KR20230009911A - Bicomponent fibers with improved curvature - Google Patents

Abstract

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

Description

Bicomponent fibers with improved curvature

Embodiments of the present disclosure relate generally to bicomponent fibers having curvature, comprising ethylene, and to nonwoven fabrics comprising such fibers.

Bicomponent fibers are fibers composed of two different polymer compositions extruded from the same spinneret and contained in the same filament or fiber. As the fibers leave the spinneret, they are composed of unmixed components that fuse at the interface. The two polymer compositions may have different chemical and/or physical properties. Bicomponent fibers may be formed by conventional spinning techniques known in the art and may be used to form nonwoven fabrics. Nonwoven fabrics have a variety of uses, such as filters, disposable materials for medical use, and diaper raw materials. Bicomponent fibers with curvature may be used to help reduce nonwoven weight or to help obtain other beneficial properties of the nonwoven, such as loft. However, problems exist in obtaining bicomponent fibers with improved curvature and improving the curvature while maintaining or enhancing other advantageous properties such as spinnability, softness, recyclability, and extensibility.

Embodiments of the present disclosure can be used to form nonwoven fabrics, which in many respects provide a unique and surprisingly high curvature, while maintaining or improving other properties such as stretchability, tactile softness, recyclability, and stretchability. Provides minute fibers. Each bicomponent fiber according to embodiments of the present disclosure comprises a first polyethylene composition and a second polyethylene composition, respectively, that contribute to the fiber having improved curvature and advantageous spinning, softness, recyclability, and extensibility. It includes a first polymer region and a second polymer region. Specifically, bicomponent fibers according to embodiments of the present disclosure are capable of improving spinability, softness, recyclability, and extensibility, and the natural curvature of the fiber (eg, attenuation by heated air or a first polyethylene composition and a second polyethylene composition, wherein the first polyethylene composition and the second polyethylene composition are capable of interacting to enhance fiber curvature (not as a result of mechanical crimping or post-extrusion processes such as tension application).

Bicomponent fibers are disclosed herein. In one embodiment, the bicomponent fibers have a fiber core; It includes a first region having a first center and a second region having a second center, wherein the first region is expressed as a ratio of weight average molecular weight to number average molecular weight (M _{w (GPC)} /M _{n (GPC)} ) a first polyethylene composition having a molecular weight distribution of less than 3.0; the second region comprises a second polyethylene composition having a density lower than the density of the first polyethylene composition; at least one of the first center and the second center is not identical to the fiber center; The first polyethylene composition has a crystallization temperature (Tc) that is at least 2° C. higher than the crystallization temperature (Tc) of the second polyethylene composition.

In another embodiment, the bicomponent fiber comprises a fiber center, a first region having a first center and a second region having a second center, the first region having a ratio of weight average molecular weight to number average molecular weight ( a first polyethylene composition having a molecular weight distribution expressed as M _{w (GPC)} /M _{n (GPC)} ) greater than 3.0; the second region comprises a second polyethylene composition having a density lower than the density of the first polyethylene composition; at least one of the first center and the second center is not identical to the fiber center; The first polyethylene composition has a crystallization temperature (Tc) that is at least 3.5° C. higher than the crystallization temperature (Tc) of the second polyethylene composition.

Also disclosed are nonwoven fabrics formed from the bicomponent fibers disclosed herein. For example, spunbond nonwovens can be formed from the bicomponent fibers disclosed herein. In one embodiment, the spunbond nonwoven fabric includes bicomponent fibers, wherein the bicomponent fibers have a fiber core; It includes a first region having a first center and a second region having a second center, wherein the first region is expressed as a ratio of weight average molecular weight to number average molecular weight (M _{w (GPC)} /M _{n (GPC)} ) a first polyethylene composition having a molecular weight distribution of less than 3.0; the second region comprises a second polyethylene composition having a density lower than the density of the first polyethylene composition; at least one of the first center and the second center is not identical to the fiber center; The first polyethylene composition has a crystallization temperature (Tc) that is at least 2° C. higher than the crystallization temperature (Tc) of the second polyethylene composition. In another embodiment, the spunbond nonwoven fabric includes bicomponent fibers, wherein the bicomponent fibers have a fiber core; It includes a first region having a first center and a second region having a second center, wherein the first region is expressed as a ratio of weight average molecular weight to number average molecular weight (M _{w (GPC)} /M _{n (GPC)} ) a first polyethylene composition having a molecular weight distribution greater than 3.0; the second region comprises a second polyethylene composition having a density lower than the density of the first polyethylene composition; at least one of the first center and the second center is not identical to the fiber center; The first polyethylene composition has a crystallization temperature (Tc) that is at least 3.5° C. higher than the crystallization temperature (Tc) of the second polyethylene composition.

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

It is to be understood that both the foregoing and following descriptions describe various embodiments and are intended to provide an overview or framework for understanding the nature and nature 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 principle and operation of the claimed subject matter.

1 is a scanning electron micrograph (SEM) cross-sectional image of a bicomponent fiber with an eccentric core-sheath shape and center offset.
2 is an illustration of a single reactor stream feed data flow used to make a polyethylene composition disclosed herein.
3 is an illustration of a dual reactor stream feed data flow used to produce a polyethylene composition disclosed herein.

Embodiments of the disclosed bicomponent fibers will be described in more detail below. Bicomponent fibers with increased curvature can be used to form nonwoven fabrics, which can have a wide variety of uses including, for example, wipes, face masks, tissues, bandages, and other medical and hygiene products. . However, it should be noted that this is merely an exemplary implementation of the embodiments disclosed herein. The above embodiments are also applicable to other technologies susceptible to problems similar to those described above.

As used herein, the terms "comprising, including", "having", and derivatives thereof, refer to whether or not the presence of any additional component, step, or procedure is specifically disclosed. It is not intended to exclude the presence of any additional component, step, or procedure without For the avoidance of doubt, all compositions claimed through use of the term "comprising" may include any additional additive, adjuvant, or compound, whether polymeric or not, unless otherwise specified. . In contrast, the term “consisting essentially of” excludes from the scope of any subsequent recitation any other component, step, or procedure, excepting those not essential to operability. The term "consisting of" excludes any component, step, or procedure not specifically delineated or listed.

As used herein, the term “interpolymer” refers to a polymer prepared by polymerization of at least two different types of monomers. Thus, the term interpolymer includes copolymers (used to refer to polymers made from two different types of monomers) and polymers made from more than two different types of monomers.

As used herein, the term “polymer” refers to a polymerizable compound prepared by polymerizing monomers of the same or different type. Thus, the generic term polymer encompasses the term homopolymer (used to refer to a polymer made from only one type of monomer, with the understanding that trace amounts of impurities may be incorporated into the polymer structure), and the term interpolymer. Trace amounts of impurities (eg, catalyst residues) may be incorporated into and/or present 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% by weight of units derived from ethylene monomers and optionally one or more comonomers. Polyethylene compositions include polyethylene homopolymers, copolymers, or interpolymers. Common types 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 both 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 fabric” and “nonwoven web” are used interchangeably herein. “Non-woven fabric” refers to a web or fabric having a structure of individual fibers or yarns that are randomly but overlapping in a non-identifiable manner as in the case of a knitted fabric.

