CN115516144A

CN115516144A - Bicomponent fibers with improved curvature

Info

Publication number: CN115516144A
Application number: CN202180033534.2A
Authority: CN
Inventors: A·加格; 林倚剑; A·斯托伊科维奇; J·J·I·范登; F·阿特亚加拉里奥斯; R·P·帕拉卡
Original assignee: Dow Global Technologies LLC
Current assignee: Dow Global Technologies LLC
Priority date: 2020-05-08
Filing date: 2021-05-05
Publication date: 2022-12-23
Also published as: EP4146853A1; AR121943A1; BR112022022436A2; KR20230009911A; US20230272567A1; JP2023524202A; WO2021226246A1

Abstract

Bicomponent fibers having improved curvature are provided. The bicomponent fiber includes a first region and a second region. The first region comprises a first polyethylene composition and the second region comprises a second polyethylene composition, wherein the crystallization temperature (Tc) of the first polyethylene composition is greater than the crystallization temperature (Tc) of the second polyethylene composition. The bicomponent fibers can be used to form a nonwoven.

Description

Bicomponent fibers with improved curvature

Technical Field

Embodiments of the present disclosure generally relate to bicomponent fibers comprising polyethylene having improved curvature, and nonwovens comprising these fibers.

Background

Bicomponent fibers are fibers made from two different polymer compositions extruded from the same spinneret with the same filament or fiber containing both compositions. As the fiber exits the spinneret, it consists of unmixed components that melt at the interface. The two polymer compositions may differ in their chemical and/or physical properties. Bicomponent fibers can be formed by conventional spinning techniques known in the art and can be used to form nonwovens. Nonwoven fabrics have a variety of applications, such as filters, disposable materials in medical applications, and diapers. To help reduce the weight of the nonwoven or to obtain other advantageous nonwoven properties, such as loft, bicomponent fibers having curvature may be used. However, there are problems with obtaining bicomponent fibers with improved curvature and maintaining or improving other advantageous properties such as spinnability, softness, recyclability and extensibility while improving curvature.

Disclosure of Invention

Embodiments of the present disclosure provide bicomponent fibers that can be used to form nonwovens and provide unique and surprisingly high curvatures in various aspects while also maintaining or improving other properties such as spinnability, tactile softness, recyclability, and extensibility. The bicomponent fibers according to embodiments of the present disclosure each include a first region and a second region comprising a first polyethylene composition and a second polyethylene composition, respectively, which contribute to fibers having improved curvature and advantageous spinnability, softness, recyclability, and extensibility. Specifically, bicomponent fibers according to embodiments of the present disclosure comprise a first polyethylene composition and a second polyethylene composition that can improve spinnability, softness, recyclability, and extensibility, and can be interfaced to improve the inherent curvature of the fibers (e.g., the curvature of the fibers that is not the result of mechanical crimping or post-extrusion processes, such as with heated air or applied tension attenuation (attenuation)).

Disclosed herein is a bicomponent fiber. In one embodiment, the bicomponent fiber comprises a fiber centroid; a first region having a first centroid and a second region having a second centroid; the first region comprises a first polyethylene composition having a ratio expressed as weight average molecular weight to number average molecular weight (M) of less than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (a); the second zone comprises a second polyethylene composition having a density less than the density of the first polyethylene composition; wherein at least one of the first centroid and the second centroid is different than the fiber centroid; and wherein the crystallization temperature (Tc) of the first polyethylene composition is at least 2 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition.

In various embodiments, the bicomponent fiber comprises a fiber centroid; a first region having a first centroid and a second region having a second centroid; the first region comprises a first polyethylene composition having a ratio expressed as weight average molecular weight to number average molecular weight (M) greater than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (a); the second region comprises a second polyethylene composition having a density less than the density of the first polyethylene composition; wherein at least one of the first centroid and the second centroid is different than the fiber centroid; wherein the first polyethylene composition has a crystallization temperature (Tc) that is greater than the second polyethylene compositionThe ethylene composition has a crystallization temperature (Tc) at least 3.5 ℃ greater.

Also disclosed herein are nonwovens formed from the bicomponent fibers disclosed herein. For example, a spunbond nonwoven can be formed from the bicomponent fibers disclosed herein. In one embodiment, the spunbond nonwoven comprises bicomponent fibers comprising a fiber centroid; a first region having a first centroid and a second region having a second centroid; the first region comprises a first polyethylene composition having a ratio expressed as weight average molecular weight to number average molecular weight (M) of less than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (a); the second zone comprises a second polyethylene composition having a density less than the density of the first polyethylene composition; wherein at least one of the first centroid and the second centroid is different than the fiber centroid; and wherein the crystallization temperature (Tc) of the first polyethylene composition is at least 2 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition. In various embodiments, the spunbond nonwoven comprises bicomponent fibers comprising a fiber centroid; a first region having a first centroid and a second region having a second centroid; the first region comprises a first polyethylene composition having a ratio expressed as weight average molecular weight to number average molecular weight (M) greater than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (a); the second region comprises a second polyethylene composition having a density less than the density of the first polyethylene composition; wherein at least one of the first centroid and the second centroid is different than the fiber centroid; wherein the crystallization temperature (Tc) of the first polyethylene composition is at least 3.5 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition.

Additional features and advantages of the embodiments will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing and the following description describe various embodiments, and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments described herein and together with the description serve to explain the principles and operations of the claimed subject matter.

Drawings

FIG. 1 is a Scanning Electron Micrograph (SEM) cross-sectional image of a bicomponent fiber having an eccentric core-sheath configuration and a centroid shift.

Fig. 2 is a graphical representation of a single reactor stream feed data stream for producing the polyethylene compositions disclosed herein.

Fig. 3 is a graphical representation of a dual reactor stream feed data stream for producing the polyethylene compositions disclosed herein.

Detailed Description

Aspects of the disclosed bicomponent fibers are described in more detail below. Bicomponent fibers having increased curvature may be used to form nonwovens, and such nonwovens may have various applications including, for example, wipes, masks, tissues, bandages, and other medical and hygiene products. It should be noted, however, that this is merely an illustrative implementation of the embodiments disclosed herein. These embodiments are applicable to other technologies that are susceptible to similar problems as described above.

As used herein, the terms "comprising," "including," "having," and derivatives thereof, are not intended to exclude the presence of any additional component, step or procedure, whether or not the component, step or procedure is specifically disclosed. For the avoidance of any doubt, unless stated to the contrary, all compositions claimed through use of the term "comprising" may include any additional additive, adjuvant or compound, whether polymeric or otherwise. In contrast, the term "consisting essentially of 8230comprises any additional components, steps or procedures excluding any subsequently listed ranges, except for those components, steps or procedures not essential to operability. The term "consisting of 823070" excludes any ingredient, step or procedure not specifically recited or listed.

As used herein, the term "interpolymer" refers to a polymer prepared by polymerizing at least two different types of monomers. The term interpolymer thus includes copolymers (used to refer to polymers prepared from two different types of monomers) and polymers prepared from more than two different types of monomers.

As used herein, the term "polymer" means a polymeric compound prepared by polymerizing monomers of the same or different types. Thus, the generic term polymer encompasses the term homopolymer (used to refer to polymers prepared from only one type of monomer, where it is understood that trace impurities may be incorporated into the polymer structure) and the term interpolymer. Trace impurities (e.g., catalyst residues) can be incorporated into and/or within the polymer. The polymer may be a single polymer or a blend of polymers.

As used herein, the term "polyethylene composition" refers to a polymer comprising greater than 50 weight percent of units derived from ethylene monomer and optionally one or more comonomers. The polyethylene composition comprises a polyethylene homopolymer, copolymer, or interpolymer. Common forms of polyethylene compositions known in the art include Low Density Polyethylene (LDPE); linear Low Density Polyethylene (LLDPE); ultra Low Density Polyethylene (ULDPE); very Low Density Polyethylene (VLDPE); single-site catalyzed linear low density polyethylene, including linear and substantially linear low density resins (m-LLDPE); medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE).

As used herein, the terms "nonwoven," "nonwoven web," and "nonwoven fabric" are used interchangeably herein. "nonwoven" refers to a web or fabric having a structure of individual fibers or threads which are inserted randomly, rather than in an identifiable manner as in a knitted fabric.

