Bicomponent fibers, nonwovens and methods and uses thereof

Abstract

The present invention relates to bicomponent fibers, nonwovens, and methods of making the same. The bicomponent fibers comprise: a core comprising a first polymeric component; and a sheath comprising a second polymeric component comprising: 55 to 95 wt% of a first polyethylene comprising 70.0 to 100.0 wt% of units derived from ethylene and 0 to 30.0 wt% of units derived from C3-C12 α-olefins and having a density of 0.905 to 0.926 g / cm3, a melt index of 12 to 35 g / 10 min, an 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 / cm3and a melt index of 10 to 40 g / 10 min. The bicomponent fibers and nonwovens formed therefrom of the present invention are capable of achieving an excellent balance of mechanical strength and soft hand. 20 3 3 The present invention relates to bicomponent fibers, nonwovens, and methods of making the same. The bicomponent fibers comprise: a core comprising a first polymeric component; and a sheath comprising a second polymeric component comprising: 55 to 95 wt% of a first polyethylene comprising 70.0 to 100.0 wt% of units derived from ethylene and 0 to 30.0 wt% of units derived from C3-C12 α-olefins and having a density of 0.905 to 0.926 g / cm3, a melt index of 12 to 35 g / 10 min, an 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 / cm3and a melt index of 10 to 40 g / 10 min. The bicomponent fibers and nonwovens formed therefrom of the present invention are capable of achieving an excellent balance of mechanical strength and soft hand.​​

Description

Technical Field

[0001] The present invention 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 known as nonwoven fabrics or nonwovens) are widely used as topsheets, leg covers, and backsheets in disposable hygiene products such as baby diapers, feminine hygiene products, and adult incontinence products. The trend toward upgrading and high-end products is driving manufacturers to pursue nonwovens with a superior hand feel to provide greater comfort for consumers. Bicomponent fiber spunbonding is a process for producing nonwovens that can produce nonwovens with a softer or fluffier hand feel.

[0003] Bicomponent fibers used to make spunbond nonwovens typically have a core-sheath structure, with a core of a polymer with a higher melting temperature surrounded by a sheath of a polymer with a lower melting temperature. Polymers commonly used for the core include polypropylene (PP) and polyethylene terephthalate (PET), while polymers commonly used for the sheath include polyethylene (PE). In the current market, PE fibers sold by Dow under the trade name Aspun are used to make bicomponent spunbond nonwovens. High-density polyethylene (HDPE) is also commonly 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; 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 percent TREF elution at 90°C and lower of about 10 weight percent to about 80 weight percent, and a weight percent TREF elution at 95°C and higher of about 3 weight percent or greater. Similar to other prior art, this patent application uses a single polyethylene to form the sheath. In addition, this patent application cuts the bicomponent fibers into bicomponent staple fibers and produces a nonwoven from the bicomponent staple fibers using hot air bonding.

[0005] Compared with short fibers, long fibers generally offer 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 this field.

[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 blend system with a good balance of mechanical strength and softness. Therefore, how to flexibly regulate the mechanical strength and softness of bicomponent fibers and the nonwovens 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] The sheath comprises a second polymer component comprising, based on the total weight of the second polymer component:

[0010] 55 to 95 wt% of a first polyethylene comprising 70.0 to 100.0 wt% of units derived from ethylene and 0 to 30.0 wt% of units derived from C3-C 20 α-olefin units and having a range of 0.905 to 0.926 g / cm 3 A density of 1000 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 and a melt index at 2.16 kg / 190° C. of 10 g / 10 min to 40 g / 10 min.

[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 fabric 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 use of the bicomponent fiber as described above or the nonwoven as described above for making a top sheet, leg cover or back sheet in baby diapers, feminine hygiene products or adult incontinence products.

[0019] Surprisingly, it was 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 mechanical strength and softness. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0021] Figure 2 3 is a graph plotting the MD tensile strength of each example as a function of (density*basis weight) based on the test results in Table 3.

