阅读说明：本技术 吸收性物品用层叠无纺布 (Laminated nonwoven fabric for absorbent article ) 是由 蒲谷吉晃 于 2020-02-05 设计创作，主要内容包括：本发明的层叠无纺布具有熔喷层(20)及层叠于该熔喷层(20)的单面或两面的纺粘层(10),构成熔喷层(20)的纤维(21)的纤维径小于1μm。本发明的层叠无纺布中,熔喷层(20)的最大厚度(t-(max))相对于最小厚度(t-(min))的比即t-(max)/t-(min)大于2,或者作为纤维的空间占有率的填充率大于7.7％。构成纺粘层(10)的纤维(11)优选该纤维(11)的横截面中的纤维纵横比大于1.2。(The laminated nonwoven fabric of the present invention has a meltblown layer (20) and a spunbond layer (10) laminated on one or both surfaces of the meltblown layer (20), and the fiber diameter of the fibers (21) constituting the meltblown layer (20) is less than 1 [ mu ] m. In the laminated nonwoven fabric of the present invention, the maximum thickness (t) of the meltblown layer (20) max ) Relative to the minimum thickness (t) min ) Is t max /t min Greater than 2, or a filling rate greater than 7.7% as the space occupancy of the fibers. The fibers (11) constituting the spunbond layer (10) preferably have a fiber aspect ratio in a cross section of the fibers (11) of greater than 1.2.)

1. A laminated nonwoven fabric for an absorbent article, comprising a meltblown layer and a spunbond layer laminated on one or both surfaces of the meltblown layer,

the diameter of the fibers constituting the meltblown layer is less than 1 μm,

the laminated nonwoven fabric satisfies at least one of the following (1) and (2):

(1) maximum thickness t of the meltblown layer_maxRelative to the minimum thickness t_minIs t_max/t_minIs greater than 2, and the reaction temperature is higher than that of the reaction kettle,

(2) the filling rate of the laminated non-woven fabric is more than 7.7%.

2. A laminated nonwoven fabric for an absorbent article, comprising a meltblown layer and a spunbond layer laminated on one or both surfaces of the meltblown layer,

the diameter of the fibers constituting the meltblown layer is less than 1 μm,

maximum thickness t of the meltblown layer_maxRelative to the minimum thickness t_minIs t_max/t_minGreater than 2.

3. A laminated nonwoven fabric for an absorbent article, comprising a meltblown layer and a spunbond layer laminated on one or both surfaces of the meltblown layer,

the diameter of the fibers constituting the meltblown layer is less than 1 μm,

the filling rate of the laminated non-woven fabric is more than 7.7%.

4. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 3, wherein the fibers constituting the spunbond layer have a larger fiber diameter than the fibers constituting the meltblown layer.

5. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 4, wherein the fibers constituting the spunbond layer have a fiber aspect ratio in a cross section of more than 1.2.

6. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 5, wherein the fiber diameter of the fibers constituting the meltblown layer is 0.1 μm or more and less than 1 μm.

7. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 6, wherein the fiber diameter of the fibers constituting the meltblown layer is 0.1 μm or more and 0.85 μm or less.

8. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 7, wherein the maximum thickness t of the meltblown layer_maxRelative to the minimum thickness t_minIs t_max/t_minGreater than 2 and 14 or soThe following steps.

9. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 8, wherein the maximum thickness t of the meltblown layer_maxRelative to the minimum thickness t_minIs t_max/t_minIs 3 or more and 10 or less.

10. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 9, wherein the filling factor of the laminated nonwoven fabric is greater than 7.7% and 35% or less, preferably 10% or more, and more preferably 14% or more.

11. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 10, wherein the fibers constituting the spunbond layer have a fiber aspect ratio in a cross section of more than 1.2 and 2.5 or less.

12. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 11, wherein a ratio of a maximum fiber width to a minimum fiber width of fibers constituting the spunbond layer, that is, a maximum fiber diameter/a minimum fiber diameter, is greater than 1.1 and 2.5 or less.

13. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 12, wherein the filling factor of the laminated nonwoven fabric is 35% or less, preferably 30% or less, and more preferably 25% or less.

14. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 13, wherein the filling factor of the laminated nonwoven fabric is 14% or more and 25% or less.

15. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 14, wherein the proportion of fibers having a longer axis of a cross section of the fibers closer to a direction parallel to the plane of the laminated nonwoven fabric than a shorter axis of the fibers in the fibers constituting the spunbond layer is 75% or more and 100% or less, preferably more than 75% and 100% or less, more preferably 80% or more and 100% or less, and still more preferably 85% or more and 100% or less.

16. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 15, wherein the filling factor of the meltblown layer is greater than 4.1% and 11% or less.

17. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 16, wherein the filling rate of the meltblown layer is 6% or more and 9% or less.

18. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 17, wherein the fiber diameter of the fibers constituting the spunbond layer is 16 μm or more and 35 μm or less.

19. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 18, wherein the water pressure resistance of the laminated nonwoven fabric is 1600mmAq. or more and 5000mmAq. or less.

20. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 19, wherein the laminated nonwoven fabric includes only an embossed portion that bonds the meltblown layer and the spunbond layer laminated on one or both surfaces of the meltblown layer.

21. The laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 20, wherein either or both of the cross-sectional shape of the fibers constituting the spunbond layer and the cross-sectional shape of the fibers constituting the meltblown layer are circular.

22. An absorbent article having a skin-facing surface side and a non-skin-facing surface side, and

comprises a surface material and an absorber disposed on the non-skin-facing side of the surface material,

the laminated nonwoven fabric for an absorbent article according to any one of claims 1 to 21 is disposed on the non-skin-facing surface side of the absorbent body,

the laminated nonwoven fabric is arranged such that the spunbond layer faces the non-skin-facing surface side.

23. A method for manufacturing a laminated nonwoven fabric for an absorbent article, comprising the steps of:

a step of producing a laminate having a meltblown layer and a spunbond layer laminated on one or both surfaces of the meltblown layer, the step including a step of forming the spunbond layer by a spunbond method and a step of forming the meltblown layer by a meltblown method;

an embossing step of embossing the laminate; and

and a calendering step of calendering the laminate.

24. The method of manufacturing a laminated nonwoven fabric for an absorbent article according to claim 23, wherein the embossing step is followed by the calendering step.

25. The method for producing a laminated nonwoven fabric for an absorbent article according to claim 23 or 24, wherein in the calendering step, calendering is performed at a line pressure of 2N/mm or more and 40N/mm or less.

26. The method for producing a laminated nonwoven fabric for an absorbent article according to any one of claims 23 to 25, wherein the linear pressure in the calendering step is 10N/mm or more and 25N/mm or less.

27. The method for producing a laminated nonwoven fabric for an absorbent article according to any one of claims 23 to 26, wherein the step of producing the laminate comprises: after forming one of the meltblown layer and the spunbond layer, the fibers forming the other layer are deposited directly on the one layer to form the other layer.

28. The method for producing a laminated nonwoven fabric for an absorbent article according to any one of claims 23 to 27, wherein an anvil roll used for the calendering process has a smooth surface.

29. The method for producing a laminated nonwoven fabric for an absorbent article according to any one of claims 23 to 28, wherein the calendering step is performed at a temperature lower than the melting point of the spunbond fibers and the meltblown fibers, which are the fibers contained in the laminate.

30. A method for manufacturing an absorbent article, comprising a step of sequentially laminating a surface material, an absorbent body, and a laminated nonwoven fabric in the thickness direction,

the laminated nonwoven fabric is produced by the method for producing a laminated nonwoven fabric for an absorbent article according to any one of claims 23 to 30, and the laminated nonwoven fabric is laminated such that the spunbond layer is positioned on the surface opposite to the surface facing the absorbent body.

Technical Field

The present invention relates to a laminated nonwoven fabric for an absorbent article.

Background

Conventionally, in absorbent articles such as disposable diapers and sanitary napkins, nonwoven fabrics have been used as constituent members. For example, patent document 1 describes a nonwoven fabric containing spirally crimped fibers of a single polymer as a nonwoven fabric used for an absorbent article. Patent document 1 describes: a meltblown layer and a 2 nd spunbond layer were sequentially laminated on the spunbond layer formed of the spirally crimped fibers, and a nonwoven fabric having a 3-layer structure of spunbond-meltblown-spunbond fibers was produced.

Documents of the prior art

Patent document

Patent document 1: japanese Kokai publication No. 2005-517093

Disclosure of Invention

The present invention is a laminated nonwoven fabric having a meltblown layer and a spunbond layer laminated on one or both sides of the meltblown layer.

The laminated nonwoven fabric of the present invention preferably has a fiber diameter of fibers constituting the meltblown layer of less than 1 μm.

The laminated nonwoven fabric of the present invention is preferably such that the maximum thickness t of the meltblown layer is_maxRelative to the minimum thickness t_minIs t_max/t_minGreater than 2.

