Polyurethane elastic fiber, and pleated member and sanitary material containing the same

Abstract

Provided is a thermoplastic polyurethane elastic fiber having excellent mobility in a paper diaper manufacturing process. The polyurethane elastic fiber of the present invention has the following characteristics: (a) is a multifilament; (b) has a total denier of 160 dtex or more and 2000 dtex or less; (c) has a flow-out start temperature of 160°C or more and 220°C or less under the conditions of an extrusion load of 49 N, a start temperature of 120°C, and a temperature increase of 3°C / minute in a flow tester; and (d) has a cohesive force between filaments of 0.4 cN or more.

Description

Technical Field

[0001] This invention relates to polyurethane elastic fibers, pleated components containing the same, and sanitary materials. Background Technology

[0002] Polyurethane elastic fibers used as pleats in the waist and leg areas of hygiene materials such as diapers are typically multifilaments with a fineness of 160 dtex or higher, and with minimal breakage due to the winding of monofilaments around guide devices and conveyor rollers during the diaper manufacturing process. For this application, polyurethane urea elastic fibers obtained by dry spinning using organic solvents in the spinning solution are commonly used. However, in recent years, from environmental, safety, and energy cost perspectives, there has been a search for thermoplastic polyurethane elastic fibers produced using melt spinning without the use of organic solvents.

[0003] Patent Document 1 discloses a thermoplastic polyurethane elastic filament with excellent processability, which is not prone to breakage or deterioration during thermal bonding, and is intended for use in knitted fabrics. Typically, the filament mobility required in the manufacturing process of disposable diapers differs from that in the manufacturing process of knitted fabrics, such as the requirement for continuous use of multiple products. However, Patent Document 1 only envisions applications in knitted fabrics and does not provide detailed disclosure regarding polyurethane elastic fibers with excellent filament mobility in the manufacturing process of disposable diapers.

[0004] In addition, Patent Document 2 below discloses coarse-fiber multifilament elastic fibers for diapers with a fineness of 200 to 2200 dtex, but its manufacturing method is dry spinning.

[0005] Patent Document 3 is known as a polyurethane elastic fiber for diapers obtained by melt spinning, but Patent Document 3 does not specifically disclose a means to improve mobility.

[0006] Thus, no thermoplastic polyurethane fibers with a fineness of 160 dtex or higher and excellent mobility in the diaper manufacturing process have been found.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2006-307409

[0010] Patent Document 2: Japanese Patent Application Publication No. 2004-52127

[0011] Patent Document 3: International Publication No. 2015 / 055459 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] In view of the aforementioned prior art, the problem to be solved by the present invention is to provide thermoplastic polyurethane elastic fibers with excellent mobility in the diaper manufacturing process, pleated components containing the same, and sanitary materials.

[0014] Solution for solving the problem

[0015] The inventors unexpectedly discovered that thermoplastic polyurethane elastic fibers with a coarseness of 160 dtex or higher, in which the bonding force between the monofilaments is within a certain range, exhibit excellent mobility in the diaper manufacturing process, thus completing the present invention.

[0016] That is, the present invention is as described below.

[0017] [1] A polyurethane elastic fiber, having the following characteristics:

[0018] (a) is a multifilament;

[0019] (b) Total fineness is 160 dtex or more and 2000 dtex or less;

[0020] (c) The outflow start temperature under the conditions of extrusion load 49N, start temperature 120℃, and temperature rise 3℃ / min in the flow tester is above 160℃ and below 220℃;

[0021] (d) The adhesion force between the monofilaments is greater than 0.4 cN.

[0022] [2] The polyurethane elastic fiber described in [1] above, wherein the birefringence Δn is 0.010 or higher.

[0023] [3] The polyurethane elastic fiber according to [1] or [2] above, wherein the birefringence Δn is less than 0.025.

[0024] [4] The polyurethane elastic fiber according to any one of [1] to [3] above contains more than 0% and less than 0.5% by weight of saturated fatty acid metal salt and / or saturated fatty acid amide.

[0025] [5] The polyurethane elastic fiber according to any one of [1] to [4] above, wherein the number of filaments (monofilaments) is 3 or more, and the average length of the bonded portion of the filaments in the cross section of the aforementioned polyurethane elastic fiber is 10 μm or more.

[0026] [6] The polyurethane elastic fiber according to any one of [1] to [5] above, wherein the stress is 0.015 cN / dtex or more when 90% recovery occurs in the second cycle of the 200% elongation / recovery repeat test.

[0027] [7] The polyurethane elastic fiber according to any one of [1] to [6] above, wherein the monofilament fineness is 5 dtex or more and 50 dtex or less.

[0028] [8] A pleated component comprising polyurethane elastic fibers as described in any one of [1] to [7].

[0029] [9] A sanitary material containing polyurethane elastic fibers as described in any one of [1] to [7].

[0030] The effects of the invention

[0031] The polyurethane elastic fibers of the present invention exhibit excellent mobility during the diaper manufacturing process. Furthermore, the pleats and sanitary materials, as other embodiments of the present invention, possess appropriate fastening force, making it less prone to diaper slippage and leakage. Attached Figure Description

[0032] Figure 1 A diagram showing the length of the bonded portion between monofilaments.

