodiments, the PBE contains a reactor blend of a first polymer component and a second polymer component. The first polymer component contains propylene and an alpha-olefin and has an alpha-olefin content of greater than 5wt% to less than 30wt%, based on the total weight of propylene-derived units and alpha-olefin-derived units of the first polymer component. The second polymer component contains propylene and an alpha-olefin and has an alpha-olefin content of greater than 1wt% to less than 10wt%, based on the total weight of propylene-derived units and alpha-olefin-derived units of the second polymer component. In one or more examples, the first polymer component has an alpha-olefin content of from about 10wt% to about 25wt%, based on the total weight of propylene-derived units and alpha-olefin-derived units of the first polymer component. The second polymer component has an alpha-olefin content of from greater than 2wt% to less than 8wt%, based on the total weight of propylene-derived units and alpha-olefin derived units of the second polymer component. In other examples, the PBE contains from about 1wt% to about 25wt% of the second polymer component and from about 75wt% to about 99wt% of the first polymer component, based on the weight of the PBE.

The PBE may be prepared by any suitable method known in the art. The PBE may be prepared using homogeneous conditions, such as a continuous solution polymerization process using a metallocene catalyst. In some embodiments, the PBE is produced in parallel solution polymerization reactors such that a first reactor component is produced in a first reactor and a second reactor component is produced in a second reactor, and the reactor effluents from the first and second reactors are combined and blended to form a single effluent from which the final PBE is separated. Exemplary methods for preparing PBE can be found in U.S. patent nos. 6,881,800;7,803,876;8,013,069; and 8,026,323 and PCT publication No. WO2011/087729; WO2011/087730; and WO 2011/087731.

As used herein, a "nonwoven" (or "fabric" as used herein) is a textile structure (e.g., sheet, web, or batt) of oriented or randomly oriented fibers, without first making yarns. The fabrics described herein comprise a network of fibers or continuous filament yarns reinforced by mechanical, chemical or thermal interlocking processes. "multilayer fabric" includes at least two fabric layers; "layer" as used herein refers to a fabric. "fiber" is a material having a length that is substantially greater than its diameter or width; average diameters are on the order of 0.01 to 200 μm and include natural and/or synthetic materials.

As used herein, "bonded" (or "bonded" bond or "adhesion") means that two or more fabrics or multiple fibers are secured to one another by: (i) The inherent tendency of molten or non-molten materials to adhere through chemical interactions and/or (i i) the ability of molten or non-molten fibers and/or fabrics to entangle with fibers comprising another material to create a bond between the fibers or fabrics. Adhesives may be used to promote adhesion of the fabric layers, but in certain embodiments the adhesive is not present in the fabric layers described herein (not used to adhere the fibers of the fabric); and in another embodiment is not present in the multilayer fabrics described herein (not used to bond adjacent fabric layers). Examples of binders include those comprising low weight average molecular weight (< 80,000 g/mole) polyolefins, polyvinyl acetates, polyamides, hydrocarbon resins, natural asphalts, styrenic rubbers, and blends thereof.

A "spunbond" fabric is a sheet of filaments made by a spunbond integration process that includes the steps of spinning molten polymer, air-attenuating, depositing (on a drum or other moving substrate to form a web, or depositing on another fabric), and bonding. Spunbond processes are well known and are generally described, for example, in POLYPROPYLENE HANDBOOK 314-324 (E.Moore, hanser Ver lag, 1996). The average diameter of such fibers is in the range of 5 to 150 microns in certain embodiments, and in particular embodiments in the range of 10 to 40 or 50 or 100 microns. In particular embodiments, the combination of thickness, fiber fineness (denier) and number of fibers per unit area determines a fabric basis weight of 8 or 10 or 15 to 50 or 80 or 120 or 400 or 800g/m ² Within a range of (2). Most spunbond processes produce fabrics with planar isotropic properties due to random placement of the fibers. Spunbond fabrics are generally non-directional and may be cut and used without fear of higher stretch in the oblique direction or unraveling at the edges. By controlling the orientation of the fibers in the web during the laying process, non-isotropic properties can be created. The fabric thickness varies from 0.1 to 4.0mm and in particular embodiments ranges from 0.15 to 1.5 mm. The bonding method can affect the thickness of the sheet as well as other properties. In certain embodiments, no adhesive is present as a binding agent; thermal bonding is preferred. The web bonded by hot calendering is thinner than the web through needling because the calendering operation passes through a pressure compression structure while the needling operation moves the fibers from the x-y plane of the fabric to the z (thickness) direction.

