Use of a polymer composition in the manufacture of soft nonwoven fabrics

Abstract

Use of a polymer composition comprising a first propylene polymer A and a second propylene polymer B for producing crimped multicomponent fibers having a side-by-side cross-sectional configuration.

Description

Technical Field

[0001] This invention relates to the use of polymer compositions for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration. Background Technology

[0002] Today, polypropylene fibers or polypropylene nonwoven fabrics are used in a variety of applications, including filter media, diapers, hygiene products, sanitary napkins, panty liners, adult incontinence products, protective clothing materials, bandages, surgical drapes, surgical gowns, surgical clothing, and packaging materials. Polypropylene nonwoven fabrics are widely used as hygiene materials due to their excellent properties, such as breathability and softness. However, further improvements in softness, bulkiness, and mechanical strength are needed.

[0003] High-loft layers can help provide nonwoven fabrics with high softness, as desired in hygiene products such as diapers and sanitary napkins. Nonwoven fabrics comprising high-loft layers based on crimped fibers are known in the art. Typically, crimped multicomponent fibers comprise two or more polymers with different physical properties, which are asymmetrically distributed across their cross-section. Most commonly, they are arranged side-by-side. This configuration causes the fibers to crimp when subjected to physical stress, such as in the case of spunbond fibers, during fiber drawing and quenching.

[0004] For example, EP3246443A1 discloses a fabric comprising at least one high-loft nonwoven fabric layer having crimped multicomponent fibers, characterized in that a first component of the multicomponent fibers comprises a first polymer A, and a second component of the multicomponent fibers comprises a blend of the first polymer A and a second polymer B, wherein the melt flow rate of polymer A differs from that of polymer B by at least 25%, and wherein the second component comprises at least 15% by weight of polymer B. A method for manufacturing SMS-type products is also claimed.

[0005] EP3246444 discloses a method for manufacturing a high-loft nonwoven web comprising crimped multicomponent fibers, the method comprising laying the fibers on a spun yarn and pre-consolidating the fibers after laying using one or more pre-consolidation rollers to form a pre-consolidated web, characterized in that the first component of the fibers comprises a PP homopolymer and the second component of the fibers comprises a PP / PE copolymer, wherein the pre-consolidation rollers are operated at a certain temperature and contact force.

[0006] According to EP2343406, crimped conjugated fibers and nonwoven fabrics containing these fibers are disclosed. This allows for the crimping of fibers when using multi-component fibers, where the two components have similar melt flow rates and melting points, but differ in the ratio of their Z-average molecular weight distribution to their weight-average molecular weight distribution.

[0007] However, despite these various improvements, there is still a need to optimize and diversify the polymers that can be used to manufacture such materials. The object of this invention is to provide a method for selecting and using polypropylene compositions for the production of nonwoven fabric sheets comprising fibers with improved and controllable crimp, and nonwoven fabrics with higher bulk compared to these known products while maintaining other desired properties. Summary of the Invention

[0008] The inventors conducted extensive research and discovered that the aforementioned properties can be achieved by using specific polypropylene compositions. Surprisingly, it was found that different customized fiber curvatures can be formed using the polypropylene compositions according to the invention, which dominates the formation of the crimped portion. Within a certain range of curvatures, the softness of the nonwoven fabric made from the fibers is optimized.

[0009] Therefore, the present invention provides:

[0010] The polymer composition comprising a first propylene polymer A and a second propylene polymer B is used for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein

[0011] (i) The first propylene polymer A and the second propylene polymer B are distributed side by side on the cross-section of the fiber.

[0012] (ii) The mass ratio of the first propylene polymer A to the second propylene polymer B [A:B] is in the range of 10:90 to 90:10, and

[0013] (iii) The absolute value of the difference between the crystallization temperature [Tc(A)] of propylene polymer (A) and the crystallization temperature [Tc(B)] of propylene polymer (B) as determined by ISO 11357 at a scan rate of 10 °C / min is in the range of 6 to 30 °C.

[0014] A preferred feature of the crimped multicomponent fiber having a side-by-side cross-sectional configuration is that the interface line between the two propylene polymers (A) and (B) contained in the radial plane of the fiber is curved, and its curvature (c) is defined by the quotient (h) / (b) and is between 0.05 and 0.25, where (b), i.e. "baseline length", is the length of the imaginary straight baseline connecting the two endpoints of the curved interface line, and (h), i.e. "bow height", is the distance between the crest of the curved interface line and the baseline.

[0015] The radial plane is perpendicular to the longitudinal direction of the fiber, and therefore forms a 90° angle with the longitudinal axis of the fiber at a given location. The shape of the radial interface line, as defined in a preferred embodiment of the invention, is the shape of the interface line contained within this plane. This is to distinguish it from the profile of an interface along the longitudinal direction or diagonal lines, which naturally curve to a certain extent according to geometric relationships within the crimped fiber. The curvature of the radial interface line as defined in this invention is geometrically independent of the fiber crimp.

[0016] In a preferred embodiment, the curvature (c) of the radial interface line is between 0.08 and 0.22, preferably between 0.10 and 0.20, and more preferably between 0.12 and 0.18. When the curvature is within these ranges, very advantageous curling behavior is observed in many cases.

[0017] In a preferred embodiment, the crimped multicomponent fibers produced using the polymer composition defined in this invention are spunbond fibers, which form a nonwoven fabric sheet, preferably a spunbond fabric sheet. This sheet may include, in addition to other fibers such as linear monocomponent fibers, bicomponent fibers conforming to the definition of this invention, or be composed of bicomponent fibers conforming to the definition of this invention. Because the millions of fibers that actually form a nonwoven material are never always identical, the term "composed of" must be understood as follows: the requirement is met when all the fibers produced are identical, and the vast majority of the fibers (e.g., more than 80% of the fibers, preferably more than 90% of the fibers) exhibit the characteristics of this invention.

[0018] definition

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While any methods and materials similar to or equivalent to those described herein may be used in practice to test the invention, preferred materials and methods are described herein. In describing and claiming protection for this invention, the following terms will be used according to their definitions.

[0020] Unless otherwise explicitly stated, the terms "a," "an," etc., are used to refer to one or more. According to the invention, the expression "propylene homopolymer" refers to polypropylene composed essentially of at least 99.0 mol%, more preferably at least 99.5 mol%, still more preferably at least 99.8 mol%, for example at least 99.9 mol%, of propylene units. In another embodiment, only propylene units are detectable, i.e., only propylene has been polymerized. Therefore, the polypropylene homopolymer may contain up to 1.0 wt% of C2 or C4 to C6. 10 The α-olefin comonomer, preferably up to 0.5% by weight, but more preferably up to 0.2% by weight, for example up to 0.1% by weight, is C2 or C4 to C6. 10α-olefin comonomer.

[0021] Such comonomers can be selected from, for example, ethylene, 1-butene, 1-hexene, and 1-octene. If a comonomer is available, ethylene is preferred.

