Bi-component fiber, non-woven fabric and preparation method and application thereof

Abstract

The invention relates to bicomponent fibers, non-woven fabrics, and methods of making the same. The bi-component fiber comprises: a core comprising a first polymer component; and a sheath comprising a second polymer component comprising: 55 to 95% by weight of a first polyethylene comprising 70.0 to 100.0% by weight of units derived from ethylene and 0 to 30.0% by weight of units derived from a C3-C20 alpha-olefin and having a density of 0.905 to 0.926 g / cm3, a melt index of 12 to 35 g / 10 min, a Mw / Mn of 1.5 to 5.0, and a CDBI of 60 to 85%; and 5 to 45 wt% of a second polyethylene having a density greater than or equal to 0.940 g / cm3 and a melt index of 10 to 40 g / 10 min. The bi-component fiber and the non-woven fabric formed by the bi-component fiber can achieve an excellent balance of mechanical strength and soft hand feeling.

Description

Technical Field

[0001] The present application relates to the field of polymer fibers and fabrics, in particular, to bicomponent fibers containing polyethylene, nonwovens containing the bicomponent fibers, a method for preparing the nonwovens, and uses of the bicomponent fibers and nonwovens. Background Art

[0002] Nonwovens (also called nonwovens, nonwovens) are widely used as top sheets, leg covers and back sheets in disposable hygiene products such as baby diapers, feminine hygiene products and adult incontinence products. The trend of upgrading and high-endization drives manufacturers to pursue nonwovens with better hand feel in order to bring better comfort to consumers. The bicomponent fiber spunbond process is a process for making nonwovens, which can produce nonwovens with a softer or fluffier hand feel.

[0003] The bicomponent fibers used to make spunbond nonwoven fabrics generally have a core-sheath structure, with a core of a polymer having a higher melting temperature surrounded by a sheath of a polymer having a lower melting temperature. Polymers commonly used for the core include polypropylene (PP), polyethylene terephthalate (PET), etc.; polymers commonly used for the sheath include polyethylene (PE), etc. In the current market, PE fibers from Dow under the trade name Aspun are used to prepare bicomponent spunbond nonwovens. In addition, high-density polyethylene (HDPE) is also often used.

[0004] WO2023244899A1 discloses a bicomponent fiber comprising a first polymer component and a second polymer component, wherein the first polymer component may comprise polyethylene terephthalate; and the second polymer component may comprise polyethylene, wherein the polyethylene has a density of about 0.930 g / cm 3 to about 0.955g / cm 3 , a melt flow index (2.16 kg at 190°C) of about 10 g / 10 min to about 50 g / 10 min, a melt index ratio (MIR) of about 15 to about 30, a weight average molecular weight to number average molecular weight ratio (Mw / Mn) of about 2 to about 4, a weight % of TREF eluted at 90°C and lower temperatures of about 10 weight % to about 80 weight %, and a weight % of TREF eluted at 95°C and higher temperatures of about 3 weight % or greater. Similar to other prior arts, a single polyethylene is used to form the sheath in this patent application. In addition, this patent application cuts the bicomponent fibers into bicomponent staple fibers, and produces nonwovens from the bicomponent staple fibers using hot air bonding.

[0005] Compared with short fibers, long fibers generally provide advantages in terms of surface smoothness and mechanical strength, but are inferior to short fibers in terms of softness. Therefore, how to improve the softness of long fibers while maintaining mechanical strength is one of the issues of concern in the art.

[0006] In addition, the limitation of using a single polyethylene to form a sheath is that the controllability of the performance is poor. If the performance of the material is to be adjusted, new polyethylene needs to be synthesized again, which is undoubtedly time-consuming and labor-intensive. A solution may be blending. However, conventionally, mechanical strength and softness are contradictory. Improving softness often sacrifices mechanical strength, and vice versa. It is difficult to obtain a blending system with a good balance of mechanical strength and softness. Therefore, how to flexibly regulate the mechanical strength and softness of the bicomponent fiber and the nonwoven formed therefrom according to the application, and achieve a good balance of mechanical strength and softness, is also one of the issues of concern in this area. Summary of the invention

[0007] In a first aspect, the present application provides a bicomponent fiber comprising:

[0008] a core, wherein the core comprises a first polymer component comprising one or more of: polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymer, polyoxymethylene, or polyetheretherketone; and

[0009] A sheath, wherein the sheath comprises a second polymer component, based on the total weight of the second polymer component, the second polymer component comprising:

[0010] 55 to 95 weight percent of a first polyethylene comprising 70.0 to 100.0 weight percent of units derived from ethylene and 0 to 30.0 weight percent of units derived from C3-C 20 α-olefin units and have a value of 0.905 to 0.926 g / cm 3 A density of 100 g / min, a melt index at 2.16 kg / 190° C. of 12 to 35 g / 10 min, a molecular weight distribution Mw / Mn of 1.5 to 5.0, and a composition distribution breadth index CDBI of 60% to 85%; and

[0011] 5 to 45 weight percent of a second polyethylene having a molecular weight greater than or equal to 0.940 g / cm 3 A density of 2.16 kg / 190° C. and a melt index of 10 to 40 g / 10 min at 2.16 kg / 190° C.

[0012] In a second aspect, the present application provides a nonwoven comprising bicomponent fibers as described above and below.

[0013] In a third aspect, the present application provides a method for preparing a nonwoven as described above and below, comprising:

[0014] (a) forming a melt of a first polymer component;

[0015] (b) forming a melt of the second polymer component;

[0016] (c) extruding a melt of the first polymer component and a melt of the second polymer component through a die configured to form a core-sheath structure to form a bicomponent fiber; and

[0017] (d) bonding the bicomponent fibers to form a nonwoven.

[0018] In a fourth aspect, the present application provides a use of the bicomponent fiber as described above or below or the nonwoven as described above or below for making a top sheet, a leg cover or a back sheet in a baby diaper, a feminine hygiene product or an adult incontinence product.

[0019] Surprisingly, it is found that the technical solution of the present application can flexibly adjust the mechanical strength and softness of the bicomponent fibers and the nonwoven fabric formed therefrom, and achieve a good balance between the mechanical strength and softness. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a graph of HOM versus (density*basis weight) for each example plotted based on the test results in Table 3.

[0021] Figure 2 3 is a graph of MD tensile strength versus (density*basis weight) for various examples plotted based on the test results in Table 3.

[0022] Figure 3 TD tensile strength of each example is plotted as a function of (density*basis weight) based on the test results in Table 3.

[0023] Details

[0024] Definition and test methods

[0025] Unless otherwise indicated, room temperature is 25°C.

[0026] An "olefin" is a linear, branched or cyclic compound of carbon and hydrogen having at least one double bond.

[0027] "Polymer" has two or more identical or different monomer (mer) units. "Homopolymer" is a polymer having identical monomer units. The term "polymer" as used herein includes, but is not limited to, homopolymers, copolymers, terpolymers, etc. The term "polymer" as used herein also includes impact, block, graft, random and alternating copolymers. Unless otherwise specifically stated, the term "polymer" shall also include all possible geometric configurations. Such configurations may include isotactic, syndiotactic and random symmetries.