One field of application for nonwovens is the hygiene field. Articles include, for example, diapers, adult incontinence pads, and feminine hygiene products. Nonwoven fabrics are used in various components of these articles such as topsheets, backsheets, acquisition distribution layers, binder and leg cuffs. For such articles, the quality of softness is important, although not well-defined. The nonwoven with improved caliper or bulk enhances the softness perception of the individual wearing the article or those who may be directly handling the article.

Examples

The embodiments discussed and described herein may be further described with the following examples. Although the following examples are directed to particular implementations, they should not be construed as limiting in any particular respect.

According to one or more embodiments provided above, two (2) multicomponent fibers are prepared from a first fiber component and a second fiber component. Two additional (2) comparative examples are provided to better show the surprising and significant differences produced by the addition of PBE and the MFR differences between the polymers on the fiber side. Table 1 summarizes the physical properties of the first fiber component and table 2 summarizes the physical properties of the second fiber component. Table 3 summarizes the fiber components produced and tested.

Table 1: first fiber component

Table 2: second fiber component

		PP1	PBE
				MWD		3.0	2.5
Mw	g/mol	180,000	119,000
				Mn	g/mol	55,000	45,000
Mz	g/mol	380,000	191,000
				MFR	dg/min	36	48
Tm	℃	159	60.5
				Tc	℃	110
Heat of fusion (Hf)	J/g	101	18.6
				Three unit group tacticity	％	0.96

Table 3: fiber component

With respect to comparative example 22, the first fiber component included 500ppm erucamide slip agent. The slip agent was added as a masterbatch SCC-88953 (from Standridge Color Corporation, which has about 10% active erucamide component in the polypropylene-based base resin). With respect to example 2, the first fiber component included 1000ppm of the erucamide slip agent, added via the SCC-88953 masterbatch.

Table 4: fabric characteristics

TABLE 5 melt analysis of various formulations

Crystallization by SAOS rheology

Referring to Table 5, crystallization was monitored by SAOS rheology, wherein samples were cooled down from the molten state (at 190 ℃) at a fixed cooling rate using a 25mm parallel plate configuration on an ARES 2001 (TA instruments) controlled strain rheometer. Sample test discs (25 mm diameter, 2.5 mm thickness) were prepared using a Carver laboratory press at 190 ℃. The sample was left to stand without pressure for about 3 minutes for melting, and then held under pressure for 3 minutes to compression mold the sample. The disc has an initial thickness of about 2.5 mm; however, after trimming the sample from the parallel plates, the gap between the plates was 1.9mm. The thermal expansion of the tool during the SAOS test is taken into account to maintain a constant gap throughout the test. The sample was first heated from room temperature to 190 ℃. The samples were equilibrated at 190 ℃ (molten state) for 15 minutes to eliminate any previous heat and crystallization history. The temperature is reproducibly controlled within + -0.5deg.C. The sample was then cooled from 190℃at a constant cooling rate of 1℃per minute and an angular frequency of 1rad/s, with a strain of 1%, maintained in the linear viscoelastic region. To terminate the experiment, a maximum torque criterion was used. At the start of crystallization during the rheological test, the instrument enters an overload condition when maximum torque is reached and the test automatically stops. All experiments were performed under a nitrogen atmosphere to minimize any degradation of the samples during the rheology test. Crystallization is observed by a sharp/abrupt increase in complex viscosity and a sharp/abrupt (stepped) decrease in loss tangent (tan delta) (i.e., a complex viscosity versus temperature plot and a loss tangent versus temperature plot depict bottleneck-like regions of abrupt changes in rheological properties due to the occurrence of crystallization). "initial crystallization temperature by rheology" Tc _{Rheology of} Is defined as the temperature at which a sharp increase in complex viscosity (i.e., bottleneck) and a simultaneous sharp decrease in tan delta are observed. Tc (Tc) _{Rheology of} The reproducibility of (C) is within + -1 ℃.

