Long-fiber non-woven fabric, method for producing same, and sanitary material

Abstract

A long-fiber non-woven fabric comprising a composite fiber that contains a first component that is a polyester resin and a second component that is a polyolefin resin, the long-fiber non-woven fabric being obtained by crimping the composite fiber, the number of bonding points of the composite fibers per unit area on one surface of the long-fiber nonwoven fabric and the number of bonding points of the composite fibers per unit area on the other surface of the long-fiber nonwoven fabric are both 20 / mm2 or more and 60 / mm2 or less, and the fiber density of the long-fiber nonwoven fabric is 0.010 g / cm < 3 > or more and 0.050 g / cm < 3 > or less. The present invention provides a long-fiber non-woven fabric which is used as a non-woven fabric for hygienic materials that is used on the surface of the hygienic materials that is in contact with the skin, and which has excellent cushioning properties and excellent flexibility in both the front and back surfaces.

Description

Technical Field

[0001] The present invention relates to a long-fiber nonwoven fabric having excellent cushioning properties and softness and suitable for use as a sanitary material, a method for producing the same, and a sanitary material. Background Art

[0002] As disposable diapers, sanitary napkins, masks and other sanitary materials have become more and more popular around the world, the performance and quality requirements of the components used have become increasingly higher in recent years. In particular, for components such as diaper top sheets that come into direct contact with the user's skin, in order to improve the comfort when wearing, they are required to have softness or fluffiness while not being easily crushed by compression, that is, cushioning properties.

[0003] Previously, so-called air-through nonwoven fabrics were used for this type of area. Air-through nonwoven fabrics are made by combing short fibers into thin sheets and then self-melting them through hot air treatment. Air-through nonwoven fabrics are widely used because they have excellent softness and cushioning properties, but because they are a structure in which short fibers are thermally bonded at the intersections, the mechanical properties of the nonwoven fabric are low, making it difficult to achieve low unit weight or high-speed production.

[0004] On the other hand, in long-fiber nonwoven fabrics produced by spunbonding or the like, since the fibers are continuous, a large number of fibers may affect the strength of the nonwoven fabric via bonding points. Therefore, although the strength is expected to be improved, the bulkiness is insufficient.

[0005] To address the above problems, Patent Document 1 proposes a spunbonded nonwoven fabric including long fibers made of two different polymers having melting temperatures of 30° C. or higher and having a fiber density within a specific range.

[0006] In addition, in Patent Document 2 or Patent Document 3, a composite long-fiber nonwoven fabric is proposed, wherein the composite long-fiber nonwoven fabric contains a polypropylene resin as a first component and a polyethylene resin as a second component, and in the composite long-fiber nonwoven fabric, the bonding points of the fibers in the nonwoven fabric and the distances between the bonding points are controlled within a specific range.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: International Publication No. 2021 / 010357

[0010] Patent Document 2: Japanese Patent Application Publication No. 2019-85661

[0011] Patent Document 3: Japanese Patent Application Publication No. 2016-041858 Summary of the invention

[0012] Problems to be solved by the invention

[0013] In the technology of Patent Document 1, the bulkiness of the nonwoven fabric is improved by bonding a nonwoven fiber web containing long fibers of a specific polymer combination using hot air. However, in the technology, in the bonding process of the nonwoven fabric, the degree of bonding is different between the surface exposed to the hot air and the surface not exposed to the hot air, and in the obtained nonwoven fabric, due to the difference in bonding, the difference in softness sometimes occurs between the surface and the back. In this way, when a raw material having a difference in softness between the surface and the back is used, for example, for sanitary materials, the nonwoven fabric cannot deform to follow the deformation of the sanitary material caused by the user's movements due to the surface with low softness, which may impair wearing comfort.

[0014] On the other hand, in the technology of Patent Document 2 or Patent Document 3, bulkiness is obtained by bonding a nonwoven web including composite long fibers containing polypropylene and polyethylene using hot air. However, since polypropylene or polyethylene has low rigidity, even if the nonwoven web has bulkiness, it will be easily crushed by compression, and there is a problem in terms of cushioning properties.

[0015] Therefore, in view of the above circumstances, an object of the present invention is to provide a long-fiber nonwoven fabric having excellent cushioning properties and excellent softness on both the front and back sides, which can be used as a nonwoven fabric for sanitary materials used on the surface in contact with the skin of sanitary materials.

[0016] Technical means of solving problems

[0017] The present invention has the following structure.

[0018] [1] A long fiber nonwoven fabric comprising a composite fiber comprising a first component being a polyester resin and a second component being a polyolefin resin, wherein the long fiber nonwoven fabric is formed by crimping the composite fiber, and the number of bonding points of the composite fiber per unit area on one surface of the long fiber nonwoven fabric and the number of bonding points of the composite fiber per unit area on the other surface of the long fiber nonwoven fabric are both 20 / mm 2 Above and 60 pieces / mm 2 The fiber density of the long fiber nonwoven fabric is 0.010 g / cm 3 Above and 0.050 g / cm 3 the following.

[0019] [2] The long-fiber nonwoven fabric according to [1], wherein the conjugate fibers are side-by-side conjugate fibers.

[0020] [3] The long-fiber nonwoven fabric according to [1] or [2], wherein in the cross section of the conjugate fiber, the area ratio of the second component is 50% or more and 90% or less.

[0021] [4] The long fiber nonwoven fabric according to any one of [1] to [3], wherein one of the surfaces of the long fiber nonwoven fabric is taken as the upper surface and the average length L of the long fiber nonwoven fabric protruding toward the inclined surface of the cantilever test machine is A (cm), and the average length L of the long-fiber nonwoven fabric protruding toward the inclined surface of the cantilever tester with the other surface as the upper surface. B The relationship between (cm) satisfies the following formula (1).

[0022]

[0023] [5] A sanitary material, at least a portion of which comprises the long-fiber nonwoven fabric according to any one of [1] to [4].

[0024] [6] The sanitary material according to [5], wherein the sanitary material is a diaper.

[0025] [7] The sanitary material according to [6], wherein the long-fiber nonwoven fabric is included in a top sheet.

[0026] [8] A method for producing a long fiber nonwoven fabric according to any one of [1] to [4], wherein the first component and the second component are melted separately and supplied to a composite spinning die, a composite polymer flow is ejected from an ejection hole of the composite spinning die, and composite fibers are spun.

