JP2013180171A - Absorbent article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an absorbent article excellent in the liquid permeability and liquid diffusivity, and highly efficient in utilizing an absorber.SOLUTION: An absorbent article 1 includes an absorber 4 and a front surface sheet 2 disposed on a skin facing side of the absorber 4. The absorber 4 includes an absorbent core 40 containing an absorbent material, and a core wrapping sheet 5A covering at least the skin facing surface 40a of the absorbent core 40. The core wrapping sheet 5A includes a first layer 51 and a second layer 52 layered on the first layer. The first layer 51 is located at a position closer to the front surface sheet 2 than the second layer 52. Relations among a liquid permeating time T1 of the front surface sheet 2, a liquid permeating time T2 of the first layer 51, a liquid permeating time T3 of the second layer 52 and a liquid permeating time T4 of the absorbent core 40 are: T3>T4>T1≥T2.

Description

  The present invention relates to absorbent articles such as disposable diapers and sanitary napkins.

  As an absorbent article of this type, it comprises a liquid-permeable surface sheet that forms a skin-facing surface, a liquid-impermeable back sheet that forms a non-skin-facing surface, and an absorbent body disposed between these two sheets, It is known that the absorbent body includes an absorbent core containing an absorbent material such as wood pulp and a water-absorbing polymer, and a core wrap sheet that covers the absorbent core. The core wrap sheet serves as a sheet for receiving the absorbent material during the production of the absorbent body, and plays a role of wrapping the absorbent core and shaping it after the production. Conventionally, water-permeable sheets such as thin paper, absorbent paper, and nonwoven fabric are used as the core wrap sheet.

  Regarding the absorbent article having the above-described configuration, Patent Document 1 includes a permeable sheet that transmits excretory fluid between a top sheet and an absorbent element (absorber). The absorbent article in which the stool permeation rate S2 and the stool permeation rate S3 on the surface of the absorbent element have a relationship of S1> S2> S3 is described, and the component closer to the skin side of the wearer has a higher stool permeation rate The application of a stool permeation velocity gradient to an absorbent article is described. Regarding the surface layer of the absorbent element, Patent Document 1 describes that a surface layer sheet made of a perforated sheet made of plastic separate from the absorbent core and the core wrap sheet is used. According to the absorbent article described in Patent Document 1, it is said that the soft stool can be quickly moved away from the skin and reliably held and held at a position far from the skin by the soft stool permeation speed gradient.

Japanese Patent Laid-Open No. 2006-141647

  Although conventional absorbent articles have an absorbent body with a sufficient absorption capacity that can absorb a large amount of excretory fluid, it cannot be said that the liquid permeability and liquid diffusibility are sufficient, so that it absorbs during use. In some cases, only part of the body contributed to the absorption and retention of excretory fluid. Absorptive articles that can efficiently absorb and retain an absorbent body with respect to excreted liquid such as urine and are unlikely to cause trouble such as liquid return have not yet been provided.

  Therefore, the subject of this invention is providing the absorbent article which is excellent in liquid permeability and liquid diffusibility, and whose utilization efficiency of an absorber is high.

  As a result of various investigations on the skin-side constituent members that include the absorbent core and are positioned closer to the wearer's skin than the constituent members of the absorbent article, in order to increase the utilization efficiency of the absorbent body, the present inventors The core wrap sheet placed between the top sheet and the absorbent core is layered on the first layer (placed on the top sheet side) and the first layer with which the liquid first comes into contact (placed on the absorbent core side) The first layer has the fastest liquid permeation rate, and the second layer has the slowest liquid permeation time. It has been found that the liquid permeability and liquid diffusibility of the entire core wrap sheet are improved by adjusting so as to improve the utilization efficiency of the absorber.

The present invention has been made based on the above knowledge, and comprises an absorbent body and a surface sheet disposed on the skin-facing surface side of the absorbent body, and the absorbent body includes an absorbent core containing an absorbent material; An absorbent article comprising a core wrap sheet covering at least a skin-facing surface of the absorbent core, wherein the core wrap sheet includes a first layer and a second layer superimposed on the first layer. The first layer is located closer to the top sheet than the second layer, and the liquid permeation time T1 measured by the following method of the top sheet, the liquid of the first layer. By providing an absorbent article in which the permeation time T2, the liquid permeation time T3 of the second layer, and the liquid permeation time T4 of the absorbent core are in the relationship of T3>T4> T1 ≧ T2, It has been solved.
<Measurement method of liquid permeation time>
Two cylinders with an inner diameter of 35 mm that open at the top and bottom are arranged vertically with the axes of both cylinders aligned, and an 8 cm square measurement sample is sandwiched between the upper and lower cylinders. 40 g ± 1 g of physiological saline is supplied. The supplied physiological saline passes through the measurement sample or is absorbed by the measurement sample and disappears from the upper cylinder. The time from the start of the physiological saline supply until the physiological water surface becomes the same position as the surface of the measurement sample is measured, and this time is defined as the liquid permeation time.