[0033] Figure 2 This is a schematic diagram illustrating a method for evaluating mobility. Detailed Implementation

[0034] The embodiments of the present invention will be described below. It should be noted that the present invention is not limited to the following embodiments, and various modifications can be made within its scope.

[0035] The polyurethane elastic fiber of this embodiment has the following characteristics:

[0036] (a) is a multifilament;

[0037] (b) Total fineness is 160 dtex or more and 2000 dtex or less;

[0038] (c) The outflow start temperature under the conditions of extrusion load 49N, start temperature 120℃, and temperature rise 3℃ / min in the flow tester is above 160℃ and below 220℃;

[0039] (d) The adhesion force between the monofilaments is greater than 0.4 cN.

[0040] The polyurethane elastic fiber in this embodiment is a multifilament (characteristic (a)). There is no particular limitation on the number of filaments (monofilaments), as long as there are two or more.

[0041] In this embodiment, the total fineness of the polyurethane elastic fibers is 160 dtex or more and 2000 dtex or less (characteristic (b)). The total fineness referred to herein is calculated from the mass of a certain amount of yarn after winding. The total fineness is preferably 200 dtex or more and 1000 dtex or less, more preferably 300 dtex or more and 700 dtex or less. If the total fineness is 160 dtex or more, the fastening force in the pleats is sufficient, and slippage of the diaper is less likely. On the other hand, if the total fineness is less than 2000 dtex, stiffness in the pleats is less likely, and the diaper adheres sufficiently to the hot melt adhesive.

[0042] Furthermore, in this embodiment, the polyurethane elastic fiber preferably has a monofilament fineness of 5 dtex or more and 50 dtex or less. If the monofilament fineness is 5 dtex or more, breakage during spinning is less likely to occur. On the other hand, if the monofilament fineness is 50 dtex or less, cooling is easier to achieve during spinning, and the orientation of the monofilament is easier to apply, thus making it easier to obtain sufficient recovery stress.

[0043] For the polyurethane elastic fiber of this embodiment, (c) the outflow start temperature under the conditions of an extrusion load of 49N, a starting temperature of 120°C, and a heating rate of 3°C / min in the flow tester is 160°C or higher and 220°C or lower, preferably 170°C or higher and 215°C or lower, more preferably 180°C or higher and 210°C or lower. If the outflow start temperature is 160°C or higher, the heat resistance is sufficiently high, and filament breakage due to heat during hot melt adhesive coating is less likely to occur in the diaper manufacturing process. On the other hand, if the outflow start temperature is 220°C or lower, melting at high temperatures is not required during melt spinning, thus the thermal decomposition of urethane is less likely to occur, and filament breakage is less likely to occur.

[0044] For the polyurethane elastic yarn of this embodiment, (d) the adhesion force between the monofilaments is 0.4 cN or more. The adhesion force between the monofilaments is defined as the force required to peel the monofilaments from the multifilaments, and the specific measurement method is explained by the examples described later. If the adhesion force is 0.4 cN or more, in the diaper manufacturing process, there will be less breakage, vibration, swaying, and tension variation of the moving yarns caused by the unwinding of the yarns and the winding of the monofilaments around the guide device, resulting in good mobility. The adhesion force between the monofilaments is preferably 0.6 cN or more. In order to keep the adhesion force within the aforementioned range, it is preferable to adjust the spinning conditions so that the yarn temperature at the bundle position of the multifilaments is 25°C or more. It should be noted that "adhesion between monofilaments" does not mean that the monofilaments are merely connected to each other, but rather that they are bonded by certain forces, and also includes the case of fusion. From the viewpoint of yarn mobility, it is preferable for the monofilaments to be fused together. In addition, the adhesion force between the monofilaments is preferably 3.0 cN or less, more preferably 2.5 cN or less, and even more preferably 2.0 cN or less. If the bond strength is below 3.0 cN, the stress will increase sufficiently at 90% recovery.

[0045] The polyurethane elastic fiber of this embodiment preferably has a birefringence Δn of 0.010 or more, more preferably 0.013 or more, and even more preferably 0.015 or more. Furthermore, a birefringence Δn of 0.025 or less, more preferably 0.022 or less, and even more preferably 0.020 or less is preferred. If the birefringence Δn is 0.010 or more, the polyurethane molecular chains are sufficiently oriented, and the stress during recovery is sufficiently increased. Conversely, if the birefringence Δn is 0.025 or less, the elongation is sufficiently increased. To ensure that the birefringence Δn is within the aforementioned range, it is preferable to adjust the spinning temperature, cooling air temperature, cooling air volume, spinning speed, false twist position, and other conditions (hereinafter referred to as "spinning conditions") so that the yarn temperature at the bundled position of the multifilament is between 20°C and 50°C. In this way, the yarn spun before bundling is oriented in a sufficiently cooled state, and therefore the birefringence Δn is within the aforementioned range.

[0046] The polyurethane elastic fiber of this embodiment preferably contains more than 0.5% by weight and less than 0.5% by weight of saturated fatty acid metal salt and / or saturated fatty acid amide. Normally, it is difficult to prevent sticking when monofilament bonding is present; however, by containing saturated fatty acid metal salt and saturated fatty acid amide within the aforementioned range, both monofilament bonding and anti-sticking can be achieved, resulting in a filament with good unwinding and mobility. By preventing sticking, a filament with good unwinding properties is formed when the filament is unwound at high speed from the roll during the diaper manufacturing process, suppressing the occurrence of breakage caused by unwinding of the filament while it is wound around the roll and tension variations during filament movement. The polyurethane elastic fiber of this embodiment more preferably contains 0.2% to 0.4% by weight of saturated fatty acid metal salt and / or saturated fatty acid amide.