[0022] In another embodiment, only propylene units can be detected, meaning only propylene has been polymerized. In this case, the amount of comonomer is 0.0% by weight.

[0023] Propylene / α-olefin random copolymers are copolymers of propylene monomer units and comonomer units, preferably selected from ethylene and C4 to C12 α-olefins, wherein the comonomer units are randomly distributed along the polymer chain. Propylene random copolymers may include comonomer units from one or more comonomers with different carbon atomic masses. Unless otherwise specified, the following quantities are given in mole percent.

[0024] Propylene homopolymers and propylene / α-olefin random copolymers typically have only one glass transition temperature. Detailed Implementation

[0025] This invention relates to the use of a specific polymer composition comprising a first propylene polymer A and a second propylene polymer B for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration. The polymer composition, the first propylene polymer A, and the second propylene polymer B are described in more detail below.

[0026] Essentially, in the polymer composition according to the invention, the mass ratio [A:B] of the first propylene polymer A to the second propylene polymer B is in the range of 10:90 to 90:10, preferably in the range of 20:80 to 80:20, more preferably in the range of 25:75 to 60:40, and the absolute value of the difference between the crystallization temperature [Tc(A)] of the propylene polymer (A) and the crystallization temperature [Tc(B)] of the propylene polymer (B) is in the range of 6 to 30°C, preferably in the range of 6 to 20°C, more preferably in the range of 7 to 15°C, for example in the range of 7 to 14°C.

[0027] First propylene polymer A

[0028] The first propylene polymer (A) may be a propylene homopolymer or a propylene / α-olefin random copolymer.

[0029] In the case where the first propylene polymer (A) is a random copolymer of propylene and α-olefins, the first propylene polymer (A) may include monomers that can be copolymerized with propylene, such as comonomers like ethylene and / or C4 to C8 α-olefins, particularly ethylene and / or C4 to C6 α-olefins, such as 1-butene and / or 1-hexene. Preferably, the first propylene polymer (A) according to the invention includes monomers that can be copolymerized with propylene, particularly consisting of monomers that can be copolymerized with propylene, selected from the group consisting of ethylene, 1-butene, and 1-hexene. More specifically, the first propylene polymer (A) of the invention includes units derived from ethylene and / or 1-butene in addition to propylene. In a preferred embodiment, the first propylene polymer (A) includes only units derived from ethylene and propylene.

[0030] Preferably, the melt flow rate (MFR2, 230°C, 2.16 kg, ISO 1133) of the first propylene polymer (A) is in the range of 15 to 120 g / 10 min, more preferably in the range of 15 to 60 g / 10 min, and even more preferably in the range of 15 to 40 g / 10 min.

[0031] Further preferably, the molecular weight distribution (Mw / Mn) of the first propylene polymer (A) (measured by size exclusion chromatography according to ISO 16014) is in the range of 2.5 to 10.0, more preferably in the range of 3.5 to 8.5, and more preferably in the range of 4.0 to 7.5. In a particular embodiment of the invention, the first propylene polymer (A) is preferably a crystalline propylene homopolymer. The term "crystalline" indicates that the propylene homopolymer has a relatively high melting temperature. Therefore, in this invention, unless otherwise stated, the propylene homopolymer is considered to be crystalline. In this embodiment, the first propylene polymer (A), as a propylene homopolymer, preferably has a melting temperature Tm measured by differential scanning calorimetry (DSC, ISO 11357-1&-2) in the range of 150°C to 164°C, preferably in the range of 155°C to 162°C, in the range of 90°C to 135°C, preferably in the range of 100°C to 130°C, more preferably in the range of 105°C to 125°C, and a comonomer content of <1.0% by weight, preferably in the range of 0.1% to 0.7% by weight.

[0032] In another specific embodiment of the invention, the first propylene polymer (A) is preferably a propylene / α-olefin random copolymer, having a comonomer content in the range of 1.0 to 5.5% by weight, preferably in the range of 1.2 to 5.0% by weight, and more preferably in the range of 1.5 to 4.2% by weight. In this embodiment, the first propylene polymer (A) as a propylene / α-olefin random copolymer preferably has a melting temperature Tm measured by differential scanning calorimetry (DSC, ISO 11357-1&-2) in the range of 142°C to 155°C, preferably in the range of 145°C to 152°C, and a crystallization temperature Tc (DSC, ISO 11357-1&-2) in the range of 80°C to 125°C, preferably in the range of 85°C to 122°C, and more preferably in the range of 90 to 120°C.

[0033] In another preferred embodiment, the first propylene polymer (A) as a propylene / α-olefin random copolymer preferably has a molecular weight distribution (Mw / Mn) in the range of 4.5 to 10.0, more preferably in the range of 5.0 to 9.0, and more preferably in the range of 5.5 to 8.5 (measured by size exclusion chromatography according to ISO 16014).

[0034] Further preferably, the first propylene polymer (A) has a xylene cold soluble content in the range of 1.5 to 10.0% by weight, more preferably in the range of 1.5 to 8.0% by weight.

[0035] The xylene cold soluble content (XCS) further indicates that the first propylene polymer (A) preferably does not contain any elastomeric polymer components, such as ethylene propylene rubber. In other words, the first propylene polymer (A) should not be a multiphase polypropylene, i.e., a system consisting of a polypropylene matrix in which an elastomeric phase is dispersed. Such systems are characterized by a relatively high xylene cold soluble content.

[0036] Second propylene polymer B

[0037] The second propylene polymer (B) can be a propylene homopolymer or a propylene / α-olefin random copolymer.

[0038] In the case where the second propylene polymer (B) is a random copolymer of propylene and α-olefins, the second propylene polymer (B) may include monomers that can be copolymerized with propylene, such as comonomers like ethylene and / or C4 to C8 α-olefins, particularly ethylene and / or C4 to C6 α-olefins, such as 1-butene and / or 1-hexene. Preferably, the second propylene polymer (B) according to the invention comprises monomers that can be copolymerized with propylene, particularly consisting of monomers that can be copolymerized with propylene, selected from the group consisting of ethylene, 1-butene, and 1-hexene. More specifically, the second propylene polymer (B) of the invention also includes units derived from ethylene and / or 1-butene in addition to propylene. In a preferred embodiment, the second propylene polymer (B) comprises only units derived from ethylene and propylene.

[0039] Preferably, the melt flow rate (MFR2, 230°C, 2.16 kg, ISO 1133) of the second propylene polymer (B) is in the range of 15 to 120 g / 10 min, more preferably in the range of 15 to 60 g / 10 min, and even more preferably in the range of 15 to 40 g / 10 min.

[0040] Further preferably, the molecular weight distribution (Mw / Mn) of the second propylene polymer (B) (measured by size exclusion chromatography according to ISO 16014) is in the range of 2.5 to 10.0, more preferably in the range of 3.5 to 8.5, and more preferably in the range of 4.0 to 7.5.

