Method for manufacturing nonwoven fabric, nonwoven fabric manufactured using the same, and absorbent article including the nonwoven fabric as a constituent member

Abstract

In the production method of the present application, hot air is blown to a web containing heat-fusible fibers having a fiber diameter of 15 μm or less under conditions such that the intersections of the fibers constituting the web are fused. The above production method preferably blows hot air to the above web under the following conditions. (1) When the melting point of the resin having the lowest melting point among the resins constituting the heat-fusible fibers is designated as Mp, the temperature T1 of the side of the above web opposite the face to which the hot air is blown is Mp or higher and Mp + 15°C or lower. (2) The temperature T1 is lower than the temperature T2 of the face to which the hot air is blown of the above web, and the difference between the temperature T1 and the temperature T2 is 10°C or higher and 35°C or lower. (3) The supply speed of the hot air is 0.30 m / sec or higher and 0.60 m / sec or lower.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing nonwoven fabric, a nonwoven fabric manufactured using the method, and an absorbent article comprising the nonwoven fabric as a constituent component. Background Technology

[0002] Absorbent articles such as disposable diapers are composed of sheet components formed from fibrous materials. As a method for manufacturing such sheet components, a method for nonwoven fabrication is known, which involves blowing hot air into a web formed from fibers. For example, Patent Document 1 describes a method for manufacturing a nonwoven fabric that is immediately cooled after heat treatment of a fiber assembly containing heat-fused fibers with low-melting-point and high-melting-point components.

[0003] Furthermore, the applicant previously disclosed a method for manufacturing a nonwoven fabric in which the long axis of the cross-section of the flattened fibers is oriented substantially along the plane of the nonwoven fabric by performing multi-stage calendering on the hot-air nonwoven fabric (Patent Document 2). In this manufacturing method, any calendering process is performed under specified conditions using a metal calendering roller and a resin roller with a specified D hardness.

[0004] In addition, the applicant previously disclosed a method for manufacturing a nonwoven fabric with an uneven surface by blowing hot air into a web containing thermally elongated fibers to form a bonded web, and then performing an embossing process on the web (Patent Document 3).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 6-158499

[0008] Patent Document 2: Japanese Patent Application Publication No. 2006-233365

[0009] Patent Document 3: Japanese Patent Application Publication No. 2011-137249 Summary of the Invention

[0010] The present invention relates to a method for manufacturing a nonwoven fabric by blowing hot air into a web containing heat-fusion fibers to fuse the intersections of the fibers constituting the web.

[0011] The fiber diameter of the aforementioned heat-fused fibers is preferably less than 15 μm.

[0012] The above manufacturing method preferably involves blowing hot air onto the mesh under the following conditions.

[0013] (1) When the melting point of the resin with the lowest melting point among the resins constituting the above-mentioned heat-fused fibers is set as Mp, the temperature T1 of the side of the mesh opposite to the hot air blowing surface is Mp or higher and Mp+15°C or lower.

[0014] (2) The temperature T1 is lower than the temperature T2 of the hot air blowing surface of the above-mentioned net, and the difference between temperature T1 and temperature T2 is more than 10°C and less than 35°C.

[0015] (3) The supply speed of hot air is above 0.30 m / s and below 0.60 m / s.

[0016] In addition, the present invention relates to a nonwoven fabric manufactured using the above-described manufacturing method.

[0017] In addition, the present invention relates to an absorbent article comprising the aforementioned nonwoven fabric as a constituent component. Attached Figure Description

[0018] Figure 1 This is a schematic diagram illustrating the apparatus used in the method for manufacturing nonwoven fabric according to the present invention.

[0019] Figure 2 yes Figure 1 An enlarged cross-sectional view of the hot air treatment unit shown.

[0020] Figure 3 (a) to (c) are schematic diagrams illustrating the method for determining the number of fibers that produce fuzz per unit area in the embodiments. Detailed Implementation

[0021] In the manufacturing methods described in Patent Documents 1-3, nonwoven fabric is manufactured by fusing the intersections of fibers together by blowing hot air onto a web. If the web uses fibers with small diameters, although it can be nonwoven by blowing hot air, the resulting nonwoven fabric tends to have insufficient strength and hand feel, and its smoothness and skin feel may be reduced. Patent Documents 1-3 do not specifically address obtaining nonwoven fabrics with good skin feel and strength when using fibers with small diameters.

[0022] Therefore, the present invention relates to a method for manufacturing a nonwoven fabric containing fibers with small diameter and excellent skin feel and strength, a nonwoven fabric manufactured using the method, and an absorbent article containing the nonwoven fabric as a constituent component.

[0023] The present invention will now be described based on its preferred embodiments. The manufacturing method of this embodiment includes a hot air treatment step of blowing hot air into a web containing heat-fusion fibers to fuse the intersections of the fibers constituting the web. The hot air treatment step of this embodiment is a step of blowing hot air into the web, which serves as a precursor for nonwoven fabric. As a method for manufacturing nonwoven fabric by blowing hot air into the web, a hot air method that allows the hot air to penetrate the web is known; however, in the hot air treatment step of this embodiment, by employing the conditions described later (1) to (3), hot air is blown into the web to the extent that not all of the blown hot air penetrates the web, thereby manufacturing the nonwoven fabric. Hereinafter, the nonwoven fabric obtained using the hot air treatment step will also be referred to as "first nonwoven fabric 14". The nonwoven fabric obtained by performing the calendering process described later on on the first nonwoven fabric 14 will also be referred to as "second nonwoven fabric 10". In the manufacturing method of this embodiment, the second nonwoven fabric 10 is finally obtained.

[0024] The first nonwoven fabric 14 and the second nonwoven fabric 10, which are the objects of manufacture according to the present invention, can be single-layer nonwoven fabrics or multi-layer nonwoven fabrics. The following description is about the manufacture of multi-layer first nonwoven fabric 14 and second nonwoven fabric 10; however, the description is equally applicable to the manufacture of single-layer first nonwoven fabric 14 and second nonwoven fabric 10.

[0025] The first nonwoven fabric 14 and the second nonwoven fabric 10 each have a first surface and a second surface located on the opposite side, and have a laminated structure obtained by stacking a first layer forming the first surface and a second layer forming the second surface. The first layer uses the first web 11 (described later) as raw material, and the second layer uses the second web 12 (described later) as raw material. In the nonwoven fabrics 10 and 14 of this embodiment, the average fiber diameter of the fibers constituting the first layer is smaller than that of the second layer, and includes fibers with a fiber diameter of 15 μm or less.

[0026] In reference Figure 1 and Figure 2 The manufacturing method of this embodiment will also be described. Figure 1 and Figure 2 In the diagram, the symbol X indicates the conveying direction of the nonwoven fabrics 14 and 10 forming materials of conveyor nets 11, 12, 13, etc. Figure 1 The diagram illustrates one embodiment of the manufacturing apparatus used in the nonwoven fabric manufacturing method of the present invention. Figure 1 The manufacturing apparatus 100 shown includes a web forming section 20, a hot air treatment section 30, and a calendering section 40.

[0027] The web forming unit 20 includes a first guide machine 21 and a second guide machine 22. The first guide machine 21 manufactures a first web 11 corresponding to the first layer. The second guide machine 22 is a mechanism for manufacturing a second web 12 corresponding to the second layer. Raw material fibers are supplied from a raw material fiber supply unit (not shown) to each guide machine 21 and 22 and the fibers are combed. This forms the first web 11 and the second web 12. The second web 12 is overlapped on the first web 11. This forms a laminated web 13 with webs 11 and 12 stacked on top of each other. The laminated web 13 is continuously supplied to the air-permeable conveying member 31 of the hot air treatment unit 30, which will be described later.

[0028] The hot air treatment unit 30 includes a blower 32 for blowing hot air onto the laminated mesh 13, a suction box 33 for drawing in the hot air, and a conveyor 35 for conveying the laminated mesh 13. The conveyor 35 includes a breathable conveyor member 31 made of a breathable material such as a metal mesh (wire mesh, etc.) and conveyor rollers 34a, 34b, 34c, and 34d supporting the breathable conveyor member 31. The breathable conveyor member 31 is an annular belt. The conveyor 35 is configured as a conveyor belt that rotates in one direction.