[0027] The composite fibers were collected on a belt to form a fiber density of 0.010 g / cm 3 Above and 0.050 g / cm 3 The following network,

[0028] When the melting point of the second component is Tm2 (° C.), the net is blown at a wind speed of 1.0 m / sec or more and 13.0 m / sec or less. Above and The gas is sucked toward the bottom of the belt at a wind speed of not less than 1.0 m / sec and not more than 13.0 m / sec.

[0029] [9] The method for producing a long-fiber nonwoven fabric according to [8], wherein the conjugate fibers are side-by-side conjugate fibers.

[0030]

[10] The method for producing a long-fiber nonwoven fabric according to [8] or [9], wherein the mass ratio of the second component in the composite polymer flow is 50 mass % or more and 95 mass % or less.

[0031] Effects of the Invention

[0032] According to the present invention, a long-fiber nonwoven fabric having excellent cushioning properties and excellent softness on both the front and back surfaces can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] [ Figure 1 ] is a schematic diagram showing an example of an eccentric core-sheath type composite cross-section in which the center of gravity of the second component (2) as the core is located at a position different from the center of gravity of the first component (1) as the sheath and the second component is a half-moon shape. DETAILED DESCRIPTION

[0034] The present invention is a long fiber nonwoven fabric comprising composite fibers comprising a first component of a polyester resin and a second component of a polyolefin resin, wherein the long fiber nonwoven fabric is formed by curling the composite fibers, and the number of bonding points of the composite fibers per unit area on one surface of the long fiber nonwoven fabric and the number of bonding points of the composite fibers per unit area on the other surface of the long fiber nonwoven fabric are both 20 / mm 2 Above and 60 pieces / mm 2 The fiber density of the long fiber nonwoven fabric is 0.010 g / cm 3 Above and 0.050 g / cm 3 the following.

[0035] Hereinafter, the constituent elements will be described in detail, but the present invention is not limited in any way to the scope of the following description unless the gist of the present invention is exceeded.

[0036] [Composite Fiber]

[0037] The conjugate fiber of the long-fiber nonwoven fabric of the present invention contains a first component which is a polyester-based resin and a second component which is a polyolefin-based resin.

[0038] Examples of the polyester resin include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, polylactic acid, and polyester elastomers. Of these, polyethylene terephthalate and polybutylene terephthalate are more preferably used, and polyethylene terephthalate is particularly preferably used, from the viewpoint of increasing the rigidity of the composite fiber and improving the cushioning properties of the nonwoven fabric.

[0039] The polyester resin may contain a copolymer component according to various purposes within a range that does not hinder the purpose of the present invention.

[0040] Furthermore, the polyester resin may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, etc. according to various purposes within the range not hindering the purpose of the present invention.

[0041] Examples of the polyolefin resin include polypropylene, polyethylene, polybutene, polymethylpentene, etc. Among these, polypropylene and polyethylene are particularly preferably used from the viewpoint of improving the adhesion between fibers and improving the mechanical properties of the nonwoven fabric.

[0042] The polyolefin resin can be copolymerized with α-olefins such as ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, and 4-methyl-1-hexene according to various purposes within the range not hindering the purpose of the present invention.

[0043] Furthermore, the polyolefin-based resin may be blended with other polyolefin-based resins according to various purposes within a range that does not hinder the purpose of the present invention.

[0044] Furthermore, the polyolefin resin may contain inorganic particles such as titanium oxide particles, lubricants, pigments, heat stabilizers, ultraviolet absorbers, conductive agents, heat storage agents, antibacterial agents, etc. according to various purposes within a range not hindering the purpose of the present invention.

[0045] The composite fiber of the long fiber nonwoven fabric of the present invention contains the first component which is a polyester resin as described above and the second component which is a polyolefin resin as described above, and has moderately high rigidity and is easily bonded by heat, so that it can exhibit good cushioning properties when made into a nonwoven fabric.

[0046] The composite fiber of the long fiber nonwoven fabric of the present invention preferably has an area ratio of the second component of 50% or more and 90% or less. By making the area ratio of the second component as a polyolefin resin within the above range, the high rigidity of the first component as a polyester resin can be effectively utilized while fully ensuring the adhesion between the fibers, and when the nonwoven fabric is made, the cushioning property can be improved. From this point of view, the area ratio of the second component is more preferably 50% or more and 80% or less.

[0047] The area ratio of the second component mentioned here is calculated as follows.

[0048] A single fiber is cut out from a long-fiber nonwoven fabric, embedded, and sliced ​​using a microtome so that the cross section of the single fiber can be observed, and then placed on a glass slide. Then, a microscope built into a Raman spectrometer ("inVia" manufactured by Renishaw) with a 100x objective lens is used to observe the fiber cross section, and microscopic Raman spectrometry is performed on the two components that constitute the fiber cross section. By comparing the obtained Raman spectrum with the Raman spectrum of the polyolefin resin constituting the second component measured in advance, the component with the same spectrum is identified as the second component. In the case where the polyolefin resin constituting the second component cannot be obtained in advance, the "Spectral Database of Organic Compounds SDBS (Spectral Data Base System)" disclosed by the National Research and Development Corporation Advanced Industrial Science and Technology is used to identify the second component.

[0049] Then, the slice used in the measurement was imaged at a magnification that allowed observation of the cross section of a single fiber using a digital microscope ("VHX6000" manufactured by Keyence Co., Ltd.). Based on the image captured by a scanning electron microscope (SEM), the cross-sectional area (Af) of the fiber and the area (A2) of the second component were measured using image analysis software ("WinROOF2015" manufactured by Mitani Shoji Co., Ltd.), and the area ratio of the second component was calculated using the following formula (2).

[0050]

[0051] The simple numerical average of the results of the same operation on 20 different conjugate fibers was calculated, and the value after rounding off to the first decimal place was used as the area ratio of the second component in the present invention.

[0052] The conjugate fibers of the long fiber nonwoven fabric of the present invention have a certain amount of crimp. Examples of such crimped conjugate fibers include side-by-side conjugate fibers and eccentric core-sheath conjugate fibers.