The laminated nonwoven fabric of the present invention preferably has a packing fraction of more than 7.7%.

In a preferred embodiment, the laminated nonwoven fabric is a laminated nonwoven fabric for an absorbent article.

The present invention is a method for producing a laminated nonwoven fabric, including the steps of:

a step of producing a laminate having a meltblown layer and a spunbond layer laminated on one or both surfaces of the meltblown layer, the step including a step of forming the spunbond layer by a spunbond method and a step of forming the meltblown layer by a meltblown method; and

and an embossing step of embossing the laminate.

The method for producing a laminated nonwoven fabric of the present invention preferably includes a calendering step of calendering the laminate.

In a preferred embodiment, the laminated nonwoven fabric is a laminated nonwoven fabric for an absorbent article.

Other features of the present invention will be apparent from the description of the claims and the following description.

Drawings

Fig. 1 is a cross-sectional view schematically showing an embodiment of the laminated nonwoven fabric of the present invention.

Fig. 2 is a schematic plan view of the laminated nonwoven fabric shown in fig. 1.

Fig. 3 is a perspective view of the laminated nonwoven fabric shown in fig. 2.

Fig. 4 is an enlarged view of the portion III shown in fig. 1.

Fig. 5(a) is a perspective view of an absorbent article provided with the laminated nonwoven fabric shown in fig. 1, and fig. 5(b) is a schematic cross-sectional view taken along line Vb-Vb in fig. 5 (a).

Fig. 6 is a conceptual diagram illustrating an embodiment of the method for producing a laminated nonwoven fabric of the present invention.

Fig. 7 is a schematic perspective view showing a part of a conventional laminated nonwoven fabric in an enlarged manner.

Detailed Description

As a leakage preventing material for an absorbent article, a single-layer or multi-layer nonwoven fabric may be used instead of a resin film from the viewpoints of flexibility, skin touch, and the like. In this regard, since the melt-blown nonwoven fabric has a high packing density by the compressed thickness to improve the water pressure resistance, it is considered to use the melt-blown nonwoven fabric having a compressed thickness to improve the water pressure resistance as a leakage preventing material for an absorbent article. However, even when conventional meltblown nonwoven fabrics are highly filled, it is difficult to sufficiently increase the water pressure resistance because the fibers constituting the meltblown nonwoven fabric are further separated when water pressure is applied, and a portion having a low fiber density is formed. In the present specification, the term "highly filled" means that the space occupancy of the fibers is increased.

As in patent document 1, by laminating a meltblown layer and a spunbond layer, the water pressure resistance can be improved as compared with the case of a meltblown nonwoven fabric alone. Fig. 7 is a schematic perspective view of a conventional laminated nonwoven fabric 7. The laminated nonwoven fabric 7 is a so-called SMS nonwoven fabric in which a spunbond layer 70, a meltblown layer 80, and a spunbond layer 70 are laminated in this order. The meltblown layer 80 may have a portion where the density of the meltblown fibers 81 constituting the meltblown layer 80 is low, and this portion may be a hole 80A through which liquid easily passes. Since the spunbond layer 70 is laminated on the meltblown layer 80, the spunbond fibers 71 constituting the spunbond layer 70 can block the holes 80A existing in the meltblown layer 80, and it is considered that the water pressure resistance can be improved by laminating the spunbond layer 70 on the meltblown layer 80. However, in order to be used as a leakage preventing material for an absorbent article, it is desired to further improve the water pressure resistance.

The present invention relates to a laminated nonwoven fabric having improved water pressure resistance.

Hereinafter, the present invention will be described based on preferred embodiments thereof.

The laminated nonwoven fabric of the present invention has a meltblown layer, typically a spunbond-meltblown (SM) nonwoven fabric, and a spunbond layer, typically a spunbond-meltblown-Spunbond (SMs) nonwoven fabric, laminated on one or both sides of the meltblown layer.

The laminated nonwoven fabric of the present invention is preferably obtained by subjecting a laminate having a meltblown layer and a spunbond layer laminated on one or both surfaces of the meltblown layer to calendering. The laminated nonwoven fabric is formed by making the melt-blown layer with a small fiber diameter highly filled and satisfying at least 1 of the following conditions (1) or (2). This results in a nonwoven fabric, which has a significantly improved water pressure resistance, and exhibits a high level of water resistance suitable for use as a leakage preventing material for an absorbent article.

Condition (1) maximum thickness t of meltblown layer_maxRelative to the minimum thickness t_minIs t_max/t_minGreater than 2.

The condition (2) is that the filling factor (also simply referred to as filling factor) of the laminated nonwoven fabric, which is the space occupancy of the fibers, is greater than 7.7%.

The laminated nonwoven fabric of the present invention satisfies at least 1 of the above conditions (1) or (2), and preferably satisfies the above conditions (1) and (2).

Hereinafter, the laminated nonwoven fabric satisfying the above condition (1) is also referred to as a laminated nonwoven fabric 1A, and the laminated nonwoven fabric satisfying the above condition (2) is also referred to as a laminated nonwoven fabric 1B.

A preferred structure common to the laminated nonwoven fabrics 1A and 1B will be described by taking as an example the laminated nonwoven fabric 1 shown in fig. 1 to 3 that satisfies the above conditions (1) and (2).

The laminated nonwoven fabric 1 shown in fig. 1 to 3 has a meltblown layer 20 and spunbond layers 10 laminated on both surfaces of the meltblown layer 20. The meltblown layer 20 is a layer formed by a meltblowing method, and is composed of fibers 21 spun by a meltblowing method. The spunbond layer 10 is a layer formed by a spunbond process and is composed of fibers 11 spun in the spunbond process. Hereinafter, the fibers 21 spun by the melt blowing method constituting the melt blown layer 20 are also referred to as melt blown fibers, and the fibers 11 spun by the spunbond method constituting the spunbond layer 10 are also referred to as spunbond fibers. In general, the spunbond fibers have larger fiber diameters than the meltblown fibers.

In fig. 1 and 2, the symbol X is an arbitrary direction along the plane direction of the laminated nonwoven fabric 1, and in fig. 2, the symbol Y is a direction orthogonal to the X direction in the plane direction. In fig. 1, reference symbol Z denotes the thickness direction of the laminated nonwoven fabric 1. As shown in fig. 1 and 2, the spunbond layer 10 may be intermittently present without the spunbond fibers 11 being present without gaps over the entire area of the laminated nonwoven fabric 1 in the planar direction.

In general, since the fibers constituting the meltblown layer have a small fiber diameter, the meltblown layer has a high fiber density and exhibits water pressure resistance, but has a weak strength. To compensate for this disadvantage, a spunbond layer having a large fiber diameter of the constituent fibers is often laminated on the meltblown layer. Since the fiber diameter of the fibers constituting the spunbond layer is larger than that of the meltblown layer, the fiber density of the spunbond layer is low, and the spunbond layer alone does not contribute to the water pressure resistance. On the other hand, by laminating a spunbond layer to a meltblown layer, the area of the meltblown layer where the fiber density is small is covered and the mesh is blocked, thereby improving the water pressure resistance. However, according to the present invention, the water pressure resistance-improving effect is further improved.

In the laminated nonwoven fabric 1, the fiber diameter of the fibers constituting the meltblown layer 20 is less than 1 μm. The laminated nonwoven fabric 1 is obtained by, for example, calendering a laminate 2 having a meltblown layer 20 and a spunbond layer 10 laminated on the meltblown layer 20 (see fig. 6).

Melt-blown nonwoven fabrics having a fiber diameter of less than 1 μm are also known. However, the meltblown nonwoven fabric used for the absorbent article is generally one having a fiber diameter of more than 1 μm. In contrast, the fiber diameter of the constituent fibers of the meltblown layers in the laminated nonwoven fabric 1 and the laminated body 2 is less than 1 μm. By setting the fiber diameter of the fibers constituting the meltblown layer to less than 1 μm, the fiber density is increased over the entire area of the meltblown layer. This can suppress the occurrence of a region having a low fiber density in the meltblown layer. Further, by subjecting the laminate 2 having the meltblown layer and the spunbond layer to the calendering process, the effect of improving the water pressure resistance can be reliably obtained.

In both of the laminated nonwoven fabric 1 and the laminate 2 before calendering, the fiber diameter of the fibers 21 constituting the meltblown layer 20 is less than 1 μm, preferably 0.95 μm or less, more preferably 0.9 μm or less, and still more preferably 0.85 μm or less, from the viewpoint of reliably obtaining the effect of improving the water pressure resistance.

The lower limit is not particularly limited, but from the viewpoint of stably spinning by the melt blowing method, it is realistic to set the lower limit to 0.1 μm or more.

The fiber diameter of the fibers 21 constituting the meltblown layer 20 is preferably 0.1 μm or more and less than 1 μm, more preferably 0.1 μm or more and 0.95 μm or less, still more preferably 0.1 μm or more and 0.9 μm or less, and particularly preferably 0.1 μm or more and 0.85 μm or less.