Differential Scanning Calorimetry (DSC)

The peak crystallization temperature (Tc), peak melting temperature (Tm) and heat of fusion (Hf) were measured by DSC procedures on particle samples using a DSC Q200 (TA Instruments) device. The temperature of the DSC was calibrated using four standards (tin, indium, cyclohexane and water). The heat flow of indium (28.46J/g) was used to calibrate the heat flow signal. Samples of 3 to 5 milligrams of polymer (typically in particulate form) were sealed in standard aluminum trays with flat covers and loaded into the instrument at room temperature. In the case where Tm corresponding to a cooling and heating rate of 10 ℃/min was determined, the following procedure was used. The sample was first equilibrated at 25 ℃ and then heated to 200 ℃ (first heating) using a heating rate of 10 ℃/min. The sample was kept at 200 ℃ for 5 minutes to eliminate any previous heat and crystallization history. The sample was then cooled to 25 c (first cooling) at a constant cooling rate of 10 c/min. The exothermic peak of crystallization (first cooling) was determined by analysis using TA Universal Analysis software. The sample was held isothermally at 25 ℃ for 10 minutes and then heated to 200 ℃ (second heating) at a constant heating rate of 10 ℃/minute. Melting endotherm peaks (second heat) were also analyzed using the TA Universal Analysis software and Tm and Hf values were determined.

Using option A of WSP 120.6 (05), the Z-direction thickness was measured at 0.5kPa with a contact time of 5 seconds and recorded as an average of 3 samples. The contact thickness measurement is made within one hour after fabric manufacture.

Tensile properties of the nonwoven fabric, such as tensile (peak) strength and percent (peak) elongation in the Machine Direction (MD) and cross-machine direction (CD), were measured according to standard method WSP 110.4 (05), with a calculated sample length of 200mm and a test speed of 100mm/min, unless otherwise indicated. The width of the fabric swatch was 5cm. For tensile testing, an Instron machine (model 5565) equipped with Ins tron Bluehill 2 (version 2.5) software for data analysis was used.

As known in the art, softness or "feel" is measured using a Thwing-Albert Instruments Co. Handle-O-Meter (Model 211-10-B/AERGLA). The quality of the "hand" is considered to be a combination of resistance due to surface friction and flexibility of the fabric material. Handle-O-Meter uses LVDT (Linear variable differential Transformer (Linear Variable Differential Transformer)) to measure both factors to detect the resistance that a blade encounters when pressing a sample of material into a parallel edge slitForce. 3 ¹ / ₂ Digital Voltage Meter (DVM) directly expresses the resistance in grams force. The "overall hand" of a given fabric is defined as the average of 8 readings taken on two fabric samples (4 readings per sample). For each sample (5 mm seam width), the hand is measured on both sides and in both directions (MD and CD) and recorded in grams. A decrease in "overall hand" indicates an improvement in fabric softness.

Thickness, compressibility and elasticity

Bulky nonwovens, such as those disclosed herein, can be distinguished from conventional nonwovens in terms of "bulk," which can be characterized as 1) the z-direction thickness of the fabric and 2) how the fabric responds to compression. There is no standard test method to measure "bulk". Currently, the Handle-O-Meter and contact thickness discussed above are used to characterize a lofty nonwoven.

US patent No. 9826877 discloses a test method for measuring compression and recovery of make-up removal wipes (nonwoven materials saturated with emulsion). Compressibility was determined using AMES Gage by measuring the thickness of the wet wipes as they were compressed by the increasing presser foot weighing from 0.5 ounces to 7.0 ounces. Recovery of the wet wipes was measured by re-measuring the thickness of the wet wipe at the lowest initial weight (0.5 ounces) after the compressibility test was completed and comparing the thickness value to the first pre-compression measurement at 0.5 ounces. A second lower 0.5 ounce measurement thickness as compared to the first 0.5 ounce measurement indicates less elasticity.