  ADVANTAGE OF THE INVENTION According to this invention, the absorbent article which is excellent in liquid permeability and liquid diffusibility, and has high utilization efficiency of an absorber is provided.

FIG. 1 is a view showing a disposable diaper which is an embodiment of the absorbent article of the present invention, and schematically shows a state where the elastic member of each part is stretched and expanded in a planar shape (surface sheet) FIG. 2 is a cross-sectional view schematically showing a cross section taken along line II (cross section in the width direction) of FIG. FIG. 3 is an enlarged cross-sectional view schematically showing a part of FIG. 2 (core wrap sheet and its vicinity). FIG. 4 is an explanatory diagram of a method for measuring the liquid permeation time. FIG. 5 is a view corresponding to FIG. 2 of another embodiment of the absorbent article of the present invention. FIG. 6 is a perspective view schematically showing an enlarged part of another embodiment of the topsheet according to the present invention. FIG. 7 is a cross-sectional view schematically showing a cross section in the width direction of the absorbent article of the present invention provided with the topsheet shown in FIG. Fig.8 (a) is a perspective view which shows other embodiment of the absorptive core which concerns on this invention, FIG.8 (b) is a III-III sectional view (cross section of the width direction) of Fig.8 (a) typically. FIG. FIG. 9 is a cross-sectional view schematically showing another embodiment of the absorbent body according to the present invention.

  Hereinafter, the absorbent article of the present invention will be described based on a disposable diaper which is a preferred embodiment thereof with reference to the drawings. The diaper 1 of the present embodiment is a so-called unfolded disposable diaper, and includes an absorbent body 4 and a surface sheet 2 disposed on the skin facing surface side of the absorbent body 4, as shown in FIGS. The absorbent body 4 includes an absorbent core 40 containing an absorbent material, and a core wrap sheet 5A that covers at least the skin facing surface 40a of the absorbent core 40.

  The diaper 1 will be further described. The diaper 1 includes a liquid-permeable surface sheet 2 that forms a skin-facing surface, a liquid-impermeable or water-repellent material that forms a non-skin-facing surface (hereinafter collectively referred to as liquid-impermeable). And the absorber 4 disposed between the two sheets 2 and 3, and is formed substantially vertically long. Each of the top sheet 2, the back sheet 3, and the absorber 4 has a vertically long shape that is long in one direction X. Each of the top sheet 2 and the back sheet 3 has a size larger than that of the absorber 4, and extends outward from the peripheral edge of the absorber 4. As shown in FIG. 2, the width of the top sheet 2 in the width direction Y is smaller than the width of the back sheet 3 in the width direction Y.

  As shown in FIG. 1, the diaper 1 has, in the longitudinal direction X, a back side portion A disposed on the back side of the wearer at the time of wearing, and a ventral side portion B disposed on the abdomen side of the wearer at the time of wearing, And a crotch part C on which the wearer's crotch is arranged when worn. The crotch part C includes an excretion part facing part that is disposed so as to face the wearer's excretion part when worn, and is located at the central part in the longitudinal direction X of the diaper 1. The diaper 1 has an hourglass shape in which both side edges of the crotch part C are curved in an inward arc shape, and the center part in the longitudinal direction X is inwardly bounded in a plan view as shown in FIG. Yes.

  In this specification, a longitudinal direction (X direction in a figure) is a direction along the long side of an absorptive article (diaper 1) or its component (surface sheet 2, absorptive core 40, core wrap sheet 5A, etc.). Yes, the width direction (Y direction in the figure) is a direction orthogonal to the longitudinal direction. Further, the skin facing surface is a surface of the absorbent article or a component thereof that is directed to the wearer's skin when the absorbent article is worn, and the non-skin facing surface is an absorption in the absorbent article or a component thereof. It is a surface that is directed to the side opposite to the skin side (clothing side) when wearing the property article.

  As shown in FIGS. 1 and 2, the absorbent body 4 includes an absorbent core 40 and two core wrap sheets 5A and 5B that cover the absorbent core 40. The absorbent core 40 contains an absorbent material such as a hydrophilic fiber or a water-absorbing polymer, and has a long thin plate shape in one direction (longitudinal direction X of the diaper 1) as shown in FIG. Department is wrapped up.