[0047] It should be noted that saturated fatty acid metal salts refer to compounds formed by the bonding of saturated fatty acids and metal ions. Saturated fatty acid amides refer to amide compounds formed by the condensation of saturated fatty acids and amines. The saturated fatty acids constituting the saturated fatty acid metal salts and saturated fatty acid amides are preferably saturated fatty acids with 12 to 20 carbon atoms, examples of which include lauric acid, palmitic acid, stearic acid, arachidic acid, etc., with stearic acid being particularly preferred. Furthermore, the metals constituting the saturated fatty acid metal salts include magnesium, calcium, aluminum, zinc, etc., with magnesium being preferred. Furthermore, the amines constituting the saturated fatty acid amides can be monoamines or diamines. Examples of monoamines include monomethylamine, dimethylamine, monoethylamine, diethylamine, monoethanolamine, diethanolamine, etc., and examples of diamines include ethylenediamine, hexamethylenediamine, etc., with ethylenediamine being preferred. That is, magnesium stearate is preferred as the saturated fatty acid metal salt, and ethylenediamine distearate is preferred as the saturated fatty acid amide.

[0048] In this embodiment, the polyurethane elastic fiber preferably has a stress of 0.015 cN / dtex or more at 90% recovery in the second cycle of a 200% elongation / recovery repeat test. If the stress is 0.015 cN / dtex or more at 90% recovery in the second cycle of a 200% elongation / recovery repeat test, the fastening force is sufficient when used as a pleat in a diaper, making it less likely for the diaper to slip off or leak.

[0049] The polyurethane elastic fiber in this embodiment preferably has a breaking elongation of 300% or more, more preferably 400% or more, and even more preferably 450% or more. If the elongation is 300% or more, it is less likely to break during the diaper manufacturing process. The elongation can be achieved by carefully adjusting the spinning conditions, controlling the polymer viscosity and spinning tension during spinning, and adjusting the fiber orientation.

[0050] In this embodiment, the polyurethane elastic filament preferably has two or more filaments, and the average length of the bonded portion between the monofilaments in the cross-section of the polyurethane elastic fiber is 10 μm or more, more preferably 11 μm or more, and even more preferably 12 μm or more. The method for measuring the average length of the bonded portion between the monofilaments in the cross-section is described in detail in the examples described later. If the average length of the bonded portion between the monofilaments is 10 μm or more, the bonding force between the monofilaments is sufficiently high, and the filament mobility in the diaper manufacturing process is good. In order to keep the average length of the bonded portion between the monofilaments within the aforementioned range, it is preferable to control the spinning conditions and keep the filament temperature at the bundle position of the multifilaments at 25°C or more.

[0051] The polyurethane elastic filament of this embodiment preferably contains a polyurethane resin that is a polymer of a polyol, an organic diisocyanate compound, and a compound containing active hydrogen.

[0052] The polyol is preferably polyalkylene ether glycol, polyester glycol, or polycarbonate glycol, which are commonly used in the polymerization of thermoplastic polyurethanes. Polyalkylene ether glycol is particularly preferred, and polyols with a number average molecular weight of 900 to 3000 are especially preferred. Examples of polyalkylene ether glycols include those with a tetramethylene alkylene group, and those with a tetramethylene group and a straight-chain or branched alkylene group having 1 to 8 carbon atoms. Specifically, polytetramethylene ether glycol, copolymerized poly(tetramethylene-neoptioleyl) ether glycol, and copolymerized poly(tetramethylene-2-methylbutylene) ether glycol are preferred.

[0053] As organic diisocyanates, this includes all organic diisocyanates that are applicable to aliphatic, alicyclic, and aromatic diisocyanates and that exhibit solubility or liquid state under reaction conditions. Specifically, examples include methylene-bis(4-phenylisocyanate), methylene-bis(3-methyl-4-phenylisocyanate), 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, m- and p-phenylenediamine diisocyanate, α,α,α',α'-tetramethyl-phenylenediamine diisocyanate, m- and p-phenylenediamine diisocyanate, 4,4'-dimethyl-1,3-phenylenediamine diisocyanate, 1-alkylphenylenediamine-2,4- and 2,6-diisocyanate, 3-(α-isocyanate ethyl)phenylisocyanate, 2,6 Diethylphenylene-1,4-diisocyanate, diphenyl-dimethylmethane-4,4-diisocyanate, diphenyl ether-4,4'-diisocyanate, naphthylene-1,5-diisocyanate, 1,6-hexamethylene diisocyanate, methylene-bis(4-cyclohexyl)isocyanate, 1,3- and 1,4-cyclohexylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, etc., with methylene-bis(4-phenyl)isocyanate being particularly preferred.