To characterize a lofty nonwoven, the present inventors developed a test method to measure z-direction thickness, compressibility, and elasticity. Samples of materials such as nonwoven fabrics were evaluated using a dynamic rotarheometer. For the example measurements herein, ARES-G2 from TA Instruments was used. Such rheometers are commonly used to evaluate the properties of molten materials; however, for this method, various natural and synthetic materials such as cotton, paper and nonwoven fabrics can be evaluated.

A schematic cross-sectional view of a parallel plate rheometer test set up 300 is shown in fig. 3. Test sample 302 was prepared by cutting a disc of material having a diameter of about 30 mm. The test sample 302 is then placed between the lower parallel plate 304 and the upper parallel plate 306. The rheometer then compresses the sample 302 in a direction 308 perpendicular to the surface of the sample 302 at a constant rate of 0.05 mm/s. The compression rate may be selected to suit the test sample material. In some embodiments of the test method, the compression rate may be varied rather than constant, for example, the compression rate may decrease as compression increases. As the distance between the plates, i.e., gap 310, decreases, the force 308 exerted by the sample on the plates perpendicular to the surface of the nonwoven (i.e., the "z direction") is measured by the rheometer, producing a normal force (N) versus gap (mm) curve.

Fig. 4 shows the normal force versus gap curves for several standard materials, including cotton, paper and ultra-soft nonwovens, as well as the curves for control sample comparative example 11 and comparative example 22 and inventive samples example 1 and example 2. The cotton standard is a natural material with high bulk. The paper standard is a material that has no bulk. Cotton and paper standards were chosen for the figures to illustrate the two extremes of very high bulk (cotton) and no bulk (paper). The ultra-soft standard is a nonwoven material that has been optimized for surface softness rather than bulk; it is a nonwoven material of three-layer spunbond monocomponent fibers made from a blend of 85wt% PP3155, 15wt% Vistamaxx 7020BF (all available from ExxonMobil Chemical Company) and 4000ppm erucamide slip agent. Softness was characterized using a Handle-o-meter and a measured coefficient of friction. Although softness preferences vary from manufacturer to manufacturer and from geographic location to geographic location, the ultra-soft standards used herein represent solutions accepted by different brand owners worldwide for their premium product lines. Many nonwoven applications seek high bulk and softness, but achieving both at the same time has been a challenge. Fibers that achieve high levels of softness typically have low modulus, which improves drape (Handle-o-meter); such low modulus makes it difficult to achieve and maintain high bulk for fabrics based on such fibers. According to the Euler-Bernoulli beam theory, fibers with lower modulus will bend at lower loads; thus, in the case of lower modulus fibers, the three-dimensional structure may collapse at very low pressures, and in some cases even under gravitational fields.

The normal force versus gap curve generated by this method can be further evaluated to characterize fluffy materials. The gap distance (z-direction thickness) values can be compared under a constant normal force to evaluate the comparative compressibility of the different samples. A greater thickness indicates a higher degree of bulk. The nonwoven of the present invention may have a thickness of 0.35 millimeters or greater, 0.38 millimeters or greater, 0.40 millimeters or greater, or 0.44 millimeters or greater under a load of 0.5N. The nonwoven of the present invention may have a thickness of 0.30 millimeters or more, 0.35 millimeters or more, or 0.38 millimeters or more under a 1N load.

The area under the curve represents the work of compression, i.e. the total work required to compress the sample to a given thickness. The higher the compression work, the higher the bulk. The nonwoven of the present invention may have a work of compression of 10.5E-4J or greater, 11.0E-4J or greater, 12.0E-4J or greater, or 13.0E-4J or greater.

The slope of the curve at a given load represents the stiffness of the material. The stiffness measured in N/m is similar to the spring constant in hooke's law and reflects the compressibility of the material. Lower stiffness values indicate that at a given load, the sample gap distance decreases more with increasing normal force than a harder material, which requires a higher load to decrease the gap distance. That is, lower stiffness indicates a more fluffy sample. The nonwoven of the present invention may have a 1N stiffness of less than 13N/m, less than 12N/m, or less than 11N/m.

