Nonwoven material comprising crimped multi-component fibers

Abstract

The present invention relates to a nonwoven fabric sheet containing crimped multi-component fibers.

Description

[0001] This invention relates to nonwoven fabric sheets containing crimped multicomponent fibers.

[0002] Flat sheets of nonwoven materials are used in the hygiene industry for the mass production of baby diapers and similar products. To improve the comfort and functionality of these products, the industry is striving to increase the softness and flexibility of the materials. One way to meet these needs is to incorporate crimped multicomponent fibers into these materials, either as a substitute for linear monocomponent fibers or in addition to linear monocomponent fibers; this method has been widely described in the literature and implemented in the market. The use of crimped fibers makes nonwoven fabrics fluffier and less dense, and also makes the fabrics more flexible and soft. This is very similar to the difference between straight and curly hair.

[0003] Typically, crimped multicomponent fibers contain 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 during fiber stretching and quenching (as is the case with spunbond fibers).

[0004] One of the earliest patents for this technology is US 6,454,989 B1, originally filed by the American company Kimberly-Clark. In the context of spunbond technology, this document (which has become an industry standard for nonwoven materials used in hygiene applications) explained the basic principles and included a list of options under which the polymer distributed across the fiber cross-section could be different. The options mentioned included differences in melting point, crystallinity, melt elasticity, average or distributed molecular weight, and a general range of the degree of difference. However, few options were actually tested, and much research has been conducted since then to reveal the conditions under which it is practically feasible and to reveal material configurations that provide particularly desired properties in various aspects. Patents resulting from these developments include EP 3,165,656 B1, EP 3,121,314 B1, EP 3,246,443 B1, and EP 3,246,444 B1, all of which trace back to research conducted by the co-applicant of this application.

[0005] However, despite these various improvements, there is still a need to optimize and diversify the polymers that can be used to manufacture this material.

[0006] In this context, the present invention proposes a nonwoven fabric sheet comprising crimped multicomponent fibers, wherein the fibers comprise two distinct polymer components (A) and (B) arranged side-by-side on the cross-section of the fiber, wherein the interface line between the two polymer components (A) and (B) contained in the radial plane of the fiber is curved, and its curvature (c) (as defined by the quotient (h) / (b)) is 0.05 to 0.25, where (b) "baseline length" is the length of an imaginary straight baseline connecting the two endpoints of the curved interface line, and (h) "bow height" is the distance from the vertex of the curved interface line to the baseline. The interface line has the shape of a single arc, i.e., it is not wavy, or, in more mathematical terms, has no inflection point of curvature change. Referring again to the shape of the interface line, the interface line is contained in any radial plane of the fiber and is therefore visible when the fiber is cut in the radial direction.

[0007] 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 defining the invention is the shape of the interface line contained within this plane. This differs from the interface profile along a longitudinal or diagonal line, which in crimped fibers is naturally curved to some extent due to geometric relationships. The curvature of the radial interface line defining the invention is geometrically independent of the fiber's crimp.

[0008] Further research aimed at a more fundamental understanding of crimped bicomponent fibers revealed that beneficial crimping properties can be observed if the radial interface lines between the components of a multicomponent fiber with its polymer components arranged side by side have the curvature specified.

[0009] 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 properties have been observed in many cases.

[0010] For the purposes of this application, the side-by-side arrangement of polymer components (A) and (B) is given in standard side-by-side fibers, but can also exist in eccentric sheath-core fibers with a D-shaped core, which essentially corresponds to side-by-side fibers encapsulated by either polymer coating. However, these effects are observed, particularly in side-by-side bicomponent fibers containing only the two polymer components arranged side-by-side on the cross-section, when the curvature is within the defined range.

[0011] Although these effects have also been observed for other fiber types such as short fibers, in the preferred embodiment, the nonwoven material of the present invention is a spunbond material, and the crimped multicomponent fiber is a spunbond fiber.

[0012] In addition to other fibers such as linear monocomponent fibers, the sheet may also contain bicomponent fibers as defined in this invention, or the sheet may be composed of bicomponent fibers as defined in this invention. Since the millions of fibers that form nonwoven materials in reality are not always identical, the term "composed of..." must be understood in the sense that it is satisfied when the fibers are identical in production and the vast majority of the fibers (e.g., more than 80% of the fibers, preferably more than 90% of the fibers) exhibit the features of this invention.

[0013] To facilitate the spinning of spunbonded multicomponent fibers according to the present invention, the spunbonding machine must allow two directly adjacent streams of different polymers to flow side-by-side on the scale of a single fiber. These streams merge, and the merged streams then exit the spinneret (die plate) shortly thereafter. The formation and curvature of the curved interface depend on the polymers used and the process conditions during fiber stretching and quenching.

[0014] In this context, it is preferred that at least one of polymer components (A) or (B) is a polyolefin polymer. More preferably, both polymer components (A) and polymer components (B) are polyolefin polymers. Among polyolefin polymers, propylene homopolymers, ethylene homopolymers, and copolymers of propylene or ethylene with other α-olefins, especially propylene-α-olefin copolymers (like propylene-ethylene copolymers or propylene-C4-C8 copolymers), are preferred. In one embodiment, propylene-ethylene copolymers are most preferred. In the given context, a homopolymer is defined as a polymer having a comonomer content of less than 1% by weight, preferably less than 0.5% by weight. Copolymers of propylene or ethylene with other α-olefins preferably have a comonomer content between 1.0% by weight and 5.5% by weight. The copolymer is preferably a random copolymer.