[0054] As the active hydrogen-containing compound that reacts with the isocyanate group, low molecular weight diols can be used, specifically including ethylene glycol, 1,2-propanediol, 1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,4-butanediol, 1,3-butanediol, hexamethylenediol, diethylene glycol, 1,10-decanediol, 1,3-dimethylolcyclohexane, or 1,4-dimethylolcyclohexane. Alkanolamines such as 2-amino-1-ethanol, 3-amino-1-propanol, 4-amino-1-butanol, and 5-amino-1-pentanol can also be used. 1,4-Butanediol is particularly preferred as the active hydrogen-containing compound that reacts with the isocyanate group.

[0055] The polyurethane elastic filament of this embodiment may contain stabilizers as needed. Examples of stabilizers include compounds commonly used in polyurethane resins, such as ultraviolet absorbers, antioxidants, light stabilizers, gas stabilizers, and antistatic agents. Additionally, anti-adhesion agents and treatment agents may be added during spinning as needed. Anti-adhesion agents are preferably the aforementioned saturated fatty acid metal salts or saturated fatty acid amides. Treatment agents can be well-known agents such as dimethylsilicone and mineral oil, and are preferably one or more of the following: dimethylsilicone, mineral oil, higher alcohols having OH groups at the ends of carbons 8 to 25, polyalkylene ether glycols, polyalkylene ether glycols, and organic diisocyanates.

[0056] The polyurethane resin contained in the polyurethane elastic fiber of this embodiment can be manufactured using known polyurethane reaction techniques, and can be manufactured using either a one-step process or a prepolymer process. In the case of the prepolymer process, under nitrogen purging, a polyol and an organic diisocyanate are added to a reaction tank equipped with a warm water jacket and a stirrer at a molar ratio of 1:1.8 to 3.0, preferably 1:2.2 to 2.5, and a prepolymer reaction is carried out at 40 to 100°C, more preferably 50 to 80°C, to obtain a prepolymer with two-terminated isocyanate groups. Next, an active hydrogen compound is added to this prepolymer in an equivalent amount approximately equal to the number of functional groups of the isocyanate terminal groups to carry out a chain extension reaction. As an equivalent ratio, it is preferably 0.95 to 1.1, more preferably 0.99 to 1.05, relative to the isocyanate terminal groups. Then, solid-state polymerization is carried out to obtain a polyurethane with a specified molecular weight. As a method for chain extension reaction and solid-state polymerization, an active hydrogen compound can be directly added to a batch reaction vessel containing a prepolymer at 40–100°C, then removed and subjected to solid-state polymerization at 60–200°C, preferably 80–130°C, to obtain a fragmented polymer. Alternatively, after uniformly mixing the prepolymer and solid-state polymer, a cylindrical tube extruder can be used, with the barrel temperature of the polymerization zone set to 180–240°C. After obtaining the polymer continuously or semi-continuously, solid-state polymerization can be carried out at 60–200°C, preferably 80–140°C.

[0057] The molecular weight (Mw) of the obtained polyurethane resin, when determined by GPC according to the polystyrene standard, is typically about 100,000 to 800,000, preferably 150,000 to 500,000, and more preferably 200,000 to 400,000.

[0058] There are no particular restrictions on the spinning method as long as the desired physical properties are obtained. For example, in addition to feeding polyurethane resin fragments into an extruder and heating and melting them for spinning, another method can be listed: melting polyurethane resin fragments and mixing them with polyisocyanate compounds for spinning. For prepolymers with two-terminated isocyanate groups, a method can be used to continuously spin prepolymers with two-terminated isocyanate groups and active hydrogen compounds without fragmentation.

[0059] The polyurethane resin fed into the extruder is metered by a metering pump and introduced into the spinning head. As needed, foreign matter is removed by filtering through metal mesh, glass beads, etc., inside the spinning head, and then it is ejected from the spinneret, cooled by air in a cold air chamber, given a treatment agent, and wound up by the guide roller.

[0060] In the spinning process, the temperature profile and spinning tension of the fiber are meticulously controlled by adjusting the temperature of the die head, the speed and temperature of the cold air, the bundling position, and the spinning speed. The die head temperature is preferably 180℃~220℃, more preferably 200℃~210℃. A common melt spinning cooling method is used, such as contacting the spinneret perpendicularly to the direction of filament movement with cold air from directly below the spinneret. The cold air speed is preferably 0.2m / s~2.0m / s, more preferably 0.5m / s~1.2m / s, and the cold air temperature is preferably 5℃~20℃, more preferably 7℃~15℃. The bundling position is used as a method to bond the multifilaments. A false twisting machine is installed between the spinneret and the guide roller. Twist is transmitted from below according to the strength of the twist, causing the filaments to bundle together, and the height of this bundling point is controlled. The false twisting method can be a conventional method, such as air false twisting using an air nozzle or a ring false twisting machine that contacts a rotating ring. The bundling position can be defined as the distance from the spinneret to the point where the filaments are bundled, preferably 800-1700 mm, more preferably 1000-1600 mm, and even more preferably 1200-1400 mm. This allows control over the orientation achieved by the cooling of the filaments and the temperature of the filaments at the bundling position, resulting in fibers with excellent stress and adhesion during elongation recovery.

[0061] Pleated members containing the polyurethane elastic fibers of this embodiment and sanitary materials are also aspects of the present invention. Specific examples of sanitary materials include absorbent articles such as disposable diapers and feminine hygiene products, masks, and bandages. In diapers, pleated members made by bonding elastic fibers to nonwoven fabric using a hot-melt adhesive are used in the waist and leg openings; the pleated members of this embodiment are suitable for such areas. The polyurethane elastic fibers of this embodiment can be used to manufacture pleated members and sanitary materials that offer good mobility and excellent fastening strength during the diaper manufacturing process.