As used herein, the term "meltblowing" refers to the manufacture of a nonwoven fabric via a process comprising the steps of: (a) Extruding molten thermoplastic strands (strand) from a spinneret; (b) Simultaneously quenching and attenuating a polymer stream immediately below a spinneret using a heated high velocity air stream; (c) The stretched strands are collected into a mesh on a collection surface. The meltblown nonwoven web may be bonded by a variety of means including, but not limited to, autogenous bonding (i.e., self bonding without further treatment), hot calendaring processes, adhesive bonding processes, hot air bonding processes, needle punching processes, hydroentangling processes, and combinations thereof.

As used herein, the term "spunbond" refers to the manufacture of a nonwoven fabric comprising the steps of: (a) Extruding molten thermoplastic strands from a plurality of fine capillaries, known as spinnerets; (b) Quenching strands comprising thermoplastic strands, such as polyethylene compositions, with a stream of air, which is typically cooled, so as to promote solidification of the molten strands of thermoplastic; (c) Advancing the filaments through a quench zone to attenuate the filaments with a drawing tension that can be applied by pneumatically entraining the filaments in a stream of air or by winding the filaments onto a mechanical draw roll of the type commonly used in the textile fiber industry; (d) Collecting the stretched strands in a mesh (e.g., a moving screen or a porous belt) on a foraminous surface; and (e) bonding the web of loose strands into the nonwoven fabric. Bonding may be accomplished in a variety of ways including, but not limited to, a thermal calendaring process, an adhesive bonding process, a hot air bonding process, a needle punching process, a hydroentangling process, and combinations thereof.

As used herein, the term "curvature" refers to the bending or curling of an individual fiber as a result of its composition, rather than as a result of any post-extrusion process (e.g., mechanical curling or thinning by heat) that may affect the bending or curling of the fiber. The amount of curvature of the bicomponent fibers disclosed herein can be measured according to the test methods described below.

Fiber

The fibers taught herein can be formed by any conventional spinning technique. For example, the first region and the second region of the bicomponent fiber can be formed into a fiber via melt spinning. In melt spinning, a first zone comprising a first polyethylene composition and a second zone comprising a second polyethylene composition may be melted, coextruded and forced through fine holes in a metal plate, known as a spinneret, into air or other gas where they are cooled and solidified, thereby forming a bicomponent fiber. The solidified fibers may be drawn off via air jets, rotating rolls, or godets (godets) and may be laid as a web on a conveyor belt for forming a nonwoven. Meltblown nonwovens may be formed that include bicomponent fibers according to embodiments of the present disclosure. In other embodiments, spunbond nonwovens may be formed comprising bicomponent fibers according to embodiments of the present disclosure.

The fibers disclosed herein have improved curvature and other advantageous properties, such as recyclability, tactile softness and extensibility due to being comprised of polyethylene. The improved curvature of the fibers disclosed herein is not a result of mechanical crimping or post-extrusion processes, such as attenuation with heated air or applied tension. The fibers in various aspects comprise all or a majority of the polyethylene composition. Nonwovens comprising polyethylene compositions are known for their tactile softness, and materials comprising polyethylene compositions are candidates for compatibility with polyethylene recycle streams.

In embodiments, the bicomponent fibers have a curvature of at least 0.50mm ^-1 . The curvature of the bicomponent fiber can be measured according to the test method described below. Disclosed herein and including at least 0.50mm ^-1 All individual values and subranges of (a). For example, in some embodiments, the curvature of the bicomponent fiber can be at least 0.50mm when measured according to the test method described below ^-1 、0.60mm ^-1 、0.70mm ^-1 Or 0.80mm ^-1 . In other embodiments, the curvature of the bicomponent fiber may be at 0.50mm when measured according to the test method described below ^-1 To 3.00mm ^-1 、0.50mm ^-1 To 2.50mm ^-1 、0.50mm ^-1 To 2.00mm ^-1 、0.50mm ^-1 To 1.50mm ^-1 、0.50mm ^-1 To 1.00mm ^-1 、1.00mm ^-1 To 3.00mm ^-1 、1.00mm ^-1 To 2.50mm ^-1 、1.00mm ^-1 To 2.00mm ^-1 、1.00mm ^-1 To 1.50mm ^-1 、1.50mm ^-1 To 3.00mm ^-1 、1.50mm ^-1 To 2.50mm ^-1 、1.50mm ^-1 To 2.00mm ^-1 、2.00mm ^-1 To 3.00mm ^-1 Or 2.00mm ^-1 To 2.50mm ^-1 Within the range.

In an embodiment, the bicomponent fiber comprises a first region and a second region, wherein the weight ratio of the first region to the second region is from 90 to 10. All individual values and subranges of the ratio of 90. For example, in embodiments, the weight ratio of the first region to the second region may be from 20 to 20, from 30 to 30.

Although the fibers taught herein are bicomponent fibers, one of ordinary skill in the art will appreciate that because both regions of the fiber contain a polyethylene composition, it may not be readily discernible from the fiber itself that the fiber includes two distinct regions. One of ordinary skill in the art will appreciate that raman microscopy and multivariate calibration as described in the test methods section below can be used to measure the percent crystallinity (%) of the individual polyethylene regions of the bicomponent fiber in situ. The difference between the raman measured crystallinity% of the two regions of the bicomponent fiber according to embodiments of the present disclosure corresponds to the improved curvature of the fiber. In embodiments, the% raman measured crystallinity of the first polyethylene composition of the first region of the bicomponent fibers is at least 5.0% greater than the% raman measured crystallinity of the second polyethylene composition of the second region of the bicomponent fibers, wherein the% raman measured crystallinity is measured according to the test method described below. All individual values and subranges from at least 5.0% greater are disclosed herein and included herein; for example, the% raman measured crystallinity of the first polyethylene composition of the first region of the bicomponent fibers can be at least 5.0% greater, at least 7.5% greater, at least 10.0% greater, or from 5.0% to 20.0% greater, from 5.0% to 15.0% greater, from 7.5% to 15.0% greater, from 10.0% to 15.0% greater, from 3.5% to 12.0% greater, from 5.0% to 12.0% greater, from 7.5% to 12.0% greater, or from 10.0% to 12.0% greater than the% raman measured crystallinity of the second polyethylene composition of the second region of the bicomponent fibers, wherein the% raman measured crystallinity is measured according to the test method described below.

Center of mass

In embodiments, the bicomponent fiber comprises a fiber centroid and a first region having a first centroid and a second region having a second centroid, wherein at least one of the first centroid and the second centroid is different than the fiber centroid.

As used herein, the term "centroid" refers to the arithmetic mean of all points of the cross-sectional area of the bicomponent fiber. For example, bicomponent fibers according to embodiments of the present disclosure have a fiber centroid, which may be designated as C _f And a region (e.g., the first region or the second region) of the bicomponent fiber has an independent centroid, which may be designated as C _rx Where x is the name of the region (e.g., the first region may be named C) _r1 And the second region may be named C _r2 ) And wherein "r" is C _f Average distance from the outer surface of the bicomponent fiber and is calculated as

Where A is the area of the cross-section of the bicomponent fiber. Figure 1 shows a bicomponent fiber and its centroid and the centroid of the second region of the bicomponent fiber. The distance from the centroid of the region to the centroid of the fiber can be defined as "P _rx ", and the centroid offset of the first or second centroid from the fiber centroid can be defined as" P _rx /r”。

In embodiments, at least one of the first centroid and the second centroid is different from the fiber centroid. Where the first centroid or the second centroid is different than the fiber centroid, the bicomponent fiber can have a different configuration, such as eccentric core-sheath, side-by-side, or segmented pie, but cannot have a concentric configuration (e.g., core-sheath concentric configuration) in which the fiber centroid, the first centroid, and the second centroid are the same. In embodiments, the first centroid of the first region and the second centroid of the second region are arranged such that the first region and the second region are in a side-by-side configuration. In other embodiments, the first centroid of the first region and the second centroid of the second region are arranged such that the first region and the second region are in a segmented pie configuration. In further embodiments, the first centroid of the first region and the second centroid of the second region are arranged such that the first region and the second region are in an eccentric core-sheath configuration, wherein the first region is a sheath of the bicomponent fiber and the second region is a core region of the bicomponent fiber and the sheath region surrounds the core region.

In embodiments, the first centroid or the second centroid is offset from the fiber centroid by at least 0.1, or at least 0.2, or at least 0.4, and less than 1 or less than 0.9, wherein the offset is measured according to the test method described below.