[0029] A blower 32 and a suction box 33 are arranged facing each other, separated by a permeable conveying member 31. The permeable conveying member 31 conveys the laminated mesh 13 between the blower 32 and the suction box 33. The blower 32 has a hot air supply port (not shown) for supplying hot air to the permeable conveying member 31, which is arranged opposite it. The laminated mesh 13, placed on the permeable conveying member 31, is conveyed along the conveying direction X and passes under the blower 32. The laminated mesh 13 passes under the blower 32 with the second mesh 12 facing the blower 32 and the first mesh 11 facing the permeable conveying member 31. At this time, hot air heated to a predetermined temperature is blown onto the laminated mesh 13. That is, the surface of the laminated mesh 13 on the side of the second mesh 12 becomes the hot air blowing surface (hereinafter referred to as the "blowing surface"), and the surface on the side of the first mesh 11 becomes the hot air non-blowing surface (hereinafter referred to as the "non-blowing surface"). The non-blown surface is the side opposite to the blown surface. The heat-bonding fibers contained in the laminated web 13 soften or melt due to the heat imparted when the hot air is blown on them, and the intersections between the fibers bond together. This yields the first nonwoven fabric 14. The hot air blown onto the laminated web 13 is drawn back by the suction box 33.

[0030] In the conveying device 35, a first conveying roller 34a and a fourth conveying roller 34d are arranged upstream of the conveying path of the laminated mesh 13 between the blower 32 and the suction box 33, and a second conveying roller 34b and a third conveying roller 34c are arranged downstream of the conveying path. The first conveying roller 34a and the fourth conveying roller 34d are located upstream of the blower 32. The first conveying roller 34a is positioned vertically closer to the blower 32 than the fourth conveying roller 34d. The second conveying roller 34b and the third conveying roller 34c are located downstream of the blower 32. The second conveying roller 34b is positioned vertically closer to the blower 32 than the third conveying roller 34c.

[0031] The manufacturing apparatus 100 includes a cooling device 50 for cooling the permeable conveying member 31, which has been heated by hot air. The cooling device 50 is located between the third conveying roller 34c and the fourth conveying roller 34d, and cools the permeable conveying member 31 conveyed between these rollers 34c and 34d. A known device such as a blower fan that blows cold air can be used as the cooling device 50. Alternatively, any one of the conveying rollers 34a, 34b, 34c, or 34d can be designated as a cooling roller. The cooling roller contains a refrigerant such as water or gas.

[0032] The calendering section 40 includes a calendering roller 41 with a metal surface and a first resin roller 42 and a second resin roller 43 with resin surfaces. The first resin roller 42, calendering roller 41, and second resin roller 43 are arranged in a vertically overlapping manner in this order. That is, the first resin roller 42 and the second resin roller 43 are arranged facing each other in contact with the calendering roller 41. In the conveying direction X of the first nonwoven fabric 14, the first resin roller 42 is located on the upstream side, and the second resin roller 43 is located on the downstream side. When the first nonwoven fabric 14 is introduced into the calendering section 40, the first layer of the first nonwoven fabric 14 contacts the calendering roller 41 between the first resin roller 42 and the calendering roller 41. Additionally, the first layer of the first nonwoven fabric 14 contacts the calendering roller 41 between the second resin roller 43 and the calendering roller 41. The second nonwoven fabric 10 is obtained by calendering using the calendering process of the calendering section 40. It should be noted that the metal calendering roll 41, as well as the first resin roll 42 and the second resin roll 43, are all made of metal in their shaft portions.

[0033] In the manufacturing method of this embodiment, the manufacturing apparatus 100 described above is used to manufacture the second nonwoven fabric 10. The manufacturing method of this embodiment includes: a web forming process, forming a first web 11 and a second web 12, and stacking the two webs 11 and 12 to obtain a laminated web 13; a hot air treatment process, blowing hot air onto the laminated web 13 under the conditions described later (1) to (3) to obtain a first nonwoven fabric 14; and a calendering process, performing calendering processing on the first nonwoven fabric 14 to obtain the second nonwoven fabric 10.

[0034] In the web forming process, firstly, web 11 and web 12 are manufactured. Raw material fibers such as heat-fusion fibers are split using a fiber splitting machine, and the split raw material fibers are then formed into webs using the aforementioned guiding machines 21 and 22, thereby manufacturing these webs 11 and 12. Web 11 and web 12 are sheet-like materials in the stage before the formation of nonwoven fabric, in which no heat fusion occurs between the fibers.

[0035] Wire mesh 11 and wire mesh 22 contain thermoplastic fibers. Thermoplastic fibers are fibers that fuse together due to heat, using thermoplastic resins as raw materials. Examples of thermoplastic resins include polyolefins such as polyethylene (PE) and polypropylene (PP); polyesters such as polyethylene terephthalate (PET); polyamides such as nylon 6 and nylon 66; and alkyl polyacrylates, alkyl polymethacrylates, polyvinyl chloride, and polyvinylidene chloride, etc., and one or more of these resins can be used alone or in combination. Furthermore, as thermoplastic fibers, composite fibers containing two or more components, including low-melting-point and high-melting-point components, can be used. Examples of such composite fibers include core-sheath type and parallel type fibers with a core-sheath structure comprising a core and a sheath. Core-sheath type composite fibers can be concentric or eccentric.

[0036] From the viewpoint of more reliably ensuring the strength of nonwoven fabrics 10 and 14, the heat-fusion fibers preferably contain PE as a constituent resin, more preferably contain PE at least on the surface, and even more preferably are formed of PE. For example, in the case where the heat-fusion fibers contain fibers having a core-sheath structure, the resin component of the core is preferably PET and the resin component of the sheath is preferably PE.

[0037] From the same point of view as above, the content of heat-fused fibers in the first web 11 is preferably at least 50% by mass, more preferably at least 90% by mass, and less than 100% by mass relative to the total mass of the first web 11.

[0038] The content of heat-fusion fibers in the second mesh 12 is preferably within the same range as the content of heat-fusion fibers in the first mesh 11.

[0039] Web 11 and Web 22 may contain other fibers in addition to the heat-fusion fibers. Examples of other fibers include fibers that do not fuse together with heat. Examples include pulp, cotton, rayon, lyocell, and Tencel. One or more of these fibers may be used alone or in combination.

[0040] The first nonwoven fabric 11 contains heat-fused fibers with a fiber diameter of 15 μm or less. Hereinafter, "heat-fused fibers with a fiber diameter of 15 μm or less" will also be referred to as fine fibers. The reason for using fine fibers as raw materials is to make the surfaces of the first nonwoven fabric 14 and the second nonwoven fabric 10 (especially the surface on the first layer side) feel good to the skin.

[0041] From the viewpoint of further improving the smoothness of nonwoven fabrics 10 and 14, the content of fine fibers in the first web 11 is preferably 25% or more, more preferably 30% or more, and practically 100% or less. The content of fine fibers can be adjusted by the amount of raw material fibers used in the manufacture of the first web 11. The method for determining the content of fine fibers will be described later.

[0042] From the viewpoint of further improving the strength and softness of nonwoven fabrics 10 and 14, it is preferable that the average fiber diameter of the fibers constituting the second web 12 is greater than the average fiber diameter of the fibers constituting the first web 11 (second web 12 > first web 11).

[0043] From the same point of view as above, the difference between the average fiber diameter of the fibers constituting the first web 11 and the average fiber diameter of the fibers constituting the second web 12 is preferably 0.5 μm or more, more preferably 1 μm or more, and preferably 25 μm or less, more preferably 15 μm or less. It is also preferably 0.5 μm or more and 25 μm or less, more preferably 1 μm or more and 15 μm or less.

[0044] From the viewpoint of further improving the smoothness of the first layer side surface of the nonwoven fabrics 10 and 14, the first web 11 containing fine fibers preferably has an average fiber diameter of 5 μm or more, more preferably 8 μm or more, and preferably 20 μm or less, more preferably 15 μm or less. It is also preferred that the first web 11, which contains fine fibers, has an average fiber diameter of 5 μm or more and 20 μm or less, more preferably 8 μm or more and 15 μm or less.

[0045] From the viewpoint of further improving the skin feel and strength of nonwoven fabrics 10 and 14, the average fiber diameter of the fibers constituting the second web 12 is preferably 5 μm or more, more preferably 8 μm or more, and preferably 30 μm or less, more preferably 20 μm or less. It is also preferred that the average fiber diameter of the fibers constituting the web 12 is 5 μm or more and 30 μm or less, more preferably 8 μm or more and 20 μm or less.