Fig. 6 is a view showing an example of a method for producing the laminated nonwoven fabric 1. The laminate 2 to be subjected to the calendering is not limited to the one shown in fig. 6. For example, a laminate in which a spunbond nonwoven fabric wound out from a roll sheet and a meltblown nonwoven fabric wound out from the roll sheet in the same manner are laminated, a laminate in which meltblown fibers are sprayed onto a spunbond nonwoven fabric wound out from a roll sheet, a laminate having a spunbond layer only on one side of a meltblown layer, or the like may be used. The details of the manufacturing method shown in fig. 6 will be described later.

The fiber diameter of the fibers constituting the meltblown layer was measured by the following method.

< method for measuring fiber diameter of fiber constituting meltblown layer >

10 small samples were randomly cut out from the laminated nonwoven fabric as an object of measurement using a razor. The observation was performed by focusing on a portion of the meltblown layer not including the embossed portion using a Scanning Electron Microscope (SEM). The observation magnification is set so that 20 to 30 meltblown fibers are projected in the visual field, and a photograph is taken. The observation magnification is, for example, 4500 times or more. The fiber diameter was measured by counting all the fibers in the visual field one by one. The diameter is defined as the fiber diameter when the cross section of the fiber is a perfect circle, the length of the major axis is defined as the fiber diameter when the cross section is an ellipse, and the length of the line having the longest span length in the cross section of the fiber is defined as the fiber diameter when the cross section is not either a perfect circle or an ellipse. The fiber diameters of 200 or more fibers in total of 20 or more were measured for each of the 10 small piece samples measured in this manner. The average value of these values was calculated. The average value is obtained by rounding the decimal point and the second place by a micrometer, and the value is set as the fiber diameter of the fibers constituting the meltblown layer.

When a small piece of sample was cut from the laminated nonwoven fabric using a razor, the laminated nonwoven fabric was immersed in liquid nitrogen, and then the laminated nonwoven fabric was taken out of the liquid nitrogen, and the small piece of sample was cut within 30 seconds. As the razor, a razor having an edge with a thickness of 0.23mm was used. The laminated nonwoven fabric was cut with a razor standing in a direction perpendicular to the plane direction of the laminated nonwoven fabric.

Method for measuring fiber diameter of fiber constituting meltblown layer by SEM and minimum thickness t of meltblown layer_minAnd a maximum thickness t_maxThe measuring methods of (1), (ii) the measuring methods of the minor axis and major axis lengths of the spunbond fibers, (iii) the judging method, (iv) the measuring method of the maximum fiber width and the minimum fiber width, (iv) the measuring method of the fiber diameter of the fibers constituting the spunbond layer, and (iv) liquid nitrogen is required.

Liquid nitrogen is used as necessary for the methods other than the above method of measuring the filling ratio of the laminated nonwoven fabric, the method of measuring the density of the resin, the method of measuring the filling ratio of the meltblown layer, and the method of measuring the weight per unit area.

When the laminated nonwoven fabric to be measured is incorporated into a product such as an absorbent article, a cold spray is sprayed to the product to cure the adhesive, and the laminated nonwoven fabric to be measured is carefully peeled off and taken out. The measurement of the fiber diameter in the laminated nonwoven fabric is performed at a portion where the fibers retain their shape, avoiding the embossed portion. The extraction method and the measurement site are also applicable to other measurements in the present specification. In addition, SEM used in the measurement in the present specification is JCM-6000PLUS manufactured by Japan Electron Ltd.

In general, the conventional thermoplastic fibers have a constant fiber diameter in the longitudinal direction of the fibers without undergoing compression deformation or the like. In the present invention, the fiber diameter of the meltblown fibers and the fiber diameter of the spunbond fibers are constant in the longitudinal direction, respectively, except for the compression-deformed portion.

In general, a cross section of a thermoplastic fiber spun by using a conventional circular (perfect circle) nozzle is fixed to a perfect circle in the longitudinal direction without compression deformation or the like. In the present invention, the cross-sectional shapes of the meltblown fibers and the spunbond fibers are substantially circular except for the compression-deformed portion, and are fixed in the longitudinal direction of the fibers.

When the laminated nonwoven fabric 1 is produced by compressing the laminate 2 by calendaring or the like, the laminated nonwoven fabric 1 is compressed in the thickness direction Z. As a result, the distance between fibers is reduced and the filling is increased both in the laminated nonwoven fabric 1 as a whole and in the meltblown layer 20. Further, by compressing the meltblown layer 20 and the spunbond layer 10 in a laminated state, a portion where the spunbond fibers 11 are much present is in a state where the spunbond fibers 11 are sunk into the meltblown layer 20 when microscopically observed (see fig. 1).

The laminated nonwoven fabrics 1A and 1B satisfy the above conditions (1) and (2) by such action, for example. This shows significantly superior water resistance compared to conventional SMS nonwoven fabrics having a spunbond layer and a meltblown layer but not subjected to calendering. The laminated nonwoven fabrics 1A and 1B will be further described below. The water resistance can be evaluated using water pressure resistance as an index, and those with high water pressure resistance are excellent in water resistance.

[ laminated nonwoven Fabric 1A ]

As shown in fig. 1, the laminated nonwoven fabric 1A is in a state where the spunbond fibers 11 constituting the spunbond layer 10 are embedded in the meltblown layer 20. Thus, the laminated nonwoven fabric 1A has a relatively large thickness portion and a relatively small thickness portion of the meltblown layer 20 when compared in the planar direction of the laminated nonwoven fabric 1A. In particular, in the meltblown layer 20, the thickness of the meltblown layer 20 is reduced in the portion where the spunbond fibers 11 are relatively densely present compared to the portion where the spunbond fibers 11 are relatively sparsely present.

In the laminated nonwoven fabric 1A, the spunbond fibers 11 are partially embedded in the meltblown layer 20, and the fiber-restraining portions 4 in which the movement of the meltblown fibers 21 in the meltblown layer 20 is suppressed by the spunbond fibers 11 are formed in the laminated nonwoven fabric 1A. In the fiber retaining portion 4, when the movement of the meltblown fibers 21 is suppressed, the meltblown fibers 21 are not easily separated even if, for example, water pressure is applied to the meltblown layer. Also, the generation of a portion having a low fiber density such as a reduced water pressure resistance is prevented in the meltblown layer 20.

Since the laminated nonwoven fabric 1A has the condition (1), the spunbond fibers 11 are greatly inserted into the meltblown layer 20, and the movement suppression force of the meltblown fibers 21 in the fiber retaining portions 4 is high. The fiber-restraining portions 4 formed by the pressure of the spunbond fibers 11 constituting the spunbond layer 10 are dispersed in the planar direction of the laminated nonwoven fabric 1A.

According to the laminated nonwoven fabric 1A, the fiber-restrained portions 4 having a strong movement restraining force are formed in a state of being dispersed in the planar direction, and thus a laminated nonwoven fabric having a further reliably improved water pressure resistance can be obtained.

Minimum thickness t of meltblown layer 20_minAnd a maximum thickness t_maxThe measurement was carried out by the following method.

< minimum thickness t of meltblown layer_minAnd a maximum thickness t_maxMethod for measuring (1)

The laminated nonwoven fabric is cut at a plurality of locations spaced apart in the plane direction thereof by a razor. At this time, the cutting surface without the embossed portion is obtained. And observing the cutting surface at each cutting part by using SEM at a magnification of about 100-300 times. The thickness of the minimum thickness portion and the maximum thickness portion of the meltblown layer having a width of 400 μm centered on the center of each cut surface in the planar direction were measured. For measuring in this wayThe thickness of the minimum portion and the thickness of the maximum portion of the meltblown layer on each cut surface of (a) are averaged, and the average value is calculated. The average values of these are set to the minimum thickness t_minAnd a maximum thickness t_max. The observed cut surface was set to 5 or more positions, and measurement was performed so that the total width of the measurement range was 2mm or more (400 μm × 5 or more).

From the viewpoint of suppressing the migration of the meltblown fibers 21 and further improving the water resistance, the maximum thickness t of the meltblown layer 20_maxRelative to the minimum thickness t_minIs t_max/t_minPreferably greater than 2, more preferably 2.5 or more, and still more preferably 3 or more.

From the viewpoint of maintaining excellent flexibility as a nonwoven fabric, it is preferably 14 or less, more preferably 13.5 or less, and still more preferably 10 or less.

From the viewpoint of achieving both of these effects, the average particle size is preferably greater than 2 and not more than 14, more preferably 2.5 or more and not more than 13.5, and still more preferably 3 or more and not more than 10.

The minimum thickness t of the meltblown layer 20 is set to maintain excellent flexibility as a nonwoven fabric_minPreferably 5 μm or more, more preferably 10 μm or more.

From the viewpoint of suppressing the migration of the meltblown fibers 21 and further improving the water resistance, it is preferably 45 μm or less, and more preferably 20 μm or less.

