Nonwoven fabrics for sanitary materials, substrates for SAP sheets, and SAP sheets

Abstract

This disclosure provides a nonwoven fabric for sanitary materials that exhibits excellent water retention, SAP loading capacity, and water permeability, making it suitable as a substrate for SAP sheets. The nonwoven fabric for sanitary materials of this disclosure has a warp / weft ratio (warp / weft) of 0.5 or higher for the variation value of the average coefficient of friction (MMD) obtained using the KES method, and a napping grade of 4 or lower obtained using the Martindale method.

Description

Technical Field

[0001] This disclosure relates to nonwoven fabrics for sanitary materials, substrates for SAP sheets, and SAP sheets. Background Technology

[0002] Diapers are basically composed of a top layer, absorbent core, bottom layer, and leg openings. The absorbent core is typically made by winding a mixture of SAP (superabsorbent polymer) and pulp using nonwoven fabric, tissue paper, etc. However, to achieve thinner diapers, there are cases where SAP-loaded nonwoven fabrics (SAP sheets) are used. The substrate for SAP sheets must be able to support a large amount of SAP, not impede SAP permeability, and retain its own moisture.

[0003] Patent Document 1 below discloses an SAP sheet formed by embedding and loading SAP on a planar fabric made of hydrophilic and crimped long fibers as a substrate.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2006-110329 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] However, there is a need for high-performance SAP substrates compared to the SAP substrates in reference 1, particularly SAP substrates with excellent liquid water retention.

[0009] In view of the problems of the prior art, the purpose of this disclosure is to provide a nonwoven fabric for sanitary materials that has excellent liquid retention, SAP loading capacity and water permeability and is suitable for SAP sheet substrates.

[0010] Solution for solving the problem

[0011] Examples of embodiments of this disclosure are listed in the following items [1] to

[14] .

[0012] [1] A nonwoven fabric for hygiene materials, wherein the ratio of the variation value of the average coefficient of friction (MMD) obtained by the KES method is greater than 0.5 and the napping grade obtained by the Martindale method is less than 4.

[0013] [2] The nonwoven fabric for sanitary materials described in Project [1] has a nap grade of 3 or lower obtained by the Martindale method.

[0014] [3] A nonwoven fabric for sanitary materials, wherein the aspect ratio (width / width) of the variation value of the average coefficient of friction (MMD) obtained by the KES method is 0.5 or more, and in a friction test conducted by the Martindale method, the same nonwoven fabric as the aforementioned nonwoven fabric for sanitary materials is used as the friction element, and when the friction test is conducted with a load of 9 kPa and 16 friction cycles, any one or more of the following occurs: surface roughness, pilling, pores and cracks.

[0015] [4] The nonwoven fabric for sanitary materials described in Project [3], when used as a friction element in a friction test using the Martindale method, is the same nonwoven fabric as the aforementioned nonwoven fabric for sanitary materials, and when the friction test is conducted with a load of 9 kPa and 16 friction cycles, it produces one or more of the following: pilling, holes and cracks.

[0016] [5] The nonwoven fabric for sanitary materials according to any one of items [1] to [4] has a unit area weight of 5 g / m². 2 Above and 80g / m 2 the following.

[0017] [6] The nonwoven fabric for sanitary materials according to any one of items [1] to [5] is composed of fibers with a fiber length of 50 mm or more.

[0018] [7] The nonwoven fabric for sanitary materials according to any one of items [1] to [6] is a spunbond nonwoven fabric.

[0019] [8] A nonwoven fabric for sanitary materials according to any one of items [1] to [7], which contains a water-permeable agent.

[0020] [9] The nonwoven fabric for sanitary materials according to any one of items [1] to [8] contains fibers with a crimp count of 3 or more / 2.5cm and 45 or less / 2.5cm.

[0021]

[10] The nonwoven fabric for sanitary materials according to any one of items [1] to [8] contains a polyolefin resin.

[0022]

[11] A substrate for SAP sheets, comprising any one of items [1] to

[10] for use as a nonwoven fabric for sanitary materials.

[0023]

[12] According to the SAP sheet substrate described in Project

[11] , the aforementioned nonwoven fabric for sanitary materials is a spunbond nonwoven fabric with a nap grade of 3 or lower obtained by the Martindale process and contains polyolefin resin.

[0024]

[13] An SAP sheet comprising a substrate for SAP sheets as described in item

[11] or

[12] and SAP.

[0025]

[14] A sanitary material containing the SAP sheet described in item

[13] .

[0026] The effects of the invention

[0027] The nonwoven fabric for sanitary materials disclosed herein can be appropriately used as a substrate for SAP sheets due to its excellent water retention, SAP loading capacity and water permeability. Detailed Implementation

[0028] Nonwoven fabrics for sanitary materials

[0029] The nonwoven fabric for sanitary materials disclosed herein (hereinafter also referred to as "nonwoven fabric") has an aspect ratio of 0.5 or higher for the variation value (MMD) of the average coefficient of friction determined by the KES (KAWABATAEVALUATION SYSTEM) method. The nonwoven fabric for sanitary materials disclosed herein is characterized in that the napping grade obtained by the Martindale method is 4 or lower, or, in a friction test conducted using the same nonwoven fabric as the aforementioned nonwoven fabric for sanitary materials as the friction element, when a friction test is performed with a load of 9 kPa and 16 cycles, any one or more of the following occurs: surface roughness, pilling, porosity, and cracking.

[0030] The nonwoven fabric can be either a long-fiber nonwoven fabric or a short-fiber nonwoven fabric. However, from the viewpoints of strength, productivity, and reduced skin irritation, long-fiber nonwoven fabrics are preferred, and spunbond nonwoven fabrics are particularly preferred. In this disclosure, long fibers refer to fibers with a fiber length of 50 mm or more. From the viewpoint of fiber shedding, the longer the fiber length, the better. The nonwoven fabric is preferably composed of fibers with an average fiber length of 50 mm or more, more preferably 80 mm or more, and even more preferably 100 mm or more. The longer the average fiber length, the less likely fiber shedding will occur, and the better the water retention of the liquid.