  As shown in FIG.1 and FIG.2, the side sheet | seat 6 to which the elastic member 61 is being fixed in the expansion | extension state by one side edge part is distribute | arranged to each both sides along the longitudinal direction X of the diaper 1, and it wears A pair of three-dimensional gathers are formed in the crotch part C at the time. In addition, elastic members 62 are arranged along the longitudinal direction X on the left and right leg portions arranged around the legs of the wearer. Leg gathers are formed. The pair of side sheets 6 and 6, the top sheet 2, the absorbent body 4, the elastic members 61 and 62, and the back sheet 3 are appropriately joined to each other by a known joining means such as a hot-melt adhesive.

  Moreover, as shown in FIG. 1, a pair of fastening tapes 7 and 7 are provided in the both-sides edge part along the longitudinal direction X of the back side part A of the diaper 1. As shown in FIG. A fastening part 71 made of a male member of a mechanical surface fastener is attached to the fastening tape 7. In addition, a non-skin facing surface of the ventral side B of the diaper 1 is formed with an attachment region 8 made of a female member of a mechanical hook-and-loop fastener. The to-be-bonded region 8 is formed by joining and fixing a female member of a mechanical surface fastener to the non-skin facing surface of the back sheet 3 with a known joining means (for example, an adhesive or heat seal). The fastening part 71 of the tape 7 can be detachably fastened.

  When the core wrap sheet which comprises the absorber 4 with the absorptive core 40 is demonstrated, as shown in FIG. 2, the absorber 4 has the core wrap sheet 5A which coat | covers the skin opposing surface 40a of the absorptive core 40, and an absorptivity. It includes a non-skin facing surface 40b of the core 40 and a core wrap sheet 5B that covers both side edges 40s, 40s along the longitudinal direction X of the absorbent core 40. Both sheets 5A and 5B differ only in the dimension (length in the width direction Y), and have the same composition. The core wrap sheet 5 </ b> A covers substantially the entire area of the skin facing surface 40 a of the absorbent core 40. The core wrap sheet 5B covers substantially the entire area of the non-skin facing surface 40b of the absorbent core 40, and extends outward in the width direction Y from both side edge portions 40s, 40s of the absorbent core 40, and the extended portion thereof. Is wound up on the core wrap sheet 5A disposed to face the skin facing surface 40a of the absorbent core 40, and covers both side edges along the longitudinal direction X of the sheet 5A. The core wrap sheet 5A and the absorbent core 40 and the core wrap sheet 5B and the absorbent core 40 may be joined by a known joining means such as a hot-melt adhesive.

  As shown in FIG. 3, the core wrap sheet 5A disposed between the top sheet 2 and the absorbent core 40 and covering the skin-facing surface 40a of the absorbent core 40 is overlapped with the first layer 51. And two layers 52. The first layer 51 and the second layer 52 are integrated. The first layer 51 is disposed adjacent to the top sheet 2, and is located closer to the top sheet 2 than the second layer 52. Therefore, when body fluid such as urine is excreted toward the top sheet 2 when the diaper 1 is worn, the first layer 51 comes into contact with the body fluid (excretion fluid) first in the core wrap sheet 5A.

  As one of the main features of the diaper 1 of this embodiment, the skin side structural member (surface sheet 2, the 1st layer 51 of core wrap sheet | seat 5A) which contains the absorptive core 40 and is located in a wearer's skin side rather than this. And the second layer 52 and the absorbent core 40), the liquid permeation time T1 of the top sheet 2 measured by the following method, the liquid permeation time T2 of the first layer 51 of the core wrap sheet 5A, and the second of the core wrap sheet 5A. The point which the liquid permeation | transmission time T3 of the layer 52 and the liquid permeation | transmission time T4 of the absorptive core 40 have the relationship of T3> T4> T1> = T2 is mentioned. The liquid permeation time is an index of the liquid permeation speed. The shorter the liquid permeation time, the faster the liquid permeation speed is considered, and the liquid permeation time is highly evaluated as being excellent in liquid permeability. Therefore, in the diaper 1, the first layer 51 having the shortest liquid permeation time T2 has the fastest liquid permeation speed and the second layer 53 having the longest liquid permeation time T3 is the most liquid permeation speed. In the single core wrap sheet 5A, there are a portion having the fastest liquid permeation rate (first layer 51) and a portion having the slowest liquid permeation rate (second layer 52). The layers 51 and 52 are adjacent to each other in the thickness direction. Further, the liquid permeation time T1 of the top sheet 2 is equal to or longer than the liquid permeation time T2 of the first layer 51 and shorter than the liquid permeation time T4 of the absorbent core 40. Accordingly, the liquid permeation rate of the top sheet 2 is equal to or slower than the liquid permeation rate of the first layer 51, but is faster than the liquid permeation rate of the absorbent core 40.

