CN113039315A

CN113039315A - Bicomponent fibers and nonwovens produced therefrom

Info

Publication number: CN113039315A
Application number: CN201980075237.7A
Authority: CN
Inventors: S·S·S·塔露里; L·K·阿帕拉库-伯尔迪; P·E·小罗林; 赵斌
Original assignee: ExxonMobil Chemical Patents Inc
Current assignee: ExxonMobil Chemical Patents Inc
Priority date: 2018-09-18
Filing date: 2019-08-30
Publication date: 2021-06-25
Also published as: WO2020060747A1; EP3853401A1; EP3853401A4

Abstract

The process may comprise (a) extruding a bicomponent fiber comprising: a first component comprising a first polypropylene homopolymer; and a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer; (b) cooling the bicomponent fiber; and (c) thermally and/or mechanically activating the bicomponent fibers to cause the bicomponent fibers to bend.

Description

Bicomponent fibers and nonwovens produced therefrom

Priority

This application claims priority and benefit from U.S. provisional application No. 62/732,599 filed on 18.9.2018 and european patent application No. 18199603.4 filed on 10.10.2018, the disclosures of which are incorporated herein by reference in their entirety.

FIELD

The present disclosure relates to bicomponent fibers that enhance loft (loft) of nonwoven materials when used to produce nonwoven materials.

Background

Synthetic fibers and nonwoven fabrics often lack the soft feel or "hand" like natural fibers and fabrics. The different aesthetic perception is due to the lack of "loftiness" or "bulk" in the synthetic material relative to the inherent space-filling characteristics of natural fibers. Natural fibers are generally not planar materials and instead they exhibit some three-dimensional crimp or texture that allows for space between the fibers. Natural fibers can be laid on a flat surface and have a surface protrusion from the flat surface, which is "3-dimensional". In contrast, synthetic fibers are substantially planar. There are many ways to impart "bulk" or "loftiness" to synthetic fibers or fabrics, including mechanical treatments such as creping, air-jet texturing, or pleating. These processes are not generally readily applied to spunbond nonwoven fabrics in a cost effective manner.

SUMMARY

A first embodiment is a method comprising (or consisting of, or consisting essentially of): (a) extruding a bicomponent fiber comprising: a first component comprising a first polypropylene homopolymer; and a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer; (b) cooling the bicomponent fiber; and (c) thermally and/or mechanically activating the bicomponent fibers to cause the bicomponent fibers to bend.

A second embodiment is a bicomponent fiber comprising: a first component comprising a first polypropylene homopolymer; and a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer.

A third embodiment is a nonwoven article comprising the bicomponent fiber of the second embodiment.

A fourth embodiment is a laminate comprising the bicomponent fiber of the second embodiment.

Brief description of the drawings

The following figures are included to illustrate certain aspects of embodiments and should not be taken as exclusive embodiments. The subject matter disclosed is capable of considerable modification, alteration, combination, and equivalents in form and function, as will occur to those ordinarily skilled in the pertinent art and having the benefit of this disclosure.

FIG. 1 is a graph of shrinkage for fibers of the examples (ASTM D2259-02 (2016)).

Fig. 2A is a scanning electron micrograph of the bicomponent fiber produced prior to mechanical activation.

Fig. 2B is a scanning electron micrograph of the bicomponent fiber produced after mechanical activation.

Fig. 3A and 3B are optical micrographs of the fibers produced prior to heat activation.

Fig. 3C and 3D are samples after thermal activation at 100 ℃ for 15 seconds.

FIG. 4 is a graph of shrinkage for the example fibers (ASTM D2259-02 (2016)).

Detailed Description

The present disclosure relates to bicomponent fibers that enhance loft of nonwoven materials when used to produce nonwoven materials. More specifically, the bicomponent fiber comprises: a first component comprising a first polypropylene homopolymer, and a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer. The blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer. That is, if the melt flow rate of the first polypropylene homopolymer is 36g/10min (ASTM D1238-13, 2.16kg, 230 ℃), the melt flow rate of the blend is greater than 43g/10min (ASTM D1238-13, 2.16kg, 230 ℃) or less than 29g/10min (ASTM D1238-13, 2.16kg, 230 ℃).

Definition of

As used herein, "extruding" or "extruded" means forcing the material in its molten or flowable state through a mechanical containment device such as a tube, a preform die, a die (preferably having a desired constricted diameter and/or shape), or an extruder (heated or otherwise) such that the material flows from one point to another, such as an unmelted polymer source, to form a molten stream of such polymer in the stream or formed stream.

As used herein, "spunbond" refers to a melt-spinning process for forming a fabric in which a polymer melt or solution is extruded through a spinneret to form filaments, the filaments are cooled and then attenuated by a suitable means, such as by an electrostatic charge or high velocity air, and such attenuated filaments ("fibers") are then laid down on a moving web to form the fabric. The fibers produced by the spunbond process typically have some degree of molecular orientation imparted to them.

As used herein, "meltblown" refers to a process in which a polymer melt or solution is extruded through a spinneret to form filaments, the filaments are attenuated by a suitable device, such as by an electrostatic charge or high velocity air, and such attenuated filaments ("fibers") are then laid down on a moving web to form a fabric. The fibers themselves may be referred to as "spunbond" or "meltblown".

As used herein, the term "coform" refers to another meltspinning process in which at least one meltspinning die is positioned adjacent to a chute through which other materials are added to the fabric while the fabric is being formed. Such other materials may be, for example, pulp, superabsorbent particles, cellulose or short fibers. Co-molding processes are described in US 4,818,464 and US 4,100,324. For the purposes of this disclosure, a coform process is considered a particular embodiment of a melt spinning process. In certain embodiments, the propylene-based fabric described herein is a coform fabric.

As used herein, a "fiber" is a structure whose length is much greater than its diameter or width; with an average diameter of the order of 0.1 μm to 250 μm and comprising natural and/or synthetic materials. The fibers may be "monocomponent" or "bicomponent". Bicomponent fibers comprise two different chemical and/or physical properties extruded from separate extruders but the same spinneret, with the two polymers within the same filament, resulting in fibers having different domains. The configuration of such bicomponent fibers may be, for example, a sheath/core arrangement in which one polymer is surrounded by another, either side-by-side (as described in US 5,108,820) or in the form of islands-in-the-sea (as described in US7,413,803).

Regardless of how formed, any "web" of fibers may be used as is (unbonded), or bonded, such as by heating, for example by passing the web of fibers through a heated calender or roll.

As used herein, a "laminate" comprises at least two fabrics and/or film layers. The laminate may be formed by any means known in the art. Such a laminate can be produced, for example, as follows: sequentially depositing a first layer of meltspun fabric onto a moving forming belt followed by another layer of meltspun fabric, or adding a dry-laid fabric on top of the first layer of meltspun fabric and then adding a layer of meltspun fabric on top of these layers, followed by some bonding of the laminate, such as by thermal point bonding or the inherent tendency of the layers to adhere to one another, hydroentangling, and the like. Alternatively, the fabric layers may be prepared separately, collected into rolls and combined in a separate bonding step or steps. The multilayer laminate may also have a different number of layers in many different configurations and may include other materials such as films or coform materials, meltblown and spunbond materials, airlaid materials, and the like.

