Nonwoven fabric for sanitary materials, base material for sap sheets, and sap sheet

Abstract

The present disclosure provides a nonwoven fabric for sanitary materials, the nonwoven fabric being excellent in terms of liquid retainability, SAP supporting capacity and water permeability, thereby being suitable as a base material for SAP sheets. With respect to a nonwoven fabric for sanitary materials according to the present disclosure, the height-width ratio of the mean deviation of the friction coefficient (MMD) as determined by a KES method is 0.5 or more; and the fuzz grade as determined by a Martindale method is grade 4 or less.

Description

Nonwoven fabric for sanitary materials, substrate for SAP sheet, and SAP sheet

[0001] The present disclosure relates to a nonwoven fabric for sanitary materials, a substrate for an SAP sheet, and an SAP sheet.

[0002] Diapers are basically composed of a top sheet, absorbent body, back sheet, and leg cuffs. The absorbent body is usually a mixture of SAP (super absorbent polymer) and pulp wrapped in nonwoven fabric or tissue paper. However, to make diapers thinner, nonwoven fabrics carrying SAP (SAP sheets) are sometimes used. The substrate for SAP sheets must be able to carry a large amount of SAP, not impede water permeability to the SAP, and be able to retain water itself.

[0003] Patent Document 1 listed below discloses an SAP sheet in which SAP is embedded and supported in a substrate that is a planar web made of hydrophilic and crimped long fibers.

[0004] Japanese Patent Application Laid-Open No. 2006-110329

[0005] However, there is a demand for a substrate for an SAP sheet with higher performance than the substrate for an SAP sheet of Patent Document 1, in particular a substrate for an SAP sheet with excellent liquid retention.

[0006] In view of the problems of the prior art described above, an object of the present disclosure is to provide a nonwoven fabric for sanitary materials that is excellent in liquid water retention, SAP loading, and water permeability, and is suitable as a substrate for SAP sheets.

[0007] Examples of embodiments of the present disclosure are listed in the following items [1] to

[14] . [1] A nonwoven fabric for sanitary materials, having a length-to-width ratio (length / width) of the mean coefficient of friction variation (MMD) measured by the KES method of 0.5 or more and a fuzz rating of 4 or less measured by the Martindale method. [2] The nonwoven fabric for sanitary materials according to item [1], having a fuzz rating of 3 or less measured by the Martindale method. [3] A nonwoven fabric for sanitary materials, having a length-to-width ratio (length / width) of the mean coefficient of friction variation (MMD) measured by the KES method of 0.5 or more, wherein, in a friction test using the same nonwoven fabric as the nonwoven fabric for sanitary materials as the friction element, at a load of 9 kPa and 16 friction cycles, the nonwoven fabric for sanitary materials exhibits one or more of surface roughness, pilling, holes, and tears. [4] The nonwoven fabric for sanitary materials according to item [3], wherein, in a friction test by the Martindale method, the same nonwoven fabric as the nonwoven fabric for sanitary materials is used as a friction element, and the friction test is performed 16 times under a load of 9 kPa, and one or more of pilling, holes, and tears occur. [5] The nonwoven fabric for sanitary materials has a basis weight of 5 g / m ２ 80g / m or more ２ The nonwoven fabric for sanitary materials according to any one of items [1] to [4], which is as follows: [6] The nonwoven fabric for sanitary materials according to any one of items [1] to [5], which is composed of fibers having a fiber length of 50 mm or more. [7] The nonwoven fabric for sanitary materials according to any one of items [1] to [6], which is a spunbonded nonwoven fabric. [8] The nonwoven fabric for sanitary materials according to any one of items [1] to [7], which contains a water-permeable agent. [9] The nonwoven fabric for sanitary materials according to any one of items [1] to [8], which contains fibers having a number of crimps of 3 or more per 2.5 cm and 45 or less per 2.5 cm.

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

[11] A substrate for an SAP sheet, which contains the nonwoven fabric for sanitary materials according to any one of items [1] to

[10] .

[12] The substrate for SAP sheets according to item

[11] , wherein the nonwoven fabric for sanitary materials is a spunbonded nonwoven fabric having a Martindale fluff grade of 3 or less and containing a polyolefin resin.

[13] An SAP sheet comprising the substrate for SAP sheets according to item

[11] or

[12] and an SAP.

[14] A sanitary material comprising the SAP sheet according to item

[13] .

[0008] The nonwoven fabric for sanitary materials of the present disclosure has excellent liquid retention, SAP loading, and water permeability, and is therefore suitable for use as a substrate for SAP sheets.

[0009] <<Nonwoven Fabric for Hygiene Materials>> The nonwoven fabric for hygiene materials (hereinafter also simply referred to as "nonwoven fabric") of the present disclosure has a length to width ratio of the mean coefficient of friction variation (MMD) measured by the KES (KAWABATA EVALUATION SYSTEM) method of 0.5 or more. The nonwoven fabric for hygiene materials of the present disclosure is characterized by having a fuzz grade of 4 or less by the Martindale method, or exhibiting one or more of surface roughness, pilling, holes, and tears when a friction test by the Martindale method is performed using the same nonwoven fabric as the nonwoven fabric for hygiene materials as a friction element at a load of 9 kPa and 16 friction cycles.

[0010] The nonwoven fabric may be either a long-fiber nonwoven fabric or a short-fiber nonwoven fabric. However, from the viewpoints of strength, productivity, and reduced skin irritation, a long-fiber nonwoven fabric is preferred, and a spunbond nonwoven fabric is particularly preferred. In the present disclosure, long fibers refer to fibers having a fiber length of 50 mm or more. In terms of fiber shedding, the longer the fiber length, the more preferable it is. The nonwoven fabric is preferably composed of fibers having 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 occurs and the better the liquid retention.

