JP2843123B2 - Surface sheet for absorbent article and method for producing the same - Google Patents

Description

The present invention relates to a surface sheet of an absorbent article. More specifically, the present invention relates to a surface sheet of a disposable absorbent article, such as a sanitary napkin, a disposable diaper, or an incontinence pad, which forms a surface in contact with a user's skin.

(Prior Art) In general, as a sheet of this type, a body fluid quickly penetrates into an article without oozing or diffusing into the surface of the article, and the body fluid once absorbed into the article is used by a user. It is required to reduce the possibility of backflow to the surface due to the body pressure to wet the skin of the user, and also to improve the texture.

Conventionally, in order to impart such required performance to the topsheet, the topsheet is composed of a surface layer in contact with the skin of the user and a back layer not in contact with the skin, and the density of the surface layer is increased to form a dense paper, Techniques of forming a large amount of space by lowering the density of the back layer are disclosed in, for example, JP-A-58-55788 and JP-A-61-23949, while the fibers constituting the surface layer and the back layer are fused to each other. Japanese Patent Application Laid-Open No. Sho 64-20844 discloses a technique in which the density of the surface layer is lower than that of the back layer. In addition, it is a well-known technique to use a perforated plastic film for a topsheet.

(Problems to be Solved by the Invention) It is difficult to simultaneously satisfy all the required performances with the surface sheet according to the above-mentioned known technology. For example, in the technique of forming a dense paper with a high density of the surface layer, rapid penetration of the body fluid to the back surface cannot be obtained, and the body fluid that stays forever on the top surface of the surface layer may give a discomfort to the wearer.

On the other hand, in the above-mentioned technology in which the density of the surface layer is made lower than that of the back layer, although a certain permeation effect is recognized, the permeation of bodily fluids from the surface layer to the back layer and from the back layer to the absorbers arranged on the lower surface is reduced. Relying exclusively on capillary action, the fibrous tissue is prone to clogging and is not sufficiently fast to penetrate. It is possible to perform an active agent treatment to make the fibers hydrophilic in order to promote penetration, but since the active agent is flushed with the penetration of bodily fluids, the effect is less persistent and sometimes the active agent is worn by the wearer. May also irritate the skin.
Therefore, there is also a need to be able to effectively penetrate body fluids without resorting to activator treatment.

Accordingly, the present invention provides a topsheet of an absorbent article made of a fiber entangled nonwoven fabric containing at least a first fiber and a second fiber, and aims to solve the above problems.

(Means for Solving the Problems) The following is a summary of the configuration of the topsheet according to the present invention in solving the above problems.

In the topsheet, at least a surface layer in contact with the skin includes first hydrophobic fibers, and a back layer thereof includes second hydrophobic fibers.
The second fiber is constituted by a fiber having a smaller denier than the first fiber. A plurality of openings penetrate between the surface layer and the back layer. The diameter of the opening is 0.5 mm or more, and the opening ratio is 20 to 50%. Further, the topsheet is provided with a projection extending downward from the back layer near the periphery of the opening.

(Operation) In the topsheet configured as described above, it is made of a fiber entangled nonwoven fabric, and it is possible to give a soft feel with little irritation to the wearer's skin.
Corresponding to).

The bodily fluid penetrates into the absorber through the opening in the topsheet,
The size of the opening can be selected so as not to be easily clogged by the body fluid (corresponding to claim 1).

Reducing the denier of the second fiber of the back layer, compared to the first fiber of the surface layer, allows for the formation of sharply defined apertures, which reduce the resistance to passage of bodily fluids. Helps promote body fluid penetration. At the same time, the density can be increased from the surface layer to the back layer, and body fluid permeation is also promoted by giving such a gradient to the density. Therefore, stagnation of bodily fluids on the top surface of the topsheet is reduced, and discomfort during wearing is eliminated (corresponding to claim 1).

The back layer has a hydrophilic third fiber in addition to the hydrophobic second fiber.
When the fiber is included, the permeability from the surface layer to the back layer is further improved. The permeated bodily fluid is retained in the back layer by the water absorbing power of the third fiber, while the hydrophobicity of the second fiber prevents backflow (also called re-wet) of the bodily fluid once permeated into the back layer to the surface layer. As a result, the dry touch feeling on the surface layer is improved, and the discomfort during wearing is more effectively eliminated (corresponding to claim 3).

The protrusions provided near the periphery of the opening help the body fluid to penetrate from the topsheet to the absorber by capillarity by keeping the tip in contact with the absorber, and the body fluid diffused into the absorber is Prevents backflow to the topsheet and reduces backflow (re-wet amount) to the topsheet. These projections have the effect of separating the topsheet and the absorber from each other, and also give the topsheet a good touch cushioning property (corresponding to claim 2).