[0015] In a particularly preferred embodiment, one of the polymer components (A) is a propylene homopolymer, and the other polymer component (B) is a propylene-α-olefin copolymer, wherein the propylene-α-olefin copolymer preferably has a comonomer content between 1.0 weight percent and 5.5 weight percent.

[0016] Furthermore, in this context, the crystallization temperature T of the two polymer components c The difference has been identified as a crucial parameter. In a preferred embodiment, the crystallization temperature [T] of polymer component (A) is... c (A) and the crystallization temperature of polymer component (B) [T] c The absolute value of the difference (B) is greater than 0°C and less than 30°C, preferably greater than 10°C and less than 25°C, as measured by differential scanning calorimetry (DSC, ISO 11357-1 and ISO 11357-2).

[0017] When polymer component (A) is a propylene homopolymer and polymer component (B) is a propylene-α-olefin copolymer, it is preferable that the crystallization temperature [Tc(A)] of the propylene homopolymer (A) is higher than the crystallization temperature [Tc(B)] of the propylene-α-olefin copolymer (B) to the extent described above.

[0018] In one embodiment, the curved radial interface line is arched toward the polymer component with a lower crystallization temperature, preferably a propylene-α-olefin copolymer. The polymer component with a higher crystallization temperature, preferably homopolymer polypropylene, has a more compact cross-section.

[0019] The crystallization temperature [T] of polymer component (A) with a higher crystallization temperature c The absolute value of (A) is preferably in the range of 90°C to 135°C, and more preferably 100°C to 125°C. The crystallization temperature [T] of the polymer component (B) having a lower crystallization temperature... c The absolute value of (B) is preferably between 80°C and 125°C, and more preferably between 90°C and 115°C.

[0020] Crystallization temperature T of polymers (A) and (B) c It is related to the chemical properties of the polymer and varies with, for example, the content of comonomers, stereoregularity, or molecular weight distribution in propylene-α-olefin copolymers.

[0021] Crystallization properties and kinetics can be further influenced and balanced by adding nucleating agents to one or both of polymer components (A) and (B).

[0022] Nucleating agents increase the number of sites where crystallites begin to form, and thus promote crystallization. Suitable nucleating agents include nonitol- or sorbitol-based nucleating agents.

[0023] In a preferred embodiment, the nucleating agent is an α-nucleating agent. Suitable α-nucleating agents include salts of monocarboxylic and polycarboxylic acids (e.g., sodium benzoate or aluminum tert-butylbenzoate), dibenzylidene sorbitol (e.g., 1,3:2,4-dibenzylidene sorbitol), C1-C8 alkyl-substituted dibenzylidene sorbitol derivatives (e.g., methyl dibenzylidene sorbitol, ethyl dibenzylidene sorbitol, or dimethyl dibenzylidene sorbitol, such as 1,3:2,4-di(methylbenzylidene)sorbitol), or substituted nonitol derivatives (e.g., 1,2,3,-trideoxy-4,6:5,7-bis-O-[(4-propylphenyl)methylene]-nonitol), phosphate diester salts (e.g., sodium 2,2'-methylenebis(4,6-di-tert-butylphenyl)phosphate or bis[2,2'-methylene-bis(4,6-di-tert-butylphenyl)phosphate]hydroxyaluminum), vinylcycloalkane polymers, and vinylalkane polymers. 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 (e.g., 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, or vinyl alkane polymers may be most preferred.

[0024] Based on the total weight of each polymer component, the appropriate addition amount is between 0.01-5000 ppm, preferably between 0.05-4500 ppm, more preferably between 0.1-4000 ppm, such as 0.15-3000 ppm.

[0025] Melting point T of the two polymer components m The difference has been identified as a potentially important parameter.

[0026] Melting temperature T of polymer component (A) with a high crystallization (and melting) temperature m Preferably, the temperature is within the range of 155°C to 164°C (when determined by DSC, ISO 11357-1 and ISO 11357-2). The melting temperature T of the polymer component (B) having a lower crystallization (and melting) temperature. m The absolute value is preferably in the range between 142°C and 155°C (when measured by DSC, ISO 11357-1 and ISO 11357-2).

[0027] Other relevant characteristics of the polymer include melt flow rate (MFR) and molecular weight distribution.

[0028] The melt flow rate of at least one, more preferably both, of the two polymer components (A) and (B) is in the range of 15 g / 10 min to 120 g / 10 min (when measured according to ISO 1133 at 230 °C and 2.16 kg). Preferably, the melt flow rate is less than 60 g / 10 min, at least for the component with the higher melt flow rate (in this embodiment, the propylene homopolymer).

[0029] The polydispersity (M) of at least one, more preferably both, of the two polymer components (A) and (B) w / M n The polydispersity index (PDI) is in the range of 4.5 to 10.0 (when measured by size exclusion chromatography according to ISO 16014), preferably in the range of 5.0 to 9.0, and more preferably in the range of 5.5 to 8.5. The absolute difference between the polydispersity of the two polymer components is preferably 0.3 or higher.