[0011] The nonwoven fabric is preferably composed of fibers made of a thermoplastic resin. Thermoplastic resins include, but are not limited to, polyolefin resins such as polyethylene, polypropylene, and copolymer polypropylene; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and copolymer polyester; polyamide resins such as nylon-6, nylon-66, and copolymer nylon; biodegradable resins such as polylactic acid, polybutylene succinate, and polyethylene succinate; and combinations thereof. The thermoplastic resins may be used alone or in combination of two or more. From the viewpoint of the texture of the nonwoven fabric, and because many of its uses are as disposable materials, polyolefin resins are preferred from the viewpoint of versatility and ease of recycling.

[0012] The fibers constituting the nonwoven fabric may be not only circular fibers but also special fibers such as modified cross-section fibers and hollow fibers. From the viewpoint of imparting distinctive features to the surface structure of the nonwoven fabric, it is preferable that the fibers are crimped. The lower limit of the number of crimps is preferably 3 crimps / 2.5 cm or more, more preferably 5 crimps / 2.5 cm or more. The upper limit, which can be arbitrarily combined with the lower limit, is preferably 45 crimps / 2.5 cm or less, more preferably 30 crimps / 2.5 cm or less, and even more preferably 20 crimps / 2.5 cm or less. When the number of crimps is 45 crimps / 2.5 cm or less, the fibers do not shrink too much, making it difficult for SAP to slip through as a substrate for an SAP sheet and improving liquid retention. When the number of crimps is 3 crimps / 2.5 cm or more, a higher amount of SAP can be supported as a substrate for an SAP sheet.

[0013] One method for crimping fibers is to form a fiber cross section with a modified cross section and then perform uneven cooling during spinning and cooling. It is also possible to induce crimp in composite fibers composed of two or more thermoplastic resins, and crimp can be easily induced by using a side-by-side (S / S) or eccentric sheath-core (eccentric S / C) type. In the case of an eccentric sheath-core (eccentric S / C) type, the core may be exposed on the fiber surface. In this case, the proportion of the core area on the fiber surface is preferably more than 0% and not more than 50%, more preferably more than 0% and not more than 30%. If the proportion of the core area on the fiber surface is 50% or less, there is little effect on adhesion during joining as a nonwoven fabric, and the fabric strength is sufficient.

[0014] When the fiber is a composite fiber composed of two or more thermoplastic resins, any of the above-mentioned thermoplastic resins may be combined as long as the desired effect is achieved, and from the viewpoint of bonding the fibers together, a combination of thermoplastic resins with different melting points is preferred. In this case, the weight ratio of the resin with the higher melting point in the fiber is preferably 20 wt % to 80 wt %, more preferably 30 wt % to 80 wt %, and even more preferably 50 wt % to 70 wt %.

[0015] From the viewpoint of the texture of the resulting nonwoven fabric, the composite fiber is preferably a combination of polyolefin-based resins, or preferably a combination of a polyolefin-based resin and a polyester-based resin. Examples of composite fibers combining polyolefin-based resins include composite fibers combining resins such as polyethylene, polypropylene, and copolymers of these monomers with other α-olefins. Other α-olefins are preferably α-olefins having 3 to 10 carbon atoms, specifically propylene, 1-butene, 1-pentene, 1-hexane, 4-methyl-1-pentene, and 1-octene. When combining a polyolefin-based resin with a polyester-based resin, the polyolefin resin is preferably a resin such as polyethylene, polypropylene, or a copolymer of these monomers with other α-olefins, and the polyester resin is preferably a polyethylene terephthalate single component or a copolymer of polyethylene terephthalate containing isophthalic acid or the like as a monomer unit. The polyethylene terephthalate may be modified by blending or the like, or may contain additives or the like. A preferred combination of thermoplastic resins is polypropylene and polyethylene, because it has high strength and is less likely to break during use, is suitable for processing during the production of sanitary materials, and has a good texture. When the composite fiber is an eccentric sheath-core type, it is preferred that the core be polypropylene and the sheath be polyethylene.

[0016] When polypropylene is used for the fibers, it may be any of polypropylene synthesized using a general Ziegler-Natta catalyst, polypropylene synthesized using a single-site active catalyst such as metallocene, and ethylene random copolymer polypropylene, and these may be used alone or in combination of two or more. From the viewpoint of texture, strength, and dimensional stability, it is preferable to use homopolypropylene as the main component.

[0017] In terms of spinnability in fiber production and fiber strength, the lower limit of the MFR of polypropylene is preferably 20 g / 10 min or more, more preferably greater than 30 g / 10 min, even more preferably greater than 40 g / 10 min, and even more preferably greater than 53 g / 10 min. The upper limit of the MFR, which can be arbitrarily combined with the above lower limit, 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 measured in accordance with Table 1 of JIS-K7210 "Plastics - Test methods for melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics," at a test temperature of 230°C and a test load of 2.16 kg.

[0018] When polyethylene is used for the fibers, it may be either polyethylene synthesized using a general Ziegler-Natta catalyst or polyethylene synthesized using a single-site active 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 / cm. ３ 0.97g / cm or more ３ or less, more preferably 0.925 g / cm ３ 0.96g / cm or more ３ The polyethylene may be used alone or in combination of two or more. From the viewpoint of fiber adhesiveness, it is preferable to use high-density polyethylene with linear polyethylene added in an amount of 0.5 wt % to 25 wt %.

