Laminated nonwoven fabric and method for manufacturing the same

Abstract

To provide a laminated nonwoven fabric excellent in both surface smoothness and flexibility; and to provide a method for manufacturing the same.SOLUTION: A laminated nonwoven fabric is composed of fibers and is formed by laminating at least one spun-bonded nonwoven fabric layer and at least one melt-blown nonwoven fabric layer. The spun-bonded nonwoven fabric layer and the melt-blown nonwoven fabric layer are both composed of fibers comprising a polypropylene-based resin. The laminated nonwoven fabric has a basis weight of 30 g / m2 or more and 90 g / m2 or less. When y (the number of yarns / mm2) represents the number of yarns having a flatness ratio of 0.80 or greater and 1.25 or less per unit cross-sectional area of the laminated nonwoven fabric, and x (g / m2) represents the basis weight of the laminated nonwoven fabric, the laminated nonwoven fabric satisfies the following expression: 0≤a≤600, where a=y-10.7x.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a laminated nonwoven fabric. [Background technology]

[0002] BACKGROUND ART In recent years, nonwoven fabrics have been used in a variety of applications, including industrial materials, civil engineering materials, building materials, daily necessities, agricultural materials, sanitary materials, and medical materials.

[0003] Among these, nonwoven fabrics made from polyolefin resins are attracting attention for their use in labels, taking advantage of the water repellency that is one of the resin's properties. Nonwoven fabrics used for labels must have a smooth surface to ensure good printability and flexibility to conform to the shape of containers, etc.

[0004] Various laminated nonwoven fabrics have been proposed for similar purposes. For example, Patent Document 1 proposes a nonwoven fabric for use as a sterilization packaging material, which has a fibrous layer (I) with a specific porosity as the heat-sealable surface, and a fibrous layer (II) with a specific range of fiber specific surface area and number of fibers equivalent to 1 cm per 1 mg as the barrier layer, and in which the fibrous layer (I) and the fibrous layer (II) are laminated. It is described that this nonwoven fabric for use as a sterilization packaging material can be provided that has both easy-peel properties and barrier properties.

[0005] Furthermore, Patent Document 2 proposes a packaging material for sterilization made of a continuous long-fiber nonwoven fabric having a surface roughness coefficient Ra within a specific range. It is described that this material has a seal strength that prevents the bag from breaking under all sterilization conditions, and also has suitable peeling properties such as easy peel and clean peel, resulting in a high-performance, high-quality packaging material for sterilization with excellent quality stability. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2020 / 196340 [Patent Document 2] Japanese Patent Application Publication No. 2019-172348 Summary of the Invention [Problem to be solved by the invention]

[0007] Laminated nonwoven fabrics of conventional materials, such as polypropylene spunbonded nonwoven fabric and meltblown nonwoven fabric, as described in Patent Documents 1 and 2, have excellent surface smoothness, but their flexibility is reduced by calendaring, and therefore, when used as labels as is, they have the problem of peeling off from containers, etc. The present invention has been made in view of the above circumstances, and its object is to provide a laminated nonwoven fabric that achieves both surface smoothness and flexibility, and a method for producing the same. [Means for solving the problem]

[0008] The present invention and its preferred embodiments include the following configurations. [1] A laminated nonwoven fabric comprising at least one spunbond nonwoven fabric layer and at least one meltblown nonwoven fabric layer, the at least one spunbonded nonwoven fabric layer and the at least one meltblown nonwoven fabric layer are both composed of fibers made of a polypropylene-based resin composition mainly containing a polypropylene-based resin, The basis weight of the laminated nonwoven fabric is 30 g / m 2 More than 90g / m 2 The number of yarns per unit cross-sectional area of ​​the laminated nonwoven fabric is y (y / mm 2 ), the basis weight of the laminated nonwoven fabric is x (g / m 2 ) A laminated nonwoven fabric that satisfies the following relational expression. 0≦a≦600 Here, a=y-10.7x [2] The laminated nonwoven fabric according to [1], wherein the average surface roughness of at least one of the laminated nonwoven fabrics is 1.0 μm or more and 10.0 μm or less. [3] The apparent density of the laminated nonwoven fabric is 0.30 g / cm 3 More than 0.60g / cm 3 The laminated nonwoven fabric according to [1] or [2], which is: [4] The tensile strength and elongation product per unit area of ​​the laminated nonwoven fabric, calculated by the following formula, is 0.05 (N / 50 mm) / (g / m 2 ) or more 0.50(N / 50mm) / (g / m 2 The laminated nonwoven fabric according to any one of [1] to [3], wherein: Tensile strength and elongation product per unit weight ((N / 50mm) / (g / m 2 )) = [Average value of maximum strength (N / 50mm)] x [Average value of elongation at maximum strength (-)] / basis weight (g / m 2 ) [5] The laminated nonwoven fabric according to any one of [1] to [4], wherein the polypropylene resin composition contains a low-crystalline polyolefin resin. [6] The laminated nonwoven fabric according to [5], wherein the content of the low-crystalline polyolefin resin in the polypropylene resin composition is 1% by mass or more and 20% by mass or less. [7] The laminated nonwoven fabric according to [5] or [6], wherein the low-crystalline polyolefin resin is an ethylene-propylene copolymer. [8] A method for producing a laminated nonwoven fabric according to any one of [1] to [7], comprising the steps of: forming at least one layer of a first spunbond nonwoven web; forming at least one layer of a meltblown nonwoven web on the at least one layer of the first spunbond nonwoven web; forming a second spunbond nonwoven web on the at least one layer of the meltblown nonwoven web to form a laminated web; preheating only one surface of the laminated web by bringing the heating surface of a heating device into contact with the laminated web to obtain a preheated laminated web; and fusing the preheated laminated web using a heat calendar roll consisting of a pair of upper and lower flat rolls to form a laminated nonwoven fabric, wherein the preheating temperature in the step of obtaining the preheated laminated web is 40°C or higher and 95°C or lower. [9] A label comprising the laminated nonwoven fabric according to any one of [1] to [7]. [Effects of the Invention]

[0009] According to the present invention, a laminated nonwoven fabric having excellent surface smoothness and flexibility and suitable for label applications can be obtained. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below. However, the present invention is not limited to the embodiments described below as long as the gist of the present invention is not exceeded.

[0011] The laminated nonwoven fabric of the present invention is a laminated nonwoven fabric comprising at least one spunbonded nonwoven fabric layer and at least one meltblown nonwoven fabric layer, and both the at least one spunbonded nonwoven fabric layer and the at least one meltblown nonwoven fabric layer are composed of fibers made of a polypropylene-based resin composition mainly containing a polypropylene-based resin. Herein, "polypropylene-based resin" in the present invention refers to a resin whose main repeating unit is a propylene unit. Hereinafter, the at least one spunbonded nonwoven fabric layer will be simply referred to as "the spunbonded nonwoven fabric layer," and the at least one meltblown nonwoven fabric layer will be simply referred to as "the meltblown nonwoven fabric layer." In the present invention, the polypropylene-based resin composition used in the fibers constituting the spunbonded nonwoven fabric layer will be referred to as polypropylene-based resin composition P. S The polypropylene resin composition used for the fibers constituting the melt-blown nonwoven fabric layer is referred to as polypropylene resin composition P M It is sometimes referred to as.