Elasticity is an indication of the retained thickness (or "bulk") of a material after long-term compression (which simulates what happens when a fabric is rolled). To measure the elasticity of the sample, the fabric sample is subjected to a static load for a longer period of time and thickness (gap distance) measurements are collected by a plate-configured rheometer before and after the load is applied. To evaluate the bulk of the nonwoven, a load of 4kg and a 24 hour test interval may be used. The load and test time may be selected to suit the sample material. As outlined in equations 1 and 2, elasticity is defined as the difference between the thickness (gap distance) measurement and the initial thickness (gap distance). The thickness remains the complement of elasticity.

T _R ＝1-R (2)

Wherein:

r is elasticity

·T _R Is thickness retention

·t ₀ Is of initial thickness

·t _l Is the thickness after compression

Table 6 shows the thickness, compression work and stiffness of inventive fabrics, examples 1 and 2, as compared to various standards and comparative examples, comparative examples 11 and 22, measured using the test methods taught herein.

Table 6: thickness and compressibility of various materials

Inventive samples examples 1 and 2 have a thickness at 0.5N and 1N that is between the thickness of the paper standard (low bulk) and the cotton standard (high bulk) and show significantly improved levels of bulk over the bulk of the ultra-soft nonwoven standard.

High bulk cotton standards require 13.9E-4J work to compress the sample. The samples of the present invention required a similar amount of work to compress—example 1 required 13.9E-4J and example 2 required 11.6E-4J. The comparative sample required a lower level of work to compress—comparative example 11 required 10.4E-4J and comparative example 22 required 9.05E-4J. The ultra-soft nonwoven standard requires significantly less work to compress-5.05E-4J, less than half the work required for the inventive sample. The observed compression work of the inventive examples over the comparative examples is due to the presence of PBE.

The difference in compression properties can also be observed in fig. 3. The curves of the cotton standard and inventive examples 1 and 2 have a more gradual transition from the lower stiffness region at higher gap distances to the higher stiffness region at smaller gap distances compared to papers showing a more abrupt transition from lower stiffness at high gap distances to higher stiffness at low gap distances, the soft lean blend (ultra soft standard) and comparative examples 11 and 22.

All fabric tests described above were performed at least 20 days after the day of fabric manufacture, unless otherwise indicated, to ensure a balance of properties and to take into account any effects that may change fabric properties over time.

Spun-bonded nonwoven fabric

The spunbonded nonwoven was produced on a 1.1 meter wide single beam Reicofil 4 (R4) line with 6800 hole spinneret with a hole (die) diameter of 0.6 mm. For a detailed description of the Reicofil spunbond process, see EP 1340843 or U.S. Pat. No. 6,918,750. As noted, the production rate per well is variable. The quench air temperature for all experiments was 18 ℃. Under these conditions, fibers of 1 to 1.4 denier, corresponding to fiber diameters of 12 to 15 microns, were produced. For all examples, the line speed was varied as required to obtain 25g/m ² (gsm) nonwoven of target fabric basis weight.

The formed fabric is thermally bonded by compression through a set of two heated rolls (calenders) to improve fabric integrity and improve fabric mechanical properties. The basic principle of the thermal bonding process of fabrics can be found in the review article "Review of Thermally Point-bonded works: materials, processes, and Properties" 99J.APPLIED POLYM.SCI.2489-2496 (2005) by michelson et al or in the article "Thermal Bonding of Polypropylene Nonwovens: effect of Bonding Variables on the Structure and Properties of the Fabrics,"92J.APPLIED POLYM.SCI, 3593-3600 (2004) by Bhat et al. The two rolls are referred to as the "embossing" (E) roll and the "smoothing" (S) roll. The set temperatures of the two calenders are listed in table 4, corresponding to the set oil temperatures of the heating medium used as the rolls. The calender temperature was measured on both the embossing roll and the S-roll using a contact thermocouple and was typically found to be 10-20 ℃ lower than the set oil temperature. The spinnability of the composition of the invention was evaluated as excellent under the described conditions.