[0019] From the viewpoint of spinnability in production, the lower limit of the melt index (MI) of the 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 arbitrarily 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 measured in accordance with Table 1 of JIS-K7210 "Plastics - Test methods for melt mass-flow rate (MFR) and melt volume-flow rate (MVR) of thermoplastics," at a test temperature of 190°C and a test load of 2.16 kg.

[0020] When a polyester resin is used, the solution viscosity of the resin η ｓｐ / c(η ｓｐ The lower limit of η (where η is the specific viscosity and c is the unit concentration of the resin) is preferably 0.2 or more, more preferably 0.6 or more. ｓｐ The upper limit of / c is preferably 0.9 or less, and more preferably 0.8 or less.

[0021] The nonwoven fabric has a length / width ratio (longitudinal / lateral) of the mean coefficient of friction variation (MMD) measured by the KES method of 0.5 or more, preferably 0.55 or more, and more preferably 0.60 or more. "Longitudinal" refers to the flow direction (MD) in the production of the nonwoven fabric, and "lateral" refers to the width direction (CD) perpendicular to the length direction. If the length / lateral ratio of the mean coefficient of friction is 0.5 or more, the dropped liquid is well dispersed on the surface layer of the nonwoven fabric, resulting in a large amount of liquid remaining after the liquid has passed through. Therefore, the nonwoven fabric is suitable for use as a substrate for SAP sheets. The upper limit of the length / lateral ratio of the variation (MMD) is preferably less than 1.00, more preferably less than 0.9.

[0022] From the viewpoint of reducing irritation to the skin, the absolute value of the average coefficient of friction measured by the KES method is preferably 0.0010 or more and 0.0100 or less, 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 machine direction (MD direction), and is 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 in the cross direction (CD direction).

[0023] The nonwoven fabric has a Martindale fluff rating of Grade 4 or less, preferably Grade 3 or less. More specifically, when the nonwoven fabric is subjected to a Martindale friction test using the same nonwoven fabric as the friction element at a load of 9 kPa and 16 friction cycles, one or more of surface roughness, pilling, holes, and tears occur, preferably one or more of pilling, holes, and tears. When the Martindale fluff rating is Grade 4 or less, the adhesion between fibers is not too strong, making it easier to support SAP inside the nonwoven fabric. The fluff rating is preferably greater than Grade 1.5. More specifically, it is preferable that the nonwoven fabric does not exhibit holes or tears in the friction test. When the fluff rating is greater than Grade 1.5, the adhesion between fibers is sufficient, increasing the strength of the nonwoven fabric and making it less likely to break during the diaper manufacturing process.

[0024] The average fiber diameter of the fibers of the nonwoven fabric 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 texture of the nonwoven fabric used in sanitary materials, the average fiber diameter is preferably 38.0 μm or less.

[0025] The basis weight of the nonwoven fabric is preferably 5 g / m ２ 80g / m or more ２ Less than 8 g / m, more preferably ２ 40g / m or more ２ More preferably, 10 g / m or less ２ 30g / m or more ２ The basis weight is 5 g / m or less. ２ If the basis weight is 80 g / m or more, the nonwoven fabric has a strength suitable for use in sanitary materials. ２ If the thickness is below this, the texture is sufficiently satisfactory for a nonwoven fabric to be used in sanitary materials, and the appearance is not likely to give a thick impression.

[0026] 1.25 g / cm of nonwoven fabric ２ 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.２ If the thickness under load is 140 μm or more, the texture and rewet performance of the nonwoven fabric are excellent. If the thickness is 3000 μm or less, the texture is sufficient for a nonwoven fabric used in sanitary materials, and the appearance is not bulky.

[0027] The nonwoven fabric may contain a water-permeable agent. The water-permeable agent to be used is not particularly limited, but taking into consideration safety for the human body and safety during processing, examples include nonionic surfactants to which ethylene oxide is added, such as higher alcohols, higher fatty acids, and alkylphenols, anionic surfactants such as alkyl phosphate salts and alkyl sulfate salts, and surfactants composed of these alone or as mixtures thereof. Preferred examples of the water-permeable agent include polyglycerin fatty acid esters, sorbitan fatty acid esters, polyether-polyester block copolymers, polyethylene ether-modified silicones, polyether-modified silicones, ethylene oxide-added polyhydric alcohols, and polyamide compounds.

[0028] The amount of the water-permeable agent is usually preferably 0.10 wt% to 2.00 wt%, more preferably 0.15 wt% to 1.50 wt%, based on the nonwoven fabric. If it is 0.10 wt% or more, sufficient water permeability is obtained, while if it is 1.50 wt% or less, it is unlikely to cause skin rash or eczema.

[0029] <<Method for producing nonwoven fabric for sanitary materials>> From the viewpoints of strength and productivity, the nonwoven fabric is preferably produced by the spunbond method. Details of the production method by the spunbond method are described below, but the nonwoven fabric of the present disclosure is not limited to nonwoven fabrics produced by the spunbond method.

[0030] A thermoplastic resin is melt-extruded from an extruder and discharged from a spinneret having a large number of spinning holes. When a nonwoven fabric containing conjugated long fibers combined with two or more thermoplastic resins is to be produced, for example, different thermoplastic resins are melt-extruded from two or more different extruders, and the two or more thermoplastic resins in a combined state are discharged as threads from a spinneret having a large number of spinning holes.