칭 및 감쇠시키는 단계; (c) 인발된 스트랜드를 수집 표면에 웹의 형태로 수집하는 단계. 용융 취입 부직포는 자가 접합(즉, 추가 처리가 없는 자체 접합), 열-캘린더링 공정, 접착제 접합 공정, 열풍 접합 공정, 니들 펀치 공정, 하이드로인탱글링 공정, 및 이들의 조합을 포함하지만 이에 제한되지 않는 다양한 수단에 의해 접합될 수 있다.As used herein, the term "meltblown" refers to the manufacture of a nonwoven fabric through a process comprising the steps of: (a) extruding a molten thermoplastic strand from a spinneret; (b) a stream of polymer simultaneously under the spinneret using a high-velocity heated air stream;

quenching and damping; (c) collecting the drawn strands in the form of a web on a collecting surface. Melt blown nonwovens include, but are not limited to, self bonding (i.e., self bonding without additional treatment), heat-calendering process, adhesive bonding process, hot air bonding process, needle punch process, hydroentangling process, and combinations thereof. It can be bonded by various means.

칭하는 단계; (c) 필라멘트를 공기류에 공압으로 동반부유(entraining)시키거나 섬유 산업에서 일반적으로 사용되는 유형의 기계식 인발 롤 주위에 권취함으로써 적용시킬 수 있는 인발 장력을 유지하면서 필라멘트를

칭 대역을 통해 전진시킴으로써 필라멘트를 감쇠시키는 단계; (d) 인발된 스트랜드를 다공성 표면(예를 들어, 이동하는 스크린 또는 다공성 벨트) 상에 웹으로 수집하는 단계; 및 (e) 느슨한 스트랜드의 웹을 부직포에 접합하는 단계. 접합은 열-캘린더링 공정, 접착제 접합 공정, 열풍 접합 공정, 니들 펀치 공정, 하이드로인탱글링 공정, 및 이들의 조합을 포함하지만 이에 제한되지 않는 다양한 수단에 의해 달성될 수 있다.As used herein, the term "spunbond" refers to the manufacture of a nonwoven fabric comprising the steps of: (a) extruding a molten thermoplastic strand from a plurality of fine capillaries called spinnerets; (b) strands of thermoplastic strand comprising, for example, a polyethylene composition, with a stream of air that is generally cooled to promote solidification of the molten thermoplastic strand.

calling; (c) the filaments are held while maintaining the drawing tension that can be applied by pneumatically entraining the filaments in a stream of air or by winding them around mechanical drawing rolls of the type commonly used in the textile industry.

attenuating the filament by advancing it through a quenching zone; (d) collecting the drawn strands into a web on a porous surface (eg, a moving screen or porous belt); and (e) bonding the web of loose strands to the nonwoven fabric. Bonding may be accomplished by a variety of means including, but not limited to, a heat-calendering process, an adhesive bonding process, a hot air bonding process, a needle punch process, a hydroentangling process, and combinations thereof.

As used herein, the term "curvature" is the result of the composition of the fiber and not the result of any post-extrusion process that can affect the bending or crimping of the fiber (e.g., thermal mechanical crimping or attenuation). Refers to the bending or crimping of individual fibers. The amount of curvature of the bicomponent fibers disclosed herein can be measured according to the test method described below.

fiber

The fibers taught herein may be formed by any conventional spinning technique. For example, the first and second regions of the bicomponent fibers may be formed into fibers through melt spinning. In melt spinning, a first region comprising a first polyethylene composition and a second region comprising a second polyethylene composition are melted and coextruded so that they can be forced into air or other gas through a fine orifice in a metal plate called a spinneret. where they cool and solidify to form bicomponent fibers. The coagulated fibers can be drawn through air jets, rotating rolls, or godes and placed on a conveyor belt as a web to form a nonwoven fabric. A meltblown nonwoven fabric comprising bicomponent fibers according to embodiments of the present disclosure may be formed. In other embodiments, a spunbond nonwoven fabric comprising bicomponent fibers according to embodiments of the present disclosure may be formed.

The fibers disclosed herein have improved curvature as a result of being made of polyethylene, and other advantageous properties such as recyclability, tactile softness, and extensibility. The improved curvature of the fibers disclosed herein is not the result of mechanical crimping or post-extrusion processes such as damping with heated air or application of tension. The fibers of various embodiments include all or a majority of a polyethylene composition. Nonwovens comprising polyethylene compositions are known to be soft to the touch, and materials comprising polyethylene compositions are candidates for compatibility with polyethylene recycling streams.

In embodiments, the bicomponent fiber has a curvature of at least 0.50 mm ⁻¹ . The curvature of bicomponent fibers can be measured according to the test method described below. All individual values and subranges of at least 0.50 mm ⁻¹ are disclosed herein and are included. For example, in some embodiments, the bicomponent fibers can have a curvature that is at least 0.50, 0.60, 0.70, or 0.80 mm ^-1 as measured according to the test method described below. In other embodiments, the bicomponent fiber has a range from 0.50 to 3.00, 0.50 to 2.50, 0.50 to 2.00, 0.50 to 1.50, 0.50 to 1.00, 1.00 to 3.00, 1.00 to 2.50, 1.00 as measured according to the test method described below. to 2.00, 1.00 to 1.50, 1.50 to 3.00, 1.50 to 2.50, 1.50 to 2.00, 2.00 to 3.00, or 2.00 to 2.50 mm ^-1 .

In embodiments, the bicomponent fiber comprises a first region and a second region, and the weight ratio of the first region to the second region is from 90:10 to 10:90. All individual values and subranges of the ratio from 90:10 to 10:90 are disclosed herein and are included. For example, in embodiments, the weight ratio of the first region to the second region is 80:20 to 20:80, 70:30 to 30:70, 60:40 to 40:60, or 55:45 to 45: May be 55.

Although the fibers taught herein are bicomponent fibers, one skilled in the art will understand that it may not be readily discernible from the fiber itself that it comprises two different regions because both regions of the fiber contain a polyethylene composition. One skilled in the art will understand that the percentage (%) crystallinity of the individual polyethylene regions of the bicomponent fibers can be measured in situ using Raman microscopy and multivariate calibration as described in the Test Methods section below. The difference between the Raman measured % crystallinity of two regions of a bicomponent fiber according to embodiments of the present disclosure corresponds to the improved curvature of the fiber. In embodiments, the first polyethylene composition of the first region of the bicomponent fiber has a Raman measured % crystallinity that is at least 5.0% greater than the Raman measured % crystallinity of the second polyethylene composition of the second region of the bicomponent fiber, wherein the Raman measured % crystallinity Measurement % crystallinity is measured according to the test method described below. All individual values and subranges that are greater than at least 5.0% are included herein and disclosed herein, eg, the first polyethylene composition of the first region of the bicomponent fiber

At least 5.0% greater, at least 7.5% greater, at least 10.0% greater, or 5.0% to 20.0% greater, 5.0% to 15.0% greater than the Raman measured % crystallinity of the second polyethylene composition of the second region of the bicomponent fiber. greater, 7.5% to 15.0% greater, 10.0% to 15.0% greater, 3.5% to 12.0% greater, 5.0% to 12.0% greater, 7.5 to 12.0% greater, or 10.0% to 12.0% greater It may have a Raman-measured % crystallinity, wherein the Raman-measured % crystallinity is measured according to the test method described below.

center

In embodiments, a bicomponent fiber comprises a fiber center, a first region having a first center and a second region having a second center, wherein at least one of the first center and the second center is the same as the fiber center. don't

로 계산되며, 여기서 A는 이성분 섬유 단면의 면적이다. 도 1은 이성분 섬유 및 그의 중심뿐만 아니라 이성분 섬유의 제2 영역의 중심을 예시하고 있다. 소정 영역의 중심으로부터 섬유 중심까지의 거리는 "P_rx"로 정의될 수 있으며, 섬유 중심에 대한 제1 중심 또는 제2 중심의 중심 오프셋은 "P_rx/r"로 정의될 수 있다.As used herein, the term "center" means the arithmetic mean of all points of the area of the cross section of a bicomponent fiber. For example, a bicomponent fiber according to embodiments of the present disclosure has a fiber center denoted by C _f , and a given region (eg, first region or second region) of the bicomponent fiber is C _rx has an independent center denoted by , where x denotes the region (e.g., a first region can be represented by C _r1 and a second region can be represented by C _r2 ), and "r" is C is the average distance from _f to the outer surface of the bicomponent fiber, and

, where A is the area of the bicomponent fiber cross section. Figure 1 illustrates the bicomponent fiber and its center as well as the center of the second region of the bicomponent fiber. The distance from the center of the region to the center of the fiber may be defined as "P _rx ", and the center offset of the first center or the second center with respect to the center of the fiber may be defined as "P _rx /r".