[0041] In a particular embodiment of the invention, the second propylene polymer (B) is preferably a crystalline propylene homopolymer. The term "crystalline" indicates that the propylene homopolymer has a relatively high melting temperature. Therefore, in the present invention, unless otherwise stated, the propylene homopolymer is considered to be crystalline. In this embodiment, the second propylene polymer (B) as the propylene homopolymer preferably has a melting temperature Tm measured by differential scanning calorimetry (DSC, ISO 11357-1&-2) in the range of 150°C to 164°C, preferably in the range of 155°C to 162°C, in the range of 90°C to 135°C, preferably in the range of 100°C to 130°C, more preferably in the range of 105°C to 125°C, in the range of DSC, ISO 11357-1&-2, and a comonomer content of <1.0 wt%, preferably in the range of 0.1 to 0.7 wt%.

[0042] In another specific embodiment of the invention, the second propylene polymer (B) is preferably a propylene / α-olefin random copolymer, having a comonomer content in the range of 1.0 to 5.5% by weight, preferably in the range of 1.2 to 5.0% by weight, and more preferably in the range of 1.5 to 4.2% by weight. In this embodiment, the second propylene polymer (B) as a propylene / α-olefin random copolymer preferably has a melting temperature Tm measured by differential scanning calorimetry (DSC, ISO 11357-1&-2) in the range of 142°C to 155°C, preferably in the range of 145°C to 152°C, and a crystallization temperature Tc (DSC, ISO 11357-1&-2) in the range of 80°C to 125°C, preferably in the range of 85°C to 120°C, and more preferably in the range of 90 to 115°C.

[0043] In another preferred embodiment, the second propylene polymer (B) as a propylene / α-olefin random copolymer preferably has a molecular weight distribution (Mw / Mn) in the range of 4.5 to 10.0, more preferably in the range of 5.0 to 9.0, and more preferably in the range of 5.5 to 8.5 (measured by size exclusion chromatography according to ISO 16014).

[0044] Further preferably, the second propylene polymer (B) has a xylene cold soluble content in the range of 1.5 to 10.0% by weight, more preferably in the range of 1.5 to 8.0% by weight.

[0045] The xylene cold soluble content (XCS) further indicates that the second propylene polymer (B) preferably does not contain any elastomeric polymer components, such as ethylene propylene rubber. In other words, the first propylene polymer (A) should not be a multiphase polypropylene, i.e., a system consisting of a polypropylene matrix in which an elastomeric phase is dispersed. Such systems are characterized by a relatively high xylene cold soluble content.

[0046] The propylene polymers of the present invention, comprising a first propylene polymer (A) and a second propylene polymer (B), which satisfy the requirements mentioned above, can be produced by polymerization processes known in the prior art. Commercially available propylene polymers can be used, examples including HG475FB manufactured and sold by Borealis Polyolefin.

[0047] Preferably, the propylene polymers (A and B) according to the invention are produced in the presence of the following:

[0048] (a) A Ziegler-Natta catalyst comprising a compound of a Group 4 to 6 transition metal from IUPAC, a Group 2 metal compound, and an internal donor, wherein the internal donor is a non-phthalic acid compound, more preferably a non-phthalic acid ester, and still more preferably a non-phthalic acid diester.

[0049] (b) Optional co-catalysts, and

[0050] (c) Optional external donor.

[0051] Polypropylene homopolymers that meet requirement e) can be produced using Ziegler-Natta catalysts with non-phthalic acid compounds as internal donors.

[0052] Preferably, the internal donor is selected from optionally substituted malonates, maleates, succinates, glutarates, cyclohexene-1,2-dicarboxylate esters, benzoates and their derivatives and / or mixtures, and preferably, the internal donor is citrate.

[0053] Alternatively or alternatively, the molar ratio of the co-catalyst to the external donor (ED) [Co / ED] is 5 to 45.

[0054] In view of the above, it is preferable that the polypropylene polymer does not contain phthalic acid compounds and their corresponding decomposition products, i.e. phthalate esters, which are typically used as internal donors of Ziegler-Natta catalysts (e.g., fourth-generation Ziegler-Natta catalysts).

[0055] In the context of this invention, the term "free of" phthalic acid compounds means that phthalic acid compounds are undetectable in polypropylene homopolymers and that corresponding decomposition products derived from the catalyst used are not present at all.

[0056] According to the present invention, the term "phthalic acid compound" refers to phthalic acid (CAS No. 88-99-3), its monoesters and diesters with aliphatic, alicyclic and aromatic alcohols, and phthalic anhydrides.

[0057] As noted above, the polypropylene polymer of the present invention may optionally be produced using a sequential polymerization process.

[0058] The term "sequential polymerization system" indicates that polypropylene polymers are produced in at least two reactors connected in series. Therefore, a sequential polymerization system includes at least a first polymerization reactor and a second polymerization reactor, and optionally a third polymerization reactor. The term "polymerization reactor" should indicate the location of the main polymerization reaction. Therefore, if the process consists of two polymerization reactors, this definition does not preclude the inclusion of a prepolymerization step, for example, in a prepolymerization reactor. The term "consisting of" is merely a closed-ended statement referring to the main polymerization reactor.

[0059] Preferably, in any case, the first polymerization reactor is a slurry reactor and can be any continuous or simple stirred batch reactor or loop reactor operated in bulk or slurry mode. Bulk refers to polymerization carried out in a reaction medium comprising at least 60% (w / w) monomer. According to the invention, the slurry reactor is preferably a (bulk) loop reactor.

[0060] The optional second polymerization reactor can be a slurry reactor as defined above, preferably a loop reactor or a gas-phase reactor.

[0061] The optional third polymerization reactor is preferably a gas-phase reactor.

[0062] Suitable sequential polymerization processes are known in the art.

[0063] The preferred multi-stage process is the "loop-gas phase" process, such as the one developed by Borealis (known as...). (Technology), for example, as described in patent documents such as EP 0 887 379, WO 92 / 12182, WO 2004 / 000899, WO 2004 / 111095, WO 99 / 24478, WO 99 / 24479 or WO 00 / 68315.

[0064] Another suitable slurry-gas phase process is Basell's Process.

[0065] Selecting polymerization conditions in a certain way to obtain the desired properties of polypropylene polymers is within the capabilities of those skilled in the art.

[0066] polymer composition

[0067] In a particularly preferred embodiment of the invention, the first propylene polymer A and the second propylene polymer B are different, and at least one propylene polymer (A and B) is viscous cracked.

[0068] Therefore, in this embodiment, preferably, the melt flow rate (230°C / 2.16 kg, ISO 1133) of the propylene polymer (A or B) before viscosity reduction cracking is much lower, for example, 0.5 to 50 g / 10 min. For example, the melt flow rate (230°C / 2.16 kg) of the propylene polymer (A or B) before viscosity reduction cracking is 1.0 to 45 g / 10 min, for example, 1.5 to 40 g / 10 min.

