Non-woven fabric

Abstract

Provided is a non-woven fabric which is fluffy, has excellent softness, is smooth, and has an excellent fluffy recovery rate. A non-woven fabric having: a first layer containing thermally adhesive composite fibers (1) in which at least some intersection points are thermally adhered; and a second layer containing thermally adhesive composite fibers (2) in which at least a part of intersection points are thermally adhered, in the non-woven fabric, the fiber diameter of the thermally adhesive composite fibers (1) is 5-18 [mu] m, the fiber diameter of the thermally adhesive composite fibers (2) is 12-35 [mu] m, the fiber diameter of the thermally adhesive composite fibers (2) is greater than the fiber diameter of the thermally adhesive composite fibers (1), and the fiber diameter of the thermally adhesive composite fibers (2) is greater than the fiber diameter of the thermally adhesive composite fibers (1). The specific volume of the first layer and the second layer is 150 cm < 3 > / g to 400 cm < 3 > / g.

Description

Technical Field

[0001] This invention relates to a nonwoven fabric that is fluffy, soft, smooth, and has excellent fluffiness recovery rate. Background Technology

[0002] Nonwoven fabrics used in applications such as hygiene products that come into contact with human skin are required to offer higher levels of comfort. Specifically, they need to be highly fluffy or soft, and have minimal roughness (smoothness) due to friction with the skin.

[0003] Most nonwoven fabrics of this type are produced using through-air processing. Through-air nonwoven fabrics are obtained by heat-treating a web comprising composite fibers made of at least two thermoplastic resins with different melting points. Methods for heat-treating the web include, for example, heat-bonding the composite fibers together using a heat treatment apparatus (e.g., a through-air heat treatment machine or a hot air blowing heat treatment machine) that includes a conveying support for supporting and conveying the web. However, since through-air nonwoven fabrics are manufactured by blowing hot air, there is a problem that the pressure from the hot air applies to the web, thereby impairing its bulkiness or softness.

[0004] In view of such problems, the applicant previously proposed that a nonwoven fabric with excellent softness and high strength could be obtained by using superheated steam gas to heat-fuse the intersections of thermally bondable composite fibers under non-pressure conditions (Patent Document 1). However, because the nonwoven fabric obtained in this way is very fluffy, it sometimes collapses due to the winding pressure when it is made into rolls.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2022 / 202142 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] This invention is based on the prior art and aims to provide a nonwoven fabric that is fluffy, soft, smooth, and has excellent fluffiness recovery rate.

[0010] Technical means to solve the problem

[0011] The inventors conducted in-depth research to solve the aforementioned problem. As a result, they discovered that by fabricating a nonwoven fabric having a first layer and a second layer with specific fiber diameters and specific volumes, a nonwoven fabric that is fluffy, soft, smooth, and resistant to collapsing due to winding pressure (excellent fluffiness recovery rate) can be obtained, thus completing this invention.

[0012] That is, the present invention has the following structure.

[0013] [1] A nonwoven fabric comprising: a first layer containing at least a portion of thermally bonded composite fibers 1 whose intersections are thermally bonded; and a second layer containing at least a portion of thermally bonded composite fibers 2, wherein the nonwoven fabric,

[0014] The thermally bondable composite fiber 1 has a fiber diameter of 5 μm to 18 μm, and the thermally bondable composite fiber 2 has a fiber diameter of 12 μm to 35 μm.

[0015] The fiber diameter of the thermally bonded composite fiber 2 is larger than that of the thermally bonded composite fiber 1.

[0016] The specific volume of the first layer is 150 cm³. 3 / g~400 cm 3 / g, the specific volume of the second layer is 150 cm³ 3 / g~400 cm 3 / g.

[0017] [2] According to the nonwoven fabric described in [1], the first layer and the second layer are integrated by the fusion of the thermally adhesive composite fiber 1 and the thermally adhesive composite fiber 2.

[0018] [3] The nonwoven fabric according to [1] or [2], wherein the fiber density of the first layer is 10 fibers / mm. 2 ~25 strands / mm 2 The fiber density of the second layer is 3 fibers / mm. 2 ~15 strands / mm 2 .

[0019] [4] The nonwoven fabric according to any one of [1] to [3], wherein the fiber density ratio in the first layer is 1.4 or less, and the fiber density ratio in the second layer is 1.4 or less.

[0020] [5] The nonwoven fabric according to any one of [1] to [4], wherein the fiber diameter of the thermally bondable composite fiber 2 is 1.1 to 2.5 times that of the fiber diameter of the thermally bondable composite fiber 1.

[0021] The effects of the invention

[0022] This invention provides a nonwoven fabric that is fluffy, soft, smooth, and has excellent fluffiness recovery. Detailed Implementation

[0023] The nonwoven fabric of the present invention comprises: a first layer containing at least a portion of thermally bonded composite fibers 1; and a second layer containing at least a portion of thermally bonded composite fibers 2. The nonwoven fabric is characterized in that: the fiber diameter of the thermally bonded composite fibers 1 is 5 μm to 18 μm, the fiber diameter of the thermally bonded composite fibers 2 is 12 μm to 35 μm, and the fiber diameter of the thermally bonded composite fibers 2 is larger than the fiber diameter of the thermally bonded composite fibers 1.

[0024] The specific volume of the first layer is 150 cm³. 3 / g~400 cm 3 / g, the specific volume of the second layer is 150 cm³ 3 / g~400 cm 3 / g.