From the viewpoint of achieving both of these, the particle diameter is preferably 5 μm or more and 45 μm or less, and more preferably 10 μm or more and 20 μm or less.

The maximum thickness t of the meltblown layer 20 is set to maintain excellent flexibility as a nonwoven fabric_maxPreferably 65 μm or more, and more preferably 95 μm or more.

From the viewpoint of further improving the water resistance, it is preferably 130 μm or less, and more preferably 100 μm or less.

From the viewpoint of achieving both of these, it is preferably 65 μm or more and 130 μm or less, and more preferably 95 μm or more and 100 μm or less.

[ laminated nonwoven Fabric 1B ]

The laminated nonwoven fabric 1B is obtained by subjecting a laminate 2 having a meltblown layer 20 and a spunbond layer 10 laminated on the meltblown layer 20 to calendering, for example. This increases the filling ratio of the whole laminated nonwoven fabric, and satisfies the above condition (2).

When the laminated nonwoven fabric 1B satisfies the condition (2), the spunbond fibers 11 constituting the spunbond layer 10 are closely adhered to the meltblown layer 20. Even if the meltblown layer 20 has a portion with a low fiber density such as the hole 80A shown in fig. 7, the portion can be effectively covered, and the liquid permeation preventing performance from the portion is excellent.

According to the laminated nonwoven fabric 1B, the effect of improving the water pressure resistance achieved by the high filling of the meltblown layer 20 having a small fiber diameter of the constituent fibers can be obtained, and the effect of improving the water pressure resistance achieved by the adhesion of the spunbond fibers 11 can also be obtained. Therefore, according to the laminated nonwoven fabric 1B, high water pressure resistance can be obtained.

The filling factor of the laminated nonwoven fabric was measured by the following method.

< method for measuring filling factor of laminated nonwoven Fabric >

A test piece of 10 cm. times.10 cm was cut out from the laminated nonwoven fabric to be measured using a razor. When a test piece of 10cm × 10cm cannot be cut, a test piece having an area as large as possible is cut. The thickness was measured using a laser thickness meter under a load of 50 Pa. The thickness of the laminated nonwoven fabric was set as an average value at 3 points of measurement from one test piece. Next, the mass of the test piece was measured, and the value obtained by dividing the mass by the area was defined as the weight per unit area of the laminated nonwoven fabric. The filling factor of the laminated nonwoven fabric was calculated from { the weight per unit area of the laminated nonwoven fabric/(the thickness of the laminated nonwoven fabric × the density of the resin) } × 100.

The laser thickness meter used in this specification is ZSLD80 manufactured by OMRON corporation.

The "density of the resin" can be measured by the following method.

< method for measuring Density of resin >

The taken-out laminated nonwoven fabric was subjected to Labopress (manufactured by Toyo Seiki Seisaku-Sho Ltd., model No.)P2-30) was pressed in two stages at 180 ℃ (low pressure: 5kg/cm³And high pressure: 150kg/cm³) The film was produced by performing the cooling press for 1 minute after the pressing for 1 minute. Thereafter, a 10 × 10cm sample was cut from a place not contaminated with air using a razor, and the mass was measured and divided by the volume to calculate a value, which was used as the density of the resin. The volume of the produced film can be calculated by multiplying the thickness of the film by the area. The thickness of the film can be determined by a laser thickness meter.

From the viewpoint of improving the water pressure resistance, the filling ratio of the laminated nonwoven fabric 1B is preferably more than 7.7%, more preferably 10% or more, and further preferably 14% or more.

From the viewpoint of improving the texture of the laminated nonwoven fabric 1B, it is preferably 35% or less, more preferably 30% or less, and still more preferably 25% or less.

From the viewpoint of achieving both of these, it is preferably more than 7.7% and 35% or less, more preferably 10% or more and 30% or less, and still more preferably 14% or more and 25% or less.

A preferred structure of the laminated nonwoven fabrics 1A and 1B will be further described with reference to the laminated nonwoven fabric 1 shown in fig. 1 to 3.

The laminated nonwoven fabric 1 preferably has a flat shape in the cross-sectional shape of the spunbond fibers 11. Specifically, as shown in fig. 4, the cross section of the spunbond fibers 11 in the direction perpendicular to the longitudinal direction of the spunbond fibers 11 has a flat shape having a major axis and a minor axis. The laminated nonwoven fabric 1 preferably has a fiber aspect ratio of the spunbond layer of greater than 1.2. That is, "flat" as used herein means that the fiber aspect ratio is greater than 1.2. The laminated nonwoven fabric 1 may have a fiber aspect ratio of some of the spunbond fibers 11 constituting the spunbond layer 10 of more than 1.2, and preferably has a fiber aspect ratio of all the spunbond fibers 11 of more than 1.2. It can be produced, for example, in the following manner: the spunbond fibers 11 are flattened by being subjected to a calendering process.

The length L of the major axis of the cross section of the spunbond fiber 11 is defined as the length L of the major axis when a line segment connecting 2 points having the longest distance from each other among 2 arbitrary points on the outer periphery of the cross section of the spunbond fiber 11 extracted by microscopic observation is defined as the major axis (see fig. 4). On the other hand, the short axis is a length S of a short side when a rectangle having a long side parallel to the long axis determined in the above manner and circumscribing the outer periphery is drawn (see fig. 4).

The laminated nonwoven fabric 1 has a fiber aspect ratio of more than 1.2, and the spunbond fibers 11 have a flat shape, so that the spunbond fibers 11 can cover the surface of the meltblown layer 20 with a larger area. Therefore, even if the meltblown layer 20 has a portion with a low fiber density such as the hole 80A shown in fig. 7, the spunbond fibers 11 can effectively cover the portion, and have excellent performance of preventing the liquid from permeating through the portion.

The laminated nonwoven fabric 1, when the fiber aspect ratio is larger than 1.2, not only exerts the effect of improving the water pressure resistance by increasing the filling of the meltblown layer 20 having a small fiber diameter constituting the fibers, but also exerts the effect by the flat spunbond fibers 11. Therefore, according to the laminated nonwoven fabric 1 having the fiber aspect ratio of more than 1.2, high water pressure resistance can be obtained.

The fiber aspect ratio of the spunbond fibers 11 is preferably more than 1.2, and more preferably 1.6 or more from the viewpoint of covering the surface of the meltblown layer with a larger area.

From the viewpoint of maintaining excellent flexibility as a nonwoven fabric, it is preferably 2.5 or less, and more preferably 2.2 or less.

From the viewpoint of achieving both of these, it is preferably more than 1.2 and 2.5 or less, and more preferably 1.6 or more and 2.2 or less.

< method for measuring the lengths of the minor and major axes of spunbonded fibers >

The measurement piece having a cut surface in the thickness direction was cut out by a razor from any 5 points spaced in the planar direction of the laminated nonwoven fabric. At this time, the cutting surface without the embossed portion is obtained. The embossed portions of the cut surfaces of each measurement piece were observed at 300 magnifications by SEM. 10 or more spun-bonded fibers 11 are randomly selected from the cut surfaces of 5 measurement pieces, and the length of the short axis and the length of the long axis are measured for 50 or more spun-bonded fibers in total of 5 measurement pieces, and the average values of the short axis length S and the long axis length L are defined as the average values.

From the viewpoint of increasing the area of the coated meltblown layer and improving the water pressure resistance, the spunbond fibers 11 preferably have the long axes L of their cross sections oriented in the direction along the plane of the laminated nonwoven fabric 1. Whether or not the long axis L of the cross section is oriented in the direction along the plane direction of the laminated nonwoven fabric 1 is determined by the following method.

< determination method >

A measurement piece having a cut surface in the thickness direction was cut out by a razor from any 5 points spaced in the planar direction of the laminated nonwoven fabric 1. At this time, the cutting surface without the embossed portion is obtained. The cut surface of each measurement piece not containing the embossed portion was observed with an SEM at a magnification of 300 times. 10 or more spun-bonded fibers 11 were randomly selected from the cut surfaces of 5 pieces. It is determined which of the major axis and the minor axis of these spunbond fibers 11 is closer to the direction parallel to the plane of the laminated nonwoven fabric. For each of the 5 test pieces, the ratio of spunbond fibers in a direction parallel to the plane of the laminated nonwoven fabric, in which the major axis is closer to the minor axis than the minor axis, among 50 total spunbond fibers of 10 or more. When the ratio is 75% or more, it is determined that the long axis L of the cross section is oriented in the direction along the plane of the laminated nonwoven fabric 1. The proportion of the spunbond fibers in the direction parallel to the plane of the laminated nonwoven fabric is preferably more than 75%, more preferably 80% or more, further preferably 85% or more, and 100% or less.