[0030] When polymer component (A) is a propylene homopolymer and polymer component (B) is a propylene-α-olefin copolymer, it is preferable that the polydispersity of the propylene homopolymer (A) is lower than that of the propylene-α-olefin copolymer (B).

[0031] Furthermore, the difference in melt viscosity at a given temperature can be a relevant parameter in a given context. In the case where polymer component (A) is a propylene homopolymer and polymer component (B) is a propylene-α-olefin copolymer, it is preferable that the melt viscosity of the propylene homopolymer (A) is lower than that of the propylene-α-olefin copolymer (B).

[0032] In another embodiment, at least one of the two polymer components (A) and (B), more preferably both, has a xylene cold soluble content (XCS) in the range of 1.5 wt% to 10.0 wt%, more preferably in the range of 1.5 wt% to 8.0 wt%. The amount of these xylene cold solubles (XCS) represents a low content in any elastomeric polymer component (like ethylene propylene rubber), and therefore represents a single-phase polymer component in which no elastomeric phase is dispersed. This system is characterized by a relatively high xylene cold soluble content.

[0033] In one embodiment, one or both of polymer components (A) and (B) are viscosity-reducing cracked. Viscosity-reducing cracking refers to controlled polymer chain cleavage by adding viscosity-reducing cracking additives to the polymer components. Polymer chain cleavage occurs at high temperatures as the polymer components melt and are extruded through the spinneret of a spunbond machine. Suitable viscosity-reducing cracking additives include organic peroxides, organic hydroxylamine esters, or thiols as sources of free radicals. Suitable addition amounts are between 100 ppm and 500 ppm. Viscosity-reducing cracking can be used to influence viscosity and adjust polydispersity as well as the further melting and crystallization properties of the two polymer components (A) and (B) relative to each other.

[0034] In one particular embodiment of the invention, only one of the propylene polymers (A and B) is viscous-reducing cracked, and the absolute value of the difference between Mz / Mw between propylene polymers A and B 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.

[0035] In another embodiment of the invention, two of the propylene polymers (A and B) are viscous cracked, and the absolute value of the difference between Mz / Mw between propylene polymers A and B 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.

[0036] The discovery of this invention is not limited to fibers in which two polymer components (A) and (B) arranged side by side are used within the fiber in a 50:50 weight ratio. Rather, the discovery applies to a wide range of weight ratios, such as 90:10 to 10:90. However, preferred weight ratios that result in significant crimp are between 80:20 and 20:80, more preferably between 70:30 and 30:70, and even more preferably between 60:40 and 40:60.

[0037] In one embodiment, the weight ratio of the polymer component (A) with a higher crystallization temperature (preferably a propylene homopolymer) to the polymer component (B) with a lower crystallization temperature (preferably a propylene-α-olefin copolymer) is less than 50:50, meaning that there is an excess of the polymer component (B) with the lower crystallization temperature in the fiber. It has been found that this can potentially enhance crimp.

[0038] In an alternative embodiment, the weight ratio of polymer component (A) with a higher crystallization temperature (preferably propylene homopolymer) to polymer component (B) with a lower crystallization temperature (preferably propylene-α-olefin copolymer) is greater than 50:50, meaning that there is an excess of polymer component (A) with a higher crystallization temperature in the fiber. This has been found to potentially enhance the stability of the production process.

[0039] The crimped bicomponent fibers are typically helically crimped. In one embodiment, the average number of crimps in the crimped bicomponent fibers is in the range of at least 7 crimps per cm of fiber, and preferably at least 10 crimps, as measured according to Japanese Standard JIS L-1015-1981 under a pre-tension load of 2 mg / denier. When measured according to JIS L-1015-1981 under a pre-tension load of 2 mg / denier, the crimp amplitude is preferably in the range of less than 0.30 mm, and preferably between 0.20 mm and 0.30 mm.

[0040] The fiber preferably has a linear mass density in the range of 1.0 to 2.2 denier, preferably 1.2 to 2.0 denier.

[0041] The base weight of each layer in the inner spunbond layer of a multilayer sheet can be 4-40 g / m². 2 Between, preferably between 5-25 g / m 2 between.

[0042] The density of the nonwoven fabric sheet is preferably less than 60 mg / cm³. 3 And preferably less than 50 mg / cm³ 3 These values ​​are typical for high-loft nonwovens with crimped fibers. In contrast, standard-loft nonwovens with non-crimped fibers typically have values ​​higher than 60-70 mg / cm³. 3 The density.

[0043] According to WSP.120.6, option A, at a pressure of 0.5 kPa at 2500 mm 2 When measuring on the plate, for 20g / m 2 For a base weight of 0 or greater, the thickness of the nonwoven fabric sheet is preferably greater than 0.35 mm.

[0044] In one embodiment, the spunbond sheet forms one layer of a multilayer sheet, which, in addition to the spunbond sheet according to the invention, includes one or more additional layers. The additional layers may be nonwoven materials (like additional spunbond sheets or meltblown sheets), or other sheets (like polymer films or woven fabrics). Preferred embodiments include S nType structures (like SS, SSS, etc.), wherein the sheet according to the invention is combined with at least one other spunbond nonwoven fabric sheet, preferably a spunbond nonwoven fabric sheet formed of non-crimped fibers (like monocomponent fibers); or any SM or SMS type structure (like SSM, SSMS, SMMS, SSMMS, etc.), wherein the sheet according to the invention is combined with one or more meltblown nonwoven fabric sheets, and optionally additionally combined with at least one other spunbond nonwoven fabric sheet, preferably a spunbond nonwoven fabric sheet formed of non-crimped fibers.