[0028] As used herein, unless otherwise specified, the term "copolymer" refers to a polymer formed by the polymerization of at least two different monomers (i.e., monomer units). For example, the term "copolymer" includes copolymerization products of propylene and α-olefins such as ethylene, 1-hexene. A "terpolymer" is a polymer having three monomer units that are different from each other. Therefore, the term "copolymer" also includes terpolymers and tetrapolymers such as copolymer products of mixtures of ethylene, propylene, 1-hexene and 1-octene.

[0029] "Different" as used to refer to monomeric monomeric units means that the monomeric units differ from each other by at least one atom or are isomerically different. An "ethylene polymer" or "ethylene copolymer" is a polymer or copolymer comprising at least 50 mole % ethylene derived units, a "propylene polymer" or "propylene copolymer" is a polymer or copolymer comprising at least 50 mole % propylene derived units, and so forth. For purposes of the present invention, polyethylene is an ethylene polymer.

[0030] As used herein, when a polymer is referred to as "comprising, consisting of, or consisting essentially of a monomer," the monomer is present in the polymer in the polymerized / derivative form of the monomer. For example, when a copolymer is said to have an "ethylene" content of 35% to 55% by weight, it is understood that the monomer units in the copolymer are derived from ethylene in the polymerization reaction, and the derived units are present at 35% to 55% by weight based on the weight of the copolymer. Thus, a polymer or copolymer said to have a 90% by weight "ethylene" content is equivalent to a polymer or copolymer said to have a 90% by weight "ethylene-derived" content or 90% by weight "units derived from ethylene," etc.

[0031] As used herein, "polyethylene" means an ethylene homopolymer or a copolymer comprising at least 79 wt.% ethylene. The terms "polyethylene polymer", "polyethylene", "ethylene polymer", "ethylene copolymer" and "ethylene-based polymer" have the same meaning as polyethylene copolymers, except where otherwise indicated (e.g., when referring to polyethylene homopolymers, this means polymers formed from ethylene monomers that do not contain comonomer units, e.g., 100 wt.% ethylene-derived units).

[0032] As used herein, "high density polyethylene (HDPE)" means a polyethylene produced in a gas phase and / or slurry phase polymerization and having a density of 0.940 g / cm 3 Up to 0.970g / cm 3 Ethylene homopolymers and ethylene copolymers having a range of densities.

[0033] As used herein, "low density polyethylene (LDPE)" means a polyethylene produced in high pressure free radical polymerization and having a density of 0.910 g / cm 3 Up to 0.940g / cm 3 Ethylene homopolymers and / or ethylene copolymers having a density within a certain range.

[0034] As used herein, "linear low density polyethylene (LLDPE)" means a polyethylene produced in a suspension, solution, slurry or gas phase polymerization process and having an average molecular weight of 0.910 g / cm 3 Up to 0.940g / cm 3 The LLDPE can be produced with conventional Ziegler-Natta catalysts, vanadium catalysts, metallocene catalysts, and / or other suitable catalysts for polymerizing ethylene and comonomers in gas phase reactors, high pressure tubular reactors and / or slurry reactors and / or with any of the disclosed catalysts in solution reactors.

[0035] As used herein, "spunbond" refers to a melt spinning process for forming fabrics in which a polymer melt or solution is extruded through a spinneret to form filaments, which are cooled and then attenuated by a suitable device, such as by electrostatic charge or high velocity air, and such attenuated filaments ("fibers") are then laid down on a moving web to form a fabric. The fibers produced by the spunbond process typically have a degree of molecular orientation imparted therein.

[0036] As used herein, "fiber" is a structure whose length is much larger than its diameter or width; the average diameter is in the order of 0.1 μm to 250 μm, and comprises natural and / or synthetic materials. Fibers can be "monocomponent" or "bicomponent". Bicomponent fibers contain two different chemical and / or physical properties extruded from separate extruders but the same spinneret, wherein the two polymers are in the same filament, resulting in fibers having different domains. The configuration of such bicomponent fibers can be, for example, a sheath / core arrangement, wherein one polymer is surrounded by another, side-by-side (as described in US 5,108,820) or in the form of islands in the sea (as described in US 7,413,803). Fibers can be continuous (long fibers) or discontinuous (short fibers). The aspect ratio of long fibers is greater than 60, preferably 200-500, while the aspect ratio of short fibers is less than 60, preferably 20-60.

[0037] However formed, any "web" of fibers may be used as is (unbonded) or may be bonded, for example, by heating (eg, by passing the web of fibers through a heated calender or rolls).

[0038] Moment and distribution of molecular weight (Mw, Mn, Mz, Mw / Mn, Mz / Mn, etc.) and monomer / comonomer content (C2, C4, C6 and / or C8 and / or other, etc.) and g'(vis) were determined by using high temperature gel permeation chromatography (Polymer Char GPC-IR) equipped with a multi-channel bandpass filter based infrared detector IR5, an 18-angle light scattering detector and a viscometer. Three Agilent PLgel 10 μm Mixed-B LS columns were used to provide polymer separation. Detailed analysis principle and method for determination of molecular weight and g' vis Described in paragraphs

[0044] -

[0051] of PCT Publication WO2019 / 246069A1, which is incorporated herein by reference (note that the equation c= / / / mentioned in paragraph

[0044] regarding the concentration (c) at each point in the chromatogram is c=βI, where β is the mass constant and I is the IR5 broadband signal intensity (I) minus the baseline). Unless specifically mentioned, all molecular weight moments used or mentioned in this disclosure are determined according to the absolute determination method (such as mentioned in paragraphs

[0044] -

[0051] of the just-mentioned publication), noting that for the equation in such paragraph

[0044] , a=0.695 and K=0.000579 (1-0.75Wt) are used, where Wt is the weight fraction of the comonomer, and further noting that the comonomer composition is determined by the ratio of the IR5 detector intensities corresponding to the CH2 and CH3 channels calibrated with a series of PE and PP homo / copolymer standards, the nominal values ​​of which are predetermined by NMR or FTIR as indicated in paragraph

[0045] of the just-mentioned PCT publication (providing methyl groups / 1000 total carbons (CH3 / 1000TC)). Other parameters required can be found in the paragraphs mentioned in the WO2019 / 246069A1 disclosure text, but for convenience, some are included here: TCB at 145°C n = 1.500; I = 665nm; dn / dc = 0.1048mL / mg.

[0039] The density values ​​of polymers are measured by following ASTM D1505-10.