As used herein, a "membrane" is a flat unsupported section of plastic and/or elastomeric material whose thickness is very narrow relative to its width and length and has a macroscopic morphology that is continuous or nearly continuous throughout its structure, thereby allowing air to pass at diffusion-limited rates or lower. The laminates described herein may include one or more film layers and may comprise any material as described herein for use in a fabric. In certain embodiments, no film is present in the laminates described herein. The films described herein may contain additives that facilitate perforation and the passage of air and/or fluid through the film upon treatment. Additives such as clays, antioxidants, and the like, as described herein, may also be added.

Polypropylene homopolymer

The bicomponent fibers of the present invention comprise: a first component comprising a first polypropylene homopolymer, and a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer. The first and second polypropylene homopolymers may be the same or different. As used herein, the term "polypropylene homopolymer" refers to a polymer having only propylene monomer units and is commonly used to describe the first and second propylene homopolymers. That is, the composition and properties of the propylene homopolymer are adapted to the first propylene homopolymer and/or the second propylene homopolymer.

In certain embodiments, the polypropylene homopolymer is predominantly crystalline, as evidenced by having a melting point generally greater than 110 ℃, alternatively greater than 115 ℃, and most preferably greater than 130 ℃, or in the range from 110 ℃, or 115 ℃, or 130 ℃ to 150 ℃, or 160 ℃, or 170 ℃. The term "crystalline" as used herein is characterized by those polymers having a high degree of intermolecular and intramolecular order. The polypropylene preferably has a heat of fusion of greater than 60J/g, alternatively at least 70J/g, alternatively at least 80J/g, as determined by DSC analysis. The heat of fusion depends on the composition of the polypropylene.

The weight average molecular weight (Mw) of the polypropylene homopolymer may range from 40,000 g/mole, or 50,000 g/mole or 80,000 g/mole to 200,000 g/mole, or 400,000 g/mole, or 500,000 g/mole or 1,000,000 g/mole. The number average molecular weight (Mn) is in the range of from 20,000 g/mole, or 30,000 g/mole or 40,000 g/mole to 50,000 g/mole, or 55,000 g/mole, or 60,000 g/mole or 70,000 g/mole. The z-average molecular weight (Mz) is at least 300,000 g/mole, or 350,000 g/mole, or in the range of from 300,000 g/mole or 350,000 g/mole to 500,000 g/mole. In any embodiment, the molecular weight distribution (Mw/Mn) is less than 5.5, or 5, or 4.5, or 4, or in the range from 1.5, or 2, or 2.5, or 3 to 4, or 4.5, or 5, or 5.5.

The polypropylene homopolymer may have a Melt Flow Rate (MFR) in the range of from 1g/10min to 500g/10min, alternatively from 1g/10min, or 5g/10min, or 10g/10min, or 15g/10min, or 20g/10min, or 25g/10min to 45g/10min, or 55g/10min, or 100g/10min, or 300g/10min, or 350g/10min, or 400g/10min, or 450g/10min, or 500g/10min, as measured according to ASTM D1238-13 using a 2.16kg load at 230 ℃ (ASTM D1238-13, 2.16kg, 230 ℃).

There is no particular limitation on the method of preparing the polypropylene homopolymer of the present invention. For example, the polymer may be a propylene homopolymer obtained by homopolymerization of propylene in a single-stage or multistage reactor. The polymerization process includes high pressure, slurry, gas, bulk or solution phase or combinations thereof, using conventional ziegler-natta catalysts or single site metallocene catalyst systems or combinations thereof, including bimetallic supported catalyst systems. The polymerization may be carried out by a continuous or batch process and may include the use of chain transfer agents, scavengers, or other additives deemed suitable. Most preferably, however, a ziegler-natta catalyst is used to form the polypropylene homopolymer.

The polypropylene homopolymer may be reactor grade, meaning that it has not undergone any post-reactor modification by reaction with peroxide, with a crosslinking agent, with an electron beam, with gamma radiation, or other types of controlled rheology modification. In any embodiment, the polypropylene homopolymer may be visbroken by peroxides, as is known in the art. In any case, the polyolefins used in the examples listed herein and described above have the properties as used, with or without visbreaking.

Polypropylene in polypropylene homopolymerAn exemplary commercially available product of the polymer is ExxonMobil^TMPP3155(36g/10min MFR (ASTM D1238-13, 2.16kg, 230 ℃) homopolymer, available from ExxonMobil Chemical Company), ExxonMobil^TMPP3155E5(36g/10min MFR (ASTM D1238-13, 2.16kg, 230 ℃) homopolymer available from ExxonMobil Chemical Company), ExxonMobil^TMPP1264E1(20g/10min MFR (ASTM D1238-13, 2.16kg, 230 ℃) homopolymer available from ExxonMobil Chemical Company), ExxonMobil^TMPP1105E1(35g/10min MFR (ASTM D1238-13, 2.16kg, 230 ℃) homopolymer available from ExxonMobil Chemical Company), ExxonMobil^TMPP1074KNE1(20g/10min MFR (ASTM D1238-13, 2.16kg, 230 ℃) homopolymer available from ExxonMobil Chemical Company), Achieve^TMAdvanced PP1605(32g/10min MFR (ASTM D1238-13, 2.16kg, 230 ℃) homopolymer available from ExxonMobil Chemical Company) and Achieve^TMAdvanced PP3854(24g/10min MFR (ASTM D1238-13, 2.16kg, 230 ℃) homopolymer, available from ExxonMobil Chemical Company).

The bicomponent fiber comprises: a first component comprising a first polypropylene homopolymer, and a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer.

The amount of polypropylene homopolymer or blend of propylene homopolymers in the first component can be from 80 wt% to 100 wt%, or from 90 wt% to 99 wt%, or from 95 wt% to 98 wt%, based on the weight of the first component. The first component may optionally further comprise additives described herein.

The amount of polypropylene homopolymer or blend of propylene homopolymers in the second component can be from 10 wt% to 90 wt%, or from 20 wt% to 50 wt%, or from 50 wt% to 80 wt%, based on the weight of the second component. The second component may optionally further comprise additives described herein.

Propylene-based elastomers

The propylene-based elastomer as described herein is a propylene-derived unit and is derived from ethylene or C₄-C₁₀Copolymers of units of at least one of the alpha-olefins. Based on propyleneThe elastomer may contain at least 50 wt% propylene derived units. The propylene-based elastomer may have limited crystallinity resulting from adjacent isotactic propylene units and a melting point as described herein. The crystallinity and melting point of propylene-based elastomers can be reduced by introducing errors in propylene insertion compared to highly isotactic polypropylene. Propylene-based elastomers are generally free of any substantial intermolecular heterogeneity in tacticity and comonomer composition, and also generally free of any substantial heterogeneity in intramolecular composition distribution.