In embodiments, at least one of the first center and the second center is not identical to the fiber center. Bicomponent fibers may have various shapes, such as an eccentric core sheath, side-by-side arrangement, or divided pie, where the first or second center is different from the fiber center, but the fiber center and the first center and the second center are In the same case, it may have a concentric shape (eg, a core-sheath concentric shape). In embodiments, the first center of the first area and the second center of the second area are arranged such that the first area and the second area are arranged side by side. In other embodiments, the first center of the first region and the second center of the second region are arranged such that the first region and the second region are arranged in a divided pie shape. In further embodiments, the first center of the first region and the second center of the second region are arranged such that the first region and the second region are in the form of an eccentric core-sheath, in which case the first region is a bicomponent fiber. becomes the sheath of and the second region becomes the core region of the bicomponent fiber and the sheath region surrounds the core region.

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

First Region and Second Region—Metallocene or Single Site Catalyst Embodiments

In certain embodiments, the bicomponent fiber includes a first region and a second region; the first region comprises a first polyethylene composition having a molecular weight distribution expressed as a ratio of weight average molecular weight to number average molecular weight (M _w(GPC) /M _n(GPC) ) of less than 3.0; the second region comprises a second polyethylene composition having a density lower than the density of the first polyethylene composition; The first polyethylene composition has a crystallization temperature (Tc) that is at least 2° C. higher than the crystallization temperature (Tc) of the second polyethylene composition. In these 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 molecular weight distribution expressed as a ratio of weight average molecular weight to number average molecular weight (M _w(GPC) /M _n(GPC) ) of less than 3.0. All individual values and subranges of the molecular weight distribution (M _{w (GPC)} /M _{n (GPC)} ) less than 3.0 are disclosed herein and are included, for example, in embodiments, the first polyethylene composition is less than 3.0 , less than 2.8, less than 2.6, less than 2.4, or less than 2.2, or 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 a molecular weight distribution (M _{w (GPC)} / M _{n (GPC)} ) from the range of 2.2 to 2.4, wherein the molecular weight distribution is the ratio of weight average molecular weight to number average molecular weight (M _{w (GPC)} / M _n(GPC) ) and can be measured according to the test method described below.

Also in these embodiments, the first polyethylene composition has a crystallization temperature (Tc) that is at least 2° C. higher than the crystallization temperature (Tc) of the second polyethylene composition. All individual values and subranges of the crystallization temperature (Tc) of the first polyethylene composition that are at least 2° C. greater than the crystallization temperature (Tc) of the second polyethylene composition are disclosed herein and are included, e.g., the first polyethylene composition is at least 2° C. higher, at least 4° C. higher, at least 6° C. higher, at least 8° C. higher, at least 10° C. higher, or at least 12° C. higher than the crystallization temperature (Tc) of the second polyethylene composition. The second polyethylene composition may have a crystallization temperature (Tc) higher, at least 14° C. higher, at least 16° C. higher, or at least 18° C. higher, or at a crystallization temperature (Tc) of the first polyethylene composition. The difference minus the crystallization temperature (Tc) is 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°C to 30°C, 15°C to 25°C, or 15°C to 20°C, wherein the crystallization temperature (Tc) can be measured according to Differential Scanning Calorimetry (DSC) described below. there is.

Also in these embodiments, the first polyethylene composition can have a melting temperature (Tm) that is at least 2° C. higher than the melting temperature (Tm) of the second polyethylene composition. All individual values and subranges of the melting temperature (Tm) of the first polyethylene composition that are at least 2° C. greater than the melting temperature (Tm) of the second polyethylene composition are disclosed herein and are included, e.g., the first polyethylene composition is at least 2° C. higher, at least 4° C. higher, at least 6° C. higher, at least 8° C. higher, at least 10° C. higher, or at least 14° C. higher than the melting temperature (Tm) of the second polyethylene composition. higher, at least 18° C. higher, at least 22° C. higher, at least 26° C. higher, or at least 30° C. higher, or the melting temperature (Tm) of the first polyethylene composition ( Tm) minus the melting temperature (Tm) of the second polyethylene composition, the difference is 2 ° C to 50 ° C, 2 ° C to 45 ° C, 2 ° C to 40 ° C, 2 ° C to 35 ° C, 2 ° C to 30 ° C, 2 ° C to 25°C, 2°C to 20°C, 2°C to 15°C, 2°C to 10°C, 2°C to 5°C, 5°C to 50°C, 5°C to 45°C, 5°C to 40°C, 5°C to 35°C , 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 40 ℃, 25 ℃ to 35 ℃, 30 ℃ to 50 ℃, 30 ℃ to 40 °C, 30 °C to 35 °C, or 30 °C to 32 °C, where the melting temperature can be determined according to DSC as described below.

Also in these embodiments, the melting temperature (Tm) of the first polyethylene composition may be less than 130°C. All individual values and subranges that fall below 130°C are disclosed herein and are included, for example, the melting temperature (Tm) of the first polyethylene composition is less than 130°C, less than 129.8°C, less than 129.6°C, 129.4°C. less than, less than 129.2 °C, less than 129 °C, or less than 128.9 °C, where the melting temperature (Tm) can be determined according to DSC as described below. In embodiments, the melting temperature (Tm) of the second polyethylene composition may be less than 127°C. All individual values and subranges that fall below 127°C are disclosed herein and are included, e.g., the melting temperature (Tm) of the second polyethylene composition is less than 127°C, less than 126.5°C, less than 125°C, 120°C. less than 115°C, less than 110°C, less than 105°C, less than 100°C, less than 99°C, less than 98.5°C, or less than 98°C, wherein the melting temperature (Tm) is measured according to DSC as described below. It can be.

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°C. All individual values and subranges that are at least 1.5° C. are included and disclosed herein, for example, the difference between the melting temperature (Tm) of the first polyethylene composition minus the melting temperature (Tm) of the second polyethylene composition is at least 1.5°C, at least 2.0°C, at least 2.5°C, at least 3°C, at least 5°C, at least 10°C, at least 15°C, at least 20°C, at least 25°C, or at least 30°C, or from 1.5°C to 40°C, 2.0°C to 40°C, 2.5°C to 40°C, 1.5°C to 30°C, 2.0°C to 30°C, 2.5°C to 30°C, 1.5°C to 20°C, 2.0°C to 20°C, 2.5°C to 20°C, 1.5°C to 10°C °C, 2.0 °C to 10 °C, 2.5 °C to 10 °C, 1.5 °C to 5 °C, 2.0 °C to 5 °C, 2.5 °C to 5 °C, 10 °C to 40 °C, 10 °C to 35 °C, 10 °C to 30 °C, ranges from 10°C to 20°C, 20°C to 40°C, 20°C to 35°C, 20°C to 30°C, 25°C to 40°C, 25°C to 35°C, 28°C to 32°C, or 29°C to 31°C , where the melting temperature (Tm) can be determined according to DSC as described below.