[0040] Each melt flow index or melt index (MI) and high load melt index (HLMI) are measured on a Goetfert MI-4 melt indexer according to ASTM D1238-13, wherein the MI is measured at 190°C, 2.16 kg load (sometimes referred to as I2); and the HLMI is measured at 190°C, 21.6 kg load (sometimes referred to as I 21 ). Samples in an amount of 5 to 6 g were loaded into the barrel of the instrument at 190°C and compressed manually. Thereafter, the material was automatically compacted in the barrel by lowering all available weight onto the piston to remove all air bubbles. Data acquisition started after a 6 min pre-melting time.

[0041] The melt flow index ratio or melt index ratio (equivalently MFR or MIR) is the ratio HLMI / MI (or I 21 / I2).

[0042] First Polyethylene

[0043] The first polyethylene may include or be a linear low density polyethylene (LLDPE), wherein the linear low density polyethylene comprises a polyethylene derived from ethylene and one or more C3-C 20 In various embodiments, the first polyethylene has one or more of the following properties:

[0044] (a) Density (ASTM D4703 / D1505) from about 0.905 to about 0.926 g / cm 3 or about 0.915 to about 0.925 g / cm 3 or about 0.915 to about 0.920 g / cm 3 or about 0.916 to about 0.920 g / cm 3 ;

[0045] (b) a composition distribution breadth index ("CDBI") of about 60% to about 85%, or about 65% to about 85%, or about 70% to about 80%. "CDBI" refers to the weight percentage of copolymer molecules having a comonomer content within 50% of the median total molar comonomer content. The CDBI of a copolymer can be measured using techniques known in the art. The CDBI of a copolymer is readily determined using well-known techniques for isolating individual fractions of a copolymer sample. One such technique is temperature rising elution fractionation (TREF), as described in Wild et al., J. Poly. Sci., Poly. Phys. Ed., Vol. 20, pp. 441-455 (1982), which is incorporated herein by reference. Details regarding determining the CDBI of a copolymer are known to those skilled in the art, see, for example, PCT patent application WO 1993 / 003093, published on February 18, 1993, regarding CDBI;

[0046] (c) a weight average molecular weight (Mw) of about 15,000 to about 400,000 g / mol, about 20,000 to about 250,000 g / mol, about 20,000 to about 200,000 g / mol, about 25,000 to about 150,000 g / mol, about 30,000 to about 100,000 g / mol, about 35,000 to about 80,000 g / mol, or about 40,000 to about 60,000 g / mol;

[0047] The number average molecular weight (Mn) may be about 5,000 to about 100,000 g / mol, about 7,500 to about 80,000 g / mol, about 10,000 to about 60,000 g / mol, about 12,500 to about 40,000 g / mol, about 15,000 to about 30,000 g / mol;

[0048] The z-average molecular weight (Mz) may be about 50,000 to about 800,000 g / mol, about 60,000 to about 400,000 g / mol, about 70,000 to about 200,000 g / mol, about 75,000 to about 100,000 g / mol;

[0049] (d) a molecular weight distribution ("MWD", "Mw / Mn") of about 1.5 to about 5.0, or about 2.0 to about 3.5. Techniques for determining molecular weight ("Mw" and "Mn") and molecular weight distribution ("MWD", "Mw / Mn") can be found in U.S. Pat. No. 4,540,753 to Cozewit et al. and references cited therein, and VerStrate et al., Macromolecules, Vol. 21, p. 3360 (1986) and references cited therein, the foregoing documents being incorporated herein by reference;

[0050] Mz / Mw is from about 1.2 to about 5.0, or from about 1.4 to about 3.0;

[0051] Mz / Mn is from about 2.0 to about 7.5, or from about 3.5 to about 6.0;

[0052] (e) a melt index ("MI", ASTM D-1238, 2.16 kg, 190°C) of about 12 to about 35 g / 10 min, about 15 to about 35 g / 10 min, or about 15 to about 25 g / 10 min, or about 17 to about 25 g / 10 min, or about 18 to about 20 g / 10 min; and

[0053] (f) Branching Index (as defined herein) g' vis is greater than or equal to about 0.85, or greater than or equal to about 0.9, or greater than or equal to about 0.93, or greater than or equal to about 0.95, or greater than or equal to about 0.97, indicating a substantially linear structure of the molecular chain.

[0054] In one class of embodiments, the first polyethylene may have one or more of the following properties: a melt index (MI) (190°C / 2.16kg) of about 18 g / 10 min to about 20 g / 10 min; W About 20,000 to about 200,000 g / mol; M W / Mn is from about 2.0 to about 4.5; and a density is from about 0.916 to about 0.920 g / cm 3 .

[0055] The first polyethylene comprises about 70.0 wt % to about 100.0 wt % of units derived from ethylene. The lower limit of the ethylene content range of the first polyethylene can be about 70.0 wt %, about 75.0 wt %, about 80.0 wt %, about 85.0 wt %, about 90.0 wt %, about 92.0 wt %, about 94.0 wt %, about 95.0 wt %, about 96.0 wt %, about 97.0 wt %, about 98.0 wt % or about 99.0 wt %. The upper limit of the ethylene content range of the first polyethylene can be about 80.0 wt %, about 85.0 wt %, about 90.0 wt %, about 92.0 wt %, about 94.0 wt %, about 95.0 wt %, about 96.0 wt %, about 97.0 wt %, about 98.0 wt %, about 99.0 wt %, about 99.5 wt % or about 100.0 wt %. Therefore, the first polyethylene can have less than 30.0 wt % of units derived from C3-C 20 Polymer units of olefins (preferably α-olefins, such as hexene or octene). 20 The lower end of the olefin content range may be about 25.0 wt%, about 20.0 wt%, about 15.0 wt%, about 10.0 wt%, about 8.0 wt%, about 6.0 wt%, about 5.0 wt%, about 4.0 wt%, about 3.0 wt%, about 2.0 wt%, about 1.0 wt%, or about 0.5 wt%. 20 The upper limit of the olefin content range can be about 20.0 wt %, about 15.0 wt %, about 10.0 wt %, about 8.0 wt %, about 6.0 wt %, about 5.0 wt %, about 4.0 wt %, about 3.0 wt %, about 2.0 wt % or about 1.0 wt %. Any lower limit can be combined with any upper limit to form a range. The comonomer content is based on the total content of all monomers in the first polyethylene.

[0056] C3-C 20 The α-olefin comonomers may be linear or branched, and two or more comonomers may be used if desired. Examples of suitable α-olefin comonomers include propylene, butene, 1-pentene; 1-pentene with one or more methyl, ethyl or propyl substituents; 1-hexene; 1-hexene with one or more methyl, ethyl or propyl substituents; 1-heptene; 1-heptene with one or more methyl, ethyl or propyl substituents; 1-octene; 1-octene with one or more methyl, ethyl or propyl substituents; 1-nonene; 1-nonene with one or more methyl, ethyl or propyl substituents; 1-decene substituted with ethyl, methyl or dimethyl; 1-dodecene and styrene. Preferred α-olefins may include pentene, hexene, heptene, octene or a combination thereof.