[0046] The proportion of fine fibers, the average fiber diameter of the fibers constituting the first web 11, and the average fiber diameter of the fibers constituting the second web 12 were determined by magnified observation of each web using an electron microscope. Specifically, for each web to be measured, a 10mm × 30mm area was cut out along the entire thickness direction using a sharp razor, and this area was designated as the measurement sample. A 500μm × 400μm area (observation area) was photographed at 200x magnification using a scanning electron microscope (SEM, JCM-6000Plus, manufactured by Nippon Electronics Co., Ltd. All SEMs mentioned in this application specification refer to this product). In this SEM-based imaging, the focus was on the fibers located on the outermost surface of the measurement sample's field of view. A total of five SEM images were obtained from five different locations on each side of one measurement sample. The fiber diameter and the proportion of fine fibers were determined from each of the obtained SEM images using the following method. First, in the SEM image, select "Focused Fibers". "Focused Fibers" are fibers whose outlines are not blurred within the observation area. Then, for each focused fiber, arbitrarily select the portion other than the thermally fused portion where the fibers fuse together. Next, draw a line orthogonal to the length direction of the selected fiber portion, and measure the fiber diameter along this line. In this measurement, for the focused fibers, the measurement is performed at a position where the diameter line showing the diameter length (orthogonal to the fiber's length direction) intersects with the line showing the fiber's outline. Then, count the number of fine fibers with a diameter of 15 μm or less, and calculate the percentage (%) of the ratio of the number of such fine fibers in the SEM image to the number of focused fibers, i.e., "number of fine fibers / number of focused fibers". Calculate this ratio for each of the five SEM images obtained from the sample, and set their average as the "fiber content ratio". In addition, the average fiber diameter of the focused fibers is set as either "the average fiber diameter of the fibers constituting the first web 11" or "the average fiber diameter of the fibers constituting the second web".

[0047] Using a nonwoven fabric formed from the first web 11 and the second web 12, and measuring the average fiber diameter and the proportion of fine fibers constituting these webs 11 and 12, a 10mm × 30mm area (viewed from above) is cut from the nonwoven fabric along its thickness using a sharp razor, and the resulting material is designated as a measurement sample. In this case, the first layer side (first web 11 side) and the second layer side (second web 12 side) of the measurement sample are magnified and observed using the method described above.

[0048] From the viewpoint of further improving the fluffiness of nonwoven fabrics 10 and 14, the unit area weight of the first web 11 and the second web 12 is preferably within the following range.

[0049] The unit area weight of the first mesh 11 is preferably lower than that of the second mesh 12 (first mesh 11 < second mesh 12). Specifically, the difference between the unit area weight of the first mesh 11 and the unit area weight of the second mesh 12 is preferably 0.5 g / m². 2 The above, more preferably 1g / m 2 In addition, the preferred value is 10g / m³. 2 The preferred value is 8g / m 2 The following values ​​are preferred, and more preferably 0.5 g / m 2 Above and 10g / m 2 The following is more preferably 1g / m 2 Above and 8g / m 2 the following.

[0050] The preferred unit area weight of the first mesh 11 is 5g / m². 2 The above, preferably 7g / m 2 In addition, the preferred value is 15g / m³. 2 The following is more preferably 12g / m 2 The following, and preferably 5g / m 2 Above and 15g / m 2 The preferred value is 7g / m 2 Above and 12g / m 2 the following.

[0051] The preferred unit area weight of the second mesh 12 is 5g / m². 2 The above, preferably 7g / m 2 In addition, the preferred value is 25g / m³. 2 The following is more preferably 20g / m 2 The following, and preferably 5g / m 2 Above and 25g / m 2 The preferred value is 7g / m 2 Above and 20g / m 2 the following.

[0052] From the viewpoint of improving the softness, fluffiness and smoothness of nonwoven fabrics 10 and 14, the fineness of the first web 11 and the second web 12 is preferably within the following range.

[0053] The fineness of the first mesh 11 is preferably lower than that of the second mesh 12 (first mesh 11 < second mesh 12). Specifically, the ratio of the fineness of the second mesh to the fineness of the first mesh (fineness of the second mesh / fineness of the first mesh) is preferably 1.1 or more, more preferably 1.2 or more, even more preferably 1.3 or more, and preferably 3 or less, more preferably 2.5 or less, even more preferably 2.0 or less, and also preferably 1.1 or more and 3.0 or less, more preferably 1.1 or more and 2.5 or less, and even more preferably 1.3 or more and 2.0 or less.

[0054] The fineness of the first mesh 11 is preferably 0.5 dtex or more, more preferably 1.0 dtex or more, and even more preferably 5.0 dtex or less, more preferably 4.0 dtex or less, and even more preferably 0.5 dtex or more and 5.0 dtex or less, and even more preferably 1.0 dtex or more and 4.0 dtex or less.

[0055] The fineness of the second mesh 12 is preferably 1.0 dtex or more, more preferably 1.5 dtex or more, and even more preferably 8.0 dtex or less, more preferably 5.0 dtex or less, and even more preferably 1.0 dtex or more and 8.0 dtex or less, and even more preferably 1.5 dtex or more and 5.0 dtex or less.

[0056] The fineness of the fiber can be determined using the following method. Cut the first mesh 11 into 50mm × 100mm pieces (area 5000mm²). 2 A rectangular sample for testing was prepared. Then, a cross-sectional observation was performed on the sample. Ten standard fibers, spaced 0.05 mm apart along the thickness direction from one of the two main faces of the sample, were used as subjects. The fiber thickness was measured using a scanning electron microscope at 200x magnification, and the average fiber thickness Dn (μm) was calculated. Next, the resin composition of the standard fibers at 0.05 mm intervals along the thickness direction from the aforementioned face of the sample was determined, and the theoretical fiber density Pn (g / cm³) was calculated using differential scanning calorimetry (DSC). 3 Based on the obtained average fiber thickness Dn (μm) and theoretical fiber density Pn (g / cm³), 3 ), calculate the weight (g) of every 10,000 m of fiber length, and set the calculated value as the fineness (dtex) of the first web 11.

[0057] The fineness of the second mesh 12 can also be determined using the same method as the fineness of the first mesh 11.

[0058] Using a nonwoven fabric formed from the first web 11 and the second web 12, and measuring the fineness of the fibers constituting these webs 11 and 12 in the nonwoven fabric, a 50mm × 100mm area (area 5000mm²) is cut from the nonwoven fabric along its thickness direction using a sharp razor. 2 The obtained material is used as the test sample. In this case, a standard fiber located at a 0.05 mm interval along the thickness direction from the non-blown surface of the first layer (first mesh 11) of the test sample is used as the object. The average fiber thickness Dn (μm) and the theoretical fiber density Pn (g / cm³) of the fiber are determined using the method described above. 3 The fineness (dtex) of the first mesh 11 is calculated based on these values. In addition, except that a standard fiber located at a distance of 0.05 mm from the blown surface of the second layer (second mesh 12) of the test sample along the thickness direction is used as the object, the fineness (dtex) of the second mesh 12 is calculated using the same method as that of the first mesh 11.

[0059] In the web forming process, the first web 11 and the second web 12 are merged during transport, and the second web 12 is stacked on the first web 11 to obtain the laminated web 13 (see reference). Figure 1 The resulting laminated mesh 13 is used in the subsequent hot air treatment process.

[0060] The hot air treatment process is a process of blowing hot air into the laminated web 13 to fuse the intersections of the fibers constituting the laminated web 13 to produce the first nonwoven fabric 14. In the hot air treatment process, hot air is blown into the laminated web 13 under the following conditions (1) to (3).

[0061] (1) When the melting point of the resin with the lowest melting point among the resins that constitute the thermo-fusion fibers contained in the laminated mesh 13 is set as Mp, the temperature T1 of the non-blowing surface of the mesh (laminated mesh 13) is above Mp and below Mp+15℃.

[0062] (2) The temperature T1 is lower than the temperature T2 of the hot air blowing surface of the mesh (layered mesh 13) and the difference between temperature T1 and temperature T2 is more than 10°C and less than 35°C.

[0063] (3) The supply speed of hot air is above 0.30 m / s and below 0.60 m / s.