[0012] Examples of the polypropylene resin include a homopolymer of propylene and a copolymer of propylene with various α-olefins.

[0013] The proportion of propylene units in the polypropylene-based resin is preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more, which can maintain good spinnability and improve the strength of the laminated nonwoven fabric.

[0014] The polypropylene resin composition may contain, in addition to polypropylene, other polyolefin resins such as polyethylene and poly-4-methyl-1-pentene, thermoplastic elastomers, and the like.

[0015] Among the other polyolefin resins, low-crystalline polyolefin resins are preferred from the viewpoint of imparting flexibility. The low-crystalline polyolefin resin is a polyolefin resin in which a copolymerization monomer such as ethylene or 1-butene is incorporated into a regular polypropylene chain, and for example, an ethylene-propylene copolymer or a low stereoregular polypropylene is preferably used. From the viewpoint of flexibility, an ethylene-propylene copolymer is more preferred.

[0016] The ethylene content of the ethylene-propylene copolymer is preferably 1% by mass or more and 50% by mass or less. When the ethylene content of the ethylene-propylene copolymer is 1% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, flexibility can be achieved with a low addition amount. When the ethylene content of the ethylene-propylene copolymer is 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, the occurrence of partial viscosity unevenness during fiber spinning can be prevented, and good spinnability can be maintained.

[0017] The content of the low-crystalline polyolefin resin in the polypropylene resin composition is preferably 1% by mass or more, more preferably 3% by mass or more, and even more preferably 8% by mass or more, in order to fully exert the effect of imparting flexibility. On the other hand, the content of other resins in the polypropylene resin composition is preferably 20% by mass or less, more preferably 15% by mass or less, in order to fully exert the properties of the polypropylene resin.

[0018] Additives such as antioxidants, weathering agents, light stabilizers, anti-fogging agents, blocking agents, lubricants, nucleating agents, and pigments such as titanium oxide may be added to the polypropylene resin composition as needed, provided that the effects of the present invention are not impaired.

[0019] The content of the other resin in the polypropylene resin composition can be calculated by subjecting the laminated nonwoven fabric to infrared spectroscopic analysis and differential scanning calorimetry.

[0020] The polypropylene resin composition P S The polypropylene resin composition P preferably has a melt flow rate (sometimes abbreviated as MFR) of 75 g / 10 min or more and 850 g / 10 min or less. S By setting the MFR to 75 g / 10 min or more, more preferably 120 g / 10 min or more, and even more preferably 155 g / 10 min or more, the stress during drawing can be reduced, and stable spinning becomes possible even when drawn at a high spinning speed. This reduces the fiber diameter of the spunbonded nonwoven fabric layer, making the surface smooth and allowing for a laminated nonwoven fabric with excellent printability. On the other hand, S The polypropylene resin composition P S As a result, the molecular weight of the nonwoven fabric increases and the strength of each fiber increases, making it possible to obtain a laminated nonwoven fabric that is strong enough to be used as a label, for example.

[0021] The polypropylene resin composition P M The polypropylene resin composition P preferably has an MFR of 200 g / 10 min or more and 2500 g / 10 min or less. M By setting the MFR of the polypropylene resin composition P to 200 g / 10 min or more, more preferably 400 g / 10 min or more, and even more preferably 600 g / 10 min or more, the stress during stretching is reduced, so that a melt-blown nonwoven fabric layer having a small fiber diameter can be obtained while maintaining productivity. M By setting the MFR to 2500 g / 10 min or less, more preferably 2000 g / 10 min or less, and even more preferably 1500 g / 10 min or less, the spinneret back pressure increases and fluctuations in the resin discharge rate can be suppressed, resulting in a uniform fiber diameter in the melt-blown nonwoven fabric layer and a laminated nonwoven fabric with uniform texture.

[0022] In the present invention, the MFR of the polypropylene resin composition is measured by ASTM D1238 (Method A), which specifies that the MFR of polypropylene is measured under a load of 2.16 kg and at a temperature of 230°C.

[0023] The polypropylene resin composition P S and the polypropylene resin composition P M The MFR can also be adjusted by blending two or more resins with different MFRs. In this case, the MFR of the resin blended with the main polypropylene resin (referring to the polypropylene resin that accounts for the largest mass % in the polypropylene resin composition) is preferably 10 g / 10 min to 1000 g / 10 min, more preferably 20 g / 10 min to 800 g / 10 min, and even more preferably 30 g / 10 min to 600 g / 10 min. This can prevent the blended polypropylene resin composition from having uneven viscosity, which can lead to non-uniform fineness or poor spinnability.

[0024] Furthermore, in order to prevent the occurrence of local viscosity variations during fiber spinning, to make the fiber fineness uniform, and to further reduce the fiber diameter as described below, the MFR may be increased by decreasing the molecular weight of the resin used. Examples of methods for increasing the MFR include a method of thermally decomposing the resin by heating it before use, or a method of heat-treating it by adding a peroxide.

[0025] The melting point of the polypropylene resin composition is preferably 120°C to 200°C. By setting the melting point to preferably 120°C or higher, more preferably 130°C or higher, and even more preferably 140°C or higher, heat resistance sufficient for practical use is more likely to be obtained. Furthermore, by setting the melting point to preferably 200°C or lower, more preferably 180°C or lower, it becomes easier to cool the yarn discharged from the spinneret, suppressing fusion between fibers and facilitating stable spinning. Here, the melting point (Tmr) of the polypropylene resin composition refers to the maximum melting peak temperature obtained by measuring the polypropylene resin composition by differential scanning calorimetry (DSC).

[0026] The cross-sectional shape of the fibers constituting the spunbonded nonwoven fabric layer may be round or flat, with a round cross-section being a more preferred embodiment because it has excellent spinnability and can be spun at a high spinning speed to produce fibers with excellent single yarn strength.

[0027] The fibers constituting the spunbonded nonwoven fabric layer preferably have an average single fiber diameter of 6.5 μm or more and 11.9 μm or less. By setting the average single fiber diameter to preferably 6.5 μm or more, more preferably 7.5 μm or more, and even more preferably 8.4 μm or more, deterioration of spinnability can be prevented and a nonwoven fabric layer with a stable average single fiber diameter can be formed. On the other hand, by setting the average single fiber diameter to preferably 11.9 μm or less, more preferably 11.2 μm or less, and even more preferably 10.6 μm or less, a laminated nonwoven fabric with high flexibility and uniformity and excellent texture uniformity suitable for practical use can be obtained, even if the content of the melt-blown nonwoven fabric layer in the laminated nonwoven fabric is low. The average single fiber diameter can be controlled by the spinning temperature, single-hole throughput, spinning speed, etc., as described below.