[0069] Preferably, the ratio of the final MFR after viscosity-reducing cracking to the initial MFR before viscosity-reducing cracking is...

[0070] [Final MFR] / [Initial MFR]>5

[0071] Preferably, the polypropylene polymer (A or B) has undergone viscosity reduction cracking, and the viscosity reduction cracking ratio [final MFR2 (230°C / 2.16kg) / initial MFR2 (230°C / 2.16kg)] is greater than 5 to 50.

[0072] "Final MFR2 (230℃ / 2.16kg)" is the MFR2 (230℃ / 2.16kg) of the polypropylene polymer (A or B) after viscosity reduction cracking, and "Initial MFR2 (230℃ / 2.16kg)" is the MFR2 (230℃ / 2.16kg) of the polypropylene polymer (A or B) before viscosity reduction cracking.

[0073] More preferably, the polypropylene polymer (A or B) has been subjected to viscosity reduction cracking, with a viscosity reduction cracking ratio [final MFR2 (230°C / 2.16 kg) / initial MFR2 (230°C / 2.16 kg)] of 8 to 25.

[0074] Even more preferably, the polypropylene polymer (A or B) has been subjected to viscosity reduction cracking with a viscosity reduction cracking ratio [final MFR2 (230°C / 2.16 kg) / initial MFR2 (230°C / 2.16 kg)] of 10 to 20.

[0075] Preferred mixing apparatuses for viscosity reduction cracking are known to those skilled in the art and can be selected from, for example, discontinuous and continuous kneaders, twin-screw extruders and single-screw extruders with special mixing sections, and co-kneaders.

[0076] The viscosity-reducing cracking step according to the present invention is carried out using peroxides or mixtures of peroxides, or using hydroxylamine esters or thiols as free radical sources (viscosity-reducing cracking agents), or by pure thermal degradation.

[0077] Typical peroxides suitable as viscosity-reducing cracking agents are 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane (DHBP) (e.g., sold under the trade names Luperox 101 and Trigonox 101), 2,5-dimethyl-2,5-bis(tert-butylperoxy)hexyn-3 (DYBP) (e.g., sold under the trade names Luperox 130 and Trigonox 145), dicumyl peroxide (DCUP) (e.g., sold under the trade names Luperox DC and Perkadox BC), di-tert-butyl peroxide (DTBP) (e.g., sold under the trade names Trigonox B and Luperox Di), tert-butyl cumyl peroxide (BCUP) (e.g., sold under the trade names Trigonox T and Luperox 801), and bis(tert-butylperoxyisopropyl)benzene (DIPP) (e.g., sold under the trade names Perkadox 14S and Luperox DC).

[0078] The appropriate amount of peroxide to be used according to the present invention is known in principle to those skilled in the art and can be easily calculated based on the amount of propylene homopolymer to be subjected to viscous cracking, the MFR2 (230°C) value of the propylene homopolymer to be subjected to viscous cracking, and the desired target MFR2 (230°C) of the product to be obtained.

[0079] Therefore, the typical amount of the peroxide viscosity-reducing cracking agent is 0.005 to 0.5% by weight, more preferably 0.01 to 0.2% by weight, based on the total amount of the polypropylene polymer (A or B) used. Typically, the viscosity-reducing cracking according to the invention is carried out in an extruder, thereby achieving an increase in melt flow rate under suitable conditions. During viscosity-reducing cracking, the higher molar mass chains of the starting product are statistically broken more frequently than the lower molar mass molecules, resulting in an overall decrease in average molecular weight and an increase in melt flow rate as described above.

[0080] After viscosity reduction cracking, the polypropylene polymer (A or B) according to the present invention is preferably in the form of granules or pellets. The polypropylene polymer (A or B) of the present invention is preferably used in spunbond fiber processes in the form of granules or pellets.

[0081] In a particular embodiment of the invention, only one of the propylene polymers (A and B) is viscous-reducing and cracked, and the M between propylene polymers A and B is... z / M w The absolute value of the difference is 0.3 to 10.0, preferably 0.5 to 8.5, more preferably 1.0 to 5.5, and even more preferably 1.5 to 4.0.

[0082] In another embodiment of the invention, both propylene polymers (A and B) are viscous-reduced and cracked, and the M between propylene polymers A and B is...z / M w The absolute value of the difference is between 0.0 and 0.3, preferably between 0.00 and 0.25, more preferably between 0.00 and 0.22, and even more preferably between 0.00 and 0.15.

[0083] In another preferred embodiment of the invention, at least one of propylene polymers A and B is nucleated, and the amount of nucleating agent is in the range of 0.01 to 5000 ppm based on the total amount of nucleated propylene polymers, preferably in the range of 0.05 to 4500 ppm, more preferably in the range of 0.1 to 4000 ppm, for example 0.15 to 3000 ppm.

[0084] When propylene polymer A or B is nucleating, it may include a nucleating agent, preferably an α-nucleating agent. The α-nucleating agent is preferably selected from the group consisting of the following:

[0085] (i) Salts of monocarboxylic and polycarboxylic acids, such as sodium benzoate or aluminum tert-butylbenzoate, and

[0086] (ii) Dibenzyl sorbitol (e.g., 1,3:2,4-dibenzyl sorbitol) and C1-C8-alkyl-substituted dibenzyl sorbitol derivatives, such as methyl dibenzyl sorbitol, ethyl dibenzyl sorbitol, or dimethyl dibenzyl sorbitol (e.g., 1,3:2,4-di(methyl benzyl)sorbitol), or substituted nonitol derivatives, such as 1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, and

[0087] (iii) Salts of phosphate diesters, such as sodium 2,2'-methylene-bis(4,6'-di-tert-butylphenyl)phosphate or aluminum bis[2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate] (or simply aluminum bis[2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate]), and

[0088] (iv) Vinylcycloalkane polymers and vinylalkane polymers (discussed in more detail below), and

[0089] (v) Its mixture.

[0090] Such additives are generally commercially available and described, for example, in Hans Zweifel's "Plastic Additives Handbook", pp. 871-873, 5th edition, mid-2001.

[0091] Preferably, propylene polymer A or B contains up to 5.0% by weight of an α-nucleating agent. In a preferred embodiment, the propylene homopolymer contains 0.01 to 5000 ppm, preferably 0.05 to 4500 ppm, more preferably 0.1 to 4000 ppm, and most preferably 0.15 to 3000 ppm of an α-nucleating agent, particularly selected from the group consisting of dibenzyl sorbitol (e.g., 1,3:2,4-dibenzyl sorbitol), dibenzyl sorbitol derivatives, preferably dimethyl dibenzyl sorbitol (e.g., 1,3:2,4-di(methylbenzyl)sorbitol) or substituted nonitol derivatives, such as 1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol, sodium 2,2'-methylenebis(4,6,-di-tert-butylphenyl)phosphate, vinyl cycloalkane polymers, vinyl alkane polymers, and mixtures thereof.