[0031] Nonwoven fabrics are preferably made of fibers formed from thermoplastic resins. There are no particular limitations on the thermoplastic resin, but examples include polyolefin resins such as polyethylene, polypropylene, and copolymer polypropylene; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolyester; polyamide resins such as nylon-6, nylon-66, and copolynylon; biodegradable resins such as polylactic acid, polybutylene succinate, and polyethylene succinate; and combinations thereof. One thermoplastic resin can be used alone or in combination of two or more. From the viewpoint of the nonwoven fabric's feel, its applications are mostly for disposable materials; from the viewpoint of versatility and ease of recycling, polyolefin resins are preferred.

[0032] The fiber form constituting the nonwoven fabric can be not only round fibers, but also fibers with special forms such as irregular cross-section fibers and hollow fibers. From the viewpoint of imparting characteristics to the surface structure of the nonwoven fabric, fiber crimp is preferred. The lower limit of the number of crimps is preferably 3 or more per 2.5 cm, more preferably 5 or more per 2.5 cm, and the upper limit, which can be combined with the above lower limit, is preferably 45 or less per 2.5 cm, more preferably 30 or less per 2.5 cm, and even more preferably 20 or less per 2.5 cm. If the number of crimps is 45 or less per 2.5 cm, the fibers will not shorten excessively, so as a substrate for SAP sheets, it is not easy to over-extract SAP, and the liquid water retention is improved. If the number of crimps is 3 or more per 2.5 cm, the SAP load capacity of the substrate for SAP sheets increases.

[0033] As a means of inducing fiber crimping, methods include forming irregular cross-sectional shapes of the fiber and performing uneven cooling during spinning. Even composite fibers composed of two or more thermoplastic resins can exhibit crimping, particularly by forming side-by-side (S / S) or eccentric sheath-core (eccentric S / C) shapes, which readily induce crimping. In the case of the eccentric sheath-core (eccentric S / C) shape, the core can be exposed on the fiber surface. In this case, the ratio of the core area to the fiber surface is preferably greater than 0% and less than 50%, more preferably greater than 0% and less than 30%. If the ratio of the core area to the fiber surface is less than 50%, the impact on adhesion when used as a bond in nonwoven fabrics is small, and the fabric strength is sufficient.

[0034] When the fiber is a composite fiber composed of two or more thermoplastic resins, any of the aforementioned thermoplastic resins can be combined to achieve the desired effect. From the viewpoint of bonding the fibers together, a combination of thermoplastic resins with different melting points is preferred. In this case, the weight percentage of the resin with the higher melting point in the fiber is preferably 20 wt% or more and 80 wt% or less, more preferably 30 wt% or more and 80 wt% or less, and even more preferably 50 wt% or more and 70 wt% or less.

[0035] From the viewpoint of the hand feel of the resulting nonwoven fabric, composite fibers are preferably combinations of polyolefin resins, or preferably combinations of polyolefin resins and polyester resins. Examples of composite fibers composed of polyolefin resins include those made of polyethylene, polypropylene, and copolymers of their monomers with other α-olefins. Among the other α-olefins, those with 3 to 10 carbon atoms are preferred, specifically propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 1-octene. When combining polyolefin resins and polyester resins, it is preferable to use polyethylene, polypropylene, and copolymers of their monomers with other α-olefins as the polyolefin resin, and polyethylene terephthalate as the polyester resin, or copolymers of polyethylene terephthalate containing isophthalic acid or the like as monomer units. Polyethylene terephthalate can be modified by mixing or by adding additives. From the viewpoints of high strength and resistance to breakage during use, excellent processability in the production of sanitary materials, and good hand feel, a combination of polypropylene and polyethylene is preferred as a combination of thermoplastic resins. When the composite fiber is an eccentric sheath type, it is preferable that the core is polypropylene and the sheath is polyethylene.

[0036] When polypropylene is used for the fiber, it can be any one of the following: polypropylene synthesized using a conventional Ziegler-Natta catalyst, polypropylene synthesized using a single-active-center catalyst, such as metallocene, or ethylene random copolymer polypropylene. These can be a single type or a combination of two or more types. From the viewpoints of feel, strength, and dimensional stability, homopolymer polypropylene is preferred as the main component.

[0037] Considering the spinnability and strength of the fiber during manufacturing, the lower limit of the melt flow rate (MFR) of polypropylene is preferably 20 g / 10 min or more, more preferably more than 30 g / 10 min, further preferably more than 40 g / 10 min, and even more preferably more than 53 g / 10 min. The upper limit of the MFR, which can be combined with any of the above lower limits, is preferably 155 g / 10 min or less, more preferably 70 g / 10 min or less, and even more preferably 60 g / 10 min or less. The MFR is determined according to Table 1 of JIS-K7210 "Test methods for melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of plastics—thermoplastics", at a test temperature of 230°C and a test load of 2.16 kg.

[0038] When polyethylene is used for the fiber, it can be either polyethylene synthesized using a conventional Ziegler-Natta catalyst or polyethylene synthesized using a single-active-center catalyst, such as metallocene. The polyethylene is preferably high-density polyethylene or linear low-density polyethylene. The density of the polyethylene is preferably 0.92 g / cm³.3 Above and 0.97 g / cm 3 Below, more preferably 0.925 g / cm 3 Above and 0.96 g / cm 3 The following applies. Polyethylene can be used alone or in combination of two or more types. From the viewpoint of fiber adhesion, it is preferable to use high-density polyethylene with 0.5 wt% or more and 25 wt% or less of linear polyethylene.