[0025] (Thermo-adhesive composite fiber 1)

[0026] The thermally bondable composite fiber 1 used in this invention has a fiber diameter of 5 μm to 18 μm. If the fiber diameter of the thermally bondable composite fiber 1 is 5 μm or more, the fiber is less prone to collapse under pressure, which can improve the fluffiness recovery rate of the nonwoven fabric. If it is less than 18 μm, the roughness is small, and the smoothness is easily perceived. From the above point of view, 6 μm to 16 μm is preferred, and 8 μm to 14 μm is more preferred.

[0027] The fiber length of the heat-bonding composite fiber 1 is not particularly limited, but is preferably 3 mm to 200 mm, more preferably 20 mm to 120 mm, and even more preferably 30 mm to 60 mm. If the fiber length is 3 mm or more, the entanglement between the fibers increases, improving the shape retention of the web and the strength of the nonwoven fabric. If the fiber length is less than 200 mm, the fibers tend to align in the thickness direction of the nonwoven fabric, increasing its bulkiness or softness.

[0028] Thermo-bonding composite fiber 1 is not particularly limited to any fiber that can be melted by heat and form bonding points, and examples include concentric sheath core type composite fiber, eccentric sheath core type composite fiber, or parallel type composite fiber. In addition, the cross-sectional shape of the composite fiber is not particularly limited, and any of the following can be used: round or elliptical, triangular or quadrangular, star or octagonal, segmented or hollow, etc.

[0029] The thermoplastic resin constituting the heat-bonding composite fiber 1 is not particularly limited, but may include: polyethylene resins such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), or high-density polyethylene (HDPE); polypropylene resins such as crystalline polypropylene (PP) or copolymers of propylene and α-olefins (excluding propylene) with propylene as the main component (Co-PP); polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate, copolymerized polyethylene terephthalate (Co-PET), polylactic acid, polyglycolic acid, or polybutylene succinate; polyvinyl alcohol resins; polyvinyl acetate resins; acrylic resins; polystyrene resins; polyurethane resins; polyamide resins; or fluorinated resins. Among these, polyethylene resins, polypropylene resins, or polyester resins are preferred from the perspective of excellent processability. The combination of thermoplastic resins constituting the heat-bonding composite fiber 1 is not particularly limited. From the perspective of expanding the processing temperature range, a melting point difference of 10°C or more is preferred, more preferably 30°C or more, and even more preferably 50°C or more. Examples of specific combinations of high-melting-point and low-melting-point components of the thermoplastic resins include PP / HDPE, PP / LLDPE, PP / Co-PP, PET / HDPE, PET / LLDPE, PET / Co-PET, and PET / PP. From the viewpoints of feel, raw material cost, and production stability, a combination of PP / HDPE or PET / HDPE is preferred, and a combination of PET / HDPE is more preferred. Furthermore, from the viewpoint of heat bonding, a low-melting-point component preferably accounts for 50% or more of the surface area of ​​the heat-bonding composite fiber 1, more preferably 70% or more.

[0030] The volume ratio of low-melting-point components to high-melting-point components is not particularly limited. A higher proportion of low-melting-point components increases the bonding strength between the thermally bonded composite fibers 1, or between the first and second layers, resulting in a high-strength nonwoven fabric. Conversely, a higher proportion of high-melting-point components tends to improve the bulkiness or softness and bulk recovery rate of the nonwoven fabric. From this perspective, the volume ratio of low-melting-point components to high-melting-point components is preferably 20 / 80 to 80 / 20, more preferably 30 / 70 to 70 / 30.

[0031] The thermoplastic resin constituting the thermally bondable composite fiber 1 may also contain additives such as antioxidants, light stabilizers, ultraviolet absorbers, neutralizers, nucleating agents, epoxy stabilizers, lubricants, antibacterial agents, deodorants, flame retardants, antistatic agents, pigments, or plasticizers, as needed, without hindering the effects of the present invention.

[0032] (First floor)

[0033] The fiber density of the first layer in this invention is not particularly limited, but is preferably 10 fibers / mm. 2 ~25 strands / mm 2 More preferably, 12 strands / mm 2 ~22 strands / mm 2 Therefore, 14 strands / mm is preferred. 2 ~20 roots / mm 2 If the fiber density of the first layer is 10 fibers / mm 2 Increasing the number of fiber intersections improves the strength of the nonwoven fabric; for example, 25 fibers / mm. 2 The number of intersections between fibers is reduced, which can improve the bulkiness or softness of nonwoven fabrics.

[0034] The first layer in this invention is not particularly limited, but a fiber density ratio of 1.4 or less is preferred. If the fiber density ratio in the first layer is 1.4 or less, even if a thermally bonded composite fiber 1 with a small fiber diameter is used, areas with high fiber density are less likely to occur in the first layer, and the softness of the nonwoven fabric is less likely to be damaged. From this point of view, 1.3 or less is more preferred, and 1.2 or less is even more preferred. Furthermore, the lower limit of the fiber density ratio in the first layer is 1.0. The closer it is to 1.0, the closer the fiber density is to a uniform state, that is, the closer it is to the ideal state in this invention.

[0035] Here, the fiber density ratio in this specification is expressed as the ratio of the fiber density of the high-density portion to the low-density portion in each of the first and second layers. In addition, the terms "high-density portion" and "low-density portion" are defined as follows: in the upper and lower portions obtained by dividing each layer into two equal parts along the thickness direction, the side with the higher fiber density when measuring the fiber density is called the "high-density portion," and the side with the lower fiber density is called the "low-density portion."

