Laminated nonwoven fabrics and sanitary materials

Abstract

The present invention aims to provide a laminated nonwoven fabric having sufficient quick-drying properties and an excellent absorption rate to maintain comfort within a member using a nonwoven fabric for sanitary materials. The present invention is a laminated nonwoven fabric formed by laminating nonwoven layers containing thermoplastic resin fibers, wherein in the nonwoven layer (A) having the smallest average short fiber diameter among the nonwoven layers, the inter-fiber pore size Ra (㎛) calculated by the following formula (1) is 200㎛ or less. Ra=(100×Ta×da) / (Wa×Da)-Da… Equation (1) Here, Ta: Thickness (㎛) of nonwoven layer (A) da: Fineness (dtex) of the thermoplastic resin fibers constituting the nonwoven layer (A) Wa: Weight per unit area of ​​nonwoven layer (A) (g / m²) Da: Average short fiber diameter (μm) of the thermoplastic resin fibers constituting the nonwoven layer (A).

Description

Technology Field

[0001] The present invention relates particularly to a laminated nonwoven fabric suitable for use as a sanitary material and a sanitary material using the same. Background Technology

[0002] In general, for hygiene materials such as paper diapers, sanitary pads, and masks, the key to comfort is the ability to quickly remove moisture, such as urine or sweat, and keep the surface dry.

[0003] For this reason, for components that come into direct contact with the skin, it is required to have both "absorbency," which rapidly absorbs moisture, and "quick-drying property," which transfers the absorbed moisture from the outermost surface layer to keep the surface dry.

[0004] Conventionally, various nonwoven fabrics treated with hydrophilization have been widely used for this surface material. While these can guide moisture from the outermost surface layer to the inner nonwoven fabric or absorbent layer, moisture tends to remain on the outermost surface layer, resulting in poor "quick-drying properties."

[0005] Regarding this problem, Patent Document 1 proposes a nonwoven fabric in which a fiber layer containing fine fibers (on the skin side) and a fiber layer containing coarse fibers are laminated, with some intermingling at the interface. Additionally, Patent Document 2 proposes a sheet in which sheets with different average fiber non-occupancy pores are laminated according to the difference in the mixing ratio and fiber diameter of a plurality of fibers, such that the average fiber non-occupancy pore of the first layer in contact with the skin is larger than that of layers other than the first layer. Prior art literature

[0006] Japanese Patent Publication No. Hei 7-042057 Japanese Patent Publication No. Hei 7-178133 The problem to be solved

[0007] However, with the technology of Patent Document 1, it was difficult to obtain both "quick drying" and "absorbency."

[0008] Meanwhile, the technology of Patent Document 2 states that by creating a difference in the volume of pores other than fibers between layers, it is possible to guide moisture absorbed in the first layer to the second layer (the layer opposite the skin surface) due to a difference in capillary effect. However, the "quick-drying ability" of the technology of Patent Document 2 was insufficient.

[0009] Therefore, the objective of the present invention is to provide a laminated nonwoven fabric having sufficient quick-drying properties and excellent absorbency to maintain comfort within a member using a nonwoven fabric for sanitary materials. means of solving the problem

[0010] The inventors have discovered that in the technology of Patent Document 1, since the fiber layer containing fine fibers on the skin side has a denser structure compared to other layers, moisture tends to remain in the fiber layer on the skin side, making it difficult to obtain "quick drying properties," and furthermore, because the dense fiber layer on the skin side reduces permeability, moisture cannot be absorbed quickly, making it difficult to obtain "absorbency."

[0011] In addition, the inventors have found that the average fiber non-occupied pore disclosed in Patent Document 2 represents the total volume of space occupied by non-fibers, and therefore is not an indicator of the size of the inter-fiber pores important for capillary force, and that a difference between layers does not result in a difference in capillary force. In particular, in Patent Document 2, since the size of the inter-fiber pores in layers other than the skin surface is large, capillary force cannot be sufficiently drawn out, and thus the transfer of moisture from the skin surface has a limited effect, and the "quick drying" is insufficient.

[0012] And as a result of repeated careful consideration to achieve the above objective, the inventors have obtained the finding that, in a laminated nonwoven fabric, by controlling the inter-fiber gap size, considering the fiber diameter, to a specific range in addition to the weight and thickness per unit area in a specific nonwoven layer, a laminated nonwoven fabric having sufficient absorption and quick-drying properties for use as a nonwoven fabric for hygiene materials can be obtained.

[0013] The present invention has been completed based on these findings, and according to the present invention, the following invention is provided.

[0014] The present invention is a laminated nonwoven fabric comprising layers of nonwoven fabrics including thermoplastic resin fibers, wherein in the nonwoven fabric layer (A) having the smallest average short fiber diameter among the nonwoven fabric layers, the inter-fiber gap size Ra (㎛) calculated by the following formula (1) is 200㎛ or less.

[0015] Ra=(100×Ta×da) / (Wa×Da)-Da… Equation (1)

[0016] Here,

[0017] Ta: Thickness (㎛) of nonwoven layer (A)

[0018] da: Fineness (dtex) of the thermoplastic resin fibers constituting the nonwoven layer (A)

[0019] Wa: Weight per unit area of ​​nonwoven layer (A) (g / m²)

[0020] Da: Average short fiber diameter (μm) of the thermoplastic resin fibers constituting the nonwoven layer (A).

[0021] In addition, the present invention is a sanitary material comprising at least a portion of the laminated nonwoven fabric of the present invention. Effects of the invention

[0022] According to the present invention, a laminated nonwoven fabric can be obtained that has sufficient fast-drying properties for use as a sanitary nonwoven fabric and also has an excellent absorption rate. Specific details for implementing the invention

[0023] The present invention will be described in detail below. However, the present invention is not limited to the scope described below, provided that it does not depart from the gist thereof.

[0024] [Thermoplastic resin fibers]

[0025] First, the laminated nonwoven fabric of the present invention is formed by laminating nonwoven fabric layers containing thermoplastic resin fibers.

[0026] The term "thermoplastic resin fiber" as used in the present invention refers to a fiber containing a thermoplastic resin. Such thermoplastic resin may be of one type or may contain a plurality of thermoplastic resins.