[0045] For multilayer sheets comprising the nonwoven sheet according to the invention, it is preferred that the nonwoven sheet according to the invention forms the outer layer of the multilayer sheet.

[0046] In one embodiment, the nonwoven sheet or multilayer sheet includes an adhesive pattern introduced during manufacturing via calendering rolls. In one embodiment, the adhesive pattern comprises 10-16% adhesive area and / or 20-45 dots / cm. 2 Point density and / or 0.35-0.55 mm per point 2 The point size. These relatively open bonding patterns are typical for sheets containing high-loft spunbond materials formed from crimped fibers.

[0047] The base weight of each layer in the spunbond inner layer of a multilayer sheet can be 3-25 g / m². 2 Between, preferably between 4-20 g / m 2 The base weight of the meltblown layer can be between 0.5-5 g / m². 2 Between, preferably between, 1-4 g / m 2 between.

[0048] The present invention further relates to a method for manufacturing spunbond nonwoven sheets or multilayers as defined above.

[0049] The spunbond nonwoven fabric sheet is manufactured in an apparatus comprising at least two extruders having a spinneret, a stretching channel, and a moving belt, wherein fibers are spun in the spinneret, stretched in the stretching channel, and laid on the moving belt, wherein the apparatus includes a pressurized process air chamber from which process air is guided through the stretching channel to stretch the fibers.

[0050] The stretching channel may include more than one segment. The stretching channel or a segment of the stretching channel may narrow with increasing distance from the spinneret. In one embodiment, the convergence angle may be adjusted. The apparatus may form a closed assembly extending from at least the process air inlet point to the end of the stretching channel, such that air cannot enter from the outside, and the supplied process air cannot escape to the outside. In one embodiment, the apparatus includes at least one diffuser disposed between the end of the stretching channel and the moving belt.

[0051] 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 overall 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 lower than 6000 Pascals, and more preferably lower than 5000 Pascals.

[0052] Suitable process air temperatures are typically greater than 10°C. However, it has been observed that, within a reasonable overall range, higher process air temperatures tend to result in curvature within the desired range and have a positive effect on crimping. In a preferred embodiment, the process air temperature is therefore above 20°C, more preferably above 25°C. The upper limit of the process air temperature is preferably below 60°C. If two different temperatures of process air are applied to the fiber during stretching, the above description refers to the process temperature of the air that first contacts the filament.

[0053] The maximum air velocity in the stretching channel is typically higher than 50 m / s.

[0054] Furthermore, this invention relates to hygiene products comprising nonwoven sheets or multilayer sheets according to the invention. The sheets of this invention can be used as nonwoven sheets in hygiene products such as adult urinary incontinence products, baby diapers, and sanitary napkins in the hygiene industry.

[0055] Further details and advantages of the invention will become apparent from the accompanying drawings and embodiments described below. The drawings show:

[0056] Figure 1 : A schematic cross-section of a general-purpose side-by-side bicomponent fiber with no curvature;

[0057] Figure 2 : A schematic diagram of crimped fibers;

[0058] Figure 3 : A schematic diagram of a spinning machine suitable for producing spunbond nonwoven fabric sheets according to the present invention;

[0059] Figure 4 : A schematic diagram of a production line suitable for producing multilayer sheets according to the present invention;

[0060] Figure 5 SEM (scanning electron microscope) image of a cross section of side-by-side bicomponent fibers with a curved interface line;

[0061] Figure 6 A schematic diagram of the cross-section of an eccentric sheath-core fiber with a D-shaped core and a curved interface line; and

[0062] Figure 7 For some embodiments, a graph showing the relationship between material thickness and interface curvature is plotted.

[0063] Figure 1 A schematic diagram of a cross-section of side-by-side bicomponent fibers is shown. Fiber F comprises a first polymer component A and a second polymer component B arranged side-by-side. This arrangement extends along the entire length of the fiber.

[0064] Figure 2 This is a schematic illustration of a segment of crimped fiber F included in the nonwoven fabric sheet of the present invention. The fiber is curved and includes a specific crimp radius and a specific crimp count.

[0065] Figure 3 A spinning machine 100 suitable for producing spunbond nonwovens according to the invention is shown. The spunbond nonwoven 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 to remove gases generated during the spinning of the fiber F in the form of decomposition products, monomers, oligomers, etc. The monomer extraction device 4 includes an extraction opening or extraction gap.

[0066] 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 arranged in series along the fiber flow direction. Thus, process air at a relatively high temperature (e.g., 60°C) can be applied to the fiber in an earlier stage in chamber section 102a, and process air at a relatively low temperature (e.g., 30°C) can be applied to the fiber in a later stage in chamber section 102b. The process air is supplied through air supply chambers 105a and 105b, respectively. For example, the chamber pressure in chambers 105a and 105b can be the same, and can be, for example, about 3000 Pascals higher than the ambient pressure.

[0067] A stretching device 106 for stretching and extending fibers 103 is arranged below the cooling device 102. The stretching device includes an intermediate channel 107, which preferably converges and narrows with increasing distance from the spinneret 101. In one embodiment, the convergence angle of the intermediate channel 107 can be adjusted. After the intermediate channel 107, the fiber curtain enters the lower channel 108.