Region 1 and Region 2 - Ziegler-Natta Catalyst Embodiments

In other embodiments, the bicomponent fiber includes a first region and a second region; the first region comprises a first polyethylene composition having a molecular weight distribution, expressed as the ratio of weight average molecular weight to number average molecular weight (M _w(GPC) /M _n(GPC) ) greater than 3.0; the second region comprises a second polyethylene composition having a density lower than the density of the first polyethylene composition; The first polyethylene composition has a crystallization temperature (Tc) that is at least 3.5° C. higher 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 molecular weight distribution, expressed as a ratio of weight average molecular weight to number average molecular weight (M _w(GPC) /M _n(GPC) ) greater than 3.0. All individual values and subranges of the molecular weight distribution (M _{w (GPC)} /M _{n (GPC)} ) greater than 3.0 are disclosed herein and are included, for example, in embodiments, the first polyethylene composition is 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 from 3.0 to 5.0, from 3.0 to 4.5, from 3.0 to 4.0, from 3.0 to 3.5, from 3.0 to 3.2, from 3.1 to 5.0, from 3.1 4.5, 3.1 to 4.0, 3.1 to 3.5, or 3.1 to 3.2, and may have a molecular weight distribution (M _{w (GPC)} /M _{n (GPC)} ), wherein the molecular weight distribution is weight average molecular weight to number average molecular weight It can be expressed as a ratio of (M _{w (GPC)} / M _{n (GPC)} ). In such embodiments, the first polyethylene composition may be formed in the presence of a Ziegler-Natta catalyst.

Also in these embodiments, the first polyethylene composition has a crystallization temperature (Tc) that is at least 3.5° C. higher than the crystallization temperature (Tc) of the second polyethylene composition. All individual values and subranges of the crystallization temperature (Tc) of the first polyethylene composition that are at least 3.5° C. greater than the crystallization temperature (Tc) of the second polyethylene composition are disclosed herein and are included, e.g., the first polyethylene composition is at least 3.5°C higher, at least 4°C higher, at least 4.5°C higher, at least 5°C higher, at least 5.5°C higher, or at least 6°C higher than the crystallization temperature (Tc) of the second polyethylene composition. higher, at least 6.2° C. higher, or at least 6.4° C. higher, or may have a crystallization temperature (Tc) of the second polyethylene composition from the crystallization temperature (Tc) of the first polyethylene composition 3.5°C to 15°C, 3.5°C to 10°C, 3.5°C to 7.5°C, 3.5°C to 6°C, 5°C to 15°C, 5°C to 10°C, 5°C to 7.5°C, 5°C to 6°C , 6°C to 15°C, 6°C to 10°C, 6°C to 8°C, or 6°C to 7°C, wherein the crystallization temperature (Tc) can be determined according to DSC as described below. there is.

Also in these embodiments, the first polyethylene composition can have a melting temperature (Tm) that is at least 5° C. higher than the melting temperature (Tm) of the second polyethylene composition. All individual values and subranges of the melting temperature (Tm) of the first polyethylene composition that are at least 5° C. greater than the melting temperature (Tm) of the second polyethylene composition are disclosed herein and are included, e.g., the first polyethylene composition is at least 5 °C higher, at least 5.2 °C higher, at least 5.4 °C higher, at least 5.6 °C higher, at least 5.8 °C higher, or at least 6.0 °C higher than the crystallization temperature (Tc) of the second polyethylene composition. may have a crystallization temperature (Tc) that is at least 6.2° C. higher, and at least 6.4° C. higher, at least 6.6° C. higher, at least 6.8° C. higher, or at least 6.9° C. higher, or The difference obtained by subtracting the melting temperature (Tm) of the second polyethylene composition from the melting temperature (Tm) of the first polyethylene composition is 5 ° C to 10 ° C, 5 ° C to 7.5 ° C, 5 ° C to 7 ° C, 5 ° C to 6.5 ° C, 5 °C to 6 °C, 5.5 °C to 10 °C, 5.5 °C to 7.5 °C, 5.5 °C to 7 °C, 5.5 °C to 6 °C, 6 °C to 10 °C, 6 °C to 7.5 °C, 6 °C to 7 °C, 6.5 °C to 10 °C, 6.5 °C to 7.5 °C, or 6.5 °C to 7 °C, where the melting temperature (Tm) can be determined according to DSC as described below.

1st area and 2nd area - general

In embodiments described herein, the second polyethylene composition has a density lower than the density of the first polyethylene composition, where the density may be measured according to ASTM D792. In some embodiments, the density of the first polyethylene composition is at least 0.015 g/cm 3 higher than the density of the second polyethylene composition. All individual values and subranges that amount to at least 0.015 g/cm are included and disclosed herein; for example, in some embodiments, the density of the first polyethylene composition is at least 0.015 g/cm greater than the density of the second polyethylene composition. cm3, at least 0.030 g/cm3, or at least 0.040 g/cm3 greater, or the difference between the density of the first polyethylene composition minus the density of the second polyethylene composition is between 0.015 g/cm3 and 0.100 g/cm3, 0.015 g/cm3 to 0.080 g/cm3, 0.015 g/cm3 to 0.060 g/cm3, 0.015 g/cm3 to 0.040 g/cm3, 0.015 g/cm3 to 0.020 g/cm 3 , 0.020 g/cm 3 to 0.100 g/cm3, 0.020 g/cm3 to 0.080 g/cm3, 0.020 g/cm3 to 0.060 g/cm3, 0.020 g/cm3 to 0.040 g/cm3, 0.020 g/cm3 to 0.030 g/cm3, 0.030 g/cm3 to 0.100 g/cm3, 0.030 g/cm3 to 0.080 g/cm, 0.030 g/cm to 0.060 g/cm, 0.030 g/cm to 0.050 g/cm, 0.030 g/cm to 0.040 g/cm, or 0.040 g/cm to 0.050 g/cm, Density may be measured according to ASTM D792.

In embodiments described herein, the first polyethylene composition may have a density of at least 0.925 g/cm 3 , where the density may be measured according to ASTM D792. All individual values and subranges of density in the range of at least 0.925 g/cm are disclosed herein and are included. For example, in some embodiments, the first polyethylene composition has a density of at least 0.935, at least 0.940, at least 0.945, at least 0.950, at least 0.955, at least 0.960, or at least 0.965 g/cm3, which can be measured according to ASTM D792. Alternatively, the first polyethylene composition may have a density of from 0.925 to 0.980, 0.930 to 0.980, 0.940 to 0.980, 0.950 to 0.980, 0.930 to 0.980, 0.930 to 0.970, 0.930 to 0.960, 0.930, as measured according to ASTM D792. , 0.940 내지 0.980, 0.940 내지 0.970, 0.940 내지 0.960, 0.940 내지 0.950, 0.945 내지 0.980, 0.945 내지 0.970, 0.945 내지 0.960, 0.945 내지 0.955, 0.950 내지 0.980, 0.950 내지 0.970, 0.950 내지 0.960, 0.960 내지 0.980, 또는 0.960 to 0.980 g/cm 3 .

In the embodiments described above and herein, the first region of the bicomponent fiber comprises at least 75% by weight of the first polyethylene composition. All individual values and subranges that amount to at least 75% by weight are included and disclosed herein, e.g., the first region is at least 75% by weight, at least 80% by weight, at least 85% by weight, at least 90% by weight, At least 95%, or 75% to 100%, 75% to 90%, 75% to 80%, 80% to 100%, or 90% to 100% by weight of the first polyethylene composition, wherein the weight percent is based on the total weight of the first region.