[0036] In addition, the "fiber density" in this specification is expressed as the number of fibers per unit area in the cross-section of the nonwoven fabric, and the unit may be, for example, fibers / mm. 2 The method for determining fiber density will be described in detail in the examples.

[0037] There is no particular limitation on the weight per unit area of ​​the first layer, but it is preferably 5 g / m². 2 ~50 g / m 2 More preferably 8 g / m2 ~40 g / m 2 The preferred value is 10 g / m 2 ~30 g / m 2 If the weight per unit area of ​​the first layer is 5 g / m² 2 The above indicates that the nonwoven fabric has a low roughness and its smoothness is easily perceptible. If it is 50 g / m²... 2 The thickness of the nonwoven fabric will not be too thick, making it easy to maintain its drape.

[0038] The thickness of the first layer is not particularly limited, but is preferably 0.5 mm to 20 mm, more preferably 1 mm to 10 mm, and even more preferably 2 mm to 5 mm. If the thickness of the first layer is 0.5 mm or more, a nonwoven fabric with excellent bulkiness or softness can be obtained, and if it is 20 mm or less, a nonwoven fabric with excellent drape can be obtained.

[0039] The specific volume of the first layer in this invention is 150 cm³. 3 / g~400 cm 3 / g. If the specific volume of the first layer is 150cm³ 3 A weight of 1 g or higher will yield a nonwoven fabric with excellent bulkiness or softness; for example, a 400 cm² nonwoven fabric. 3 When the density is below a certain value (g), the decrease in strength is suppressed, resulting in a nonwoven fabric with excellent processability. From this perspective, the specific volume of the first layer is preferably 160 cm³. 3 / g~350 cm 3 / g, and more preferably 170 cm 3 / g~300 cm 3 / g. If it is 1% by weight or more, the effect commensurate with the use can be obtained; if it is less than 30% by weight, a non-woven fabric that is not prone to pilling can be obtained.

[0040] The first layer may also include fibers other than the heat-bonding composite fiber 1, to the extent that it does not impair the effects of the present invention. There are no particular limitations on the fibers other than the heat-bonding composite fiber 1, and examples include: natural fibers (wood fibers, etc.), regenerated fibers (rayon, etc.), semi-synthetic fibers (acetate, etc.), or chemical fibers, synthetic fibers (polyester fibers, acrylic fibers, nylon fibers, vinyl chloride fibers, etc.) and other fibers that do not have heat-bonding properties (hereinafter referred to as "non-heat-bonding fibers"); heat-bonding composite fibers with a fiber diameter of less than 5 μm; or heat-bonding composite fibers with a fiber diameter of more than 18 μm. When fibers other than the heat-bonding composite fiber 1 are included, their proportion is not limited as long as it does not impair the effects of the present invention; for example, it may be 1% to 30% by weight, preferably 3% to 15% by weight.

[0041] Furthermore, the term "non-thermal bonding fiber" in this specification refers to fibers that do not undergo thermal changes (melting or softening, etc.) during the thermal bonding process in the manufacture of nonwoven fabrics.

[0042] (Thermo-adhesive composite fiber 2)

[0043] The thermally bondable composite fiber 2 used in this invention has a fiber diameter of 12 μm to 35 μm. If the fiber diameter of the thermally bondable composite fiber 2 is 12 μm or more, the cushioning or fluffiness recovery rate of the nonwoven fabric can be improved; if it is 35 μm or less, the whiteness of the nonwoven fabric is improved, resulting in good masking properties. Furthermore, it can reduce roughness or stiffness. From this perspective, a diameter of 14 μm to 30 μm is preferred, and more preferably 16 μm to 28 μm.

[0044] The effect of this invention can be obtained as long as the fiber diameter of the thermally bonded composite fiber 2 used in this invention is greater than that of the thermally bonded composite fiber 1. Preferably, the fiber diameter is 1.1 to 2.5 times that of the thermally bonded composite fiber 1, more preferably 1.2 to 2.3 times, and even more preferably 1.3 to 2.2 times, thereby obtaining a nonwoven fabric with excellent fluffiness recovery.

[0045] Regarding the fiber length, composite morphology, cross-sectional shape, thermoplastic resin, and combination of high-melting-point and low-melting-point components of the thermo-bonded composite fiber 2, the structure can be arbitrarily selected to be the same as that described in the thermo-bonded composite fiber 1.

[0046] (Second layer)

[0047] The fiber density of the second layer in this invention is not particularly limited, but is preferably 3 fibers / mm. 2 ~15 strands / mm 2 More preferably 4 strands / mm 2 ~14 strands / mm 2 Therefore, 5 strands / mm is preferred. 2 ~12 strands / mm 2 If the fiber density of the second layer is 3 fibers / mm 2 Increasing the number of fiber intersections improves the strength of the nonwoven fabric; for example, 15 fibers / mm. 2 The number of intersections between fibers is reduced, which can improve the bulkiness or softness of nonwoven fabrics.

[0048] The second layer in this invention is not particularly limited, but a fiber density ratio of 1.4 or less is preferred. If the fiber density ratio in the second layer is 1.4 or less, the roughness or stiffness of the nonwoven fabric can be reduced even when using thermally bonded composite fibers 2 with a large fiber diameter ratio. From this point of view, 1.3 or less is more preferred, and 1.2 or less is even more preferred. Furthermore, the lower limit of the fiber density ratio of the second layer is 1.0.