[0028] The average single fiber diameter (μm) of the fibers constituting the spunbonded nonwoven fabric layer is calculated by the following procedure. (1) Ten small sample pieces are randomly taken from the laminated nonwoven fabric. (2) Surface photographs are taken at a magnification of 500 to 1000 times using a scanning electron microscope (SEM) (for example, Keyence Corporation's "VHX-D500"), and the widths of 10 fibers from each sample (100 fibers in total) are measured. If the cross section of the fiber is irregular, the cross-sectional area is measured, and the diameter of a circle with the same cross-sectional area is determined. (3) Calculate the average single fiber diameter (μm) from the average of the 100 measured values.

[0029] The fibers constituting the melt-blown nonwoven fabric layer preferably have an average single fiber diameter of 0.1 μm or more and 8.0 μm or less. By setting the average single fiber diameter to preferably 0.1 μm or more, more preferably 0.4 μm or more, fibers can be easily collected when forming the melt-blown nonwoven fabric layer, preventing scattering to the surroundings and resulting in a more uniform laminated nonwoven fabric. On the other hand, by setting the average fiber diameter to preferably 8.0 μm or less, more preferably 7.0 μm or less, the flexibility of the laminated nonwoven fabric can be improved. The average single fiber diameter can be controlled by the spinning temperature, single-hole output rate, spinning speed, etc., as described below.

[0030] The average single fiber diameter (μm) of the fibers constituting the meltblown nonwoven fabric layer of the present invention is calculated by the following procedure. (1) Ten small sample pieces are randomly taken from the laminated nonwoven fabric. (2) The collected test specimen is cut using a freezing microtome, and the resulting cross section is subjected to a conductive treatment. The cross section is then photographed at a magnification of 4000 to 10000 times using an SEM (for example, Keyence Corporation's "VHX-D500"). (3) Measure the width of 100 fibers in total, 10 fibers from each meltblown nonwoven fabric layer of each sample. (4) The average single fiber diameter (μm) is calculated from the average value of the 100 measured values.

[0031] Specific lamination structures of the laminated nonwoven fabric include, for example, an SMS nonwoven fabric formed by laminating (spunbond nonwoven fabric layer) / (meltblown nonwoven fabric layer) / (spunbond nonwoven fabric layer) in this order from the surface of the spunbond nonwoven fabric layer side, an SM nonwoven fabric formed by laminating (spunbond nonwoven fabric layer) / (meltblown nonwoven fabric layer), and an SM nonwoven fabric formed by laminating (spunbond nonwoven fabric layer) / (meltblown nonwoven fabric layer) / (meltblown nonwoven fabric layer). Examples of such nonwoven fabrics include an SMMS nonwoven fabric laminated with a (spunbond nonwoven fabric layer) / (spunbond nonwoven fabric layer) / (meltblown nonwoven fabric layer) / (meltblown nonwoven fabric layer) / (spunbond nonwoven fabric layer), and an SSMMS nonwoven fabric laminated with a (spunbond nonwoven fabric layer) / (meltblown nonwoven fabric layer) / (meltblown nonwoven fabric layer) / (spunbond nonwoven fabric layer).

[0032] The laminated nonwoven fabric has a number of yarns per unit cross-sectional area of ​​the laminated nonwoven fabric having an aspect ratio of 0.80 to 1.25 (y yarns / mm 2 ), the basis weight of the laminated nonwoven fabric is x (g / m 2 ), the following relation is satisfied: 0≦a≦600 Here, a=y-10.7x By setting the above a to 0 or more, preferably 30 or more, more preferably 50 or more, and even more preferably 100 or more, a suitable amount of voids in the nonwoven fabric is ensured, resulting in a laminated nonwoven fabric with excellent printability. On the other hand, by setting the above a to 600 or less, preferably 500 or less, more preferably 400 or less, and even more preferably 300 or less, a laminated nonwoven fabric with excellent surface smoothness is obtained.

[0033] In the present invention, the number y of yarns per unit cross-sectional area in the laminated nonwoven fabric is 0.80 or more and 1.25 or less (yarns / mm 2 ) is measured as follows: (1) Randomly take 20 test pieces measuring 20 mm x 20 mm from the laminated nonwoven fabric. (2) The collected specimen is cut using a freezing microtome, the resulting cross section is subjected to a conductive treatment, and the cross section is photographed using a scanning electron microscope (SEM) (e.g., Keyence Corporation's "VHX-D500") at a magnification of 1000 to 1800. If the SEM photograph of the cross section contains fused areas due to embossing or the like, the observation field is shifted and the photograph is taken again. (3) The thickness of the laminated nonwoven fabric is measured at five points on the SEM photograph of the cross section, and the average value is taken as the thickness (t) (mm) of the laminated nonwoven fabric. (4) The length (l) (mm) of the laminated nonwoven fabric included in the cross-sectional SEM photograph is measured. (5) Among the fibers included in the cross-sectional SEM photograph, the cross-sectional area is 30 μm 2 The flattening ratio of the above fibers is measured. The flattening ratio is the ratio (A / B or B / A) of the longest line segment (A) to the shortest line segment (B) of any line segments that pass through the center of the fiber cross section and have both end points on the circumference. Note that the flattening ratio is not measured for fibers at the edge of the cross-sectional SEM photograph, where the fiber cross section cannot be completely observed, or for fibers where the interface is unclear due to fusion between fibers. (6) Among the fibers contained in the cross-sectional SEM photograph, the number h (of fibers) with an aspect ratio of 0.80 or more and 1.25 or less is calculated. (7) Divide h by t and l to obtain the number of yarns with an aspect ratio of 0.80 or more and 1.25 or less per unit cross-sectional area (h / (t×l)) (number / mm 2 ) is calculated. (8) For 20 test pieces, the steps (2) to (7) are carried out, and the average value of (h / (t×l)) for the 20 test pieces is rounded to the nearest whole number, and the result is used as the number of yarns with an aspect ratio of 0.80 or more and 1.25 or less per unit cross-sectional area (h / (t×l)) (pieces / mm 2 )

[0034] h / (t×l) can be adjusted by adjusting the average single fiber diameter of the spunbonded nonwoven fabric layer, and can also be controlled by appropriately adjusting the preheating conditions (temperature, linear pressure, etc.) and the thermal bonding conditions (bonding area shape, compression ratio, temperature, linear pressure, etc.) described below.

[0035] The basis weight of the laminated nonwoven fabric is 30 g / m 2 More than 90g / m 2 The basis weight is 30 g / m or less. 2 or more, preferably 35 g / m 2 More preferably, 40 g / m 2 By adjusting the weight to 90 g / m or more, a laminated nonwoven fabric having a mechanical strength sufficient for practical use can be obtained. 2 Less than 70 g / m 2 By setting the following, it is possible to obtain a laminated nonwoven fabric that is flexible enough to conform to a container or the like when used as a label.