[0062] Example

[0063] The present invention will be specifically described below through examples and comparative examples, but the present invention is not limited to these examples. The measured values ​​in the examples, etc., were obtained by the measurement methods described below. It should be noted that the roll body manufactured in this example was sampled, but if the following sampling cannot be performed due to limitations such as sample size, an appropriate and reasonable sampling method and measurement method can be used.

[0064] (1) Outflow start temperature

[0065] Using a Shimadzu CFT-500D flow tester (manufactured by Shimadzu Corporation), an extrusion load of 49 N was applied with a sample weight of 1.5 g, a die (nozzle) diameter of 0.5 mm, and a thickness of 1.0 mm. After preheating at an initial set temperature of 120°C for 240 seconds, the temperature was increased at a constant rate of 3°C / min, and the plunger stroke-temperature curve was plotted. As the sample was heated at a constant rate, it was slowly heated, and polymer began to flow out. The flow temperature at this point is set as the outflow start temperature. If the temperature is further increased, a large amount of molten polymer flows out, and the plunger descent stops, ending the test. The average temperature after three measurements is set as the outflow start temperature. It should be noted that the test sample used was 1.5 g of yarn unwound from the same roll, without pretreatment such as degreasing agents, the yarn was crumpled into a ball, and cut into four equal parts using scissors.

[0066] (2) The adhesive force between the monofilaments

[0067] The experiment was conducted using a Shimadzu EZ-SX AUTOGRAPH instrument at 20°C and 65% RH. For the determination of the adhesion strength between monofilaments, tweezers were used to separate the monofilaments of the multifilament, pulling out approximately 3 cm of each monofilament. One of the pulled monofilaments was then held in place by a lower chuck, while the remaining pulled multifilament was held in place by an upper chuck, with a holding length of 5 cm. The monofilament was then stretched vertically at a speed of 500 mm / min to separate it from the multifilament. To eliminate any slack, the stress was measured from the starting point of separation until the measurement was completed, up to 150 mm. The average value of the stress peak at 150 mm was taken as the adhesion strength. Five samples were collected at 5 m intervals, and the adhesion strength was measured at each sample, with the average value calculated.

[0068] (3) Elongation at break

[0069] The test was conducted using a Shimadzu AGS-500NG Autograph Tester at 20°C and 65% humidity. The elongation at break was measured when a 5cm elastic filament was stretched at a speed of 500mm / min. Five samples were collected at 5m intervals, and the elongation at break was measured for each sample. The average value was then calculated.

[0070] (4) Determination of stress at 90% recovery in the second cycle of the 200% elongation / recovery repeat test.

[0071] The tests were conducted using a Shimadzu AGS-500NG Autograph testing machine at 20°C and 65% humidity. For a 5cm specimen, the elongation / recovery was repeated twice at a speed of 500mm / min until 200% elongation was achieved. The stress at 90% recovery in the second elongation cycle was set as the 90% recovery stress of the second cycle. A higher value indicates a stronger fiber clamping force. Five samples were collected at 5m intervals, and the 90% recovery stress was measured at each sample. The average value was calculated.

[0072] (5) Birefringence Δn

[0073] An OLYMPUS BX-51P polarizing microscope with an OLYMPUS U-CTB compensator was used to measure Δn. Five samples were collected at 5m intervals, and the average value was calculated.

[0074] (6) Average length of the bonding portion of the monofilaments in the cross section

[0075] The cross-section, cut perpendicular to the length of the polyurethane elastic fiber, was photographed using SEM. From this cross-sectional image, the areas where the monofilaments are bonded together on the outer periphery of the multifilament were analyzed. Figure 1 The length of the line segment formed by connecting the two furthest bonding points, as shown, was measured. For the monofilament located on the outer periphery, the length of all bonding points was measured, and the average was calculated by dividing by the number of measurements. It should be noted that the multifilament used for taking SEM images of the cross-section was immersed in liquid nitrogen for more than 10 seconds before cutting, and then cut with a razor blade perpendicular to the length direction of the monofilament. It was then mounted on the SEM stage for observation so that its cross-section could be observed from the front. The SEM measurement magnification was set at an appropriate magnification so that the overall image of the cross-section of the multifilament could be observed. In this embodiment and the comparative example, measurements were taken in the range of 100 to 300x. For the number of measurements, five samples were taken from the same roll at intervals of more than 1m. The average length of the bonding portion obtained from each cross-section was divided by 5 and the result was taken as the average length of the bonding portion of that sample.

[0076] (7) Fineness

[0077] The polyurethane elastic fibers were peeled from the roll without tension. A length of 1 m was measured and cut off under tension-free and unslackened conditions. The weight was then calculated using the following formula:

[0078] Fineness (dt) = 10000 × weight per meter (g)

[0079] The measurement was performed 5 times, and the average value was taken as the fineness. The total fineness was the value obtained by measuring one multifilament using the above method, and the single filament fineness was the value obtained by dividing the total fineness by the number of filaments.