[0039] From the viewpoint of spinnability in manufacturing, the lower limit of the melt index (MI) of polyethylene is preferably 10 g / 10 min or more, more preferably more than 15 g / 10 min. The upper limit of MI, which can be combined with the above lower limit, is preferably 100 g / 10 min or less, more preferably 60 g / 10 min or less, and even more preferably 40 g / 10 min or less. MI is determined according to Table 1 of JIS-K7210 "Test methods for melt mass flow rate (MFR) and melt volumetric flow rate (MVR) of plastics - thermoplastics", at a test temperature of 190°C and a test load of 2.16 kg.

[0040] When using polyester-based resins, the solution viscosity η of the resin is... sp / c(η sp The lower limit of the specific viscosity (where c is the unit concentration of the resin) is preferably 0.2 or more, more preferably 0.6 or more. The solution viscosity η can be any combination of the above lower limits. sp The upper limit of / c is preferably 0.9 or less, more preferably 0.8 or less.

[0041] The aspect ratio (warp / cross) of the variation value (MMD) of the average coefficient of friction obtained by the KES method for nonwoven fabrics is 0.5 or more, preferably 0.55 or more, and more preferably 0.60 or more. "Warp" refers to the flow direction (MD direction) in the nonwoven fabric manufacturing process, and "cross" refers to the width direction perpendicular to the warp direction (CD direction). If the aspect ratio of the average coefficient of friction is 0.5 or more, the added liquid diffuses well on the surface of the nonwoven fabric, thus increasing the amount of liquid remaining after flow. Therefore, it can be suitable as a substrate for SAP sheets. The upper limit of the aspect ratio of the variation value (MMD) is preferably less than 1.00, more preferably less than 0.9.

[0042] From the viewpoint of reducing skin irritation, the absolute value of the average coefficient of friction obtained using the KES method is preferably 0.0010 or more and 0.0100 or less in the longitudinal direction (MD direction), more preferably 0.0020 or more and 0.0090 or less, and even more preferably 0.0030 or more and 0.0080 or less in the transverse direction (CD direction), preferably 0.0050 or more and 0.0200 or less, more preferably 0.0060 or more and 0.0150 or less, and even more preferably 0.0070 or more and 0.01200 or less.

[0043] The napping grade of the nonwoven fabric obtained using the Martindale process is 4 or lower, preferably 3 or lower. More specifically, in a friction test using the Martindale process, when the same nonwoven fabric is used as the friction element and the test is conducted with a load of 9 kPa and 16 cycles, the nonwoven fabric exhibits at least one of the following: surface roughness, pilling, porosity, and tearing, preferably at least one of these. If the napping grade obtained using the Martindale process is 4 or lower, the fiber adhesion is not too strong, making it easy to load SAP (superficial polymeric substances) inside the nonwoven fabric. The napping grade is preferably higher than 1.5. More specifically, it is preferable that there are no porosity or tearing in the nonwoven fabric during the aforementioned friction test. If the grade exceeds 1.5, the fiber adhesion is sufficient, the strength of the nonwoven fabric increases, and therefore the nonwoven fabric is less prone to breakage during the diaper manufacturing process.

[0044] The average fiber diameter of the nonwoven fabric fibers is preferably 8.0 μm or more and 38.0 μm or less, more preferably 9.0 μm or more and 33.5 μm or less, and even more preferably 11.0 μm or more and 26.5 μm or less. From the viewpoint of spinning stability, the average fiber diameter is preferably 8.0 μm or more, and from the viewpoint of the hand feel of the nonwoven fabric used as a hygiene material, it is preferably 38.0 μm or less.

[0045] The preferred area weight of nonwoven fabric is 5 g / m². 2 Above and 80g / m 2 Below, more preferably 8g / m 2 Above and 40g / m 2 The following is a further preferred option: 10g / m 2 Above and 30g / m 2 The following applies if the weight per unit area is 5g / m². 2 The above-mentioned nonwoven fabrics used as sanitary materials have preferred strength. If the weight per unit area is 80 g / m²... 2 The following non-woven fabrics used as sanitary materials fully satisfy the requirements of feel and appearance, and do not easily give the impression of being too thick.

[0046] 1.25 g / cm³ for nonwoven fabrics2 The thickness under load is preferably 140 μm or more, more preferably 140 μm or more and 3000 μm or less, and even more preferably 140 μm or more and 2000 μm or less. If 1.25 g / cm³ 2 When the thickness under load is above 140μm, the nonwoven fabric exhibits excellent hand feel, water permeability, and moisture recovery properties. If the thickness is below 3000μm, the nonwoven fabric used as a sanitary material adequately meets the requirements for hand feel and does not give the impression of being too thick.

[0047] Nonwoven fabrics may contain water-permeable agents. There are no particular limitations on the water-permeable agents used; however, considering safety to the human body and safety during processing, examples include nonionic surfactants formed by the addition of ethylene oxide to higher alcohols, higher fatty acids, and alkylphenols; anionic surfactants such as alkyl phosphate salts and alkyl sulfates; and surfactants composed of these alone or in mixtures. Preferred water-permeable agents include, for example, polyglycerol fatty acid esters, sorbitol fatty acid esters, polyether-polyester block copolymers, polyvinyl ether-modified silicones, polyether-modified silicones, polyols that have undergone addition of ethylene oxide, and polyamide compounds.

[0048] The amount of the water-permeable agent is generally preferably 0.10 wt% or more and 2.00 wt% or less, more preferably 0.15 wt% or more and 1.50 wt% or less, relative to the nonwoven fabric. Sufficient water permeability is obtained when it is 0.10 wt% or more, while it is less likely to cause inflammation or eczema on the skin when it is 1.50 wt% or less.