First zone and second zone-metallocene or single-site catalyst embodiments

In certain embodiments, the bicomponent fiber comprises a first region and a second region; the first region comprises a first polyethylene composition having a ratio expressed as weight average molecular weight to number average molecular weight (M) of less than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (a); the second region comprises a second polyethylene composition having a density less than the density of the first polyethylene composition; wherein the crystallization temperature (Tc) of the first polyethylene composition is at least 2 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition. In such embodiments, the first polyethylene composition may be formed in the presence of a metallocene or single site catalyst.

Further, in such embodiments, the first polyethylene composition has a ratio expressed as weight average molecular weight to number average molecular weight (M) of less than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (2). Molecular weight distribution (M) less than 3.0 is disclosed and included herein _w(GPC) /M _n(GPC) ) All individual values and subranges of (a); for example, in embodimentsMolecular weight distribution (M) of a polyethylene composition _w(GPC) /M _n(GPC) ) Less than 3.0, less than 2.8, less than 2.6, less than 2.4, or less than 2.2, or in the range of 1.8 to 3.0, 1.8 to 2.6, 1.8 to 2.4, 1.8 to 2.2, 2.0 to 3.0, 2.0 to 2.6, 2.0 to 2.4, 2.0 to 2.2, 2.2 to 2.6, or 2.2 to 2.4, wherein the molecular weight distribution can be expressed as the ratio of weight average molecular weight to number average molecular weight ((M) M _w(GPC) /M _n(GPC) ) And may be measured according to the test methods described below.

Further, in such embodiments, the crystallization temperature (Tc) of the first polyethylene composition is at least 2 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition. All individual values and subranges from the crystallization temperature (Tc) of the first polyethylene composition at least 2 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition; for example, the crystallization temperature (Tc) of the first polyethylene composition may be at least 2 ℃, at least 4 ℃, at least 6 ℃, at least 8 ℃, at least 10 ℃, at least 12 ℃, at least 14 ℃, at least 16 ℃, or at least 18 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition, or the difference of the crystallization temperature (Tc) of the first polyethylene composition minus the crystallization temperature (Tc) of the second polyethylene composition may be in the range of 2 ℃ to 30 ℃,2 ℃ to 25 ℃,2 ℃ to 20 ℃,2 ℃ to 15 ℃,2 ℃ to 10 ℃,2 ℃ to 5 ℃,5 ℃ to 30 ℃,5 ℃ to 25 ℃,5 ℃ to 20 ℃,5 ℃ to 15 ℃,5 ℃ to 10 ℃, 10 ℃ to 30 ℃, 10 ℃ to 25 ℃, 10 ℃ to 20 ℃, 10 ℃ to 15 ℃,15 ℃ to 30 ℃,15 ℃ to 25 ℃, or 15 ℃ to 20 ℃, wherein the crystallization temperature (Tc) may be measured according to Differential Scanning Calorimetry (DSC) as described below.

Further, in such embodiments, the melting temperature (Tm) of the first polyethylene composition may be at least 2 ℃ greater than the melting temperature (Tm) of the second polyethylene composition. All individual values and subranges from the melting temperature (Tm) of the first polyethylene composition at least 2 ℃ greater than the melting temperature (Tm) of the second polyethylene composition; for example, the melting temperature (Tm) of the first polyethylene composition can be at least 2 ℃, at least 4 ℃, at least 6 ℃, at least 8 ℃, at least 10 ℃, at least 14 ℃, at least 18 ℃, at least 22 ℃, or at least 26 ℃, or at least 30 ℃ greater than the melting temperature (Tm) of the second polyethylene composition, or the difference of the melting temperature (Tm) of the first polyethylene composition minus the melting temperature (Tm) of the second polyethylene composition may be in the range of 2 ℃ to 50 ℃,2 ℃ to 45 ℃,2 ℃ to 40 ℃,2 ℃ to 35 ℃,2 ℃ to 30 ℃,2 ℃ to 25 ℃,2 ℃ to 20 ℃,2 ℃ to 15 ℃,2 ℃ to 10 ℃,2 ℃ to 5 ℃,5 ℃ to 50 ℃,5 ℃ to 45 ℃,5 ℃ to 40 ℃,5 ℃ to 35 ℃,5 ℃ to 30 ℃,5 ℃ to 25 ℃,5 ℃ to 20 ℃,5 ℃ to 15 ℃,5 ℃ to 10 ℃, 10 ℃ to 50 ℃, 10 ℃ to 40 ℃, 10 ℃ to 30 ℃, 10 ℃ to 20 ℃, 20 ℃ to 50 ℃, 20 ℃ to 40 ℃, 20 ℃ to 30 ℃, 25 ℃ to 50 ℃, 25 ℃ to 35 ℃, 30 ℃ to 50 ℃, 30 ℃ to 40 ℃, 30 ℃ to 35 ℃, or 30 ℃ to 32 ℃, wherein the melting temperature may be measured according to DSC as described below.

Further, in such embodiments, the first polyethylene composition may have a melting temperature (Tm) of less than 130 ℃. All individual values and subranges from less than 130 ℃ are disclosed herein and included herein; for example, the first polyethylene composition can have a melting temperature (Tm) of less than 130 ℃, less than 129.8 ℃, less than 129.6 ℃, less than 129.4 ℃, less than 129.2 ℃, less than 129 ℃, or less than 128.9 ℃, wherein the melting temperature (Tm) can be measured according to DSC as described below. In embodiments, the melting temperature (Tm) of the second polyethylene composition may be less than 127 ℃. All individual values and subranges from less than 127 ℃ are disclosed herein and included herein; for example, the melting temperature (Tm) of the second polyethylene composition can be less than 127 ℃, less than 126.5 ℃, less than 125 ℃, less than 120 ℃, less than 115 ℃, less than 110 ℃, less than 105 ℃, less than 100 ℃, less than 99 ℃, less than 98.5 ℃, or less than 98 ℃, wherein the melting temperature (Tm) can be measured according to DSC as described below.

In embodiments, the difference between the melting temperature (Tm) of the first polyethylene composition minus the melting temperature (Tm) of the second polyethylene composition may be at least 1.5 ℃. All individual values and subranges from at least 1.5 ℃ are included herein and disclosed herein; for example, the difference of the melting temperature (Tm) of the first polyethylene composition minus the melting temperature (Tm) of the second polyethylene composition may be at least 1.5 ℃, at least 2.0 ℃, at least 2.5 ℃, at least 3 ℃, at least 5 ℃, at least 10 ℃, at least 15 ℃, at least 20 ℃, at least 25 ℃, or at least 30 ℃, or may be measured within the melting temperature range of 1.5 ℃ to 40 ℃, 2.0 ℃ to 40 ℃, 2.5 ℃ to 40 ℃, 1.5 ℃ to 30 ℃, 2.0 ℃ to 30 ℃, 2.5 ℃ to 30 ℃, 1.5 ℃ to 20 ℃, 2.0 ℃ to 20 ℃, 2.5 ℃ to 20 ℃, 1.5 ℃ to 10 ℃, 2.0 ℃ to 10 ℃, 2.5 ℃ to 10 ℃, 1.5 ℃ to 5 ℃, 2.0 ℃ to 5 ℃, 10 ℃ to 40 ℃, 10 ℃ to 35 ℃, 10 ℃ to 30 ℃, 10 ℃ to 20 ℃, 20 ℃ to 40 ℃, 20 ℃ to 35 ℃, 20 ℃ to 30 ℃, 25 ℃ to 40 ℃, 25 ℃ to 35 ℃, 28 ℃ to 32 ℃, or 29 ℃, wherein the Tm may be measured as follows a DSC (DSC) as follows.

First zone and second zone-Ziegler Natta catalyst embodiments

In other embodiments, the bicomponent fiber comprises a first region and a second region; the first region comprises a first polyethylene composition having a ratio expressed as weight average molecular weight to number average molecular weight (M) greater than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (a); the second region comprises a second polyethylene composition having a density less than the density of the first polyethylene composition; wherein the crystallization temperature (Tc) of the first polyethylene composition is at least 3.5 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition. In such embodiments, the first polyethylene composition may be formed in the presence of a ziegler-natta catalyst. In such embodiments, the first polyethylene composition has a ratio expressed as weight average molecular weight to number average molecular weight (M) greater than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (2). Molecular weight distributions (M) greater than 3.0 are disclosed and included herein _w(GPC) /M _n(GPC) ) All individual values and subranges of (a); for example, in embodiments, the first polyethylene composition has a molecular weight distribution (M) _w(GPC) /M _n(GPC) ) Greater than 3.0, greater than 3.02, greater than 3.04, greater than 3.06, greater than 3.08, greater than 3.10, greater than 3.12, or greater than 3.14, or between 3.0 and 5.0, 3.0 and 4.5, 3.0 and 4.0, 3.0 and 3.5, 3.0 and 3.2,3.1 to 5.0, 3.1 to 4.5, 3.1 to 4.0, 3.1 to 3.5, or 3.1 to 3.2, wherein the molecular weight distribution can be expressed as a ratio of weight average molecular weight to number average molecular weight (M) _w(GPC) /M _n(GPC) ). In such embodiments, the first polyethylene composition may be formed in the presence of a ziegler natta catalyst.