If the permeability of the topsheet is improved as described above, the hydrophilic treatment of the topsheet is not necessarily required (corresponding to claims 1 to 3).

A surface sheet having the above-mentioned properties can be obtained by using a known fiber-entangled nonwoven fabric. It is easy to form (corresponding to claim 4).

Next, an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment) FIG. 1 is a perspective view of a topsheet 1 according to an embodiment of the present invention.

The topsheet 1 is obtained from the nonwoven fabric 1A, is mainly composed of the first fibers 2 contained in the surface layer and the second fibers 3 mainly contained in the back layer, and has a plurality of openings 4 penetrating the front and back of the sheet 1. Having. The first fibers 2 are selected from polyolefin fibers, polyester fibers, or other hydrophobic fibers, or mixtures or composite fibers thereof, and have a fineness of 3 denier or less and a basis weight of 5 to 20 g / m ² . The second fiber 3 is selected from the same fibers as the first fiber 2,
The fineness is preferably set to a denier of 1/5 or less of the first fiber ² and is used at a basis weight of 15 to 45 g / m ² . Fibers having a low denier number for this purpose include, for example, melt blown fibers and split fibers.

The opening 4 does not specify its planar shape,
In general, it is preferable to have a substantially convex shape such as a circle, an ellipse, or an ellipse in appearance and the like. The opening 4 has a hole diameter d of 0.5 mm or more and an opening ratio in the range of 20 to 50%. The hole diameter d is defined as the distance between two tangents parallel to the longest chord L at the opening 4 and sandwiching the longest chord L. The hole diameter d is equal to the diameter of the opening 4 if it is a circle, and is equal to its minor diameter if it is an ellipse or an ellipse.

The nonwoven fabric 1A is a fiber entangled nonwoven fabric, and can be obtained by a fluid fiber entanglement method known in the production of nonwoven fabrics, preferably a water flow fiber entanglement method. The perforation of the opening 4 is a secondary processing for the nonwoven fabric 1A, and the heating needle is
Alternatively, a method of melting the fibers may be used, but more preferably, the fiber is entangled simultaneously with the fiber entanglement using a fiber entanglement treatment using a fluid. For example, in the case of the above-mentioned hydrofiber entanglement method, a fiber web composed of the second fiber 3 is superimposed on a support (not shown) having a projection as a forming element of the opening 4 and a large number of drainage holes. And a high-pressure water of 50 to 80 kg / cm ² is applied from a large number of injection nozzles to cause the fibers to be entangled and moved at the same time, thereby forming a nonwoven fabric 1A having openings 4. Obtainable.

FIG. 2 is a cross-sectional view taken along the line II-II of FIG. 1. The surface sheet 1 mainly includes the first fibers 2 and the back layer mainly includes the second fibers 3, and both fibers are entangled between the layers.

In the case of the fluid fiber entanglement method as described above,
Although the fibers 3 may be mixed with the first fibers 2 in the back layer, the first fibers 2 are not buried in the second fibers 3 in the surface layer, and the second fibers 3 are replaced with the first fibers 2 in the back layer. The object of the present invention can be achieved as long as it is not buried.
The back layer containing many fibers having a small denier number can be formed at a higher density than the surface layer. The cross-sectional shape of the opening 4 is
It follows the shape of the projection on the support in which the opening 4 is formed, and usually expands from the surface layer to the back layer.

FIG. 3 shows another embodiment of the present invention, in which the support has an elliptical opening 4 obtained by using a 10-400 mesh wire mesh (not shown) made of stainless steel wire described later. 2 shows the upper surface of the non-woven fabric 1A.

FIG. 4 and FIG. 5 are respectively IV-IV in FIG.
It is a typical sectional view of a line and a VV line. In each cross-sectional view, the nonwoven fabric 1A has a surface layer mainly including the first fibers 2 and a back layer mainly including the second fibers 3, and the fibers are entangled with each other between the layers.

FIG. 5A is a perspective view extremely schematically showing the surface shape of the back layer of the nonwoven fabric 1A for easy understanding. The surface is constituted by an opening 4, a thin portion 15 and a rib-like projection 5.