[0068] The cooling device 102 and the stretching device 106 (including the intermediate channel 107 and the lower channel 108) together form a closed assembly, meaning that the main airflow will not enter from the outside along the entire length of the assembly, and the main process air supplied in the cooling device 102 will not escape to the outside. A small amount of smoke extraction device may be included directly below the spinneret.

[0069] The fiber 103, exiting the stretching device 106, then passes through a laying unit 109, which includes two consecutively arranged diffusers 110 and 111, wherein diffuser 110 has an expansion section and diffuser 111 has a convergence section and an adjacent expansion section. The diffusion angle, particularly the diffusion angle in the expansion sections of diffusers 110 and 111, is adjustable. A gap 115 is formed between diffusers 110 and 111 through which ambient air is drawn into the fiber flow space.

[0070] After passing through laying unit 109, fiber F, as a nonwoven web NW, is deposited on rotating belt 113 formed of a breathable mesh. Suction device 116 is arranged below the resting area of ​​rotating belt 113 to extract process air. Figure 3 The figure is illustrated by arrow 117.

[0071] Once deposited, the nonwoven web NW is first guided through the gap between a pair of pre-consolidation rollers 114 for pre-consolidating the nonwoven web NW.

[0072] Figure 4 The diagram illustrates a production line 200 for producing the SMS-type nonwoven laminated fabric sheet NWLS of the present invention.

[0073] Specifically, the machine is configured to produce SMMS in a specific form. H SMS-type nonwoven laminated fabric sheet (NWLS) in sheet form, where "S" represents the conventional spunbond layer, i.e., a layer formed from non-crimped fibers, "M" represents the meltblown layer, and "S" represents the nonwoven laminated fabric sheet. H "S" represents a high-loft spunbond layer formed from crimped bicomponent fibers. The layer "S" within this fabric... H"This is the layer according to the invention. The spunbond structure on one side of the internal meltblown structure is high-loft, and the spunbond structure on one side of the internal meltblown structure is a conventional spunbond sheet. The SMS-type sheet is called a semi-high-loft structure. The conventional S layer provides mechanical stability, the M layer improves liquid barrier properties, and the loft S layer enhances the softness and flexibility of the fabric."

[0074] Production line 200 includes facilities for producing S H - A spinning machine 100 with a single layer, such as Figure 3 The configuration is shown in the diagram. Two reservoirs 118a and 118b contain two different polymer components, A and B, for spinning bicomponent fibers. An auxiliary reservoir 119 may contain a masterbatch with additives such as nucleating agents or viscosity-reducing cracking additives.

[0075] Additionally, production line 200 includes a rotating belt 213, a first spinning machine 220 for forming a conventional S-layer (including only one polymer reservoir 218 and configured for spinning single-component fibers), and two meltblown machines 230 for forming an MM double-layer meltblown structure. Machines 220, 230, and 100 are arranged continuously along the rotating belt 213.

[0076] Downstream of each spinning machine 220 and 100 is a pair of pre-consolidation rollers 214 and 114. Calendering / printing rollers 240 for firmly bonding the layers of the laminated sheet NWLS are arranged downstream of the last spinning machine.

[0077] Figure 5 SEM images (scanning electron microscope images) of cross sections of bicomponent fibers with curved interface lines between polymer components are shown.

[0078] Figure 5 The images were taken using the method explained below, which is generally a good method for measuring the curvature that defines the invention. In principle, curvature is an absolute geometric property of a fiber and does not depend on how it is measured. The curvature of a single fiber naturally varies along its length, and each fiber in a fabric sheet is not exactly the same. For practical purposes, it is most preferable to select at least ten fibers from the nonwoven sheet, measure the curvature of each selected fiber at randomly chosen length positions, and use the average.

[0079] When measuring from nonwoven sheets, the machine orientation is first identified, and the sheet is wrapped and secured in polyester or epoxy resin. The resulting polymer block is then cut in a cross-machine directional plane perpendicular to the face of the wrapped nonwoven sheet. The cut surfaces are polished to have a visible interface after etching. The cross-sectional surfaces of the fibers exposed at the polished cut surfaces are etched to remove the more amorphous polymer components. Measurements are taken from the fiber ends that have the most circular cross-section and are therefore oriented as precisely as possible in the machine orientation at the cut surfaces. Corrections can be made for small directional deviations due to deformation. In practice, useful fiber cross-sections are elliptical with a ratio between the major and minor axes of less than 1.2. Fibers shown as circular are preferred. After taking SEM images in a manner generally known to practitioners, curvature can be determined using an image-based measurement system (such as the DatInf measure from DatInf GmbH).

[0080] It can be seen that the interface between the two polymers is curved. More specifically, the interface line has the shape of a single arc and has no inflection point indicating a change in curvature. Figure 5 In this example, the polymer on the left side is a propylene-α-olefin copolymer with a relatively low crystallization temperature, and the polymer on the right side is a propylene homopolymer with a relatively high crystallization temperature. The curved interface arches towards the left, i.e., towards the propylene-α-olefin copolymer with the relatively low crystallization temperature. The polymer component with the higher crystallization temperature has a more compact cross-section.