[0027] Examples of thermoplastic resins used in thermoplastic resin fibers in the present invention include:

[0028] Aromatic polyester polymers such as polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polyhexamethylene terephthalate, and copolymers thereof

[0029] Aliphatic polyester polymers such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, polyhydroxybutylate-polyhydroxyvalylate copolymer, polycaprolactone, and copolymers thereof,

[0030] Aliphatic polyamide-based polymers such as polyamide 6, polyamide 66, polyamide 610, polyamide 10, polyamide 12, polyamide 6-12, and copolymers thereof,

[0031] Polyolefin-based polymers such as polypropylene, polyethylene, polybutene, polymethylpentene, and copolymers thereof,

[0032] Water-insoluble ethylene-vinyl alcohol copolymer system polymer containing 70 mol% of ethylene units at 25 mol%,

[0033] Polystyrene-based, polydiene-based, chlorine-based, polyolefin-based, polyester-based, polyurethane-based, polyamide-based, and fluorine-based elastomer-based polymers, and can be selected and used from among these.

[0034] In addition, thermoplastic resins may contain various additives such as inorganic materials like titanium oxide, silica, and barium oxide, carbon black, coloring agents such as dyes or pigments, flame retardants, fluorescent whitening agents, antioxidants, or ultraviolet absorbers.

[0035] In addition, between the nonwoven layers, the thermoplastic resin constituting the thermoplastic resin fiber may be the same or different.

[0036] The thermoplastic resin fiber in the present invention may be a single-component fiber, or a composite fiber formed by combining two or more types of resins. When the thermoplastic resin fiber is a composite fiber, it is not particularly limited as long as it does not impair the effects of the present invention, and it may be appropriately selected from a core-sheath type, a sea-island type, a side-by-side type, an eccentric core-sheath type, etc. In addition, it may be a split-fiber type composite fiber in which part or all of the fiber is divided from a single fiber into multiple fibers.

[0037] The cross-sectional shape of the thermoplastic resin fiber of the present invention is not particularly limited as long as it does not impair the effects of the present invention, and may be a circular cross-section, as well as a irregular cross-section such as a triangular, flat, hexagonal, or hollow cross-section. When the laminated nonwoven fabric of the present invention is used as a sanitary material, a circular cross-section is preferred in that it offers high productivity and excellent flexibility.

[0038] [Lamination interface of laminated nonwoven fabric]

[0039] A lamination interface for specifying the nonwoven layer in the laminated nonwoven fabric of the present invention is described. The lamination interface in the laminated nonwoven fabric of the present invention is specified according to the following steps.

[0040] (Specific sequence of stacking interfaces)

[0041] Procedure 1: Take a 5 cm × 5 cm sample from the laminated nonwoven fabric. Avoid areas where the thickness is thin due to poor fabric uniformity.

[0042] Step 2: A three-dimensional image is taken of the sample obtained in Step 1 using a high-resolution three-dimensional X-ray microscope. The resolution of the measurement should be within a range where the diameter of the fibers of each nonwoven layer can be determined, but it is preferable to have a resolution of 1.0 μm / voxel or less. Here, if the laminated nonwoven fabric has been embossed, the image is taken so that the center point between the embossed points, that is, the center of the convex part left by the embossing process, is included within the imaging range of the X-ray CT image.

[0043] Step 3: From the 3D image taken in Step 2, an area of ​​0.5 mm × 0.5 mm is extracted as the area to be analyzed. Here, if the laminated nonwoven fabric has an embossing process, the area to be analyzed is extracted to include the center point between the embossing points.

[0044] Step 4: For the area of ​​the subject to analysis extracted in Step 3, slice (cross-sectional) images parallel to each other and perpendicular to the thickness direction of the laminated nonwoven fabric are produced at intervals of 1 voxel.

[0045] Step 5: Analyze the fiber diameters of all fibers included in each slice image obtained in Step 4, calculate the average value, and set it as the provisional average fiber diameter.

[0046] Step 6: A graph is obtained by plotting the position of each slice image produced in Step 4 in the thickness direction of the laminated nonwoven fabric on the x-axis (unit is μm) and the provisional average fiber diameter of each slice image obtained in Step 5 on the y-axis (unit is μm).

[0047] Step 7: In the graph obtained in Step 6, the rate of change Δy / Δx of the y-axis value with respect to the x-axis is calculated from continuous 15-voxel data using the least squares method, and the interval on the x-axis where its absolute value is 0.30 or greater is identified as the interface position of the lamination between nonwoven layers.

[0048] [Non-woven fabric layer (A)]

[0049] In the laminated nonwoven fabric of the present invention, the nonwoven layer (A) is defined as having the smallest average short fiber diameter among the nonwoven layers constituting the laminated nonwoven fabric.

[0050] The average staple fiber diameter of each nonwoven layer is calculated as follows.

[0051] (Measurement procedure for the average staple fiber diameter of the nonwoven layer)

[0052] Step 1: A cross-section in the thickness direction is photographed using a scanning electron microscope (SEM) at a magnification that converges the entire thickness direction of the laminated nonwoven fabric within the imaging range.

[0053] Step 2: Apply the position information of the laminated interface obtained by the “step for specifying the laminated interface” to the cross-sectional image obtained in Step 1. In Step 7 of the “step for specifying the laminated interface,” the section on the x-axis where the absolute value of Δy / Δx is 0.30 or greater is designated as the laminated interface section, and the section separated by the laminated interface section is designated as the analysis section for each nonwoven fabric layer.

[0054] Step 3: Using image analysis software for the analysis sections of specific nonwoven layers in Step 2, the area Af (㎛) formed by the cross-sectional contour of the staple fibers 2 ) is measured, and the diameter of the circle that has the same area as this area Af is calculated. This is measured for 20 short fibers randomly selected from the same analysis section, and the average is calculated, with the unit set to μm and rounded to the second decimal place to obtain the average short fiber diameter.

[0055] It is preferable that the average short fiber diameter Da of the thermoplastic resin fiber constituting the nonwoven layer (A) be 20.0 μm or less. By making Da 20.0 μm or less, and more preferably 15.0 μm or less, the inter-fiber pore size Ra of the nonwoven layer (A) described later can be effectively reduced, thereby obtaining suitable capillary force. In addition, it is preferable that Da be 2.0 μm or more. By making Da 2.0 μm or more, the inter-fiber pore size Ra of the nonwoven layer (A) can be suppressed from becoming extremely small, thereby suppressing the reduction in liquid permeability.

[0056] In the laminated nonwoven fabric of the present invention, in the nonwoven fabric layer (A), the interfiber gap size Ra calculated by the following formula (1) is 200 μm or less.

[0057] Ra=(100×Ta×da) / (Wa×Da)-Da… Equation (1)

[0058] Here,

[0059] Ta: Thickness (㎛) of nonwoven layer (A)

[0060] da: Fineness (dtex) of the thermoplastic resin fibers constituting the nonwoven layer (A)

[0061] Wa: Weight per unit area of ​​the nonwoven layer (A) (g / m²)

[0062] Da: Average short fiber diameter (μm) of the thermoplastic resin fibers constituting the nonwoven layer (A).