[0057] In various embodiments, the first polyethylene is polymerized in the presence of a single-site catalyst. In a specific embodiment, the single-site catalyst is a metallocene. For example, the first polyethylene may include or be a metallocene-catalyzed linear low-density polyethylene (m-LLDPE). Useful metallocene catalysts, resins, and manufacturing methods are described in U.S. Patent No. 6,932,592, entitled "Very Low Density Polyethylene Produced by Metallocenes" (Farley et al.), which is incorporated herein by reference.

[0058] The first polyethylene described herein is not limited to any particular method of preparation.In various embodiments, the ethylene derived resin is prepared by gas phase polymerization of a supported catalyst containing a bridged bis(alkyl-substituted dicyclopentadienyl) zirconium dichloride transition metal component and a methylaluminoxane cocatalyst.

[0059] In addition to those discussed above, first polyethylenes useful in the present invention include copolymers commercially available from ExxonMobil Chemical Company, Houston, Texas, such as those sold under the tradename EXCEED TM Those sold, including but not limited to those sold under the brand name EXCEED TM Those sold by 0019XC.

[0060] EXCEED TM 0019XC is a m-LLDPE, ethylene 1-hexene copolymer, with a viscosity of 0.918 g / cm 3 density, a melt index of 19 g / 10 min (190°C / 2.16 kg), a melting peak temperature of 113°C and a Vicat softening temperature of 95.0°C. TM 0019XC has a 1-hexene content of 9.34 wt%, a Mw / Mn of 2.9, and a CDBI of 77%.

[0061] Second polyethylene

[0062] The second polyethylene may include or be high density polyethylene (HDPE). In various embodiments, the second polyethylene has one or more of the following properties:

[0063] (a) Density greater than or equal to about 0.940 g / cm 3 , or 0.940 g / cm 3 Up to 0.970g / cm 3 , or 0.945 g / cm 3 Up to 0.965g / cm 3 , or 0.950g / cm 3 Up to 0.970g / cm 3 ;

[0064] (b) a melt index ("MI", ASTM D-1238, 2.16 kg, 190°C) of about 10 to about 40 g / 10 min, about 15 to about 35 g / 10 min, or about 15 to about 30 g / 10 min, or about 18 to about 25 g / 10 min;

[0065] (c) a weight average molecular weight (Mw) of about 15,000 to about 400,000 g / mol, about 20,000 to about 250,000 g / mol, about 20,000 to about 200,000 g / mol, about 25,000 to about 150,000 g / mol, about 30,000 to about 100,000 g / mol, about 35,000 to about 80,000 g / mol, or about 40,000 to about 60,000 g / mol;

[0066] The number average molecular weight (Mn) may be about 4,000 to about 100,000 g / mol, about 6,000 to about 60,000 g / mol, about 10,000 to about 40,000 g / mol, about 12,000 to about 20,000 g / mol;

[0067] The z-average molecular weight (Mz) may be about 80,000 to about 1,000,000 g / mol, about 100,000 to about 800,000 g / mol, about 120,000 to about 400,000 g / mol, about 150,000 to about 200,000 g / mol;

[0068] (d) a molecular weight distribution ("MWD", "Mw / Mn") of from about 2.0 to about 6.0, or from about 2.5 to about 5.5, or from about 2.5 to about 4.5;

[0069] Mz / Mw is from about 1.5 to about 5.0, or from about 2.0 to about 3.5;

[0070] Mz / Mn is from about 5.0 to about 15.0, or from about 8.0 to about 13.0;

[0071] (e) Branching Index (as defined herein) g' vis is greater than or equal to about 0.85, or greater than or equal to about 0.9, or greater than or equal to about 0.92, or greater than or equal to about 0.94, or greater than or equal to about 0.95, or greater than or equal to about 0.96, indicating a substantially linear structure of the molecular chain.

[0072] Suitable second polyethylenes may be polyethylene homopolymers or ethylene-α-olefin copolymers, wherein the α-olefin may be any of those discussed above in conjunction with the first polyethylene.

[0073] A suitable second polyethylene may be produced by any suitable process known to those skilled in the art such as gas phase fluidised bed polymerisation or slurry polymerisation, or a combination thereof (eg in the case of a reactor or other bimodal HDPE composition, which may be produced in two or more reactors in series).

[0074] In addition to those discussed above, second polyethylenes useful in the present invention include HDPEs commercially available from ExxonMobil Chemical Company, Houston, Texas, or commercially available from PetroChina Fushun Petrochemical, including but not limited to those sold under the designation HDPE 2911FS.

[0075] Blending

[0076] The blends of the first polyethylene and the second polyethylene described herein can be prepared by any procedure that produces a mixture of the components, such as dry blending, melt blending, etc. In certain embodiments, a complete mixture of the polymer components is indicated by morphological uniformity of the dispersion of the polymer components.

[0077] Melt Blending: Continuous melt mixing equipment is typically used. These processes are well known in the art and include single and twin screw compounding extruders and other machines and processes designed to intimately homogenize the polymer components.

[0078] Dry Blending: The first polyethylene, the second polyethylene, and other optional components can be dry blended and fed directly to a fiber or nonwoven process extruder. Dry blending is accomplished by combining the first polyethylene, the second polyethylene, and other optional components in a dry blending device. Such equipment and processes are well known in the art and include drum tumblers, double cone drum mixers, and the like. In this case, the drum tumbler and other optional components are melted (when available) and homogenized in a process extruder similar to a melt blending process. Instead of making pellets, the homogenized molten polymer is delivered to a die or spinneret to form fibers and fabrics.

[0079] Bicomponent Fibers

[0080] The bicomponent fibers of the present disclosure comprise a core and a sheath, wherein the core may comprise a first polymer component and the sheath may comprise a second polymer component, wherein the second polymer component may comprise the first polyethylene and the second polyethylene as described above.

[0081] In various embodiments, based on the gross weight of the second polymer component, the second polymer component can include 10 wt % to 100 wt % of the first polyethylene and 0 wt % to 90 wt % of the second polyethylene. For example, the content of the first polyethylene can be from 10 wt %, 15 wt %, 20 wt %, 25 wt %, 30 wt %, 40 wt %, 50 wt %, 60 wt %, 70 wt %, 80 wt %, 90 wt %, 95 wt %, or 99 wt % lower limit to 100 wt %, 99 wt %, 95 wt %, 90 wt %, 80 wt %, 70 wt %, 60 wt %, 50 wt %, 45 wt %, 40 wt %, 35 wt %, 30 wt %, or 20 wt % upper limit, including the range consisting of any two values ​​above, as long as the lower limit is less than the upper limit. The content of the second polyethylene can be in a range from a lower limit of 0 weight %, 5 weight %, 10 weight %, 15 weight %, 20 weight %, 25 weight %, 30 weight %, 40 weight %, 50 weight %, 60 weight %, 70 weight %, 80 weight %, 85 weight %, or 89 weight % to an upper limit of 90 weight %, 89 weight %, 85 weight %, 80 weight %, 70 weight %, 60 weight %, 50 weight %, 45 weight %, 40 weight %, 35 weight %, 30 weight %, 20 weight %, 15 weight %, or 10 weight %, including ranges consisting of any two of the above values, as long as the lower limit is less than the upper limit.