The amount of propylene-derived units present in the propylene-based elastomer can range from an upper limit of 95 wt%, 94 wt%, 92 wt%, 90 wt%, or 85 wt% to a lower limit of 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 84 wt%, or 85 wt% of the propylene-based elastomer. Comonomer derived units include ethylene or C₄-C₁₀At least one of the alpha-olefins may be present in an amount of 1 to 35 wt%, or 5 to 35 wt%, or 7 to 32 wt%, or 8 to 25 wt%, or 8 to 20 wt%, or 8 to 18 wt% of the propylene-based elastomer. The comonomer content can be adjusted so that the propylene-based elastomer has a heat of fusion of less than 80J/g, a melting point of 105 ℃ or less, and a crystallinity of 2% to 65% of the crystallinity of isotactic polypropylene, and an MFR (ASTM D1238-13, 2.16kg, 230 ℃) in the range of 2g/10min-50 g/min.

In a preferred embodiment, the comonomer is ethylene, 1-hexene or 1-octene, with ethylene being most preferred. In embodiments where the propylene-based elastomer comprises ethylene-derived units, the propylene-based elastomer may comprise from 5 wt% to 25 wt%, or from 8 wt% to 20 wt%, or from 9 wt% to 16 wt% ethylene-derived units. In some embodiments, the propylene-based elastomer consists essentially of units derived from propylene and ethylene, i.e., the propylene-based elastomer does not contain any other comonomer in amounts other than those typically present as impurities in the ethylene and/or propylene feed streams used in the polymerization process, or in amounts that will substantially affect the heat of fusion, melting point, crystallinity, or melt flow rate of the propylene-based elastomer, or such that any other comonomer is intentionally added to the polymerization process.

In some embodiments, the propylene-based elastomer may comprise more than one comonomer. Preferred embodiments of propylene-based elastomers having more than one comonomer include propylene-ethylene-octene, propylene-ethylene-hexene, and propylene-ethylene-butene polymers. In the presence of more than one monomer derived from ethylene or C₄-C₁₀In embodiments where the comonomer is at least one of an alpha-olefin, the amount of one comonomer may be less than 5 wt% of the propylene-based elastomer, but the total amount of comonomer in the propylene-based elastomer is 5 wt% or greater.

The propylene-based elastomer may have a triad tacticity of at least 75%, at least 80%, at least 82%, at least 85%, or at least 90% of three propylene units, such as by¹³C NMR measurement. Preferably, the propylene-based elastomer has a triad tacticity of from 50% to 99%, or from 60% to 99%, or from 75% to 99%, or from 80% to 99%. In some embodiments, the propylene-based elastomer may have a triad tacticity of 60% to 97%.

The propylene-based elastomer has a heat of fusion ("H") as determined by DSC of 80J/g or less, or 70J/g or less, or 50J/g or less, or 40J/g or less_f"). The propylene-based elastomer may have an H of 0.5J/g, or 1J/g or 5J/g_fThe lower limit. E.g. H_fValues can range from 1.0J/g, 1.5J/g, 3.0J/g, 4.0J/g, 6.0J/g, or 7.0J/g to 30J/g, 35J/g, 40J/g, 50J/g, 60J/g, 70J/g, 75J/g, or 80J/g.

The propylene-based elastomer may have a percent crystallinity of from 2% to 65%, or from 0.5% to 40%, or from 1% to 30%, or from 5% to 35% of the crystallinity of isotactic polypropylene, as determined according to the DSC procedure described herein. The heat energy of propylene having 100% crystallinity was assumed to be 189J/g. In some embodiments, the copolymer has a crystallinity that is less than 40%, or in the range of 0.25% to 25%, or in the range of 0.5% to 22% of the crystallinity of the isotactic polypropylene.

In some embodiments, the propylene-based elastomer may further comprise diene-derived units (as used herein, "dienes"). The optional diene can be any hydrocarbon structure having at least two unsaturated bonds, wherein at least one unsaturated bond is readily incorporated into the polymer. For example, the optional diene may be selected from linear acyclic olefins such as 1, 4-hexadiene and 1, 6-octadiene; branched acyclic olefins such as 5-methyl-1, 4-hexadiene, 3, 7-dimethyl-l, 6-octadiene and 3, 7-dimethyl-l, 7-octadiene; monocyclic alicyclic olefins such as 1, 4-cyclohexadiene, 1, 5-cyclooctadiene and 1, 7-cyclododecadiene; polycyclic cycloaliphatic fused and bridged cycloalkenes, such as tetrahydroindene, norbornadiene, methyl-tetrahydroindene, dicyclopentadiene, bicyclo- (2.2.1) -hepta-2, 5-diene, norbornadiene, alkenylnorbornene, alkylidene norbornenes such as ethylidene norbornene ("ENB"), cycloalkenylnorbornene and cycloalkylidene (cycloakyline) norbornene (e.g., 5-methylene-2-norbornene, 5-ethylidene-2-norbornene, 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene, 5- (4-cyclopentenyl) -2-norbornene, 5-cyclohexylidene-2-norbornene, 5-vinyl-2-norbornene); and cycloalkenyl-substituted alkenes such as vinylcyclohexene, allylcyclohexene, vinylcyclooctene, 4-vinylcyclohexene, allylcyclodecene, vinylcyclododecene and tetracyclo- (A-l 1,12) -5, 8-dodecene. The amount of diene-derived units present in the propylene-based elastomer may range from an upper limit of 15%, 10%, 7%, 5%, 4.5%, 3%, 2.5%, or 1.5% to a lower limit of 0%, 0.1%, 0.2%, 0.3%, 0.5%, 1%, 3%, or 5%, by weight of the propylene-based elastomer.

The propylene-based elastomer may have a single-peak melt transition as determined by DSC. In some embodiments, the copolymer has a major peak transition of 90 ℃ or less, and a broad melt transition end point of 110 ℃ or more. Peak "melting point" ("T)_m") is defined as the temperature of maximum heat absorption when the sample melts. However, the copolymer may exhibitA minor melting peak adjacent to the major peak and/or at the end of the melting transition. For purposes of this disclosure, such minor melting peaks are collectively considered to be a single melting point, the highest of these peaks being considered to be the T of the propylene-based elastomer_m. The propylene-based elastomer can have a T of 110 ℃ or less, 105 ℃ or less, 100 ℃ or less, 90 ℃ or less, 80 ℃ or less, or 70 ℃ or less_m. In some embodiments, the propylene-based elastomer has a T of from 25 ℃ to 105 ℃, or from 60 ℃ to 105 ℃, or from 70 ℃ to 105 ℃, or from 90 ℃ to 105 ℃_m。

The propylene-based elastomer may have a density of 0.850g/cm³To 0.900g/cm³Or 0.860g/cm³To 0.880g/cm³At 22 ℃ according to ASTM D1505-18.

The propylene-based elastomer may have a melt flow rate ("MFR") of at least 2g/10min, as measured at 230 ℃ according to ASTM D1238-13, 2.16 kg. In some embodiments, the propylene-based elastomer may have an MFR of from 2g/10min to 50g/10min, or from 2g/10min to 20g/10min, or from 30g/10min to 50g/10min, or from 40g/10min to 50g/10 min.