The laminated nonwoven fabric 1 is formed by calendering the spunbond fibers 11 of the laminated nonwoven fabric 1, and 1 piece of the spunbond fibers 11 has a strongly-compressed portion and a weakly-compressed portion. The strongly compressed portions of the spunbond fibers 11 are more flat and have a flatter cross-sectional shape. The weakly pressurized portions of the spunbond fibers 11 are less flat and have a more nearly perfectly round cross-sectional shape. That is, the spunbond fibers 11 preferably have portions having different fiber widths in the longitudinal direction of the spunbond fibers 11. Here, the fiber width means the length of the line that spans the longest length in the cross section of the fiber. The ratio of the maximum fiber width to the minimum fiber width (maximum fiber diameter/minimum fiber diameter) in the spunbond fibers 11 is preferably greater than 1.1, more preferably greater than 1.4.

In order to avoid local pressurization, the nonwoven fabric is kept soft and has a good texture, preferably 2.5 or less, and more preferably 2 or less.

In order to sufficiently pressurize the substrate, the pressure is preferably more than 1.1 and 2.5 or less, more preferably more than 1.4 and 2 or less.

Before calendering, that is, when the cross-sectional shape of the fiber is a flat shape from the time of spinning, the fiber width does not change greatly in the longitudinal direction of the fiber, and the ratio of the maximum fiber width to the minimum fiber width does not fall within the above range.

The maximum and minimum fiber widths of the spunbond fibers 11 were measured as follows.

< method for measuring maximum fiber width and minimum fiber width >

The measurement piece having a cut surface in the thickness direction was cut out by a razor from any 5 points spaced in the planar direction of the laminated nonwoven fabric. At this time, the cutting surface without the embossed portion is obtained. The embossed portions of the cut surfaces of each measurement piece were observed at 300 magnifications by SEM. 10 or more spun-bonded fibers 11 are randomly selected from the cut surfaces of 5 measurement pieces, and the length of the line having the longest span length in the cross section of the fibers is measured for 50 or more spun-bonded fibers in total of the 5 measurement pieces, and the average of the maximum 5 is set as the maximum fiber width, and the average of the minimum 5 is set as the minimum fiber width. The second decimal place after the decimal place of the value obtained by dividing the maximum fiber width by the minimum fiber width is rounded to be the ratio of the minimum fiber width to the maximum fiber width.

From the viewpoint of improving the water pressure resistance, the meltblown layer 20 of the laminated nonwoven fabric 1 is preferably closed with meshes and has small gaps between fibers. Specifically, the filling rate per unit space and the weight per unit area, which is the mass per unit area, are preferably high.

From the viewpoint of improving the water pressure resistance, the filling ratio of the meltblown layer 20 is preferably more than 4.1%, more preferably 5% or more, and still more preferably 6% or more.

From the viewpoint of maintaining excellent flexibility as a nonwoven fabric, it is preferably 11% or less, more preferably 10% or less, and still more preferably 9% or less.

From the viewpoint of achieving both of these effects, the content is preferably more than 4.1% and 11% or less, more preferably 5% or more and 10% or less, and still more preferably 6% or more and 9% or less.

< method for measuring filling factor of meltblown layer >

A test piece of 10 cm. times.10 cm was cut out from the laminated nonwoven fabric using a razor. When a test piece of 10cm × 10cm cannot be cut, a test piece having an area as large as possible is cut. The meltblown layer was removed from the test piece by carefully peeling the spunbond layer off with hands or tweezers. The thickness under a load of 50Pa was measured using a laser thickness meter, and the average value was defined as the thickness of the meltblown layer. Next, the weight of the meltblown layer was measured, and the value obtained by dividing the weight by the area of the laminated nonwoven fabric was defined as the weight per unit area of the meltblown layer. The filling factor of the meltblown layer was calculated from { weight per unit area of the meltblown layer/(thickness of the meltblown layer × density of resin) } × 100.

The "density of the resin" is measured by the same method as the above-described < method for measuring the density of the resin >.

The weight per unit area of the meltblown layer 20 is preferably 5g/m²Above, more preferably 7.5g/m²The above.

Further, it is preferably 15g/m²Hereinafter, more preferably 12.5g/m²The following.

Further, it is preferably 5g/m²Above and 15g/m²Hereinafter, more preferably 7.5g/m²Above and 12.5g/m²The following.

The weight per unit area was measured by the following method.

< method for measuring weight per unit area >

When the weight per unit area of the laminated nonwoven fabric was measured, a test piece of 10cm × 10cm was cut out from the laminated nonwoven fabric to be measured using a razor. When a test piece of 10cm × 10cm cannot be cut, a test piece having an area as large as possible is cut. Next, the mass of the test piece was measured, and the value obtained by dividing the mass by the area was defined as the weight per unit area of the laminated nonwoven fabric.

In the case of measuring the weight per unit area of the meltblown layer or the spunbond layer, a test piece of 10cm × 10cm was cut out from the laminated nonwoven fabric using a razor. When a test piece of 10cm × 10cm cannot be cut, a test piece having an area as large as possible is cut. The meltblown layer or spunbond layer was carefully removed from the test piece by hand or tweezers. Then, the mass of the test piece was measured, and the value obtained by dividing the mass by the area of the laminated nonwoven fabric was defined as the weight per unit area of the meltblown layer or the spunbond layer.

From the viewpoint of improving the water resistance of the laminated nonwoven fabrics 1A and 1B, the fiber diameter of the spunbond fibers 11 is preferably 35 μm or less, and more preferably 30 μm or less.

In addition, from the viewpoint of stably spinning by the spunbond method, it is realistic to set the thickness to 16 μm or more.

From the viewpoint of achieving both of these, it is preferably 16 μm or more and 35 μm or less, and more preferably 16 μm or more and 30 μm or less. The fiber diameter of the spunbond fiber 11 means the length of the major axis when the cross section of the spunbond fiber 11 has the major axis and the minor axis.

From the viewpoint of improving the water resistance of the laminated nonwoven fabrics 1A and 1B, the fiber diameter of the spunbond fibers 11 is preferably 30 μm or less, more preferably 27 μm or less, before compression by calendering or the like.

In addition, from the viewpoint of stably spinning by the spunbond method, it is realistic to set the thickness to 10 μm or more.

From the viewpoint of achieving both of these, it is preferably 10 μm or more and 30 μm or less, and more preferably 10 μm or more and 27 μm or less.

< method for measuring fiber diameter of fiber constituting spunbond layer >

3 small samples were cut out from the laminated nonwoven fabric as an object of measurement using a razor. Using SEM, focus was on the part of the spunbond layer that did not contain the embossed portion. A photograph is taken of the fibers with an observation magnification of, for example, 300 to 500 times so that 5 to 10 fibers are projected in the field of view, and the maximum value and the minimum value of the fiber diameter are measured for each fiber for all the fibers in the field of view. The average value of the fiber diameters including at least the maximum value and the minimum value of 15 or more is calculated, and the first place after the decimal point is rounded off by a micrometer, and the value obtained by the calculation is taken as the fiber diameter of the fibers constituting the spunbond layer.

The water pressure resistance of the laminated nonwoven fabric 1 is preferably 1600mmaq or more, and more preferably 1800mmaq or more, from the viewpoint that liquid does not leak through the leakage preventing material even when used as a leakage preventing material for an absorbent article.

Although not particularly limited, it is realistic to set the value to 5000mmAq.

From the viewpoint of achieving both of these, it is preferably 1600mmAq. or more and 5000mmAq. or less, and more preferably 1800mmAq. or more and 5000mmAq. or less.

The water pressure resistance can be measured by the following method.

< method for measuring Water pressure resistance >

The measurement was carried out in accordance with the Water resistance test (hydrostatic pressure method) A method (low water pressure method) of JIS L1092-1998 using a laminated nonwoven fabric as a measurement object. For the water resistance test, a nylon mesh (pore diameter: 133 μm, thickness: 121 μm, manufactured by Korea textile Co., Ltd., DO-ML-20) was superimposed on a test piece and measured. When the size of the test piece does not satisfy the predetermined specification, a device having a reduced measurement area may be assembled so that water hits the test piece having an available area, and the water pressure resistance may be measured in the same manner. The 3-ply nonwoven fabric was measured, and the average value thereof was set as the water pressure resistance of the laminated nonwoven fabric.

The laminated nonwoven fabric of the present invention can be suitably used as a laminated nonwoven fabric for an absorbent article. An absorbent article is an article mainly used for absorbing and retaining body fluids excreted from the body, such as urine and menstrual blood. Absorbent articles include, for example, but are not limited to, disposable diapers, catamenial napkins, incontinence pads, pantiliners, and the like, and broadly include articles for absorbing liquids discharged from the human body.

An absorbent article typically includes a surface material, a back material, and a liquid-retentive absorbent body interposed between the surface material and the back material.

The surface material is typically liquid permeable.

The backing material is typically liquid impermeable or hydrophobic, but may also be liquid permeable.

The laminated nonwoven fabric of the present invention is particularly suitable for a leakage preventing material of such an absorbent article. As the leakage preventing material of the absorbent article, a sheet for forming three-dimensional gathers, and the like can be cited in addition to the back material.