[0036] In the present invention, the basis weight of the laminated nonwoven fabric is measured by the following procedure in accordance with "6.2 Mass per unit area" of JIS L1913:2010 "Testing methods for general nonwoven fabrics." (1) Take three 20cm x 25cm test pieces per meter of sample width. (2) Weigh the mass (g) of each at standard conditions. (3) The average value is 1m 2 Mass per unit (g / m 2 )

[0037] The apparent density of the laminated nonwoven fabric is 0.30 g / cm 3 More than 0.60g / cm 3It is preferable that the apparent density is 0.30 g / cm or less. 3 More preferably, 0.35 g / cm 3 More preferably, 0.40 g / cm 3 By satisfying the above conditions, the occurrence of fluffing and delamination can be suppressed, and the laminated nonwoven fabric can have strength and ease of handling. 3 or less, more preferably 0.55 g / cm 3 or less, more preferably 0.50 g / cm 3 The apparent density can be controlled by appropriately adjusting the average single fiber diameter of the fibers and / or the preheating conditions (temperature, linear pressure, etc.) and the thermal bonding conditions (shape of the bonded portion, compression rate, temperature, linear pressure, etc.) described below.

[0038] Apparent density of nonwoven fabric (g / cm 3 ) is calculated by the following procedure. (1) The thickness (mm) of the nonwoven fabric is measured according to the following procedure in accordance with "6.1.1 Method A" of JIS L1913:2010 "General nonwoven fabric testing methods." (A) Using a pressure probe with a diameter of 10 mm, measure the thickness of the nonwoven fabric at 10 equally spaced points per meter across the width with an accuracy of 0.01 mm under a load of 10 kPa. (B) Round the average of the above 10 points to the nearest hundredth. (2) From the above unrounded basis weight and thickness, calculate the apparent density using the following formula, and round off to the third decimal place. Apparent density (g / cm 3 ) = [weight (g / m 2 )] / [Thickness (mm)]×10 -3 .

[0039] The laminated nonwoven fabric preferably has an arithmetic mean roughness of at least one surface of 1.0 μm or more and 10.0 μm or less. By adjusting the arithmetic mean roughness to 1.0 μm or more, more preferably 2.0 μm or more, and even more preferably 3.0 μm or more, a laminated nonwoven fabric with excellent flexibility can be obtained. On the other hand, by adjusting the arithmetic mean roughness to 10.0 μm or less, more preferably 9.0 μm or less, and even more preferably 8.0 μm or less, a laminated nonwoven fabric with excellent surface smoothness and printability can be obtained. The arithmetic mean roughness can be controlled by appropriately adjusting the average single fiber diameter of the fibers and / or the preheating conditions (temperature, linear pressure, etc.) and thermal bonding conditions (shape of the bonded portion, compression rate, temperature, linear pressure, etc.) described below.

[0040] In the present invention, the arithmetic mean roughness Ra of the surface of the laminated nonwoven fabric is determined in accordance with "4.2.1 Arithmetic mean height of profile curve" in JIS B0601:2013 "Geometric product specifications (GPS) - Surface texture: Profile curve method - Terms, definitions and surface texture parameters," and is measured as follows: (1) Test pieces measuring 100 mm x 100 mm are taken from the laminated nonwoven fabric at equal intervals across the width of the laminated nonwoven fabric, 10 pieces per meter. (2) The test piece is set on the sample stage, and a surface roughness measuring instrument (for example, a small surface roughness measuring instrument "SURFTEST SJ-210" manufactured by Mitutoyo Corporation) is used to measure the contour curves in the warp direction (the longitudinal direction of the laminated nonwoven fabric, i.e., MD direction) and the weft direction (the width direction of the laminated nonwoven fabric, i.e., CD direction) for both sides of the laminated nonwoven fabric, and the arithmetic mean roughness Ra (μm) is calculated. (3) For each of both sides, the measured values ​​of all test pieces are averaged and rounded to the nearest tenth to obtain the arithmetic mean roughness Ra (μm).

[0041] The air permeability per unit area of ​​the laminated nonwoven fabric of the present invention is 0.01 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or more 5.0(cm 3 / (cm 2 ·sec)) / (g / m 2The air permeability per unit area is preferably 5.0 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or less, more preferably 2.0 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or less, more preferably 1.0 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or less, more preferably 0.5 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or less, it is possible to maintain the water resistance required for label applications, etc. On the other hand, the air permeability per unit area is 0.01 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or more, more preferably 0.02 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or more, more preferably 0.04 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or more, more preferably 0.06 (cm 3 / (cm 2 ·sec)) / (g / m 2 ) or more, the ink can be quickly penetrated into the nonwoven fabric.

[0042] The air permeability can be adjusted by the basis weight, average single fiber diameter, basis weight of the melt-blown nonwoven fabric layer, and thermocompression bonding conditions (bonding rate, temperature, and linear pressure).

[0043] In the present invention, the air permeability per unit area weight of the laminated nonwoven fabric is measured by the following procedure in accordance with "6.8.1 Frazier type method" of JIS L1913:2010 "General nonwoven fabric testing methods." (1) Cut a test piece measuring 80 cm x 100 cm from the laminated nonwoven fabric. (2) At a barometer pressure of 125 Pa, measurements are taken at any 20 points on the test piece. (3) The average of the 20 points is calculated as the basis weight (g / m 2 ) and round to the third decimal place.

[0044] The tensile strength and elongation product per unit area of ​​the laminated nonwoven fabric is 0.05 (N / 50 mm) / (g / m 2 ) or more 0.50(N / 50mm) / (g / m 2 ) or less. The tensile strength and elongation product per unit area is preferably 0.05 (N / 50 mm) / (g / m 2 ) or more, more preferably 0.10 (N / 50mm) / (g / m 2 ) or more, more preferably 0.15 (N / 50mm) / (g / m 2 ) or more, more preferably 0.18 (N / 50mm) / (g / m 2 ) or more, a laminated nonwoven fabric with excellent strength can be obtained even at a low basis weight. On the other hand, the tensile strength / elongation product per basis weight is 0.50 (N / 50 mm) / (g / m 2 ) or less, more preferably 0.35 (N / 50mm) / (g / m 2 ) or less, it is possible to prevent the flexibility of the laminated nonwoven fabric from being extremely reduced and the texture from being impaired.

[0045] The tensile strength-elongation product per unit area weight can be controlled by appropriately adjusting the MFR of the polypropylene resin composition, additives, the average single fiber diameter of the core-sheath type composite fiber, and / or the spinning speed, preheating conditions (temperature, linear pressure, etc.), and thermal bonding conditions (shape of the bonded part, compression rate, temperature, linear pressure, etc.) described below.