Further, in such embodiments, the crystallization temperature (Tc) of the first polyethylene composition is at least 3.5 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition. All individual values and subranges from the crystallization temperature (Tc) of the first polyethylene composition at least 3.5 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition; for example, the crystallization temperature (Tc) of the first polyethylene composition may be at least 3.5 ℃ greater, at least 4 ℃ greater, at least 4.5 ℃ greater, at least 5 ℃ greater, at least 5.5 ℃ greater, at least 6 ℃ greater, at least 6.2 ℃ greater, or at least 6.4 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition, or the difference of the crystallization temperature (Tc) of the first polyethylene composition minus the crystallization temperature (Tc) of the second polyethylene composition may be in the range of 3.5 ℃ to 15 ℃, 3.5 ℃ to 10 ℃, 3.5 ℃ to 7.5 ℃, 3.5 ℃ to 6 ℃,5 ℃ to 15 ℃,5 ℃ to 10 ℃,5 ℃ to 7.5 ℃,5 ℃ to 6 ℃,6 ℃ to 15 ℃,6 ℃ to 10 ℃,6 ℃ to 8 ℃, or 6 ℃ to 7 ℃, where (Tc) may be measured according to DSC as described below.

Further, in such embodiments, the melting temperature (Tm) of the first polyethylene composition may be at least 5 ℃ greater than the melting temperature (Tm) of the second polyethylene composition. All individual values and subranges from the melting temperature (Tm) of the first polyethylene composition at least 5 ℃ greater than the melting temperature (Tm) of the second polyethylene composition; for example, the melting temperature (Tm) of the first polyethylene composition may be at least 5 ℃, at least 5.2 ℃, at least 5.4 ℃, at least 5.6 ℃, at least 5.8 ℃, at least 6.0 ℃, at least 6.2 ℃, and at least 6.4 ℃, at least 6.6 ℃, at least 6.8 ℃, or at least 6.9 ℃ greater than the melting temperature (Tm) of the second polyethylene composition, or the difference in melting temperature (Tm) of the first polyethylene composition minus the melting temperature (Tm) of the second polyethylene composition may be measured at a DSC in the range of 5 ℃ to 10 ℃,5 ℃ to 7.5 ℃,5 ℃ to 6 ℃, 5.5 ℃ to 10 ℃, 5.5 ℃ to 7.5 ℃, 5.5 ℃ to 7 ℃, 5.5 ℃ to 6 ℃,6 ℃ to 10 ℃,6 ℃ to 7.5 ℃,6 ℃ to 7 ℃ 6.5 ℃ to 10 ℃, 6.5 ℃ to 7.5 ℃, or 6.5 ℃ to 7 ℃, where the melting temperature (Tm) may be measured as follows.

First and second regions-generally

In embodiments described herein, the second polyethylene composition has a density that is less than the density of the first polyethylene composition, wherein the density may be measured according to ASTM D792. In some embodiments, the first polyethylene composition has a density at least 0.015g/cm greater than the density of the second polyethylene composition ³ . Included and disclosed herein are at least 0.015g/cm greater ³ All individual values and subranges of (a); for example, in some embodiments, the first polyethylene composition has a density at least 0.015g/cm greater than the density of the second polyethylene composition ³ At least 0.030g/cm ³ Or at least 0.040g/cm ³ Or the difference between the density of the first polyethylene composition minus the density of the second polyethylene composition is 0.015g/cm ³ To 0.100g/cm ³ 、0.015g/cm ³ To 0.080g/cm ³ 、0.015g/cm ³ To 0.060g/cm ³ 、0.015g/cm ³ To 0.040g/cm ³ 、0.015g/cm ³ To 0.020g/cm ³ 、0.020g/cm ³ To 0.100g/cm ³ 、0.020g/cm ³ To 0.080g/cm ³ 、0.020g/cm ³ To 0.060g/cm ³ 、0.020g/cm ³ To 0.040g/cm ³ 、0.020g/cm ³ To 0.030g/cm ³ 、0.030g/cm ³ To 0.100g/cm ³ 、0.030g/cm ³ To 0.080g/cm ³ 、0.030g/cm ³ To 0.060g/cm ³ 、0.030g/cm ³ To 0.050g/cm ³ 、0.030g/cm ³ To 0.040g/cm ³ Or 0.040g/cm ³ To 0.050g/cm ³ Wherein the density can be measured according to ASTM D792.

In the embodiments described herein, the first polyethylene composition may have a density of at least 0.925g/cm ³ Wherein the density can beAs measured according to ASTM D792. Disclosed herein and included at least 0.925g/cm ³ All individual values and subranges of density within a range. For example, in some embodiments, the first polyethylene composition may have a density of at least 0.935g/cm ³ At least 0.940g/cm ³ At least 0.945g/cm ³ At least 0.950g/cm ³ At least 0.955g/cm ³ At least 0.960g/cm ³ Or at least 0.965g/cm ³ Wherein the density may be measured according to ASTM D792, or the density of the first polyethylene composition may be at 0.925g/cm ³ To 0.980g/cm ³ 、0.930g/cm ³ To 0.980g/cm ³ 、0.940g/cm ³ To 0.980g/cm ³ 、0.950g/cm ³ To 0.980g/cm ³ 、0.930g/cm ³ To 0.980g/cm ³ 、0.930g/cm ³ To 0.970g/cm ³ 、0.930g/cm ³ To 0.960g/cm ³ 、0.930g/cm ³ To 0.950g/cm ³ 、0.940g/cm ³ To 0.980g/cm ³ 、0.940g/cm ³ To 0.970g/cm ³ 、0.940g/cm ³ To 0.960g/cm ³ 、0.940g/cm ³ To 0.950g/cm ³ 、0.945g/cm ³ To 0.980g/cm ³ 、0.945g/cm ³ To 0.970g/cm ³ 、0.945g/cm ³ To 0.960g/cm ³ 、0.945g/cm ³ To 0.955g/cm ³ 、0.950g/cm ³ To 0.980g/cm ³ 、0.950g/cm ³ To 0.970g/cm ³ 、0.950g/cm ³ To 0.960g/cm ³ 、0.960g/cm ³ To 0.980g/cm ³ Or 0.960g/cm ³ To 0.980g/cm ³ Wherein the density can be measured according to ASTM D792.

In the embodiments above and described herein, the first region of bicomponent fibers comprises at least 75 weight percent of the first polyethylene composition. All individual values and subranges from at least 75 weight percent are included herein and disclosed herein; for example, the first region may comprise at least 75 wt%, at least 80 wt%, at least 85 wt%, at least 90 wt%, at least 95 wt%, or at least 75 wt% to 100 wt%, 75 wt% to 90 wt%, 75 wt% to 80 wt%, 80 wt% to 100 wt%, or 90 wt% to 100 wt% of the first polyethylene composition, wherein the weight percentages are based on the total weight of the first region.

In the embodiments above and described herein, the second region of the bicomponent fiber comprises at least 75% by weight of the second polyethylene composition. All individual values and subranges from at least 75 weight percent are included herein and disclosed herein; for example, the second region may comprise at least 75 wt%, at least 80 wt%, at least 85 wt%, at least 90 wt%, at least 95 wt%, or at least 75 wt% to 100 wt%, 75 wt% to 90 wt%, 75 wt% to 80 wt%, 80 wt% to 100 wt%, or 90 wt% to 100 wt% of the second polyethylene composition, wherein the weight percentages are based on the total weight of the second region.