[0092] In a particularly preferred embodiment of the invention, the first propylene polymer A is a propylene homopolymer, and the second propylene polymer B is a propylene random copolymer. In this case, the amount of the first propylene polymer A is preferably less than the amount of the second propylene polymer B. More preferably, the mass ratio [A:B] of the first propylene polymer A (e.g., propylene homopolymer) and the second propylene polymer B (e.g., propylene / α-olefin random copolymer) is in the range of 10:90 to 50:50, preferably in the range of 20:80 to 45:55, and more preferably in the range of 25:85 to 45:55.

[0093] The polymer compositions of the present invention, as defined above, are used for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration. Preferably, the multicomponent fibers are bicomponent fibers consisting of first and second components. In the use of the present invention, the first and second components are arranged in a side-by-side arrangement. The term "side-by-side" arrangement includes various variations, such as, for example, hollow side-by-side arrangement, eccentric hollow side-by-side arrangement, and side-by-side multi-leaf arrangement.

[0094] The crimped bicomponent fiber is typically helical crimped. In one embodiment, when measured according to Japanese Standard JIS L-1015-1981 at a pre-stretch load of 2 mg / denier, the average number of crimps in the crimped bicomponent fiber is in the range of at least 7 crimps / cm, preferably at least 10 crimps / cm. When measured according to JIS L-1015-1981 at a pre-stretch load of 2 mg / denier, the crimp amplitude is preferably less than 0.30 mm, and preferably between 0.20 and 0.30 mm.

[0095] The fiber preferably has a linear mass density in the range of 1.0 to 2.2 denier, and more preferably in the range of 1.2 to 2.0 denier.

[0096] The basis weight of each spunbond layer in a multilayer sheet can be between 4 and 40 g / m². 2 Between 5 and 25 g / m 2 between.

[0097] The density of the nonwoven fabric sheet is preferably less than 60 mg / cm³. 3 And preferably less than 50 mg / cm³ 3 These are typical values ​​for high-loft nonwoven fabrics with crimped fibers. In contrast, standard-loft nonwoven fabrics with uncrimped fibers typically have values ​​higher than 60 to 70 mg / cm³. 3 The density.

[0098] According to WSP.120.6, option A, at 2500mm 2 When measured at a pressure of 0.5 kPa on the plate, for 20 g / m 2 The basis weight is greater than or equal to the thickness of the nonwoven fabric sheet, preferably greater than 0.35 mm, more preferably greater than 0.37 mm.

[0099] The methods and processes for producing crimped multicomponent fibers with side-by-side cross-sectional arrangements in the form of spunbond nonwoven fabric sheets using the polymer compositions of the present invention are defined as follows:

[0100] The spunbond nonwoven fabric sheet is made in an extruder comprising at least two spinnerets, drawing channels, and moving belts, wherein fibers are spun in the spinnerets, drawn in the drawing channels, and laid on the moving belts, wherein the equipment includes a pressurized process air chamber from which process air is guided through the drawing channels to draw the fibers.

[0101] The drawing channel may include more than one segment. The drawing channel, or a segment thereof, may narrow with increasing distance from the spinneret. In one embodiment, the convergence angle can be adjusted. The device can form a closed aggregate that extends at least between the process air inlets to the end of the drawing channel, thus preventing air from entering from the outside and preventing any supplied process air from escaping to the outside. In one embodiment, the device includes at least one diffuser disposed between the end of the drawing channel and the moving belt.

[0102] The pressure difference between ambient pressure and the pressure inside the process air chamber is typically higher than 2000 Pascals. It has been observed that, within a reasonable range, higher chamber pressures tend to result in curvature within the desired range and have a positive effect on coiling. In a preferred embodiment, the chamber pressure is therefore higher than 2500 Pascals, more preferably higher than 3000 Pascals, or even higher than 3500 Pascals. For process stability, the upper limit of the chamber pressure is preferably less than 6000 Pascals and more preferably less than 5000 Pascals.

[0103] Suitable process air temperatures are typically above 10°C. However, it has been observed that, across a reasonable range, higher process air temperatures tend to result in curvature within the desired range and have a positive effect on crimping. Therefore, in a preferred embodiment, the process air temperature is above 20°C, more preferably above 25°C. At the upper limit, the process air temperature is preferably below 60°C. If two different temperatures of process air are applied to the fiber during the drawing process, the above description refers to the process temperature of the air that first contacts the filament.

[0104] The maximum air velocity in the drawing channel is usually higher than 50 m / s.

[0105] Further details and advantages of the invention will become apparent from the following drawings and embodiments. The drawings show:

[0106] Figure 1 A schematic cross-section of a general-purpose, side-by-side bicomponent fiber with no curvature;

[0107] Figure 2 : A schematic diagram of crimped fibers;

[0108] Figure 3 : A schematic diagram of a spinning machine suitable for producing spunbond nonwoven fabric sheets according to the present invention;

[0109] Figure 4 : A schematic diagram of a production line suitable for producing multilayer sheets according to the present invention;

[0110] Figure 5 SEM (scanning electron microscope) image of a cross section of side-by-side bicomponent fibers with a curved interface line.

[0111] Figure 1 A schematic cross-sectional view of a bicomponent fiber arranged side-by-side is shown. Fiber F comprises first and second propylene polymers A and B arranged side-by-side. This arrangement extends along the entire length of the fiber.

[0112] Figure 2 This is a schematic cross-sectional view of the crimped fiber F included in the nonwoven fabric sheet of the present invention. The fiber is curved and includes a certain crimp radius and a certain number of crimps.

[0113] Figure 3 A spinning machine 100 suitable for producing spunbond nonwoven fabrics according to the present invention is shown. The spunbond nonwoven fabric NW is produced from continuous fibers F of a thermoplastic material, which are spun in a spinneret 101 and subsequently passed through a cooling device 102. A monomer extraction device 104 is arranged between the spinneret 101 and the cooling device 102 for removing gases in the form of decomposition products, monomers, oligomers, etc., generated during the spinning of fiber F. The monomer extraction device 4 includes an inlet or an extraction gap.

[0114] In the cooling device 102, process air is applied to the fiber curtain from opposite sides of the spinneret 101. The cooling device 102 is divided into two sections 102a and 102b, which are arranged in series along the fiber flow direction. Therefore, process air at a relatively high temperature (e.g., 60°C) can be applied to the fiber in the cavity section 102a at an earlier stage, and process air at a relatively low temperature (e.g., 30°C) can be applied to the fiber in the cavity section 102b at a later stage. The process air is supplied through air supply cavities 105a and 105b, respectively. The chamber pressures in cavities 105a and 105b can be the same and can be, for example, higher than the ambient pressure, for example, by about 3000 Pascals.