[0046] In the present invention, the tensile strength / elongation product per unit area of ​​the laminated nonwoven fabric is a value measured by the following procedure in accordance with "6.3 Tensile strength and elongation (ISO method)" of JIS L1913:2010 "Testing methods for general nonwoven fabrics." (1) Take three 50mm x 300mm test pieces per meter of nonwoven fabric width, with the long side facing the warp direction (longitudinal direction of the nonwoven fabric) of the nonwoven fabric. (2) Set the test piece in the tensile testing machine with a gripping distance of 200 mm. (3) A tensile test is carried out at a tensile speed of 100 mm / min, and the maximum strength and the elongation at the maximum strength are measured. Here, the elongation is not converted into a percentage (%), but is expressed as the ratio of elongation to the initial grip distance. (4) Obtain the average value of the maximum strength and elongation at maximum strength measured for each test piece, calculate the tensile strength-elongation product per unit area weight based on the following formula, and round off to one decimal place. Tensile strength and elongation product per unit weight ((N / 50mm) / (g / m 2 )) = [Average value of maximum strength (N / 50mm)] x [Average value of elongation at maximum strength (-)] / basis weight (g / m 2 ).

[0047] [Manufacturing method of laminated nonwoven fabric] Next, a preferred embodiment of the method for producing the laminated nonwoven fabric of the present invention will be specifically described.

[0048] The method for producing the laminated nonwoven fabric of the present invention includes the steps of forming at least one layer of a first spunbond nonwoven web, forming at least one layer of a meltblown nonwoven web on the at least one layer of the first spunbond nonwoven web, forming at least one layer of a second spunbond nonwoven web on the at least one layer of the meltblown nonwoven web to form a laminated web (the steps up to this point are referred to as "step 1"), preheating by contacting only one surface of the laminated web with the heating surface of a heating device to obtain a preheated laminated web (referred to as the "preheating step"), and fusing the preheated laminated web using a thermal calendar roll consisting of a pair of upper and lower flat rolls to form a laminated nonwoven fabric (referred to as the "fusing step").

[0049] (Process 1) In step 1, the spunbond nonwoven fabric layer and the meltblown nonwoven fabric layer can be formed by the spunbonding method and the meltblown nonwoven fabric layer, respectively. As a method for laminating these to form a laminate, a method can be preferably employed in which fibers formed by the meltblown method are deposited directly on the spunbond nonwoven fabric layer formed first to form a meltblown nonwoven fabric layer, and then fibers formed by the spunbonding method are deposited to form a spunbond nonwoven fabric layer, thereby forming a laminate by sequentially depositing additional fibers on the obtained nonwoven fabric layers.

[0050] The spunbond nonwoven fabric layer can be formed by spinning a molten polypropylene resin composition into long fibers from a spinneret, cooling and stretching the fibers, and then collecting the fibers on a moving net. The stretching may also be performed by suction with compressed air using an ejector or the like.

[0051] The spinneret and ejector may have various shapes such as a round shape, a rectangular shape, etc. Among them, a combination of a rectangular spinneret and a rectangular ejector is preferably used because it uses a relatively small amount of compressed air, is excellent in energy cost, is less likely to cause fusion or friction between the yarns, and facilitates opening of the yarns.

[0052] In the present invention, a polypropylene resin composition is melted in an extruder, metered, and fed to a spinneret to be spun into continuous fibers. The spinning temperature when the polypropylene resin composition is melted and spun is preferably 200°C or higher and 270°C or lower, more preferably 210°C or higher and 260°C or lower, and even more preferably 220°C or higher and 250°C or lower. By setting the spinning temperature within the above range, a stable molten state can be achieved, and excellent spinning stability can be obtained.

[0053] The spun continuous fiber yarn is cooled by, for example, forcibly blowing cold air onto the yarn, naturally cooling at the ambient temperature around the yarn, or adjusting the distance between the spinneret and the ejector, or a combination of these methods can be used. The cooling conditions can be appropriately adjusted in consideration of the output per hole of the spinneret, the spinning temperature, the ambient temperature, etc.

[0054] Next, the cooled and solidified yarn may be drawn by compressed air injected from an ejector. The spinning speed is preferably 3000 m / min to 6500 m / min, more preferably 3500 m / min to 6500 m / min, and even more preferably 4000 m / min to 6500 m / min. A spinning speed of 3000 m / min to 6500 m / min results in high productivity, promotes fiber orientation and crystallization, and enables the production of high-strength long fibers.

[0055] The meltblown nonwoven fabric layer can be formed using a known manufacturing method. A polypropylene resin composition is melted in an extruder and fed to a nozzle. Hot air is blown onto the extruded filaments to thin them. The meltblown nonwoven fabric layer is then formed on a previously formed spunbonded or meltblown nonwoven fabric layer placed on a collection net or a moving net. The meltblowing method does not require complex processes, can easily produce fine fibers of several micrometers, and can exhibit high water resistance.

[0056] The long fibers can be collected on a moving net or on an already formed spunbond or meltblown nonwoven web that is placed on the moving net to further form a nonwoven web.

[0057] (Preheating process) In the preheating step, only one surface of the laminated web is preheated by contacting the heating surface of a heating device. Preheating is preferably performed by fusing the collected fiber web using a pair of upper and lower flat rolls, or by placing a flat roll or a heating plate above a net conveyor and fusing the web between the net conveyor and the flat roll or heating plate. This method allows for a laminated nonwoven fabric with excellent surface smoothness while maintaining the gap. The "flat roll" used in these methods refers to a metal roll or elastic roll with a smooth surface. Furthermore, the upper and lower pair of flat rolls refers to a pair of metal rolls or a pair of metal rolls and elastic rolls. Here, an elastic roll refers to a roll made of a material that is more elastic than a metal roll. Examples of elastic rolls include so-called paper rolls made of paper, cotton, aramid paper, etc., as well as resin rolls made of urethane resins, epoxy resins, silicone resins, polyester resins, hard rubber, etc., or mixtures of these.

[0058] In this preheating, when a pair of upper and lower flat rolls are used for fusion bonding, only one of the flat rolls serves as a heated surface. To give an example of an embodiment, only one of the flat rolls has a heating mechanism such as a heater and is a roll (heated roll) heated to a temperature described below, while the other flat roll does not have such a heating mechanism, or has a heating mechanism but the heater is switched off. In this embodiment, the "heated surface" refers to the surface of the heated roll.

[0059] In this preheating, when a flat roll is placed above a net conveyor and preheating is performed between the net conveyor and the flat roll, the flat roll is preferably made of metal, and a heating mechanism such as a heater is provided only on this flat roll, which is heated to a temperature described below. This flat roll is the heated roll, and the surface of this heated roll is the "heated surface" mentioned above.

[0060] In this preheating, when a heating plate is placed above the net conveyor and preheating is performed between the net conveyor and the heating plate, the heating plate is preferably made of metal, and a heating mechanism such as a heater is provided only on this heating plate, and the surface of this heating plate that comes into contact with the fiber web is the "heating surface."