In the embodiments described above and herein, the first region and/or the second region may comprise additional components, such as one or more other polymers and/or one or more additives. Other polymers may include polyesters, another polyethylene composition, propylene-based polymers (e.g., polypropylene homopolymers, propylene-ethylene copolymers, or propylene/α -olefin interpolymers), or propylene-based plastomers or elastomers. The amount of other polymer may be up to 25 wt-%, based on the total weight of the first region or the second region comprising such other polymer. For example, in embodiments, the first region and/or The second region may comprise up to 25 wt.% of a propylene-based plastomer or propylene-based elastomer (e.g., VERSIFY available from The Dow Chemical Company) ^TM Polymer and VISTA MAX available from ExxonMobil Chemical Co ^TM Polymers), low modulus and/or low molecular weight polypropylenes (e.g., L-MODU from white light (Idemitsu) ^TM Polymers), random copolymerized propylene or propylene-based olefin block copolymers (such as Intune). Potential additives include, but are not limited to, antistatic agents, color enhancers, dyes, lubricants, fillers, pigments, primary antioxidants (primary antioxidants), secondary antioxidants (secondary antioxidants), processing aids, ultraviolet stabilizers, antiblocking agents, slip agents, additives, and the like,Tackifiers, flame retardants, antimicrobials, deodorants, antifungals, and combinations thereof. The first region and/or the second region may contain from about 0.01 wt% or 0.1 wt% or 1 wt% to about 25 wt% or about 20 wt% or about 15 wt% or about 10 wt% of such additives by combined weight, based on the weight of the first region or the second region comprising such additives.

Polymerisation

Any conventional polymerization process may be employed to produce the first polyethylene composition or the second polyethylene composition. Such conventional polymerization processes include, but are not limited to, solution polymerization processes using one or more conventional reactors (e.g., parallel, series loop reactors, isothermal reactors, stirred tank reactors, batch reactors, and/or any combination thereof). Such conventional polymerization processes also include gas phase, solution or slurry polymerizations or any combination thereof using any type of reactor or reactor configuration known in the art.

In embodiments, the solution phase polymerization process is at a temperature of from 115 ℃ to 250 ℃; e.g., 155 ℃ to 225 ℃ and at a temperature in the range of 300psi to 1000psi; for example, in the range of 400psi to 750psi, in one or more well-stirred reactors, such as one or more loop reactors. In one embodiment, in a dual reactor, the temperature in the first reactor is in the range of 115 ℃ to 190 ℃ (e.g., 115 ℃ to 150 ℃) and the second reactor temperature is in the range of 150 ℃ to 200 ℃ (e.g., 170 ℃ to 195 ℃). In another embodiment, the temperature in the reactor is in the range of 115 ℃ to 250 ℃ (e.g., 155 ℃ to 225 ℃) in a single reactor. Residence times in solution phase polymerization processes are typically from 2 minutes to 30 minutes; for example in the range of 10 minutes to 20 minutes. Ethylene, solvent, one or more catalyst systems, optionally one or more co-catalysts, optionally one or more impurity scavengers, and optionally one or more comonomers are continuously fed to one or more reactors. Exemplary solvents include, but are not limited to, isoparaffins. For example, such solvents are commercially available under the name ISOPAR E from Exxon Mobil chemical, houston, tex. The resulting mixture of the first or second polyethylene composition and the solvent is then withdrawn from the reactor and the first or second polyethylene composition is isolated. The solvent is typically recovered via a solvent recovery unit (i.e., a heat exchanger and a vapor liquid separator drum) and then recycled back into the polymerization system.

In one embodiment, the first polyethylene composition or the second polyethylene composition may be produced via a solution polymerization process in a dual reactor system (e.g., a double loop reactor system), wherein ethylene and optionally one or more alpha-olefins are polymerized in the presence of one or more catalyst systems. In another embodiment, the first polyethylene composition or the second polyethylene composition may be produced in a single reactor system (e.g., a loop reactor system) via a solution polymerization process in which ethylene and optionally one or more a-olefins are polymerized in the presence of one or more catalyst systems. As noted above, in certain embodiments, the first polyethylene composition is formed in the presence of a metallocene or single site catalyst system. In other embodiments, the first polyethylene composition is formed in the presence of a ziegler-natta catalyst system.

An example of a catalyst system suitable for producing the second polyethylene composition may be a catalyst system comprising a pre-catalyst component comprising a metal-ligand complex of formula (I):

in formula (I), M is a metal selected from titanium, zirconium or hafnium, the metal having a formal oxidation state of +2, +3 or 4; n is 0, 1, or 2; when n is 1, X is a monodentate ligand or a bidentate ligand; when n is 2, each X is a monodentate ligand and is the same or different; the metal-ligand complex is electrically neutral as a whole; each Z is independently selected from-O-, -S-, -N (R) ^N ) -, or-P (R) ^P ) -, wherein each R is independently ^N And R ^P Is (C1-C3)0) A hydrocarbyl or (C1-C30) heterohydrocarbyl group; l is (C) ₁ -C ₄₀ ) Alkylene or (C) ₁ -C ₄₀ ) A heterohydrocarbylene group of which (C) ₁ -C ₄₀ ) The alkylene group has a moiety comprising a linking backbone (to which L is bonded) connecting from 1-carbon atom to 10-carbon atoms of the two Z groups in formula (I), or (C) ₁ -C ₄₀ ) The heterohydrocarbylene group has a moiety comprising a 1-atom to 10-atom linking backbone linking two Z groups of formula (I) wherein (C) ₁ -C ₄₀ ) Each of the 1-atom to 10-atom of the heterohydrocarbylene group to which each of the 1-10 atoms of the backbone is independently a carbon atom or a heteroatom, wherein each heteroatom is independently O, S (O) ₂ 、Si(R ^C ) ₂ 、Ge(R ^C ) ₂ 、P(R ^C ) Or N (R) ^C ) Wherein each R is ^C Independently is (C) ₁ -C ₃₀ ) Hydrocarbyl or (C) ₁ -C ₃₀ ) A heterohydrocarbyl group; r is ¹ And R ⁸ Independently selected from the group consisting of: -H, (C) ₁ -C ₄₀ ) Hydrocarbyl radical, (C) ₁ -C ₄₀ ) Heterohydrocarbyl, -Si (R) ^C ) ₃ 、-Ge(R ^C ) ₃ 、-P(R ^P ) ₂ 、-N(R ^N ) ₂ 、-OR ^C 、-SR ^C 、-NO ₂ 、-CN、-CF ₃ 、R ^C S(O)-、R ^C S(O) ₂ -、(R ^C ) ₂ C＝N-R ^C C(O)O-、R ^C OC(O)-、R ^C C(O)N(R ^N )-、(R ^N ) ₂ NC (O) -, halogen and a group having formula (II), formula (III) or formula (IV):

in the formulae (II), (III) and (IV), R ^31-35 、R ^41-48 Or R ^51-59 Each of (A) is independently selected from (C) ₁ -C ₄₀ ) Hydrocarbyl, (C) ₁ -C ₄₀ ) Heterohydrocarbyl, -Si (R) ^C ) ₃ 、-Ge(R ^C ) ₃ 、-P(R ^P ) ₂ 、-N(R ^N ) ₂ 、-N＝CHR ^C 、-OR ^C 、-SR ^C 、-NO ₂ 、-CN、-CF ₃ 、R ^C S(O)-、R ^C S(O) ₂ -、(R ^C ) ₂ C＝N-、R ^C C(O)O-、R ^C OC(O)-、R ^C C(O)N(R ^N )-、(R ^N ) ₂ NC (O) -, halogen or-H, with the proviso that R ¹ Or R ⁸ At least one of which is a group of formula (II), formula (III) or formula (IV), wherein R ^C 、R ^N And R ^P As defined above.

In the formula (I), R ^2-4 、R ^5-7 And R ^9-16 Each of (A) is independently selected from (C) ₁ -C ₄₀ ) Hydrocarbyl, (C) ₁ -C ₄₀ ) Heterohydrocarbyl, -Si (R) ^C ) ₃ 、-Ge(R ^C ) ₃ 、-P(R ^P ) ₂ 、-N(R ^N ) ₂ 、-N＝CHR ^C 、-OR ^C 、-SR ^C 、-NO ₂ 、-CN、-CF ₃ 、R ^C S(O)-、R ^C S(O) ₂ -、(R ^C ) ₂ C＝N-、R ^C C(O)O-、R ^C OC(O)-、R ^C C(O)N(R ^N )-、(R ^C ) ₂ NC (O) -, halogen and-H, wherein R ^C 、R ^N And R ^P As defined above.