[0063] The thickness of each nonwoven fabric layer is determined as follows.

[0064] (Procedure for measuring the thickness of the non-woven layer)

[0065] Procedure 1: For each of the nonwoven layer to be measured for thickness and the other nonwoven layer laminated thereon, the average short fiber diameter obtained in the “Procedure for Measuring Average Short Fiber Diameter of Nonwoven Layer” is added and divided by 2 to calculate the average fiber diameter of the two layers. If another nonwoven layer is laminated on the other side of the nonwoven layer to be measured for thickness, the average short fiber diameter between it and the other nonwoven layer is added and divided by 2 to calculate the average fiber diameter of the two layers.

[0066] Step 2: In the section of the lamination interface between the nonwoven layer to be measured for thickness and another nonwoven layer laminated thereon, on the graph obtained in Step 6 of “Step 6 for determining the lamination interface,” the x-coordinate y is determined by taking the average value of the fiber diameters of the two layers calculated in Step 1.

[0067] Step 3: If another nonwoven layer is laminated on both sides of the nonwoven layer to be measured for thickness, the distance between x-coordinates is calculated by taking the average value of the fiber diameters of the two laminated layers in the section of the laminated interface between both sides, and this is taken as the thickness of the nonwoven layer to be measured. If another nonwoven layer is laminated on only one side of the nonwoven layer to be measured for thickness, the distance between the x-coordinate taking the average value of the fiber diameters of the two layers in the section of the laminated interface and the x-coordinate of the exposed surface on the other side of the nonwoven layer to be measured is calculated, and this is taken as the thickness of the nonwoven layer to be measured.

[0068] In addition, the thickness Tt of the laminated nonwoven fabric can be obtained by calculating the distance between the x-coordinates of the two surfaces of the laminated nonwoven fabric in Step 3 of the “Step for measuring the thickness of the nonwoven fabric layer”.

[0069] In addition, the fineness of the thermoplastic resin fibers constituting the nonwoven fabric layer shall be the value calculated from the following formula using the average short fiber diameter of the thermoplastic resin fibers and the density of the thermoplastic resin fibers measured in the "Procedure for Measuring the Average Short Fiber Diameter of the Nonwoven Fabric Layer," rounded to the second decimal place.

[0070] d=(π×ρ×D 2 ) / 400

[0071] Here,

[0072] d: Fineness (dtex) of the thermoplastic resin fibers constituting the nonwoven layer

[0073] ρ: Density of thermoplastic resin fibers constituting the nonwoven layer ρ (g / cm³)

[0074] D: Average staple fiber diameter (μm) of the thermoplastic resin fibers constituting the nonwoven fabric layer.

[0075] The density ρ of the thermoplastic resin fiber is measured based on "8.17.2 Density Gradient Tube Method" of JIS L1013:2010 "Test Method for Chemical Fiber Filament Yarns". A density gradient tube with an appropriately adjusted density range is prepared, and the density of the fiber (g / cm³) is measured to the third decimal place for a fiber sample of approximately 0.1g taken from the nonwoven fabric layer. The same operation is performed on five other samples randomly taken from the nonwoven fabric layer, and the average of the results is calculated and the value rounded to the third decimal place is taken as the density ρ (g / cm³) of the first thermoplastic fiber.

[0076] In addition, the weight W (g / ㎡) per unit area of ​​the nonwoven fabric layer is calculated as follows.

[0077] First, the weight Wt (g / m²) per unit area of ​​the laminated nonwoven fabric is measured based on "6.2 Mass per unit area" of JIS L1913:2010 "Test Method for General Nonwoven Fabrics". Specifically, three test specimens are taken per 1m width of the sample, each cut from the laminated nonwoven fabric to a size of 20cm × 25cm, and the mass (g) of each is weighed in a standard state. The mass per 1m calculated from the average value is rounded to the second decimal place and used as the weight Wt (g / m²) per unit area of ​​the laminated nonwoven fabric.

[0078] Next, using the thickness T of the nonwoven fabric layer and the thickness Tt of the laminated nonwoven fabric obtained by the above-described procedure, the value calculated from the following formula is rounded to the second decimal place and is set as the weight W (g / ㎡) per unit area of ​​the nonwoven fabric layer.

[0079] W = W × T / Tt … Equation.

[0080] The interfiber gap size represented by Equation (1) is a value representing the length of one side of the gap defined by the fibers when assuming a model in which the fibers included in the nonwoven fabric layer are regularly arranged in a grid pattern. It is thought that the smaller this interfiber gap size, the stronger the capillary force acts, and the water-attracting power is improved.

[0081] In the laminated nonwoven fabric of the present invention, the interfiber gap size Ra of the nonwoven fabric layer (A), which has the smallest average short fiber diameter, is set to 200 μm or less, preferably 100 μm or less, and more preferably 80 μm or less. This increases the capillary force of the nonwoven fabric layer (A) when liquid is applied to the outermost surface of the laminated nonwoven fabric, thereby allowing a large amount of liquid to be transferred to the nonwoven fabric layer (A) and enabling good fast drying properties.

[0082] In addition, it is desirable to have an inter-fiber pore size Ra of 30㎛ or more to ensure consistent permeability and absorption.

[0083] The interfiber gap size Ra can be controlled by controlling the average short fiber diameter Da of the thermoplastic resin fibers constituting the nonwoven layer.

[0084] It is preferable that the thickness of the nonwoven fabric layer (A) be 100 μm or more. By making the thickness of the nonwoven fabric layer (A) 100 μm or more, and more preferably 120 μm or more, the liquid absorbed by the laminated nonwoven fabric can be retained more in the nonwoven fabric layer (A), thereby increasing the drainage ratio described later on the surface of the nonwoven fabric layer (A).

[0085] Meanwhile, it is preferable that the thickness of the nonwoven fabric layer (A) be 1000 μm or less. By making the thickness of the nonwoven fabric layer (A) 1000 μm or less, it is possible to prevent liquid from stagnating inside the nonwoven fabric layer (A) and inhibiting liquid transfer between nonwoven fabric layers.

[0086] [Non-woven fabric layer (B)]

[0087] In the laminated stretchable nonwoven fabric of the present invention, the nonwoven layer (B) is defined as a nonwoven layer laminated in contact with the nonwoven layer (A).

[0088] In the laminated nonwoven fabric of the present invention, for at least one of the nonwoven layers (B) laminated in contact with the nonwoven layer (A) (including cases where the nonwoven layer (B) is laminated in contact with only one side of the nonwoven layer (A), the ratio Rb / Ra of the inter-fiber gap size Rb (㎛) calculated by the following formula (2) and Ra (㎛) is 1.1 times or more.