[0064] In the hot air treatment process that satisfies the conditions (1) to (3) above, while suppressing excessive flattening of the thickness of the laminated web 13, the constituent fibers (thermally fused fibers) of the laminated web 13 are moderately thermally fused together. As a result, the thickness of the first nonwoven fabric 14 is well maintained, thus obtaining a soft and fluffy feel. In addition, in the above-mentioned hot air treatment process, since the excessive thermal fusion of the fine fibers contained in the first web 11 can be suppressed, the non-blowing surface (the surface on the side of the first web 11) of the first nonwoven fabric 14 forms a smooth feel due to the fine fibers. Thus, in the manufacturing method of this embodiment, a nonwoven fabric 14 with a soft, fluffy feel and a smooth surface with excellent skin feel can be obtained. Furthermore, in the manufacturing method of this embodiment, since the constituent fibers of the laminated web 13 are moderately fused together, a soft nonwoven fabric 14 with excellent strength can be obtained.

[0065] On the other hand, if the conventional hot air method is used to manufacture hot air nonwoven fabric from the laminated web 13 containing fine fibers, the original smooth feel of the fine fibers is reduced due to excessive melting of the fine fibers, thereby impairing the hand feel of the hot air nonwoven fabric. In addition, the hot air in the hot air method excessively flattens the web, thereby impairing its fluffiness.

[0066] The conditions (1) to (3) above will be described in detail below.

[0067] The condition in (1) above is expressed by the following formula (i).

[0068] Mp≤T1≤Mp+15℃···(i)

[0069] Mp: The melting point of the resin with the lowest melting point among the resins constituting the thermoforming fibers contained in the mesh (laminated mesh 13).

[0070] T1: Temperature of the non-blown surface of the mesh (laminated mesh 13)

[0071] Mp is the melting point of the resin with the lowest melting point among the resins constituting the thermoforming fibers contained in the laminated web 13. When the thermoforming fibers of the laminated web 13 are composed of multiple resins, such as core-sheath type composite fibers, Mp is set as the melting point of the resin with the lowest melting point among these resins. In the case of resins for which there is no clearly defined melting point, Mp is set as the softening point.

[0072] For temperature T1, for ease of temperature measurement, it is set as the temperature P1 located 10 cm away from the non-blowing conveying surface f1 of the permeable conveying member 31 of the hot air treatment conveying path r1 along the normal direction (refer to...). Figure 2The "hot air handling conveying path r1" is the path of the laminated mesh 13 formed by the permeable conveying member 31 that faces the hot air supply port of the blower 32. The "non-blowing conveying surface f1" is the side of the permeable conveying member 31 opposite to the side facing the hot air supply port of the blower 32. The temperature at the aforementioned position P1 is equivalent to the temperature T1 of the non-blowing surface of the laminated mesh 13.

[0073] Temperature T1 affects the degree of thermal fusion and hand feel of the non-blown surface (the surface on the first layer side) of nonwoven fabrics 10 and 14. Under the conditions described in (1) above, setting temperature T1 to Mp or higher ensures the strength of the non-blown surface, and setting temperature T1 to Mp+15°C or lower suppresses excessive thermal fusion of the fine fibers, resulting in a good hand feel for the non-blown surface. From the viewpoint of further improving this hand feel, under the conditions described in (1) above, the difference between temperature T1 and Mp is 15°C or lower, preferably 0.5°C or higher, more preferably 1°C or higher, and preferably 10°C or lower, more preferably 5°C or lower, and preferably 0.5°C or higher and 15°C or lower, more preferably 1°C or higher and 10°C or lower, and even more preferably 1°C or higher and 5°C or lower.

[0074] The condition in (2) above is expressed by the following formula (ii).

[0075] 10℃≤T2-T1≤35℃···(ii)

[0076] T2: Temperature of the blowing surface of the mesh (laminated mesh 13)

[0077] In the above equation (ii), T2 > T1 is taken as an premise.

[0078] For temperature T2, for ease of temperature measurement, let it be the temperature at position P2 10cm away from the blowing surface f2 of the permeable conveying member 31 along the normal direction of the hot air treatment conveying path r1 (refer to...). Figure 2 "Blowing and conveying surface f2" is the surface of the permeable conveying member 31 facing the hot air supply port of the blower 32. The temperature of the aforementioned position P2 is equivalent to the temperature T2 of the blowing surface of the laminated mesh 13.

[0079] In the measurement of temperatures T1 and T2, known measuring mechanisms such as thermocouple-type temperature sensors and temperature displays are used. The measurement of temperatures T1 and T2 is performed using the following method: When the hot air processing conveying path r1 is divided into four equal sections along the conveying direction X, starting from the upstream side, into four sections: section 1 S1, section 2 S2, section 3 S3, and section 4 S4, the temperatures at positions P1 and P2, which are the midpoints of the conveying path lengths of each of these four sections S1, S2, S3, and S4, are measured. Then, the average temperature at position P1 and the average temperature at position P2 of the four sections S1, S2, S3, and S4 are calculated and set as temperatures T1 and T2.

[0080] Temperature T2 affects the thermal fusion between the constituent fibers of nonwoven fabrics 10 and 14. Under the conditions described in (2) above, the temperature difference (T2-T1) between T1 and T2 is 10°C or more, thereby ensuring the overall strength of nonwoven fabrics 10 and 14 by thermal fusion between the constituent fibers of the laminated web 13. At the same time, the temperature difference (T2-T1) between T1 and T2 is 35°C or less, thereby suppressing excessive thermal fusion of the constituent fibers on the blowing surface side of the laminated web 13. As a result, nonwoven fabrics 10 and 14 can be endowed with strength and softness. From the viewpoint of more reliably ensuring the strength and softness of nonwoven fabrics 10 and 14, under the conditions described in (2) above, the temperature difference (T2-T1) between T1 and T2 is preferably 12°C or more, more preferably 15°C or more, and preferably 30°C or less, more preferably 25°C or less. It is also more preferably 12°C or more and 30°C or less, more preferably 15°C or more and 25°C or less.

[0081] Under the conditions described in (3) above, the supply speed of hot air in the hot air handling conveying path r1 is set to be above 0.30 m / s and below 0.60 m / s.

[0082] The supply speed of hot air affects the thickness of nonwoven fabrics 10 and 14. Under the conditions described in (3) above, the supply speed of hot air is set to 0.30 m / s or more, thereby allowing the constituent fibers of the laminated web 13 to be moderately thermally fused, and the supply speed of hot air is set to 0.60 m / s or less, thereby maintaining the original thickness of the laminated web 13 well. As a result, nonwoven fabrics 10 and 14 can be given a cushioning and fluffy feel. From the viewpoint of more reliably ensuring the cushioning and fluffy feel of nonwoven fabrics 10 and 14, under the conditions described in (3) above, the supply speed of hot air is preferably 0.33 m / s or more, more preferably 0.35 m / s or more, and preferably 0.57 m / s or less, more preferably 0.50 m / s or less, and preferably 0.33 m / s or more and 0.57 m / s or less, more preferably 0.35 m / s or more and 0.50 m / s or less.

[0083] It should be noted that the hot air supply speed is measured at a position P2 10 cm away from the blowing and conveying surface f2 of the permeable conveying member 31 along the normal direction in the hot air handling conveying path r1 using a known anemometer (such as MODEL6162 or MODEL0203 of ANEMOMASTER manufactured by Kanomax Co., Ltd. of Japan).

[0084] As previously described, the first web 11 of the laminated web 13 contains fine fibers. From the viewpoint of further suppressing excessive thermal fusion of the fine fibers and ensuring moderate thermal fusion between the constituent fibers of the second web 12, the hot air treatment process preferably blows hot air onto the laminated web 13 from the second web 12 side. This allows for a smoother non-blown surface of the laminated web 13 and more reliably ensures the strength of the first nonwoven fabric 14.

[0085] In this embodiment, the hot air treatment process involves continuously supplying the laminated mesh 13 to the annular, breathable conveying member 31 while simultaneously blowing hot air onto the laminated mesh 13. Thus, in the manufacturing method of this embodiment, the hot air treatment process is performed continuously while the laminated mesh 13 is continuously conveyed. The aforementioned hot air treatment conveying path r1 is included in a portion of the annular path r2 of the breathable conveying member 31 (see reference). Figure 2 ).