In the embodiments described above and herein, the second region of the bicomponent fiber comprises at least 75% by weight of the second polyethylene composition. All individual values and subranges that are at least 75% by weight are included and disclosed herein, e.g., the second region is at least 75%, at least 80%, at least 85%, at least 90%, At least 95%, or 75% to 100%, 75% to 90%, 75% to 80%, 80% to 100%, or 90% to 100% by weight of a second polyethylene composition, wherein the weight percent is 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 include additional components, such as one or more other polymers and/or one or more additives. Other polymers include polyesters, other polyethylene compositions, propylene-based polymers (e.g., polypropylene homopolymers, propylene-ethylene copolymers, or propylene/alpha-olefin interpolymers), or propylene-based plastomers or elastomers. can do. The amount of other polymers can be up to 25% by weight based on the total weight of either the first region or the second region comprising such other polymers. For example, in embodiments, the first region and/or the second region contains up to 25% by weight of a propylene-based plastomer or propylene-based elastomer (such as VERSIFY ^™ polymer available from The Dow Chemical Company and ExxonMobil Chemical Co. VISTAMAXX ^™ polymers available from ), low modulus or/and low molecular weight polypropylenes (such as Idemitsu's L-MODU ^™ polymers), random copolypropylenes, or propylene-based olefin block copolymers (such as Intune). Possible additives include antistatic agents, color enhancers, dyes, lubricants, fillers, pigments, primary antioxidants, secondary antioxidants, processing aids, UV stabilizers, antiblocking agents, slip agents, tackifiers, flame retardants, antibacterial agents, odor reducers, antifungal agents and combinations thereof, but are not limited thereto. The first region and/or the second region may contain from about 0.01 or 0.1 or 1 to about 25 or about 20 or about 15 or about 0.01 or 0.1 or 1 to about 25 or about 20 or about 15 or It may contain about 10% by weight of these additives.

polymerization catalyst

Any conventional polymerization process may be used to prepare the first or second polyethylene composition. Such conventional polymerization processes include solution polymerization processes using one or more conventional reactors, such as loop reactors, isothermal reactors, stirred tank reactors, batch reactors in parallel, series, and/or any combination thereof. However, it is not limited thereto. Such conventional polymerization processes also include gas phase, solution phase or slurry polymerization, or any combination thereof, using any type of reactor or reactor configuration known in the art.

In embodiments, the solution phase polymerization process is performed at a temperature in the range of 115 to 250° C. in one or more fully stirred reactors, such as one or more loop reactors; eg, at 155 to 225° C., at pressures ranging from 300 to 1000 psi; For example, it may occur at pressures of 400 to 750 psi. In one embodiment that is a dual reactor, the temperature of the first reactor is in the range of 115 to 190 °C, eg 115 to 150 °C, and the temperature of the second reactor is 150 to 200 °C, eg 170 to 195 °C is in the range of °C. In another embodiment, which is a single reactor, the temperature of the reactor ranges from 115 to 250 °C, such as from 155 to 225 °C. Residence times in solution phase polymerization processes typically range from 2 to 30 minutes; For example, in the range of 10 to 20 minutes. Ethylene, solvent, one or more catalyst systems, optionally one or more cocatalysts, 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, this solvent is commercially available under the designation ISOPAR E from ExxonMobil Chemical Co., Houston, Texas. The resulting mixture of the first or second propylene composition and solvent is then removed from the reactor and the first or second propylene composition is separated. The solvent is typically recovered through a solvent recovery unit, ie a heat exchanger and gas-liquid separator drum, and then recycled back to the polymerization system.

In one embodiment, the first or second propylene composition may be prepared via a solution polymerization process in a dual reactor system, for example a dual loop reactor system, wherein ethylene and optionally one or more α-olefins are coupled to one or more catalyst systems polymerized in the presence of In another embodiment, the first or second propylene composition may be prepared via a solution polymerization process in a single reactor system, for example a single loop reactor system, wherein ethylene and optionally one or more α-olefins are coupled to one or more catalyst systems polymerized in the presence of As noted above, in certain embodiments, the first polyethylene composition may be formed in the presence of a metallocene or single site catalyst system. In other embodiments, the first polyethylene composition may be formed in the presence of a Ziegler-Natta catalyst system.

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

(I)

(I)

In Formula (I), M is a metal selected from titanium, zirconium, or hafnium, and the metal is in 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 overall charge neutral; Each Z is independently selected from -O-, -S-, -N(R ^N )-, or -P(R ^P )-, wherein each R ^N and R ^P is independently (C1-C30) hydrocarbyl or (C1-C30)heterohydrocarbyl; L is (C ₁ -C ₄₀ )hydrocarbylene or (C ₁ -C ₄₀ )heterohydrocarbylene, and (C ₁ -C ₄₀ )hydrocarbylene is two compounds of formula (I) (to which L is bonded). A (C 1 -C 40 )heterohydrocarbylene having a moiety comprising a 1-carbon atom to 10-carbon atom linker backbone linking the Z groups, or (C ₁ -C ₄₀ )heterohydrocarbylene is a 1- to 10-carbon atom linking two Z groups of formula (I). has a moiety comprising a 10-membered linker backbone, and each of 1 to 10 atoms of the 1- to 10-membered linker backbone of (C ₁ -C ₄₀ )heterohydrocarbylene is independently a carbon atom or a heteroatom; , each heteroatom is independently O, S, S(O), ^S (O) ₂ , Si(RC ) ₂ , Ge( ^RC ) ₂ , P( ^RC ), or N( ^RC ) , independently each R ^C is (C ₁ -C ₃₀ )hydrocarbyl or (C ₁ -C ₃₀ )heterohydrocarbyl; R ¹ and R ⁸ are independently -H, ( ^C ₁ -C ₄₀ )hydrocarbyl, ( ^C ₁ -C ₄₀ )heterohydrocarbyl, -Si(RC ) ₃ , -Ge(RC ) 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)- , halogens, and radicals having formula (II), formula (III), or formula (IV):

In Formulas (II), (III), and (IV), R ^31-35 , R ^41-48 , or R ^51-59 are each independently (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= ^CHRC , -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, provided that at least one of R ¹ or R ⁸ is of the formula (II), a radical having formula (III), or formula (IV), wherein R ^C , R ^N , and R ^P are as defined above.

In Formula (I), R ^2-4 , R ^5-7 , and R ^9-16 are each independently (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 -, (RC ) 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, where R ^C , R ^N , and R ^P are as defined above.

A catalyst system comprising a metal-ligand complex of formula (I) can be catalytically activated by any technique known in the art for activating metal-based catalysts of olefin polymerization reactions. For example, a metal-ligand complex of formula (I) can be catalytically activated by contacting the complex with an activating co-catalyst, or by combining the complex with an activating co-catalyst. Activating cocatalysts suitable for use herein include alkyl aluminum; polymeric or oligomeric alumoxanes (also known as aluminoxanes); 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 above activating promoters and technologies are also contemplated. The term "alkyl aluminum" means a monoalkyl aluminum dihydride or monoalkylaluminum dihalide, a dialkyl aluminum hydride or dialkyl aluminum halide, or a trialkylaluminum. Examples of polymeric or oligomeric alumoxanes include methylalumoxane, triisobutylaluminum-modified methylalumoxane, and isobutylalumoxane.