[0080] (8) Temperature of the filament at the bundle position

[0081] Using an InfRecR550Pro infrared thermal imaging camera manufactured by Nippon Avionics Co., Ltd., during spinning at an ambient temperature of 25°C, the camera was fixed at a height of 100 mm away from the filament at the height of the bundled position, with the focus on the bundled filament, to capture thermal images. The emissivity of the measured material was set to 0.9, and a black rubber plate was placed 30 mm behind the moving filament to minimize the influence of heat reflection from the external environment. The temperature of the uppermost part of the bundled position was extracted from the captured thermal image and set as the filament temperature at the bundled position.

[0082] (9) Mobility

[0083] The roll 1 of elastic fibers obtained by spinning is mounted on Figure 2 The device was moved under the following conditions: the elastic fiber feed roller 2 was set to a speed of 50 m / min, the pre-stretch roller 3 (winding the elastic fiber three times) was set to a speed of 80 m / min, and the take-up roller 4 was set to a speed of 85 m / min. The behavior of the elastic fiber in observation part 5 was visually observed for 3 minutes and evaluated according to the following evaluation criteria:

[0084] 5 points: The width of the silk sway is 0mm or more and less than 2mm.

[0085] 4 points: The width of the silk wavy line is more than 2mm and less than 4mm

[0086] 3 points: The width of the silk wavy line is 4mm or more but less than 6mm

[0087] 2 points: The width of the silk oscillation is 6mm or more.

[0088] 1 point: Decapitation.

[0089] If the mobility score is 3 or higher, fewer yarn breaks will occur during the diaper manufacturing process, resulting in pleats with good elasticity. If the mobility score is below 2, yarn breaks are more likely to occur during the diaper manufacturing process, leading to reduced diaper production efficiency.

[0090] (10) Relief

[0091] After spinning, 15g of elastic fiber from a 150g package wound on a paper tube is unwound and 15g is separated. The package with the 15g separated fiber is placed on a bobbin holder, and the filament is creeled vertically. Using a dogtail guide device, the filament is moved horizontally and wound through a take-up roller 2m away at a speed of 15m / min. An online tension meter (EIKO SOKKI.inc Z-2 type tension sensor, 50g range) is placed 1m in front of the take-up roller, and measurements are taken for 3 minutes. The average value is taken as the unwinding tension. The smaller this value, the better the filament separation from the package, indicating good unwinding performance. Unwinding performance is evaluated according to the following criteria:

[0092] 5 points: Relaxation tension less than 3g

[0093] 4 points: Relaxation tension is 3g or more but less than 5g

[0094] 3 points: Relaxation tension is 5g or more and less than 7g

[0095] 2 points: Relaxation tension is 7g or more but less than 10g

[0096] 1 point: The tension is 10g or more.

[0097] If the unwinding performance is 3 points or higher, it becomes a good filament for separation when the filament is unwound at high speed from the roll in the diaper manufacturing process, which can easily suppress the breakage caused by the unwinding of the filament while it is wrapped around the roll and the tension changes when the filament moves.

[0098] [Example 1]

[0099] 2400 g of polytetramethylene ether glycol with a number average molecular weight of 1800 and 750.75 g of 4,4'-diphenylmethane diisocyanate were reacted for 3 hours under a dry nitrogen atmosphere at 60°C with stirring to obtain a polyurethane prepolymer capped with terminal isocyanate. 9 g of ADEKA CORPORATION AO-60 as an antioxidant and 9 g of ADEKA CORPORATION LA-36 as an ultraviolet absorber were then mixed into the reaction solution, followed by the addition of 150.95 g of 1,4-butanediol. The mixture was stirred for 15 minutes to obtain a polyurethane with a viscosity of 200 Pa·s (30°C).

[0100] Then, the polyurethane was removed from the Teflon (registered trademark) tray and, with the polyurethane still in the tray, heat-treated in a hot air oven at 110°C for 19 hours to obtain the polyurethane resin. This polyurethane resin has a Shore A hardness of 75 and exhibits thermoplastic properties.

[0101] The polyurethane resin obtained in this way was pulverized to a powder of approximately 3 mm using a Horai Co., Ltd. UG-280 pulverizer. 0.35 parts by weight of dried ethylene bis-stearamide were added to the polyurethane resin powder, fed into the hopper, and melted inside the extruder. Metered and pressurized by a gear pump located at the head, and filtered, the extruded material was ejected from a 0.23 mm diameter, 60-hole nozzle at a temperature of 210°C at a rate of 31 g / min. Cold air at a velocity of 0.6 m / s and a temperature of 16°C was blown from a 900 mm long cold air chamber, making perpendicular contact with the fibers. Using a ring-type false-twisting machine positioned 5m below, the twist was conducted, with the bundling position (distance from the spinneret to the twisting point) set at 1400mm. Then, while applying a treatment agent primarily composed of polydimethylsiloxane and mineral oil, the fibers were wound at a speed of 500m / min to obtain polyurethane elastic fibers with a single filament fineness of 10 dtex and a total fineness of 620 dtex. The filament temperature at the bundling position was 30°C, and the treatment agent was applied to the polyurethane elastic fibers at a rate of 2 parts by weight. Various functional evaluations are shown in Table 3 below. Fibers exhibiting excellent stress at 90% recovery in the second cycle of the 200% repeated elongation / recovery test (an indicator of fastening strength), a mobility rating of 4 points, and good mobility were obtained. The various performance evaluation results of the elastic fibers are shown in Table 1 below.