FIG. 6 shows a cross section of the wire mesh support 50 contributing to the formation of this cross section together with a cross section taken along line VV of the nonwoven fabric 1A shown in FIG. In the figure, a support 50 is made of a stainless steel wire, and includes a warp wire 51 and weft wires 61 to 64. The structure of the wire mesh when viewed in plan is a plain weave (not shown). The gap has a function as a drain hole. Wire 51 is a wire
The portion floating above 62 and 64 is a raised portion 53. Wire 51 is wire 6
The valley 54 is formed on the both sides of each of the wire rods 61 and 63 in the part which sinks below 1,63. Although not shown, the valley
In 54, voids serving as drain holes are formed on both sides of the wire 51. The nonwoven fabric 1A indicated by the two-dot chain line corresponds to the sectional view of FIG. When the web supplied to the support 50 is subjected to high-pressure jet water treatment by a large number of nozzles, the constituent fibers of the web are moved to the periphery at the raised portion 53 and the opening 4 is formed.
Then, some fibers flow into the valley 54 together with the flow of drainage, and the projections 5 are formed. As shown in FIGS. 4 to 5A, the vicinity of the periphery of the opening 4 is constituted by a relatively thin portion, a projection 5 extending in a hook-like pattern, and the like.
The protrusion 5 extends downward from the back layer of the nonwoven fabric 1A near the periphery of the opening 4.

In order to obtain the nonwoven fabric 1A, the web made of the second fiber 3 is placed on the support 50 as described above, and the web made of the first fiber is supplied on the support 50, or
When the web of the first fiber 2 is supplied first and then the web of the first fiber 2 is supplied, the second side of the nonwoven fabric 1A mainly
A backing layer containing fibers is formed, especially at the tips of the projections 5.
It is possible to increase the ratio including the fibers 3. On the surface side, a surface layer mainly including the first fibers 2 is formed. Both fibers are entangled with each other between the layers.

The openings 4 and the projections 5 are formed particularly clearly when the second fibers 3 having a small denier are used with a predetermined basis weight, and the above-mentioned melt-blown fibers are particularly suitable. The nonwoven fabric 1A is cut into appropriate dimensions and used as the topsheet 1.

Table 1 below shows the evaluation results of various surface sheets and comparative examples obtained by the method of the present example in order to determine comfort when wearing the article. As a guide for evaluation, the amount of re-wet, dry touch feeling and permeability were taken from artificial urine. The opening 4 is formed in a substantially elliptical shape in any of the topsheets, and attention was paid to the size of the minor axis in the evaluation.

The description of each item and abbreviation in Table 1 is as follows.

(A) Regarding the first fiber; i) EP: core-sheath type conjugate fiber composed of polyethylene and polypropylene, fineness 1.5d ii) BF-1: polyethylene fiber fineness 0.1d iii) BF-2: polyethylene fiber fineness 0.3 d iv) PP-1: polypropylene fiber fineness 0.7 d v) PP-2: polypropylene fiber fineness 1.5 d vi) PET-1: polyester fiber fineness 0.7 d vii) PET-2: polyester fiber fineness 1.4 d (b) second About the fiber; MB: polyethylene melt blown fiber Fineness 0.06d (c) Re-wet amount: The method for obtaining the re-wet amount is as follows: (i) A surface sheet test piece is 150 x 400 mm in size and this is ground pulp. (Ii) 100 cc of artificial urine is injected into the center of the test piece in about 9 seconds, (iii) 5 minutes after the start of injection, 100 × 100 mm filter paper of known weight Four
0 sheets and a 3.5 kg weight are placed on the injection site for 3 minutes. (Iv) Then, leave it for 2 minutes, and repeat (ii) and (iii) above.
Is repeated, and the re-wet amount is calculated by the following equation.

(D) dry touch feeling; (i) in the measurement of the (c) re-wet amount;
The operation of (ii) was performed, and the dryness of the test specimen 3 minutes after the start of the injection was evaluated by touch.

(E) permeability; (i) in the measurement of the (c) re-wet amount,
The operation of (ii) was performed, and the speed of penetration of artificial urine was visually evaluated.

(F) Symbol of evaluation: ◎ Very good ○ Good × Bad Test item 1 shows that the re-wet amount is reduced and the dry touch feeling is improved by setting the basis weight of the first fiber to 5 g / m ² or more. . The dry touch feeling is improved by increasing the number of hydrophobic fibers having a large diameter in the surface layer.

Test item II shows that the dry touch feeling is improved by making the fineness ratio (denier number of first fiber / denier number of second fiber) larger than 5. It is preferable to use a fiber having a smaller denier for the second fiber than for the first fiber.

Test item III indicates that the permeability is improved when the minor diameter of the opening is 0.5 mm or more.