[0049] Manufacturing method of nonwoven fabrics for sanitary materials

[0050] From the perspective of strength and productivity, nonwoven fabrics are preferably manufactured using the spunbond method. The following details the manufacturing method using the spunbond method; however, the nonwoven fabrics disclosed herein are not limited to those manufactured using the spunbond method.

[0051] Thermoplastic resin is melt-extruded from an extruder and extruded from a spinning spinneret with many spinning holes. In the case of forming a nonwoven fabric containing composite long fibers composed of two or more thermoplastic resins, for example, it can be manufactured by melt-extruded different thermoplastic resins separately from two or more different extruders and extruded from a spinning spinneret with many spinning holes in the form of filaments in the state of being combined with two or more thermoplastic resins.

[0052] Next, the ejected filaments are cooled by blowing cold air at a temperature controlled between 3°C and 28°C, while being pulled by a traction device. The filaments from the traction device are piled onto a conveyor belt to form a woven sheet, which is then conveyed. Other woven sheets can be further layered on top of the conveying woven sheet. In the case of layered nonwoven fabrics, woven sheets with different fiber diameters can be used to form each layer, or woven sheets formed by fibers with special shapes such as shaped cross-section filaments, crimped fibers, and hollow fibers can be layered.

[0053] The fabrics manufactured as described above are integrally formed into a nonwoven fabric through bonding. The bonding of the fabrics can be carried out by methods such as bonding with adhesives; bonding with low-melting-point fibers or composite fibers; fusion bonding by dispersing hot-melt adhesives during fabric formation; or interlacing fibers by methods such as needle punching or water jetting, etc., without particular limitation.

[0054] From the viewpoint of easily maintaining the surface structure of nonwoven fabrics, especially in the case of composite long fibers composed of two or more thermoplastic resins, a bonding method is preferred, which involves heating to a temperature above which the intersections of the fibers melt and can be bonded. Various heating methods can be used, such as hot air circulation, hot air penetration, infrared heaters, methods of spraying hot air onto both sides of the nonwoven fabric, and methods of introducing heat into a heating gas. From the viewpoint of obtaining more fiber bonding points at the intersections of the fibers, thereby improving the tensile strength of the nonwoven fabric, heating using hot air is preferred, and hot air penetration is particularly preferred.

[0055] Conventionally, from the perspective of equipment maintenance and high-speed production, it is preferable to have short heat treatment times and high temperatures and air velocities during the bonding process for fiber bonding. However, in the manufacturing of the nonwoven fabric of this embodiment, from the viewpoint of increasing the load of SAP as a substrate, it is preferable to bond at low temperatures and air velocities. If bonding is performed at low temperatures and air velocities, the strength of the resulting nonwoven fabric will be weakened, and the nonwoven fabric may break during the manufacturing process of the sanitary material. Therefore, it is necessary to extend the heat treatment time. In order to exhibit the strength that can be used in the manufacturing process as a sanitary material, the heat treatment time is preferably 0.5 seconds or more and 10 seconds or less, more preferably 0.5 seconds or more and 5 seconds or less, and even more preferably 1 second or more and 5 seconds or less. If the heat treatment time is 10 seconds or less, the adhesion between the fibers will not be too strong, and the hand feel will be good.

[0056] The hot air velocity is preferably 0.1 m / s or higher and 3.0 m / s or lower, more preferably 0.5 m / s or higher and 3.0 m / s or lower, and even more preferably 1.0 m / s or higher and 3.0 m / s or lower. If it is 0.5 m / s or higher, heat is sufficiently transferred to the interior of the nonwoven fabric, thus ensuring sufficient adhesion between the fibers. If it is 3.0 m / s or lower, damage to the nonwoven fabric caused by the air velocity can be suppressed, increasing the amount of SAP retained as a substrate for SAP sheets.

[0057] Embossing can be used for bonding as long as it does not adversely affect the surface structure of the nonwoven fabric. From a productivity point of view, embossing is preferably performed by passing the fabric through a pair of rollers, a combination of a metal embossing roller and a metal smoothing roller. From the viewpoint of maintaining the shape of the fabric and the strength of the final nonwoven fabric, the embossing area ratio, i.e., the ratio of the area of ​​the embossed portion (bonded portion) to the total area of ​​the nonwoven fabric, is preferably 5% or more and 30% or less, more preferably 5% or more and 20% or less, and even more preferably 6% or more and 15% or less. The deeper the embossing, the easier it is to maintain the thickness of the nonwoven fabric; preferably 0.5 mm or more and 2.0 mm or less, even more preferably 0.7 mm or more and 1.5 mm or less. The embossing shape is not particularly limited, but round, elliptical, diamond, rectangular, and combinations thereof are preferred.

[0058] As a method for applying the water-permeable agent, existing methods such as coating (e.g., gravure coating machine, kiss coating machine) and spraying can be used, or pretreatment such as corona discharge treatment or atmospheric pressure plasma discharge treatment can be performed as needed. As a drying method after coating, existing methods that utilize convective heat transfer, heat conduction, and radiative heat transfer can be used, as well as drying methods that utilize hot air, infrared rays, or thermal contact.

[0059] The permeable agent can be diluted with solvents such as water and applied in the form of an aqueous solution. To avoid insufficient drying during the drying process associated with high-speed equipment operation, a low coating amount of the permeable agent aqueous solution is preferable. For the coating amount (wt%) of the nonwoven fabric, in any of the above coating methods, it is preferably 1.0 wt% or more and 65 wt% or less, more preferably 3.0 wt% or more and 60 wt% or less, and even more preferably 5.0 wt% or more and 50 wt% or less. If the coating amount is 1.0 wt% or more, uniform coating is easily achieved; on the other hand, if it is 65 wt% or less, the drying capacity required in the subsequent drying process is reduced, thus lowering equipment costs and preventing insufficient drying.