[0022] Figure 3 3 is a graph showing the TD tensile strength of each example 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] A "polymer" has two or more identical or different monomeric (mer) units. A "homopolymer" is a polymer having identical monomeric units. As used herein, the term "polymer" includes, but is not limited to, homopolymers, copolymers, terpolymers, and the like. As used herein, the term "polymer" 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., monomeric units). For example, the term "copolymer" includes the copolymerization reaction product of propylene and an α-olefin, such as ethylene or 1-hexene. A "terpolymer" is a polymer having three monomeric units that are different from each other. Thus, the term "copolymer" also includes terpolymers and tetrapolymers, such as copolymer products of a mixture 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 percent ethylene-derived units, a "propylene polymer" or "propylene copolymer" is a polymer or copolymer comprising at least 50 mole percent propylene-derived units, and so forth. For purposes of this 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 that 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 a polyethylene homopolymer, this means a polymer formed from ethylene monomers without 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 to 0.970g / cm 3 Ethylene homopolymers and ethylene copolymers with 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 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 a density of 0.910 g / cm 3 to 0.940g / cm 3 LLDPE can be produced using 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 in solution reactors using any of the disclosed catalysts.

[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 the fabric. The fibers produced by the spunbond process typically have a certain degree of molecular orientation imparted thereto.

[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. Fiber can be "monocomponent" or "bicomponent". Bicomponent fibers comprise 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 structural domains. The configuration of such bicomponent fibers can be, for example, a sheath / core arrangement, wherein one polymer is surrounded by the other, side by side (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). Fiber 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 (e.g., by passing the web of fibers through a heated calender or rolls).

[0038] Molecular weight moments and distributions (Mw, Mn, Mz, Mw / Mn, Mz / Mn, etc.), monomer / comonomer content (C2, C4, C6 and / or C8 and / or other, etc.), and g'(vis) were determined 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 principles and molecular weight determination methods and g' are provided. 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 referred to in this disclosure are determined according to the absolute determination method (such as mentioned in paragraphs

[0044] to

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

[0044] , a = 0.695 and K = 0.000579 (1-0.75 Wt) 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 immediately above-mentioned PCT publication (providing methyl groups / 1000 total carbons (CH3 / 1000TC)). Other parameters required can be found in the paragraphs mentioned in the WO 2019 / 246069 A1 publication, but for convenience some are included here: TCB at 145°C n = 1.500; I = 665 nm; dn / dc = 0.1048 mL / mg.

[0039] The density values ​​of the polymers were 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 under a load of 2.16 kg (sometimes referred to as I2); and the HLMI is measured at 190°C under a load of 21.6 kg (sometimes referred to as I2). 21 A sample of 5 to 6 g was loaded into the barrel of the instrument at 190°C and compressed manually. The material was then automatically compacted in the barrel by lowering all available weight onto the piston to remove any air bubbles. Data acquisition began after a 6-minute pre-melt period.

[0041] 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 from about 60% to about 85%, or from about 65% to about 85%, or from 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, and can be found, for example, in PCT patent application WO 1993 / 003093, published 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 from about 50,000 to about 800,000 g / mol, from about 60,000 to about 400,000 g / mol, from about 70,000 to about 200,000 g / mol, from about 75,000 to about 100,000 g / mol;

[0049] (d) a molecular weight distribution ("MWD," "Mw / Mn") of from about 1.5 to about 5.0, or from 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 Cozewith et al. and references cited therein, and in VerStrate et al., Macromolecules, Vol. 21, p. 3360 (1986) and references cited therein, each of which is 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 / 2.16 kg) 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 % 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 %. Thus, 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 comonomer 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 having one or more methyl, ethyl, or propyl substituents; 1-hexene; 1-hexene having one or more methyl, ethyl, or propyl substituents; 1-heptene; 1-heptene having one or more methyl, ethyl, or propyl substituents; 1-octene; 1-octene having one or more methyl, ethyl, or propyl substituents; 1-nonene; 1-nonene having 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 biscyclopentadienyl) 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 trade name EXCEED TM Those sold by 0019XC.

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

[0061] Second polyethylene

[0062] The second polyethylene can 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 0.940g / cm 3 to 0.970g / cm 3 , or 0.945g / cm 3 to 0.965g / cm 3 , or 0.950g / cm 3 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 from about 80,000 to about 1,000,000 g / mol, from about 100,000 to about 800,000 g / mol, from about 120,000 to about 400,000 g / mol, from 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 connection with the first polyethylene.

[0073] 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 combinations thereof (e.g. in the case of reactor or other bimodal HDPE compositions, 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 from PetroChina Fushun Petrochemical, including but not limited to those sold under the designation HDPE 2911FS.

[0075] Blending

[0076] The blends of the first and second polyethylenes 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-screw 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 apparatus. 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 transported 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 and second polyethylenes as described above.