[0031] Next, the discharged yarn is cooled by blowing cold air controlled to a temperature of 3°C or higher and 28°C or lower, and is pulled by a pulling device. The yarn discharged from the pulling device is piled up on a transport conveyor to form a web, which is then transported. Another web may be layered on top of the web being transported. In the case of a laminated nonwoven fabric, each layer may be formed from webs of different fiber diameters, or webs made from special fiber forms such as modified cross-section yarns, crimped fibers, or hollow fibers may be layered.

[0032] The webs produced as described above are integrated by bonding to form a nonwoven fabric. The webs can be bonded using an adhesive, low-melting-point fibers or composite fibers, a hot-melt binder sprayed during web formation to melt and bond the web, or entangled fibers by needle punching or water jets, and the like, without any particular limitation.

[0033] From the viewpoint of easily maintaining the characteristics of the surface structure of the nonwoven fabric, particularly in the case of conjugated long fibers combined with two or more thermoplastic resins, a method of heating to a temperature at or above which the intersections of the fibers can melt and bond is preferred. Various heating methods can be used, including hot air circulation, hot air penetration, infrared heater, blowing hot air onto both sides of the nonwoven fabric, and introducing the nonwoven fabric into heated gas. Heating with hot air is preferred, and hot air penetration is particularly preferred, from the viewpoint of obtaining more fiber bonding points at the intersections of the fibers, resulting in higher breaking strength of the nonwoven fabric.

[0034] Conventionally, from the viewpoints of equipment maintenance and high-speed production, the bonding conditions for fibers have been such that a short heat treatment time is preferable, and the temperature and air velocity during bonding are set high. However, in the production of the nonwoven fabric of the present embodiment, bonding at a low temperature and air velocity is preferable from the viewpoint of increasing the amount of SAP supported in the SAP sheet substrate. Bonding at a low temperature and air velocity weakens the strength of the resulting nonwoven fabric, which may cause the nonwoven fabric to break during the manufacturing process of the sanitary material, so a long heat treatment time is necessary. To achieve a strength sufficient for use in the manufacturing process of the 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. A heat treatment time of 10 seconds or less prevents the fibers from being too strongly bonded to each other, resulting in a good texture.

[0035] The hot air velocity is preferably 0.1 m / s to 3.0 m / s, more preferably 0.5 m / s to 3.0 m / s, and even more preferably 1.0 m / s to 3.0 m / s. If the velocity is 0.5 m / s or higher, heat is transmitted thoroughly to the interior of the nonwoven fabric, resulting in sufficient adhesion of the fibers. If the velocity is 3.0 m / s or lower, collapse of the nonwoven fabric due to the velocity of the air can be suppressed, and the amount of SAP held by the substrate for an SAP sheet can be increased.

[0036] Bonding may be performed by embossing as long as it does not adversely affect the surface structure of the nonwoven fabric. From the viewpoint of productivity, embossing is preferably performed by passing the web through a pair of rolls consisting of a metal embossing roll and a metal flat roll. From the viewpoint of maintaining the shape of the web and the strength of the final nonwoven fabric, the embossed area ratio, i.e., the ratio of the area of ​​the embossed portion (bonded portion) to the area of ​​the entire nonwoven fabric, is preferably 5% to 30%, more preferably 5% to 20%, and even more preferably 6% to 15%. The deeper the embossing depth, the easier it is to maintain the thickness of the nonwoven fabric, and it is preferably 0.5 mm to 2.0 mm, more preferably 0.7 mm to 1.5 mm. The embossed shape is not particularly limited, but is preferably a circle, an ellipse, a diamond, a rectangle, or a combination thereof.

[0037] The water-permeable agent can be applied by conventional methods such as coating (e.g., using a gravure coater or a kiss coater) or spraying, and pretreatment such as corona discharge treatment or atmospheric pressure plasma discharge treatment may be performed as necessary. As a drying method after application, known methods utilizing convective heat transfer, conductive heat transfer, radiative heat transfer, etc. can be used, such as drying with hot air or infrared rays, or drying by thermal contact.

[0038] The water-permeable agent may be diluted with a solvent such as water and applied as an aqueous solution. To avoid insufficient drying during the drying process due to increased equipment speed, it is preferable to apply a small amount of the aqueous water-permeable agent solution. In any of the above-mentioned application methods, the amount (wt%) applied to the nonwoven fabric 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. An application amount of 1.0 wt% or more facilitates uniform application, while an application amount of 65 wt% or less reduces the drying capacity required in the subsequent drying process, thereby reducing equipment costs and preventing insufficient drying.

[0039] When applying the water-permeable agent using a gravure coater, the gravure roll pattern may be, for example, a lattice or pyramid type, but a diagonal type is preferred, as the water-permeable agent is less likely to remain at the bottom of the gravure cell. The cell volume is preferably 5 cm ３ / m ２ 40cm or more ３ / m ２ The cell volume is 5 cm or less. ３ / m ２ If it is more than 40cm, it will be easy to apply evenly. ３ / m ２ If the thickness is less than 100 μm, it is easy to suppress insufficient drying in the drying step and uneven adhesion of the water-permeable agent due to migration. The depth of the gravure cells is preferably 10 μm or more and 80 μm or less, and the cell spacing is preferably 80 mesh or more and 250 mesh or less.

[0040] For ease of equipment management, application by a kiss coater method using a stainless steel applicator roll is also preferred. The aqueous solution of the water-permeable agent is continuously supplied to a bath, and the water-permeable agent can be applied by bringing a rotating roller in the bath into contact with the nonwoven fabric. The amount of water-permeable agent applied can be easily adjusted by setting the number of revolutions per minute of the kiss roll.