[0060] In the application of a water-permeable agent using a gravure coating machine, the pattern of the gravure roller can be, for example, a grid pattern or a pyramidal pattern, but is preferably a diagonal pattern where the water-permeable agent is less likely to remain at the bottom of the groove. The groove volume is preferably 5 cm³. 3 / m 2 Above and 40cm 3 / m 2 The following applies if the tank volume is 5 cm³. 3 / m 2 The above methods make it easy to apply the coating evenly. If the thickness is 40cm... 3 / m 2 The following measures can easily suppress insufficient drying during the drying process and uneven adhesion of the permeable agent due to migration. The depth of the grooves in the gravure printing plate is preferably 10 μm or more and 80 μm or less, and the groove spacing is preferably 80 mesh or more and 250 mesh or less.

[0061] From the perspective of ease of equipment management, coating using a kissing machine with a stainless steel application roller is preferred. A water-permeable aqueous solution is continuously supplied to the bath, and a rotating roller is brought into contact with the nonwoven fabric within the bath, thereby applying the water-permeable aqueous solution. The amount of water-permeable coating can be easily adjusted by setting the rotation speed of the kiss roll every minute.

[0062] From the viewpoints of being able to handle high-speed equipment, effectively coating, and easily maintaining the thickness of the nonwoven fabric, coating of the permeable agent using a spray method is preferred. As a spray method, air spraying can be used, where compressed air is used to form a fine mist of the permeable agent aqueous solution and then spray it out; or rotor humidification can be used, where the centrifugal force of a rotating rotor forms a mist of the permeable agent aqueous solution and then sprays it. When applying the permeable agent aqueous solution using a spray method, the spray direction can be spraying only one side of the nonwoven fabric or spraying both sides.

[0063] The drying of the waterproofing agent aqueous solution after coating can be carried out using conventional drying methods without particular limitations. Known methods such as convective heat transfer, heat conduction, and radiative heat transfer can be employed. For example, various drying methods can be used, such as hot air circulation, hot air penetration, infrared heaters, spraying hot air onto both sides of the nonwoven fabric, or introducing the material into a heated gas.

[0064] To adjust the ratio (longitudinal / transverse) of the variation value of the average coefficient of friction (MMD) obtained using the KES method to 0.5 or more, in the case of spunbond fabric, the width of the longitudinal direction (MD direction) of the drawn yarn when it touches the conveyor (the drop width from the outlet of the traction device to the conveyor) is preferably 30 mm or more. The reason for this is not theoretically limited, but it is believed that by setting the drop width to 30 mm or more, the coiled fibers will not entangle and the fibers will form an appropriate arrangement. From the viewpoint of suppressing the reduction in SAP load due to the thinning of the nonwoven fabric, the drop width is preferably 500 mm or less, more preferably 300 mm or less, and even more preferably 200 mm or less. It should be noted that the flow direction (the direction of fiber orientation) in nonwoven fabric manufacturing is defined as the longitudinal direction, and the direction perpendicular to the flow direction in the plane of the nonwoven fabric is defined as the transverse direction. Furthermore, to ensure that the drop width is 30 mm or more and 500 mm or less, it is preferable to adjust the distance (height) between the conveyor and the diffuser.

[0065] To adjust the nap grade obtained using the Martindale process to level 4 or below, when using a hot air bonding method, it is preferable to adjust the hot air temperature to a temperature suitable for the thermoplastic resin that contributes to bonding. For example, in the case of a nonwoven fabric formed from composite fibers containing polyethylene and polypropylene, the temperature at which the polyethylene is melted and bonded is preferably 160°C or below, more preferably 150°C or below, further preferably 140°C or below, and most preferably 130°C or below. If the temperature is below 160°C, it is easy to obtain a nap grade of level 4 or below using the Martindale process, and it is easy to have sufficient water retention. As a lower limit that can be arbitrarily combined with the above upper limits, from the viewpoint of ensuring sufficient bonding between the fibers, the bonding temperature is preferably 100°C or above. To adjust the nap grade obtained using the Martindale process to level 4 or below, the traction speed is adjusted to a degree where the number of curls is preferably more than 3 / 2.5cm, more preferably more than 5 / 2.5cm. The reason is not limited by theory, but is believed to be that the increase in loops of fibers on the surface of nonwoven fabric due to the number of curls exceeding 3 / 2.5cm results in a tendency to pill.

[0066] Substrates for SAP Sheets, SAP Sheets, and Sanitary Materials

[0067] The SAP sheet substrate disclosed herein contains the nonwoven fabric for hygiene materials of this disclosure and can be combined with any other nonwoven fabric for hygiene materials. The SAP sheet substrate is preferably formed from the nonwoven fabric for hygiene materials of this disclosure.

[0068] The SAP sheet disclosed herein comprises a SAP sheet substrate and SAP (superabsorbent polymer). SAP generally refers to a polymeric compound capable of absorbing and retaining water up to several hundred times its own weight, up to about a thousand times its own weight. Examples of SAP are not limited to polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, and polyacrylic acid polymers. From the viewpoint of high absorbency, polyacrylic acid polymers are preferred, and sodium polyacrylate is more preferred. The SAP sheet preferably has SAP loaded onto the SAP sheet substrate.

[0069] The sanitary materials disclosed herein contain the SAP sheets of this disclosure. Examples of sanitary materials include, for instance, diapers, face masks, hand warmers, backing fabrics for bandages, medicated patches, bandage backing fabrics, packaging materials, wiping products, medical gowns, bandages, clothing, and skin care sheets. Due to the excellent water retention, SAP load-bearing capacity, and liquid permeability of the nonwoven fabric used in the sanitary materials of this disclosure, diapers are preferred sanitary materials.

[0070] Example

[0071] The embodiments and comparative examples of this disclosure are described in detail below, but this disclosure is not limited to the following embodiments. It should be noted that the evaluation methods for each characteristic are as follows, and the obtained physical properties are shown in Table 1 below. The flow direction in the manufacturing of nonwoven fabric is referred to as the MD direction (longitudinal direction), and the width direction forming a right angle with this direction is referred to as the CD direction (transverse direction).