Fig. 5 shows an absorbent article 3 as an example of an absorbent article having a laminated nonwoven fabric of the present invention. Fig. 5(b) shows the thickness of the laminated nonwoven fabric 1 in an exaggerated manner. The absorbent article 3 has a skin-facing surface and a non-skin-facing surface on the side opposite to the skin-facing surface. The absorbent article 3 includes a liquid-permeable surface material 32 and a liquid-retentive absorbent body 34 disposed on the non-skin-facing side of the surface material 32. The laminated nonwoven fabric 1 is disposed on the non-skin-facing surface side of the absorbent body 34. The laminated nonwoven fabric 1 is used as a back material for preventing the liquid absorbed by the absorber 34 from leaking from the non-skin-facing surface of the absorbent article.

In the present specification, the "skin-facing surface" is a surface of the absorbent article or a constituent member thereof (e.g., the absorbent body 34) that faces the skin side of the wearer when the absorbent article is worn, that is, a surface that is relatively close to the skin side of the wearer, and the "non-skin-facing surface" is a surface of the absorbent article or a constituent member thereof that faces the side opposite to the skin side when the absorbent article is worn, that is, a surface that is relatively distant from the skin side of the wearer. Here, "while worn" refers to a state in which a normal proper wearing position, that is, a proper wearing position of the absorbent article is maintained.

The absorbent article 3 has the laminated nonwoven fabric 1 having high water pressure resistance on the non-skin-facing surface side of the absorbent body 34, thereby effectively preventing the liquid absorbed by the absorbent body 34 from leaking to the outside. Further, the laminated nonwoven fabric 1 is a nonwoven fabric, and thus the touch and appearance of the outer surface of the absorbent article 3 are also improved. The nonwoven fabric 1 is preferably laminated such that the spunbond layer 10 faces the non-skin-facing surface. When the laminated nonwoven fabric 1 is an SM nonwoven fabric, the meltblown layer 20 is preferably disposed on the skin-facing surface side, and the spunbond layer 10 is preferably disposed on the non-skin-facing surface side. When the laminated nonwoven fabric 1 is an SMS nonwoven fabric, any of the spunbond layers 10 may be oriented toward the non-skin-facing surface. That is, from the viewpoint of preventing damage or the like due to friction of the laminated nonwoven fabric 1, including the case where the spunbond layers 10 are provided on both sides of the meltblown layer 20, it is preferable to dispose the meltblown layer, which is formed of fibers having a fiber diameter of less than 1 μm and generally lower in strength than the spunbond fibers, on the absorbent body 34 side of the spunbond layer 10.

The absorbent article 3 shown in fig. 5 is a so-called spread-out diaper. The crotch portion A is provided at the longitudinal center portion thereof, and one of two portions extending forward and backward of the crotch portion A is a back portion B and the other is a stomach portion C. Fastening tapes 35 are provided at both side edges of the back portion B. A fastening region 36 for fixing the fastening tape 35 is provided on the non-skin-facing surface (the surface facing the opposite side of the wearer's skin when worn) of the abdominal portion C. The fastening tapes 35 are fixed to the side flap portions 31 existing on both widthwise side portions of the back side portion B. The absorbent article 3 has three-dimensional gathers 37 on both longitudinal side portions. The flap portion 31 includes a laminate of the sheet 38 for forming the three-dimensional gathers 37 and the laminated nonwoven fabric 1. The three-dimensional gather 37 forming sheet 38 has a thread-like or belt-like elastic member 62 extending in the longitudinal direction of the absorbent article 3. Further, on the outer edge portion side in the width direction of the absorbent article 3, a plurality of thread-like elastic members 63 are fixed in the longitudinal direction between the laminated nonwoven fabric 1 and the sheet 38 for forming three-dimensional gathers 37.

The absorbent article may also be a pant diaper. A pants-type diaper typically has a crotch portion at a longitudinal center portion thereof, and has a back portion as one of two portions extending forward and backward toward the crotch portion and a stomach portion as the other. The two side portions of the back side portion and the two side portions of the stomach side portion are joined to each other to form a pair of side seal portions. Further, a waist opening through which the torso of the wearer passes and a pair of leg openings through which the lower limbs of the wearer pass are formed.

Next, a method for producing a laminated nonwoven fabric according to the present invention will be described based on a preferred embodiment thereof with reference to the drawings. Fig. 6 shows an outline of an example of a method for producing the laminated nonwoven fabric 1 as one embodiment of the method for producing the laminated nonwoven fabric of the present invention. The method for producing the laminated nonwoven fabric 1 of the present embodiment includes a step of producing a laminate 2 in which the spunbond layer 10 is laminated on one surface or both surfaces of the meltblown layer 20, an embossing step of embossing the laminate 2, and a calendering step of calendering the laminate 2 (see fig. 6). In the method for producing a laminated nonwoven fabric of the present invention, either the embossing step or the calendering step may be performed first, and the calendering step may be performed after the embossing step, or the embossing step may be performed after the calendering step. In the present embodiment, the embossing step is followed by the calendering step.

The process for producing the laminate 2 includes a process for forming the spunbond layer 10 by the spunbond method and a process for forming the meltblown layer 20 by the meltblown method.

In the production method of the present embodiment, first, the spunbond fibers 11 are spun from the spinning nozzle of the 1 st spinneret 51 disposed above the conveying conveyor (not shown) and are deposited in a web shape on the conveying conveyor to form the spunbond layer 10. Next, the formed spunbond layer 10 is conveyed in one Direction (MD Direction, which is the conveying Direction) indicated by the symbol MD by a conveying conveyor (not shown). During the conveyance, the meltblown fibers 21 are spun from the spinning nozzle of the 2 nd spinneret 52 disposed above the conveyance conveyor (not shown) and directly deposited on the spunbond layer 10. Thereby, the meltblown layer 20 is formed on the spunbond layer 10, and the spunbond-meltblown laminate 2A is formed. Next, the spunbond-meltblown laminate 2A is continuously conveyed in the MD direction by a conveying conveyor (not shown). During the conveyance, the spunbond fibers 11 were spun from the spinning nozzle of the 3 rd spinneret 53 disposed above the conveying conveyor (not shown) and directly deposited on the meltblown layer 20. As a result, the spunbond layer 10 is formed on the meltblown layer 20, and a spunbond-meltblown-spunbond laminate 2 (hereinafter, also referred to as a laminate 2) is formed.

Next, an embossing process is performed. Specifically, the laminate 2 is conveyed in the MD direction, and is supplied between the mutually opposed embossing roll 54 and anvil roll 55, and the laminate 2 is subjected to embossing. The embossing step is preferably performed in a state of being heated to a temperature equal to or higher than the melting point of the spunbond fibers 11 and the meltblown fibers 21, which are fibers included in the laminate 2. By performing the embossing step in a state where the laminate 2 is heated, embossed portions for bonding the layers of the laminate 2 to each other can be formed in the laminate 2, and the layers of the laminate 2 can be integrated to form a nonwoven fabric from the laminate 2.

Next, a calendering process is performed. Specifically, the laminate 2 subjected to the embossing is conveyed in the MD direction, supplied between a pair of anvil rollers 56 and 57, and subjected to the calendering process for the laminate 2.

Anvil rolls 56, 57 used in the calendering process are typically smooth in surface.

The calendering step is preferably performed at a temperature lower than the melting point of the spunbond fibers 11 and the meltblown fibers 21 included in the laminate 2.

The laminate 2 is compressed in the thickness direction of the laminate 2 by the calendering process, and the spunbond layer 10 is in a state of being sunk into the meltblown layer 20, thereby producing the laminated nonwoven fabric 1.

The embossing step and the calendering step may be performed in different orders, but from the viewpoint of stabilizing the laminated structure of the laminated nonwoven fabric 1, it is preferable to perform the embossing step first.

According to the production method of the present embodiment, the laminated nonwoven fabric 1 having a greatly improved water pressure resistance can be easily produced.

In general, in the melt-blowing method or the spunbond method, since a resin is melt-spun, the melt-blown layer 20 or the spunbond layer 10 immediately after formation may have a temperature higher than room temperature. In the present embodiment, the calendering process may be performed on the laminate 2 after the rough heat of the laminate 2 is removed, or the calendering process may be performed on the laminate 2 before the rough heat of the laminate 2 is removed. In the present embodiment, since the calendering process is performed off-line (off-line) which is not continuous with the spinning line, the calendering process is performed after rough heat is removed. Examples of methods for removing the crude heat include: placing the laminate 2 under a temperature condition lower than the temperature of the laminate 2; blowing an air flow to the laminated body 2; off-line processing that is not continuous with the spinning line, and the like. In addition, when the calendering process is performed before the rough heat is removed, the calendering process can be performed on the laminate 2 in a soft and brittle state, and therefore, the filling ratio of the laminated nonwoven fabric 1 can be further increased, and the water pressure resistance can be further increased.