[0081] The curvature “c” is measured and calculated according to the description below. 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 an imaginary baseline. In the given example, the baseline is 540 pixels. Next, the bow height “h” is measured by drawing a line perpendicularly from the baseline (typically the middle of the baseline) to the vertex of the curved interface line. The length of the line corresponds to the bow height “h” and is 111 pixels in the given example.

[0082] Then the curvature is given by 111 / 540 = 0.206. Therefore, Figure 5 A fiber with curvature within the range required by the present invention is shown.

[0083] Figure 6 The illustration shows how the contents of the present invention can also be applied to eccentric sheath-core fibers with a D-shaped core. Example:

[0084] In such Figure 3 The machine shown in the middle has a range of options for processing two polymers arranged side by side.

[0085] For all options, 20g / m 2 The basic weight of the spunbond nonwoven sheet. The specific polymer yield in spinneret 101 is approximately 0.52 g polymer per minute per orifice. The chamber pressure remains essentially constant at 4000 Pascals. Other process settings remain within the normal range for producing crimped fibers. For example, the ceramic pre-consolidated roller 114 at the tow exit side of the rotating belt operates at a temperature of 50-70°C. Calender ( Figure 3 (Not shown in the image, but located downstream of the pre-consolidation roller 114) has a bonding area of ​​12% and 25 circular bonding points / cm². 2 A standard open-type point-type calender. The temperature of the calender is in the range of 135-145℃.

[0086] A series of different polymer combinations were tested. The main focus was on combinations with propylene homopolymer as polymer A and propylene-α-olefin copolymer as polymer B. The main parameter variation was the difference in crystallization temperature.

[0087] The configurations for each example are summarized in Table 1 below.

[0088] Table 1

[0089]

[0090] In the table, "CE" represents a comparative example and "IE" represents an inventive example.

[0091] Polymer component PP1 is the polypropylene homopolymer described in pages 17-20 of application WO 2017 / 118612A1, namely Borealis HG 475FB.

[0092] The polymer component PP2 is a combination of 95 wt% PP1 and 5 wt% polypropylene masterbatch containing a nucleating agent. The masterbatch is described as "IE2" in EP 3 184 587B1 and is a nucleated polypropylene homopolymer with an MFR of 230 / 2.16 of 8.0 g / 10 min.

[0093] The polymer component PP3 is a polypropylene homopolymer prepared as follows:

[0094] The catalyst used in the polymerization of polymer component PP3 was prepared as follows:

[0095] Chemicals used:

[0096] A 20% toluene solution of butyl ethyl magnesium (Mg(Bu)(Et), BEM) was supplied by Chemitura.

[0097] 2-Ethylhexanol, supplied by Amphochem.

[0098] 3-Butoxy-2-propanol-(DOWANOL) TM PnB), provided by Dow Chemical Company

[0099] Bis(2-ethylhexyl) citrate, supplied by SynphaBase.

[0100] TiCl4, supplied by Millenium Chemicals.

[0101] Toluene, supplied by Aspokem

[0102] 1-254, provided by Evonik

[0103] Heptane, supplied by Chevron.

[0104] Preparation of magnesium alkoxy compounds

[0105] Magnesium alkoxide solution was prepared 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 butyl ethyl magnesium (Mg(Bu)(Et)) while stirring (70 rpm). The reactor contents were kept below 45°C during the addition. After the addition was complete, the reaction mixture was continued to mix at 60°C (70 rpm) for 30 minutes. After cooling to room temperature, 2.3 kg g of the donor bis(2-ethylhexyl) citrate was added to the magnesium alkoxide solution, while the temperature was kept below 25°C. Mixing was continued for 15 minutes with stirring (70 rpm).

[0106] Preparation of solid catalyst components

[0107] 20.3 kg of TiCl4 and 1.1 kg of toluene were added to a 20 L stainless steel reactor. Mixing was carried out at 350 rpm while maintaining the temperature at 0 °C. 14.5 kg of the alkoxymagnesium compound prepared in Example 1 was added over 1.5 hours. 1.7 L of... 1-254 kg of heptane and 7.5 kg of toluene were mixed at 0 °C for 1 hour, and the temperature of the resulting emulsion was increased to 90 °C over 1 hour. Mixing was stopped after 30 minutes to solidify the catalyst droplets and allow the formed catalyst particles to settle. After settling (1 hour), the supernatant was siphoned off. The catalyst particles were then washed at 90 °C with 45 kg of toluene for 20 minutes, followed by two heptane washes (30 kg, 15 min 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.

[0108] The resulting catalyst was used in conjunction with triethylaluminum (TEAL) as a co-catalyst and dicyclopentyldimethoxysilane donor (D donor) as an external donor. Polymerization was carried out at the Borstar PP-type polypropylene (PP) pilot plant, which consisted of a circulating reactor and a gas-phase reactor. The polymerization conditions for the PP3 base polymer are described in Table 2.

[0109] Table 2

[0110]

[0111]

[0112] To obtain the polymer component PP3, the obtained polymer was then subjected to viscosity-reducing cracking with 5 wt% PP-MB, 500 ppm Irganox 3114 (BASF), 500 ppm Irgafos 168 (BASF), and 500 ppm Ceasit FI (Baerlocher) through a co-rotating twin-screw extruder at 200-230°C using an appropriate amount of (tert-butylperoxy)-2,5-dimethylhexane (Trigonox 101, distributed by AkzoNobel).