[0115] Below the cooling device 102 is a drawing device 106 for drawing and stretching the fibers 103. The drawing device includes an intermediate channel 107, which preferably converges and narrows as the distance from the spinneret 101 increases. In one embodiment, the convergence angle of the intermediate channel 107 can be adjusted. After passing through the intermediate channel 107, the fiber curtain enters the lower channel 108.

[0116] The cooling device 102 and the drawing device 106 (including the intermediate channel 107 and the lower channel 108) together form a closed assembly, which means that no main airflow can enter from the outside along the entire length of the assembly, and no main process air supplied in the cooling device 102 can escape to the outside. Some flue gas extraction devices can be installed directly below the spinneret to extract a small volume of air.

[0117] The fiber 103 exiting the drawing device 106 then passes through the laying unit 109, which includes two successively arranged diffusers 110 and 111, wherein diffuser 110 has a diverging section and diffuser 111 has a converging section and an adjacent diverging section. The diffuser angles, particularly the diffuser angles in the diverging regions of diffusers 110 and 111, are adjustable. A gap 115 exists between diffusers 110 and 111 through which ambient air is drawn into the fiber flow space.

[0118] After passing through the laying unit 109, fiber F, as a nonwoven web NW, is deposited on the spun yarn 113 formed by the breathable web. A suction device 116 is arranged below the laying area of ​​the spun yarn 113 to draw away process air, such as... Figure 3 As shown by arrow 117 in the middle.

[0119] Once deposited, the nonwoven web NW is first guided through the gap between a pair of pre-consolidation rollers 114 to pre-consolidate the nonwoven web NW.

[0120] Figure 4 The diagram illustrates a production line 200 for producing SMS-type nonwoven laminated fabric sheets (NWLS) of the present invention.

[0121] Specifically, the machine is configured to produce SMS-type nonwoven laminated fabric sheets (NWLS), specifically in the form of SMMSH sheets, where "S" represents a conventional spunbond layer, i.e., a layer formed from uncrimped fibers, "M" represents a meltblown layer, and "SH" represents a high-loft spunbond layer formed from crimped bicomponent fibers. The "SH" layer within the fabric is the layer according to the invention. An SMS-type sheet where the spunbond structure on one side of the internal meltblown structure is a high-loft structure and the spunbond structure on the other side of the internal meltblown structure is a conventional spunbond sheet is called a semi-high-loft structure. The conventional S layer provides mechanical stability, the M layer improves liquid barrier properties, and the lofty S layer enhances the fabric's softness and flexibility.

[0122] Production line 200 includes a spinning machine 100 for producing the SH layer, configured as follows: Figure 3 As illustrated, two reservoirs 118a and 118b contain two different polymer components, A and B, for spinning bicomponent fibers. An additional reservoir 119 contains a masterbatch with additives such as nucleating agents or viscosity-reducing cracking additives.

[0123] Furthermore, production line 200 includes a spinning ribbon 213, a first spinning machine 220 (which includes only one polymer reservoir 218 and is configured to spin monocomponent fibers for forming a conventional S-layer), and two meltblown machines 230 (for forming a MM double-layer meltblown structure). Machines 220, 230, and 100 are arranged in series along the spinning ribbon 213.

[0124] Downstream of each spinning machine 220 and 100 are pre-consolidation roller pairs 214 and 114. Downstream of the last spinning machine is a calender / embossing roller 240 for firmly bonding the layers of the laminate NWLS together.

[0125] Figure 5 This image shows a cross-sectional SEM (scanning electron microscope) image of a bicomponent fiber with a curved interface line between the polymer components.

[0126] Figure 5 The images were taken using the method explained below, a method generally preferred for measuring the curvature that defines the invention. In principle, curvature is an absolute geometric property of a fiber, independent of how it is measured. The curvature of a single fiber will naturally vary over its length, and not every fiber in a fabric sheet is identical. For practical purposes, it is best to pick up at least ten fibers from the nonwoven sheet, measure the curvature of each picked fiber at randomly selected length positions, and use the average.

[0127] When measuring from a nonwoven sheet, the machine orientation is first determined, and then the sheet is encapsulated in polyester or epoxy resin and released. The resulting polymer block is then cut across a plane perpendicular to the plane of the encapsulated nonwoven sheet, on a plane perpendicular to the machine orientation. After etching, the cut surfaces are polished to have a visible interface. The exposed fiber cross-section at the polished cut surface is etched to remove the majority of the amorphous portion of the polymer component. Measurements are taken from fiber ends that have the most circular cross-section and are therefore oriented as strictly as possible along the machine orientation at the cut surface. Small orientation deviations can be corrected to eliminate distortion. From a practical standpoint, a useful fiber cross-section is an ellipse with a ratio between the major and minor axes of less than 1.2. Preferably, the fibers are circular. After taking SEM images in a manner generally known to practitioners, the curvature can be determined using an image-based measurement system (such as the Datlnf measurement system from Datlnf GmbH).

[0128] It can be seen that the interface between the two polymers is curved. Figure 5 In this example, the polymer on the left is a propylene-α-olefin copolymer with a relatively low crystallization temperature, while the polymer on the right is a propylene homopolymer with a relatively high crystallization temperature. The curved interface arches to the left, specifically towards the propylene-α-olefin copolymer with the relatively low crystallization temperature. The polymer component with the higher crystallization temperature has a denser cross-section.

[0129] The curvature “c” is measured and calculated according to the following description. First, the distance “b” between the polymer surface intersections is measured using a line drawn between the polymer intersections on the fiber surface. This line is the imaginary baseline. In the given example, it is 540 pixels. Next, the bow height “h” is measured by drawing a line orthogonally from the baseline (usually the middle of the baseline) to the crest of the curved interface line. The length of the line corresponds to the bow height “h”, which is 111 pixels in the given example.

[0130] Then the curvature is given as 111 / 540 = 0.206. Therefore, Figure 5 Fibers with curvature within the range required by the present invention are shown.

[0131] The invention will now be described with reference to the following non-limiting embodiments.

[0132] Experimental Section

[0133] A) Method

[0134] Unless otherwise defined, the following definitions and determination methods apply to the above general description of the invention and the following embodiments.

[0135] MFR2 (230°C) is measured according to ISO 1133 (230°C, 2.16 kg load). The MFR2 of the polypropylene composition is determined on the particles of the material, while the MFR2 of the meltblown mesh is determined on slices of compression-formed sheets prepared from the mesh in a heated press at a temperature not exceeding 200°C, the slices having dimensions comparable to the particle size.

[0136] Xylene-soluble fraction at room temperature (Xylene cold soluble fraction XCS, wt%): The amount of polymer soluble in xylene was determined at 25°C according to ISO 16152; 5th edition; 2005-07-01.