[0049] The weight per unit area of ​​the second layer is not particularly limited, but is preferably 5 g / m². 2 ~50 g / m 2 More preferably 8 g / m 2 ~40 g / m 2 The preferred value is 10 g / m 2 ~30 g / m 2 If the weight per unit area of ​​the second layer is 5 g / m² 2 In addition to maintaining the strength of nonwoven fabrics, the above methods can also improve the bulk recovery rate, which is 40 g / m². 2 The following non-woven fabrics will not be too stiff and will have a good feel.

[0050] The thickness of the second layer is not particularly limited, but is preferably 0.5 mm to 20 mm, more preferably 1 mm to 10 mm, and even more preferably 2 mm to 5 mm. If the thickness of the second layer is 0.5 mm or more, a nonwoven fabric with excellent bulkiness or softness can be obtained, and if it is 20 mm or less, a nonwoven fabric with excellent drape can be obtained.

[0051] The specific volume of the second layer in this invention is 150 cm³. 3 / g~400 cm 3 / g. If the specific volume of the second layer is 150cm³ 3 A weight of 1 g or higher will yield a nonwoven fabric with excellent bulkiness or softness; for example, a 400 cm² nonwoven fabric. 3 When the density is below a certain value (g), the decrease in strength is suppressed, resulting in a nonwoven fabric with excellent processability. From this perspective, the specific volume of the second layer is preferably 160 cm³. 3 / g~350 cm 3 / g, and more preferably 170 cm 3 / g~300 cm 3 / g.

[0052] The second layer may also include fibers other than the heat-bonded composite fiber 2, to the extent that it does not impair the effects of the present invention. There is no particular limitation on the fibers other than the heat-bonded composite fiber 2; examples include non-heat-bonded fibers, heat-bonded composite fibers with a fiber diameter less than 12 μm, or heat-bonded composite fibers with a fiber diameter greater than 35 μm. When fibers other than the heat-bonded composite fiber 2 are included, their proportion is not limited as long as it does not hinder the effects of the present invention; for example, it can be 1% to 30% by weight, preferably 3% to 15% by weight. If it is 1% by weight or more, an effect commensurate with its use can be obtained; if it is 30% by weight or less, a nonwoven fabric that is not prone to pilling can be obtained.

[0053] (Non-woven fabric)

[0054] The nonwoven fabric of the present invention has a first layer and a second layer. By forming this structure, a nonwoven fabric with excellent fluffiness, softness, smoothness, and fluffiness recovery rate can be obtained. In particular, the improvement in fluffiness recovery rate is considered to be a novel effect exhibited by combining specific layers, which cannot be expected by a single-layer nonwoven fabric consisting only of the first or second layer.

[0055] The nonwoven fabric of the present invention is not particularly limited, but it is preferable that the first layer and the second layer are integrated by welding, adhesive, or interlocking. From the viewpoint of peel strength or skin irritation, it is preferable that the first layer and the second layer are integrated by welding. While there are no particular limitations in the case of the first layer and the second layer being integrated by welding, it is preferable that they are integrated by welding thermally bonded composite fiber 1 and thermally bonded composite fiber 2. In particular, it is preferable that the low-melting-point components of thermally bonded composite fiber 1 and thermally bonded composite fiber 2 are made of highly compatible resins, and that the welding is performed by melting at least one, and more preferably both, of their low-melting-point components. There are no particular limitations on the combination of resins with high compatibility, but examples include: HDPE / HDPE, LDPE / LDPE, LLDPE / LLDPE, HDPE / LDPE, HDPE / LLDPE, LDPE / LLDPE, PP / PP, coPP / coPP, PP / coPP, PET / PET, coPET / coPET, and PET / coPET. From the viewpoint of peel resistance and processing temperature, HDPE / HDPE, LDPE / LDPE, LLDPE / LLDPE, HDPE / LDPE, HDPE / LLDPE, LDPE / LLDPE, PP / PP, coPP / coPP, and PP / coPP are preferred, and HDPE / HDPE, LDPE / LDPE, LLDPE / LLDPE, PP / PP, and coPP / coPP are even more preferred.

[0056] The nonwoven fabric of the present invention is not particularly limited in terms of its unit area weight, but is preferably 10 g / m².2 ~100 g / m 2 More preferably 16 g / m 2 ~80 g / m 2 Therefore, 20 g / m is preferred. 2 ~60 g / m 2 .

[0057] The unit area weight ratio of the first layer to the second layer in the nonwoven fabric of the present invention is not particularly limited, but is preferably 20 / 80 to 80 / 20, more preferably 25 / 75 to 75 / 25, and even more preferably 30 / 70 to 70 / 30. Within the range described above, a nonwoven fabric with excellent manufacturing stability or fluffiness recovery rate can be obtained.

[0058] There is no particular limitation on the tensile strength per unit area weight of the nonwoven fabric. From the viewpoint of minimizing the generation of fine fibers and minimizing breakage or poor processability even when the unit area weight is reduced, it is preferably 0.5 N / 50 mm or more, more preferably 0.7 N / 50 mm or more, and even more preferably 1.0 N / 50 mm or more. As for the upper limit of the tensile strength per unit area weight, there is no particular limitation. From the viewpoint of balancing the specific volume of the nonwoven fabric, it is preferably 3.0 N / 50 mm or less, more preferably 2.5 N / 50 mm or less, and even more preferably 2.0 N / 50 mm or less.

[0059] There is no particular limitation on the specific volume of nonwoven fabric, but it is preferably 150 cm³. 3 / g or more, preferably 160 cm 3 / g or more, and preferably 170 cm 3 / g or more. If the specific volume is 150 cm³ 3 If the specific volume is above a certain value (g), the bulkiness or softness of the nonwoven fabric can reach a satisfactory level. There is no particular limit to the upper limit of the specific volume; however, from the viewpoint of balancing the strength of the nonwoven fabric, 400 cm³ is preferred. 3 / g or less, more preferably 350 cm 3 / g or less, and more preferably 300 cm 3 / g or less.