The propylene-based elastomer may have an elongation at break of less than 2000%, less than 1800%, less than 1500%, less than 1000%, or less than 800%, as measured by ASTM D412-16.

The propylene-based elastomer can have a weight average molecular weight (Mw) of 5,000 to 5,000,000 g/mole, or 10,000 to 1,000,000 g/mole, or 50,000 to 400,000 g/mole. The propylene-based elastomer can have a number average molecular weight (Mn) of 2,500 g/mole to 250,000 g/mole, or 10,000 g/mole to 250,000 g/mole, or 25,000 g/mole to 250,000 g/mole. The propylene-based elastomer can have a z-average molecular weight (Mz) of from 10,000 g/mole to 7,000,000 g/mole, or from 80,000 g/mole to 700,000 g/mole, or from 100,000 g/mole to 500,000 g/mole. Finally, the propylene-based elastomer can have a molecular weight distribution MWD of 1.5 to 20, or 1.5 to 15, or 1.5 to 5, or 1.8 to 3, or 1.8 to 2.5.

The first component and/or the second component of the bicomponent fibers disclosed herein can include one or more different propylene-based elastomers, such as distinct propylene-based elastomers each having one or more different properties, such as different comonomer or comonomer contents. Such combinations of various propylene-based elastomers are within the scope of the present invention.

The propylene-based elastomer may comprise a copolymer prepared according to the procedures described in WO/2002/036651, US6,992,158 and/or WO/2000/001745. Preferred processes for producing propylene-based elastomers can be found in US7,232,871 and US6,881,800. The present invention is not limited by any particular polymerization process used to prepare the propylene-based elastomer, and the polymerization process is not limited by any particular type of reaction vessel.

Suitable propylene-based elastomers may be available under the trade name Vistamaxx^TM(available from ExxonMobil Chemical Company), VERSIFY^TM(available from The Dow Chemical Company), certain brands of TAFMER^TMXM or NOTIO^TMAvailable from Mitsui Company), and certain brands of SOFTEL^TMCommercially available (available from Basell polyofins). The specific brand(s) of commercially available propylene-based elastomer suitable for use in the present invention can be readily determined using methods well known in the art.

The amount of the propylene-based elastomer or blend of propylene-based elastomers in the second component can be from 10 wt% to 90 wt%, or from 20 wt% to 50 wt%, or from 50 wt% to 80 wt%, based on the weight of the second component. The second component may optionally further comprise additives described herein.

Blend of second component

The second component of the bicomponent fiber comprises a blend comprising a propylene-based elastomer and a second polypropylene homopolymer.

The blend may have an MFR (ASTM D1238-13, 2.16kg, 230 ℃) of at least 2g/10 min. In some embodiments, the propylene-based elastomer may have an MFR of from 2g/10min to 50g/10min, or from 2g/10min to 20g/10min, or from 30g/10min to 50g/10min, or from 40g/10min to 50g/10 min. The blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer.

The weight ratio of propylene homopolymer(s) to propylene-based elastomer(s) in the second component may be from 10:90 to 90:10, or from 20:80 to 80:20, or from 15:85 to 50:50, or from 30:70 to 40:60, or from 50:50 to 85:15, or from 60:40 to 70: 30.

Additive agent

Various additives may be incorporated into the blends of propylene homopolymers and/or second components described above for use in making fibers and fabrics. Such additives include, for example, stabilizers, antioxidants, fillers, colorants, nucleating agents, and slip additives. Primary and secondary antioxidants include, for example, hindered phenols, hindered amines, and phosphate esters. Nucleating agents include, for example, sodium benzoate and talc. In addition, other nucleating agents such as Ziegler-Natta olefin products or other highly crystalline polymers may also be employed. Other additives such as dispersants, e.g., ACROWAX, may also be included^TMC (available from Lonza). Slip agents include, for example, oleamide and erucamide. Catalyst deactivators such as calcium stearate, hydrotalcite, and calcium oxide, and/or other acid neutralizers known in the art are also commonly used.

Other additives include, for example, fire retardants/retardants, plasticizers, vulcanization or curing agents, vulcanization or curing accelerators, cure retarders, processing aids, tackifying resins, and the like. The aforementioned additives may also include fillers and/or reinforcing materials, independently added or incorporated into the additive. Examples include carbon black, clay, talc, calcium carbonate, mica, silica, silicates, combinations thereof, and the like. Other additives that may be used to enhance properties include antiblocking agents, lubricants, and nucleating agents. The list described herein is not intended to include all types of additives that may be used with the present invention. Upon reading this disclosure, one skilled in the art will appreciate that other additives may be used to enhance properties. As understood by those skilled in the art, the blends of the present invention can be modified to adjust the properties of the blend as desired.

In any embodiment, the blend of the second component described herein can comprise (or consist of): a propylene-based elastomer, a second polypropylene homopolymer, and an additive in a range from 0.1 wt% to 3 wt%, or 4 wt% or 5 wt%, based on the weight of the blend. Most preferably, those additives include primary and secondary antioxidants, acid scavengers, nucleating agents and pigments or other colorants.

Blending of

The blend of the second component described herein can be prepared by any procedure that produces a mixture of the components, such as dry blending, melt blending, and the like. In certain embodiments, a complete mixture of polymer components is indicated by the morphological homogeneity of the dispersion of the polymer components.

Melt blending: continuous melt mixing equipment is typically used. These processes are well known in the art and include single and twin screw compounding extruders as well as other machines and processes designed to intimately homogenize the polymer components.

Dry mixing: the propylene-based elastomer, the second polypropylene homopolymer, and other optional components may be dry blended and fed directly to the fiber or nonwoven process extruder. Dry blending is accomplished by combining the propylene-based elastomer, the second polypropylene homopolymer, and other optional components in a dry blending apparatus. Such equipment and processes are well known in the art and include drum tubers (twin cone mixers), and the like. In this case, the propylene-based elastomer, the second polypropylene homopolymer and other optional components are melted (when available) and homogenized in a process extruder similar to the melt blending process. Instead of making pellets, the homogenized molten polymer is delivered to a die or spinneret to form fibers and fabrics.

Method for producing a nonwoven fabric of fibres

The present invention also discloses a process for producing a nonwoven fabric of bicomponent fibers, the process comprising: (a) forming a first component polymer melt comprising: a first polypropylene homopolymer, (b) forming a second component polymer melt comprising: a propylene-based elastomer and a second polypropylene homopolymer, (c) extruding (e.g., by a melt-spinning process or a spunbond process) the first component polymer melt and the second component polymer melt through a die configured for a desired bicomponent fiber composition cross-section, and (d) cooling the bicomponent fiber. In such processes, the vast majority of the bicomponent fibers produced do not curl or buckle. That is, the crimped or bent portions of the bicomponent fibers are less than 5 weight percent of the total weight of the bicomponent fibers.