[0089] Rb=(100×Tb×db) / (Wb×Db)-Db … Equation (2)

[0090] Here,

[0091] Tb: Thickness (㎛) of the nonwoven layer (B)

[0092] db: Fineness (dtex) of the thermoplastic resin fibers constituting the nonwoven layer (B)

[0093] Wb: Weight per unit area of ​​the nonwoven layer (B) (g / m²)

[0094] Db: Average short fiber diameter (μm) of the thermoplastic resin fibers constituting the nonwoven layer (B).

[0095] In addition, the method for determining Tb (㎛), db (dtex), Wb (g / m²), and Db (㎛) related to Equation (2) is the same as the thickness T of the nonwoven fabric layer described above, the fineness d of the thermoplastic resin fiber constituting the nonwoven fabric layer, the weight W per unit area of ​​the nonwoven fabric layer, and the average short fiber diameter D of the thermoplastic resin fiber constituting the nonwoven fabric layer.

[0096] By making the Rb / Ra ratio 1.1 times or more, more preferably 1.2 times or more, and even more preferably 1.5 times or more, moisture can be efficiently transferred to the nonwoven layer (A) due to the large difference in capillary force between the nonwoven layer (A) and the nonwoven layer (B), thereby improving fast drying properties.

[0097] Meanwhile, as the ratio of Rb to Ra increases, the ratio of inter-fiber voids within the nonwoven fabric layer (B) naturally increases. In order to suppress the unevenness of weight per unit area that occurs at that time and to suppress the decrease in strength starting from this unevenness of weight per unit area, it is desirable that Rb / Ra be 10.0 times or less.

[0098] It is preferable that the inter-fiber pore size Rb of the nonwoven fabric layer (B) be 100 μm or more. Since Rb is 100 μm or more, and more preferably 120 μm or more, liquid permeability is improved, so the amount of liquid remaining in the nonwoven fabric layer (B) is reduced, and quick drying properties can be obtained.

[0099] It is preferable that the interfiber gap size Rb of the nonwoven fabric layer (B) be 500 μm or less. By making Rb 500 μm or less, the liquid transferred to the nonwoven fabric layer (A) is prevented from seeping out when a load is applied to the laminated nonwoven fabric, thereby maintaining a dry surface.

[0100] In controlling the inter-fiber gap size Rb (㎛) in the nonwoven fabric layer (B) to the aforementioned range, it is preferable that the average short fiber diameter Db of the thermoplastic resin fiber constituting the nonwoven fabric layer (B) is within the range of 15.0㎛ to 30.0㎛.

[0101] The thickness of the nonwoven fabric layer (B) is preferably within the range of 100 to 1000 μm. By making the thickness of the nonwoven fabric layer (B) 100 μm or more, it is possible to suppress the increase in the drainage rate described later caused by some of the moisture retained in the nonwoven fabric layer (A) seeping out. In addition, by making the thickness of the nonwoven fabric layer (B) 1000 μm or less, the liquid absorbed from the nonwoven fabric layer (B) can be rapidly penetrated into the nonwoven fabric layer (A).

[0102] [Laminated Nonwoven Fabric]

[0103] In the laminated nonwoven fabric of the present invention, when physiological saline is absorbed on each of the two sides according to the following procedure, at least one of the four sides, including the absorbent surface that has absorbed physiological saline and the opposite side, preferably has a drainage ratio defined by the following formula (3) of 40% or less.

[0104] (Measurement procedure for the multiple ratio)

[0105] Step 1: Cut out a 5 cm × 5 cm sample from the laminated nonwoven fabric.

[0106] Procedure 2: Prepare two sheets of filter paper compliant with Type 2 of JIS P3801, cut to 5 cm × 5 cm, for one measurement, and measure the mass of each.

[0107] Step 3: Drop 0.250 ± 0.005 mL of physiological saline onto a polypropylene film. At this time, measure the mass of the physiological saline being dropped.

[0108] Step 4: Place a laminated nonwoven fabric over the dropped physiological saline solution with the absorbent surface facing downward, and maintain for 1 minute.

[0109] Step 5: After maintaining Step 4 above, the laminated nonwoven fabric is removed from the polypropylene film, the absorbent surface is placed upward on the first sheet of filter paper, and the second sheet of filter paper is quickly placed on top of it.

[0110] Step 6: Place a 125g weight on top of the second filter paper above so that the pressure becomes 5g / ㎠, and maintain for 1 minute.

[0111] Step 7: After maintaining Step 6 above, remove the weight, measure the mass of each filter paper, and calculate the increase in mass of each filter paper.

[0112] Step 8: Calculate the drainage ratio of each surface in the laminated nonwoven fabric from the following formula.

[0113] Multiplier ratio (%) = 100 × W1 / W0

[0114] Here,

[0115] W0: Mass (g) of physiological saline solution added in the above Step 3

[0116] W1: Mass increase (g) of the filter paper applied to the surface in the above procedure 7.

[0117] The drainage ratio obtained through this process indicates that the lower the value, the less liquid is retained on the surface. In other words, if this drainage ratio is low on the surface that touches the skin, even after the liquid has been absorbed, a dry sensation can be felt when touched.

[0118] In the laminated nonwoven fabric of the present invention, by making the drainage ratio on at least one of the four aforementioned surfaces 40% or less, more preferably 30% or less, and even more preferably 20% or less, the amount of moisture retained on the surface is low, so that a dry surface can be effectively maintained.

[0119] In the laminated nonwoven fabric of the present invention, as an embodiment for achieving the surface drainage ratio as described above, it is preferable that the nonwoven fabric layer (B) is laminated on at least one outermost surface. That is, as described above, since the nonwoven fabric layer (B) is defined as a nonwoven fabric layer laminated in contact with the nonwoven fabric layer (A), in the laminated nonwoven fabric of this preferred embodiment, from at least one side,

[0120] Non-woven layer (B) / Non-woven layer (A) …

[0121] It has a laminated structure such as that. And as described above, since the nonwoven layer (A) is defined as having the smallest average short fiber diameter among the nonwoven layers constituting the laminated nonwoven fabric, when liquid is absorbed from the outermost surface of the nonwoven layer (B) side, which has a relatively large average short fiber diameter, the liquid is rapidly transferred to the nonwoven layer (A) side, where the inter-fiber pore size is controlled to be very small as described above, so the drainage ratio of the outermost surface of the nonwoven layer (B) side is reduced, and fast drying properties can be obtained.

[0122] In addition, the laminated nonwoven fabric of the present invention preferably has a drainage ratio of 50% or more on the side opposite to the surface where the aforementioned drainage ratio is 40% or less. By making this drainage ratio 50% or more, more preferably 60% or more, the absorbed liquid can be smoothly transferred from the surface that absorbed the liquid to the other side without leaving the absorbed liquid inside the laminated nonwoven fabric.