Lewis acid activators (cocatalysts) include Group 13 metal compounds containing 1 to 3 (C ₁ -C ₂₀ )hydrocarbyl substituents as described herein. Examples of Group 13 metal compounds include tri((C ₁ -C ₂₀ )hydrocarbyl)-substituted-aluminum or tri((C ₁ -C ₂₀ )hydrocarbyl)-boron compounds; tri(hydrocarbyl)-substituted-aluminum, tri((C ₁ -C ₂₀ )hydrocarbyl)-boron compounds; tri((C ₁ -C ₁₀ )alkyl)aluminum, tri((C ₆ -C ₁₈ )aryl)boron compounds; and halogenated (including perhalogenated) derivatives thereof. In a further example, the Group 13 metal compound is tris(fluoro-substituted phenyl)borane, tris(pentafluorophenyl)borane. The activating cocatalyst may be tris((C ₁ -C ₂₀ )hydrocarbyl borate (eg, trityl tetrafluoroborate) or tri((C ₁ -C ₂₀ )hydrocarbyl)ammonium tetra((C ₁ -C ₂₀ )hydrocarbyl)borane (eg, bis(octadecyl)methylammonium tetrakis(pentafluorophenyl)borane. As used herein, the term “ammonium” refers to ((C ₁ -C ₂₀ )hydrocarbyl ) ₄ N ⁺ , ((C ₁ -C ₂₀ )hydrocarbyl) ₃ N(H) ⁺ , ((C ₁ -C ₂₀ )hydrocarbyl) ₂ N(H) ₂ ⁺ , (C ₁ -C ₂₀ )hydro Nitrogen cation which is carbylN(H) ₃ ⁺ , or N(H) ₄ ⁺ , wherein each (C ₁ -C ₂₀ )hydrocarbyl may be the same or different when two or more are present.

Combinations of neutral Lewis acid activators (cocatalysts) are tri((C ₁ -C ₄ )alkyl)aluminum and halogenated tri((C ₆ -C ₁₈ )aryl)boron compounds, particularly tris(pentafluorophenyl). ) a combination of boranes; or mixtures comprising combinations of such neutral Lewis acid mixtures with polymeric or oligomeric alumoxanes, and combinations of single neutral Lewis acids, particularly tris(pentafluorophenyl)borane, with polymeric or oligomeric alumoxanes. (Metal-ligand complex):(tris(pentafluoro-phenylborane):(alumoxane) [eg (Group 4 metal-ligand complex):(tris(pentafluoro-phenylborane):(alumoxane) )] is from 1:1:1 to 1:10:30, or from 1:1:1.5 to 1:5:10.

A catalyst system comprising a metal-ligand complex of formula (I) can be activated to form an active catalyst composition by combining with one or more cocatalysts, such as cation forming cocatalysts, strong Lewis acids, or combinations thereof. . Suitable activating cocatalysts include polymeric or oligomeric aluminoxanes, particularly methyl aluminoxane, as well as inert, compatible, non-coordinating ion forming compounds. Exemplary suitable cocatalysts include modified methyl aluminoxane (MMAO), bis(hydrogenated tallow alkyl)methyl, tetrakis(pentafluorophenyl)borate( ^1- )amine, and combinations thereof, but not limited

One or more of the above activating cocatalysts may be used in combination with each other. One preferred combination is a mixture of tri((C ₁ -C ₄ )hydrocarbyl)aluminum, tri((C ₁ -C ₄ )hydrocarbyl)borane, or ammonium borate with an oligomeric or polymeric alumoxane compound. The ratio of the total number of moles of the at least one metal-ligand complex of formula (I) to the total number of moles of the at least one activating co-catalyst is from 1:10,000 to 100:1. This ratio may be at least 1:5000, or at least 1:1000, and may be 10:1 or less, or 1:1 or less. When alumoxane is used alone as the activating co-catalyst, preferably the number of moles of alumoxane used may be at least 100 times the number of moles of the metal-ligand complex of formula (I). When tris(pentafluorophenyl)borane is used alone as an activating cocatalyst, the ratio of the number of moles of tris(pentafluorophenyl)borane used to the total number of moles of one or more metal-ligand complexes of formula (I) is 0.5 :1 to 10:1, 1:1 to 6:1, or 1:1 to 5:1. The remaining activating cocatalyst is generally used in a molar amount approximately equal to the total molar amount of the at least one metal-ligand complex of formula (I).

Test Methods

density

Density is measured according to ASTM D792 and is expressed in grams/cm 3 (g/cm 3 ).

Melt Index (I2)

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

curvature

The amount of curvature is measured through an optical microscope. The amount of curvature is calculated based on the reciprocal of the radius of the helix formed by the fiber. The amount of curvature is equal to the radius of the circle formed by projecting the helix formed by the fiber onto a surface perpendicular to it. Record the average of at least 5 measurements. Measurements are recorded in units of 1/millimeter (mm ^-1 ).

center offset

For AFM analysis, fibers were immersed in epoxy and polished at cryogenic conditions using a Leica UCT/FCS microtome operated at -140 °C. Topographic and phase images were captured at ambient temperature using a Bruker Icon AFM system with a MikroMasch probe. The probe has a spring constant of 40 N/m and a resonant frequency of about 170 kHz. An imaging frequency of 0.5 to 2 Hz is used with a set point ratio of about 0.8. A single cord is used to measure the diameter of a fiber cross section, divide this measurement in half, and denote the midpoint as the fiber center (Cf). The core region of the bicomponent fiber is divided at 90° into two chords, making visually four quadrants of equal area visible, and the intersection of the two chords defines the center (Cr2) of the core region. The distance between the fiber center (Cf) and the center of the core region (Cr2) is measured and then divided by the fiber radius to calculate the fiber center offset (Pr2/r).

Conventional GPC (Mw/Mn)

Conventional GPC is obtained using a high temperature gel permeation chromatography (GPC) apparatus (PolymerChar, Spain). An IR5 detector ("Measurement Channel") is used as the concentration detector. The weight average (Mw) and number average (Mn) molecular weights of the polymers are calculated using GPCOne software (PolymerChar, Spain) and the molecular weight distribution (Mw/Mn) is determined. The method consisted of three 10 micron PL gel mixed B columns (Agilent Technologies, column size 100 × 7.6 mm) or four 20 micron PL gel mixed A columns (Agilent Technologies, column size 100 × 7.6 mm) operating at a system temperature of 150 °C. mm) is used. Samples were prepared using an autosampler (PolymerChar, Spain) in a 1,2,4-trichlorobenzene solvent containing 200 ppm of the antioxidant butylated hydroxytoluene (BHT) at 160 °C for 3 hours with gentle agitation. at a concentration of 2 mg/mL. The flow rate is 1.0 mL/min and the injection volume is 200 microliters. Plate number is counted using GPCOne software. The chromatography system should contain at least 22,000 plates.

The GPC column set is calibrated using at least 20 narrow molecular weight distribution polystyrene standards. The calibration uses a 3rd order fit for a system with three 10 micron PL gel mixture B columns or a 5th order fit for a system with four 20 micron PL gel mixture A columns. The molecular weight (MW) of the standards ranges from 580 g/mole to 8,400,000 g/mole, and the standards are contained in 6 "cocktail" mixtures. Each standard mixture has a spacing of approximately 10 between individual molecular weights. The standard mixture is purchased from Agilent Technologies. The polystyrene standards are prepared at "0.025 g in 50 mL of solvent" for molecular weights greater than or equal to 1,000,000 g/mole and "0.05 g in 50 mL of solvent" for molecular weights less than 1,000,000 g/mole. The polystyrene standards are dissolved at 80° C. with gentle stirring for 30 minutes. The narrow standards mixture is run first, then the highest molecular weight component in decreasing order to minimize degradation. The polystyrene standard peak molecular weight was converted to polyethylene molecular weight using equation (1) (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621 (1968)) as follows: Converted:

[Equation 1]

In the above formula, MW is the molecular weight of polyethylene (PE) or polystyrene (PS) as indicated, and B is 1.0. It is known to those skilled in the art that A can range from about 0.38 to about 0.44 such that the A value yields 52,000 MWPE for standard reference material (SRM) 1475a. The use of this polyethylene calibration method to obtain molecular weight values, such as molecular weight distribution (MWD or Mw/Mn) and related statistics, is defined herein as the modified method of Williams and Ward. The number average molecular weight, weight average molecular weight, and z average molecular weight are calculated from the formulas below.