[0086] When the manufacturing apparatus 100 has just started operating, the temperature of the breathable conveying member 31 is basically at room temperature. However, as operation continues, the temperature of the breathable conveying member 31 rises due to the hot air from the blower 32. For this reason, the temperature T2 also rises. From the viewpoint of further suppressing the excessive rise of temperature T2 in the hot air treatment process and making the surface of the nonwoven fabrics 10 and 14 smoother, it is preferable to cool the breathable conveying member 31, which has been heated by continuous hot air blowing, before supplying the laminated web 13 in the hot air treatment process. This cooling process will also be referred to as the "cooling process" below. In this embodiment, the cooling process is performed in the annular path r2 of the breathable conveying member 31 using a cooling device 50 located in a path other than the hot air treatment conveying path r1. For example, the cooling device 50 blows cold air onto the breathable conveying member 31 before it enters the hot air treatment conveying path r1, thereby cooling the breathable conveying member 31. Additionally, as a cooling device 50, any one of the conveying rollers 34a, 34b, 34c, and 34d can be designated as a cooling roller. The cooling roller contains a refrigerant such as water or gas inside.

[0087] From the same perspective as above, the temperature of the breathable conveying member 31 after the cooling process and before the hot air treatment process is preferably 25°C or higher, more preferably 30°C or higher, and preferably 130°C or lower, more preferably 120°C or lower. Furthermore, it is preferably 25°C or higher and 130°C or lower, more preferably 30°C or higher and 120°C or lower. At the entrance of the hot air treatment conveying path r1, the temperature of the breathable conveying member 31 after the cooling process and before the hot air treatment process is measured using a known measuring mechanism such as a thermocouple-type temperature sensor or a temperature display.

[0088] From the same point of view as above, the temperature difference between Mp and the temperature of the breathable conveying member 31 cooled by the cooling process (Mp - temperature of the breathable conveying member 31 cooled by the cooling process) is preferably greater than 0°C, more preferably 10°C or more, and preferably 105°C or less, more preferably 90°C or less. It is also preferably greater than 0°C and less than 105°C, more preferably 10°C or more and less than 90°C.

[0089] The first nonwoven fabric 14 is obtained using the above hot air treatment process. As mentioned above, the first nonwoven fabric 14 is a nonwoven fabric with excellent skin feel and strength. However, in the manufacturing method of this embodiment, a calendering process is further performed to apply a calendering process to the first nonwoven fabric 14. Calendering can smooth the surface of the nonwoven fabric, further improving its smoothness when in contact with the skin. In addition, it can increase the density of the constituent fibers of the nonwoven fabric, further improving its softness. As mentioned above, the thickness of each of the first web 11 and the second web 12 of the first nonwoven fabric 14 is well maintained, resulting in a fluffy feel. For this reason, even if the first nonwoven fabric 14 is calendered, the thickness is easily restored, so the second nonwoven fabric 10 obtained after the calendering process also has a good fluffy feel.

[0090] The calendering process can be performed in two or more stages, or in one stage, preferably in at least one stage. From the viewpoint of further improving the smoothness and softness of the surface of the second nonwoven fabric 10, the calendering process is preferably performed in multiple stages.

[0091] In the calendering process of this embodiment, a two-stage calendering process is applied to the first nonwoven fabric 14. The first stage of calendering is performed by introducing the first nonwoven fabric 14 between the calendering roller 41 and the first resin roller 42. The second stage of calendering is performed by introducing the first nonwoven fabric 14 between the calendering roller 41 and the second resin roller 43. In both the first and second stages of calendering, the first layer of the first nonwoven fabric 14 is brought into contact with the calendering roller 41.

[0092] The calendering process is preferably performed under the following conditions (C1).

[0093] Temperature: 25℃

[0094] Linear voltage: 20 N / cm or higher and 500 N / cm or lower

[0095] Rollers: A pair of calendering rollers are used, one of which is a calendering roller with a metal surface and the other is a resin roller with a surface D hardness (JIS K6253) of 40 degrees or higher and 100 degrees or lower.

[0096] When calendering is performed in multiple stages during the calendering process, it is preferable to satisfy condition (C1) in any one of the calendering processes. That is, it is preferable to perform at least one stage of the multi-stage calendering process under the aforementioned condition (C1).

[0097] By performing calendering that satisfies condition (C1), the surface of the first layer abutting against the calendering roller 41 becomes smoother, and the softness of the second nonwoven fabric 10 is further improved. Furthermore, excessive compression of the fibers is further suppressed, further maintaining the fluffiness of the second nonwoven fabric 10. This is because the first layer side facing the calendering roller 41 is clamped during the calendering process, causing the fibers contained in the first layer to deform and flatten, and thus becoming denser due to this clamping. Additionally, the clamping exerts a "rubbing" effect on the nonwoven fabric 14, causing some of the fiber bonding points to deform or break, making the nonwoven fabric 14 softer. For the fibers contained in the second layer facing the resin rollers 42 and 43, since the resin rollers 42 and 43 are made of soft material, they are less susceptible to clamping pressure, less prone to deformation, and less prone to becoming denser. The long axis direction of the cross-section of the fibers contained in the flattened first layer is oriented along the planar direction of the nonwoven fabric 14.

[0098] The calendering roll 41 can be a smooth roll with a mirror finish, or it can be a roll with fine textures or irregularities. The calendering roll 41 is preferably a metal roll.

[0099] For example, rollers made of resins such as hard rubber, silicone rubber, polyurethane rubber, NBR, and EPDM can be used as the first resin roller 42 and the second resin roller 43.

[0100] Under condition (C1), the D hardness (JIS K6253) of the constituent resin on the surface of one or both of the first resin roller 42 and the second resin roller 43 is preferably 40 degrees or more and 100 degrees or less, more preferably 70 degrees or more and 95 degrees or less.

[0101] Under condition (C1), calendering rolls 41 and / or resin rolls 42, 43 can be used in a heated state or in a non-heated state. When used in a non-heated state, calendering is performed at room temperature (25°C).

[0102] Under condition (C1), the linear pressure of the calendering process is preferably 20 N / cm or more and 500 N / cm or less. From the viewpoint of further improving the fluffiness of the second nonwoven fabric 10, it is more preferably 20 N / cm or more and 300 N / cm or less. In addition, the calendering roller 41 and / or resin rollers 42, 43 can be used in a heated or unheated state; however, from the viewpoint of simultaneously improving fluffiness and hand feel, it is preferred to use them in the unheated state.

[0103] In the case of performing a two-stage calendering process as in this embodiment, both stages may satisfy condition (C1), or only one stage may satisfy condition (C1). From the viewpoint of making the surface of the first layer of the second nonwoven fabric 10 smoother, it is preferable that the second stage calendering process satisfies condition (C1) and that the linear pressure of the first stage calendering process is higher than that of the second stage. From the same viewpoint as above, the linear pressure of the first stage calendering process is preferably 50 N / cm or more and 700 N / cm or less, more preferably 100 N / cm or more and 300 N / cm or less.

[0104] From the viewpoint of reliably obtaining a fluffy feel, it is preferable to further apply an additional heat treatment or calendering process to the second nonwoven fabric 10 after calendering, so that the compression work WC is 1.2 mN·cm / cm. 2 Above and 1.6 mN·cm / cm 2 The following is a preferred method: An additional process is applied to the second nonwoven fabric 10 such that the compression work WC of the second nonwoven fabric 10 is 1.2 mN·cm / cm. 2 Above and 1.6 mN·cm / cm 2 the following.

[0105] [Determination of compression work]

[0106] The known amount of compression work can usually be expressed by the measured value of the KES (KAWABATA EVALUATION SYSTEM) manufactured by Kato Tech Co., Ltd. (Reference: Standardization and Analysis of Hand Feel Evaluation (2nd Edition), author: Kawabata Sueo, published July 10, 1955). The compression work is measured using the KES-G5 compression testing apparatus manufactured by Kato Tech Co., Ltd. First, the nonwoven fabric to be measured is mounted on the test stand of the compression testing apparatus, and a 2cm² area is applied... 2 Compression is performed between circular flat steel plates. In this compression process, the compression speed is set to 0.2 cm / sec, and the maximum compression load is set to 2450 mN / cm². 2 The compression work (WC) is expressed by the following formula (1), with the unit being "mN·cm / cm". 2In the following formula, Tm represents 2450 mN / cm². 2 The thickness under a load of (24.5 kPa) is T0, which represents 4.902 mN / cm. 2 The thickness under a load of (49Pa). Additionally, P in equation (1) below... a The measured load during the compression process (mN / cm) 2 The higher the value of the compression work (WC), the fluffier the feel.