[0123] In the laminated nonwoven fabric of the present invention, in order to control the drainage ratio of the surface opposite to the surface that has absorbed the liquid to the aforementioned range, it is preferable to place a nonwoven fabric layer (A) with high capillary force on one surface.

[0124] The laminated nonwoven fabric of the present invention preferably has an absorption rate of 20 seconds or less measured from at least one surface.

[0125] The absorption rate referred to herein is measured based on "7.1.1 Dropping Method" of JIS L1907:2010 "Test Method for Absorbency of Textile Products". One drop of water is dropped onto a laminated nonwoven fabric, and the time until it is absorbed and the specular reflection on the surface disappears is measured. The simple average of this value is calculated from the values ​​measured at 10 other locations, the unit is set to seconds, and the value is rounded to the first decimal place and used as the absorption rate referred to in the present invention.

[0126] The absorption rate being 20 seconds or less, more preferably 10 seconds or less, indicates good performance in removing moisture attached to the surface.

[0127] It is preferable that the weight per unit area of ​​the laminated nonwoven fabric of the present invention be 10 to 100 g / m².

[0128] By making the weight per unit area preferably 10 g / m² or more, more preferably 13 g / m² or more, and even more preferably 15 g / m² or more, a laminated nonwoven fabric with mechanical strength suitable for practical use can be obtained. Meanwhile, by making the weight per unit area preferably 100 g / m² or less, and more preferably 50 g / m² or less, a laminated nonwoven fabric having suitable flexibility suitable for use as a nonwoven fabric for sanitary materials can be obtained.

[0129] In the laminated nonwoven fabric of the present invention, it is preferable that each nonwoven fabric layer is integrated. The integration referred to herein means that the nonwoven fabric layers are joined by interlocking of fibers, fixation by components such as adhesives, or fusion of thermoplastic resins constituting each layer.

[0130] The laminated nonwoven fabric of the present invention may be provided with a hydrophilic agent for the purpose of increasing absorbency.

[0131] [Hygiene Materials]

[0132] The sanitary material of the present invention has excellent absorbency and quick-drying properties, as at least a portion of it is composed of the laminated nonwoven fabric of the present invention.

[0133] The sanitary material of the present invention can be suitably used for health-related purposes such as medical care and nursing. The sanitary material of the present invention can be suitably used mainly for disposable items, such as paper diapers, sanitary pads, gauze, bandages, masks, gloves, adhesive bandages, etc.

[0134] Among them, in paper diapers, it can be used as a component at each location, such as a top sheet, back sheet, and side gather.

[0135] In the diaper as a hygiene material of the present invention, it is preferable that the top sheet is composed of the laminated nonwoven fabric of the present invention. When the laminated nonwoven fabric of the present invention is used as the top sheet of a diaper, if the nonwoven fabric layer (B) is installed so as to be on the skin-side of the top sheet, excreted urine can be rapidly absorbed and quickly transferred to the nonwoven fabric layer (A), thereby keeping the surface of the top sheet dry.

[0136] In addition, it is preferable that the diaper as a hygiene material of the present invention is composed of at least a portion of the waist portion made of the laminated nonwoven fabric of the present invention. When the laminated nonwoven fabric of the present invention is used as part of the waist portion of the diaper, if the nonwoven fabric layer (B) is installed on the skin-side of the waist portion of the diaper, sweat can be rapidly absorbed and quickly transferred to the nonwoven fabric layer (A), thereby keeping the surface of the waist portion dry.

[0137] In addition, the sanitary material of the present invention can also be suitably used as a mask. In the mask as a sanitary material of the present invention, it is preferable that the inner layer is composed of the laminated nonwoven fabric of the present invention. The inner layer referred to in the present invention refers to the layer installed closest to the mouth among the face coverings. If the laminated nonwoven fabric of the present invention is used such that the nonwoven fabric layer (B) is installed on the skin side, even if sweat or exhaled air condenses and moisture adheres to the skin side, it is immediately absorbed into the laminated nonwoven fabric, so the skin side can be kept dry, and thus it can be used without discomfort when worn.

[0138] [Method for manufacturing laminated nonwoven fabric]

[0139] Next, a preferred embodiment for manufacturing the laminated nonwoven fabric of the present invention will be described in detail.

[0140] The manufacturing method of the nonwoven layer (A) and the nonwoven layer (B) constituting the laminated nonwoven fabric of the present invention can be selected from known manufacturing methods such as the spunbond method, the meltblow method, and the short fiber carding method.

[0141] Among them, the spunbond method can be cited as a desirable method because of its excellent productivity.

[0142] Hereinafter, preferred embodiments of manufacturing the laminated nonwoven fabric of the present invention based on the spunbond method are described, but are not limited thereto.

[0143] The spunbond method is a method for manufacturing nonwoven fabric that requires the process of melting a thermoplastic resin raw material, spinning it from a spinneret, cooling and solidifying the resulting yarn, pulling it with an ejector to stretch it, collecting it on a moving net to form a nonwoven fiber web, and then heat-bonding it.

[0144] Various shapes, such as circular or rectangular, can be adopted for the spinnerets or ejectors used. Among these, a combination of a rectangular spinneret and a rectangular ejector is a desirable embodiment in that it uses relatively less compressed air and is less likely to cause fusion or abrasion between the strands.

[0145] In the present invention, it is preferable that the spinning temperature be between (melting temperature of the raw material thermoplastic resin + 10°C) and (melting temperature of the raw material thermoplastic resin + 100°C). By keeping the spinning temperature within the above range, a stable molten state can be achieved, thereby obtaining excellent spinning stability.

[0146] In addition, when manufacturing the nonwoven layer (A), the average inter-fiber gap can be reduced by making the fiber diameter thinner. For this reason, in order to stably manufacture fine fibers, it is desirable to make the melt viscosity of the polymer used in the nonwoven layer (A) 100 Pa·s or less, and more desirable to make it 50 Pa·s or less.

[0147] The melt viscosity of the polymer referred to here is the deformation rate of 1216s when the moisture content of the chip-shaped polymer is reduced to 200 ppm or less by a vacuum dryer, the deformation rate is varied in steps, and the measurement temperature is the same as the spinning temperature. -1 It is the value in.

[0148] The ejected filament is then cooled. Methods for cooling the ejected filament include, for example, forcibly spraying cold air onto the filament, natural cooling at the ambient temperature surrounding the filament, and adjusting the distance between the spinneret and the ejector, or a combination of these methods may be adopted. Additionally, the cooling conditions can be appropriately adjusted by considering the discharge rate per single hole of the spinneret, the spinning temperature, and the ambient temperature.