[0060] The nonwoven fabric of this invention is not particularly limited, and can also be laminated with nonwoven fabrics or films other than the nonwoven fabric of this invention, such as hot-air nonwoven fabrics, spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, needle-punched nonwoven fabrics, films, meshes, or nets. Through lamination, it is possible to control properties such as softness and permeability or liquid recirculation. The method of lamination is not particularly limited, and examples include lamination using adhesives such as hot melt adhesives, and lamination using thermal bonding methods such as hot air bonding or hot embossing.

[0061] Nonwoven fabrics can also be subjected to electrochemical processing, water-repellent processing, hydrophilic processing, antibacterial processing, ultraviolet absorption processing, near-infrared absorption processing, or electret processing, etc., within the scope of not impairing the effects of the present invention, depending on the purpose.

[0062] (Manufacturing method of non-woven fabric)

[0063] The nonwoven fabric of the present invention is not particularly limited, and includes: a step of forming a web 1 containing thermally bondable composite fibers 1 with a fiber diameter of 5 μm to 18 μm (hereinafter sometimes referred to as web forming step 1); a step of forming a web 2 containing thermally bondable composite fibers 2 with a fiber diameter of 12 μm to 35 μm (hereinafter sometimes referred to as web forming step 2); and a step of thermally bonding the intersections of the thermally bondable composite fibers 1 and 2 without pressure (hereinafter sometimes referred to as thermal bonding step). According to this method, the intersections of fibers can be thermally bonded in a manner that achieves a specific fiber density while maintaining the shape of the web, i.e., a low density in the thickness direction, thereby obtaining a nonwoven fabric that is fluffy, has excellent softness, is smooth, and has excellent fluffiness recovery rate.

[0064] There are no particular limitations on the method for manufacturing nonwoven fabric from mesh 1 and mesh 2. Examples include: when mesh 1 and mesh 2 are overlapped, a thermal bonding process is performed to thermally bond the intersections of thermally bondable composite fibers 1 in mesh 1 and the intersections of thermally bondable composite fibers 2 in mesh 2, thereby achieving interlayer integration of mesh 1 and mesh 2; or, for mesh 1 and mesh 2, the intersections of fibers are thermally bonded separately, and the resulting layers are overlapped and integrated with the first layer and the second layer through heat treatment, ultrasonic treatment, adhesive treatment or interlocking treatment, etc. From the perspectives of peel resistance, skin irritation, and manufacturing simplification, it is preferable to perform a thermal bonding process in which the thermally bonded composite fibers 1 in the mesh 1 and the thermally bonded composite fibers 2 in the mesh 2 are thermally bonded together, thereby achieving interlayer integration of the mesh 1 and the mesh 2.

[0065] The web 1 or web 2 containing thermally bondable composite fibers is not particularly limited. It can be a long fiber web formed by spunbonding, meltblowing, or tow opening, or a short fiber web formed by using short fibers (staple or chopped fibers) and by carding, air-laying, or wet-laying. From the viewpoint of improving bulkiness or softness, a short fiber web formed by carding or air-laying is preferred, and a short fiber web formed by carding is more preferred. Furthermore, in this invention, "web" refers to a fiber aggregate in a state of entanglement, meaning that the intersections of the composite fibers are not bonded.

[0066] Next, in the obtained web 1 or web 2, the intersections of the thermally bondable composite fibers are thermally bonded without pressure. The heat medium in the thermal bonding process is not particularly limited; examples include hot air or superheated steam. Superheated steam is preferred from the perspectives of reducing pilling, excellent hand feel, and the productivity of nonwoven fabrics. The thermal bonding process can be exemplified by a method of continuously obtaining nonwoven fabrics by introducing the web into a furnace filled with hot air or superheated steam via a conveyor.

[0067] The temperature of the heat transfer medium is not particularly limited, but can be exemplified by the melting point or softening point of the low-melting-point component constituting the composite fiber, ranging from +0°C to 30°C. Furthermore, the blowing velocity of the heat transfer medium is not particularly limited, but is preferably less than 0.1 m / s to obtain a specific fiber density. Additionally, the blowing pressure of the heat transfer medium is not particularly limited, but is preferably less than 0.1 kPa to obtain a specific fiber density.

[0068] The nonwoven fabric of this invention can be used in absorbent items such as diapers, sanitary napkins, and incontinence pads; hygiene materials such as masks, gowns, surgical gowns, and bandages; interior decoration materials such as wall panels, window slats, and flooring materials; household materials such as drapes, cleaning cloths, and kitchen waste covers; toiletries such as disposable toilets and toilet seats; pet supplies such as pet mats, pet diapers, and pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil-absorbing materials, abrasives, and absorbents for ink cartridges; and fiber products such as general medical materials, bedding materials, and nursing care products.

[0069] Example

[0070] The present invention will now be described in detail through examples, but the invention is not limited to these examples. Furthermore, the methods or definitions for measuring the physical properties shown in the examples are illustrated below. Additionally, all the following physical property measurements were performed after heat-treating the nonwoven fabric in an oven at 110°C for 5 minutes to reset the stress on the nonwoven fabric.