[0107] [Number 1]

[0108]

[0109] When applying calendering to the second nonwoven fabric 10 in the additional process, the conditions can be the same as those in the aforementioned calendering process. For example, calendering can be performed in one or more stages in the additional process.

[0110] When heat treatment is applied to the second nonwoven fabric 10 in an additional process, it is preferable to heat the second nonwoven fabric 10 at a temperature lower than the melting point Mp of the heat-bonding fibers contained in the second nonwoven fabric 10. Examples of methods for this heat treatment include blowing hot air onto the second nonwoven fabric 10 and heating the second nonwoven fabric 10 in a windless environment and at a specified temperature. In the above-described method of blowing hot air, the aforementioned hot air treatment unit 30 can be used with the condition that the temperature T2 is lower than M.

[0111] The second nonwoven fabric 10 is obtained using the above manufacturing method. The second nonwoven fabric 10 and the first nonwoven fabric 14 obtained in the aforementioned hot air treatment process are each applicable to nonwoven fabric products. Nonwoven fabric products are products made of nonwoven fabric or products having nonwoven fabric as a constituent component. Examples of nonwoven fabric products broadly include absorbent items such as disposable diapers and sanitary napkins, warming devices such as goggles, surgical gowns, masks, cleaning sheets, and wiping sheets. The aforementioned "absorbent items" broadly include items used to absorb bodily fluids (urine, feces, menstrual blood, sweat, etc.) excreted from the human body, such as disposable diapers, sanitary napkins, menstrual underwear, and incontinence pads.

[0112] Absorbent articles typically have a liquid-permeable front sheet positioned relatively close to the wearer's skin, a liquid-impermeable, liquid-resistant, or hydrophobic back sheet positioned relatively away from the wearer's skin, and a liquid-retaining absorbent sandwiched between the two sheets. Absorbent articles may also have an outer packaging forming their outer surface.

[0113] When the first nonwoven fabric 14 and the second nonwoven fabric 10 are used as constituent components of an absorbent article, these nonwoven fabrics 10 and 14 are preferably used in constituent components that come into contact with the skin of a wearer or other user. In this case, it is more preferable to use them in such a way that the first layer side of the first nonwoven fabric 14 and the second nonwoven fabric 10 is the skin-contacting surface. Since the first layer side of these nonwoven fabrics 10 and 14 is flat and smooth, a good wearing experience can be obtained. Examples of constituent components that come into contact with the skin of a wearer or other user include front sheets, outer packaging, etc.

[0114] The first nonwoven fabric 14 and the second nonwoven fabric 10 are each manufactured as strips of nonwoven fabric with their length direction aligned with the conveying direction X (MD direction) (see reference). Figure 1 The direction orthogonal to the length direction (width direction) of these nonwoven fabrics 10 and 14 is the same as the direction orthogonal to the conveying direction X (CD direction). From the viewpoint of more reliably ensuring strength, the tensile strength in the MD direction of either or both of the manufactured first nonwoven fabric 14 and second nonwoven fabric 10 is preferably 10 N / 50 mm or more, more preferably 20 N / 50 mm or more, and preferably 100 N / 50 mm or less, more preferably 70 N / 50 mm or less. Moreover, it is preferably 10 N / 50 mm or more and 100 N / 50 mm or less, more preferably 20 N / 50 mm or more and 70 N / 50 mm or less. From the same point of view as above, the tensile strength in the CD direction of each of the manufactured first nonwoven fabric 14 and second nonwoven fabric 10 is preferably 4N / 50mm or more, more preferably 5N / 50mm or more, and preferably 15N / 50mm or less, more preferably 12N / 50mm or less. Furthermore, it is preferably 4N / 50mm or more and 15N / 50mm or less, more preferably 5N / 50mm or more and 12N / 50mm or less.

[0115] The methods for measuring tensile strength in the MD and CD directions are detailed in the "Measurement of Tensile Strength" section of the embodiments described later. In this "Measurement of Tensile Strength," if the size described later cannot be obtained when cutting the test sample, the length in the width direction is set to 50 mm, and the length in the length direction is shortened in 50 mm increments (e.g., 50 mm × 150 mm, or 50 mm × 100 mm) when cutting the test sample. In this case, the distance between the clamps of the tensile testing machine is 50 mm shorter than the length of the test sample in the length direction. Even if the length of the test sample in the length direction is changed in this way, the results of the tensile strength measurement can be directly compared.

[0116] From the viewpoint of suppressing pilling on the appearance and further improving the hand feel of the nonwoven fabric, the number of pilling fibers per unit area of ​​either or both of the manufactured first nonwoven fabric 14 and second nonwoven fabric 10 is preferably 20 or less, more preferably 10 or less, and most preferably 0. That is, from the above viewpoint, the fewer the number of pilling fibers per unit area, the more preferred. The method for measuring the number of fibers is described in detail in the embodiment described later, in the section on "Measurement of the Number of Pilling Fibers per Unit Area". In this section on "Measurement of the Number of Pilling Fibers per Unit Area", if it is not possible to cut a 10cm × 10cm measuring piece from the nonwoven fabric, the size of the measuring piece is set to 7cm × 7cm.

[0117] The present invention has been described above based on its preferred embodiments; however, the present invention is not limited to the above embodiments and can be appropriately modified. Furthermore, the above-described components can be appropriately combined.

[0118] For example, the manufacturing method of the above-described embodiment uses a laminated web 13 with a first web 11 and a second web 12 stacked together; however, a single-layer web can be used instead. In this case, the single-layer web contains fine fibers.

[0119] In addition, the manufacturing method of the above-described embodiment includes a cooling process; however, if the conditions of (1) to (3) above are met in the hot air treatment process, the cooling process may not be included.

[0120] Example

[0121] The present invention will be further described in detail below with reference to embodiments. However, the scope of the present invention is not limited to these embodiments.

[0122] [Example 1]

[0123] use Figure 1 The manufacturing apparatus 100 shown produces a second nonwoven fabric 10. First, a web-forming process is performed. The raw material fiber for the first web 11 is a thermoforming fiber formed from concentric core-sheath composite fibers (core-sheath ratio 50% by mass: 50% by mass) containing PET as the core component and PE as the sheath component. The raw material fiber for this first web 11 is a fine fiber with a diameter of 12.4 μm and a fineness of 1.3 dtex. The resin with the lowest melting point among the constituent resins (PE as the sheath component) has a melting point Mp of 130°C. This raw material fiber is fed into the first guide machine 21 to produce the first web 11 (weight per unit area 10 g / m²). 2 ).

[0124] The raw material fiber for the second web 12 is a thermoforming fiber formed from concentric core-sheath composite fibers (core-sheath ratio 50% by mass: 50% by mass) containing PET as the core component and PE as the sheath component. The raw material fiber of the second web 12 has a fiber diameter of 16.7 μm, a fineness of 2.0 dtex, and the lowest melting point resin (PE as the sheath component) among the constituent resins has a melting point Mp of 130°C. This raw material fiber is fed into the second guide machine 22 to produce the second web 12 (unit area weight 15 g / m²). 2 The average fiber diameter of the fibers constituting the first web 11 is 12.4 μm, and the average fiber diameter of the fibers constituting the second web 12 is 16.7 μm. The average fiber diameter was determined using the method described above. Subsequently, the second web 12 is laminated onto the first web 11 to produce a laminated web 13.

[0125] Then, the laminated wire 13 is subjected to a hot air treatment process using the hot air treatment unit 30. At this time, the surface of the second wire 12 side of the laminated wire 13 is designated as the blowing surface, and the surface of the first wire 11 side is designated as the non-blowing surface. The conditions of the hot air treatment process (temperature T1, the difference between temperature T1 and MP, temperature T2, the difference between temperature T1 and temperature T2, and the hot air supply speed) are shown in Table 1 below.

[0126] In the hot air treatment process, a cooling process is performed to cool the breathable conveying member 31 before supplying the laminated web 13. The temperature of the breathable conveying member 31 after the cooling process and before the hot air treatment process is 105°C. Using the above-described hot air treatment process, the first nonwoven fabric 14 is manufactured.