[0061] In the preheating step, the temperature of the heated surface is preferably 40°C or higher and 95°C or lower. By setting the temperature of the heated surface to 40°C or higher, more preferably 45°C or higher, and even more preferably 50°C or higher, thermal crystallization of the fibers before thermocompression bonding can be promoted, preventing a loss of flexibility in the nonwoven fabric after thermocompression bonding. Furthermore, deterioration of the texture due to the surface layer of the nonwoven fabric being turned up or blown away during transport on the net can be prevented, improving transportability from the time the yarns are collected to the time they are thermocompression bonded. On the other hand, by setting the surface temperature to 95°C or lower, more preferably 75°C or lower, and even more preferably 70°C or lower, thermal crystallization of the fibers before thermocompression bonding can be suppressed, resulting in a nonwoven fabric with even better surface smoothness.

[0062] Furthermore, when a flat roll is used in the preheating step, the linear pressure of the heating surface is preferably 1 N / cm or more and 100 N / cm or less. By setting the lower limit of the linear pressure range to 1 N / cm or more, preferably 5 N / cm or more, the fiber web on the heating surface can be sufficiently preheated. On the other hand, by setting the upper limit of the range to 100 N / cm or less, preferably 50 N / cm or less, heat is transferred to the interior of the fiber web on the heating surface, thermal crystallization is suppressed, and sufficient pressure bonding can be achieved during thermal bonding.

[0063] (fusion process) In the fusion step, a method for fusion bonding the laminated web is preferably used, which uses a heat calendar roll consisting of a pair of upper and lower flat (smooth) rolls, which allows the thickness of the spunbonded nonwoven fabric to be adjusted to a constant value, and a laminated nonwoven fabric with excellent surface smoothness can be obtained.

[0064] As the surface material of the heat calender roll, it is preferable to use a pair of metal rolls in order to obtain a sufficient heat-pressure bonding effect.

[0065] The surface temperature of the hot calender roll in the fusion step is preferably Tm-50°C to Tm-5°C, where Tm is the melting point of the polypropylene resin composition used. By setting the surface temperature of the hot calender roll to Tm-50°C or higher, more preferably Tm-45°C or higher, it is possible to obtain a laminated nonwoven fabric with adequate fusion strength for practical use. Furthermore, by setting the surface temperature of the hot calender roll to Tm-5°C or lower, more preferably Tm-8°C or lower, excessive fusion is suppressed, and the laminated nonwoven fabric can be obtained with adequate flexibility and processability suitable for use in label applications.

[0066] The linear pressure of the heat calendar roll is preferably 50 N / cm or more and 500 N / cm or less. By setting the linear pressure of the heat calendar roll to 50 N / cm or more, more preferably 100 N / cm or more, and even more preferably 150 N / cm or more, it is possible to obtain a laminated nonwoven fabric with adequate fusion and practical strength. On the other hand, by setting the linear pressure of the heat calendar roll to 500 N / cm or less, more preferably 400 N / cm or less, and even more preferably 300 N / cm or less, it is possible to obtain a laminated nonwoven fabric with adequate flexibility and processability suitable for use in label applications.

[0067] In the present invention, in order to adjust the thickness of the laminated nonwoven fabric, thermocompression bonding can be performed using a pair of upper and lower flat rolls before and / or after the fusion bonding using the above-mentioned thermal calendar rolls. The pair of upper and lower flat rolls refers to metal rolls or elastic rolls with smooth surfaces, and a pair of metal rolls or a pair of metal rolls and elastic rolls can be used.

[0068] The term "elastic roll" used herein refers to a roll made of a material that has greater elasticity than a metal roll. Examples of elastic rolls include so-called paper rolls made of paper, cotton, aramid paper, etc., and rolls made of resins such as urethane resin, epoxy resin, silicone resin, polyester resin, hard rubber, and mixtures of these.

[0069] [label] As described above, the laminated nonwoven fabric of the present invention has excellent surface smoothness and flexibility, and is therefore suitable for a variety of uses, including labels, protective clothing, sanitary materials, agricultural materials, and the like.

[0070] Among these, labels comprising the laminated nonwoven fabric are preferred because they can take advantage of the surface smoothness and flexibility of the laminated nonwoven fabric. The label referred to here is a label formed by printing and / or dyeing information such as trademarks, product names, classification symbols, and destination addresses, as well as designs, on the surface of the laminated nonwoven fabric. The label of the present invention is not limited to labels affixed to articles such as postal items and cardboard boxes for home delivery, but may also be affixed to products primarily used indoors, such as personal computers, mobile phones, stationery, and beverage bottles, as well as products primarily used outdoors, such as automobiles, motorcycles, and bicycles.

[0071] Therefore, it is also preferable that the label of the present invention has an adhesive layer on the back side of the surface (design surface) on which the characters etc. are printed, which is made of an acrylic adhesive, a silicone adhesive, a rubber adhesive, etc. Depending on the purpose, this adhesive layer may be arranged so that the entire surface of the label is uniformly covered with the resin, or may be arranged so that the resin is locally arranged in a dotted or striped pattern.

[0072] In addition, in order to further impart weather resistance and water resistance to the label of the present invention, it is also preferable that the surface (design surface) on which the above-mentioned characters etc. are printed is uniformly covered with a resin such as natural resin, acrylic resin, urethane resin, polyethylene or polypropylene by applying a varnish coat, UV coat, lamination or the like. [Example]

[0073] The laminated nonwoven fabric of the present invention will be specifically described based on examples. However, the present invention is not limited to these examples. In measuring each physical property, unless otherwise specified, the measurement was performed according to the above-mentioned method.

[0074] (1) Weight of laminated nonwoven fabric (g / m 2 ) The basis weight of the laminated nonwoven fabric was measured based on the above-mentioned method.

[0075] (2) Number of threads y (threads / mm 2 ) Based on the above-mentioned method, the number y of yarns having an aspect ratio of 0.80 or more and 1.25 or less per unit cross-sectional area was measured.

[0076] (3) Average single fiber diameter (μm) of spunbond nonwoven fabric layer and meltblown nonwoven fabric layer The scanning electron microscope used was a VHX-D500 manufactured by Keyence Corporation, and measurements were carried out according to the method described above.

[0077] (4) Apparent density of the laminated nonwoven fabric (g / cm 3) The apparent density of the laminated nonwoven fabric was calculated based on the above-mentioned method.

[0078] (5) Tensile strength and elongation product of laminated nonwoven fabric ((N / 50mm) / (g / m 2 )) The tensile strength-elongation product of the laminated nonwoven fabric was calculated based on the above-mentioned method.