[0071] <Fiber diameter of thermo-bonded composite fiber 1 and thermo-bonded composite fiber 2>

[0072] Images of the first and second layers were captured at 100x to 200x magnification using a scanning electron microscope (Hitachi High-Tech, Inc., SU-8000). The fiber diameters of thermally bonded composite fiber 1 and thermally bonded composite fiber 2 were determined using image analysis software (ImageJ). The fiber diameter was taken as the average value when 50 fibers were measured.

[0073] <Fiber diameter ratio of thermally bonded composite fiber 1 to thermally bonded composite fiber 2>

[0074] Based on the fiber diameters of the obtained thermally bonded composite fiber 1 and thermally bonded composite fiber 2, the fiber diameter ratio is calculated using the following formula.

[0075] Fiber diameter ratio (times) = Fiber diameter of thermally bonded composite fiber 2 ÷ Fiber diameter of thermally bonded composite fiber 1

[0076] <Fiber density of the first and second layers>

[0077] (1) Method for preparing the specimen for observation

[0078] A nonwoven fabric, cut to a diameter of 1 cm (machine direction) × 3 cm (width direction) (cross direction), was impregnated with a photocurable resin (PADICO, a manufacturer of ultraviolet-light emitting diode (UV-LED) resin, Shizuku Hoshino [soft]). The photocurable resin was then cured by UV irradiation. Next, the cured sample was cut using a microtome (Leica, RM2265) to a thickness of 10 μm in the MD direction, yielding an observation sample with a diameter of 10 μm (MD direction) × 3 cm (CD direction) × thickness (thickness direction).

[0079] (2) Determination of fiber density

[0080] An observation specimen is placed on a glass slide between two polarizing plates arranged in a cross-nicols configuration. An image of the sliced ​​section (3 cm (CD direction) × thickness (thickness direction)) of the observation specimen is taken at 30x magnification using a microscope (KEYENCE, VHX-6000).

[0081] The number of fibers in the first and second layers was determined using image analysis software (ImageJ), and then divided by the area to calculate the fiber count.

[0082] Specifically, the image was converted to 16 bits using ImageJ and then binarized to distinguish fibers from non-fiber areas. Next, in the first and second layers, a range was selected (5 mm (CD direction) × half the thickness of the first and second layers (thickness direction)) for the upper and lower portions bisected along the thickness direction. The "Analyze Particle" function in ImageJ was used to determine the number of fibers in the selected area. The fiber count was then divided by the area of ​​the selected portion to calculate the fiber count (fibers / mm²). 2 Here, in the upper and lower parts of the first layer, the parts with higher fiber density are designated as high-density parts of the first layer, and the parts with lower fiber density are designated as low-density parts of the first layer. Similarly, in the upper and lower parts of the second layer, the parts with higher fiber density are designated as high-density parts of the second layer, and the parts with lower fiber density are designated as low-density parts of the second layer. Based on the obtained fiber density of each part, the fiber density of the first and second layers is calculated using the following formula. Furthermore, the fiber density of each part is taken as the average value of measurements taken at two locations.

[0083] Fiber density of the first layer (fibers / mm) 2 = (Fiber density of the high-density section of the first layer (fibers / mm)) 2 ) + Fiber density of the low-density section of the first layer (fibers / mm) 2 ))÷2

[0084] Second layer fiber density (roots / mm) 2 = (Fiber density of the high-density section of the second layer (fibers / mm)) 2 ) + Fiber density of the low-density section of the second layer (fibers / mm) 2 ))÷2

[0085] <Fiber density ratio in the first and second layers>

[0086] Based on the fiber density of each part obtained by the method, the fiber density ratio of the first layer and the second layer is calculated by the following formula.

[0087] The fiber density ratio in the first layer = the fiber density of the high-density portion of the first layer (fibers / mm²) 2 ) ÷ Fiber density of the low-density section of the first layer (fibers / mm) 2 )

[0088] The fiber density ratio in the second layer = the fiber density of the high-density portion of the second layer (fibers / mm²) 2 ) ÷ Fiber density of the low-density section of the second layer (fibers / mm) 2 )

[0089] <Weight per unit area>

[0090] The weight of the nonwoven fabric cut into 150 mm × 150 mm pieces was measured, and the value converted to per unit area was taken as the unit area weight of the nonwoven fabric (g / m²). 2 The weight per unit area is the average of two measurements. Furthermore, the weight per unit area of ​​the first and second layers is measured by peeling the obtained nonwoven fabric into first and second layers (using solvents, etc., if necessary).

[0091] <Thickness>

[0092] Using a laser thickness gauge (manufactured by Keyence, IL-S065), 0.7 gf / cm was applied over 5 seconds. 2 A pressure of 68.6 Pa was applied, and the thickness at this point was taken as the thickness (mm) of the nonwoven fabric. The thickness was taken as the average value of measurements taken at 5 locations. In addition, the unit area weight of the first and second layers was measured by peeling the obtained nonwoven fabric into the first and second layers (using solvents, etc., if necessary).

[0093] Specific volume

[0094] According to the obtained unit area weight (g / m²) 2 The specific volume of the nonwoven fabric is calculated using the formula based on the fabric's thickness (mm). A larger specific volume indicates a more fluffy and porous fabric.

[0095] Specific volume (cm) 3 / g) = Thickness (mm) ÷ Weight per unit area (g / m²) 2 )×1000

[0096] <Tensile Strength>

[0097] Using an Autograph (manufactured by Shimadzu Corporation, AGX-J), a sample cut to a size of 50 mm in the CD direction and 150 mm in the MD direction was stretched at a chuck spacing of 100 mm and a stretching speed of 100 mm / min. The maximum stress at this point was taken as the tensile strength of the nonwoven fabric (N / 50 mm). The tensile strength was taken as the average of three measurements.