[0041] Spraying is also preferred for applying the water-permeable agent, as it allows for efficient application and is compatible with faster equipment speeds, and the thickness of the nonwoven fabric can be easily maintained. Examples of spraying methods include an air spray method, in which the water-permeable agent aqueous solution is sprayed in the form of a fine mist using compressed air, and a rotor dampening method, in which the water-permeable agent aqueous solution is sprayed in the form of a mist using the centrifugal force of rotor rotation. When applying the water-permeable agent aqueous solution by spraying, the spraying direction may be either on one side of the nonwoven fabric or on both sides.

[0042] A common drying method can be used for drying the water-permeable agent solution after application, and is not particularly limited, and known methods utilizing convective heat transfer, conductive heat transfer, radiative heat transfer, etc. For example, various drying methods can be used, such as a hot air circulation type, a hot air penetration type, an infrared heater type, a method of blowing hot air onto both sides of the nonwoven fabric, and a method of introducing the nonwoven fabric into heated gas.

[0043] In order to adjust the aspect ratio (longitudinal / lateral) of the average coefficient of friction variation (MMD) measured by the KES method to 0.5 or more, in the case of a spunbond method, the width in the longitudinal direction (MD direction) when the pulled yarn lands on the conveyor (the fall width from the outlet of the pulling device to the conveyor) is preferably 30 mm or more. The reason for this is not limited by theory, but it is thought that a fall width of 30 mm or more prevents crimped fibers from becoming entangled and allows the fibers to be properly aligned. From the viewpoint of preventing a decrease in the SAP loading amount due to a decrease in the thickness of the nonwoven fabric, the fall width is preferably 500 mm or less, more preferably 300 mm or less, and even more preferably 200 mm or less. The machine direction (the direction in which the fibers are oriented) in the production of the nonwoven fabric is defined as the machine direction, and the direction perpendicular to the machine direction in the plane of the nonwoven fabric is defined as the transverse direction. Furthermore, in order to set the fall width to 30 mm or more and 500 mm or less, it is preferable to adjust the distance (height) between the conveyor and the diffuser.

[0044] In order to adjust the Martindale fluff grade to Grade 4 or less, in the case of a bonding method using hot air, 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 made of composite fibers containing polyethylene and polypropylene, the temperature at which the polyethylene is melted and bonded is preferably 160°C or less, more preferably 150°C or less, even more preferably 140°C or less, and most preferably 130°C or less. If the temperature is 160°C or less, it is easy to achieve a Martindale fluff grade of Grade 4 or less and to provide sufficient water retention. As a lower limit that can be arbitrarily combined with the above upper limit, from the viewpoint of sufficiently bonding the fibers together, a bonding temperature of 100°C or more is preferred. In order to adjust the Martindale fluff grade to Grade 4 or less, the pulling speed is adjusted so that the number of crimps is preferably more than 3 / 2.5 cm, more preferably 5 / 2.5 cm or more. The reason for this is thought to be that, without being limited by theory, when the number of crimps exceeds 3 / 2.5 cm, the number of fiber loops present on the surface of the nonwoven fabric increases, resulting in increased fuzzing.

[0045] <<SAP Sheet Substrate, SAP Sheet, and Sanitary Material>> The SAP sheet substrate of the present disclosure comprises the nonwoven fabric for sanitary materials of the present disclosure, and may be optionally combined with other nonwoven fabrics for sanitary materials. The SAP sheet substrate is preferably made of the nonwoven fabric for sanitary materials of the present disclosure.

[0046] The SAP sheet of the present disclosure includes the SAP sheet substrate of the present disclosure and an SAP (superabsorbent polymer). SAP generally refers to a polymer compound capable of absorbing and retaining water in amounts ranging from several hundred to approximately one thousand times its own weight. Examples of SAP include, but are not limited to, polyvinyl alcohol, polyethylene glycol, polyacrylonitrile, and polyacrylic acid-based polymer compounds. From the viewpoint of high water absorption, the SAP is preferably a polyacrylic acid-based polymer compound, more preferably sodium polyacrylate. The SAP sheet preferably has the SAP supported on the SAP sheet substrate.

[0047] The sanitary material of the present disclosure includes the SAP sheet of the present disclosure. Examples of the sanitary material include diapers, masks, body warmers, tape bases, patch bases, first aid bandage bases, packaging materials, wipe products, medical gowns, bandages, clothing, and skin care sheets. Because the nonwoven fabric for sanitary material of the present disclosure has excellent water retention, SAP support, and liquid permeability, the sanitary material is preferably a diaper.

[0048] Examples and comparative examples of the present disclosure will be described in detail below, but the present disclosure is not limited to the following examples. 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 production of nonwoven fabric is called the MD direction (machine direction), and the width direction perpendicular to that direction is called the CD direction (cross direction).

[0049] <Average fiber diameter (μm)> One meter of a nonwoven fabric was divided into five equal parts in the CD direction, and a 1 cm square sample was taken from the center of each of the five equal parts. The fiber diameter of each sample was measured at 20 points using a microscope VHX-700F manufactured by Keyence Corporation, and the average value was calculated.

[0050] <Weight (g / m ２) In accordance with JIS-L1906:2000, five samples of 20 cm in MD x 5 cm in CD were taken so that they were evenly spaced in the CD direction of the nonwoven fabric, and the mass was measured. The average value was converted into the weight per unit area to give the basis weight (g / m ２ ) was calculated.