[0137] DSC analysis, melting temperature (T) m ), enthalpy of fusion (H) m ), crystallization temperature (T) c ) and crystallization enthalpy (H c ): Samples of 5 to 7 mg were measured using a TAInstrument Q200 differential scanning calorimetry (DSC). The DSC was operated according to ISO 11357-1, -2 and -3 / Method C2 in a heating / cooling / heating cycle at a scan rate of 10 °C / min over a temperature range of -30 to +225 °C. Crystallization temperature (T c ) and crystallization enthalpy (H c The melting temperature (T) is determined by the cooling step, while the melting temperature (T) is determined by the melting step. m ) and enthalpy of fusion (H m The result is determined by the second heating step or the first heating step (if it is a mesh).

[0138] The number-average molecular weight (Mn), weight-average molecular weight (Mw), z-average molecular weight (Mz) and MWD (Mw / Mn) of polypropylene were determined by gel permeation chromatography (GPC) according to ISO 16014-4:2003 and ASTM D 6474-99. A PolymerChar GPC instrument equipped with an infrared (IR) detector was used, with 3×Olexis and 1×Olexis Guard columns from Polymer Laboratories, using 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol) as the solvent, at a temperature of 160°C and a constant flow rate of 1 mL / min. 200 μL of sample solution was injected for each analysis. The column set was calibrated using universal calibration (according to ISO 16014-2:2003) with at least 15 narrow MWD polystyrene (PS) standards in the range of 0.5 kg / mol to 11500 kg / mol. The Mark-Houwink constants for PS, PE and PP used are as described according to ASTM D6474-99. All samples were prepared by dissolving the polymer samples in stabilized TCB (same as the mobile phase) for 2.5 hours at a maximum temperature of 160°C under continuous gentle shaking in the autosampler of the GPC instrument, to achieve a PP concentration of ~1 mg / mL (at 160°C). The MWD of the polypropylene composition was determined on material pellets, while the MWD of the meltblown web was determined on fiber samples from the web, both dissolved in a similar manner.

[0139] Basis weight and thickness of the web

[0140] The basis weight (grammage) of the web is determined according to ISO 536:1995, in g / m 2 . The thickness of the web is measured on a web having a basis weight of 20 g / m 2 .

[0141] Curvature (c) of crimped fibers

[0142] The curvature (c) of fibers is determined by the method specified in combination with Figure 5 above.

[0143] Filament fineness

[0144] Filament fineness (in denier) is calculated from the average fiber diameter using the following relationship:

[0145] Fiber diameter (cm) = (4.444×10 -6 × denier / 0.91 × π)1 / 2

[0146] B) Examples

[0147] The preparation of the propylene polymers (PP1 to PP4) used in the embodiments (IE1 to 6) and comparative examples (CE1 to 2) of the present invention is described in detail below.

[0148] Basic polymers: The production of basic polymers is as follows:

[0149] PP1: The production of the base polymer PP1 is described in WO2017118612 as a polypropylene homopolymer used in embodiments of the present invention.

[0150] PP2: The base polymer of PP2 is prepared by compounding 95% by weight of the PP1 base polymer with 5% by weight of PP-MB (described as IE2 in EP3184587B1).

[0151] The preparation of the catalyst used in the polymerization process of PP3, the basic polymer, is as follows:

[0152] Chemicals used:

[0153] A 20% toluene solution of butyl ethyl magnesium (Mg(Bu)(Et), BEM) supplied by Chemitura

[0154] 2-Ethylhexanol, provided by Amphochem

[0155] 3-Butoxy-2-propanol-(DOWANOL) TM PnB), provided by Dow

[0156] Bis(2-ethylhexyl) citrate, provided by SynphaBase

[0157] TiCl4, provided by Millenium Chemicals

[0158] Toluene, supplied by Aspokem

[0159] 1-254, provided by Evonik

[0160] Heptane, supplied by Chevron

[0161] Preparation of magnesium alkoxy compounds

[0162] An alkoxymagnesium compound solution was prepared in a 20L stainless steel reactor by adding a mixture of 4.7 kg of 2-ethylhexanol and 1.2 kg of butoxypropanol to 11 kg of a 20 wt% toluene solution of butylethyl magnesium (Mg(Bu)(Et)). The temperature of the reactor contents was maintained below 45°C during the addition. After the addition was complete, the reaction mixture was continued to be mixed at 60°C (70 rpm) for 30 minutes. After cooling to room temperature, 2.3 kg of the donor bis(2-ethylhexyl) citrate was added to the alkoxymagnesium compound solution, maintaining the temperature below 25°C. Mixing was continued for 15 minutes with stirring (70 rpm).

[0163] Preparation of solid catalyst components

[0164] 20.3 kg TiCl4 and 1.1 kg toluene were added to a 20 L stainless steel reactor. The mixture was stirred at 350 rpm and kept at 0 °C. 14.5 kg of the alkoxymagnesium compound prepared in Example 1 was added over 1.5 hours. 1.7 L of [the compound] was then added. 1-254 and 7.5 kg of heptane were mixed at 0°C for 1 hour, and the temperature of the resulting emulsion rose to 90°C within 1 hour. After 30 minutes, mixing was stopped, the catalyst droplets solidified, and the resulting catalyst particles settled. After settling (1 hour), the supernatant was siphoned away. The catalyst particles were then washed with 45 kg of toluene at 90°C for 20 minutes, followed by two washes with heptane (30 kg, 15 minutes each). During the first heptane wash, the temperature was lowered to 50°C, and during the second wash, the temperature was lowered to room temperature.

[0165] The catalyst thus obtained is used in conjunction with triethylaluminum (TEAL) as a co-catalyst and dicyclopentyldimethoxysilane donor (D-donor) as an external donor.

[0166] Polymerization was carried out in a Borstar PP-type polypropylene (PP) pilot plant, which includes a loop reactor and a gas-phase reactor.

[0167] The polymerization conditions of the PP3 base polymer are shown in Table 1.

[0168] Table 1: Preparation of basic propylene polymer PP3

[0169]

[0170] The base polymer of PP3 was subjected to viscosity-reducing cracking at 200 to 230 °C using a suitable amount of (tert-butylperoxy)-2,5-dimethylhexane (Trigonox 101, distributed by Akzo Nobel, Netherlands) with 5 wt% PP-MB, 500 ppm Irganox 3114 (BASF), 500 ppm Irgafos 168 (BASF), and 500 ppm Ceasit FL (Baerlocher).

[0171] PP4: The production of the base polymer of PP4 is described in EP2999721B2 as Example IE3 of the present invention.

[0172] Table 2: Performance of polypropylene polymers after pellet thickening and cracking in the embodiments and comparative examples of the present invention

[0173] C2 content [weight%] 0.4 0.4 2.1 3,6 Final MFR [g / 10min] 27 27 27 33 Mw / Mn [-] 4.7 4.7 4.6 6.4 Mz / Mw [-] 2.07 2.08 2.06 2.7 XCS [weight%] 4.5 4.4 3.4 8.1 <![CDATA[T g ]]> [℃] -0.5 -0.5 -2.1 -4,7 <![CDATA[T m ]]> [℃] 158 163 154 149 <![CDATA[T c ]]> [℃] 111 124 119 120

[0174] Preparation of crimped multicomponent fibers with side-by-side cross-sectional configuration

[0175] like Figure 3 The illustration shows a range of options on a machine that process two polymers arranged side-by-side.