The various polymer melt properties of the neat polymer and polymer blend compositions comparable to the fiber compositions used in fabric production are reported in table 5 above. Without being limited by theory, it is believed that polymer melt crystallization behavior is a factor in fiber formation. The difference in crystallization temperatures of the various fiber components contributes in part to the generation of crimp in the fibers. The crystallization temperature under shear was measured (Tc, _{rheology of} ) Is an approximation of the difference in fiber structure (i.e., curl) found in the setting behavior of polymer compositions and fibers of bicomponent or multicomponent geometry. In addition to the data set forth in table 5, fig. 1 depicts a graphical representation of complex viscosity (Pa x s) versus temperature (°c) for fiber compositions based on PP1, PP2, and PBE at various blend ratios. Similarly, FIG. 2 depicts a graphical representation of Tanδ versus temperature (. Degree.C.) for compositions based on PP1, PP2 and PBE in various blend ratios. Tc (Tc) _{Rheology of} It is presumed that addition of PBE to PP1 complex leads to Tc, determined as described above _{Rheology of} Is reduced. Alternatively, the addition of PP2 to PP1 results in Tc _{Rheology of} Maintaining or increasing Tc over PP1, _{rheology of} Values. Moreover, the samples including PBE of examples 1 and 2 had greater contact thicknesses (0.55 and 0.53 mm, respectively) than those of comparative examples 11 and 22 (0.48 and 0.43 mm, respectively) including no PBE. The thickness improvement observed when PBE is added to the fiber composition is a function of the difference created between the first and second fiber components.

List of embodiments

The present disclosure may further include any one or more of the following non-limiting embodiments:

1. a multicomponent fiber for a nonwoven comprising a first fiber component comprising a first polypropylene having an MFR of at least 30dg/min and a second polypropylene having an MFR of less than 20dg/min and a second fiber component comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and from about 10wt% to about 30wt% of one or more alpha olefin derived units based on the total weight of the elastomer, wherein the propylene-based elastomer has an MFR of at least 40dg/min and a heat of fusion (Hf) of from about 3J/g to about 75J/g as determined by DSC.

2. The fiber of embodiment 1, wherein the first polypropylene has an MFR of from 30dg/min to about 40 dg/min.

3. The fiber of embodiment 1 or 2, wherein the first polypropylene has a melting temperature (Tm) of at least 140 ℃.

4. The fiber of embodiments 1-3, wherein the second polypropylene has a melting temperature (Tm) of at least 140 ℃.

5. The fiber of embodiments 1-4, wherein the second polypropylene has an MFR of from 10dg/min to about 20 dg/min.

6. The fiber of embodiments 1-5, wherein the MFR of the second polypropylene is less than half the MFR of the first polypropylene.

7. The fiber of embodiments 1-6 wherein the MFR of the second polypropylene is 15% -40% of the MFR of the first polypropylene.

8. The fiber of embodiments 1-7, wherein the at least one propylene-based elastomer has an MFR of from 30dg/min to about 60 dg/min.

9. The fiber of embodiments 1-8, wherein the one or more alpha olefin derived units consist essentially of ethylene.

10. The fiber of embodiments 1-9, wherein the one or more alpha olefin derived units consist of ethylene.

11. The fiber of embodiments 1-10, wherein the at least one propylene-based elastomer has a tacticity index (m/r) of 4-12.

12. The fiber of embodiments 1-11, wherein the at least one propylene-based elastomer has about 0.84g/cm ³ -about 0.92g/cm ³ Is a density of (3).

13. The fiber of embodiments 1-12, wherein the at least one propylene-based elastomer has a percent crystallinity of from about 1% to about 40%.

14. The fiber of embodiments 1-13 wherein the ratio of the first polypropylene to the second polypropylene in the first fiber component is in the range of 20/80 to 80/20.

15. The fiber of embodiments 1-14 wherein the ratio of the first polypropylene to the propylene-based elastomer in the second fiber component is in the range of 5/955/95 to 95/595/5.