Desirable bicomponent fiber composition cross-sections include, but are not limited to, side-by-side, segmented, sheath/core, islands-in-the-sea structures ("matrix microfibers"), and other cross-sections known in the art. The first component described herein may constitute from 10 wt% to 90 wt% of the bicomponent fiber, or from 20 wt% to 80 wt% of the bicomponent fiber, or from 25 wt% to 60 wt% of the bicomponent fiber, or from 40 wt% to 75 wt% of the bicomponent fiber. The second component may constitute the balance of the bicomponent fiber.

The method may further comprise (e) thermally and/or mechanically activating the bicomponent fibers to cause the bicomponent fibers to curl or buckle. Activation preferably occurs after cooling of the bicomponent fibers and before thermal bonding (e.g., via calendering). For example, activation can occur immediately after the fibers are laid on the forming belt. In another example, activation may occur after the compaction rolls but before calendering.

Activation can be accomplished using, for example, a hot air knife, a heated roller (e.g., using heated oil or a heating coil), a mechanical crimping roller, a fabric tensioning roller, and the like, and any combination thereof. Heat activation may include heating the bicomponent fiber to 50 ℃ or more (e.g., 50 ℃ to 150 ℃, or 75 ℃ to 125 ℃, or 90 ℃ to 115 ℃) for 1 second or more (e.g., 1 second to 5 minutes, or 1 second to 1 minute, or 5 seconds to 15 seconds). Mechanical activation may include applying a force of at least 0.01N (e.g., 0.01N to 10N, or 0.1N to 5N, or 0.5N to 2N) to the bicomponent fibers. The thermal and/or mechanical activation can cause the fiber to have a shrinkage of at least 5% (e.g., 5% to 80%, or 20% to 75%, or 40% to 65%), as determined by ASTM D2259-02 (2016).

In certain embodiments, the spunbond process comprises a process of melt extruding (or "extruding") the desired material through one or more dies, and then attenuating (drawing) streams of the molten material with pressurized air to create a venturi effect. The materials may be added to their respective melt extruders as pellets with the desired additives, or the additives may be combined in this step.

In particular, the formation of bicomponent fibers is accomplished as follows: the molten material is extruded through a suitable die as is known in the art to produce the desired bicomponent fiber composition cross-section, followed by quenching the molten material (having the desired melting temperature within the die) with a quench air system (whose temperature can be controlled). Common quench air systems include those that deliver temperature controlled air in the direction of cross flow. The filaments are then pulled from the spinneret or spinnerets and attenuated accordingly. To achieve this, the filaments are attenuated by a venturi device in which they are accelerated and/or attenuated due to the pressurized air flow. Increasing the air velocity within the venturi device may be accomplished by various methods described in the art, including increasing the air pressure within the venturi device. Generally, increasing this air velocity (e.g., by increasing air pressure) results in increased filament velocity and greater filament attenuation. The higher the air pressure, the more the polymer melt of the bicomponent fiber accelerates and thus attenuates, in terms of the speed and denier of the fiber formed therefrom. To achieve finer fibers, high air pressure is desired. However, this is balanced with the tendency of the filaments to break due to excessive pressure. The polymer melt of the bicomponent fibers described herein can be attenuated using higher air pressure than is typical in other spunbond processes. In any embodiment, the attenuating air pressure used in the spunbond process is greater than 2000Pa or 3000Pa or 4000Pa or 6000Pa, and in other embodiments less than 600kPa or 500kPa or 400 kPa; and in other embodiments in the range from 2000Pa or 3000Pa or 4000Pa to 8000Pa or 10,000Pa or 15,000 Pa. Such air pressure may be generated within a closed area, such as a "cabin," where the fibers are attenuated, and the air pressure therein is sometimes referred to as "cabin pressure.

Air attenuation can be achieved in any manner, such as that described, and the process is not limited to any particular method of attenuation of the filaments. In any embodiment, the venturi effect of attenuating the fibers is obtained by pulling filaments of the polymer melt of the bicomponent fibers (slot draw) using an aspirator slot that extends along the width of the machine. In another embodiment, the venturi effect is obtained by drawing the filaments through a nozzle or aspirator gun. Multiple guns may be used because the hole size may be varied to achieve the desired effect. The bicomponent fibers so formed are collected on a screen ("wire") in any embodiment, or on a porous forming belt in another embodiment to form a web of filaments. Typically, a vacuum is maintained on the underside of the belt to promote the formation of a uniform fabric and to remove the air used to attenuate the filaments and create air pressure. The actual method of air attenuation is not critical as long as the desired accelerated air velocity (typically reflected by air pressure) and hence venturi effect is achieved to attenuate the bicomponent fiber.

In any embodiment, the pressure in the die orifice area is generated by a gear pump. The method of forming the pressure in the die area is not critical, but the pressure inside the die area ranges from 35 bar to 50 bar (3500kPa to 5000kPa) in any embodiment, and from 36 bar to 48 bar (3600kPa to 4800kPa) in another embodiment, and from 37 bar to 46 bar (3700kPa to 4600kPa) in yet another embodiment.

The melt temperature in the die of the polymer melt of the bicomponent fiber ranges from 200 ℃ to 260 ℃ in any embodiment, and from 200 ℃ to 250 ℃ in yet another embodiment, and from 210 ℃ to 245 ℃ in yet another embodiment.

In certain embodiments, the spunbond line throughput ranges from 150kg/hr or 170kg/hr to 200kg/hr or 270kg/hr or 300 kg/hr. In certain other embodiments, the spunbond line throughput/hole ranges from 0.20 grams/hole/minute or 0.30 grams/hole/minute or 0.40 grams/hole/minute to 0.60 grams/hole/minute or 0.70 grams/hole/minute or 0.90 grams/hole/minute.

In certain embodiments, the spunbond process is conducted at a spinning speed ranging from 700m/min, or 900m/min, or 1100m/min, or 1300m/min, or 1500m/min to 2000m/min, or 2500m/min, or 3000m/min, or 3500m/min, or 4000m/min, or 4500m/min, or 5000 m/min.

In forming propylene-based fabrics, there is a method of dispersing or distributing the bicomponent fibers in any amount to form a uniform fabric. In any embodiment, a fixed or moving guide is used. In another embodiment, electrostatic or air turbulence is used to improve fabric uniformity. Other means as known in the art may also be used. In any event, the formed fabric is typically passed through a press roll to improve fabric integrity. In any embodiment, the fabric is then passed between heated calender rolls, wherein the raised regions on one roll bond the fabric at certain points to further improve the integrity of the spunbond fabric. The compression and heating calender may be separate from the zone where the filaments are formed in any embodiment.