[0127] Then, a calendering process is performed using calendering section 40. The calendering process is as follows: Figure 1 As shown, the first nonwoven fabric 14 undergoes a two-stage calendering process. The calendering roller 41 is a smooth roller with a mirror-finished metal surface. For the surface of the first resin roller 42, a roller made of hard rubber with a D hardness (JIS K6253) of 40 to 100 degrees is used. The second resin roller 43 uses the same roller as the first resin roller 42. Both the first and second stages of calendering are performed at room temperature (25°C). The linear pressure values ​​for each stage of calendering are shown in Table 1 below. Using the above-described calendering process, the second nonwoven fabric 10 is manufactured.

[0128] [Examples 2-5]

[0129] In Examples 2 to 4, the second nonwoven fabric 10 was manufactured using the same method as in Example 1, except that the conditions of the hot air treatment process were different.

[0130] In addition, the first nonwoven fabric 14 obtained before the calendering process in Example 1 is set as the nonwoven fabric obtained in Example 5.

[0131] [Comparative Examples 1-4]

[0132] In Comparative Examples 1 to 3, except that the conditions of the hot air treatment process were different, the second nonwoven fabric 10 was manufactured using the same method as in Example 1.

[0133] In Comparative Example 4, except that the conditions of the hot air treatment process are different and the cooling process is not performed, the second nonwoven fabric 10 is manufactured using the same method as in Example 1.

[0134] 〔evaluate〕

[0135] Thickness, compression work WC, and tensile strength were measured for the second nonwoven fabric 10 of Examples 1-4 and Comparative Examples 1-4, and the first nonwoven fabric 14 of Example 5. The compression work WC was measured using the method described above. Furthermore, the average deviation (MMD) of the coefficient of friction was measured on the first layer side of each nonwoven fabric. The measurement results are shown in Table 1 below.

[0136] [Thickness Measurement]

[0137] The nonwoven fabric used for testing was subjected to a load of 4.9 N / cm. 2 Under this load, at least five locations were measured using a laser displacement gauge (Omron Corporation, high-precision displacement sensor ZS-LD80, trade name). The arithmetic mean of these measurements was taken as the thickness (mm).

[0138] [Determination of tensile strength]

[0139] The nonwoven fabrics in each embodiment and comparative example are strip-shaped nonwoven fabrics, with their length direction aligned with the conveying direction X (MD direction). Furthermore, the direction orthogonal to the length direction (width direction) of the nonwoven fabric is aligned with the direction orthogonal to the conveying direction X (CD direction). A 200mm long and 50mm wide piece is cut from the nonwoven fabric to be tested, and this is used as a test piece for tensile strength in the MD direction. The test piece is mounted between the clamps of a tensile testing machine (manufactured by Shimadzu Corporation, model "AUTOGRAPH AG-X") with its length direction aligned with the tensile direction. The distance between the clamps is set to 150mm. The mounted test piece is then stretched at a speed of 300mm / min, and a curve of tensile strength as the stretching distance changes is obtained. The maximum tensile strength is determined from the obtained curve. This maximum tensile strength is measured three times repeatedly, and the average value is taken as the tensile strength in the MD direction.

[0140] In addition, a measuring piece with a length of 50 mm and a width of 200 mm was cut from the nonwoven fabric to be tested, and this piece was used as a test piece for tensile strength in the CD direction. Apart from using this test piece, the tensile strength in the CD direction was measured using the same method as for the tensile strength in the MD direction.

[0141] [Determination of the mean deviation (MMD) of the coefficient of friction]

[0142] Using the surface of the 11th side of the first mesh (the surface of the first layer) as the measurement surface, a KES-FB4 surface testing machine (manufactured by KatoTech Co., Ltd.) was used to apply 5 kPa (50 gf / cm²) to the test object using a probe. 2 Under a load condition, the contact was moved horizontally for 3 cm at a constant speed of 0.1 cm / sec, and the average deviation (MMD) of the friction coefficient in the area where the contact moved was measured. Measurements were taken at three different points on the nonwoven fabric, and the average value was set as the average deviation (MMD) of the friction coefficient of the nonwoven fabric. The lower the average deviation (MMD) of the friction coefficient, the smoother the surface of the first layer side can be evaluated.

[0143] To evaluate the pilling of the second nonwoven fabric 10 of Examples 1-4 and Comparative Examples 1-4, and the first nonwoven fabric 14 of Example 5, the number of pilling fibers per unit area was measured. The measurement results are shown in Table 1 below.

[0144] [Determination of the number of fibers causing pilling per unit area]

[0145] Figure 3 This is a schematic diagram illustrating a method for determining the number of fibers that cause pilling in the fibers constituting a nonwoven fabric at 22°C and 65% RH. First, a 10cm × 10cm measurement piece 104 is cut from the nonwoven fabric to be measured using a sharp razor. Then, as... Figure 3 As shown in (a), the test piece 104 is folded and placed on an A4-sized black backing paper (not shown), as follows. Figure 3 (b) shows that an A4-sized black backing paper 101 with a hole 107 of 1 cm in length and 1 cm in width is placed on the measuring sheet 104 on the backing paper. At this time, it is arranged so that the crease 105 of the measuring sheet 104 can be observed through the hole 107 of the upper black backing paper. The backing paper arranged on the top and bottom of the measuring sheet 104 is, for example, "KENRAN (Black) 265g" from Fuji Kyowa Paper Co., Ltd. Figure 3For ease of explanation, the backing paper 101 is shown in white. Then, two 50g weights 102 are placed on the backing paper 101 positioned on the measuring piece 104. At this time, the weights 102 are placed on the crease 105 of the measuring piece 104, and at positions 5cm away from the two side edges of the hole 107 in the backing paper 101 positioned on the measuring piece 104, respectively, in the direction along the crease 105. This brings the measuring piece 104 to a fully folded state. Then, as... Figure 3 (c) shows the observation of the hole 107 in the backing paper at 30x magnification using a microscope (Keyence VHX-900, Inc.). Through this observation, the number of fibers whose tips are above the imaginary line 108 is counted as the number of fibers causing pilling. The imaginary line 108 is obtained by moving 1 mm parallel upwards from the crease 105 of the measuring sheet 104. In the case where there are fibers 106a that cross the imaginary line 108 twice (see [reference]). Figure 3 (c)], the fiber is counted as 2. Figure 3 In the example shown in (c), there are 4 fibers that cross the imaginary thread 108 once and 1 fiber 106a that crosses the imaginary thread 108 twice. Since the fiber 106a that crosses twice is counted as 2 fibers, the number of fibers that cause pilling is 6. The number of fibers that cause pilling is counted on 9 test pieces cut from the nonwoven fabric to be measured, and their average (rounded to an integer) is taken as the number of fibers that cause pilling per unit area (1cm×1cm). The face of the first web 11 side (the face of the first layer side) is taken as the test face.

[0146] In addition, sensory evaluations were conducted on the softness and fluffy feel of the second nonwoven fabric 10 of Examples 1-4 and Comparative Examples 1-4, and the first nonwoven fabric 14 of Example 5. The evaluation results are shown in Table 1 below.

[0147] [Evaluation of softness and fluffy texture]

[0148] Test pieces were prepared by cutting 10cm x 10cm pieces of the nonwoven fabric to be evaluated. Three adult males familiar with the feel of nonwoven fabrics served as evaluation panel members. The first layer side (the side facing the 11th layer of the first web) was used as the measurement surface. The softness and fluffiness of the test piece were evaluated by having the evaluation panel members touch it. Specifically, evaluations were conducted on a five-point scale from 1 to 5, with 5 representing the highest score. The method of contact with the test piece was not specified; each evaluation panel member freely touched the test piece to provide their evaluation. The average score from the three evaluation panel members was rounded to one decimal place. The evaluation results are presented in Table 1 below.

[0149] [Table 1]

[0150]

[0151] As shown in Table 1, the nonwoven fabrics of Examples 1-5 were found to be thicker and had a larger compression work (WC) compared to the nonwoven fabrics of Comparative Examples 1, 3, and 4. Furthermore, the tensile strength in the MD direction of the nonwoven fabrics of Examples 1-5 was 40.0 N or more, and the tensile strength in the CD direction was 6.4 N or more. The nonwoven fabric of Example 5 was not only thicker than the nonwoven fabric of Comparative Example 2, but also had less fuzzing, resulting in a superior appearance and feel against the skin.