[0051] <Aspect Ratio of Average Coefficient of Friction Variation (MMD) by KES Method> 1 m of nonwoven fabric in the CD direction was divided into 5 equal parts, and 5 samples of 200 cm x 200 cm were collected. Each sample was mounted on the measurement platform of a Kato Tech Co., Ltd. automated surface tester (KES-FB4A). A standard friction probe (10 mm square metal wire friction probe) was moved 30 mm on the sample at a measurement load of 50 gf, a tension of 400 gf / 20 cm, and a movement speed of 1 mm / min, and the average coefficient of friction variation was calculated from the data at a distance of 20 mm from the center. Measurements were performed in the longitudinal direction (MD direction) and transverse direction (CD direction) of the 5 samples, and the average values ​​were used as the average coefficient of friction variation in the longitudinal direction and the average coefficient of friction variation in the transverse direction. The average coefficient of friction variation in the longitudinal direction was divided by the average coefficient of friction variation in the transverse direction to obtain the aspect ratio of the average coefficient of friction variation.

[0052] <Fluffing Grade (Grade)> Using a Groz-Beckert Martindale Abrasion and Pilling Tester, the sample was rubbed at a load of 9 kPa and 16 rubs in accordance with the Martindale method (WSP20.5(05)) (except that the nonwoven fabric sample was placed on a 155 mm diameter polyurethane foam (model number HEA786-255, purchased from Groz-Beckert Japan) instead of on felt, and the nonwoven fabric was attached to the friction element by sandwiching a 38 mm diameter polyurethane foam (same as above) between the friction element and the nonwoven fabric so that the same nonwoven fabric as the sample served as the friction surface). The fluffing state of the sample after rubbing was observed, and the grade was determined visually. Measurements were made on both sides of the sample with N=5, and the average value was taken, and the grade of the side with more fluff (lower fluff grade) was adopted. It should be noted that the grades and evaluation criteria set forth in this disclosure are written in the reverse order of the grades set forth in the specification of Japanese Patent Application No. 2021-080917, which is the basic application of the priority claim of this application, but there are no changes other than the order. The grades and evaluation criteria of this disclosure and the basic application correspond as follows: Grade 5 (Grade 1 in the basic application): No change. Grade 4 (Grade 2 in the basic application): The surface is rough. Grade 3 (Grade 3 in the basic application): Pilling is present (less than 5 pieces). Grade 2 (Grade 4 in the basic application): Pilling is observed over the entire surface (5 pieces or more). Grade 1 (Grade 5 in the basic application): Holes or tears are present.

[0053] <Amount of Water-Permeable Agent (wt%)> The weight W1 (mg) of a nonwoven fabric sample with a water-permeable agent attached, which had been conditioned for 24 hours at a temperature and humidity of 25°C and 40% RH, and the weight W2 (mg) of an extract extracted from this nonwoven fabric sample using methanol using a rapid extraction device (manufactured by Intec Co., Ltd.), were measured, and the amount of water-permeable agent C (wt%) was calculated using the following formula: C (wt%) = [W2 / W1] x 100. Nonwoven fabric samples were collected from five locations at 30 cm intervals in the MD direction and five locations equally spaced across the width of the nonwoven fabric in the CD direction, with cutouts ranging from 5 cm to 10 cm in width and lengths such that the nonwoven fabric sample weighed approximately 2 g. A total of 10 samples were collected. Measurements were performed on these 10 samples, and the average value was used to determine the amount of water-permeable agent (wt%).

[0054] <Number of crimps (per 2.5 cm)> The nonwoven fabric was divided into five equal parts in the CD direction, and a 5 cm square sample was taken from the center of each of the five equal parts. Five fibers were carefully removed from each sample using tweezers and scissors while observing the sample under a stereomicroscope, taking care not to deform the thread structure. The removed fibers were left in a state where no load was applied, and the number of crimps per 2.5 cm length was measured. The number of crimps (per 2.5 cm) was calculated from the average value.

[0055] <Water Retention (g)> A nonwoven fabric was sampled and weighed in an area of ​​150 mm in the MD direction and 150 mm in the CD direction, and the sample was fixed to the mouth of a 300 mL beaker with a rubber band. 100 mL of physiological saline was dripped onto the center of the sample from 25 mm above at a rate of 2 mL / s. After the dripping, the sample was held for 5 minutes, after which the sample was removed and the weight was measured. The difference from the weight of the sample measured previously was taken as the water retention (g). Note that a water retention of 0.5 g or more indicates good water absorbency and is unlikely to leak when used as a diaper.

[0056] <SAP Loading Amount (%)> A sample of nonwoven fabric was taken in an area of ​​150 mm in the machine direction and 150 mm in the cross direction, and its weight was measured (this weight was designated as weight A (mg)). The nonwoven fabric sample was placed between a tray and a sieve (inner diameter 75 mm x inner height 20 mm, mesh size 2.36 mm), and 10 g of SAP was dropped from the top of the sieve. The tray, nonwoven fabric sample, and the sieve containing the SAP were then placed in a sieve shaker (MICRO VIBRO SIFTER MODEL M-2), the volume was adjusted to 1, and the sieve was shaken for 1 minute. After shaking, the nonwoven fabric was removed by holding one side of the nonwoven fabric so that the SAP on the surface of the nonwoven fabric would fall, with the nonwoven fabric held vertically, and immediately weighed on a balance (this weight was designated as weight B (mg)). The SAP loading amount (%) was calculated using the following formula: SAP supported amount (%) = [(weight B (mg) - weight A (mg)) / weight A (mg)] x 100 The SAP used had the following particle size distribution: More than 0 μm and 200 μm or less...1% More than 200 μm and 400 μm or less...5% More than 400 μm and 600 μm or less...24% More than 600 μm and 800 μm or less...35% More than 800 μm and 1000 μm or less...25% More than 1000 μm and 1200 μm or less...10%