The catalyst system comprising the metal-ligand complex of formula (I) may be rendered catalytically active by any technique known in the art for activating metal-based catalysts for olefin polymerization reactions. For example, the metal-ligand complex of formula (I) can be rendered catalytically active by contacting the complex with an activating cocatalyst or combining the complex with an activating cocatalyst. Activating cocatalysts suitable for use herein include aluminum alkyls; polymeric or oligomeric aluminoxanes (also known as aluminoxanes); a neutral lewis acid; and non-polymeric, non-coordinating, ion-forming compounds (including the use of such compounds under oxidizing conditions). A suitable activation technique is bulk electrolysis. Combinations of one or more of the foregoing activating cocatalysts and techniques are also contemplated. The term "alkylaluminum" means monoalkylaluminum dihydride or monoalkylaluminum dihalide, dialkylaluminum hydride or halide, or trialkylaluminum. Examples of the polymeric or oligomeric aluminoxane include methylaluminoxane, methylaluminoxane modified with triisobutylaluminum, and isobutylaluminoxane.

Lewis acid activators (cocatalysts) include catalysts containing 1 to 3 (C) groups as described herein ₁ -C ₂₀ ) A hydrocarbyl-substituted group 13 metal compound. An example of the group 13 metal compound is tris ((C) ₁ -C ₂₀ ) Hydrocarbyl-substituted aluminium or tris ((C) ₁ -C ₂₀ ) Hydrocarbyl) -boron compounds; tri (hydrocarbyl) substituted aluminum, tri ((C) ₁ -C ₂₀ ) Hydrocarbyl) -boron compounds; three ((C) ₁ -C ₁₀ ) Alkyl) aluminum, tris ((C) ₆ -C ₁₈ ) Aryl) boron compounds; and halogenated (including perhalogenated) derivatives thereof. In further examples, the group 13 metal compound is tris (fluoro substituted phenyl) borane, tris (pentafluorophenyl) borane. The activating cocatalyst can be tri ((C) ₁ -C ₂₀ ) Hydrocarbyl borates (e.g. trityl tetrafluoroborate) or tris ((C) ₁ -C ₂₀ ) Hydrocarbyl-tetra ((C) ₁ -C ₂₀ ) Hydrocarbyl) boranamines (e.g., bis (octadecyl) methyltetrakis (pentafluorophenyl) boranaminium). As used herein, the term "ammonium" means a nitrogen cation which is ((C) ₁ -C ₂₀ ) Alkyl radical) ₄ N ⁺ 、((C ₁ -C ₂₀ ) Alkyl radical) ₃ N(H) ⁺ 、((C ₁ -C ₂₀ ) Alkyl radical) ₂ N(H) ₂ ⁺ 、(C ₁ -C ₂₀ ) Alkyl radicals N (H) ₃ ⁺ Or N (H) ₄ ⁺ Wherein two or more (C) are present ₁ -C ₂₀ ) When the hydrocarbon groups are used, they may be the same or different.

The combination of neutral Lewis acid activators (cocatalysts) comprises a compound comprising three ((C) ₁ -C ₄ ) Alkyl) aluminum and tris ((C) halide ₆ -C ₁₈ ) Aryl) boron compounds, especially tris (pentafluorophenyl) borane; or a combination of such a mixture of neutral lewis acids with a polymeric or oligomeric aluminoxane, as well as a combination of a single neutral lewis acid, especially tris (pentafluorophenyl) borane, with a polymeric or oligomeric aluminoxane. (Metal-ligand Complex) (tris (pentafluorophenyl) compoundBoranes (aluminoxanes) [ e.g., (group 4 metal-ligand complexes): tris (pentafluorophenyl borane): aluminoxane]1.

The metal-ligand complex catalyst system comprising formula (I) can be activated to form an active catalyst composition by combination with one or more cocatalysts (e.g., a cation forming cocatalyst, a strong lewis acid, or a combination thereof). Suitable activating cocatalysts include polymeric or oligomeric aluminoxanes, especially methylaluminoxane, as well as inert, compatible, noncoordinating, ion forming compounds. Exemplary suitable cocatalysts include, but are not limited to: modified Methylaluminoxane (MMAO) bis (hydrogenated tallow alkyl) methyltetrakis (pentafluorophenyl) borate (1) ^- ) Amines, and combinations thereof.

One or more of the foregoing activating cocatalysts may be used in combination with each other. A preferred combination is tris ((C) ₁ -C ₄ ) Hydrocarbyl aluminum, tris ((C) ₁ -C ₄ ) Hydrocarbyl) borane or ammonium borate with oligomeric or polymeric aluminoxane compounds. The ratio of the total moles of the one or more metal-ligand complexes of formula (I) to the total moles of the one or more activating cocatalysts of the activating cocatalysts is from 1, 10,000 to 100. The ratio may be at least 1; and may not exceed 10. When aluminoxane is used alone as the activating cocatalyst, the number of moles of aluminoxane employed is preferably at least 100 times the number of moles of the metal-ligand complex of formula (I). When tris (pentafluorophenyl) borane is used alone as the activating cocatalyst, the ratio of moles of tris (pentafluorophenyl) borane employed to the total moles of the one or more metal-ligand complexes of formula (I) can be from 0.5. The remaining activating cocatalyst is generally employed in a molar amount approximately equal to the total molar amount of the one or more metal-ligand complexes of formula (I).

Test method

Density of

Density is measured according to ASTM D792, and is in grams/cm ³ (g/cm ³ ) And (4) showing.

Melt index (I2)

Melt index (I2) was measured according to ASTM D1238 at 190 degrees Celsius (. Degree.C.) and 2.16kg and is expressed as grams eluted per 10 minutes (g/10 min).

Curvature

The amount of curvature was measured via an optical microscope. The amount of curvature is calculated based on the inverse of the radius of the helix formed by the fibers. This is equal to the radius of the circle formed by the projection of the helix formed by the fiber on the surface perpendicular thereto. The average of at least 5 measurements is reported. The measurement is in 1/millimeter (mm) ^-1 ) Reported in units.

Center of mass shift

Fibers were embedded in epoxy and polished at low temperature for AFM analysis using a Leica UCT/FCS microtome operating at-140 ℃. Topography and phase images were captured at ambient temperature by using a Bruker Icon AFM system with a MikroMasch probe. The probe has a spring constant of 40N/m and a resonant frequency above and below 170 kHz. An imaging frequency of 0.5Hz-2Hz and a set point ratio of about 0.8 are used. The diameter of the fiber cross-section was measured using a single cord and this measurement was divided in half to mark the midpoint as the fiber centroid (Cf). The core region of the bicomponent fiber is divided with two cords at 90 ° to create four quadrants of the equal region visually, and the intersection of the two cords defines the centroid (Cr 2) of the core region. The distance between the fiber centroid (Cf) and the centroid (Cr 2) of the core region is measured and then divided by the radius of the fiber to calculate the fiber centroid shift (Pr 2/r).

Conventional GPC (Mw/Mn)

Conventional GPC was obtained by high temperature Gel Permeation Chromatography (GPC) equipment (PolymerChar, spain). An IR5 detector ("measurement channel") is used as a concentration detector. The GPCOne software (Polymer char, spain) was used to calculate the weight average molecular weight (Mw) and number average molecular weight (Mn) of the polymer and determine the molecular weight distribution (Mw/Mn). The method used three 10 micron PL gel mixed B columns (Agilent Technologies, column size 100mm x 7.6 mm) or four 20 micron PL gel mixed a columns (Agilent Technologies, column size 100mm x 7.6 mm) operating at a system temperature of 150 ℃. A sample having a concentration of 2mg/mL was prepared by an autosampler (PolymerChar, spain) in a 1,2, 4-trichlorobenzene solvent containing 200 percent of antioxidant Butylated Hydroxytoluene (BHT) at 160 ℃ under gentle shaking for 3 hours. The flow rate was 1.0mL/min and the injection size was 200. Mu.l. GPCOne software was used to calculate plate counts. The chromatography system must have at least 22,000 plates.

The GPC column set was calibrated by running at least 20 narrow molecular weight distribution polystyrene standards. Calibration uses a third order fit for a system with three 10 micron PL gel-mixed B columns, or a fifth order fit for a system with four 20 micron PL gel-mixed a columns. The Molecular Weight (MW) of the standards ranged from 580g/mol to 8,400,000g/mol, and the standards were included in 6 "cocktail" mixtures. Each standard mixture has approximately ten degrees of separation between the individual molecular weights. These standard mixtures were purchased from agilent technologies. The polystyrene standard was prepared under the following conditions: for molecular weights equal to or greater than 1,000,000g/mol, 0.025g in 50mL solvent, and for molecular weights less than 1,000,000g/mol, 0.05g in 50mL solvent. The polystyrene standards were dissolved at 80 ℃ for 30 minutes with gentle stirring. Narrow standard mixtures were run first, and the descending order of highest molecular weight components was followed to minimize degradation. The peak molecular weight of polystyrene standards was converted to polyethylene molecular weight using equation (1) (as described in Williams and Ward, journal of polymer science (j.polymer.sci.), polymer letters, 6,621 (1968)):

MW _PE ＝A×(MW _PS ) B (equation 1)

Where MW is the molecular weight of the labeled Polyethylene (PE) or Polystyrene (PS) and B is equal to 1.0. As known to those of ordinary skill in the art, a can be in the range of about 0.38 to about 0.44, such that an a value produces 52,000mwpe for Standard Reference Material (SRM) 1475 a. The use of this polyethylene calibration method to obtain molecular weight values, such as molecular weight distribution (MWD or Mw/Mn), and associated statistics, is defined herein as a modified williams and wadd method. The number average molecular weight, weight average molecular weight and z average molecular weight are calculated by the following equations.