[0113] The polymer component PP4 is a polypropylene homopolymer, as described in EP 2 999 721 B2 as an example of the invention, “IE3”.

[0114] The polymer component PP5 is commercial grade resin Sabic 511A.

[0115] The polymer component PP6 is the commercial-grade resin Basell Moplen RP248R.

[0116] Table 3 below shows the physical properties of polymer components PP1-PP6.

[0117] Table 3

[0118] PP1 PP2 PP3 MFR* [g / 10min] 27 27 27 M w / M n **]]> [-] 4.7 4.7 4.6 M z / M w **]]> [-] 2.07 2.08 2.06 XCS*** [wt.-%] 4.5 4.4 3.4 <![CDATA[T m ****]]> [℃] 158 163 154 <![CDATA[T c ****]]> [℃] 111 124 119

[0119] Table 3 (continued)

[0120]

[0121]

[0122] *MFR is measured according to ISO 1133 (230°C, 2.16 kg load).

[0123] **Number-average molecular weight (M) n ), weight-average molecular weight (M) w ) and Z-average molecular weight (M z The results 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 and 1,2,4-trichlorobenzene (TCB, stabilized with 250 mg / L 2,6-di-tert-butyl-4-methylphenol) as solvent at 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 a universal calibration (according to ISO 16014-2:2003) and at least 15 narrow MWD polystyrene (PS) standards in the range of 0.5 kg / mol to 11,500 kg / mol. The Mark Houwink constants of the PS, PE, and PP used were as described in ASTM D 6474-99. All samples were prepared by dissolving the polymer sample in a stable TCB (same as the mobile phase) to a concentration of ~1 mg / ml (at 160°C) and continuously and gently agitating it in the autosampler of the GPC instrument for up to 2.5 hours at a maximum temperature of 160°C.

[0124] ***Xylene soluble fraction at room temperature (Xylene cold soluble fraction XCS, wt%): The amount of polymer soluble in xylene is determined at 25°C according to ISO 16152; 5th edition; 2005-07-01.

[0125] The melting temperature (Tm) and crystallization temperature (Tc) were measured using a TA Instrument Q200 differential scanning calorimeter (DSC) for samples ranging from 5 mg to 7 mg. The DSC was operated according to ISO 11357-1, ISO 11357-2, and ISO 11357-3 / Method C2 in a hot / cold / hot cycle, with a scan rate of 10 °C / min and a temperature range of -30 °C to +225 °C. The crystallization temperature (Tc) was determined by the cooling step, while the melting temperature (Tm) was determined by the second heating step.

[0126] The parameters measured in the examples in Table 1 are summarized in Table 4 below.

[0127] Table 4

[0128]

[0129]

[0130] *Fabric thickness as per WSP.120.6, Option A, at 2500 mm under 0.5 kPa pressure. 2 Measurement on board

[0131] **Curvature is determined by combining the above text.** Figure 5 Further explanation of the method to determine

[0132] Table 4 (continued)

[0133]

[0134] MD: Machine Direction

[0135] CD: Cross-machine direction

[0136] ***Tension and elongation properties are determined according to WSP 110.4. Figure 7 The illustration shows the relationship between bulk and fiber crimp (20 g / m²) for examples IE1-IE6 and some other examples. 2 A graph showing the relationship between the material thickness and the curvature "c" (as explained above). The standard 20 g / m² material contains no crimped fibers and is bonded using the same bonding calender. 2 Spunbond nonwovens will have a thickness of approximately 0.28 mm, so a baseline is drawn at 0.30 mm. It is evident that bulkiness, and therefore fiber crimp, is most pronounced when the curvature “c” value is between approximately 0.05 and approximately 0.25, peaking between approximately 0.12 and approximately 0.20. This applies independently regardless of whether the weight ratio between polymers A and B in the fiber is 50:50, 40:60, 60:40, or 70:30.

Claims

1. A spunbond nonwoven fabric sheet, said nonwoven fabric sheet comprising spunbond crimped multicomponent fibers, in, The spunbond nonwoven fabric sheet is manufactured in an apparatus comprising at least two extruders having a spinneret, a cooling device, a stretching channel, and a moving belt, wherein the fibers are spun in the spinneret, pass through the cooling device, are stretched in the stretching channel, and laid on the moving belt, wherein the apparatus includes a pressurized process air chamber from which process air is guided through the stretching channel to stretch the fibers, wherein the pressure in the process air chamber is higher than the ambient pressure, with a pressure difference of 2000-6000 Pascals, the maximum air velocity in the stretching channel is higher than 50 m / s, and the process air temperature is 20-60°C; The fiber comprises two different polymer components (A) and (B) arranged side by side on the cross section of the fiber, wherein the weight ratio of the two polymer components (A) to (B) is between 70:30 and 30:

70. The polymer components (A) and (B) are each independently selected from propylene homopolymer, ethylene homopolymer and propylene-α-olefin copolymer; One or both of the polymer components (A) and (B) contain a nucleating agent; The crystallization temperature [T] of the polymer component (A) as determined by DSC according to ISO 11357-1 and ISO 11357-2 c (A) and the crystallization temperature [T] of the polymer component (B). c The absolute value of the difference between (B) and [B] is greater than or equal to 8°C and less than 25°C; and The interface line between the two polymer components (A) and (B) contained in the radial plane of the fiber is curved and its curvature (c) is... Wherein 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 from the vertex of the curved interface line to the baseline, wherein the interface line has the shape of a single arc without an inflection point of curvature change sign; and the curved radial interface line is arched toward the polymer component with a lower crystallization temperature.