[0057] <Repeated water flow rate> Two pieces of nonwoven fabric were sampled, each measuring 150 mm in MD and 150 mm in CD. ２ Hot melt was evenly applied to the entire surface of the nonwoven fabric using a spray-type hot melt gun, and then 5 g of SAP was sprinkled evenly. After the SAP was sprinkled, another sheet of nonwoven fabric was placed on top to create a simple SAP sheet with a three-layer structure of nonwoven fabric / SAP / nonwoven fabric. A 125 mm square sample of the resulting simple SAP sheet was taken and placed on a larger plastic plate. The detection plate of a Lenzing Instruments LISTER, used in the Strike-Through method according to the EDANA standard, was then placed on top, and 20 mL of saline was dripped from 30 mm above. This was the first drip. The same procedure was repeated every 30 minutes, and the value displayed by the LISTER after the third drip was recorded as the third water flow rate.

[0058] <MD tensile strength (N / 50 mm)> In accordance with JIS-L1913:2010, five samples each measuring 30 cm in MD × 5 cm in CD were taken from the nonwoven fabric so that the sample taking positions were uniform in the CD direction, and the tensile strength was measured. The average value of the measurement results for the five samples was taken as the MD tensile strength.

[0059] Examples and Comparative Examples Example 1 A polypropylene (PP) resin having an MFR of 55 g / 10 min (measured in accordance with JIS-K7210 at 230°C and a load of 2.16 kg) was used as the first component, and a high-density polyethylene (HDPE) resin having an MI of 26 g / 10 min (measured in accordance with JIS-K7210 at 190°C and a load of 2.16 kg) was used as the second component. Using a side-by-side spinneret, filaments were extruded at a total throughput rate of 0.8 g / min / hole at a spinning temperature of 220°C so that the ratio of the first component to the second component was PP / PE = 3 / 2. The extruded filaments were stretched in the traction zone using the suction force of the conveyor, and then passed through a diffuser and deposited on the conveyor surface to form a web. The distance (height) between the conveyor and the diffuser was adjusted so that the fall width of the fibers in the MD direction was 50 mm. The obtained web was exposed to hot air at 125° C. and a wind speed of 1.2 m / s for 3 seconds to obtain a nonwoven fabric.

[0060] Next, a 5 wt % aqueous solution of a water permeable agent composed of polyoxyethylene fatty acid glyceryl and polyether-modified silicone (this water permeable agent is designated as A in the table) was adjusted to a liquid temperature of 20°C and applied to the obtained nonwoven fabric while adjusting the embrace angle and rotation speed of the stainless steel applicator roll so that the coating amount was 10 wt %. The fabric was then dried through a cylinder dryer at 125°C to obtain a nonwoven fabric.

[0061] Example 2 A nonwoven fabric was obtained in the same manner as in Example 1, except that the distance (height) between the conveyor and the diffuser was adjusted so that the falling width of the fibers in the MD direction was 60 mm.

[0062] Example 3 A nonwoven fabric was obtained in the same manner as in Example 1, except that the distance (height) between the conveyor and the diffuser was adjusted so that the falling width of the fibers in the MD direction was 70 mm.

[0063] Example 4 A nonwoven fabric was obtained in the same manner as in Example 1, except that the distance (height) between the conveyor and the diffuser was adjusted so that the falling width of the fibers in the MD direction was 100 mm.

[0064] Example 5 A nonwoven fabric was obtained in the same manner as in Example 1, except that the falling width of the fibers in the MD direction was 80 mm and the bonding temperature was 110°C.

[0065] Example 6 A nonwoven fabric was obtained in the same manner as in Example 5, except that the bonding temperature was 120°C.

[0066] Example 7 A nonwoven fabric was obtained in the same manner as in Example 5, except that the bonding temperature was 125°C.

[0067] Example 8 A nonwoven fabric was obtained in the same manner as in Example 5, except that the bonding temperature was 130°C.

[0068] Example 9 A nonwoven fabric was obtained in the same manner as in Example 5, except that the bonding temperature was 140°C.

[0069] [Example 10] A nonwoven fabric was obtained in the same manner as in Example 7, except that in the coating of the water permeable agent, a 5 wt% aqueous solution of the water permeable agent was applied using a rotor dampening method, the liquid temperature was adjusted to 20°C, and the coating amount was 10 wt%, and the nonwoven fabric was passed through a cylinder dryer at 120°C, dried, and wound up.

[0070] Example 11 A nonwoven fabric was obtained in the same manner as in Example 7, except that the water permeable agent was a mixture of polyoxyalkylene alkyl ether and polyether-modified silicone (this water permeable agent is designated as B in the table).

[0071] [Example 12] A nonwoven fabric was obtained in the same manner as in Example 7, except that the water permeable agent was a mixture of polyoxyethylene fatty acid glyceryl, alkyl phosphate ester, and lauryldiethanolamine (this water permeable agent is represented by C in the table).

[0072] Example 13 A nonwoven fabric was obtained in the same manner as in Example 7, except that the pulling speed was adjusted so that the number of crimps was 23 crimps / 2.5 cm.

[0073] Example 14 A nonwoven fabric was obtained in the same manner as in Example 7, except that the pulling speed was adjusted so that the number of crimps was 28 crimps / 2.5 cm.