[0176] For all options, use a basis weight of 20 g / m³. 2 The spunbond nonwoven material sheet. The specific polymer production rate in spinneret 101 is approximately 0.52 g polymer per orifice per minute. The chamber pressure is kept essentially constant at 4000 Pascals. Other process settings are kept within the normal range for crimped fiber production. For example, the ceramic pre-consolidated roller 114 on the spinneret located on the beam exit side operates at a temperature of 50 to 70°C. Calender ( Figure 3 (Not shown in the diagram, but located downstream of pre-consolidation roll 114) is a standard open-point calender with a bonding area of ​​12% and per cm 2 25 circular bonding points. The calender temperature is in the range of 135 to 145°C.

[0177] Table 3 summarizes the data on the polymer compositions used in the fiber preparation processes of embodiments IE1, IE2, IE3, IE4, IE5 and IE6, and CE1 to CE2 of the present invention, the bow height of the fiber cross section, and the thickness of the fabrics made from the fibers.

[0178] Table 3:

[0179]

[0180] It can be seen that to obtain a thicker mesh, the polymers on both sides need to have the correct combination. Table 3 shows that the meshes of IE1 to IE6 have a much higher thickness than those of CE1 and CE2, while the basis weight of the mesh is the same (20 g / m²). 2 ).

Claims

1. Use of a polymer composition comprising a first propylene polymer A and a second propylene polymer B for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein (i) The first propylene polymer A and the second propylene polymer B are distributed side-by-side on the cross-section of the crimped multicomponent fiber, wherein the interface line between the first propylene polymer A and the second propylene polymer B, contained in the radial plane of the crimped multicomponent fiber, is curved with a curvature c. Where the baseline length b is the length of the imaginary straight baseline connecting the two endpoints of the curved interface line, and the bow height h is the distance between the crest of the curved interface line and the baseline. (ii) The mass ratio [A:B] of the first propylene polymer A to the second propylene polymer B is in the range of 10:90 to 90:10, and (iii) The absolute value of the difference between the crystallization temperature [Tc(A)] of the first propylene polymer A and the crystallization temperature [Tc(B)] of the second propylene polymer B, as determined by ISO 11357 at a scan rate of 10 °C / min, is in the range of 6 to 30 °C.

2. Use of the polymer composition according to claim 1 for producing crimped multicomponent fibers having a side-by-side cross-sectional arrangement, wherein the interface line between the first propylene polymer A and the second propylene polymer B in the radial plane of the crimped multicomponent fibers is curved, with a curvature c of which is Where the baseline length b is the length of the imaginary straight baseline connecting the two endpoints of the curved interface line, and the bow height h is the distance between the crest of the curved interface line and the baseline.

3. Use of the polymer composition according to claim 1 or 2 for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the first propylene polymer A is a propylene homopolymer or a propylene / α-olefin random copolymer, the first propylene polymer A having a melt flow rate (MFR) of 15 to 120 g / 10 min at a load of 2.16 kg and 230 °C as determined according to ISO 1133, and / or having a molecular weight distribution (Mw / Mn) in the range of 2.5 to 10.0 as determined by size exclusion chromatography according to ISO 16014.

4. Use of the polymer composition according to claim 1 or 2 for producing crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the first propylene polymer A has (i) Melting temperature T measured by DSC in accordance with ISO 11357-1&-2 in the range of 150°C to 164°C m , (ii) Crystallization temperature T measured by DSC in accordance with ISO 11357-1&-2 in the range of 90°C to 135°C c ,as well as (iii) Comonomer content <1.0% by weight.

5. Use of the polymer composition according to claim 1 or 2 for producing crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the first propylene polymer A has (i) Melting temperature T measured by DSC in accordance with ISO 11357-1&-2 in the range of 142°C to 155°C m , (ii) Crystallization temperature T measured by DSC in accordance with ISO 11357-1&-2 in the range of 80°C to 125°C c ,as well as (iii) Comonomer content in the range of 1.0 to 5.5% by weight.

6. Use of the polymer composition according to claim 1 or 2 for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the second propylene polymer B is a propylene homopolymer or a propylene / α-olefin random copolymer, the second propylene polymer B having a melt flow rate (MFR) of 15 to 120 g / 10 min at a load of 2.16 kg and 230 °C as determined according to ISO 1133, and / or having a molecular weight distribution (Mw / Mn) in the range of 2.5 to 10.0 as determined by size exclusion chromatography according to ISO 16014.

7. Use of the polymer composition according to claim 1 or 2 for producing crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the second propylene polymer B has (i) Melting temperature T measured by DSC in accordance with ISO 11357-1&-2 in the range of 150°C to 164°C m , (ii) Crystallization temperature T measured by DSC in accordance with ISO 11357-1&-2 in the range of 90°C to 135°C c ,as well as (iii) Comonomer content <1.0% by weight.

8. Use of the polymer composition according to claim 1 or 2 for producing crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the second propylene polymer B has (i) Melting temperature T measured by DSC in accordance with ISO 11357-1&-2 in the range of 142°C to 155°C m , (ii) Crystallization temperature T measured by DSC in accordance with ISO 11357-1&-2 in the range of 80°C to 125°C c ,as well as (iii) Comonomer content of 1.0 to 5.5% by weight.

9. Use of the polymer composition according to claim 1 or 2 for producing crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the first propylene polymer A and the second propylene polymer B are different, and at least one of the first propylene polymer A and the second propylene polymer B is viscous cracked.

10. Use of the polymer composition according to claim 1 or 2 for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein only one of the first propylene polymer A and the second propylene polymer B is viscous-reducing cracked, and the M between the first propylene polymer A and the second propylene polymer B is... z / M w The absolute value of the difference ranges from 0.3 to 10.

0.

11. Use of the polymer composition according to claim 1 or 2 for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein both the first propylene polymer A and the second propylene polymer B are viscous-reduced and cracked, and the M between the first propylene polymer A and the second propylene polymer B is... z / M w The absolute value of the difference is between 0.0 and 0.

3.

12. Use of the polymer composition according to claim 1 or 2 for the production of crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein at least one of the first propylene polymer A and the second propylene polymer B is nucleated, and the amount of nucleating agent is between 0.01 and 5000 ppm based on the total amount of nucleated propylene polymers.

13. Use of the polymer composition according to claim 1 or 2 for producing crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the first propylene polymer A is a propylene homopolymer and the second propylene polymer B is a propylene / α-olefin random copolymer.

14. Use of the polymer composition according to claim 12 for producing crimped multicomponent fibers having a side-by-side cross-sectional configuration, wherein the amount of the first propylene polymer A is less than the amount of the second propylene polymer B.

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