[0072] <Average fiber diameter (μm)>

[0073] The nonwoven fabric was divided into 5 equal parts along the CD direction of 1m. A 1cm square sample was collected from the center of each of the 5 equal parts. The diameter of the fibers was measured at 20 points on each sample using a KEYENCE CORPORATION VHX-700F microscope, and the average value was calculated.

[0074] <weight per unit area (g / m²) 2 )>

[0075] According to JIS-L1906:2000, five samples of 20cm in the MD direction and 5cm in the CD direction of the nonwoven fabric were collected at equal sampling locations along the CD direction and their mass was measured. The average value was converted into the weight per unit area as the weight per unit area (g / m²). 2 Find the answer.

[0076] <Aspect ratio of the variation in average friction coefficient (MMD) obtained using the KES method>

[0077] Five 200cm × 200cm samples were collected by dividing 1m along the CD direction of the nonwoven fabric into five equal parts. For each sample, it was mounted on the testing table of a KATO TECH CO.,LTD. automated surface testing machine (KES-FB4A). A standard friction element (10mm square metal wire friction element) was moved 30mm across the sample with a testing load of 50gf, a tension of 400gf / 20cm, and a moving speed of 1mm / min. The variation in the average coefficient of friction was calculated from the data at a center distance of 20mm. Measurements were performed in both the longitudinal (MD) and transverse (CD) directions of the five samples, and the average values ​​were set as the variation in the average coefficient of friction in the longitudinal and transverse directions, respectively. The ratio of the variation in the average coefficient of friction in the longitudinal direction to the variation in the average coefficient of friction in the transverse direction was calculated as the longitudinal-to-transverse ratio of the variation in the average coefficient of friction.

[0078] <Pile-up Grade (Level)>

[0079] Using a Martindale abrasion / pilling tester manufactured by Groz-Beckert, the Martindale method (WSP20.5(05)) was applied according to the following procedure: (WSP20.5(05)) (wherein, a nonwoven fabric sample is placed on a 155mm diameter polyurethane foam (model HEA786-255, purchased from GROZ-BECKERT JAPAN KK), which is not felt. Additionally, a 38mm diameter polyurethane foam (same as above) is sandwiched between the friction surface and the nonwoven fabric to form a friction surface). The sample was rubbed with a load of 9 kPa and 16 rubs. The pilling condition of the sample after rubbing was observed, and the grade was visually determined. Tests were performed on both sides of the sample at N=5, and the average value was obtained. The grade of the surface with more pilling (lower pilling grade) was used. It should be noted that the grades and evaluation criteria described in this disclosure are in the reverse order of the grades described in the description of Japanese Patent Application No. 2021-080917, which is the basic application for which this application has priority, but there are no changes except for the order. The grades and evaluation criteria of this disclosure and the basic application correspond as follows.

[0080] Level 5 (Level 1 in the basic application): No change.

[0081] Level 4 (Level 2 in the basic application): Rough surface.

[0082] Level 3 (Level 3 in the basic application): Pilling exists. (Less than 5 pills)

[0083] Level 2 (Level 4 in the basic application): Pilling found on the entire surface. (5 or more pills)

[0084] Level 1 (Level 5 in the basic application): Pores and cracks exist.

[0085] <Amount of permeable agent (wt%)>

[0086] The weight W1 (mg) of a nonwoven fabric sample with a water-permeable agent applied after 24 hours of conditioning at 25°C and 40% RH was measured, and the weight W2 (mg) of the extract obtained from the nonwoven fabric sample using a rapid extraction device (INTEC CO.,LTD.) with methanol was determined, and the amount of water-permeable agent C (wt%) was calculated using the following formula.

[0087] C(wt%) = [W2 / W1] × 100

[0088] It should be noted that for the collection of nonwoven fabric samples, five samples were collected at 30cm intervals along the MD direction and five samples at equal intervals along the CD direction within the width of the nonwoven fabric. Ten samples were collected, each with a width of 5cm to 10cm and a length of approximately 2g. These ten samples were then measured, and their average value was taken as the amount of permeable agent (wt%).

[0089] <Number of curls (each per 2.5cm)>

[0090] The nonwoven fabric was divided into 5 equal parts along the CD direction. A 5cm square sample was collected from the center of each of the 5 parts. For each sample, 5 fibers were removed using tweezers and scissors while observing the sample under a stereo microscope, taking care not to deform the filament structure. The removed fibers were placed in an unloaded state, and the number of curls per 2.5cm length was measured. The average number of curls (number of curls per 2.5cm) was calculated.

[0091] <Water retention (g)>

[0092] A sample of nonwoven fabric was taken and its weight measured at a distance of 150 mm in the MD direction and 150 mm in the CD direction. The sample was fixed to the mouth of a 300 mL beaker using a rubber band. 100 mL of physiological saline was added dropwise from 25 mm above the center of the sample at a rate of 2 mL / s. After adding the saline, the sample was removed after 5 minutes, and its weight was measured. The difference between the measured weight and the weight of the sample was defined as the water retention (g). It should be noted that a water retention of 0.5 g or higher indicates good absorbency and reduces the likelihood of leakage when used as a diaper.

[0093] <SAP Load (%)>

[0094] A sample of the nonwoven fabric was taken from a 150mm x 150mm section along the MD direction and its weight was measured (this weight is designated as weight A (mg)). The nonwoven fabric sample was placed between a tray and a sieve (75mm inner diameter x 20mm inner height, 2.36mm aperture), and 10g of SAP was dropped onto the sieve. The tray, nonwoven fabric sample, and sieve containing SAP were then mounted on a sieve vibrator (MICRO VIBRO SIFTER MODEL M-2), with the volume set to 1, and vibrated for 1 minute. After vibration, the nonwoven fabric was held by one side, with the SAP falling onto its surface, and removed vertically. The weight was immediately measured using a balance (this weight is designated as weight B (mg)). The SAP loading percentage was calculated using the following formula.