[0074] [Example 15] Solution viscosity η ｓｐ A polyethylene terephthalate (PET) resin with a ρ / c of ​​0.75 was used as the first component, and a high-density polyethylene (PE) resin similar to that in Example 1 was used as the second component. Using a side-by-side spinneret, the total output rate was 0.8 g / min / hole, and filaments were extruded at a spinning temperature of 295 ° C. so that the ratio of the first component to the second component was PPPET / PE = 1 / 1. The extruded filaments were stretched in the traction zone using the suction force of the conveyor, then passed through a diffuser and deposited on the conveyor surface to form a web. At this time, the distance (height) between the conveyor and the diffuser was adjusted so that the fall width of the fibers in the MD direction was 80 mm. The obtained web was exposed to hot air for 3 seconds at 135 ° C. and a wind speed of 1.2 m / s to obtain a nonwoven fabric.

[0075] Next, a 5 wt % aqueous solution of a water-permeable agent composed of a sorbitan fatty acid ester and dioctyl sodium sulfosuccinate (referred to as D in the table) was adjusted to a liquid temperature of 20°C, and the resulting nonwoven fabric was coated with a kiss coater while adjusting the embrace angle and rotation speed of the stainless steel applicator roll so that the coating amount was 10 wt %. The fabric was then dried through a cylinder dryer at 125°C to obtain a nonwoven fabric.

[0076] [Example 16] Solution viscosity η ｓｐ A web was formed by carding using sheath-core composite fibers (fiber diameter 2.5 dtex) with a fiber length of 38 mm, the fiber length being polyethylene terephthalate (PET) with a fiber diameter / c of ​​0.75 as the core component and the same high-density polyethylene (PE) as in Example 1 as the sheath component. Hot air was blown onto the web at 135°C and an air speed of 1.2 m / s for 5 seconds to thermally fuse the fibers together, yielding a nonwoven fabric, and the draw ratio during take-up was adjusted so that the nonwoven fabric would be stretched in the MD, yielding a nonwoven fabric.

[0077] Comparative Example 1 A nonwoven fabric was obtained in the same manner as in Example 7, except that the pulling speed was adjusted so that the number of crimps was 32 per 2.5 cm.

[0078] Comparative Example 2 A nonwoven fabric was obtained in the same manner as in Example 7, except that the distance (height) between the conveyor and the diffuser was adjusted so that the falling width of the fibers in the MD direction was 40 mm.

[0079] Comparative Example 3 A nonwoven fabric was obtained in the same manner as in Example 7, except that the pulling speed was adjusted so that the number of crimps was 3 per 2.5 cm and the bonding temperature was set to 145°C.

[0080]

[0081]

[0082] The nonwoven fabric for hygiene materials of the present disclosure has excellent water retention, SAP support, and liquid permeability, making it suitable for use as a substrate for SAP sheets. The nonwoven fabric for hygiene materials of the present disclosure can also be used as a component of diapers, such as a top sheet or a second sheet. Furthermore, the nonwoven fabric for hygiene materials of the present disclosure can also be used for, for example, masks, body warmers, tape bases, medicinal patch bases, first aid bandage bases, packaging materials, wipe products, medical gowns, bandages, clothing, skin care sheets, and the like.

Claims

1. A nonwoven fabric for sanitary materials, having a length / width ratio (length / width) of the average coefficient of friction fluctuation (MMD) measured by the KES method of 0.5 or more, and a fluff grade of 4 or less measured by the Martindale method.

2. The nonwoven fabric for sanitary materials according to claim 1, which has a fluff grade of 3 or less according to the Martindale method.

3. A nonwoven fabric for sanitary materials having an aspect ratio (length / width) of the variation value of the average coefficient of friction (MMD) according to the KES method of 0.5 or more, which, when subjected to a friction test according to the Martindale method using the same nonwoven fabric as the nonwoven fabric for sanitary materials as a friction element at a load of 9 kPa and 16 friction cycles, exhibits one or more of the following: surface roughness, pilling, holes, and tears.

4. The nonwoven fabric for sanitary materials according to claim 3, which, when a friction test is performed by the Martindale method using the same nonwoven fabric as the nonwoven fabric for sanitary materials as a friction element, with a load of 9 kPa and 16 friction cycles, exhibits one or more of pilling, holes, and tears.

5. Weight per unit area is 5g / m ２ 80g / m or more ２ The sanitary nonwoven fabric according to any one of claims 1 to 4, wherein:

6. The nonwoven fabric for sanitary materials according to any one of claims 1 to 4, which is composed of fibers having a fiber length of 50 mm or more.

7. The nonwoven fabric for sanitary materials according to any one of claims 1 to 4, which is a spunbonded nonwoven fabric.

8. The nonwoven fabric for sanitary materials according to any one of claims 1 to 4, which contains a water permeable agent.

9. The nonwoven fabric for sanitary materials according to any one of claims 1 to 4, comprising fibers with a crimp number of 3 or more / 2.5 cm to 45 or less / 2.5 cm.

10. The nonwoven fabric for sanitary materials according to any one of claims 1 to 4, which contains a polyolefin resin.

11. A substrate for SAP sheets, comprising the nonwoven fabric for sanitary materials according to any one of claims 1 to 4.

12. The substrate for SAP sheets according to claim 11, wherein the nonwoven fabric for sanitary materials has a fluff grade of 3 or less according to the Martindale method, is a spunbond nonwoven fabric, and contains a polyolefin resin.

13. An SAP sheet comprising the substrate for an SAP sheet according to claim 11 and an SAP.

14. A sanitary material comprising the SAP sheet according to claim 13.