Preferably, the fabric so formed (bonded or unbonded) is exposed to a cooling environment to a temperature of less than 50 ℃, or 45 ℃, or 40 ℃, or in the range of 20 ℃ to 50 ℃. Cooling may be achieved by any means, such as cooling air or cooling rollers. After cooling, the fabric is heated, preferably on calender rolls, heated air or heated oven environment, etc., to a temperature of at least 50 ℃, or 55 ℃, or 60 ℃, or 65 ℃, or 70 ℃, or 75 ℃, or 80 ℃, or 85 ℃, or 90 ℃, or in the range from 50 ℃, or 55 ℃ to 80 ℃, or 90 ℃, or 100 ℃, or 125 ℃, or 155 ℃. More particularly, heat may be applied by any suitable method known in the art, such as heated air, infrared heaters, heated nip rolls, or partial wrapping of a fabric or laminate around one or more heated rolls or steam cans, and the like. Heat may also be applied to the grooved roll itself. It should also be understood that other grooved roll arrangements are equally suitable, such as two grooved rolls positioned directly adjacent to each other. The percent bond area is typically 18% to 25% of the fabric. The bond area may be, and preferably is, reduced, for example, to 10% to 15% of the fabric to enhance the loft of the fabric and maintain the crimp of the fibers.

Various additional potential machining and/or finishing steps known in the art, such as slitting, processing, printing patterns, etc., may be performed without departing from the spirit and scope of the present invention. For example, the fabric or fabric-containing laminate may optionally be mechanically stretched in the cross direction and/or machine direction to enhance extensibility. In any embodiment, the fabric or laminate may be passed through two or more rolls having grooves in the CD and/or MD directions. Such grooved adjunct/anvil roll arrangements are described in US 2004/0110442 and US 2006/0151914 and US 5,914,084. For example, the fabric or laminate may be passed over two or more rolls having grooves in the CD and/or MD directions. The grooved rollers may be composed of steel or other hard materials (e.g., hard rubber). In addition to grooved rolls, other techniques may be used to mechanically stretch the composite in one or more directions. For example, the composite material may be passed through a tenter frame that stretches the composite material. Such tenter frames are well known in the art and are described, for example, in US 2004/0121687.

Regardless of how formed and oriented, the propylene-based fabric comprises fibers having an average diameter, in certain embodiments, of less than 20 or 17 or 15 or 12 μm, alternatively from 0.5, or 1, or 2, or 3, or 4 to 12, or 15, or 17, or 20 μm, and/or a denier (g/9000m), in certain embodiments, of less than 2.0 or 1.9 or 1.8 or 1.6 or 1.4 or 1.2 or 1.0, alternatively from 0.2, or 0.4, or 0.6 to 1.0, or 1.2 or 1.4 or 1.6 or 1.8 or 2.0. Such fabrics have an MD tensile strength (WSP 110.4(05)) when oriented at temperatures in the range of 110-150 ℃ (calender set temperature) of greater than 20 or 25N/5cm in certain embodiments. In other embodiments the fabric has a CD tensile strength (WSP 110.4(05)) greater than 10N/5cm or 15N/5cm when oriented at a temperature in the range of 110 ℃ to 150 ℃ (calender set temperature).

In certain embodiments, one or more propylene-based fabrics may form a laminate with itself or with other minor layers. Lamination of the individual layers may be performed such that CD and/or MD orientation is imparted to the fabric or laminate, particularly where the laminate includes at least one elastomeric layer. The laminate comprising the elastomeric film and/or fabric layer may be formed in a number of ways, which remain elastomeric once the laminate layers are bonded together. One approach is to fold, wrinkle, pucker (crease), or otherwise gather the fabric layer prior to bonding it to the elastomeric film. The gathered web is bonded to the film at specific points or lines, rather than continuously across the surface of the film. The fabric remains wrinkled or wrinkled on the film while the film/fabric is in a relaxed state; once the elastomeric film is stretched, the fabric layers flatten out until the gathered material is substantially flat, at which point the elastomeric stretch ceases.

Another approach is to stretch the elastomeric film/fabric and then bond the fabric to the film while the film is stretched. Again, the fabric is bonded to the film at designated points or lines, rather than continuously across the film surface. When the stretched film is relaxed, the fabric is wrinkled or wrinkled over the unstretched elastomeric film.

Another approach is to "neck down" (tack) the web prior to bonding the web to the elastomeric layer, as described in US 5,336,545, US 5,226,992, US 4,981,747, and/or US 4,965,122. Necking is the process of pulling the fabric in one direction, which causes the fibers in the fabric to slide closer together and the width of the fabric to decrease in the direction perpendicular to the direction of pulling. If the necked fabric is point bonded to the elastomeric layer, the resulting laminate will stretch slightly in a direction perpendicular to the direction in which the fabric was pulled during necking because the fibers of the necked fabric can slide away from each other as the laminate stretches.

Laminated material

The present invention also provides a laminate comprising one or more nonwoven fabric layers comprising bicomponent fibers as described herein.

Preferably, the laminate, if previously heated, is cooled to a temperature of less than 50 ℃, or 45 ℃, or 40 ℃, or in the range of 20 ℃ to 50 ℃. Cooling may be accomplished by any means, such as cooling air or cooling rollers. After cooling, the fabric is activated, for example by heating the laminate in a manner similar to the activation of the individual fabrics described above. In particular, the laminate may be heated, preferably in a calender roll, heated air or heated oven environment, etc., to a temperature of at least 50 ℃, or 55 ℃, or 60 ℃, or 65 ℃, or 70 ℃, or 75 ℃, or 80 ℃, or 85 ℃, or 90 ℃, or in a range from 50 ℃, or 55 ℃ to 80 ℃, or 90 ℃, or 100 ℃, or 120 ℃. More particularly, heat may be applied by any suitable method known in the art, such as heated air, infrared heaters, heated nip rolls, or partial wrapping of a fabric or laminate around one or more heated rolls or steam cans, and the like. Heat may also be applied to the grooved roll itself. It should also be understood that other grooved roll arrangements are equally suitable, such as two grooved rolls positioned directly adjacent to each other.

Yet another approach is to activate the laminate by physical treatment, modification or deformation of the laminate, the activation being performed by mechanical means. For example, the laminate may be incrementally stretched (as discussed in US 5,422,172 or US 2007/0197117) by using intermeshing rolls to make the laminate stretchable and recoverable. Finally, the film or fabric may be such that it does not require activation and is simply formed on and/or bonded to the secondary layer to form the laminate.