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

[0082] In a preferred embodiment, the second polymer component comprises 55 to 95 weight percent of the first polyethylene and 5 to 45 weight percent of the second polyethylene, based on the total weight of the second polymer component. For example, the second polymer component comprises 60 to 80 weight percent of the first polyethylene and 20 to 40 weight percent of the second polyethylene. In this embodiment, the mechanical strength and softness of the bicomponent fiber and the nonwoven formed therefrom can be flexibly controlled, 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 elastomeric 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) polymer, 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 can be incorporated into the first polymer component and / or the second polymer component. Examples of additives can include, but are not limited to, stabilizers, antioxidants, fillers, colorants, nucleators, dispersants, release agents, slip agents, flame retardants, plasticizers, pigments, vulcanization or curing agents, vulcanization or curing accelerators, curing retardants, processing aids, tackifying resins, and any combination thereof. Other additives can include fillers and / or reinforcing materials, such as carbon black, clay, talc, calcium carbonate, mica, silicon dioxide, silicates, 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 made 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 fibers of the present invention are prepared by a melt-spinning process in which two polymer melts are supplied separately 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 spinneret outlet and the flow conditions of the core polymer fluid are strictly restricted to maintain the concentricity of the two components during spinning. Eccentric fiber production may include eccentric placement of the inner polymer channel and controlling 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 be combined with the concentric core-sheath component just before exiting the hole. Alternatively, the spinning concentric fibers may be deformed by passing through a hot edge.

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

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

[0092] The bicomponent fibers described herein can 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 can be formed directly into nonwovens of the bicomponent fibers described herein by spunbonding techniques.

[0095] In spunbond technology, spunbond fibers are produced conventionally such as by extruding molten polymers (such as using the melt-spinning conditions described above) from a large spinneret with thousands of holes or using a smaller spinneret in rows that for example contains 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 (" line ") or a porous forming belt to form a net. The net is then passed through a press roll, and then between the calendering rolls of heating, the raised areas on one of the rollers are bonded to form a nonwoven at 10% to 40% of the point covering its area.

[0096] The extruder can be any extruder conventionally used in this area, for example 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 rolls can be any calendering rolls commonly used in the art. Calendering rolls typically include an upper roll and a lower roll. During bonding using the calendering rolls, the temperature of the upper roll is typically higher than that of the lower roll. The bonding temperature is represented by the average temperature of the upper and lower rolls. In various embodiments, the bonding temperature can be 100-180°C, e.g., 110-170°C, 110-150°C, 110-130°C, 120-160°C, or 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 smaller, or about 5g / m 2 About 120g / m 2 , or about 5g / m 2 to 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 from 60% to 80% by weight of the first polyethylene; and from 20% to 40% by weight 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 HOM is in g and density is in 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 associated claims expressing the amounts of ingredients, properties such as molecular weight, reaction conditions, etc. should be understood as being modified in all instances 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 ​​that may vary depending on the desired properties sought to be obtained by embodiments 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 construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0105] This paper proposes one or more illustrative embodiments comprising one or more inventive elements. 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 embodiments comprising one or more elements of the present invention, in order to achieve the developer's goal, many specific decisions must be made to achieve these, such as complying with system-related, business-related, government-related and other constraints, which vary 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 this 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 impurity.

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

[0111] 55 to 95 wt% of a first polyethylene comprising 70.0 to 100.0 wt% of units derived from ethylene and 0 to 30.0 wt% of units derived from C3-C 20 α-olefin units and having a range of 0.905 to 0.926 g / cm 3 A density of 1000 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 and a melt index at 2.16 kg / 190° C. of 10 g / 10 min to 40 g / 10 min.

[0113] 2. The bicomponent fiber of embodiment 1, wherein the second polymer component comprises 60% to 80% by weight of the first polyethylene; and 20% to 40% by weight 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 is 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 breadth 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] Contains 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 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 is 0.940g / cm 3 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 from 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] The sheath comprises a second polymer component comprising, based on the total weight of the second polymer component:

[0137] 70 wt% of a first polyethylene comprising 88 to 92 wt% of units derived from ethylene and 8 to 12 wt% of units derived from hexene and having a viscosity of 0.918 g / cm 3 A density of 19 g / 10 min at 2.16 kg / 190° C., a melt index of 2.9, a molecular weight distribution Mw / Mn, 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 density and a melt index of 21 g / 10 min 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 to 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 HOM is in g and density is in 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. The method for preparing a nonwoven fabric according to any one of embodiments 9 to 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 covering or back sheet in baby diapers, feminine hygiene products or adult incontinence products. DETAILED DESCRIPTION

[0153] In order to promote 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 polyethylenes 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 through spunbond process. Specifically, nonwovens are produced on 1.6 meters of bicomponent production lines at Shanghai Jingfa. Polymer, after passing through an extruder, is extruded into molten polymer by a spinneret to produce molten fibers. After leaving the spinneret, the molten fibers are quenched by a cross-flow air quenching system, then pulled out from the spinneret and attenuated by high-speed air. The filaments formed in this way are collected on a forming belt to form a web. The web is then passed through a press roller to form a nonwoven.