Test items IV are all comparative examples, and show the evaluation results of the topsheet composed of only the first fibers or the second fibers. The surface sheet is made of only the first fiber (denier: 1.5 denier), and the contour of the opening is not clearly formed, and the shape of the opening is broken due to the tendency to disturb, and the effect of the opening on the permeability is extremely poor. If the topsheet is made of only low-denier fibers, there will be a lot of body fluid held between the fibers,
The wet amount increases and the dry touch feeling deteriorates.

FIG. 7 shows yet another embodiment of the present invention. The outer shape of the topsheet 1 is the same as that of the nonwoven fabric 1A shown in FIG. 3, but includes a hydrophilic third fiber 6 in its back layer, and its end face is shown similarly to FIG. As the third fibers 6, fibers such as rayon, cotton, and pulverized pulp can be used at a ratio of 5 to 30 g / m ² . In order to obtain the nonwoven fabric 1A, the above-described hydroentanglement method is used. Many third fibers 6 are gathered at the tip of the protrusion 5.

FIG. 8 is an end view showing an example in which the above-mentioned topsheet 1 is used as the topsheet of the disposable diaper 10, and for convenience of explanation, only a part of the topsheet 1 is schematically shown with particularly exaggerated dimensions. In the figure, a diaper 10 is composed of a top sheet 1, an absorber 11, and a back sheet 12 in the thickness direction. Absorber
No. 11 is formed by mixing and compressing pulverized pulp, superabsorbent polymer, thermoplastic fiber, etc., and has excellent body fluid absorption and diffusion properties. The back sheet 12 is made of a water-impermeable plastic film. The tip of the protrusion 5 comes into contact with the absorber 11, and the body fluid penetrates from the surface layer of the topsheet 1 to the absorber 11, prevents the bodily fluid permeated and diffused into the absorber 11 from flowing back to the topsheet 1, and the topsheet. This is useful for separating the one from the absorber 11.

(Effect) The topsheet of the present invention allows body fluid to penetrate into the absorbent body through the openings and also permeates by capillary action between the surface layer and the back layer, thereby obtaining a rapid body fluid penetration rate. The back layer is a fiber having a small denier, and when a hydrophilic fiber is appropriately contained therein, the bodily fluid penetrates more easily from the surface layer to the back layer, but hardly flows back to the surface layer. Therefore, even if hydrophobic fibers are used for the topsheet, it is not always necessary to promote the permeation of bodily fluids by hydrophilizing the fibers with an activator.

Providing a projection on the periphery of the opening effectively prevents the backflow of the bodily fluid that has permeated and diffused into the absorber and reduces the amount of re-wetting. In addition, since the topsheet is separated from the wet absorber, the dry touch feeling of the topsheet is improved together with the hydrophobic fiber having a large denier number forming the surface layer. The projections also have the effect of giving the topsheet a bulky feeling and cushioning properties.

When the fluid fiber entanglement treatment is used to obtain the topsheet, the formation of the top layer and the back layer of the topsheet and the formation of the openings and the projections are easy.

[Brief description of the drawings]

1 and 2 show a topsheet according to an embodiment of the present invention and a cross-sectional view taken along the line II-II. FIGS. 3 to 5 show topsheets according to other embodiments of the present invention. IV-IV line and VV line sectional view, FIG. 5A is a schematic diagram showing the back side of FIG. 3,
FIG. 6 is a sectional view showing the structure of a support, and FIGS. 7 and 8 are sectional views showing still another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1 ... Top sheet, 2 ... 1st fiber 3 ... 2nd fiber, 4 ... Opening 5 ... Projection, 6 ... 3rd fiber 50 ... Support body (mesh) 51, 61, 62, 63 , 64 ... wire d ... hole diameter

Claims (4)

(57) [Claims] 1. A surface sheet of an absorbent article comprising a fiber entangled nonwoven fabric, wherein at least a surface layer in contact with the skin contains a hydrophobic first fiber, and a back layer contains a hydrophobic second fiber,
And, the second fiber is constituted by a fiber having a smaller denier than the first fiber, a plurality of openings penetrate between the surface layer and the back layer, and the hole diameter of the openings is 0.5 mm or more. The surface sheet of the absorbent article, wherein the porosity is 20 to 50%. 2. The topsheet according to claim 1, wherein the nonwoven fabric has a projection extending downward from the back layer near the periphery of the opening. 3. The topsheet according to claim 1, wherein the back layer contains hydrophilic third fibers in addition to the second fibers. 4. The method of manufacturing a surface sheet for an absorbent article according to claim 1, wherein the openings and the projections are formed using a mesh made of a wire in a fluid fiber entanglement treatment step for obtaining the nonwoven fabric. Method.