[0149] Next, the cooled and solidified thread is pulled by compressed air sprayed from an ejector and stretched.

[0150] In the laminated nonwoven fabric of the present invention, the average interfiber gap size of the nonwoven fabric layer (A) and the nonwoven fabric layer (B) can be controlled by the diameter of the constituent fibers.

[0151] The diameter of the fiber is determined by the discharge rate per discharge hole of the spinneret and the traction speed, i.e., the spinning speed. For this reason, it is desirable to determine the discharge rate and the spinning speed so that the desired inter-fiber gap size can be controlled to a diameter that is obtained.

[0152] It is preferable that the spinning speed be 2000 m / min or higher. By setting the spinning speed to 2000 m / min or higher, and more preferably 3000 m / min or higher, high productivity is achieved, and the orientation crystallization of the fibers proceeds, allowing for the production of long fibers of high strength.

[0153] The long fiber strands stretched by traction in this manner are collected in a moving net, formed into sheets, and then provided to a heat bonding process.

[0154] The laminated nonwoven fabric of the present invention is formed by laminating nonwoven fabric layers. As a method for laminating nonwoven fabric layers, for example, a method in which a subsequent nonwoven fabric layer obtained by collecting thermoplastic resin fibers by the spunbond method is continuously collected in-line on a nonwoven fabric layer obtained by collecting thermoplastic resin fibers by the spunbond method on a collecting net as described above, and laminated together, or a method in which two or more nonwoven fabric layers obtained separately are overlapped offline and laminated together by thermal compression, etc., may be adopted. Among these, a method in which a subsequent nonwoven fabric layer is continuously collected in-line on a nonwoven fabric layer and laminated together by thermal bonding is a preferred embodiment due to its excellent productivity.

[0155] As a method for integrating nonwoven layers by thermal bonding to form the laminated nonwoven fabric of the present invention, methods of thermal bonding using various rolls may be employed, such as a thermal embossing roll having a pattern (irregularity) formed on the surface of each of a pair of upper and lower rolls, a thermal embossing roll comprising a combination of a roll having a flat surface on one side and a roll having a pattern (irregularity) formed on the surface of the other roll, and a thermal calender roll comprising a combination of an upper and lower pair of flat rolls, or methods of thermal compression such as ultrasonic bonding in which thermal welding is performed by the ultrasonic vibration of a horn may be employed. Furthermore, as a method for integrating the laminated nonwoven fabric of the present invention by thermal bonding, the so-called air-through method, which involves spraying hot air, may also be cited.

[0156] Among these, the method of heat bonding by a pair of upper and lower heat rollers is preferred because it allows the nonwoven layer (A) to be densified by bonding while compressing the laminated nonwoven layer, thereby reducing the size of the interfiber gaps.

[0157] When manufacturing the laminated nonwoven fabric of the present invention by heat pressing with a heat roll, it is preferable to have a linear pressure of 100 N / cm or more on the laminated nonwoven fabric between the rolls, so that the nonwoven fabric layer (A) can be sufficiently densified.

[0158] In addition, in the laminated nonwoven fabric, it is preferable to process the surface closer to the nonwoven layer (A) than the nonwoven layer (B) with a flat roll, and the surface on the opposite side with a heat embossing roll that has been cut. By adopting this combination of rolls, it becomes difficult for the nonwoven layer (B) to be compressed relative to the nonwoven layer (A), so a large difference in the interfiber gap size between the nonwoven layer (A) and the nonwoven layer (B) can be secured.

[0159] A hydrophilic agent may be applied to the laminated nonwoven fabric of the present invention before winding. Methods for applying a hydrophilic agent to the laminated nonwoven fabric include application by a kiss roll or spray, or dip coating; however, application by a kiss roll is preferred due to the ease of controlling uniformity and the amount of application.

[0160] Examples

[0161] Next, the present invention will be described in detail based on examples. However, the present invention is not limited to these examples. Furthermore, regarding the measurement of each physical property, unless otherwise specified, the measurement was performed based on the method described above.

[0162] (1) Specific characteristics of the stacking interface

[0163] The lamination interface of the laminated nonwoven fabric was determined by the aforementioned "procedure for determining the lamination interface." In addition, a high-resolution 3D X-ray microscope, the "nano3DX" manufactured by Rigaku Co., Ltd., was used. The resolution was set to 0.6 μm / voxel.

[0164] (2) Average short fiber diameter

[0165] The average short fiber diameter of each nonwoven fabric layer was measured according to the aforementioned "procedure for measuring the average short fiber diameter of the nonwoven fabric layer." In addition, the "S-5500" manufactured by Hitachi High Technologies Co., Ltd. was used as the scanning electron microscope (SEM), and "WinROOF2015" manufactured by Shoji Mitani Co., Ltd. was used as the image analysis software.

[0166] (3) Average short fiber diameter in the manufacturing process of laminated nonwoven fabric

[0167] For each thermoplastic resin fiber, a fiber sample was randomly taken from a nonwoven fiber web collected on a net, and a cross-section of the fiber was captured using a scanning electron microscope "S-5500" manufactured by Hitachi High Technologies Co., Ltd. at a magnification level capable of observing a single fiber. Subsequently, measurements were performed as described above using "WinROOF2015" manufactured by Shoji Mitani Co., Ltd. as image analysis software.

[0168] When measuring the average short fiber diameter during the manufacturing process of the laminated nonwoven fabric, it was confirmed that in this example and comparative example, an average short fiber diameter was obtained that was not different from the measurement taken according to the "procedure for measuring the average short fiber diameter of the nonwoven fabric layer" above.

[0169] (4) Thickness

[0170] The thickness of the laminated nonwoven fabric and each nonwoven fabric layer was measured according to the aforementioned "procedure for measuring the thickness of the nonwoven fabric layer."

[0171] (5) Thickness by simple method

[0172] For a cross-section perpendicular to the machine direction of the laminated nonwoven fabric, an image was captured using a scanning electron microscope (S-5500 manufactured by Hitachi High Technologies Co., Ltd.) at a magnification level capable of observing the thickness. Based on the captured image, the thickness of the laminated nonwoven fabric and each nonwoven layer was measured.

[0173] When the thickness of the laminated nonwoven fabric and each nonwoven layer was measured using a simple method, it was confirmed that in this example and comparative example, a thickness was obtained that was not different from the measurement taken according to the "procedure for measuring the thickness of the nonwoven layer" above.

[0174] (6) Interfiber gap size

[0175] The interfiber void size of the nonwoven fabric layer was calculated using the following formula.

[0176] R=(100×T×d) / (W×D)-D

[0177] Here,

[0178] T: Thickness of the nonwoven fabric layer (㎛). Measured by (4) above.