From the viewpoint of sinking the spunbond layer 10 into the meltblown layer 20, the line pressure in the calendering step is preferably 2N/mm or more, more preferably 4N/mm or more, and even more preferably 10N/mm or more.

From the viewpoint of preventing the spunbond fibers 11 from penetrating through the meltblown layer 20 and forming openings in the meltblown layer 20, they are preferably 40N/mm or less, more preferably 30N/mm or less, and still more preferably 25N/mm or less.

From the viewpoint of achieving both of these, it is preferably 2N/mm or more and 40N/mm or less, more preferably 4N/mm or more and 30N/mm or less, and still more preferably 10N/mm or more and 25N/mm or less.

The method for producing a laminated nonwoven fabric of the present invention may include a step of rolling using a pair of smooth rolls in addition to the step of producing the laminate 2, the embossing step, and the calendering step. The calendering step is different from the calendering step, and does not aim to compress the laminate or laminate the nonwoven fabric. Therefore, the linear pressure in the rolling step is generally about 1.5N/mm, which is smaller than the linear pressure in the calendering step.

The line pressure was measured by the following method.

< method for measuring line pressure >

A pressure measurement film (Prescale, manufactured by FUJIFILM corporation) was introduced between a pair of rollers used in the calendering step or the nip step. The color of the pressure measurement membrane was compared to a standard color sample and the line pressure was read. When the color of the pressure measurement membrane is the upper limit of the standard color sample, the pressure measurement membrane having a high measurable pressure range is selected and measured again.

As the raw material resins for producing the spunbond layer 10 and the meltblown layer 20, there can be mentioned: polyolefins such as polyethylene and polypropylene; polyesters such as polyethylene terephthalate; polyamides such as nylon 6 and nylon 66; polyacrylic acid, polyalkylmethacrylate, polyvinyl chloride, polyvinylidene chloride, polylactic acid, polyurethane, SIS, SEPS, and the like. These may be used alone in 1 kind or in combination of 2 or more kinds.

The base resin used to make the spunbond layer 10 can be the same as or different from the base resin used to make the meltblown layer 20.

The cross-sectional shapes of the spunbond fibers 11 and the meltblown fibers 21 include circular, triangular, rectangular, polygonal having at least a pentagon, and star-shaped ones, and among these, circular is preferable. Here, the circular shape includes not only a perfect circle but also an elliptical shape. The cross-sectional shape of the spunbond fibers 11 may be the same as or different from the cross-sectional shape of the meltblown fibers 21.

In the manufacturing method of the above embodiment, as shown in fig. 6, after a laminate 2A in which a spunbond layer 10 and a meltblown layer 20 are sequentially laminated is manufactured, spunbond fibers 11 are directly deposited on the meltblown layer 20 in the laminate 2A to form the spunbond layer 10, and the laminate 2 to be embossed is manufactured. Therefore, the produced laminated nonwoven fabric 1 has embossed portions as embossed portions, which are formed by bonding the meltblown layer 20 and the spunbond layers 10 laminated on both sides of the meltblown layer 20, and does not have an in-layer embossed portion, which is formed by compressing only the meltblown layer 20 or the spunbond layers 10 under pressure. That is, the laminated nonwoven fabric 1 includes only embossed portions that join the meltblown layer 20 and the spunbond layers 10 laminated on one or both sides of the meltblown layer 20.

When explaining the intralayer embossed portion, a spunbond nonwoven fabric is generally produced as follows: after the spunbond fibers are spun to form a spunbond layer, the spunbond layer is embossed, typically by heat embossing. Thus, typically a spunbond layer has an in-layer embossing that bonds the fibers within the spunbond layer to one another.

From the viewpoint of maintaining excellent flexibility as a nonwoven fabric, the laminated nonwoven fabric of the present invention preferably has no such an intralayer embossed portion, and has only an embossed portion for bonding between the meltblown layer 20 and the spunbond layer 10 located on one side or both sides of the meltblown layer 20.

The method for producing a laminated nonwoven fabric having only embossed portions for bonding the meltblown layer 20 and the spunbond layer 10 is not limited to the above embodiment, and may be, for example, the following method. First, after the melt-blown layer 20 is formed, the spunbond layer 10 is formed by directly depositing the spunbond fibers 11 on the melt-blown layer 20, and the laminate 2A is manufactured in this order from the melt-blown layer 20 and the spunbond layer 10. Next, the manufactured laminate 2A is turned upside down. Thereafter, the spunbond layer 10 was formed on the meltblown layer 20 in the laminate 2A, and the subsequent steps were performed in the same manner as in the above embodiment, thereby producing the laminated nonwoven fabric 1.

As described above, from the viewpoint of productivity, the step of producing the laminate preferably includes the steps of: after forming one of the melt-blown layer and the spunbond layer, the fibers forming the other layer are directly deposited on the one layer to form the other layer.

The laminated nonwoven fabric of the present invention has been described above based on a preferred embodiment thereof, but the laminated nonwoven fabric of the present invention is not limited to the above embodiment.

For example, the laminated nonwoven fabric 1 of the above embodiment has the spunbond layers 10 laminated on both surfaces of the meltblown layer 20, but the spunbond layers 10 may be laminated only on one surface of the meltblown layer 20.

In the manufacturing method of the above embodiment, the spunbond layer 10, the meltblown layer 20 and the spunbond layer 10 are formed in this order to form the laminate 2 having a 3-layer structure, but the spunbond-meltblown laminate 2A may be subjected to the embossing step and the calendering step without forming the final spunbond layer 10. In this case, a laminated nonwoven fabric is produced in which the spunbond layer 10 is laminated on one surface of the meltblown layer 20. The spunbond-meltblown laminate 2A may be produced by forming the meltblown layer 20 by directly depositing the meltblown fibers 21 on the spunbond layer 10 after the spunbond layer 10 is formed, or may be produced by forming the spunbond layer 10 by directly depositing the spunbond fibers 11 on the meltblown layer 20 after the meltblown layer 20 is formed.

In the above embodiment, the spunbond layer 10 and the meltblown layer 20 are formed in the same production line, but the spunbond layer 10 and the meltblown layer 20 may be formed in different production lines instead. Specifically, the meltblown layer 20 may be formed by depositing the meltblown fibers 21 in a web-like manner on a spunbond layer 10 previously formed in a different production line. Alternatively, the spunbond layer 10 and the meltblown layer 20 may be formed in advance in different production lines, and the spunbond layer 10 and the meltblown layer 20 may be laminated to form the laminate 2. Alternatively, a laminate 2 in which the spunbond layer 10 is laminated only on one side of the meltblown layer 20 may be subjected to calendering, and the spunbond layer 10 may be laminated on the opposite side of the laminate to produce a 3-layer laminated nonwoven fabric.

A preferred embodiment of the method for manufacturing an absorbent article of the present invention includes the steps of: the surface material 32, the absorber 34, and the laminated nonwoven fabric 1 are laminated in this order in the thickness direction. The laminated nonwoven fabric 1 is produced by the method for producing a laminated nonwoven fabric of the present invention. The laminated nonwoven fabric 1 is disposed such that the spunbond layer 10 is located on the surface opposite to the surface facing the absorbent body 34. In this lamination step, the order of laminating the surface material 32, the absorbent body 34, and the laminated nonwoven fabric 1 is not particularly limited as long as an absorbent article in which the surface material 32, the absorbent body 34, and the laminated nonwoven fabric 1 are laminated in this order from the skin facing surface side toward the non-skin facing surface side is finally manufactured. For example, the laminated nonwoven fabric 1 may be laminated after laminating the topsheet 32 and the absorbent body 34, the topsheet 32 may be laminated after laminating the absorbent body 34 and the laminated nonwoven fabric 1, or the topsheet 32, the absorbent body 34, and the laminated nonwoven fabric 13 may be laminated at the same time.

Examples

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

(example 1)

After the spunbond layer (S) is formed, meltblown fibers are deposited directly on the spunbond layer (S) to form a meltblown layer (M). Then, the spunbond fibers are directly deposited on the formed meltblown layer (M) to form a spunbond layer (S). In this manner, a laminate in which the spunbond layer (S), the meltblown layer (M), and the spunbond layer (S) are laminated in this order is produced. Next, the laminate was subjected to embossing and then to calendering, to obtain a laminated nonwoven fabric of example 1. The laminated nonwoven fabric of example 1 had no in-layer embossed portions, and only embossed portions for bonding the meltblown layer to the spunbond layers laminated on both sides of the meltblown layer. Both spunbond layers were composed of fibers comprising polypropylene resin and the meltblown layer was composed of fibers comprising polypropylene resin. The line pressure at which the spunbond layers were calendered and the dimensions of the portions of example 1 are shown in table 1.