[0082] In a preferred embodiment, based on the total weight of the second polymer component, the second polymer component comprises 55 wt % to 95 wt % of the first polyethylene; and 5 wt % to 45 wt % of the second polyethylene. For example, the second polymer component comprises 60 wt % to 80 wt % of the first polyethylene; and 20 wt % to 40 wt % of the second polyethylene. In this embodiment, the mechanical strength and softness of the bicomponent fiber and the nonwoven formed therefrom can be flexibly adjusted, and a good balance of mechanical strength and softness can be achieved.

[0083] Examples of polymers that can be used in or as the first polymer component can include, but are not limited to, propylene-based polymers (e.g., homopolymers, impact copolymers, copolymers), ethylene-based polymers (e.g., LDPE, LLDPE, HDPE (copolymers and block copolymers)), functionalized polyolefins (e.g., EXXELOR TM , maleic anhydride functionalized elastomers, ethylene copolymers), plastomers (e.g., ethylene-α-olefin copolymers), polyurethanes, polyesters such as polyethylene terephthalate, polylactic acid, polyvinyl chloride, polytetrafluoroethylene, styrenic block copolymers, ethylene vinyl acetate copolymers, polyamides, polycarbonates, cellulosics (e.g., RAYON TM LYOCELLTM TENCIL TM ), elastomers, poly(acetylene), poly(thiophene), poly(aniline), poly(fluorene), poly(pyrrole), poly(3-alkylthiophene), poly(phenylene sulfide), polynaphthalene, poly(phenylene vinylene), poly(vinylidene fluoride), poly(oxyethylene glycol) polymers (POP), polyoxymethylene (POM), polyetheretherketone (PEEK), and blends of any two or more of these materials. Useful polymers also include plastomers (e.g., ethylene-α-olefin copolymers and block copolymers), polyurethanes, polyesters such as polyethylene terephthalate (PET), polylactic acid, polyvinyl chloride, polytetrafluoroethylene, styrenic block copolymers, ethylene vinyl acetate copolymers, polyamides, polycarbonates, cellulosics (e.g., RAYON TM LYOCELL TM TENCIL TM ), elastomers, poly(acetylene), poly(thiophene), poly(aniline), poly(fluorene), poly(pyrrole), poly(3-alkylthiophene), poly(phenylene sulfide), polynaphthalene, poly(phenylene vinylene), poly(vinylidene fluoride), etc., and blends of any two or more of these materials. Preferred polymers include, but are not limited to, polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymers, polyoxymethylene, polyetheretherketone, etc., and any blends thereof.

[0084] In a preferred embodiment, the first polymer component comprises one or more of the following: polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymer, polyoxymethylene or polyetheretherketone, preferably polypropylene or polyethylene terephthalate, most preferably polypropylene.

[0085] In various embodiments, there is no particular limitation on the relative amounts of the first polymer component and the second polymer component. Typically, the weight ratio of the first composition component to the second polymer component is 10:90-90:10, such as 20:80-80:20, 30:70-70:30, 40:60-60:40, 45:55-55:45, and particularly 50:50.

[0086] One or more additives may be incorporated into the first polymer component and / or the second polymer component. Examples of additives may include, but are not limited to, stabilizers, antioxidants, fillers, colorants, nucleators, dispersants, mold release agents, slip agents, flame retardants, plasticizers, pigments, vulcanization or curing agents, vulcanization or curing accelerators, curing retardants, processing aids, tackifying resins, etc., and any combination thereof. Other additives may include fillers and / or reinforcing materials, such as carbon black, clay, talc, calcium carbonate, mica, silicon dioxide, silicates, etc., and any combination thereof.

[0087] The antioxidants may be primary and secondary antioxidants. Examples of antioxidants may include, but are not limited to, hindered phenols, hindered amines, phosphate esters, and the like, and any combination thereof.

[0088] The bicomponent fibers of the present disclosure can be prepared in a melt spinning process (also referred to as melt spinning), which is a process in which a polymer melt or solution is extruded through a spinneret to form filaments (also referred to as monofilaments).

[0089] In one or more embodiments, the core-sheath fiber of the present invention is prepared by a melt spinning process, wherein two polymer melts are separately supplied to the spinneret holes and then extruded to form a core-sheath structure. In the case of concentric monofilaments, the hole for supplying the core polymer is at the center of the spinning hole outlet and the flow conditions of the core polymer fluid are strictly limited to maintain the concentricity of the two components during spinning. Eccentric fiber production may include eccentric placement of the inner polymer channel and control of the supply rate of the two component polymers. Alternatively, different elements may be introduced near the supply of the sheath component melt. Alternatively, the single component stream may merge with the concentric core-sheath component just before coming out of the hole. Alternatively, the spinning concentric fiber may be deformed by passing through a hot edge.

[0090] The bicomponent fibers may optionally be stretched (eg, using high speed air and / or rollers) to reduce the diameter of the bicomponent fibers.

[0091] The bicomponent fibers may be optionally treated with a hydrophobic agent or a hydrophilic agent to coat at least a portion of the surface of the bicomponent fibers. The agent may be applied by spraying or other suitable techniques.

[0092] The bicomponent fibers described herein may have a diameter of from about 1 micron to about 30 microns, or from about 5 microns to about 25 microns, or from about 10 microns to about 20 microns, or from about 12 microns to about 18 microns.

[0093] Nonwovens

[0094] The bicomponent fibers may be formed directly into nonwovens of the bicomponent fibers described herein by spunbonding techniques.

[0095] In spunbond technology, spunbond fibers are usually produced, for example, by extruding molten polymers (e.g., using melt-spinning conditions described above) from a large spinneret with thousands of holes or using, for example, a smaller spinneret in rows containing as few as 40 holes. After leaving the spinneret, the molten fiber is quenched by a cross-flow air quenching system, then pulled out from the spinneret and attenuated (pulled) by high-speed air. The filaments formed in this way are collected on a wire mesh ("wire") or a porous forming belt to form a web. The web is then passed through a press roll, and then between heated calender rolls, where the raised areas on one of the rolls bond the web at points covering 10% to 40% of its area to form a nonwoven.

[0096] The extruder can be any extruder conventionally used in the art, such as a twin screw extruder or a single screw extruder. The extruders used to extrude the sheath component and the core component can be identical or different. In one embodiment, the extruder used to extrude the sheath component is a twin screw extruder, and the extruder used to extrude the core component is a single screw extruder. The extrusion temperature is set according to the melt temperature of the polymer to be extruded.

[0097] The calendering roll can be any calendering roll conventionally used in the art. The calendering roll generally includes an upper roll and a lower roll. When bonding is performed by the calendering roll, the temperature of the upper roll is generally higher than the temperature of the lower roll. The bonding temperature is represented by the average temperature of the upper roll and the lower roll. In various embodiments, the bonding temperature can be 100-180°C, such as 110-170°C, 110-150°C, 110-130°C, 120-160°C, 130-160°C.