2. The spunbond nonwoven fabric sheet as described in claim 1, wherein the curvature (c) of the interface line is 。 3. The spunbond nonwoven fabric sheet as claimed in any of the preceding claims, wherein one of the polymer components (A) is a propylene homopolymer, and the other of the polymer components (B) is a propylene-α-olefin copolymer.

4. The spunbond nonwoven fabric sheet as described in claim 3, wherein, The propylene-α-olefin copolymer has a comonomer content between 1.0% and 5.5% by weight.

5. The spunbond nonwoven fabric sheet as described in claim 1 or 2, wherein, The crystallization temperature [T] of the polymer component (A) as determined by DSC according to ISO 11357-1 and ISO 11357-2 c (A) and the crystallization temperature [T] of the polymer component (B) c The absolute value of the difference between (B) and (B) is greater than 10°C and less than 25°C.

6. The spunbond nonwoven fabric sheet as described in claim 5, wherein, Polymer components with higher crystallization temperatures have a more compact cross-section.

7. The spunbond nonwoven fabric sheet as described in claim 1 or 2, wherein, When determined by DSC according to ISO 11357-1 and ISO 11357-2, the crystallization temperature [T] of the polymer component (A) with the higher crystallization temperature c The absolute value of (A) is in the range between 90°C and 135°C, and wherein, when determined by DSC according to ISO 11357-1 and ISO 11357-2, the crystallization temperature [T] of the polymer component (B) having the lower crystallization temperature is... c The absolute value of (B) is in the range between 80°C and 125°C.

8. The spunbond nonwoven fabric sheet as described in claim 1 or 2, wherein, The nucleating agent includes nonitol-based or sorbitol-based nucleating agents.

9. The spunbond nonwoven fabric sheet as described in claim 1 or 2, wherein, The nucleating agent is present in amounts between 0.15 ppm and 3000 ppm.

10. The spunbond nonwoven fabric sheet as described in claim 1 or 2, wherein, When determined by DSC according to ISO 11357-1 and ISO 11357-2, the melting temperature [T] of the polymer component (A) with the higher melting temperature is... m The absolute value of (A) is in the range between 155°C and 164°C, and wherein, when determined by DSC according to ISO 11357-1 and ISO 11357-2, the melting temperature [T] of the polymer component (B) having the lower melting temperature is... m The absolute value of (B) is in the range of 142°C to 155°C.

11. The spunbond nonwoven fabric sheet as described in claim 1 or 2, wherein, When measured according to ISO 1133 at 230°C and 2.16 kg, one or both of the polymer components (A) and (B) have a melt flow rate of 15 g / 10 min to 120 g / 10 min, and / or wherein, when measured according to ISO 16014 by size exclusion chromatography, one or both of the polymer components (A) and (B) have a polydispersity M of 2.5 to 10.

0. w / M n .

12. The spunbond nonwoven fabric sheet as described in claim 11, wherein, The absolute difference between the polydispersity of the two polymer components is 0.3 or higher.

13. The spunbond nonwoven fabric sheet as claimed in claim 1 or 2, wherein one or both of the polymer components (A) and (B) comprise a viscosity-reducing cracking additive.

14. The spunbond nonwoven fabric sheet as described in claim 13, wherein, The viscosity-reducing cracking additives include organic peroxides or organic hydroxylamine esters.

15. The spunbond nonwoven fabric sheet as described in claim 13, wherein, The viscosity-reducing cracking additive is present in amounts between 100 ppm and 500 ppm.

16. The spunbond nonwoven fabric sheet as claimed in claim 1 or 2, wherein the weight ratio between the two polymer components (A) and (B) is between 60:40 and 40:

60.

17. The spunbond nonwoven fabric sheet as described in claim 1 or 2, wherein, An excess of the polymer component (B) with a lower crystallization temperature is present in the multicomponent fiber.

18. A multilayer sheet comprising a spunbond nonwoven fabric sheet as described in any of the preceding claims, and additionally at least one spunbond nonwoven fabric sheet and / or at least one meltblown nonwoven fabric sheet.

19. A method for manufacturing a spunbond nonwoven sheet as claimed in any one of claims 1 to 17 or a multilayer sheet as claimed in claim 18, wherein the spunbond nonwoven sheet is manufactured in an apparatus comprising at least two extruders, the extruders having a spinneret, a cooling device, a stretching channel, and a moving belt, wherein the fibers are spun in the spinneret, pass through the cooling device, stretch in the stretching channel, and laid on the moving belt, wherein the apparatus includes a pressurized process air chamber from which process air is guided through the stretching channel to stretch the fibers, wherein the pressure in the process air chamber is higher than the ambient pressure, the pressure difference being 2000-6000 Pascals, the maximum air velocity in the stretching channel is higher than 50 m / s, and the process air temperature is 20-60°C.

20. A hygiene product comprising a spunbond nonwoven fabric sheet as claimed in any one of claims 1 to 17 or a multilayer sheet as claimed in claim 18.

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