[0102] [Example 2]

[0103] The speed of the contact ring false twisting machine was adjusted, and the bundling position was set to 1000 mm. Otherwise, the polyurethane fiber of Example 2 was obtained in the same manner as in Example 1. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0104] [Example 3]

[0105] By adjusting the rotation speed of the ring-type false twisting machine and setting the bundle position to 800mm, the polyurethane fiber of Example 3 was obtained in the same manner as in Example 1. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0106] [Example 4]

[0107] A 0.35 mm diameter, 36-hole nozzle was installed on the spinning spinneret. The die temperature was set to 215°C, and the spinneret was ejected at a rate of 43.4 g / min. The cooling air was set to a temperature of 15°C and a velocity of 0.7 m / s, and the spinneret was wound at a speed of 700 filaments / min. Otherwise, the polyurethane fiber of Example 4 was obtained in the same manner as in Example 1. The obtained monofilament fineness was 17 dtex, and the total fineness was 620 dtex. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0108] [Example 5]

[0109] The speed of the contact ring false twisting machine was adjusted, and the bundling position was set to 1000 mm. Otherwise, the polyurethane fiber of Example 5 was obtained in the same manner as in Example 4. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0110] [Example 6]

[0111] A 0.5 mm diameter, 24-hole nozzle was installed on the spinning spinneret. The die temperature was set to 220°C, and the spinneret was sprayed at a rate of 62 g / min. The cooling air was set to a temperature of 14°C and a velocity of 0.8 m / s, and the spinneret was wound at a speed of 1000 s per minute. Otherwise, the polyurethane fiber of Example 6 was obtained in the same manner as in Example 4. The obtained fiber had a single filament fineness of 26 dtex and a total fineness of 620 dtex. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0112] [Example 7]

[0113] A 0.5 mm diameter, 16-hole nozzle was installed on the spinning spinneret. The die temperature was set to 210°C, and the spinneret was ejected at a rate of 83 g / min. The cooling air was set to a temperature of 14°C and a velocity of 0.8 m / s, and the spinneret was wound at a speed of 1400 rpm. Otherwise, the polyurethane fiber of Example 7 was obtained in the same manner as in Example 4. The obtained fiber had a single filament fineness of 40 dtex and a total fineness of 620 dtex. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0114] [Example 8]

[0115] For the polyurethane resin powder, without adding dried ethylene bis-stearamide, the cold air temperature was set to 16°C and the cold air velocity to 0.7 m / s, otherwise the polyurethane fiber of Example 8 was obtained in the same manner as in Example 1. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0116] [Example 9]

[0117] For the polyurethane resin powder, 0.35 parts by weight of dried magnesium stearate were added instead of ethylene bis-stearamide, and the polyurethane fiber of Example 9 was obtained in the same manner as in Example 1. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0118] [Example 10]

[0119] The spray temperature was set to 200°C, the cold air temperature to 15°C, and the cold air velocity to 0.8 m / s. Otherwise, the polyurethane fiber of Example 10 was obtained in the same manner as in Example 4. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0120] [Example 11]

[0121] Adding 0.6 parts by weight of dried ethylene bis-stearamide to polyurethane resin powder and setting the bundle position to 1200 mm, the polyurethane fiber of Example 11 was obtained in the same manner as in Example 1. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0122] [Example 12]

[0123] The ejection temperature was set to 230°C, the cold air temperature to 15°C, and the cold air velocity to 0.7 m / s. The bundle position was set to 700 mm. Otherwise, the polyurethane fiber of Example 12 was obtained in the same manner as in Example 4. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0124] [Comparative Example 1]

[0125] The cold air temperature was set to 16°C, the cold air velocity to 0.6 m / s, and the bundle position to 1800 mm. Otherwise, the polyurethane elastic fiber of Comparative Example 1 was obtained in the same manner as in Example 4. Because the bundle position of the elastic fiber in Comparative Example 1 was not ideal, the monofilament bonding strength was 0.3 cN, and the mobility evaluation score was 2 points, indicating insufficient mobility. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0126] [Comparative Example 2]

[0127] The bundle position was set at 4500 mm, and the polyurethane elastic fiber of Comparative Example 2 was obtained in the same manner as Comparative Example 1. Because the bundle position of the elastic fiber in Comparative Example 2 was not suitable, the monofilament bonding strength was 0.2 cN, and the mobility evaluation score was 1, indicating insufficient mobility. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0128] [Comparative Example 3]

[0129] The temperature of the die head was set to 190°C, the cold air temperature to 15°C, and the cold air velocity to 0.9 m / s. Otherwise, the polyurethane elastic fiber of Comparative Example 3 was obtained in the same manner as in Example 1. Due to the low ejection temperature and high cold air velocity, the elastic fiber of Comparative Example 3 had excessively low filament temperature at the bundling position during spinning, preventing the individual filaments from bonding together, resulting in low adhesion and a score of 1 in the mobility evaluation. Furthermore, it was excessively cooled and over-oriented during spinning, leading to a reduced elongation of 280%. Many filaments could not withstand the stretch ratio required for the mobility evaluation, resulting in frequent breakage. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0130] [Comparative Example 4]

[0131] For polyurethane resin powder, without adding dried ethylene bis-stearamide, it was melted in an extruder. A 0.35 mm diameter, 36-hole nozzle was installed on the spinning spinneret. The die temperature was set to 208°C, and the powder was extruded from the nozzle at a rate of 37.2 g / min. The cold air temperature was set to 16°C and the air velocity to 0.5 m / s. The bundling position was set to 2200 mm, and the powder was wound at a speed of 600 filaments / min. Otherwise, the polyurethane fiber of Comparative Example 4 was obtained in the same manner as in Example 1. The obtained filament had low monofilament bonding strength and a mobility evaluation score of 2, indicating insufficient mobility. The various performance evaluation results of the elastic fiber are shown in Table 1 below.