16. The fiber of embodiments 1-15 wherein the first polypropylene is a propylene homopolymer.

17. The fiber of embodiments 1-16 wherein the second polypropylene is a propylene homopolymer.

18. A method of making a fiber for a fabric having a suitable thickness and softness, the method comprising: forming a first polymer composition comprising a first polypropylene having an MFR of at least 30dg/min and a second polypropylene having an MFR of less than 20 dg/min; forming a second polymer composition comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and from about 10 to about 30 weight percent, based on the total weight of the elastomer, of one or more alpha-olefin derived units and having an MFR of at least 40dg/min and a heat of fusion (Hf) of from about 3J/g to about 75J/g, as determined by DSC; forming a plurality of fibers from the first polymer composition and the second polymer composition in a side-by-side configuration; and forming a fabric from the plurality of fibers, wherein the fabric has a thickness of at least 0.40mm, a total hand of less than 20g, and MD and CD tensile strengths of at least 8N/5 cm.

19. The method of embodiment 18, wherein the step of forming the fibers comprises spunbond the first polymer composition and the second polymer composition to form side-by-side fibers.

20. The method of embodiment 18 or 19, further comprising directing the fibers to a spinning belt, laying the fibers on the spinning belt and forming a fabric from the fibers.

21. The method of embodiments 18-20, wherein the ratio of the first polypropylene to the second polypropylene in the first polymer composition is in the range of 20/80-80/20 and the ratio of the first polypropylene to the propylene-based elastomer in the second polymer composition is in the range of 5/95-95/5.

22. A hygiene product comprising the fibers of embodiments 1-17.

Specific embodiments of the present disclosure have been described above in connection with various preferred embodiments. However, to the extent that the foregoing description is specific to a particular embodiment or a particular use of the present disclosure, this is intended to be illustrative only and provides a concise description of the exemplary embodiments. Accordingly, the present disclosure is not limited to the particular embodiments described above, but, on the contrary, the present disclosure includes all alternatives, modifications, and equivalents falling within the true scope of the appended claims. Various modifications and variations of the present disclosure will be apparent to those skilled in the art and it is intended that such modifications and variations be included within the scope of the present application and the spirit and scope of the appended claims.

All patents and patent applications, test methods (e.g., ASTM methods, UL methods, etc.), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It is to be understood that a range including any two values, such as any lower value in combination with any upper value, any combination of any two lower values, and/or any combination of any two upper values, is contemplated unless otherwise indicated. Certain lower limits, upper limits, and ranges appear in one or more of the following claims. All values are values indicated as "about" or "approximately" meaning that they take into account experimental error, machine tolerances, and other deviations expected by one of ordinary skill in the art.

The foregoing also outlines features of several embodiments so that those skilled in the art may better understand the present disclosure. Those skilled in the art will appreciate that they may readily use the present disclosure as a basis for designing or modifying other methods or apparatus for carrying out the same purposes and/or achieving the same advantages of the embodiments disclosed herein. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure, which is defined by the appended claims.

Various terms have been defined above. If a term used in a claim is not defined above, that term should have the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.

While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. A multicomponent fiber for a nonwoven comprising:

a first fiber component comprising a first polypropylene having an MFR of at least 30dg/min and a second polypropylene having an MFR of less than 20 dg/min; and

a second fiber component comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and from about 10wt% to about 30wt% of one or more alpha-olefin derived units based on the total weight of the elastomer, wherein the propylene-based elastomer has an MFR of at least 40dg/min and a heat of fusion (Hf) of from about 3J/g to about 75J/g as determined by DSC.

2. The fiber of claim 1, wherein the first polypropylene has an MFR of from 30dg/min to about 40 dg/min.

3. The fiber of claim 1, wherein the first polypropylene has a melting temperature (Tm) of at least 140 ℃.

4. The fiber of claim 1, wherein the second polypropylene has a melting temperature (Tm) of at least 140 ℃.

5. The fiber of claim 1, wherein the second polypropylene has an MFR of from 10dg/min to about 20 dg/min.

6. The fiber of claim 1, wherein the MFR of the second polypropylene is less than half the MFR of the first polypropylene.