M _n,cc ＝∑w _i /∑(w _i /M _cc,i ) (equation 2)

M _w,cc ＝∑w _i M _cc,i (equation 3)

Wherein M is _n,cc 、M _w,cc And M _z,cc (in g/mol) are the number average molecular weight, weight average molecular weight and z average molecular weight, respectively, obtained from conventional calibration. W _i Is in the retention volume V _i Weight fraction of polyethylene molecules eluted. M is a group of _cc,i Is obtained using conventional calibration at a retention volume V _i Molecular weight of polyethylene molecules eluted below (in g/mol) (see equation (1)).

When looking at the chromatogram at 20% peak height, the chromatogram peaks should be set to include regions where the markers significantly deviated from the baseline. The baseline integral should not be less than 100 polyethylene equivalent molecular weight and the mismatch of the antioxidant with the prepared sample and chromatographic mobile phase must be carefully handled.

The use of decane flow marker is shown in the IR5 chromatogram. The baseline (response) Y value difference between baseline start and end points should not be greater than 3% of the integrated peak height of the chromatogram at any time. In this case, the chromatographic sample must be processed by appropriately matching the sample and the mobile phase antioxidant.

w (greater than 10) ⁵ Weight fraction of g/mol) according to equation (5) according to the MWD curve (w) obtained from the GPCOne software _i For log M _cc,i ) Computing

Differential Scanning Calorimetry (DSC)

DSC is used to measure the melting temperature (Tm) and crystallization temperature (Tc) characteristics of polymers over a wide range of temperatures. This analysis is performed, for example, using a TA instrument (TA Instruments) Q1000 DSC equipped with an RCS (refrigerated cooling system) and an autosampler. During the test, a nitrogen purge flow of 50ml/min was used. Melt pressing each sample into a film at about 175 ℃; the molten sample was then air cooled to room temperature (about 25 ℃). The film samples were formed by pressing the "0.1 to 0.2 gram" samples at 175 ℃ at 1,500psi for 30 seconds to form "0.1 to 0.2 mil thick" films. A3 mg to 10mg, 6mm diameter sample was extracted from the cooled polymer, weighed, placed in a light aluminum pan (about 50 mg), and capped. Analysis is then performed to determine its thermal properties.

The thermal behavior of the sample is determined by ramping the sample temperature up and down to produce a heat flow versus temperature curve. First, the sample was rapidly heated to 180 ℃ and isothermally held for five minutes to remove its thermal history. Next, the sample was cooled to-40 ℃ at a cooling rate of 10 ℃/min and isothermally held at-40 ℃ for five minutes. The sample was then heated to 150 deg.C (this is a "second heat" ramp) at a heating rate of 10 deg.C/min. The cooling curve and the second heating curve were recorded. The cooling curve was analyzed by setting the baseline end point from the start of crystallization to-20 ℃. The heating curve was analyzed by setting a baseline end point from-20 ℃ to the end of melting. The measured value is the maximum peak melting temperature (T) _m ) (referred to herein as the melting temperature (Tm)), the highest peak crystallization temperature (Tc) (referred to herein as the "crystallization temperature (Tc)"), the heat of fusion (H) _f ) (in joules/gram) and% crystallinity of the polyethylene sample calculated using the following equation: crystallinity% = ((H) _f ) /(292J/g)). Times.100. Heat of fusion (H) reported from second heating curve _f ) And melting temperature (Tm). The crystallization temperature (Tc) was determined from the cooling curve.

Raman microscopy

Raman microscopy and multivariate calibration were used to measure in situ the% crystallinity of the individual polyethylene regions of the bicomponent fiber. Raman microscopy, a type of vibrational spectroscopy technique, is sensitive to vibrations of the polymer backbone and can provide information about both the amorphous and crystalline phases of the polymer and polyethylene compositions. Raman can use visible or near-infrared radiation and when coupled with an optical microscope provides a lateral spatial resolution of about 0.8 to 1.2 microns (depending on the excitation laser and microscope objective used).

A Partial Least Squares (PLS) model was constructed to correlate raman data with annealed base resin density and percent (%) crystallinity calculated from annealed polyethylene composition density. Annealed densities were measured according to ASTM D792. The percent (%) crystallinity was calculated from the measured annealed density using the following equation (equation 6):

wherein: ρ is a unit of a gradient _a =0.855g/cc (100% amorphous) and ρ _c Density of 1.000g/cc (100% crystalline).

Polarized raman spectra were collected using an equivalent Thermo Scientific DXR2 micro-raman instrument. Raman spectra were collected using 900 grooves/mm grating. Spectral range covering 50cm ^-1 To 3500cm ^-1 And the data interval is 0.964cm ^-1 . Other data acquisition parameters are as follows. Collecting time: 3-10 seconds; collecting times: 3 times to 6 times; dark current subtraction, cosmic ray filter, and white light correction: and (4) opening. Calibration data were recorded with an Olympus M PlanN 20x (0.40 NA) objective using a 25 micron slit and an Olympus M PlanN 100x (0.90 NA) objective using a 50 micron pinhole.

Twenty-eight density ranges of 0.859g/cm ³ -0.964g/cm ³ The polyethylene composition resin of (a) was used for calibration and cross validation of the PLS model. The PLS model was also validated using a separate set of density patches and then used to measure the resin crystallinity of the resin for the regions of bicomponent fiber. The PLS model is based on TQ analysis ^TM Software, use the followingThe parameters are constructed as follows: spectral region: 1571cm ^-1 To 971cm ^-1 (ii) a Normalization: integration region 1356cm ^-1 -1227cm ^-1 -the same baseline point; total number of samples: 28; number of calibration standards: 26; independent cross-validation sample number: 2; independently verifying the sample number: 6; data preprocessing for: annealed base resin density model and calculated% crystallinity model-average centering, derivative of order 2, SG smoothing (15 points, 3 level polynomial); the number of factors for calibration of both models: annealed base resin density and calculated% crystallinity =4.

After validation of the PLS model, a longitudinal (parallel to the direction of stretching) cross-section of each bicomponent fiber example was prepared. The cross-section is oriented on the sample stage such that the drawing direction of the fibers is oriented on the sample stage in the east-west direction. Depolarized raman spectra were acquired in three different locations for each region of the bicomponent fiber example using a 100x (0.9 NA) objective and a 25 micron pinhole. The resulting raman spectra from each region were averaged and the averaged spectra were used to measure% region crystallinity using the PLS model.

Examples

Synthesis of polyethylene composition

The development resins ("resin 1", "resin 2", "resin 3" and "resin 4") were prepared according to the following methods and tables.

All of the feed (monomer and comonomer) and process solvents (narrow boiling range high purity isoparaffin solvents, isopar-E) are purified with molecular sieves prior to introduction into the reaction environment. Hydrogen is supplied pressurized at high purity levels and without further purification. The reactor monomer feed stream is pressurized via a mechanical compressor to greater than the reaction pressure. The solvent and comonomer (if present) feeds are pressurized via pumps to above the reaction pressure. The individual catalyst components are manually batch diluted with the purification solvent and pressurized above the reaction pressure. All reaction feed streams were measured with mass flow meters and independently controlled with a computer automated valve control system.

The reactor configuration was either single reactor operation or dual series reactor operation as specified in table 2.