[0053] In these composite fibers, the center of gravity of each component is separated in the cross section of the single fiber, so when the self-tension is released in the spinning process, the fiber will bend according to the difference in elastic recovery of each component, and it will be continuous in the fiber axis, thus showing curl. By having such curl, the single fibers repel each other, so the fluffiness of the nonwoven fabric can be improved.

[0054] In the long fiber nonwoven fabric of the present invention, from the viewpoint of developing fine crimps in the fibers and improving bulkiness and softness, side-by-side conjugate fibers are preferred, which can set a large distance between the centers of gravity of the left and right crimps.

[0055] The cross-sectional shape of the conjugate fiber of the present invention is not particularly limited unless the effects of the present invention are impaired, and may be a circular cross-sectional shape or may be a triangular, flat, hexagonal, hollow or other irregular cross-sectional shape.

[0056] The single fiber diameter of the composite fiber of the present invention is preferably 3.0 μm to 30.0 μm. The single fiber diameter of the composite fiber is preferably 3.0 μm or more, more preferably 5.0 μm or more, and further preferably 7.5 μm or more. By setting the single fiber diameter of the composite fiber to 3.0 μm or more, it is not easy to collapse even if a load is applied when the nonwoven fabric is made, and excellent cushioning properties can be formed. In addition, the single fiber diameter of the composite fiber is preferably 30.0 μm or less, more preferably 25.0 μm or less, and particularly preferably 20.0 μm or less. By setting the single fiber diameter of the composite fiber to 30.0 μm or less, a soft feel is easily obtained.

[0057] The single fiber diameter (D) in the present invention is determined as follows.

[0058] First, a slice of a single fiber cross section was prepared in the same manner as the method for measuring the area ratio of the second component, and an image was taken at a magnification that allowed observation of one single fiber. The imaged fiber cross section image was used to measure the area Af (μm) formed by the cross-sectional profile of the single fiber using image analysis software ("WinROOF2015" manufactured by Mitani Shoji Co., Ltd.). 2 ), calculate the diameter of a perfect circle having the same area as the area Af. The diameter is measured for 20 single fibers randomly extracted from the long-fiber nonwoven fabric, and the simple number average is calculated. The unit is set to μm, and the value after rounding off the second decimal place is taken as the single fiber diameter (D).

[0059] [Long fiber nonwoven fabric]

[0060] Furthermore, the long-fiber nonwoven fabric of the present invention is a nonwoven fabric containing long fibers. By containing the long fibers, sufficient mechanical properties can be obtained in terms of low unit weight or high-speed production.

[0061] In addition, the fiber density of the long fiber nonwoven fabric of the present invention is 0.010 g / cm 3 Above and 0.050 g / cm 3 the following.

[0062] The fiber density mentioned here is calculated|required as follows.

[0063] First, the weight per unit area (W) of the long-fiber nonwoven fabric was measured based on "6.2 Mass per unit area" of "Test methods for ordinary nonwoven fabrics" in Japanese Industrial Standards (JIS) L 1913:2010.

[0064] Next, the thickness (H) of the long-fiber nonwoven fabric was determined as follows.

[0065] A 25 mm × 40 mm test piece was collected from the long-fiber nonwoven fabric and placed on the measuring table of a three-dimensional (3D) microscope (one shot 3D shape measuring machine manufactured by Keyence Co., Ltd.: head "VR-3050", controller "VR-3000") without applying a load to the test piece. The thickness was measured in μm at any 8 points of the sample. The average value of the measured values ​​was rounded off to the first decimal place in μm as the thickness (H) of the long-fiber nonwoven fabric.

[0066] The weight per unit area W (g / m 2 ) divided by the thickness H (μm) of the long-fiber nonwoven fabric, with the fourth decimal place rounded off, is the fiber density referred to in the present invention.

[0067] If the fiber density is within the above range, the bulkiness of the long fiber nonwoven fabric is sufficiently low, and the softness can be improved. More preferably, it is 0.010 g / cm 3 Above and 0.040 g / cm 3 Below, more preferably 0.010 g / cm 3 Above and 0.030g / cm 3 the following.

[0068] Furthermore, the fiber density of the long-fiber nonwoven fabric of the present invention can be controlled by changing the degree of crimping according to the area ratio of the second component or the cross-sectional shape of the single fiber.

[0069] In the long fiber nonwoven fabric of the present invention, the number of bonding points of the composite fibers per unit area on one surface and the number of bonding points of the composite fibers per unit area on the other surface are both 20 / mm 2 Above and 60 pieces / mm 2 the following.

[0070] The number of bonding points on one surface and the number of bonding points on the other surface mentioned here are calculated|required as follows.

[0071] First, one surface of the long-fiber nonwoven fabric is set as surface A, and the other surface is set as surface B.

[0072] Next, 10 test pieces with a size of 10 mm in the machine direction (MD (Machine Direction) direction) and 10 mm in the direction perpendicular to the machine direction (cross direction (CD) direction) were collected from the long-fiber nonwoven fabric. In order to know the positional relationship between surface A and surface B, the collected test pieces were placed still under a digital microscope ("VHX6000" manufactured by Keyence Co., Ltd.), and the cross-section of the long-fiber nonwoven fabric in the CD direction was imaged at a magnification that allowed the thickness direction to enter the entire field of view. In the cross-sectional image of the long-fiber nonwoven fabric captured, the following areas M and N were set.

[0073] Region M: A rectangular region of 1,000 μm in the CD direction and 25% (H×0.25 (μm)) of the thickness in the thickness direction from the end portion on the surface A side determined by the above method.

[0074] Region N: A rectangular region of 1,000 μm in the CD direction and 25% (H×0.25 (μm)) of the thickness in the thickness direction from the end portion on the surface B side determined by the above method.

[0075] Next, the number of bonding points of the composite fibers observed in the regions M and N was measured using image analysis software ("WinROOF2015" manufactured by Mitani Shoji Co., Ltd.). This operation was performed on 10 test pieces, and the simple number average was calculated. The number of bonding points was converted into the average value per unit area (1 mm2). 2 ) is rounded to the first decimal place. The area M per unit area (1 mm 2 ) is the number of bonding points of the composite fiber per unit area on one surface described in the present invention, and the number of bonding points of the composite fiber per unit area (1 mm 2 ) is the number of bonding points of the composite fiber per unit area on the other surface described in the present invention.