[0079] (6) Bending resistance (mm) and flexibility of laminated nonwoven fabric In accordance with "6.7.3 41.5° cantilever method" of JIS L1913:2010 "General nonwoven fabric testing methods," five 25mm wide x 250mm test pieces were taken and placed on a horizontal table with a 45° inclined surface, with the short side of the test piece aligned with the scale baseline. The test piece was manually slid in the direction of the inclined surface, and when the center point of one end of the test piece came into contact with the inclined surface, the movement length of the position of the other end was read on the scale. Measurements were taken on both sides of the five test pieces, and the average value was calculated.

[0080] The flexibility was evaluated on a scale of 1 to 3 according to the following criteria. A score of 2 or higher was judged to be "sufficiently flexible." A higher score indicates better performance. 3: The bending resistance is 120 mm or less. 2: The bending resistance is greater than 120 mm and less than or equal to 170 mm. 1: Bending resistance is greater than 170 mm.

[0081] (7) Surface roughness (μm), surface smoothness The surface roughness was measured using a small surface roughness measuring instrument "SURFTEST SJ-210" manufactured by Mitutoyo Corporation, using the method described above.

[0082] The surface smoothness was evaluated on a scale of 1 to 3 according to the following criteria. A score of 2 or higher was judged to be "sufficient surface smoothness." A higher score indicates better performance. 3: Surface roughness is 5.0 μm or less. 2: The surface roughness is greater than 5.0 μm and less than or equal to 10.0 μm. 1: Surface roughness is greater than 10.0 μm.

[0083] (8) Overall rating When the total score for flexibility and surface smoothness was 6, the overall evaluation was "A," when the total score for flexibility and surface smoothness was 5, the overall evaluation was "B," and when the scores for flexibility and surface smoothness were each 2, for a total of 4, the overall evaluation was "C," with A to C being considered pass. On the other hand, when the score for either flexibility or surface smoothness was 1, the overall evaluation was "F."

[0084] [Example 1] (First spunbond nonwoven web) A polypropylene resin consisting of a homopolymer with an MFR of 200 g / 10 min and a melting point of 163°C was mixed with a low-crystalline polyolefin resin, an ethylene-propylene copolymer with an MFR of 20 g / 10 min and a copolymerization rate of 20 wt% ethylene, so that the blending ratio of the ethylene-propylene copolymer was 10 mass%. The mixed resin composition was melted in an extruder and spun from a rectangular die with a hole diameter of φ0.30 mm and a hole depth of 2 mm at a spinning temperature of 235°C and a single-hole throughput rate of 0.40 g / min. The spun yarn was cooled and solidified, and then pulled and stretched in a rectangular ejector with compressed air at an ejector pressure of 0.35 MPa. The yarn was collected on a moving net and spun into a polypropylene long fiber fiber with a basis weight of 31 g / m. 2 A first spunbond nonwoven fabric web was formed. The average single fiber diameter of the fibers constituting the first spunbond nonwoven fabric web was 11.2 μm.

[0085] (meltblown nonwoven web) A polypropylene resin consisting of a homopolymer with an MFR of 1100 g / min was melted in an extruder and spun from a die with a hole diameter of 0.25 mm at a spinning temperature of 260°C and a single-hole throughput of 0.10 g / min. Air was then sprayed onto the yarn at an air temperature of 290°C and an air pressure of 0.10 MPa, and the yarn was collected on the first spunbond nonwoven fabric web to form a meltblown nonwoven fabric web. The basis weight of the meltblown nonwoven fabric web was 13 g / m. 2 The average single fiber diameter was 1.0 μm.

[0086] (Second spunbond nonwoven web) A second spunbond nonwoven web was formed on the meltblown nonwoven web under the same conditions as for the first spunbond nonwoven web, and the total basis weight was 75 g / m. 2 A laminated fiber web of 1000 .mu.m was obtained.

[0087] (Laminated nonwoven fabric) The laminated fiber web was preheated at a linear pressure of 30 N / cm using a pair of upper and lower flat rolls, one of which was heated to 60°C. It was then heat-sealed at a linear pressure of 300 N / cm and a thermal bonding temperature of 155°C using a thermal calender roll consisting of a pair of upper and lower flat (smooth) rolls to obtain a laminated nonwoven fabric. The evaluation results are shown in Table 1.

[0088] [Example 2] (First spunbond nonwoven web) A first spunbond nonwoven web was formed in the same manner as in Example 1, except that a polypropylene resin consisting of a homopolymer having an MFR of 200 g / 10 min and a melting point of 163° C. was fed to the extruder.

[0089] (meltblown nonwoven web) A meltblown nonwoven web was formed in the same manner as in Example 1 on the first spunbond nonwoven web.

[0090] (Second spunbond nonwoven web) A second spunbond nonwoven web was formed on the meltblown nonwoven web under the same conditions as for the first spunbond nonwoven web, and the total basis weight was 75 g / m. 2 A laminated fiber web of 1000 .mu.m was obtained.

[0091] (Laminated nonwoven fabric) The laminated fiber web was subjected to preheating and heat fusion in the same manner as in Example 1 to obtain a laminated nonwoven fabric. The evaluation results are shown in Table 1.

[0092] [Example 3] (First spunbond nonwoven web) A homopolymer polypropylene resin with an MFR of 200 g / 10 min and a melting point of 163°C was melted in an extruder and spun from a rectangular die with a hole diameter of 0.30 mm and a hole depth of 2 mm at a spinning temperature of 235°C and a single hole throughput of 0.30 g / min. After the spun yarn was cooled and solidified, it was pulled and stretched in a rectangular ejector with compressed air at an ejector pressure of 0.50 MPa, and collected on a moving net to produce a polypropylene long fiber with a basis weight of 31 g / m. 2 A first spunbond nonwoven fabric web was formed. The average single fiber diameter of the fibers constituting the first spunbond nonwoven fabric web was 8.0 μm.

[0093] (meltblown nonwoven web) A meltblown nonwoven web was formed in the same manner as in Example 1 on the first spunbond nonwoven web.

[0094] (Second spunbond nonwoven web) A second spunbond nonwoven web was formed on the meltblown nonwoven web under the same conditions as for the first spunbond nonwoven web, and the total basis weight was 75 g / m. 2 A laminated fiber web of 1000 .mu.m was obtained.

[0095] (Laminated nonwoven fabric) The laminated fiber web was subjected to preheating and heat fusion in the same manner as in Example 1 to obtain a laminated nonwoven fabric. The evaluation results are shown in Table 1.

[0096] [Example 4] (First spunbond nonwoven web) A first spunbond nonwoven web was formed in the same manner as in Example 1, except that a polypropylene resin consisting of a homopolymer having an MFR of 200 g / 10 min and a melting point of 163° C. was fed to the extruder.

[0097] (meltblown nonwoven web) A meltblown nonwoven web was formed in the same manner as in Example 1 on the first spunbond nonwoven web.

[0098] (Second spunbond nonwoven web) A second spunbond nonwoven web was formed on the meltblown nonwoven web under the same conditions as for the first spunbond nonwoven web, and the total basis weight was 75 g / m. 2 A laminated fiber web of 1000 .mu.m was obtained.