A single reactor system or two reactor systems in a series configuration are used. Each reactor is a continuous solution polymerization reactor consisting of a liquid-filled, non-adiabatic, isothermal, circulating loop reactor that simulates a Continuous Stirred Tank Reactor (CSTR) with heat removal. All fresh solvent, monomer, comonomer (if present), hydrogen and catalyst component feeds can be independently controlled. The temperature of the total fresh feed streams (solvent, monomer, comonomer if present, and hydrogen) to each reactor is typically controlled between 15 ℃ and 50 ℃ by passing the feed streams through a heat exchanger to maintain a single solution phase. The total fresh feed to each polymerization reactor was injected into the reactor at two locations with approximately equal reactor volumes between each injection location. Fresh feed was controlled with each injector receiving half of the total fresh feed mass flow. The catalyst components are injected into the polymerization reactor through an injection nozzle to introduce these components into the center of the reactor stream. The computer controls the main catalyst component feed to maintain the reactor monomer conversion at the specified value. The co-catalyst component is fed based on the calculated specified molar ratio to the main catalyst component. Immediately following each reactor feed injection location, the feed stream is mixed with the circulating polymerization reactor contents using static mixing elements. The contents of each reactor are continuously circulated through a heat exchanger responsible for removing most of the heat of reaction, and wherein the temperature of the coolant side is responsible for maintaining the isothermal reaction environment at the specified temperature. Circulation around each reactor loop is provided by a pump.

In a dual series reactor configuration, the effluent from the first polymerization reactor (containing solvent, monomer, comonomer if present, hydrogen, catalyst components, and polymer) leaves the first reactor loop and is added to the second reactor loop.

In all reactor configurations, the final reactor effluent (either the second reactor effluent in a double series or the single reactor effluent) enters a zone where a suitable reagent (water) is added and reacted with to deactivate the final reactor effluent. At this same reactor outlet position, other additives are added for polymer stabilization.

After catalyst deactivation and addition of additives, the reactor effluent enters a devolatilization system where the polymer is removed from the non-polymer stream. The separated polymer melt was pelletized and collected. The non-polymer stream is passed through various devices that separate most of the ethylene removed from the system. Most of the solvent and unreacted comonomer (if present) is recycled back to the reactor after passing through the purification system. Small amounts of solvent and comonomer (if present) are purged from the process.

The reactor stream feed data streams corresponding to the values in table 2 for the production of the developed resins are depicted graphically in fig. 2 and 3. The data are presented so that the complexity of the solvent recycling system is taken into account and the reaction system can be handled more simply as an once-through flow diagram (once through flow diagram).

TABLE 1 catalyst Components

TABLE 2 production conditions

The following materials were used in the examples.

Polymer 1 (poly.1) is resin 1 described above.

Polymer 2 (Poly.2) is ASPUN ^TM 6835, a commercially available from The Dow Chemical Company (Midland, mich.) of Midland, michThe obtained polyethylene composition and linear low-density polyethylene fiber resin.

Polymer 3 (poly.3) is resin 2 described above.

Polymer 4 (poly.4) is resin 3 described above.

Polymer 5 (poly.5) is resin 4 described above.

Polymer 6 (Poly.6) is ELITE ^TM 5860, a polyethylene composition and reinforced polyethylene resin commercially available from Dow chemical company of Midland, mich.

The densities, melt indices (I2), molecular weight distributions (Mw/Mn), crystallization temperatures (Tc), and melting temperatures (Tm) of polymers 1 through 6 are reported in table 3 below.

TABLE 3 characteristics of Polymer 1 to Polymer 6

Polymer and method of making same	Density (g/cm) ³ )	Melt index (I2)	Mw/Mn	Tc(℃)	Tm(℃)
						Polymer 1	0.950	19.0	2.170	114.50	128.81
Polymer 2	0.950	17.0	3.750	115.00	127.35
						Polymer 3	0.968	35.0	3.144	118.23	133.18
Polymer 4	0.935	17.0	2.300	113.20	127.45
						Polymer 5	0.935	21.0	2.300	111.80	126.21
Polymer 6	0.907	25.0	2.800	96.32	97.86

Fiber formation

The fibers were spun on a Hills bicomponent continuous filament fiber spinning line. Bicomponent fibers are made having an eccentric core-sheath configuration. The fibers were spun on a Hills line according to the following conditions. The profile of the extruder was adjusted to achieve a melt temperature of 240 ℃. The throughput per well was 0.5ghm (grams per minute per hour). A Hills two-component die was used and operated at a 40/60 core/sheath ratio (by weight) to form inventive examples 1,2, 3 and 4, and comparative examples 1,2, 3, 4, 5 and 6, with the first zone comprising an example in one extruder and the second zone comprising another example in another extruder, according to table 4 below. The Hills line pressure was set to 40psi. The die consisted of 144 holes with a diameter of 0.6mm and a length/diameter (L/D) of 4/1. The quench air temperature and flow rate were set at 15 deg.C to 18 deg.C and 520cfm (cubic feet per minute), respectively. After the quench zone, a drawing tension was applied to 144 filaments by pneumatically entraining the filaments with a stream of air in a slot unit. The velocity of the air stream is controlled by the slot aspirator pressure.

TABLE 4 fiber examples

Table 5 provides the melting temperature difference (Δ Tm), crystallization temperature difference (Δ Tc), and density difference (Δ density) for the first zone minus the second zone for examples 1 and 2 of the present invention and comparative examples 1 and 2, which examples have a polyethylene composition in the first zone having a molecular weight distribution (Mw/Mn) of less than 3.

TABLE 5 Δ Tm, Δ density, Δ Tc data

Table 6 provides the melting temperature difference (Δ Tm), crystallization temperature difference (Δ Tc), and density difference (Δ density) for the first zone minus the second zone for examples 3 and 4 of the present invention, and comparative examples 3, 4, and 5, which have a molecular weight distribution (Mw/Mn) of the polyethylene composition in the first zone of greater than 3.

TABLE 6 Δ TM, Δ Density and Δ Tc data

Examples	ΔTm	ΔTc	Delta density
				Inventive example 3	6.97	6.43	0.033
Inventive example 4	5.73	5.03	0.033
				Comparative example 3	1.14	3.20	0.015
Comparative example4	-0.10	1.80	0.015
				Comparative example 5	5.83	3.23	0.018
Comparative example 6	0	0	0

Some of the inventive and comparative examples were tested for% crystallinity according to the raman microscopy test method described above. Table 7 shows the results.

Table 7-crystallinity from raman microscope%

Table 8 shows the amount of curvature associated with the examples. Inventive examples 1 to 4 had significantly higher curvatures than comparative examples without curvatures.

TABLE 8 curvature data

Table 9 provides the centroid shift and fiber radius data for certain embodiments.

TABLE 9 fiber radius and centroid migration

Claims

1. A bicomponent fiber comprising:

a fiber centroid;

a first region having a first centroid and a second region having a second centroid;

the first zone comprises a first polyethylene composition having a ratio expressed as weight average molecular weight to number average molecular weight (M) of less than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (a);

the second region comprises a second polyethylene composition having a density less than the density of the first polyethylene composition;

wherein at least one of the first centroid and the second centroid is different than the fiber centroid; and is

Wherein the crystallization temperature (Tc) of the first polyethylene composition is at least 2 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition.

2. The bicomponent fiber of claim 1, wherein the melting temperature (Tm) of the first polyethylene composition is at least 2 ℃ greater than the melting temperature (Tm) of the second polyethylene composition.

3. The bicomponent fiber of claims 1-2, wherein the melting temperature (Tm) of the first polyethylene composition is less than 130 ℃.

4. A bicomponent fiber, comprising:

a fiber centroid;

the first region comprises a first polyethylene composition having a ratio expressed as weight average molecular weight to number average molecular weight (M) greater than 3.0 _w(GPC) /M _n(GPC) ) Molecular weight distribution of (a);

the second zone comprises a second polyethylene composition having a density less than the density of the first polyethylene composition;

wherein at least one of the first centroid and the second centroid is different than the fiber centroid;

wherein the crystallization temperature (Tc) of the first polyethylene composition is at least 3.5 ℃ greater than the crystallization temperature (Tc) of the second polyethylene composition.

5. The bicomponent fiber of claim 4, wherein the melting temperature (Tm) of the first polyethylene composition is at least 5 ℃ greater than the melting temperature (Tm) of the second polyethylene composition.

6. The bicomponent fiber of claims 1 to 5, wherein the first polyethylene composition has a density at least 0.015g/cm greater than the density of the second polyethylene composition ³ 。

7. Bicomponent fiber according to claims 1 to 6, wherein the curvature of the fiber is greater than 0.5mm ^-1 。

8. The bicomponent fiber of claims 1 to 7, wherein the first polyethylene composition has a% Raman measured crystallinity at least 5.00% greater than the% Raman measured crystallinity of the second polyethylene composition.

9. A spunbond nonwoven comprising the bicomponent fibers of claims 1-8.