[0076] The bonding point referred to here refers to a portion where the outer shape of the conjugate fibers is deformed near the intersection among the portions where the conjugate fibers intersect each other.

[0077] In the long fiber nonwoven fabric of the present invention, if the number of bonding points of the composite fibers per unit area on both surfaces is within the above range, the fabric has high mechanical properties and excellent softness through a moderate bonding density. Preferably, the number of bonding points of the composite fibers per unit area on one surface and the number of bonding points of the composite fibers per unit area on the other surface are both 25 / mm 2 Above and 55 pieces / mm 2 the following.

[0078] In addition, regarding the number of bonding points of the composite fibers per unit area on the surface of the long-fiber nonwoven fabric of the present invention, when heated gas is used for bonding the fibers to each other, it can be controlled by the temperature at which the fibers are bonded and the wind speed of the gas blown, etc. In addition, in order to closely control the number of bonding points on each surface, it is necessary to make the fibers bond to each other appropriately while the hot air passes evenly through the inside of the nonwoven fabric, so it is necessary to control the temperature of the gas in the bonding process and the blowing wind speed, as well as the wind speed sucked to the bottom of the long-fiber nonwoven fabric within an appropriate range.

[0079] In the long-fiber nonwoven fabric of the present invention, the difference between the number of bonding points of the composite fibers per unit area on one surface and the number of bonding points of the composite fibers per unit area on the other surface is preferably 20 / mm. 2 the following.

[0080] The difference between the number of bonding points of the composite fibers per unit area on one surface and the number of bonding points of the composite fibers per unit area on the other surface mentioned here refers to the absolute value of the difference between the number of bonding points of the composite fibers per unit area on each surface measured by the above method.

[0081] By setting the difference in the number of bonding points of the composite fibers per unit area on each surface of the long-fiber nonwoven fabric to the above preferred range, the softness of both surfaces of the nonwoven fabric can be controlled to be the same. From this point of view, it is preferred that the difference between the number of bonding points of the composite fibers per unit area on one surface and the number of bonding points of the composite fibers per unit area on the other surface is 15 pieces / mm 2 the following.

[0082] In this way, the long-fiber nonwoven fabric of the present invention has a small difference in the number of bonding points of the composite fibers per unit area on each surface, and the softness of both sides is controlled to the same degree. Therefore, when it is made into a sanitary material, the nonwoven fabric can deform following the deformation of the sanitary material caused by the wearer's movements, and the softness can be felt when worn.

[0083] Therefore, the long-fiber nonwoven fabric of the present invention is preferably an average value L of the length of the long-fiber nonwoven fabric protruding toward the inclined surface of the cantilever tester with one surface as the upper surface. A (cm), and the average length L of the long-fiber nonwoven fabric protruding toward the inclined surface of the cantilever tester with the other surface as the upper surface. B The relationship between (cm) satisfies the following formula (1).

[0084]

[0085] The L mentioned here A and L B Hereinafter, it may be referred to as the cantilever measurement length, and specifically, it is a value measured by the following procedure.

[0086] Procedure 1: Randomly collect 6 test pieces from the long-fiber nonwoven fabric, each with a width of 25 mm in the machine direction (MD direction) and a width of 250 mm in the direction perpendicular to the machine direction (CD direction).

[0087] Process 2: Based on "6.2 Mass per unit area" of JIS L 1913:2010 "Test methods for ordinary nonwoven fabrics", in g / m 2 The weight per unit area M of the test piece collected for unit measurement is calculated by rounding off the second decimal place.

[0088] Process 3: Place the 41.5° cantilever tester used in "6.7.3 41.5° cantilever method" of JIS L 1913:2010 "Test methods for ordinary nonwoven fabrics" on a horizontal table with one surface A facing downward, and align one end of the test piece with the front end of the table.

[0089] Process 4: A steel scale is placed on the test piece with its 0 point aligned with the mark D engraved on the upper surface of the cantilever type testing machine.

[0090] Process 5: Push the ruler and the test piece slowly along the slope at a constant speed.

[0091] Procedure 6: Move the steel ruler until the test piece contacts the inclined surface of the cantilever tester. After leaving it for 8 seconds, read the length of the steel ruler protruding to the depth of the test piece in units of 1 mm at most.

[0092] Process 7: Repeat process 2 to process 6 for the collected 6 test pieces, and calculate the average length of the protrusion to the depth of the 6 test pieces, which is set as L A (cm).

[0093] Process 8: The six test pieces collected in process 1 are placed with the surface B facing downward, unlike process 3. The average length of the protrusion to the depth of the six test pieces is calculated in the same manner as processes 4 to 7, and is set as L B (cm).

[0094] If the cantilever measurement length L on each surface A With cantilever measurement length L B If the relationship between L and φ satisfies equation (1), it means that the softness of the long-fiber nonwoven fabric is the same on all surfaces. When it is made into a sanitary material, the nonwoven fabric can follow the deformation of the sanitary material caused by the wearer's movements and can also feel soft when worn. From this point of view, the L A With L B The absolute value of the difference The smaller the better, preferably set to , more preferably set to .

[0095] In addition, in the long-fiber nonwoven fabric of the present invention, when the fibers are bonded together, when heated gas is used for bonding the fibers together, the above-mentioned formula (1) can be satisfied by controlling the temperature at which the fibers are bonded together, and the balance between the wind speed of the gas blown and the wind speed sucked under the nonwoven fabric.

[0096] In addition, the weight per unit area of ​​the long-fiber nonwoven fabric of the present invention is preferably set to 5 g / m 2 ~100 g / m 2 By setting the unit area weight to preferably 5 g / m 2 More preferably 8 g / m 2 More preferably, 10 g / m 2 On the other hand, by setting the weight per unit area to preferably 100 g / m 2 Less than, more preferably 50 g / m 2 In the following, a long-fiber nonwoven fabric having appropriate softness suitable for use as a nonwoven fabric for sanitary materials can be produced.

[0097] The long-fiber nonwoven fabric of the present invention preferably has an average bending rigidity per unit length of one surface Ba (gf·cm 2 / cm) and the average value of the bending rigidity per unit length of the other surface Bb (gf·cm 2 / cm) satisfies the following formula (3).

[0098]

[0099] Ba and Bb mentioned here are values ​​measured according to the following flow.