[Equation 2]

[Equation 3]

[Equation 4]

In the above formula, M _n,cc , M _w,cc , and M _z,cc (unit: g/mole) are the number average molecular weight, weight average molecular weight, and z average molecular weight obtained from conventional calibration, respectively. w _i is the weight fraction of polyethylene molecules eluted from the retention volume V _i . M _cc,i is the molecular weight (g/mol) of the polyethylene molecule eluted in the retention volume V _i obtained using a conventional calibration (see equation (1)).

Chromatographic peaks should be set to include regions that show significant and appreciable departures from the baseline when the chromatogram is viewed at 20% peak height. The baseline should not integrate below 100 polyethylene equivalent molecular weight and care should be taken to account for antioxidant mismatches from chromatographic mobile phases and prepared samples.

The use of the decane flux marker is shown in the IR5 chromatogram. At any point, the difference in baseline (response) Y-values between the start and end of the baseline should not be greater than 3% of the height of the integrated peak in the chromatogram. In this case, the chromatographic sample must be processed through appropriate matching of sample and mobile phase antioxidants.

w (weight fraction greater than 10 ⁵ g/mol) is calculated according to the MWD curve (w _i versus log M _{cc, i} ) obtained from GPCOne software according to equation (5).

[Equation 5]

Differential scanning calorimetry ( DSC )

DSC is used to measure the melting temperature (Tm) and crystallization temperature (Tc) behavior of polymers over a wide temperature range. For example, this assay is performed using a TA Instruments Q1000 DSC equipped with an RCS (refrigerated cooling system) and an autosampler. During the test, a nitrogen purge gas flow of 50 ml/min is used. Each sample was melt pressed into a thin film at about 175°C; The molten sample is then air-cooled to room temperature (approximately 25° C.). A film sample is formed by pressing a “0.1 to 0.2 g” sample at 175° C. at 1,500 psi for 30 seconds to form a “0.1 to 0.2 mil thick” film. A 3-10 mg, 6 mm diameter specimen is extracted from the cooled polymer, weighed, placed in a light aluminum pan (approximately 50 mg), and crimped closed. An analysis is then performed to determine its thermal properties.

The thermal behavior of the sample is determined by ramping the temperature of the sample up and down to create a heat flow versus temperature profile. First, the sample is rapidly heated to 180° C. and then held isothermally for 5 minutes to eliminate thermal history of the sample. The sample is then cooled to -40°C at a cooling rate of 10°C/min and held isothermally at -40°C for 5 minutes. The sample is then heated to 150° C. at a 10° C./min heating rate (this is the “second heat” ramp). Record the cooling curve and the second heating curve. The cooling curve is analyzed by setting baseline endpoints from the start of crystallization to -20°C. The heating curve is analyzed by setting baseline endpoints from −20° C. to the end of melting. The measured values are: highest peak melting temperature (referred to herein as "melting temperature (Tm)"), highest peak crystallization temperature (referred to herein as "crystallization temperature (Tc)"), heat of fusion (H _f ) (joules per gram ), and [% crystallinity = ((H _f )/(292 J/g)) x 100]. The heat of fusion (H _f ) and melting temperature (Tm) are reported from the second heat curve. The crystallization temperature (Tc) is determined from the cooling curve.

Raman microscopy

The percent crystallinity of the individual polyethylene regions of the bicomponent fibers is measured in situ using Raman microscopy and multivariate calibration. Raman microscopy, a vibrational spectroscopy technique, is sensitive to the vibrations of the polymer backbone and can provide information on both the amorphous and crystalline phases of polymers and polyethylene compositions. Raman can use visible or near infrared light and, when coupled with an optical microscope, provides a lateral spatial resolution of about 0.8 to 1.2 micrometers (depending on the excitation laser and microscope objective used).

A Partial Least Squares (PLS) model is built to correlate the Raman data with the percentage (%) crystallinity calculated from the annealed polyethylene composition density and the annealed base resin density. Polymer density is measured according to ASTM D792. Percent (%) crystallinity is calculated from the measured annealed density using the following equation (Equation 6).

[Equation 6]

where ρ _a = 0.855 g/cc (100% amorphous) and ρ _c = 1.000 g/cc (100% crystalline) density.

Depolarization Raman spectra are acquired using an equivalent Thermo Scientific DXR2 micro-Raman instrument. Raman spectra are acquired using a 900 groove/mm grating. The spectral range covers the Raman shift from 50 to 3500 cm ⁻¹ , maintaining a data interval of 0.964 cm ⁻¹ . Other data acquisition parameters include: Acquisition time: 3 to 10 seconds; Number of acquisitions: 3 to 6; Dark Current Subtract, Cosmic ray Filter, and White Light Compensation: On. 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 polyethylene synthetic resins with densities ranging from 0.859 to 0.964 g/cm are used for calibration and cross-validation of the PLS model. The PLS model was also validated using a set of independent density plaques and then used to measure the resin crystallinity of resins used in bicomponent fiber regions. A PLS model is built with TQ Analyst™ software using the following parameters: Spectral region: 1571 cm ¹ to 971 cm ⁻¹ ; Normalization: integrated area 1356 to 1227 cm ⁻¹ -same baseline points; Total number of samples: 28; # calibration standard: 26; # Independent cross validation samples: 2; # Independent validation samples: 6; Data preprocessed for: annealed base resin density model and calculated % crystallinity model - mean centered, 2nd derivative, SG smoothed (15 points, 3rd order polynomial); A number of factors used for calibration of the two models: annealed base resin density and calculation. % crystallinity = 4.

After validation of the PLS model, longitudinal (parallel to the drawing direction) cross-sections of each bicomponent fiber example are prepared. The cross section is oriented on the sample stage such that the pull direction of the fiber is oriented in an east-west direction on the sample stage. Depolarized Raman spectra were acquired at three different locations in each region of the bicomponent fiber example using a 100x (0.9NA) objective and a 25 micrometer pinhole. The resulting Raman spectra from each region are averaged and used to determine the region % crystallinity using the PLS model.

Example

Synthesis of Polyethylene Compositions

Resins to be developed ("Resin 1", "Resin 2", "Resin 3", and "Resin 4") were prepared according to the following process and table.

All raw materials (monomers and comonomers) and process solvents (narrow boiling range high purity isoparaffinic solvent Isopar-E) are purified with molecular sieves prior to introduction into the reaction environment. Hydrogen is supplied pressurized to a high purity grade, but is not further purified. The reactor monomer feed stream is pressurized above the reaction pressure via a mechanical compressor. The solvent and comonomer (if present) feeds are pressurized above the reaction pressure via a pump. The individual catalyst components are manually batch diluted with purified solvent and pressurized above the reaction pressure. All reaction feed streams are metered by mass flow meters and independently controlled by a computer automated valve control system.

The reactor configuration is a single reactor operation or a dual in-line reactor operation as specified in Table 2.