In some embodiments, the laminate comprises one or more secondary layers comprising other fabrics, meshes, coform fabrics, scrims, and/or films made from natural and/or synthetic materials. The material may be stretchable, elastic, or plastic in certain embodiments. In particular embodiments, the one or more minor layers comprise a material selected from the group consisting of: polypropylene, polyethylene, plastomers, polyurethanes, polyesters such as polyethylene terephthalate, polylactic acid, polyvinyl chloride, polytetrafluoroethylene, styrenic block copolymers, ethylene vinyl acetate copolymers, polyamides, polycarbonates, cellulosics (e.g., cotton, Rayon)^TM、Lyocell^TM、Tencil^TM) Wood, viscose, and blends of any two or more of these materials. Any minor layer may also comprise any material that is elasticExamples thereof include propylene-a-olefin elastomers, Natural Rubber (NR), synthetic polyisoprene (IR), butyl rubber (copolymer of isobutylene and isoprene, IIR), halogenated butyl rubber (chlorinated butyl rubber: CIIR; brominated butyl rubber: BUR), polybutadiene (BR), styrene-butadiene rubber (SBR), nitrile rubber, hydrogenated nitrile rubber, Chloroprene Rubber (CR), polychloroprene, chloroprene rubber, EPM (ethylene-propylene rubber) and EPDM rubber (ethylene-propylene-diene rubber), epichlorohydrin rubber (ECO), polyacrylic rubber (ACM, ABR), silicone rubber, fluorosilicone rubber, fluoroelastomers, perfluoroelastomers, polyether block amides (PEBA), chlorosulfonated polyethylene (CSM), ethylene Vinyl Acetate (EVA), a thermoplastic elastomer (TPE), a thermoplastic vulcanizate (TPV), a Thermoplastic Polyurethane (TPU), a thermoplastic olefin (TPO), a polysulfide rubber, or a blend of any two or more of these elastomers. In certain embodiments, the one or more elastic layers comprise a propylene-a-olefin elastomer, a styrene-butadiene rubber, or blends thereof. In yet other embodiments, the one or more elastic layers consist essentially of the propylene-a-olefin elastomer(s). In particular embodiments, a styrenic based elastomer (a polymer comprising at least 10% by weight styrene or substituted styrene derived units) is not present in the multilayer fabric.

The secondary layer(s) may take the form of a film, a fabric, or both. The film may be cast, blown or prepared by any other suitable means. When the secondary layer is a fabric, the secondary layer may be a melt-spun, dry-laid or wet-laid fabric. Dry-laid processes include mechanical means, such as how carded webs are produced, and aerodynamic means, such as air-laying processes. Drylaid nonwovens are made by staple fiber processing machinery, such as carding and filament drawing machines, which are designed to process staple fibers in the dry state. Also included in this category are nonwovens made of fibers in tow form, and fabrics composed of staple fibers and stitch bonded filaments or yarns, i.e., stitch bonded nonwovens. Fabrics made by the wet-laid process are made using machinery associated with pulp fiberization, such as hammermills and paper forming. The web bonding process may be described as a chemical process or a physical process. In any event, the dry-laid and wet-laid fabrics may be sprayed and/or hydroentangled to form hydroentangled (spunlace) fabrics as known in the art. Chemical bonding refers to the use of water-and solvent-based polymers to bond the webs together. These adhesives may be applied by saturation (dipping), spraying, printing or as a foam application. Physical bonding processes include thermal processes such as calendering and hot air bonding, and mechanical processes such as needling and hydroentangling. Spunlaid nonwoven materials are made in one continuous process: the fibers are spun by melt extrusion and then dispersed directly in the web by a directing device or may be directed by a stream of air.

In certain embodiments, the propylene-based elastomer may be formed into a coform fabric. Methods of forming such fabrics are described in, for example, US 4,818,464 and US 5,720,832. Generally, a fabric of two or more different thermoplastic and/or elastomeric materials may be formed.

Nonwoven fabrics of fibers can be used to make articles such as personal care products, baby diapers, training pants, absorbent underpads, swim wear, wipes, feminine hygiene products, bandages, wound care products, medical garments, surgical gowns, filters, adult incontinence products, surgical drapes, covers, garments, cleaning articles, and appliances.

Example embodiments

A first embodiment is a method comprising: (a) extruding a bicomponent fiber comprising: a first component comprising a first polypropylene homopolymer; and a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer; (b) cooling the bicomponent fiber; and (c) thermally and/or mechanically activating the bicomponent fibers to cause the bicomponent fibers to bend. This embodiment may optionally include one or more of the following: element 1: wherein the weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is from 10:90 to 90: 10; element 2: wherein the weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is from 40:60 to 90: 10; element 3: wherein the weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is from 10:90 to 60: 40; element 4: wherein the bicomponent fibers are heat activated by exposing the bicomponent fibers to 50 ℃ to 150 ℃ for 1 second to 5 minutes; element 5: wherein the bicomponent fibers are thermally activated by exposing the bicomponent fibers to 90 ℃ to 115 ℃ for 5 seconds to 15 seconds; element 6: wherein the bicomponent fibers are mechanically activated by exposing the bicomponent fibers to a force of from 0.01N to 10N; element 7: wherein the bicomponent fibers are mechanically activated by exposing the bicomponent fibers to a force of 0.1N to 5N; element 8: wherein the bicomponent fiber is substantially straight after cooling and has a shrinkage of at least 25% after activation; element 9: wherein the bicomponent fiber is substantially straight after cooling and has a shrinkage of at least 45% after activation; element 10: wherein the weight ratio of the first component to the second component in the bicomponent fiber is from 10:90 to 90: 10; element 11: wherein the weight ratio of the first component to the second component in the bicomponent fiber is from 40:60 to 80: 20; element 12: wherein the constituent cross-sections are side-by-side, segmented, sheath/core, or islands-in-the-sea; element 13: the method further comprises the following steps: producing a nonwoven article from bicomponent fibers; and element 14: the method further comprises the following steps: bicomponent fibers are used to produce laminate articles. Example combinations include, but are not limited to: one of elements 1-3 along with one or more of elements 4-7; one of elements 1-3 along with one of elements 8-9; one of elements 1-3 along with one of elements 10-11; one of elements 1-3 along with one or more of elements 12-14; one of elements 10-11 along with one or more of elements 4-7; one of elements 10-11 along with one of elements 8-9; one of elements 10-11 along with one or more of elements 12-14; one or more of elements 4-7 along with one of elements 8-9; one or more of elements 4-7 along with one or more of elements 12-14; and any combination of these combinations.

By "substantially straight" is meant that the fiber strand has a total bend from 180 ° of no more than ± 10 ° or ± 5 ° over its entire length. For example, there may be one, two or more bends or kinks in the strands, but generally the strands are substantially straight as defined herein.

A second embodiment is a bicomponent fiber comprising: a first component comprising a first polypropylene homopolymer; and a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer. This embodiment may optionally include one or more of the following: element 1; element 2; element 3; an element 10; an element 11; and an element 12. Example combinations include, but are not limited to: one of elements 1-3 together with one of elements 10-11 and optionally also together with element 12; one of elements 1-3 along with element 12; and one of elements 10-11 along with element 12.

A third embodiment is a nonwoven article comprising the bicomponent fiber of the second embodiment, optionally including one or more of elements 1-3 and 10-12.

A fourth embodiment is a laminate comprising the bicomponent fiber of the second embodiment, optionally including one or more of elements 1-3 and 10-12.

One or more illustrative embodiments containing embodiments of the inventions disclosed herein are set forth herein. In the interest of clarity, not all features of a physical implementation are described or shown in this application. It will be appreciated that in the development of a physical embodiment that comprises an embodiment of the present invention, numerous implementation-specific decisions must be made in order to achieve the developer's goals, such as compliance with system-related, business-related, government-related, and other constraints, which will vary from one implementation to another. While a developer's efforts might be time-consuming, such efforts would be, nevertheless, a routine undertaking for those of ordinary skill in this art having the benefit of this disclosure.