[0100] Procedure 1: Collect 6 test pieces from a long-fiber nonwoven fabric, each of which is 200 mm in the machine direction (MD direction) and 100 mm in the direction perpendicular to the machine direction (CD direction).

[0101] Process 2: The test piece was mounted on the chucks of a pure bending tester ("KES-FB2" manufactured by Kato-tech Co., Ltd.) so that the distance between the chucks was 10 mm. At this time, the MD direction of the test piece was the bending direction, and one surface A was facing the left side when viewed from the observer.

[0102] Process 3: According to the method described on pages 27-28 of "Standardization and Analysis of Hand Feel Evaluation (2nd Edition)" (author: Kawabata Yoshio, publisher: Japan Textile Machinery Society, Hand Feel Measurement and Standardization Research Committee, published on July 10, 1980), Pure bending with constant curvature is performed within the range of . The deformation speed is set to 0.50 cm -1 / sec.

[0103] Process 4: Through the operation of process 3, the relationship between the bending moment M and the curvature K per unit area of ​​the test piece (MK curve) is obtained.

[0104] Process 5: Repeat process 2 to process 4 for the 6 test pieces collected to calculate the MK curve. and The average value of the slope of the increase process of the absolute value of K between the two values, rounded to the fourth decimal place, is denoted as Ba (gf cm 2 / cm).

[0105] Process 6: Repeat process 2 to process 4 for the 6 test pieces collected to calculate the MK curve and The average value of the slope of the increase in the absolute value of K between the two values, rounded to the fourth decimal place, is denoted as Bb (gf cm 2 / cm).

[0106] In addition, 1 gf·cm 2 / cm is 9.807×10 -3 N cm 2 / cm, so if we use Ba (gf cm 2 / cm)、Bb(gf·cm 2 / cm) and Ba' (N·cm 2 / cm)、Bb'(N·cm2 / cm) to represent the above formula (3), it can be represented by the following formula (3').

[0107]

[0108] The difference in softness between the front and back surfaces of the long-fiber nonwoven fabric of the present invention is preferably 3.5 or more based on the criteria described below.

[0109] The difference in flexibility between the front and back sides mentioned here was evaluated based on the following criteria.

[0110] Ten randomly selected healthy adults evaluated the softness of the front and back surfaces of the long-fiber nonwoven fabrics according to the following procedure and the following criteria. The average score of the evaluation results for each nonwoven fabric was taken as the difference in softness between the front and back surfaces of the nonwoven fabric.

[0111] Procedure 1: Place the long-fiber nonwoven fabric with surface A facing upward on a table, pinch it with your index finger, middle finger and thumb, and judge its softness.

[0112] Procedure 2: Place the same sample as in Procedure 1 on a table with surface B facing upward, pinch it with the index finger, middle finger and thumb, and judge its softness.

[0113] Process 3: The difference in softness between the front and back of the long-fiber nonwoven fabric was evaluated according to the following criteria.

[0114] 5: Both sides are soft and you can hardly feel the difference.

[0115] 4: Both sides are soft, but the difference in softness is clearly felt on the other side.

[0116] ·3: One side is soft, but the other side is less soft.

[0117] ·2: One side is soft, but the other side is not soft.

[0118] 1: Both sides are not soft.

[0119] [Sanitary materials]

[0120] At least a part of the sanitary material of the present invention comprises the long-fiber nonwoven fabric, and excellent cushioning and softness can be obtained. In addition, the sanitary material of the present invention is mainly a disposable article used for health-related purposes such as medical treatment and nursing, and can be listed as diapers, sanitary napkins, gauze, bandages, masks, gloves, band-aids, etc., and its constituent members also include, for example, the top sheet, bottom sheet, side pleats, etc. of diapers.

[0121] A first preferred embodiment is a diaper in which the top sheet includes the long-fiber nonwoven fabric.

[0122] [Manufacturing method of long fiber nonwoven fabric]

[0123] Next, a preferred embodiment of producing the long-fiber nonwoven fabric of the present invention will be described in detail.

[0124] The method for producing a long fiber nonwoven fabric of the present invention is preferably a method comprising the following steps: melting the first component containing a polyester resin and the second component containing a polyolefin resin respectively and supplying them to a composite spinning die, ejecting a composite polymer flow from an ejection hole of the composite spinning die, spinning composite fibers, capturing the composite fibers on a belt to form a web having a fiber density of 0.010 g / cm3 or more and 0.050 g / cm3 or less, and blowing the web at a wind speed of 1.0 m / sec or more and 13.0 m / sec or less when the melting point of the second component is set to Tm2 (°C). Above and The gas is sucked toward the bottom of the belt at a wind speed of 1.0 m / sec to 12.0 m / sec.

[0125] As a suitable composite spinning die used in the method for manufacturing the long fiber nonwoven fabric of the present invention, it is preferred that a mechanism that can form a parallel composite cross section or an eccentric core-sheath composite cross section is included, and it is particularly preferred that a mechanism that can form a parallel composite cross section is included. In addition, as long as the effect of the present invention is not impaired, the shape of the ejection hole of the die can be freely selected, and from the perspective of spinning stability, it is preferably set as a circular hole.

[0126] In addition, when the melting temperature of the first component and the second component having a higher melting temperature is set to Tm (° C.), the spinning temperature in the present invention is preferably set to ( ) or more and ( By setting the spinning temperature within the above range, a stable molten state can be formed, thereby obtaining excellent spinning stability.

[0127] In the method for manufacturing a long fiber nonwoven fabric of the present invention, it is preferred to use an air traction unit such as an ejector to traction and stretch the fibers obtained by cooling and solidifying the composite fibers ejected from the composite spinning die, and capture them on a capture belt to form a web. By traction and stretching the fibers by the air traction unit, a difference in elastic recovery is generated between the first component and the second component in the fiber forming process, so that the composite fibers can appropriately show curling. As a result, good bulkiness can be obtained in the web in which the composite fibers are captured on the belt. Furthermore, by traction and stretching the fibers by the air traction unit, the strength of the single fiber is improved, thereby also making the mechanical properties good.

[0128] From the viewpoint of making the composite fiber appropriately crimped, in the method for producing the long fiber nonwoven fabric of the present invention, the spinning speed is preferably high, preferably 2,000 m / min or more. More preferably, it is 2,500 m / min or more, and particularly preferably 3,000 m / min or more. In addition, by setting the spinning speed to 2,000 m / min or more, the fiber can be oriented and crystallized, thereby obtaining a fiber with higher strength, and high productivity can also be ensured.