[0098] <Work Compression (WC)>

[0099] The compression work was measured using a handheld compressor (KES-G5, manufactured by KATO TECH, Inc.). First, the nonwoven fabric was placed on the sample stage, and the compression was performed from above the sample using a speed of 0.1 mm / s at a sensitivity of 2 cm². 2 The pressure component is compressed until the stress reaches 50 gf / cm.2 (4.9 kPa) up to the stress curve Pa relative to the distance is obtained. Based on the obtained Pa, the compression workload is calculated by numerical processing based on the following equation (1). The compression workload is taken as the average value of 10 measurements. In addition, in the following equation, T m Indicates 50 gf / cm 2 Thickness under a load of (4.9 kPa), T0 represents 0.5 gf / cm. 2 Thickness under load of (49.0 Pa). A higher compression load indicates greater softness; in this invention, the thickness is measured at 3 gf·cm / cm. 2 The above results indicate excellent softness.

[0100]

[0101] <Mean deviation of friction coefficient (MMD)>

[0102] The average deviation of the coefficient of friction was measured using a surface testing machine (manufactured by KATO TECH, KES-FB4) as follows. The first layer was used as the measurement surface, and a friction coefficient of 10 gf / cm was applied through the contact element. 2 Under a load of (0.98 kPa), the average deviation of the coefficient of friction was measured by moving along the MD direction with SENS (sensitivity) set to High and a contact speed of 1.0 mm / s. The average deviation of the coefficient of friction was taken as the average of 10 measurements. The smaller the average deviation of the coefficient of friction, the smoother the surface. In this invention, a deviation of 0.007 or less is considered to indicate excellent smoothness.

[0103] <Fluff recovery rate>

[0104] Using a vacuum food sealing machine (manufactured by Iris Ohyama (VPF-385T)), two pieces of non-woven fabric cut to 10 cm squares were placed into a special sealing bag and vacuum-sealed, then stored at room temperature for 24 hours. The thickness after opening the sealed bag for 5 minutes was measured using the method described in the <Thickness> measurement section, and this thickness (mm) was taken as the thickness after opening. Based on the thickness before sealing and the thickness after opening, the fluffiness recovery rate was calculated using the following formula. In this invention, a fluffiness recovery rate of 40% or higher is considered to indicate excellent fluffiness recovery.

[0105] Fluff recovery rate (%) = Thickness after opening (mm) ÷ Thickness before sealing (mm) × 100

[0106] [Example 1]

[0107] As the heat-bonding composite fiber 1, polyethylene terephthalate (intrinsic viscosity (measured at 20°C with an intrinsic viscosity of 0.65 dl / g and a melting point of 250°C) was prepared in a 50 / 50 volume ratio in the core and high-density polyethylene (density: 0.956 g / cm³) was prepared in the sheath. 3 A concentric sheath core type composite fiber with a melt flow rate (190℃, load 21.18 N): 16 g / 10 min, melting point 130℃, fineness 1.3 dtex, and fiber length 45 mm is used to prepare a mesh 1 containing thermally bondable composite fiber 1 (unit area weight: 12 g / m²) by carding. 2 ).

[0108] As the thermo-bonded composite fiber 2, a concentric sheath-core type composite fiber with a fineness of 4.4 dtex and a fiber length of 51 mm was prepared, consisting of polyethylene terephthalate (the same as that of thermo-bonded composite fiber 1) in the core and high-density polyethylene (the same as that of thermo-bonded composite fiber 1) in the sheath, at a volume ratio of 50 / 50. A mesh 2 containing the thermo-bonded composite fiber 2 (weight per unit area: 12 g / m²) was then produced by carding. 2 ).

[0109] A multi-layered mesh, with mesh 2 superimposed on mesh 1, is introduced into a furnace filled with superheated steam at 180°C for 10 seconds to obtain a nonwoven fabric. The wind speed of the superheated steam is less than 0.1 m / s.

[0110] [Example 2]

[0111] Except for changing the fineness of the thermally bondable composite fiber 1 to 1.7 dtex, the nonwoven fabric was obtained in the same manner as in Example 1.

[0112] [Example 3]

[0113] Except for changing the fineness of the thermally bondable composite fiber 1 to 2.2 dtex and the fiber length to 51 mm, the nonwoven fabric was obtained in the same manner as in Example 1.

[0114] [Example 4]

[0115] Except for changing the fineness of the thermally bondable composite fiber 1 to 0.9 dtex, the nonwoven fabric was obtained in the same manner as in Example 1.

[0116] [Example 5]

[0117] Except for changing the fineness of the thermally bondable composite fiber 2 to 2.2 dtex, the nonwoven fabric was obtained in the same manner as in Example 2.

[0118] [Example 6]

[0119] Except for changing the volume ratio of the core component to the sheath component of the thermally bonded composite fiber 2 to 60 / 40 and changing the fineness to 3.3 dtex, the nonwoven fabric was obtained in the same manner as in Example 2.

[0120] [Example 7]

[0121] Except for changing the fineness of the thermally bondable composite fiber 2 to 5.6 dtex, the nonwoven fabric was obtained in the same manner as in Example 2.

[0122] [Example 8]

[0123] Except for changing the fineness of the thermally bondable composite fiber 2 to 9.0 dtex, the nonwoven fabric was obtained in the same manner as in Example 2.

[0124] [Example 9]

[0125] In addition to setting the unit area weight of mesh 1 to 8 g / m 2 The weight per unit area of ​​mesh 2 is set to 16 g / m². 2 In addition, nonwoven fabrics were obtained in the same manner as in Example 2.