A single reactor system or a two reactor system in series configuration is used. Each reactor is a continuous solution polymerization reactor consisting of a liquid-filled, non-adiabatic, isothermal, circulating, loop reactor emulating a continuous stirred tank reactor (CSTR) with heat removed. All fresh solvent, monomer, comonomer (if present), hydrogen, and catalyst component feeds are under independent control. The total fresh feed stream to the reactor (solvent, monomers, comonomers [if present], and hydrogen) is maintained in a single solution phase by passing through a heat exchanger, typically controlled to a temperature of 15 to 50°C. All fresh feed to each polymerization reactor is injected into the reactor at two locations, with the reactor volume between each injection location being approximately equal. Fresh feed is controlled with each injector receiving half of the total fresh feed mass flow. Catalyst components are injected into the polymerization reactor through an injection nozzle so that they are introduced into the center of the reactor flow. The first catalyst component feed is computer controlled so that the reactor monomer conversion is maintained at a specified value. The cocatalyst component(s) is supplied based on a specific calculated molar ratio to the primary catalyst component. Immediately following each reactor feed injection location, the feed stream is mixed with the cyclic polymerization reactor contents using static mixing elements. The contents of each reactor are continuously circulated through heat exchangers, which serve to remove a large portion of the reaction heat, while maintaining the temperature on the coolant side, which serves to maintain an isothermal reaction environment, at a specified temperature. Circulation around each reactor loop is provided by a pump.

In a dual in-line reactor configuration, the effluent from the first polymerization reactor (containing solvent, monomers, comonomers [if present], hydrogen, catalyst components, and polymer) exits the first reactor loop and is added to the second reactor loop do.

In all reactor configurations, the final reactor effluent (the second reactor effluent in the case of a dual series, or the single reactor effluent) enters a zone where a suitable reagent (water) is added and reacted with and deactivated. At this same reactor outlet location, other additives may be added to stabilize the polymer.

After catalyst deactivation and additive addition, the reactor effluent is introduced into a devolatilization system, where the polymer is removed from the non-polymer stream. The isolated polymer melt is 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 comonomers (if present) are recycled back to the reactor after passing through the purification system. Small amounts of solvent and comonomers (if present) are removed in the process.

The reactor stream feed data flow corresponding to the values in Table 2 used to make the developing resin is graphically illustrated in FIGS. 2 and 3 . The data is presented so that the complexity of the solvent recycle system is taken into account and the reaction system can be handled simpler in one step through a flow diagram.

[Table 1]

[Table 2]

The following materials are used in the examples.

Poly. 1 is Resin 1 described above.

Poly. 2 is ASPUN™ 6835, a polyethylene composition and linear low density polyethylene fiber resin commercially available from The Dow Chemical Company (Midland, MI).

Poly. 3 is Resin 2 described above.

Poly. 4 is Resin 3 described above.

Poly. 5 is Resin 4 described above.

Poly. 6 is ELITE ^™ 5860, a polyethylene composition and reinforced polyethylene resin commercially available from The Dow Chemical Company (Midland, MI).

Poly. 1 to Poly. 6 has density, melt index (I2), molecular weight distribution (Mw/Mn), crystallization temperature (Tc), and melting temperature (Tm) as reported in Table 3 below.

[Table 3]

formation of fibers

칭 공기 온도 및 유량을 각각 15 내지 -18℃ 및 520 cfm(분 당 입방 피트)로 설정한다.

칭 대역 이후에, 144개의 필라멘트를 공기 스트림을 사용하여 슬롯 유닛 내에 필라멘트를 공압식으로 동반부유시킴으로써 그 필라멘트에 인발 장력을 가한다. 공기 스트림의 속도는 슬롯 흡인기 압력으로 제어한다.The fibers are spun on the Hills Bicomponent Continuous Filament Fiber Spinning Line. It makes bicomponent fibers with an eccentric core sheath shape. The fiber was spun at Hills Line according to the following conditions. The extruder profile is adjusted to achieve a melt temperature of 240°C. The throughput of each hole is 0.5 ghm (grams per hour per minute). Using a Hills Bicomponent die, the core/sheath ratio (by weight) with the first zone containing one example being in one extruder and the second zone containing the other example being in the other extruder according to Table 4 below. ) was run at 40/60 to form Inventive Examples 1, 2, 3, and 4 and Comparative Examples 1, 2, 3, 4, 5, and 6. Set the Hills Line pressure to 40 psi. The die consists of 144 holes with a hole diameter of 0.6 mm and a length/diameter (L/D) of 4/1.

The quench air temperature and flow rate are set at 15 to -18° C. and 520 cubic feet per minute (cfm), respectively.

After the quenching zone, the 144 filaments are subjected to drawing tension by pneumatically co-floating the filaments within the slot unit using an air stream. The velocity of the air stream is controlled by the slot aspirator pressure.

[Table 4]

Table 5 shows the difference in melting temperature subtracted between the first region and the second region in the case of Inventive Examples 1 and 2 and Comparative Examples 1 and 2, having a polyethylene composition in the first region with a molecular weight distribution (Mw/Mn) of less than 3 ( ΔTm), crystallization temperature difference (ΔTc), and density difference (Δdensity).

[Table 5]

Table 6 shows the difference between the first and second regions in the case of Inventive Examples 3 and 4 and Comparative Examples 3, 4, and 5, wherein the molecular weight distribution (Mw/Mn) has a polyethylene composition in the first region greater than 3. This gives the difference in melting temperature (ΔTm), difference in crystallization temperature (ΔTc), and difference in density (Δdensity).

[Table 6]

Certain inventive examples and comparative examples are tested for percent crystallinity according to the Raman microscopy test method described above. Table 7 shows the results.

[Table 7]

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

[Table 8]

Table 9 provides the center offset and radius of fiber data in the case of a particular embodiment.

[Table 9]

Claims (9)

As a bicomponent fiber,
fiber center;
a first region having a first center and a second region having a second center;
the first region comprises a first polyethylene composition having a molecular weight distribution expressed as a ratio of weight average molecular weight to number average molecular weight (M _w(GPC) /M _n(GPC) ) of less than 3.0;
the second region comprises a second polyethylene composition having a density lower than that of the first polyethylene composition;
at least one of the first center and the second center is not identical to a fiber center;
wherein the first polyethylene composition has a crystallization temperature (Tc) that is at least 2° C. higher than the crystallization temperature (Tc) of the second polyethylene composition. The bicomponent fiber of claim 1 , wherein the first polyethylene composition has a melting temperature (Tm) that is at least 2° C. higher than the melting temperature (Tm) of the second polyethylene composition. 3. The bicomponent fiber of claim 1 or 2, wherein the melting temperature (Tm) of the first polyethylene composition is less than 130°C. As a bicomponent fiber,
fiber center;
a first region having a first center and a second region having a second center;
the first region comprises a first polyethylene composition having a molecular weight distribution expressed as a ratio of weight average molecular weight to number average molecular weight (M _w(GPC) /M _n(GPC) ) greater than 3.0;
the second region comprises a second polyethylene composition having a density lower than that of the first polyethylene composition;
at least one of the first center and the second center is not identical to a fiber center;
wherein the first polyethylene composition has a crystallization temperature (Tc) that is at least 3.5° C. higher than the crystallization temperature (Tc) of the second polyethylene composition. 5. The bicomponent fiber of claim 4, wherein the first polyethylene composition has a melting temperature (Tm) that is at least 5° C. higher than the melting temperature (Tm) of the second polyethylene composition. 6. The bicomponent fiber of any one of claims 1 to 5, wherein the density of the first polyethylene composition is at least 0.015 g/cm 3 higher than the density of the second polyethylene composition. 7. A bicomponent fiber according to any one of claims 1 to 6, wherein the fiber has a curvature greater than 0.5 mm ⁻¹ . 8 . The bicomponent fiber of claim 1 , wherein the first polyethylene composition has a Raman-measured % crystallinity that is at least 5.00% higher than the Raman-measured % crystallinity of the second polyethylene composition. A nonwoven fabric comprising the bicomponent fibers according to any one of claims 1 to 8.

Images