[0129] In addition, in the method for manufacturing a long fiber nonwoven fabric of the present invention, from the perspective of improving the bulkiness of the web that captures the composite fiber on the belt, it is preferred to eject the composite polymer flow in the form of a composite polymer flow in which the mass ratio of the second component in the composite polymer flow is 50% by mass or more and 95% by mass or less. By controlling the mass ratio of the second component in the composite polymer flow within the range, the difference in elastic recovery between the first component and the second component is enlarged and the curling is promoted, while the high rigidity of the first component is also effectively utilized, thereby collecting a web with high cushioning properties. As a result, the web is not easily compressed in the subsequent connecting process, so a long fiber nonwoven fabric with high cushioning properties can be obtained. Therefore, from the perspective of improving the rigidity of the composite fiber and improving the cushioning properties of the web and the obtained long fiber nonwoven fabric, it is preferred to eject the composite polymer flow in a mass ratio of 50% by mass or more and 90% by mass or less. Furthermore, by ejecting the composite polymer flow in a mass ratio of 50% by mass or more and 80% by mass or less, the stability of ejection and yarn making can be improved, so it is more preferred.

[0130] In the method for producing a long-fiber nonwoven fabric of the present invention, it is preferred to arbitrarily change the ejection amount per ejection hole of the die according to a desired fiber diameter.

[0131] In the method for producing a long fiber nonwoven fabric of the present invention, it is preferred that the composite fiber produced as described above be spunbonded to a fiber density of 0.010 g / cm 3 Above and 0.050 g / cm 3 The following method is used to capture the particles on the belt.

[0132] The fiber density referred to here is the fiber density obtained by collecting the web captured on the belt before heat bonding in the process and measuring it by the above-mentioned method.

[0133] In the method for producing a long-fiber nonwoven fabric of the present invention, the fiber density is set to 0.010 g / cm 3 Above and 0.050 g / cm 3 Next, in the subsequent steps, the gas permeability is improved, and heat bonding can be efficiently performed.

[0134] In the manufacture of the long fiber nonwoven fabric of the present invention, it is preferred to heat-bond the fibers of the web captured on the belt using heated gas. By adopting such a bonding form, the web can be fixed in shape without compressing the web, thereby improving the bulkiness of the obtained long fiber nonwoven fabric.

[0135] From this viewpoint, in the thermal bonding step, it is important to control the process of sucking the gas in addition to controlling the temperature and wind speed of the gas used.

[0136] First, in the method for producing a long-fiber nonwoven fabric of the present invention, when the melting point of the second component is set to Tm2 (° C.), it is preferred that the temperature of the gas used in the thermal bonding is set to Above and the following.

[0137] The melting point Tm2 (° C.) of the second component mentioned here is the peak top temperature (° C.) of the endothermic peak of the polyolefin resin of the second component when measured under a nitrogen atmosphere at a heating rate of 16° C. / min using a differential scanning calorimeter (“DSCQ2000” manufactured by TA Instruments).

[0138] By controlling the temperature of the gas used for heat bonding in the production of the long fiber nonwoven fabric of the present invention within the above range, the composite fibers can be firmly bonded to each other to obtain a high nonwoven fabric strength, and the reduction in the bulkiness and softness of the nonwoven fabric caused by excessive bonding can be suppressed. In addition, from the viewpoint of suppressing the thermal shrinkage of the composite fibers and suppressing the high density caused by the shrinkage of the web, it is more preferable to set the temperature of the gas used for heat bonding to Above and Below. It is further preferred to set Above and the following.

[0139] In addition, any gas may be used as the gas for thermal bonding in the method for producing the long fiber nonwoven fabric of the present invention, but air is preferred from the viewpoint of cost and safety. In addition, heated steam may also be used from the viewpoint of improving the thermal conductivity to the composite fiber.

[0140] Next, in the production of the long-fiber nonwoven fabric of the present invention, it is preferred that a gas for thermal bonding is blown onto the web at a wind speed of 1.0 m / sec or more and 13.0 m / sec or less.

[0141] The blowing air speed mentioned in the present invention refers to the speed of the upper surface of the web on the belt directed vertically downward from the belt.

[0142] By controlling the wind speed of the gas used for thermal bonding in the production of the long fiber nonwoven fabric of the present invention within the above range, thermal bonding can be performed without excessively compressing the web in the thickness direction, thereby improving the bulkiness of the obtained long fiber nonwoven fabric.

[0143] Furthermore, in the production of the long-fiber nonwoven fabric of the present invention, it is preferred that the gas is sucked toward the bottom of the belt at a wind speed of 1.0 m / sec to 13.0 m / sec while blowing the gas onto the web.

[0144] The suction wind speed referred to in the present invention is the speed from directly above the belt toward vertically downward of the belt, and is a measured value measured in a state where gas is not blown from above the belt.

[0145] In the manufacture of the long-fiber nonwoven fabric of the present invention, by blowing gas to the net while sucking the gas within the range below the belt, the gas can pass through the net appropriately, and the difference in adhesion between the surface exposed to the gas and the other surface can be reduced, so that the softness of both surfaces of the obtained long-fiber nonwoven fabric can be improved.

[0146] From this point of view, in the manufacture of the long-fiber nonwoven fabric of the present invention, the relationship between the wind speed of the gas blown to the web and the wind speed of the gas sucked toward the bottom of the belt is important. That is, it is preferred that the absolute value of the difference between the wind speed of the gas blown to the web and the wind speed of the gas sucked toward the bottom of the belt be set to 3.0 m / sec or less.

[0147] By controlling the difference between the blowing wind speed and the suction wind speed within the above range, the heated gas is not easily retained in the net while sufficient bonding is performed without compressing the net, and both sides of the net can be evenly heat-bonded. Furthermore, since the fibers in the net containing long fibers are not entangled with each other, when the difference between the blowing wind speed and the suction wind speed is large, the fibers will shift, thereby damaging the texture, and the fluffiness or strength will be greatly reduced. From this point of view, the wind speed difference is more preferably set to 2.0 m / sec or less.