7. The fiber of claim 1, wherein the MFR of the second polypropylene is 15% -40% of the MFR of the first polypropylene.

8. The fiber of claim 1, wherein the at least one propylene-based elastomer has an MFR of from 40dg/min to about 60 dg/min.

9. The fiber of claim 1, wherein the one or more alpha olefin derived units consist essentially of ethylene.

10. The fiber of claim 1, wherein the one or more alpha olefin derived units consist of ethylene.

11. The fiber of claim 1, wherein the at least one propylene-based elastomer has a tacticity index (m/r) of 4-12.

12. The fiber of claim 1, wherein the at least one propylene-based elastomer has about 0.84g/cm ³ -about 0.92g/cm ³ Is a density of (3).

13. The fiber of claim 1, wherein the at least one propylene-based elastomer has a percent crystallinity of from about 1% to about 40%.

14. The fiber of claim 1, wherein the ratio of the first polypropylene to the propylene-based elastomer in the second fiber component is in the range of 5/95 to 95/5.

15. The fiber of claim 1, wherein the ratio of the first polypropylene to the second polypropylene in the first fiber component is in the range of 20/80-80/20.

16. The fiber of claim 1, wherein the first polypropylene is a propylene homopolymer.

17. The fiber of claim 1, wherein the second polypropylene is a propylene homopolymer.

18. A method of making a fiber for a fabric having a suitable thickness and softness, the method comprising:

forming a first polymer composition comprising a first polypropylene having an MFR of at least 30dg/min and a second polypropylene having an MFR of less than 20 dg/min;

forming a second polymer composition comprising the first polypropylene and at least one propylene-based elastomer comprising propylene and from about 10 to about 30 weight percent, based on the total weight of the elastomer, of one or more alpha-olefin derived units and having an MFR of at least 40dg/min and a heat of fusion (Hf) of from about 3J/g to about 75J/g, as determined by DSC;

Forming a plurality of fibers from the first polymer composition and the second polymer composition in a side-by-side configuration; and

a fabric is made from the plurality of fibers, wherein the fabric has a thickness of at least 0.40mm, a total hand of less than 20g, and MD and CD tensile strengths of at least 8N/5 cm.

19. The method of claim 18, wherein the step of forming fibers comprises spunbond the first polymer composition and the second polymer composition to form side-by-side fibers.

20. The method of claim 18, further comprising directing the fibers to a spinning belt, laying the fibers on the spinning belt and forming a fabric from the fibers.

21. The process of claim 18, wherein the ratio of the first polypropylene to the second polypropylene in the first polymer composition is in the range of 20/80-80/20 and the ratio of the first polypropylene to the propylene-based elastomer in the second polymer composition is in the range of 5/95-95/5.

22. A hygiene product comprising the fiber of claim 1.

23. A method of characterizing a material, the method comprising:

placing a sample between a first parallel plate and a second parallel plate of a parallel plate rheometer;

Compressing the sample between the first parallel plate and the second parallel plate;

measuring a normal load on the first parallel plate; and

a gap distance between the first parallel plate and the second parallel plate under the normal load is measured.

24. The method of claim 23, wherein the sample is compressed between the first parallel plate and the second parallel plate at a compression rate.

25. The method of claim 23, wherein a plurality of normal loads are measured as the compression of the sample increases.

26. The method of claim 23, wherein a plurality of gap distances are measured as the compression of the sample increases.

27. The method of claim 23, wherein the sample is a nonwoven fabric.

28. The method of claim 23, further comprising:

measuring a first gap at a baseline load prior to compressing the sample;

after compressing the sample, decompressing the sample and measuring a second gap at baseline load; and

the elasticity of the sample is determined by comparing the first gap and the second gap.

29. The method of claim 23, further comprising:

generating a curve of normal force versus gap distance; and

the work of compression of the sample is determined by calculating the area under the curve.

30. The method of claim 23, further comprising:

generating a curve of normal force versus gap distance; and

the stiffness of the sample is determined by calculating the slope of the curve at a particular load.