[0179] d: Fineness (dtex) of the thermoplastic resin fibers constituting the nonwoven layer. It is measured by the definition of d mentioned above.

[0180] W: Weight per unit area of ​​the nonwoven fabric layer (g / m²). It is measured according to the definition of W described above. Furthermore, in this example and comparative example, it was confirmed that there is no difference from the weight per unit area of ​​the nonwoven fiber web layer described later.

[0181] D: Average single fiber diameter (μm) of the thermoplastic resin fibers constituting the nonwoven fabric layer. Measured by (2) above.

[0182] (7) Multiple ratio

[0183] The drainage ratio of both sides of the laminated nonwoven fabric was measured according to the aforementioned "procedure for measuring drainage ratio." In this example and comparative example, the side on which the nonwoven fabric layer (B) is placed as the outermost surface was designated as the "absorbent surface" in step 4 of the "procedure for measuring drainage ratio." Additionally, the number of samples was set to 5, the average of the values ​​was calculated, and the result was rounded to the first decimal place.

[0184] (8) Absorption rate

[0185] The absorption rate was measured based on "7.1.1 Dropping Method" of JIS L1907:2010 "Test Method for Absorbency of Textile Products". One drop of water was applied to a laminated nonwoven fabric, and the time until it was absorbed and the specular reflection on the surface disappeared was measured. The simple average of the values ​​measured at 10 other locations was calculated, the unit was set to seconds, and the result was rounded to the first decimal place.

[0186] (9) Absorbent and quick-drying

[0187] After measuring the ratio of the above (7) for the laminated nonwoven fabric, healthy general adults (30 people in total, 15 men and 15 women) touched the “absorbent side” with their hands and evaluated the dryness of the surface in the following 3 stages. For each nonwoven fabric, the average score of the evaluation results was calculated and used as the tactile sensation of the laminated nonwoven fabric.

[0188] 5: The surface has a dry texture and feels dry.

[0189] 3: There is no moisture on the surface, but it is moist.

[0190] 1: There is moisture on the surface, and it is moist.

[0191] [Example 1]

[0192] (Non-woven fiber web layer (A))

[0193] Polypropylene (PP, melt viscosity 30 Pa·s) was melted in an extruder and extruded from a rectangular die at a single-hole discharge rate of 0.30 g / min. After cooling and solidifying the extruded fibers, they were pulled and stretched by compressed air with an ejector pressure of 0.10 MPa in a rectangular ejector, collected on a moving net, and a nonwoven fiber web layer (A) was obtained by the spunbond method. The fibers constituting the obtained nonwoven fiber web layer (A) had an average single fiber diameter of 10.6 μm. In addition, the weight per unit area was 35.0 g / m².

[0194] (Non-woven fiber web layer (B))

[0195] Polypropylene (PP), identical to the raw material used in the nonwoven fiber web layer (A), was melted in an extruder and extruded from a rectangular die at a single-hole discharge rate of 0.85 g / min. After cooling and solidifying the extruded fibers, they were pulled and stretched by compressed air with an ejector pressure of 0.08 MPa in a rectangular ejector, and collected on the moving net-shaped nonwoven fiber web layer (A) to obtain a nonwoven fiber web layer (B) by the spunbond method. The fibers constituting the obtained nonwoven fiber web layer (B) had an average single fiber diameter of 20.4 μm. In addition, the weight per unit area was set to 30.0 g / m².

[0196] A laminated fiber web with a two-layer structure of nonwoven fiber web layer (A) / nonwoven fiber web layer (B) was obtained by in-line lamination of a nonwoven fiber web layer (B) on a nonwoven fiber web layer (A).

[0197] (Laminated nonwoven fabric)

[0198] The obtained laminated fiber web was heat-bonded at a linear pressure of 300 N / cm and a heat bonding temperature of 125°C using an embossing roll having a pair of upper and lower heating mechanisms, wherein the upper roll was a metal embossing roll in which circular convex portions were arranged in a zigzag pattern with the same pitch in both MD and CD directions, and the lower roll was a metal flat roll. Subsequently, a hydrophilic treatment was performed to obtain a laminated nonwoven fabric with a weight per unit area of ​​65.0 g / m².

[0199] For the obtained laminated nonwoven fabric, the thickness of each layer, the inter-fiber pore size, the drainage ratio, the absorption rate, and the absorption and quick-drying properties were evaluated. The thickness of nonwoven layer (A) was 300 µm, and the inter-fiber pore size was 54 µm. In addition, the thickness of nonwoven layer (B) was 420 µm, and the inter-fiber pore size was 181 µm. The results are shown in Table 1.

[0200] [Example 2]

[0201] A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the single-hole extrusion amount in the process of obtaining the nonwoven fiber web layer (A) was 0.80 g / min and the single-hole extrusion amount in the process of obtaining the nonwoven fiber web layer (B) was 1.20 g / min. The evaluation results of the obtained laminated nonwoven fabric are shown in Table 1.

[0202] [Example 3]

[0203] A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the single-hole extrusion amount in the process of obtaining the nonwoven fiber web layer (B) was 0.35 g / min. The evaluation results of the obtained laminated nonwoven fabric are shown in Table 1.

[0204] [Example 4]

[0205] A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the weight per unit area of ​​the nonwoven fiber web layer (A) was 15.0 g / m² and the weight per unit area of ​​the nonwoven fiber web layer (B) was 13.0 g / m². The evaluation results of the obtained laminated nonwoven fabric are shown in Table 1.

[0206] [Example 5]

[0207] A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the weight per unit area of ​​the nonwoven fiber web layer (A) was 10.0 g / m². The evaluation results of the obtained laminated nonwoven fabric are shown in Table 1.

[0208] [Example 6]

[0209] (Non-woven fiber web layer (A))

[0210] A nonwoven fiber web layer (A) was obtained in the same manner as in Example 1.

[0211] (Non-woven fiber web layer (B))

[0212] A nonwoven fiber web layer (B) was obtained in the same manner as in Example 1, except that the tensile and stretched yarn was directly captured on a moving net.

[0213] After obtaining the nonwoven fiber web layer (A) and the nonwoven fiber web layer (B) respectively, they were laminated by an offline method to obtain a laminated fiber web with a two-layer structure of nonwoven fiber web layer (A) / nonwoven fiber web layer (B).

[0214] (Laminated nonwoven fabric)

[0215] The obtained laminated fiber web was heat-bonded in the same manner as in Example 1 and subjected to hydrophilic processing to obtain a laminated nonwoven fabric. The evaluation results of the obtained laminated nonwoven fabric are shown in Table 1.