[0126] [Example 10]

[0127] In addition to setting the unit area weight of mesh 1 to 16 g / m 2 Set the unit area weight of mesh 2 to 8g / m². 2 In addition, nonwoven fabrics were obtained in the same manner as in Example 2.

[0128] [Example 11]

[0129] The nonwoven fabric obtained in the same manner as in Example 2 was further treated with hot air at 130°C and a circulating air speed of 1.0 m / s for 10 seconds using a hot air circulating dryer, thereby obtaining the nonwoven fabric.

[0130] [Example 12]

[0131] The nonwoven fabric is obtained in the same manner as in Example 2, except that the mesh 1 is overlapped on the mesh 2.

[0132] [Comparative Example 1]

[0133] Except for changing the volume ratio of the core component to the sheath component of the thermally bonded composite fiber 1 to 60 / 40, changing the fineness to 3.3 dtex, and changing the fiber length to 51 mm, the nonwoven fabric was obtained in the same manner as in Example 1.

[0134] [Comparative Example 2]

[0135] The multilayer mesh obtained in the same manner as in Example 2 was treated with hot air at 130°C and a circulating air velocity of 1.0 m / s for 10 seconds using a hot air circulating dryer to obtain a nonwoven fabric.

[0136] [Comparative Example 3]

[0137] The mesh 1 (weight per unit area: 24 g / m²) obtained in the same manner as in Example 2 was used. 2 The material is introduced into a furnace filled with superheated steam at 180°C for 10 seconds, thereby obtaining a single-layer nonwoven fabric consisting only of the first layer. The wind speed of the superheated steam is less than 0.1 m / s.

[0138] [Comparative Example 4]

[0139] The mesh 2 (weight per unit area: 24 g / m²) obtained in the same manner as in Example 1 was used. 2 The material is introduced into a furnace filled with superheated steam at 180°C for 10 seconds, thereby obtaining a single-layer nonwoven fabric consisting only of the second layer. The wind speed of the superheated steam is less than 0.1 m / s.

[0140] The physical properties of the nonwoven fabrics obtained in Examples 1 to 8 are shown in Table 1, and the physical properties of the nonwoven fabrics obtained in Examples 9 to 12 and Comparative Examples 1 to 4 are shown in Table 2.

[0141] [Table 1]

[0142]

[0143] [Table 2]

[0144]

[0145] As can be seen from Tables 1 and 2, the nonwoven fabrics of Examples 1 to 12, which satisfy the constituent requirements of the present invention, are fluffy, soft, smooth, and have excellent fluff recovery rate. On the other hand, Comparative Example 1, which has a large fiber diameter of the thermally bonded composite fiber in the first layer, has satisfactory fluffiness, softness, and fluff recovery rate, but feels rough (not smooth). Comparative Example 2, which has a small specific volume of the first and second layers, has satisfactory smoothness and fluff recovery rate, but lacks fluffiness and softness. Comparative Example 3, which consists only of the first layer, has satisfactory fluffiness, softness, and smoothness, but has a low fluff recovery rate. Comparative Example 4, which consists only of the second layer, has satisfactory fluffiness and softness, but feels rough and has a low fluff recovery rate.

[0146] Industrial availability

[0147] The nonwoven fabric of this invention is excellent in terms of fluffiness, softness, smoothness, and fluffiness recovery rate. Therefore, it can be used in absorbent products such as diapers, sanitary napkins, and incontinence pads; hygiene materials such as masks, gowns, surgical gowns, and bandages; interior decoration materials such as wall panels, window slats, and flooring materials; household materials such as drapes, cleaning cloths, and kitchen waste covers; toiletries such as disposable toilets and toilet seats; pet supplies such as pet mats, pet diapers, and pet towels; industrial materials such as wiping materials, filters, cushioning materials, oil-absorbing materials, abrasives, and absorbents for ink cartridges; and fiber products such as general medical materials, bedding materials, and nursing care products.

Claims

1. A nonwoven fabric comprising: a first layer containing at least a portion of thermally bonded composite fibers 1 whose intersections are thermally bonded; and a second layer containing at least a portion of thermally bonded composite fibers 2 whose intersections are thermally bonded, wherein the nonwoven fabric, The thermally bondable composite fiber 1 has a fiber diameter of 5 μm to 18 μm, and the thermally bondable composite fiber 2 has a fiber diameter of 12 μm to 35 μm. The fiber diameter of the thermally bonded composite fiber 2 is larger than that of the thermally bonded composite fiber 1. The specific volume of the first layer is 150 cm³. 3 / g~400 cm 3 / g, the specific volume of the second layer is 150 cm³ 3 / g~400 cm 3 / g.

2. The nonwoven fabric according to claim 1, wherein, The first layer and the second layer are integrated by fusing the thermally bonded composite fiber 1 and the thermally bonded composite fiber 2.

3. The nonwoven fabric according to claim 1 or 2, wherein, The fiber density of the first layer is 10 fibers / mm 2 ~25 strands / mm 2 The fiber density of the second layer is 3 fibers / mm. 2 ~15 strands / mm 2 .

4. The nonwoven fabric according to claim 1 or 2, wherein, The fiber density ratio in the first layer is 1.4 or less, and the fiber density ratio in the second layer is 1.4 or less.

5. The nonwoven fabric according to claim 1 or 2, wherein, The fiber diameter of the thermally bonded composite fiber 2 is 1.1 to 2.5 times that of the thermally bonded composite fiber 1.

Images