[0148] Example

[0149] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples. In the long-fiber nonwoven fabric, the machine direction during production is referred to as the MD direction, and the direction orthogonal to the MD direction is referred to as the CD direction.

[0150] [Measurement method]

[0151] The various property values ​​in the examples were measured and evaluated by the following methods. In addition, in the measurement of various physical properties, those not particularly described were measured based on the above methods.

[0152] (1) Melting point of the second component

[0153] The melting point Tm2 of the second component was measured and calculated by the above-mentioned method using “DSCQ2000” manufactured by TA Instruments as a differential scanning calorimeter.

[0154] (2) Fiber density

[0155] The measurement and calculation were performed by the above-mentioned method using a 3D microscope (one shot 3D shape measuring machine manufactured by Keyence Co., Ltd.: head "VR-3050", controller "VR-3000").

[0156] (3) Area ratio of the second component in the composite fiber

[0157] The Raman spectrometer used was "inVia" manufactured by Renishaw, the scanning electron microscope used was "VHX-6000" manufactured by Keyence Co., Ltd., and the image analysis software used was "WinROOF2015" manufactured by Mitani Shoji Co., Ltd. The measurements and calculations were performed according to the above method.

[0158] (4) Number of fiber bonding points per unit area on the fiber surface

[0159] A digital microscope “VHX-6000” manufactured by Keyence Co., Ltd. was used, and an image analysis software “WinROOF 2015” manufactured by Mitani Shoji Co., Ltd. was used, and measurement and calculation were performed according to the above-mentioned method.

[0160] (5) Cantilever measurement length L A , cantilever measurement length L B

[0161] Six test pieces each having a length of 25 mm in the MD direction and 250 mm in the CD direction were randomly collected from the long-fiber nonwoven fabric and measured according to the above method.

[0162] (6) Bending rigidity per unit length Ba, Bending rigidity per unit length Bb

[0163] As a pure bending tester, "KES-FB2" manufactured by Kato-tech Co., Ltd. was used, and the measurement was performed according to the above-mentioned method.

[0164] (7) Buffering

[0165] Ten randomly selected healthy adults pinched the long-fiber nonwoven fabric and compressed it in the thickness direction, and each long-fiber nonwoven fabric was evaluated according to the following criteria: The average score of the evaluation results for each nonwoven fabric was used as the cushioning property of the nonwoven fabric.

[0166] 5: Excellent fluffiness and rebound force.

[0167] ·3: Although fluffy, it is easily crushed by fingers.

[0168] 1: No fluffiness.

[0169] (8) Difference in softness of the case and back

[0170] The difference in softness between the front and back of the long-fiber nonwoven fabric was evaluated according to the above method.

[0171] [Example 1]

[0172] As the first component, polyethylene terephthalate (hereinafter, including Table 1, etc., sometimes referred to as PET) is used, and as the second component, polyethylene (hereinafter, including Table 1, etc., sometimes referred to as PE) is used. These are melted using a separate extruder and ejected from a rectangular die that can obtain a parallel composite cross-section at a spinning temperature of 290°C, with an ejection amount of 0.60 g / min per single hole and an ejection mass ratio of first component: second component = 50:50. After the spun fibers are cooled and solidified, they are pulled and stretched in a rectangular ejector at a spinning speed of 3,321 m / min, and captured on a moving capture belt to obtain a fiber density of 0.015 g / m 3 The fibers in the web were curled. The web obtained in the above manner was heat-bonded by blowing heated air at 200°C from above the web toward the vertically lower side of the belt at a wind speed of 3.6 m / s and sucking the air toward the vertically lower side of the collection belt at a wind speed of 2.2 m / s, thereby obtaining a web with a unit area weight of 35 g / m 2 The results are shown in Table 1.

[0173] [Example 2]

[0174] The composite polymer stream was ejected in the same manner as in Example 1 except that the ejection mass ratio of the first component to the second component was set to first component:second component=25:75, and was pulled and stretched at a spinning speed of 3,321 m / min and captured on a moving capture belt to obtain a fiber density of 0.025 g / m 3The web obtained in the above manner was heat bonded under the same conditions as in Example 1 to obtain a web having a unit area weight of 37 g / m 2 The results are shown in Table 1.

[0175] [Example 3]

[0176] PET was used as the first component and PE was used as the second component. These were melted in a separate extruder and spun at a temperature of 290°C to obtain a filament such as Figure 1 In the rectangular die of the eccentric core-sheath composite cross-section in which the second component as the sheath is a half-moon shape, the first component is used as the core and the second component is used as the sheath, and the ejection amount per single hole is 0.60 g / min, and the ejection mass ratio is 50:50 for the first component: the second component. After the spun fiber is cooled and solidified, it is pulled and stretched in the rectangular ejector at a spinning speed of 3,262 m / min, and captured on a moving capture belt to obtain a fiber density of 0.015 g / m 3 The net obtained in the above manner was heat-bonded by blowing heated air at 200°C from above the net toward the vertically lower side of the belt at a wind speed of 3.6 m / s and sucking the air toward the vertically lower side of the collecting belt at a wind speed of 2.2 m / s, thereby obtaining a net having a unit area weight of 34 g / m 2 The results are shown in Table 1.

[0177] [Example 4]

[0178] The composite polymer stream was ejected in the same manner as in Example 1 except that the ejection mass ratio of the first component to the second component was set to first component:second component=60:40, and was pulled and stretched at a spinning speed of 2,399 m / min and captured on a moving capture belt to obtain a fiber density of 0.017 g / m 3 The web obtained in the above manner was heat-bonded under the same conditions as in Example 1, thereby obtaining a web having a weight per unit area of ​​32 g / m 2 The results are shown in Table 1.

[0179] [Example 5]

[0180] The collected web was blown with heated air at 200°C from above the web toward the vertically lower side of the belt at a wind speed of 4.8 m / sec, and suctioned toward the vertically lower side of the collecting belt at a wind speed of 1.0 m / sec. A 30-meter-high net having a weight per unit area of ​​36 g / cm was obtained in the same manner as in Example 1. 2 The results are shown in Table 1.

[0181] [Comparative Example 1]

[0182] A web having a weight per unit area of ​​33 g / m was obtained in the same manner as in Example 1 except that the web was thermally bonded without suction directed vertically downwardly from the collecting belt. 2 The results are shown in Table 1.