[0095] SAP load (%) = [(weight B (mg) - weight A (mg)) / weight A (mg)] × 100

[0096] It should be noted that the SAP used has the following particle size distribution.

[0097] Greater than 0 μm and less than 200 μm...1%

[0098] More than 200μm and less than 400μm...5%

[0099] More than 400μm and less than 600μm…24%

[0100] More than 600μm and less than 800μm...35%

[0101] More than 800μm but less than 1000μm…25%

[0102] 10% of the size ranges from over 1000 μm to below 1200 μm.

[0103] <Repeated water permeability rate>

[0104] Two samples of nonwoven fabric were taken in a manner that formed a MD direction of 150mm × CD direction of 150mm, and the sample was taken from one of the sheets to form a 1g / m² sample. 2The method involves uniformly applying hot melt adhesive to the entire surface of the nonwoven fabric using a spray-type hot melt gun, followed by evenly sprinkling 5g of SAP. After sprinkling SAP, another sheet of nonwoven fabric is overlapped to create a simple SAP sheet with a 3-layer structure of nonwoven fabric / SAP / nonwoven fabric. A 125mm square sample is taken from the prepared simple SAP sheet and placed on a slightly larger plastic plate. A LISTER test plate manufactured by LENZING INSTRUMENTS, used in the STRIKE-THROUGH method according to EDANA standards, is then placed on top. 20mL of physiological saline is added from a 30mm drop, designated as the first drop. The same procedure is repeated every 30 minutes. After the third drop, the value indicated by the LISTER is designated as the third permeability rate.

[0105] <MD tensile strength (N / 50mm)>

[0106] According to JIS-L1913:2010, five samples of 30cm in the MD direction and 5cm in the CD direction of the nonwoven fabric were collected with equal sampling positions in the CD direction. The tensile strength was measured, and the average value of the five samples was set as the MD tensile strength.

[0107] Examples and Comparative Examples

[0108] [Example 1]

[0109] Polypropylene (PP) resin with an MFR of 55 g / 10 min (measured according to JIS-K7210 at 230°C and 2.16 kg load) was used as the first component, and high-density polyethylene (HDPE) resin with an MI of 26 g / 10 min (measured according to JIS-K7210 at 190°C and 2.16 kg load) was used as the second component. Using a parallel-type spinning spinneret, the total extrusion rate was set to 0.8 g / min per hole. The filaments were extruded at a spinning temperature of 220°C with a PP / PE ratio of 3 / 2 (first component to second component). The extruded filaments were stretched within the traction zone by the suction force of the conveyor and then deposited on the conveyor surface through a diffuser to form a fabric. The distance (height) between the conveyor and the diffuser was adjusted so that the fiber's MD direction drop width was 50 mm. The obtained fabric is then subjected to hot air blowing at 125℃ and 1.2m / s for 3 seconds to obtain a nonwoven fabric.

[0110] Next, the obtained nonwoven fabric was adjusted to a liquid temperature of 20°C, and a 5 wt% aqueous solution of a permeable agent (referred to as A in the table) containing polyoxyethylene fatty acid glycerol esters and polyether-modified silicone was applied simultaneously using a coating machine with a coating amount of 10 wt% while adjusting the angle and rotation speed of the stainless steel coating roller. Then, the fabric was dried in a cylindrical dryer at 125°C to obtain the nonwoven fabric.

[0111] [Example 2]

[0112] The distance (height) between the conveyor and the diffuser is adjusted so that the drop width of the fiber in the MD direction is 60mm. Otherwise, the same method as in Example 1 is used to adjust the distance to obtain the nonwoven fabric.

[0113] [Example 3]

[0114] The distance (height) between the conveyor and the diffuser is adjusted so that the drop width of the fiber in the MD direction is 70mm. Otherwise, the same method as in Example 1 is used to adjust the distance to obtain the nonwoven fabric.

[0115] [Example 4]

[0116] The distance (height) between the conveyor and the diffuser is adjusted so that the width of the fiber drop in the MD direction is 100mm. Otherwise, the same method as in Example 1 is used to adjust the distance to obtain the nonwoven fabric.

[0117] [Example 5]

[0118] The fiber drop width in the MD direction was set to 80 mm, the bonding temperature was set to 110°C, and the nonwoven fabric was obtained using the same method as in Example 1.

[0119] [Example 6]

[0120] The bonding temperature was set to 120°C, and the nonwoven fabric was obtained using the same method as in Example 5.

[0121] [Example 7]

[0122] The bonding temperature was set to 125°C, and the nonwoven fabric was obtained using the same method as in Example 5.

[0123] [Example 8]

[0124] The bonding temperature was set to 130°C, and the nonwoven fabric was obtained using the same method as in Example 5.

[0125] [Example 9]

[0126] The bonding temperature was set to 140°C, and the nonwoven fabric was obtained using the same method as in Example 5.

[0127] [Example 10]

[0128] In the coating of the permeable agent, the liquid temperature is adjusted to 20°C by rotor humidification, and a 5wt% aqueous solution of the permeable agent is coated with a coating amount of 10wt%. The solution is then dried and wound up using a cylindrical dryer at 120°C. Otherwise, the nonwoven fabric is obtained using the same method as in Example 7.

[0129] [Example 11]

[0130] The water-permeable agent was a mixture of polyoxyalkylene alkyl ether and polyether-modified organosilicon (the water-permeable agent is recorded as B in the table), and the nonwoven fabric was otherwise obtained using the same method as in Example 7.