[0098] Nonwovens made using the bicomponent fibers described herein (e.g., made by spunbond technology) can be characterized by basis weight, which can be measured according to WSP (Worldwide Strategic Partnership) 130.1 (05). The basis weight of the nonwoven can be about 120 g / m 2 or less, or about 5g / m 2 About 120g / m 2 , or about 5g / m 2 About 50g / m 2 , or about 25g / m 2 About 100g / m 2 , or about 80g / m 2 About 120g / m 2 .

[0099] In one embodiment, wherein the second polymer component comprises 60 wt % to 80 wt % of the first polyethylene; and 20 wt % to 40 wt % of the second polyethylene, based on the total weight of the second polymer component, the basis weight of the nonwoven can be 5 g / m 2 Up to 24g / m 2 In this embodiment, an excellent balance of mechanical strength and softness can be achieved.

[0100] The nonwoven may have one or more of the following properties:

[0101] HOM<-0.636*density+4.9493, where the unit of HOM is g and the unit of density is g / cm 3 ;

[0102] MD tensile strength>14.08*basis weight-195.22, where the unit of MD tensile strength is N and the unit of basis weight is g / m2 ;and

[0103] TD tensile strength>5.1485*basis weight-69.177, where the unit of TD tensile strength is N and the unit of basis weight is g / m 2 .

[0104] Unless otherwise indicated, all numerical values ​​used in this specification and the related claims expressing the amount of ingredients, properties such as molecular weight, reaction conditions, etc. should be understood as being modified in all cases by the term "about". Therefore, unless indicated to the contrary, the numerical parameters listed in the following specification and the appended claims are approximate values, which may vary depending on the desired properties sought to be obtained by the embodiment of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be interpreted in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0105] One or more illustrative embodiments including one or more inventive elements are proposed herein. For the sake of clarity, all features of physical implementation are not described or shown in this application. It should be understood that in the development of physical implementations including one or more elements of the present invention, in order to achieve the developer's goal, many specific decisions must be made to achieve, for example, system-related, business-related, government-related and other constraints are observed, which change from time to time with the implementation. Although the developer's efforts may be time-consuming, such efforts are routine tasks for those of ordinary skill in the art who benefit from the present disclosure.

[0106] Although compositions and methods are described herein in terms of "comprising" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. In the context of compositions, consisting essentially of allows for 25 ppm or less (of each) of impurities.

[0107] Additional embodiments

[0108] 1. Bicomponent fiber, comprising:

[0109] a core, wherein the core comprises a first polymer component comprising one or more of: polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymer, polyoxymethylene, or polyetheretherketone; and

[0110] A sheath, wherein the sheath comprises a second polymer component, based on the total weight of the second polymer component, the second polymer component comprising:

[0111] 55 to 95 weight percent of a first polyethylene comprising 70.0 to 100.0 weight percent of units derived from ethylene and 0 to 30.0 weight percent of units derived from C3-C 20 α-olefin units and have a value of 0.905 to 0.926 g / cm 3 A density of 100 g / min, a melt index at 2.16 kg / 190° C. of 12 to 35 g / 10 min, a molecular weight distribution Mw / Mn of 1.5 to 5.0, and a composition distribution breadth index CDBI of 60% to 85%; and

[0112] 5 to 45 weight percent of a second polyethylene having a molecular weight greater than or equal to 0.940 g / cm 3 A density of 2.16 kg / 190° C. and a melt index of 10 to 40 g / 10 min at 2.16 kg / 190° C.

[0113] 2. The bicomponent fiber of embodiment 1, wherein the second polymer component comprises 60 to 80 wt% of the first polyethylene; and 20 to 40 wt% of the second polyethylene, based on the total weight of the second polymer component.

[0114] 3. The bicomponent fiber of embodiment 1 or 2, wherein the first polyethylene has one or more of the following properties:

[0115] Density 0.916 to 0.920 g / cm 3 ,

[0116] The melt index at 2.16 kg / 190°C is 18 g / 10 min to about 20 g / 10 min,

[0117] Molecular weight distribution Mw / Mn is 2.0 to 4.5,

[0118] The composition distribution width index CDBI is 65% to 85%,

[0119] The weight average molecular weight Mw is 30,000-100,000 g / mol,

[0120] Branching index g' vis is greater than or equal to 0.9, and

[0121] The present invention comprises 80.0 to 97.0 wt. % of units derived from ethylene and 3.0 to 20.0 wt. % of units derived from C3-C 20 α-olefin units,

[0122] The C3-C 20 The α-olefin is hexene, and

[0123] The first polyethylene is a linear low-density polyethylene.

[0124] 4. The bicomponent fiber of embodiment 1 or 2, wherein the second polyethylene has one or more of the following properties:

[0125] Density: 0.940 g / cm 3 Up to 0.970g / cm 3 ,

[0126] The melt index at 2.16kg / 190°C is 15g / 10min to 35g / 10min,

[0127] Molecular weight distribution Mw / Mn is 2.0 to 4.5,

[0128] The weight average molecular weight Mw is 30,000-100,000 g / mol,

[0129] Branching index g' vis is greater than or equal to 0.9, and

[0130] The second polyethylene is high-density polyethylene.

[0131] 5. The bicomponent fiber of embodiment 1 or 2, wherein the first polymer component comprises polypropylene.

[0132] 6. The bicomponent fiber of embodiment 1 or 2, wherein the weight ratio of the first polymer component to the second polymer component is 10:90 to 90:10.

[0133] 7. The bicomponent fiber of embodiment 1 or 2, wherein the bicomponent fiber is a bicomponent long fiber.

[0134] 8. Bicomponent fibers, comprising:

[0135] a core, wherein the core comprises a first polymer component, the first polymer component being polypropylene; and

[0136] A sheath, wherein the sheath comprises a second polymer component, based on the total weight of the second polymer component, the second polymer component comprising:

[0137] 70 wt% of a first polyethylene comprising 88 wt% to 92 wt% of units derived from ethylene and 8 wt% to 12 wt% of units derived from hexene and having a molecular weight of 0.918 g / cm 3 A density of 1.5 g / 10 min, a melt index at 2.16 kg / 190° C. of 19 g / 10 min, a molecular weight distribution Mw / Mn of 2.9, and a composition distribution breadth index CDBI of 77%; and

[0138] 30 wt% of a second polyethylene having a thickness of 0.960 g / cm 3 A density of 21 g / 10 min and a melt index at 2.16 kg / 190°C;

[0139] The weight ratio of the first polymer component to the second polymer component is 50:50.

[0140] 9. A nonwoven comprising the bicomponent fiber according to any one of embodiments 1-8.

[0141] 10. The nonwoven fabric according to embodiment 9, wherein the basis weight of the nonwoven fabric is 5 g / m 2 Up to 50g / m 2 .