[0132] [Table 1]

[0133]

[0134] Industrial availability

[0135] The polyurethane elastic fiber of the present invention has excellent bonding strength of the filaments, good mobility in the diaper manufacturing process, and excellent fastening force, and therefore can be suitable as an elastic component for the pleats and stretching parts of sanitary materials such as diapers.

[0136] Explanation of reference numerals in the attached figures

[0137] 1. Rolls of elastic fibers

[0138] 2 Feeding Rollers

[0139] 3 Pre-stretching rolls

[0140] 4 take-up rollers

[0141] 5. Observation area

[0142] 6 Ceramic Hook Guide Device

[0143] 7-bearing free roller

Claims

1. A polyurethane elastic fiber, having the following characteristics: (a) is a multifilament; (b) Total fineness is 160 dtex or more and 2000 dtex or less; (c) The outflow start temperature under the conditions of extrusion load of 49N, start temperature of 120℃ and temperature rise of 3℃ / min in the flow tester is above 160℃ and below 220℃; (d) The adhesion force between the monofilaments is greater than 0.4 cN and less than 3.0 cN; The birefringence Δn of the polyurethane elastic fiber is greater than 0.010 and less than 0.

025. The multifilament includes 3 or more filaments, and the average length of the bonded portion of the monofilaments in the cross section of the polyurethane elastic fiber is 10 μm or more.

2. The polyurethane elastic fiber according to claim 1, wherein, (b) Total fineness is 200 dtex or more and 1000 dtex or less.

3. The polyurethane elastic fiber according to claim 1 or 2, wherein, (b) Total fineness is above 300 dtex and below 700 dtex.

4. The polyurethane elastic fiber according to claim 1 or 2, wherein, (c) The outflow start temperature under the conditions of extrusion load of 49N, start temperature of 120℃, and temperature rise of 3℃ / min in the flow tester is above 170℃ and below 215℃.

5. The polyurethane elastic fiber according to claim 1 or 2, wherein, (c) The outflow start temperature under the conditions of extrusion load of 49N, start temperature of 120℃, and temperature rise of 3℃ / min in the flow tester is above 180℃ and below 210℃.

6. The polyurethane elastic fiber according to claim 1 or 2, wherein, (d) The adhesion force between the monofilaments is greater than 0.4 cN and less than 2.5 cN.

7. The polyurethane elastic fiber according to claim 1 or 2, wherein, (d) The adhesion force between the monofilaments is greater than 0.6 cN and less than 2.0 cN.

8. The polyurethane elastic fiber according to claim 1 or 2, wherein, The birefringence Δn is greater than 0.013 and less than 0.

025.

9. The polyurethane elastic fiber according to claim 1 or 2, wherein, The birefringence Δn is greater than 0.015 and less than 0.

025.

10. The polyurethane elastic fiber according to claim 1 or 2, wherein, The birefringence Δn is greater than 0.010 and less than 0.

022.

11. The polyurethane elastic fiber according to claim 1 or 2, wherein, The birefringence Δn is greater than 0.010 and less than 0.

020.

12. The polyurethane elastic fiber according to claim 1 or 2, wherein it contains more than 0% by weight and less than 0.5% by weight of saturated fatty acid metal salts and / or saturated fatty acid amides.

13. The polyurethane elastic fiber according to claim 1 or 2, wherein it contains 0.2% to 0.4% by weight of saturated fatty acid metal salt and / or saturated fatty acid amide.

14. The polyurethane elastic fiber according to claim 1, wherein, The average length of the bonded portion of the monofilaments in the cross section of the polyurethane elastic fiber is 11 μm or more.

15. The polyurethane elastic fiber according to claim 1, wherein, The average length of the bonded portion of the monofilaments in the cross-section of the polyurethane elastic fiber is 12 μm or more.

16. The polyurethane elastic fiber according to claim 1 or 2, wherein, The stress at 90% recovery in the second cycle of the 200% elongation / recovery repeat test is above 0.015 cN / dtex.

17. The polyurethane elastic fiber according to claim 1 or 2, wherein, The single filament fineness is above 5 dtex and below 50 dtex.

18. The polyurethane elastic fiber according to claim 1 or 2, wherein, The elongation at break is over 300%.

19. The polyurethane elastic fiber according to claim 1 or 2, wherein, The elongation at break is over 400%.

20. The polyurethane elastic fiber according to claim 1 or 2, wherein, The elongation at break is over 450%.

21. A pleated member comprising polyurethane elastic fibers as described in any one of claims 1 to 20.

22. A sanitary material comprising polyurethane elastic fibers as described in any one of claims 1 to 20.

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