[0131] [Example 12]

[0132] The permeable agent was set as a mixture of polyoxyethylene fatty acid glycerol ester, alkyl phosphate ester, and lauryl diethanolamine (the permeable agent is recorded as C in the table), and the nonwoven fabric was otherwise obtained using the same method as in Example 7.

[0133] [Example 13]

[0134] The traction speed was adjusted to form 23 curls per 2.5 cm, and the nonwoven fabric was otherwise obtained using the same method as in Example 7.

[0135] [Example 14]

[0136] The traction speed was adjusted to form 28 curls per 2.5 cm, and the nonwoven fabric was otherwise obtained using the same method as in Example 7.

[0137] [Example 15]

[0138] The solution viscosity η sp Polyethylene terephthalate (PET) resin with a ratio of 0.75 was used as the first component, and high-density polyethylene (PE) resin (the same as in Example 1) was used as the second component. A parallel-type spinning spinneret was used, and the total extrusion rate was set to 0.8 g / min·hole. The filaments were extruded at a spinning temperature of 295°C with a PP / PE ratio of 1:1 (PPPET / PE = 1:1). The extruded filaments were stretched within the traction zone by the suction force of a conveyor and then deposited on the conveyor surface through a diffuser to form a fabric. The distance (height) between the conveyor and the diffuser was adjusted so that the fiber drop width in the MD direction was 80 mm. The resulting fabric was then subjected to hot air blowing at 135°C and a wind speed of 1.2 m / s for 3 seconds to obtain a nonwoven fabric.

[0139] Next, the obtained nonwoven fabric was adjusted to a liquid temperature of 20°C, and a 5 wt% aqueous solution of a permeable agent (referred to as D in the table) containing dehydrated sorbitol fatty acid ester and sodium dioctyl sulfosuccinate was applied using a coating machine with the coating amount adjusted to 10 wt% while adjusting the angle and rotation speed of the stainless steel coating roller. The nonwoven fabric was then dried in a cylindrical dryer at 125°C to obtain the nonwoven fabric.

[0140] [Example 16]

[0141] Using solution viscosity η sp A sheath-core composite fiber (fiber diameter 2.5 dtex) with a fiber length of 38 mm was formed using polyethylene terephthalate (PET) with a core component of 0.75 and high-density polyethylene (PE) (the same as in Example 1) as the sheath component. This fiber was then carded to form a fabric. The fabric was then subjected to hot air blowing at 135°C and a wind speed of 1.2 m / s for 5 seconds to thermally fuse the fibers together, resulting in a nonwoven fabric. The pull ratio of the winding was adjusted by stretching the nonwoven fabric in the MD direction to obtain the final nonwoven fabric.

[0142] [Comparative Example 1]

[0143] The traction speed was adjusted to form 32 curls per 2.5 cm, and the nonwoven fabric was otherwise obtained using the same method as in Example 7.

[0144] [Comparative Example 2]

[0145] The distance (height) between the conveyor and the diffuser is adjusted so that the falling width of the fiber in the MD direction is 40 mm. Otherwise, the nonwoven fabric is obtained using the same method as in Example 7.

[0146] [Comparative Example 3]

[0147] The traction speed was adjusted to form 3 curls per 2.5 cm, and the bonding temperature was set to 145°C. Otherwise, the nonwoven fabric was obtained using the same method as in Example 7.

[0148] [Table 1]

[0149]

[0150] [Table 2]

[0151]

[0152] Industrial availability

[0153] The nonwoven fabric for hygiene materials disclosed herein possesses excellent water retention, SAP load-bearing capacity, and liquid permeability, making it suitable for use as a substrate for SAP pads. Furthermore, the nonwoven fabric for hygiene materials disclosed herein can also be used as a component in diapers, such as a top layer or a second layer. Moreover, the nonwoven fabric for hygiene materials disclosed herein can also be used, for example, in masks, hand warmers, backing fabrics for bandages, medicated patch backing fabrics, bandage backing fabrics, packaging materials, wiping products, medical gowns, bandages, clothing, and skin care pads.

Claims

1. A nonwoven fabric for sanitary materials, wherein the aspect ratio of the variation value of the average coefficient of friction obtained by the KES method, i.e., the aspect ratio of the width to the width, is 0.5 or more and less than 1.00, and in a friction test conducted using the Martindale method, the same nonwoven fabric as the sanitary material is used as the friction element, and when the friction test is conducted with a load of 9 kPa and 16 cycles, any one or more of the following occurs: surface roughness, pilling, porosity, and cracking. The nonwoven fabric is composed of composite fibers, wherein the composite fibers are composed of polyolefin resins combined with each other, and the number of crimps of the fibers constituting the sanitary material nonwoven fabric is 5 or more / 2.5 cm and less than 30 crimps / 2.5 cm.

2. The nonwoven fabric for sanitary materials according to claim 1, wherein, in a friction test using the Martindale method, the same nonwoven fabric as the nonwoven fabric for sanitary materials is used as the friction element, and the friction test is conducted with a load of 9 kPa and 16 friction cycles, any one or more of the following occurs: pilling, pores, and cracks.

3. The nonwoven fabric for sanitary materials according to claim 1 or 2, wherein the unit area weight is 5 g / m². 2 Above and 80g / m 2 the following.

4. The nonwoven fabric for sanitary materials according to claim 1 or 2, which is composed of fibers with a fiber length of 50 mm or more.

5. The nonwoven fabric for sanitary materials according to claim 1 or 2, wherein it is a spunbond nonwoven fabric.

6. The nonwoven fabric for sanitary materials according to claim 1 or 2, wherein it contains a water-permeable agent.

7. A substrate for SAP sheets comprising the nonwoven fabric for sanitary materials as described in claim 1 or 2.

8. An SAP sheet comprising the SAP sheet substrate of claim 7 and SAP.

9. A sanitary material comprising the SAP sheet as described in claim 8.

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