[0142] 11. The nonwoven according to embodiment 9 or 10, wherein the nonwoven is formed by a spunbond process.

[0143] 12. The nonwoven according to embodiment 9 or 10, wherein the nonwoven has one or more of the following properties:

[0144] HOM<-0.636*density+4.9493, where the unit of HOM is g and the unit of density is g / cm 3 ;

[0145] MD tensile strength>14.08*basis weight-195.22, where the unit of MD tensile strength is N and the unit of basis weight is g / m 2 ;and

[0146] TD tensile strength>5.1485*basis weight-69.177, where the unit of TD tensile strength is N and the unit of basis weight is g / m 2 .

[0147] 13. A method for preparing a nonwoven fabric according to any one of embodiments 9-12, comprising:

[0148] (a) forming a melt of a first polymer component;

[0149] (b) forming a melt of the second polymer component;

[0150] (c) extruding a melt of the first polymer component and a melt of the second polymer component through a die configured to form a core-sheath structure to form a bicomponent fiber; and

[0151] (d) bonding the bicomponent fibers to form a nonwoven.

[0152] 14. Use of the bicomponent fiber according to any one of embodiments 1 to 8 or the nonwoven according to any one of embodiments 9 to 12 for making a top sheet, leg cover or back sheet in a baby diaper, a feminine hygiene product or an adult incontinence product. DETAILED DESCRIPTION

[0153] In order to facilitate a better understanding of the embodiments of the present invention, the following examples of preferred or representative embodiments are given. The following examples should in no way be construed as limiting or defining the scope of the present invention.

[0154] Example

[0155] Table 1 shows the polyethylenes used in the examples.

[0156]

[0157]

[0158] Using the parameters shown in Table 2, bicomponent fibers were produced in a core-sheath configuration with polyethylene or a blend of polyethylene as the sheath and polypropylene (PP) as the core.

[0159] Six types of bicomponent fibers were produced: (F1) core PP and sheath HDPE 2911FS, (F2) core PP and sheath (80% HDPE 2911FS + 20% EXCEED 0019) (i.e., in the sheath composition, HDPE 2911FS accounts for 80% by weight and EXCEED0019 accounts for 20% by weight), (F3) core PP and sheath (70% HDPE 2911FS + 30% EXCEED 0019), (F4) core PP and sheath (60% HDPE 2911FS + 40% EXCEED 0019), (F5) core PP and sheath (30% HDPE 2911FS + 70% EXCEED0019), and (F6) core PP and sheath EXCEED 0019. In all bicomponent long fibers, the core PP is PPH-Y400 from Sinopec, and the weight ratio of core to sheath is 50:50.

[0160] Use the parameters in Table 2 to produce nonwovens by spunbond process. Specifically, produce nonwovens on 1.6 meters of bicomponent production line of Shanghai Jingfa. Polymer, after passing through extruder, produces molten fiber by spinning head extruding molten polymer. After leaving spinning head, molten fiber is quenched by cross-flow air quenching system, then pulled out from spinning head and made to thin by high-speed air. Collect the filaments formed in this way on forming belt to form net. Make net pass through press roller to form nonwoven then.

[0161] Table 3 and Figure 1-3The properties of the resulting nonwoven are provided in.

[0162]

[0163]

[0164] Figure 1 It is a graph of the HOM of each example as a function of (density*basis weight) plotted according to the test results in Table 3. Surprisingly, when normalized to (density*basis weight), Example F5 (30% HDPE 2911FS + 70% EXCEED0019) has the best softness, as reflected in its HOM < -0.636*density+4.9493, while the HOMs of the other examples are all ≥ -0.636*density+4.9493.

[0165] Figure 2 The MD tensile strength of each example is plotted as a function of (density*basis weight) according to the test results in Table 3. It is surprisingly found that when normalized relative to (density*basis weight), the strength of Example F5 (30% HDPE 2911FS + 70% EXCEED 0019) is the best, which is reflected in its MD tensile strength>14.08*basis weight-195.22, while the MD tensile strengths of the other examples are all ≤14.08*basis weight-195.22.

[0166] Figure 3 It is a graph of the TD tensile strength of each example as a function of (density*basis weight) plotted according to the test results in Table 3. It is surprisingly found that when normalized relative to (density*basis weight), Example F5 (30% HDPE 2911FS + 70% EXCEED 0019) has the best strength, which is reflected in its TD tensile strength>5.1485*basis weight-69.177, while the MD tensile strengths of the other examples are all ≤5.1485*basis weight-69.177.

[0167] The above results show that the sheath formula of 30% HDPE 2911FS + 70% EXCEED 0019 can achieve the best balance between softness and tensile strength.

[0168] Test Method

[0169] 1. Fiber size

[0170] Instrument: Carl Zeiss Microlmaging GmbH, Axio Scope.A1

[0171] The test method is based on ExxonMobil method:

[0172] Use an optical microscope to observe the size of the optical fiber at 50x: cut a small piece of fiber and place it on glass. Drop immersion oil on the sample, wait for the sample to be completely immersed, place a cover glass on the fiber sample, and observe and measure.

[0173] 2. Basis weight

[0174] Instrument:LIBERO,FX 3820

[0175] The test method is based on ExxonMobil method:

[0176] The circular sample cutter FX 3820 quickly and accurately cuts circular specimens of a specific fixed area to determine the area weight. The cutter is particularly suitable for woven, nonwoven and knitted textiles, carpets, paper, films, foams and panels. The cutter can be used to prepare samples for basis weight tests. The basis weight of the sample is 3 square pieces with an area of ​​100 cm 2 The average value of the samples (in grams per square meter).

[0177] 3. Tensile strength and elongation

[0178] Instrument: Zwick GmbH., BT2-FZ0.5TH.D16.001

[0179] The test method is based on the ExxonMobil method, referring to the Edana test method WSP 110.4(05):

[0180] This method uses a Zwick tensile testing machine, the sample is prepared into a rectangular shape (50*250mm), the load is measured by a load cell, and the deformation is measured by the crosshead position. Since a rectangular specimen is used, no additional extensometer is used to measure the elongation. The tensile properties of a material determine its strength and elongation under load. When a load is applied to a nonwoven fabric, it stretches, yields, stretches further, and eventually breaks.

[0181] By plotting load against elongation, a so-called "stress-strain curve" is obtained. From this curve, a graph can be obtained that characterizes the tensile properties.

[0182] 4. Softness (HOM, Hand-o-meter)

[0183] Instrument: Thwing-Albert, HOM

[0184] The test method is based on the ExxonMobil method, referenced to WSP 90.3.0(05):

[0185] The Handle-O-Meter uses an LVDT (Linear Variable Differential Transformer) to detect the resistance encountered by the blade as it presses a material specimen into a parallel edge slot. A digital voltmeter (DVM) indicates resistance directly in grams. Two beams (100 gram and 1000 gram) are quickly interchangeable, providing versatility for testing different materials. The instrument automatically detects which beam is in use and adjusts the distance resolution. The slot width is also adjustable to accommodate samples of varying thicknesses. Lower values ​​in grams represent softer materials.