[0152] Compared with the nonwoven fabrics of Comparative Examples 1-4, the nonwoven fabrics of Examples 1-5 have a smaller average deviation (MMD) of the friction coefficient on the first layer side. This result shows that the surface of the first layer side of the nonwoven fabrics of Examples 1-5 is smooth.

[0153] The number of fibers causing pilling per unit area on the first layer side of the nonwoven fabrics in Examples 1 to 5 is less than 9, indicating that there is little pilling on the surface.

[0154] The sensory evaluation of the softness of the nonwoven fabrics in Examples 1 to 5 was 5.3 or higher, and the sensory evaluation of the fluffy feel was 4.6 or higher.

[0155] The results above show that the nonwoven fabrics of Examples 1-5 have excellent overall skin feel, such as smoothness, softness and fluffiness, and compared with the nonwoven fabrics of Comparative Examples 1-4, they have a good balance between skin feel and strength.

[0156] Industrial availability

[0157] According to the nonwoven fabric manufacturing method of the present invention, a nonwoven fabric containing fibers with small diameter and excellent skin feel and strength can be obtained.

Claims

1. A method for manufacturing a nonwoven fabric, hot air is blown to a web containing heat-fusible fibers having a fiber diameter of 15 μm or less to fuse the intersections of the fibers constituting the web: (1) when the melting point of the resin having the lowest melting point among the resins constituting the heat-fusible fibers is set as Mp, the temperature Tl of the side of the web opposite to the side on which the hot air is blown is Mp or higher and Mp + 15°C or lower, (2) the temperature Tl is lower than the temperature T2 of the side on which the hot air is blown to the web and the difference between the temperature Tl and the temperature T2 is 10°C or higher and 35°C or lower, (3) the supply speed of the hot air is 0.30 m / sec or higher and 0.60 m / sec or lower.

2. The method for manufacturing a nonwoven fabric according to claim 1, wherein the web has a first web and a second web, the first web contains heat-fusible fibers having a fiber diameter of 15 μm or less.

3. The method for manufacturing a nonwoven fabric according to claim 2, wherein the content ratio of the heat-fusible fibers having a fiber diameter of 15 μm or less in the first web is 25% or higher and 100% or lower.

4. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the average fiber diameter of the fibers constituting the second web is larger than the average fiber diameter of the fibers constituting the first web.

5. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the difference between the average fiber diameter of the fibers constituting the first web and the average fiber diameter of the fibers constituting the second web is 0.5 μm or higher and 25 μm or lower.

6. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the average fiber diameter of the fibers constituting the first web is 5 μm or higher and 20 μm or lower.

7. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the average fiber diameter of the fibers constituting the second web is 5 μm or higher and 30 μm or lower.

8. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the weight per unit area of the first web is lower than the weight per unit area of the second web.

9. The method for manufacturing a nonwoven fabric according to claim 8, wherein The difference between the weight per unit area of the first web and the weight per unit area of the second web is 0.5 g / m 2 The above and 10 g / m 2 The following.

10. The method for manufacturing a nonwoven fabric according to claim 8, wherein The weight per unit area of the first web was 5 g / m 2 The weight per unit area of the first web was 5 g / m 2 The weight per unit area of the first web was 5 g / m 11. The method for manufacturing a nonwoven fabric according to claim 8, wherein The weight per unit area of the second web is 5 g / m 2 The weight per unit area of the second web is 5 g / m 2 The weight per unit area of the second web is 5 g / m 12. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the fineness of the first web is 0.5 dtex or higher and 5.0 dtex or lower.

13. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the fineness of the second web is 1.0 dtex or higher and 8.0 dtex or lower.

14. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the ratio of the fineness of the second web to the fineness of the first web, i.e., the fineness of the second web / the fineness of the first web, is 1.1 or higher and 3.0 or lower.

15. The method for manufacturing a nonwoven fabric according to claim 2 or 3, wherein the hot air is blown from the side of the second web.

16. The method for manufacturing a nonwoven fabric according to claim 1 or 2, wherein in the condition of the (1), the difference between the temperature Tl and Mp is 0.5°C or higher and 15°C or lower.

17. The nonwoven fabric production method according to claim 1 or 2, wherein In the condition of the (2), the difference between the temperature Tl and the temperature T2, i.e., T2-Tl is 12°C or more and 30°C or less.

18. The nonwoven fabric production method according to claim 1 or 2, wherein In the condition of the (3), the supply speed of the hot air is 0.33 m / sec or more and 0.57 m / sec or less.

19. The nonwoven fabric production method according to claim 1 or 2, which has a step of continuously supplying the web to a permeable conveyance member that is circularly conveyed with one side thereof, and continuously blowing the hot air to the web with one side thereof, In the step, the permeable conveyance member heated by the continuous blowing of the hot air is cooled before the web is supplied.

20. The nonwoven fabric production method according to claim 19, wherein The temperature of the permeable conveyance member after the cooling and before the continuous blowing of the hot air is 25°C or more and 130°C or less.

21. The nonwoven fabric production method according to claim 19, wherein The temperature difference between Mp and the temperature of the permeable conveyance member after the cooling, i.e., Mp - the temperature of the permeable conveyance member cooled by the cooling step is more than 0°C and 105°C or less.

22. The nonwoven fabric production method according to claim 1 or 2, wherein The nonwoven fabric obtained by blowing the hot air to the web is subjected to calendering processing.

23. The nonwoven fabric production method according to claim 22, wherein The calendering processing is performed in multiple stages, and any one of the calendering processing is performed under the following condition, i.e., Cl: Temperature: 25°C Linear pressure: 20 N / cm or more and 500 N / cm or less Roller: A pair of calendering rollers are used, and one is a calendering roller having a metal surface, and the other is a resin roller having a D hardness of 40 degrees or more and 100 degrees or less on the surface, the D hardness being referred to JIS K6253.

24. The nonwoven fabric production method according to claim 23, wherein A mirror-finished smooth calendering roller or a calendering roller to which fine irregularities are applied is used as the calendering roller having a metal surface.

25. The nonwoven fabric production method according to claim 23 or 24, wherein A roller composed of a resin of hard rubber, silicone rubber, polyurethane rubber, NBR, or EPDM is used as the resin roller.

26. The nonwoven fabric production method according to claim 23 or 24, wherein A resin roller having a D hardness of 70 degrees or more and 95 degrees or less is used as the resin roller, the D hardness being referred to JIS K6253.

27. The nonwoven fabric production method according to claim 23 or 24, wherein The calendering processing is performed at a linear pressure of 20 N / cm or more and 300 N / cm or less.

28. The nonwoven fabric production method according to claim 23 or 24, wherein At least one stage of the calendering processing among the calendering processing is performed under the condition Cl.

29. The nonwoven fabric production method according to claim 23 or 24, wherein The calendering is performed in two stages, and the second stage of calendering is performed under the condition C1.

30. The method for manufacturing a nonwoven fabric according to claim 29, wherein The line pressure of the first stage of calendering is made higher than the second stage.

31. The method for manufacturing a nonwoven fabric according to claim 30, wherein The line pressure of the first stage of calendering is made 50 N / cm or more and 700 N / cm or less.

32. The method for manufacturing a nonwoven fabric according to claim 22, wherein The nonwoven fabric after the calendering process is subjected to 1.2 mN-cm / cm 2 1.6 mN-cm / cm 2 The heat treatment or calendering process is performed in the following manner.

33. A nonwoven fabric manufactured by the method for manufacturing a nonwoven fabric according to any one of claims 1 to 32.

34. The nonwoven fabric according to claim 33, wherein The tensile strength in the length direction, i.e., the conveyance direction, of the nonwoven fabric is 10 N / 50 mm or more and 100 N / 50 mm or less.

35. The nonwoven fabric according to claim 33 or 34, wherein The tensile strength in the width direction, i.e., the direction orthogonal to the conveyance direction, of the nonwoven fabric is 4 N / 50 mm or more and 15 N / 50 mm or less.

36. The nonwoven fabric according to claim 33 or 34, wherein The number of fibers that cause fluff per unit area of the nonwoven fabric is 20 or less.

37. An absorbent article comprising the nonwoven fabric according to any one of claims 33 to 36 as a constituent member.

38. The absorbent article according to claim 37, wherein The nonwoven fabric has a layer containing heat-fusible fibers having a fiber diameter of 15 μm or less, The nonwoven fabric is contained in a manner such that the layer side becomes a skin abutting surface.

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