Although compositions and methods are described herein in terms of "comprising" various components or steps, the compositions and methods can also "consist essentially of" or "consist of" the various components and steps.

In order to facilitate a better understanding of embodiments of the invention, the following examples of preferred or representative embodiments are described. The following examples should in no way be construed as limiting or restricting the scope of the invention.

Examples

Example 1 bicomponent fibers were produced using side-by-side and sheath/core composition cross-sections, where the first component was a 50:50 blend of a polypropylene homopolymer having an MFR (ASTM D1238-13, 2.16kg, 230 ℃) of 36g/10min and a second component was the same polypropylene homopolymer and a polypropylene-polyethylene copolymer having an MFR (ASTM D1238-13, 2.16kg, 230 ℃) of 48g/10min (sheath/core bicomponent fibers and side-by-side bicomponent fibers). The blend had an MFR (ASTM D1238-13, 2.16kg, 230 ℃) of 45g/10 min.

Control fibers were produced consisting of a polypropylene homopolymer (monocomponent fiber) having an MFR (ASTM D1238-13, 2.16kg, 230 ℃) of 36g/10 min.

The weight ratio of the first component to the second component varies from 20:80 to 80: 20. After cooling the produced fibers, the bicomponent fibers and the control fibers were thermally activated by exposure to 100 ℃ for 15 seconds, which resulted in filament crimp. Shrinkage (ASTM D2259-02(2016)) is reported in FIG. 1.

The control filament had a shrinkage of less than 7%. However, bicomponent fibers can have almost 80% shrinkage. As the weight ratio of the first component to the second component increases, the amount of shrinkage also increases.

Example 2. FIG. 2A is a graph having 40 wt.% ExxonMobil prior to mechanical activation^TMPP3155E5 and 60% by weight of ExxonMobil produced^TM PP3155E5+Vistamaxx^TM7050, and figure 2B is a scanning electron micrograph of bicomponent fibers of a 30:70 blend, after mechanical activation by manual application of force with a brush. This illustrates the straight fibers produced and the bent fibers after activation.

Example 3. bicomponent fibers were produced using side-by-side compositional cross-sections, where the first component was a 60:40 blend of a polypropylene homopolymer having an MFR (ASTM D1238-13, 2.16kg, 230 ℃) of 36g/10min and the second component was the same polypropylene homopolymer and a polypropylene-polyethylene copolymer having an MFR (ASTM D1238-13, 2.16kg, 230 ℃) of 48g/10 min.

Fig. 3A and 3B are light micrographs of the fibers produced prior to heat activation, and fig. 3C and 3D are samples after heat activation at 100 ℃ for 15 seconds. This illustrates the straight fibers produced and the bent fibers after activation.

Example 4 bicomponent fibers were produced according to the compositions in table 1 using side-by-side composition cross-sections or sheath/core composition cross-sections. A control fiber was produced consisting of a polypropylene homopolymer having an MFR (ASTM D1238-13, 2.16kg, 230 ℃) of 36g/10 min.

TABLE 1

Example 5 three groups of fibers were produced. First, with ExxonMobil^TMThe side-by-side configuration of PP3155 and another polypropylene homopolymer produced a control fiber (PP/PP bicomponent fiber). Second, Achieve was used^TMAdvanced PP3854 as a first component and ExxonMobil^TMPP3155E5 was produced as the second component in a side-by-side configuration as a bicomponent fiber of the present invention (PP/achievee blend bicomponent fiber). Third, ExxonMobil production^TMPP3155 and Vistamaxx^TM7020 as monocomponent fibers (PP blend monocomponent fibers). Each set of fibers was produced at a different weight ratio for each component. The fibers were heat activated by exposure to 100 ℃ for 15 seconds and shrinkage was measured (see fig. 4). The bicomponent fibers of the present invention are the only samples with suitable shrinkage including up to 55%, with 70% by weight of the first component and 30% by weight of the second component.

The present invention is therefore well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein.

While compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps, the compositions and methods can also "consist essentially of" or "consist of" the various components and steps.

Claims

1. The method comprises the following steps:

extruding a bicomponent fiber comprising:

a first component comprising a first polypropylene homopolymer; and

a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer;

cooling the bicomponent fiber; and

activating the bicomponent fibers thereby causing the bicomponent fibers to buckle, wherein the step of activating is performed thermally, mechanically or by a combination of thermal and mechanical action.

2. The method of claim 1, wherein the weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is from 10:90 to 90: 10.

3. The process of any preceding claim, wherein the weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is from 40:60 to 90: 10.

4. The method of any preceding claim, wherein the bicomponent fiber is thermally activated by exposing the bicomponent fiber to 50 ℃ to 150 ℃ for 1 second to 5 minutes.

5. The process of any preceding claim, wherein the bicomponent fiber is thermally activated by exposing the bicomponent fiber to 90 ℃ to 115 ℃ for 5 seconds to 15 seconds.

6. The method according to any preceding claim, wherein the bicomponent fibers are mechanically activated by exposing the bicomponent fibers to a force of from 0.01N to 10N.

7. The method according to any preceding claim, wherein the bicomponent fibers are mechanically activated by exposing the bicomponent fibers to a force of from 0.1N to 5N.

8. The method of any preceding claim, wherein the bicomponent fiber is substantially straight after cooling and has a shrinkage of at least 25% after activation.

9. The method of any preceding claim, wherein the bicomponent fiber is substantially straight after cooling and has a shrinkage of at least 45% after activation.

10. The method of any preceding claim, wherein the weight ratio of the first component to the second component in the bicomponent fiber is from 10:90 to 90: 10.

11. The method of any preceding claim, wherein the weight ratio of the first component to the second component in the bicomponent fiber is from 40:60 to 80: 20.

12. The method of any preceding claim, wherein the compositional cross-section is side-by-side, segmented, sheath/core, or islands-in-the-sea.

13. The method of any preceding claim, further comprising producing a nonwoven article with the bicomponent fibers.

14. The method of one of claims 1-12, further comprising producing a laminate with bicomponent fibers.

15. A bicomponent fiber comprising:

a first component comprising a first polypropylene homopolymer; and

a second component comprising a blend comprising a propylene-based elastomer and a second polypropylene homopolymer, wherein the blend has a melt flow rate that is at least 20% greater or at least 20% less than the melt flow rate of the first polypropylene homopolymer.

16. The bicomponent fiber of claim 15, wherein the weight ratio of the propylene-based elastomer and the second polypropylene homopolymer in the blend is from 10:90 to 90: 10.

17. Bicomponent fiber according to one of claims 15-16, wherein the weight ratio of the first component and the second component in the bicomponent fiber is from 10:90 to 90: 10.

18. Bicomponent fiber according to one of claims 15-17, wherein the compositional cross-section is side-by-side, segmented, sheath/core, or islands-in-the-sea.

19. A nonwoven article comprising the bicomponent fiber of one of claims 15-18.

20. Laminate comprising bicomponent fibres according to one of claims 15 to 18.