[0099] (Laminated nonwoven fabric) The laminated fiber web was preheated and heat-sealed in the same manner as in Example 1, except that the preheating temperature was 95°C and the heat-sealing temperature was 135°C, to obtain a laminated nonwoven fabric. The evaluation results are shown in Table 1.

[0100] [Comparative Example 1] (First spunbond nonwoven web) A first spunbond nonwoven web was formed in the same manner as in Example 1, except that a polypropylene resin consisting of a homopolymer having an MFR of 200 g / 10 min and a melting point of 163° C. was fed to the extruder.

[0101] (meltblown nonwoven web) A meltblown nonwoven web was formed in the same manner as in Example 1 on the first spunbond nonwoven web.

[0102] (Second spunbond nonwoven web) A second spunbond nonwoven web was formed on the meltblown nonwoven web under the same conditions as for the first spunbond nonwoven web, and the total basis weight was 75 g / m. 2 A laminated fiber web of 1000 .mu.m was obtained.

[0103] (Laminated nonwoven fabric) The laminated fiber web was preheated at a linear pressure of 30 N / cm using a pair of flat rolls, one of which was heated to 60°C. Next, a thermal embossing roll, consisting of a combination of a flat (smooth) roll on one side and an engraved (concave and convex) roll on the other side, was used to heat-seal the web at a linear pressure of 300 N / cm and a thermal bonding temperature of 155°C to obtain a laminated nonwoven fabric. The evaluation results are shown in Table 1.

[0104] Comparative Example 2 (First spunbond nonwoven web) A homopolymer polypropylene resin with a MFR of 200 g / 10 min and a melting point of 163°C was fed into the extruder, and the weight per unit area was 41 g / m 2 A first spunbond nonwoven fabric web was formed in the same manner as in Example 1, except that the conditions were adjusted so that:

[0105] (meltblown nonwoven web) On the first spunbond nonwoven web, a nonwoven fabric having a basis weight of 18 g / m 2 A melt-blown nonwoven fabric web was formed in the same manner as in Example 1, except that the conditions were adjusted so that:

[0106] (Second spunbond nonwoven web) A second spunbond nonwoven web was formed on the meltblown nonwoven web under the same conditions as for the first spunbond nonwoven web, and the total basis weight was 100 g / m. 2 A laminated fiber web of 1000 .mu.m was obtained.

[0107] (Laminated nonwoven fabric) The laminated fiber web was subjected to preheating and heat fusion in the same manner as in Example 1 to obtain a laminated nonwoven fabric. The evaluation results are shown in Table 1.

[0108] Comparative Example 3 (First spunbond nonwoven web) A first spunbond nonwoven web was formed in the same manner as in Example 1, except that a polypropylene resin consisting of a homopolymer having an MFR of 200 g / 10 min and a melting point of 163° C. was fed to the extruder.

[0109] (meltblown nonwoven web) A meltblown nonwoven web was formed in the same manner as in Example 1 on the first spunbond nonwoven web.

[0110] (Second spunbond nonwoven web) A second spunbond nonwoven web was formed on the meltblown nonwoven web under the same conditions as for the first spunbond nonwoven web, and the total basis weight was 75 g / m. 2 A laminated fiber web of 1000 .mu.m was obtained.

[0111] (Laminated nonwoven fabric) The laminated fiber web was subjected to preheating and heat fusion bonding in the same manner as in Example 1, except that the preheating temperature was 30° C. and the heat bonding temperature was 170° C., and an attempt was made to produce a laminated nonwoven fabric. However, due to breakage of the laminated nonwoven fabric, it was not possible to collect a sample.

[0112] [Table 1]

[0113] As shown in Table 1, the laminated nonwoven fabrics of Examples 1 to 4 had sufficient surface smoothness and softness. On the other hand, the laminated nonwoven fabrics of Comparative Examples 1 and 2 did not have sufficient surface smoothness or softness.

Claims

1. A laminated nonwoven fabric comprising at least one spunbonded nonwoven fabric layer and at least one meltblown nonwoven fabric layer, the at least one spunbonded nonwoven fabric layer and the at least one meltblown nonwoven fabric layer are both composed of fibers made of a polypropylene-based resin composition mainly containing a polypropylene-based resin, The basis weight of the laminated nonwoven fabric is 30 g / m ２ 90g / m or more ２ The number of yarns per unit cross-sectional area of ​​the laminated nonwoven fabric is y (yarns / mm ２ ), the basis weight of the laminated nonwoven fabric is x (g / m ２ ) a laminated nonwoven fabric that satisfies the following relational expression: 0≦a≦600 Here, a = y - 10.7x

2. 2. The laminated nonwoven fabric according to claim 1, wherein the average surface roughness of at least one of the laminated nonwoven fabrics is 1.0 μm or more and 10.0 μm or less.

3. The apparent density of the laminated nonwoven fabric is 0.30 g / cm ３ 0.60g / cm or more ３ The laminated nonwoven fabric according to claim 1 or 2, wherein:

4. The tensile strength and elongation product per unit area of ​​the laminated nonwoven fabric, calculated by the following formula, is 0.05 (N / 50 mm) / (g / m ２ ) or more 0.50 (N / 50mm) / (g / m ２ 3. The laminated nonwoven fabric according to claim 1 or 2, wherein the thickness is 1 / 2 mm or less. Tensile strength and elongation product per unit area ((N / 50 mm) / (g / m ２ )) = [average value of maximum strength (N / 50mm)] x [average value of elongation at maximum strength (-)] / basis weight (g / m ２ )

5. The laminated nonwoven fabric according to claim 1 or 2, wherein the polypropylene-based resin composition contains a low-crystalline polyolefin-based resin.

6. The laminated nonwoven fabric according to claim 5 , wherein the content of the low-crystalline polyolefin resin in the polypropylene resin composition is 1% by mass or more and 20% by mass or less.

7. 6. The laminated nonwoven fabric according to claim 5, wherein the low-crystalline polyolefin resin is an ethylene-propylene copolymer.

8. 3. A method for producing the laminated nonwoven fabric according to claim 1, comprising the steps of: forming at least one layer of a first spunbonded nonwoven web; forming at least one layer of a meltblown nonwoven web on the at least one layer of the first spunbonded nonwoven web; forming at least one layer of a second spunbonded nonwoven web on the at least one layer of the meltblown nonwoven web to form a laminated web; preheating the laminated web by contacting only one surface of the laminated web with the heating surface of a heating device to obtain a preheated laminated web; and fusing the preheated laminated web using a heat calender roll consisting of a pair of upper and lower flat rolls to form a laminated nonwoven fabric, wherein the preheating temperature in the step of obtaining the preheated laminated web is 40°C or higher and 95°C or lower.

9. A label comprising the laminated nonwoven fabric according to claim 1 or 2.

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