[ Table 1]

(examples 2 to 5)

A laminated nonwoven fabric was produced in the same manner as in example 1, except that the linear pressure during calendering was changed as shown in table 1. The laminated nonwoven fabrics of examples 2 to 6 had no in-layer embossed portions, and only embossed portions for bonding the meltblown layer to the spunbond layers laminated on both sides of the meltblown layer.

(example 6)

A laminated nonwoven fabric was produced in the same manner as in example 1, except that the basis weight of the nonwoven fabric constituting the spunbond layer and the line pressure at the time of calendering were changed as shown in table 1. The laminated nonwoven fabric of example 6 had no in-layer embossed portions, but only embossed portions for bonding the meltblown layer to the spunbond layers laminated on both sides of the meltblown layer.

(example 7)

A laminated nonwoven fabric was produced in the same manner as in example 1, except that the line pressure at the time of calendering and the fiber diameter of the meltblown fibers were changed as shown in table 2. The laminated nonwoven fabric of example 7 had no in-layer embossed portions, but only embossed portions for bonding the meltblown layer to the spunbond layers laminated on both sides of the meltblown layer.

Comparative example 1

The meltblown nonwoven fabric of comparative example 1 was produced by calendering the meltblown nonwoven fabric. The dimensions of each part of the meltblown nonwoven fabric of comparative example 1 are shown in table 1.

Comparative example 2

The meltblown nonwoven fabric of comparative example 2 was produced in the same manner as in comparative example 1, except that calendering was not performed. The dimensions of each part of the meltblown nonwoven fabric of comparative example 2 are shown in table 1.

Comparative example 3

A laminated nonwoven fabric of comparative example 3 was produced in the same manner as in example 1, except that the calendering process was not performed.

Comparative examples 4, 6 and 8

Meltblown nonwoven fabrics of comparative examples 4, 6 and 8 were produced in the same manner as in comparative example 1 except that the line pressure and the fiber diameter of the meltblown fibers during calendering were changed as shown in table 1.

Comparative example 5

A laminated nonwoven fabric of comparative example 5 was produced in the same manner as in example 1, except that the line pressure during calendering and the fiber diameter of the meltblown fibers were changed as shown in table 1.

Comparative example 7

A laminated nonwoven fabric of comparative example 7 was produced in the same manner as in example 1, except that the fiber diameter of the meltblown fibers was changed as shown in table 1.

Comparative example 9

A laminated nonwoven fabric of comparative example 9 was produced in the same manner as in example 1, except that the linear pressure at the time of calendering was changed as shown in table 1.

The nonwoven fabrics obtained in examples 1 to 7 and comparative examples 1 to 9 were subjected to measurement of water pressure resistance by the above-described method, and skin touch was evaluated by the following method. The measurement results of water pressure resistance and the evaluation results of skin touch are shown in table 1.

< method for evaluating touch feeling of skin >

The laminated nonwoven fabric was compressed at maximum 5kPa in a normal mode, except that a KES compression tester (KES FB-3 manufactured by Kyowa Kagaku Co., Ltd.) was used, and the terminal speed was set to 0.1mm/s, to measure the compression rigidity, that is, LC. The closer the LC value is to 1, the harder it is, and therefore the smaller the value, the better the skin feel.

As shown in table 1, the laminated nonwoven fabrics of examples 1 to 7 had water pressure resistance of 1600mmaq. or more, which was significantly improved as compared with the laminated nonwoven fabric of comparative example 3, which was not calendered, and the single-layer meltblown nonwoven fabrics of comparative examples 1, 2, 4, 6, and 8.

The above ratio t of the laminated nonwoven fabric of comparative example 3 which was not calendered_max/t_min1.3, the laminated nonwoven fabric of comparative example 9, which was calendered under a condition of a low line pressure, had the above ratio t_max/t_minThe ratio t of the laminated nonwoven fabrics of examples 1 to 6 was 2.0_max/t_minAbove 2, it is considered that it contributes to the improvement of the water pressure resistance of the laminated nonwoven fabric of the present invention.

The laminated nonwoven fabric of comparative example 3, which was not subjected to calendering, had a filling factor of 6.7, whereas the laminated nonwoven fabrics of examples 1 to 6 had a filling factor of 10 or more, which is considered to contribute to the improvement in the water pressure resistance of the laminated nonwoven fabric of the present invention.

From the comparison of comparative examples 5 and 6, the comparison of comparative examples 7 and 8, and the comparison of example 7 and 4, it was confirmed that when the fiber diameter of the meltblown fiber was less than 1 μm, the effect of improving the water pressure resistance achieved by laminating the spunbond layer and the meltblown layer and performing calendering was exhibited. In comparative examples 7, 5, 7 and 1, the fiber diameters of the fibers of the meltblown layer were 1.1 μm, 1.0 μm, 0.9 μm and 0.8 μm in this order, and the water pressure resistance was dramatically improved when the fiber diameter was less than 1.

From these results, it is important that the fiber diameter of the meltblown fibers is less than 1 μm and at least one of the above conditions (1) and (2) is satisfied in order to exhibit high water pressure resistance in the laminated nonwoven fabric of the present invention.

Further, the results of evaluation of the filling ratio and the feel to the skin of the laminated nonwoven fabrics of examples 1 to 4 were observed, and it was confirmed that the water pressure resistance tended to increase as the filling ratio increased. From the viewpoint of achieving both the water pressure and the texture, it is preferable to suppress the filling ratio of the laminated nonwoven fabric to 35% or less so that a good texture equivalent to that of the laminated nonwoven fabric of comparative example 3, which is not subjected to the calendering, can be obtained.

In the laminated nonwoven fabric of comparative example 3 in which calendering was not performed, the ratio of the maximum fiber width of the spunbond fibers to the minimum fiber width was 1.1, whereas in the laminated nonwoven fabrics of examples 1 to 7 and comparative example 9 in which calendering was performed, the ratio of the maximum fiber width of the spunbond fibers to the minimum fiber width (maximum fiber diameter/minimum fiber diameter) was 1.4 or more and 2.2 or less. It is shown that the laminated nonwoven fabrics of examples 1 to 7 and comparative example 9 have regions where the spunbond fibers are largely flattened by calendering. In addition, the laminated nonwoven fabrics of examples 1 to 7 have a larger ratio of the maximum fiber width to the minimum fiber width of the spunbond fibers than the laminated nonwoven fabric of comparative example 9 which was calendered under a low line pressure condition. In the laminated nonwoven fabrics of examples 1 to 7, calendering was performed with sufficient line pressure, and the spunbond fibers were present in a largely flat region, so that the surface of the meltblown layer could be covered with a larger area, which is also considered to contribute to improvement in water pressure resistance.

As shown in table 1, in examples 1 to 7, a part of the cross-sectional shape of the meltblown fibers was elliptical, and the cross-sectional shape of the spunbond fibers was also elliptical. The term "partially elliptical shape" (in table 1, "partially elliptical") means a portion having a cross-sectional shape of a perfect circle or a substantially perfect circle and a portion having an elliptical shape. On the other hand, in comparative example 3, the cross-sectional shape of the meltblown fiber was a perfect circle, and the cross-sectional shape of the spunbond fiber was a substantially perfect circle. It shows that the fibers of the layers are deformed into an oval shape by the calendering process. Thus, the spunbond fibers can cover the surface of the meltblown layer with a larger area, which is also believed to contribute to the improved water pressure resistance.

(examples 8 to 11)

A laminated nonwoven fabric was produced in the same manner as in example 1, except that the linear pressure during calendering and the fiber diameter of the spunbond fibers before calendering were changed as shown in table 2. The laminated nonwoven fabrics of examples 8 to 11 had no in-layer embossed portions, and only embossed portions for bonding the meltblown layer to the spunbond layers laminated on both sides of the meltblown layer.

Comparative example 9

A laminated nonwoven fabric of comparative example 9 was produced in the same manner as in example 1, except that the line pressure of the calendering process was changed as shown in table 2.

[ Table 2]

The water pressure resistance was measured by the above-described method for examples 8 to 11 and comparative example 9. In addition, the skin feel was evaluated by the above-described method for examples and comparative examples. The measurement results of water pressure resistance and the evaluation results of skin touch are shown in table 2.

Comparing the results of example 8 and example 9, although the line pressure at the time of calendering of example 9 was higher than that of example 8, the water pressure resistance of example 8 was improved compared to that of example 9. This is considered to be because the spunbond in example 8 has finer fibers than in example 9, and therefore the spunbond layer has a higher fiber density and a narrower fiber-to-fiber distance, and therefore the pitch of the restrained meltblown fibers becomes shorter and the meltblown fibers are further fixed. From the viewpoint of improving the water pressure resistance, the fiber diameter of the spunbond fibers is preferably 35 μm or less.

Industrial applicability

According to the laminated nonwoven fabric of the present invention, a laminated nonwoven fabric having improved water pressure resistance can be provided.

According to the method for producing a laminated nonwoven fabric of the present invention, a laminated nonwoven fabric having improved water pressure resistance can be produced.