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

[0162]

[0163]

[0164] Figure 1 The following is a graph showing the HOM of each example as a function of (density*basis weight) plotted based on the test results in Table 3. Surprisingly, when normalized to (density*basis weight), Example F5 (30% HDPE 2911FS + 70% EXCEED0019) exhibits the best softness, as reflected by 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 figure shows the MD tensile strength of each example as a function of (density*basis weight) according to the test results in Table 3. It is surprisingly found that when normalized to (density*basis weight), Example F5 (30% HDPE 2911FS + 70% EXCEED 0019) has the best strength, as reflected in its MD tensile strength being >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 The TD tensile strength of each example is plotted as a function of (density*basis weight) based on the test results in Table 3. Surprisingly, when normalized to (density*basis weight), Example F5 (30% HDPE 2911FS + 70% EXCEED 0019) has the best strength, as reflected in its TD tensile strength being >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 at 50x magnification to observe the size of the optical fiber: Cut a small piece of fiber and place it on glass. Drop immersion oil on the sample and wait for the sample to be completely immersed. Place a coverslip 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 FX 3820 circular sample cutter quickly and accurately cuts circular specimens of a specific fixed area to determine the area weight. This cutter is particularly suitable for woven, nonwoven and knitted textiles, carpets, paper, film, foam and board materials. The cutter can be used to prepare samples for basis weight tests. The sample base is 3 squares 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, with reference to 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 x 250 mm). The load is measured by a load cell, and the deformation is measured by the crosshead position. Because rectangular specimens are used, no additional extensometer is used to measure elongation. The tensile properties of a material determine its strength and elongation under load. When a load is applied to a nonwoven, it stretches, yields, stretches further, and eventually breaks.

[0181] By plotting load against elongation, we obtain the so-called "stress-strain curve." From this curve, we can create a graph 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, referencing 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 the material specimen into a parallel-edge slot. A digital voltmeter (DVM) indicates the resistance directly in grams. Two beams (100 gram and 1000 gram) can be quickly interchanged, providing versatility for testing different materials. The instrument automatically detects the beam 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 will be 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. Furthermore, no limitation is intended to the details of construction or design shown herein, except as described in the claims below. It is therefore apparent that the specific illustrative embodiments disclosed above may be changed, combined, or modified, and all such variations are considered within the scope and spirit of the present invention. The invention disclosed herein illustratively 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 vary to some extent.

[0188] Whenever a numerical range with a lower limit and an upper limit is disclosed, any value and any included range falling within the range is specifically disclosed. In particular, each value range 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 value and range contained within the wider range of values. Similarly, when multiple ranges are disclosed (e.g., 1-100 or 10-90, e.g., 30 to 75), the range from any disclosed lower end to any disclosed upper end (e.g., 10-75) is specifically encompassed.

[0189] Also, 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, the first polymer component being polypropylene; and The sheath comprises a second polymer component comprising, based on the total weight of the second polymer component: 70 wt% of a first polyethylene, wherein the first polyethylene is EXCEED TM 0019XC; and 30 wt% of a second polyethylene, wherein the second polyethylene is HDPE 2911FS; The weight ratio of the first polymer component to the second polymer component is 50:

50.

2. The bicomponent fiber of claim 1, wherein the bicomponent fiber is a bicomponent long fiber.

3. A nonwoven comprising the bicomponent fiber according to any one of claims 1 to 2.

4. The nonwoven fabric according to claim 3, wherein the basis weight of the nonwoven fabric is 5 g / m 2 Up to 50 g / m 2 .

5. The nonwoven according to claim 3 or 4, wherein the nonwoven is formed by a spunbond process.

6. The nonwoven fabric according to claim 3 or 4, wherein the nonwoven fabric has one or more of the following properties: HOM<-0.636*density+4.9493, where HOM is in g and density is in 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 .

7. The method for preparing a nonwoven fabric according to any one of claims 3 to 6, 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.

8. Use of the bicomponent fiber according to any one of claims 1 to 2 or the nonwoven according to any one of claims 3 to 6 for producing a top sheet, leg covering or back sheet in baby diapers, feminine hygiene products or adult incontinence products.

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