[0183] [Comparative Example 2]

[0184] PET was used as the first component and PE was used as the second component. These were melted in a separate extruder and extruded from a rectangular die that could obtain a core-sheath composite cross-section at a spinning temperature of 290°C, with the first component as the core and the second component as the sheath, at an ejection rate of 0.74 g / min per single hole and an ejection mass ratio of first component: second component = 50:50. After the spun fiber was cooled and solidified, it was pulled and stretched in a rectangular ejector at a spinning speed of 2,696 m / min and captured on a moving capture belt to obtain a fiber density of 0.020 g / m 3 The net obtained in the above manner was heat-bonded by blowing heated air at 200°C from above the net toward the vertically lower side of the belt at a wind speed of 3.6 m / s and sucking the air toward the vertically lower side of the collecting belt at a wind speed of 2.2 m / s, thereby obtaining a net having a unit area weight of 34 g / m 2 The results are shown in Table 1.

[0185] [Comparative Example 3]

[0186] The captured web was blown with heated air at 200°C from above the web toward the vertically lower side of the belt at a wind speed of 15.0 m / sec, and suctioned toward the vertically lower side of the capturing belt at a wind speed of 0.5 m / sec. A web having a weight per unit area of ​​31 g / cm was obtained in the same manner as in Example 1. 2 The results are shown in Table 1.

[0187] [Comparative Example 4]

[0188] The captured web was blown with heated air at 200°C from above the web toward the vertically lower side of the belt at a wind speed of 0.5 m / sec, and suction was conducted toward the vertically lower side of the capturing belt at a wind speed of 15.0 m / sec. A web having a weight per unit area of ​​29 g / cm was obtained in the same manner as in Example 1. 2 The results are shown in Table 1.

[0189] [Table 1]

[0190] [Table 1]

[0191]

[0192] As shown in Table 1, in the long-fiber nonwoven fabrics of Examples 1 to 4, the cushioning property is excellent and the difference in softness between the front and back is small. In particular, for Examples 1, 2 and 4, the cushioning property and softness are both high. In addition, for Example 3, although the softness is inferior to that of Examples 1, 2 and 4 due to the high weight per unit area, the fibers on both sides of the long-fiber nonwoven fabric are compatible with each other, so the cushioning property is particularly excellent while having softness. In addition, for Example 5, since the difference between the wind speed of the heated air and the suction wind speed is greater than that of Examples 1 to 4, the difference in softness between the surface A and the surface B is greater than that of Examples 1 to 4, but it has cushioning property. On the other hand, for Comparative Example 1, since the adhesion of the surface B not exposed to the hot air is low, the softness of the front and back is greatly different. In addition, for Comparative Example 2, the result is that the nonwoven fabric has poor bulkiness and poor cushioning property. In addition, the results of Comparative Example 3 are as follows: since the air heating wind speed is extremely high and the suction wind speed is low, the nonwoven fabric becomes harder and the fibers are more significantly bonded to each other on the surface A strongly exposed to the hot air, while on the other hand, the adhesion becomes lower on the surface B, and a large difference occurs in the softness between the front and back, resulting in poor cushioning. In addition, since the air heating wind speed is low and the suction wind speed is extremely high, the adhesion becomes lower on the surface A, and a large difference occurs in the softness between the front and back.

[0193] Industrial Applicability

[0194] The long-fiber nonwoven fabric of the present invention has excellent cushioning properties and excellent softness on both the front and back sides, and can therefore be used in sanitary materials such as diapers, sanitary napkins, and masks.

[0195] Explanation of symbols

[0196] 1: core

[0197] 2: sheath

Claims

1. A long fiber nonwoven fabric, comprising composite fibers comprising a first component as a polyester resin and a second component as a polyolefin resin, wherein the long fiber nonwoven fabric is formed by curling the composite fibers, and the number of bonding points of the composite fibers per unit area on one surface of the long fiber nonwoven fabric and the number of bonding points of the composite fibers per unit area on the other surface of the long fiber nonwoven fabric are both 20 / mm 2 Above and 60 pieces / mm 2 The fiber density of the long fiber nonwoven fabric is 0.010 g / cm 3 Above and 0.050g / cm 3 the following.

2. The long fiber nonwoven fabric according to claim 1, wherein: The composite fiber is a side-by-side composite fiber.

3. The long fiber nonwoven fabric according to claim 1 or 2, wherein: In the cross section of the conjugate fiber, the area ratio of the second component is 50% or more and 90% or less.

4. The long fiber nonwoven fabric according to claim 1 or 2, wherein: The average length L of the long-fiber nonwoven fabric protruding from the inclined surface of the cantilever tester with one surface of the long-fiber nonwoven fabric as the upper surface A (cm), and the average length L of the long-fiber nonwoven fabric protruding toward the inclined surface of the cantilever tester with the other surface as the upper surface B The relationship between (cm) satisfies the following formula (1). 0≤|L A -L B |≤1.5…(1).

5. A sanitary material, at least a part of which comprises the long-fiber nonwoven fabric according to claim 1 or 2.

6. The sanitary material according to claim 5, wherein The sanitary material is a diaper.

7. The sanitary material according to claim 6, wherein The long-fiber nonwoven fabric is contained in the top sheet.

8. A method for manufacturing a long fiber nonwoven fabric, comprising manufacturing the long fiber nonwoven fabric as claimed in claim 1, wherein the first component and the second component are melted and supplied to a composite spinning die respectively, a composite polymer flow is ejected from an ejection hole of the composite spinning die to spin a composite fiber, The composite fibers were collected on a belt to form a fiber density of 0.010 g / cm 3 Above and 0.050g / cm 3 The following network, When the melting point of the second component is set to Tm2 (°C), a gas with a temperature of Tm2-20°C or higher and Tm2+100°C or lower is blown onto the net at a wind speed of 1.0 m / s or higher and 13.0 m / s or lower, and the gas is sucked toward the bottom of the belt at a wind speed of 1.0 m / s or higher and 13.0 m / s or lower.

9. The method for producing a long-fiber nonwoven fabric according to claim 8, wherein: The composite fiber is a side-by-side composite fiber.

10. The method for producing a long-fiber nonwoven fabric according to claim 8 or 9, wherein: The mass ratio of the second component in the composite polymer flow is 50 mass % or more and 95 mass % or less.

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