[0216] [Example 7]

[0217] The polymer used for the nonwoven fabric layer (A) and the nonwoven fabric layer (B) was polyethylene glycol copolymer polyethylene terephthalate (copolymerized PET, where the copolymerization rate of polyethylene glycol is 8 mass% of the polymer).

[0218] (Non-woven fiber web layer (A))

[0219] As a raw material polymer for the fiber, copolymerized polyethylene terephthalate (copolymerized PET) was used, in which polyethylene glycol was copolymerized into a polymer at a mass of 8%. Using copolymerized PET, a nonwoven fiber web layer (A) was obtained in the same manner as in Example 1, except that the running speed of the net was changed. The fibers constituting the obtained spunbond nonwoven layer (A) had an average staple fiber diameter of 8.5 μm. In addition, the weight per unit area was set to 30.0 g / m².

[0220] (Non-woven fiber web layer (B))

[0221] A nonwoven fiber web layer (B) was obtained in the same manner as in Example 1, except that the same copolymer PET used as the raw material in the nonwoven fiber web layer (A) was used. The characteristics of the fibers constituting the obtained spunbond nonwoven fabric layer (B) were such that the average single fiber diameter was 17.5 μm. In addition, the weight per unit area was set to 37.0 g / m², which is 30.0 g / m².

[0222] (Laminated nonwoven fabric)

[0223] A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that the heat bonding temperature was set to 200°C. The thickness of the nonwoven layer (A) was 270 μm, and the interfiber pore size was 73 μm. In addition, the thickness of the nonwoven layer (B) was 350 μm, and the interfiber pore size was 158 μm. The evaluation results of the obtained laminated nonwoven fabric are shown in Table 1.

[0224] [Comparative Example 1]

[0225] A laminated nonwoven fabric was obtained in the same manner as in Example 1, except that in the process of obtaining the nonwoven fiber web layer (A), the single-hole discharge rate was 1.20 g / min and the pressure at the ejector was 0.08 MPa, and in the process of obtaining the nonwoven fiber web layer (B), the single-hole discharge rate was 1.20 g / min. The fibers constituting the obtained nonwoven fiber web layer (A) had an average single fiber diameter of 22.0 μm. In addition, the thickness of the nonwoven fabric layer (A) was 430 μm, and the inter-fiber pore size was 245 μm. The evaluation results of the obtained laminated nonwoven fabric are shown in Table 1.

[0226]

[0227] As shown in Table 1, it can be seen that Examples 1 to 7 exhibit excellent absorption and quick-drying properties. In particular, Examples 1 and 6 achieved a high level of compatibility between absorption rate and absorption and quick-drying properties. On the other hand, Comparative Example 1 showed low absorption and quick-drying properties.

Claims

Claim 1 A laminated nonwoven fabric formed by laminating nonwoven layers containing thermoplastic resin fibers, wherein in the nonwoven layer (A) having the smallest average single fiber diameter among the nonwoven layers, the inter-fiber gap size Ra (㎛) calculated by the following formula (1) is 200㎛ or less, and for at least one of the nonwoven layers (B) laminated in contact with the nonwoven layer (A), the inter-fiber gap size Rb (㎛) calculated by the following formula (2) is 100㎛ or more. Ra = (100 × Ta × da) / (Wa × Da) - Da … Equation (1) where, Ta: thickness of nonwoven layer (A) (㎛) da: fineness of thermoplastic resin fibers constituting nonwoven layer (A) (dtex) Wa: weight per unit area of ​​nonwoven layer (A) (g / m²) Da: average short fiber diameter of thermoplastic resin fibers constituting nonwoven layer (A) (㎛) Rb = (100 × Tb × db) / (Wb × Db) - Db … Equation (2) where, Tb: thickness of nonwoven layer (B) (㎛) db: fineness of thermoplastic resin fibers constituting nonwoven layer (B) (dtex) Wb: weight per unit area of ​​nonwoven layer (B) (g / m²) Db: average short fiber diameter of thermoplastic resin fibers constituting nonwoven layer (B) (㎛). Claim 2 A laminated nonwoven fabric according to claim 1, wherein the ratio of Rb to Ra, Rb / Ra, is 1.1 or greater. Claim 3 A laminated nonwoven fabric according to claim 1 or 2, wherein, when physiological saline is absorbed on each of the two sides of the laminated nonwoven fabric according to the following procedure, at least one of the four sides, including the absorbent surface that has absorbed the physiological saline and the surface opposite it, has a drainage ratio defined by the following formula (3) of 40% or less. Procedure 1: A 5 cm × 5 cm sample is cut from the laminated nonwoven fabric. Procedure 2: Two sheets of filter paper conforming to Type 2 of JIS P3801 are cut to 5 cm × 5 cm for one measurement, and the mass of each is measured. Procedure 3: 0.250 ± 0.005 mL of physiological saline is dropped onto a polypropylene film. At this time, the mass of the dropping physiological saline solution is measured and recorded. Step 4: Place the laminated nonwoven fabric over the dropping physiological saline solution with the absorbent surface facing downward, and maintain it for 1 minute. Step 5: After maintaining it in Step 4, remove the laminated nonwoven fabric from the polypropylene film, place the absorbent surface facing upward on the first sheet of filter paper, and quickly place the second sheet of filter paper on top of it. Step 6: Place a 125g weight over the second sheet of filter paper so that the pressure becomes 5g / ㎠, and maintain it for 1 minute. Step 7: After maintaining it in Step 6, remove the weight, measure the mass of each sheet of filter paper, and calculate the mass increase of each sheet of filter paper. Step 8: Calculate the drainage ratio of each surface of the laminated nonwoven fabric from the following formula. Drainage ratio (%) = 100 × W1 / W0, where W0: the above steps Mass (g) of physiological saline solution dropped in 3 W1: Mass increase (g) of the filter paper applied to its surface in the above procedure 7. Claim 4 A laminated nonwoven fabric according to paragraph 3, wherein the drainage ratio of the side opposite to the surface having a drainage ratio of 40% or less is 50% or more. Claim 5 A laminated nonwoven fabric according to claim 1 or 2, wherein on at least one surface, the absorption rate measured by the dropping method of JIS L1907:2010 is 20 seconds or less. Claim 6 A sanitary material comprising at least a portion of the laminated nonwoven fabric described in paragraph 1 or 2. Claim 7 In paragraph 6, the sanitary material is a diaper. Claim 8 In claim 7, a sanitary material in which the top sheet is composed of the above-mentioned laminated nonwoven fabric. Claim 9 In claim 7, a sanitary material comprising at least a portion of the waste portion being composed of the laminated nonwoven fabric. Claim 10 In claim 7, the sanitary material is a mask, and the inner layer of the mask is composed of the laminated nonwoven fabric.

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