[0186] Therefore, the present invention is well adapted to obtain the results and advantages mentioned and inherent therein. The specific embodiments and configurations disclosed above are illustrative only, as it is apparent to those skilled in the art having the benefit of the teachings herein that different but equivalent means may be employed to modify and implement the present invention. In addition, except as described in the following claims, it is not intended to limit the details of the construction or design shown herein. It is therefore apparent that the specific illustrative embodiments disclosed above may be changed, combined or modified, and all such changes are considered to be within the scope and spirit of the present invention. The invention disclosed illustratively herein may be suitably implemented in the absence of any element not specifically disclosed herein and / or any optional element disclosed herein.

[0187] Although compositions and methods are described in terms of "comprising," "containing," or "including" various components or steps, the compositions and methods may also "consist essentially of" or "consist of" the various components and steps. All numerical values ​​and ranges disclosed above may be varied to some extent.

[0188] Whenever a numerical range with a lower limit and an upper limit is disclosed, any numerical value and any included range falling within the range are specifically disclosed. In particular, the range of each value disclosed herein (having the following form "from about a to about b", or equivalently "from about a to b", or equivalently "from about ab") should be understood to enumerate each numerical value and range contained within the wider range of values. Similarly, when multiple ranges (e.g., 1-100 or 10-90, e.g., 30 to 75) are disclosed, the range from any disclosed lower end to any disclosed upper end (e.g., 10-75) is specifically covered.

[0189] Furthermore, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee. Furthermore, the indefinite articles "a" or "an" as used in the claims are defined herein to mean one or more than one of the element it introduces.

Claims

1. Bicomponent fiber, comprising: a core, wherein the core comprises a first polymer component comprising one or more of: polypropylene, polyethylene terephthalate, polyamide, poly(oxyethylene glycol) polymer, polyoxymethylene, or polyetheretherketone; and A sheath, wherein the sheath comprises a second polymer component, based on the total weight of the second polymer component, the second polymer component comprising: 55 to 95 weight percent of a first polyethylene comprising 70.0 to 100.0 weight percent of units derived from ethylene and 0 to 30.0 weight percent of units derived from C3-C 20 α-olefin units and have a value of 0.905 to 0.926 g / cm 3 A density of 100 g / min, a melt index at 2.16 kg / 190° C. of 12 to 35 g / 10 min, a molecular weight distribution Mw / Mn of 1.5 to 5.0, and a composition distribution breadth index CDBI of 60% to 85%; and 5 to 45 weight percent of a second polyethylene having a molecular weight greater than or equal to 0.940 g / cm 3 A density of 2.16 kg / 190° C. and a melt index of 10 to 40 g / 10 min at 2.16 kg / 190° C.

2. The bicomponent fiber of claim 1, wherein the second polymer component comprises 60 wt% to 80 wt% of the first polyethylene; and 20 wt% to 40 wt% of the second polyethylene, based on the total weight of the second polymer component.

3. The bicomponent fiber of claim 1 or 2, wherein the first polyethylene has one or more of the following properties: Density 0.916 to 0.920 g / cm 3 , The melt index at 2.16 kg / 190°C is 18 g / 10 min to about 20 g / 10 min, Molecular weight distribution Mw / Mn is 2.0 to 4.5, The composition distribution width index CDBI is 65% to 85%, The weight average molecular weight Mw is 30,000-100,000 g / mol, Branching index g' vis is greater than or equal to 0.9, and The present invention comprises 80.0 to 97.0 wt. % of units derived from ethylene and 3.0 to 20.0 wt. % of units derived from C3-C 20 α-olefin units, The C3-C 20 The α-olefin is hexene, and The first polyethylene is a linear low-density polyethylene.

4. The bicomponent fiber of claim 1 or 2, wherein the second polyethylene has one or more of the following properties: Density: 0.940 g / cm 3 Up to 0.970g / cm 3 , The melt index at 2.16kg / 190°C is 15g / 10min to 35g / 10min, Molecular weight distribution Mw / Mn is 2.0 to 4.5, The weight average molecular weight Mw is 30,000-100,000 g / mol, Branching index g' vis is greater than or equal to 0.9, and The second polyethylene is high-density polyethylene.

5. The bicomponent fiber of claim 1 or 2, wherein the first polymer component comprises polypropylene.

6. The bicomponent fiber according to claim 1 or 2, wherein the weight ratio of the first polymer component to the second polymer component is 10:90 to 90:

10.

7. The bicomponent fiber according to claim 1 or 2, wherein the bicomponent fiber is a bicomponent long fiber.

8. Bicomponent fibers, comprising: a core, wherein the core comprises a first polymer component, the first polymer component being polypropylene; and A sheath, wherein the sheath comprises a second polymer component, based on the total weight of the second polymer component, the second polymer component comprising: 70 wt% of a first polyethylene comprising 88 wt% to 92 wt% of units derived from ethylene and 8 wt% to 12 wt% of units derived from hexene and having a molecular weight of 0.918 g / cm 3 A density of 1.5 g / 10 min, a melt index at 2.16 kg / 190° C. of 19 g / 10 min, a molecular weight distribution Mw / Mn of 2.9, and a composition distribution breadth index CDBI of 77%; and 30 wt% of a second polyethylene having a thickness of 0.960 g / cm 3 A density of 21 g / 10 min and a melt index at 2.16 kg / 190°C; The weight ratio of the first polymer component to the second polymer component is 50:

50.

9. A nonwoven comprising the bicomponent fibers according to any one of claims 1 to 8.

10. The nonwoven fabric according to claim 9, wherein the basis weight of the nonwoven fabric is 5 g / m 2 Up to 50g / m 2 .

11. The nonwoven according to claim 9 or 10, wherein the nonwoven is formed by a spunbond process.

12. The nonwoven fabric according to claim 9 or 10, wherein the nonwoven fabric has one or more of the following properties: HOM<-0.636*density+4.9493, where the unit of HOM is g and the unit of density is g / cm 3 ; MD tensile strength>14.08*basis weight-195.22, where the unit of MD tensile strength is N and the unit of basis weight is g / m 2 ;and TD tensile strength>5.1485*basis weight-69.177, where the unit of TD tensile strength is N and the unit of basis weight is g / m 2 .

13. The method for preparing a nonwoven fabric according to any one of claims 9 to 12, comprising: (a) forming a melt of a first polymer component; (b) forming a melt of the second polymer component; (c) extruding a melt of the first polymer component and a melt of the second polymer component through a die configured to form a core-sheath structure to form a bicomponent fiber; and (d) bonding the bicomponent fibers to form a nonwoven.

14. Use of the bicomponent fiber according to any one of claims 1 to 8 or the nonwoven according to any one of claims 9 to 12 for making a top sheet, leg covering or back sheet in baby diapers, feminine hygiene products or adult incontinence products.

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