<Measurement method of liquid permeation time>
As shown in FIG. 4, two cylinders 91 and 92 having an inner diameter of 35 mm with upper and lower ends opened are arranged up and down with the axes of both cylinders 91 and 92 aligned, and an 8 cm square measurement sample S is placed up and down. Between the cylinders 91 and 92. At this time, it is preferable that the upper and lower cylinders 91 and 92 are connected by fitting the clip 93 to an annular flange portion provided at the lower end of the upper cylinder 91 and the upper end of the lower cylinder 92. Reference numeral 94 denotes a rubber packing having a through hole having the same diameter and the same shape as the inner diameters of the cylinders 91 and 92. Thus, in the state where the measurement sample S is sandwiched and fixed between the upper and lower cylinders 91 and 92, a physiological saline (an aqueous solution having a sodium chloride concentration of 0.9 mass%) indicated by the symbol W in FIG. 40 g ± 1 g is supplied. The supplied physiological saline passes through the measurement sample S or is absorbed by the measurement sample S and disappears from the upper cylinder 91. The time from when the physiological saline starts to be supplied until the physiological water surface reaches the same position as the surface of the measurement sample S (the surface on the upper cylinder 91 side) is taken as the liquid permeation time.

  In addition, when measuring the liquid permeation time for each of the first layer and the second layer of the core wrap sheet alone, the first layer and the second layer are peeled off from the core wrap sheet and used as a measurement sample. When it is difficult to peel off, separately prepare sheets corresponding to the first layer and the second layer, and use the prepared sheets as measurement samples. The separately prepared sheet has the same composition as the first layer or the second layer in the core wrap sheet. In addition to the machine conditions (paper making conditions) such as paper making speed, press roll pressure, touch roll pressure, pulp slurry concentration, thickness and density Sheet characteristics such as moisture content and crepe rate should be the same as much as possible.

  The diaper 1 has a liquid permeation rate gradient satisfying T3> T4> T1 ≧ T2 in the skin side component (the surface sheet 2, the first layer 51 and the second layer 52 of the core wrap sheet 5A, and the absorbent core 40). By having, it has the characteristics that it is excellent in liquid permeability and liquid diffusibility, and the utilization efficiency of the absorber 4 is high. Among these skin-side structural members, the core having the first layer 51 with the fastest liquid permeation speed and the second layer 52 with the slowest speed plays a particularly important role in improving the utilization efficiency of the absorbent body 4. In the wrap sheet 5A, the difference in the liquid permeation speed between the first layer 51 and the second layer 52 promotes the diffusion of excretory fluid such as urine in the surface direction, thereby improving the utilization efficiency of the absorber 4. . That is, in the core wrap sheet 5A, due to the difference in liquid permeation speed between the first layer 51 and the second layer 52, urine or the like is present at or near the interface (the vicinity of the interface in the first layer 51). The excretory fluid is diffused in the surface direction, and the diffused fluid thus diffused is transmitted in the thickness direction toward the second layer 52 while being further diffused in the surface direction by the capillary phenomenon of the first layer 51. Although the second layer 52 itself has a low liquid permeation rate as compared with the first layer 51, it has good liquid permeability, so that the core wrap sheet 5A as a whole has excellent liquid permeability and liquid diffusibility. It can be expressed.

  As shown in FIG. 3, the core wrap sheet 5A having excellent liquid permeability and liquid diffusibility is formed between the surface sheet 2 having a relatively high liquid transmission rate and the absorbent core 40 having a relatively low liquid transmission rate. When excretion fluid such as urine is excreted from the body of the diaper wearer toward the surface sheet 2 of the excretory part facing portion of the crotch C, the excretion fluid is contained inside the surface sheet 2. The core wrap sheet 5A passes through the inside in the thickness direction, reaches the first layer 51 of the core wrap sheet 5A, and at the interface between the first layer 51 and the second layer 52 or in the vicinity of the interface in the first layer 51. And diffused in the surface direction. The excretory liquid diffused in the surface direction thus passes through the second layer 52 at a relatively slow speed in the thickness direction, reaches the skin facing surface 40a of the absorbent core 40, and is absorbed and held therein. Thus, according to the diaper 1, the core wrap sheet 5 </ b> A transmits the excretion liquid received from the top sheet 2 to the absorbent core 40 after further diffusing in the surface direction around the excretion part facing part. The excretory fluid can be sent to a wide area of the skin facing surface 40a of the absorbent core 40. Therefore, the excretory fluid can be absorbed and held in a wide area of the absorbent core 40, and the absorbent core 40 (absorber 4) can be used efficiently.

  From the viewpoint of more surely exhibiting the effect of the liquid permeation time gradient (T3> T4> T1 ≧ T2), the liquid permeation time T3 of the second layer 52 is preferably 4 to 10 seconds, The liquid permeation time T4 of the absorbent core 40 is preferably 3 to 8 seconds, more preferably 3 to 5 seconds, and the liquid permeation time T1 of the top sheet 2 is preferably 0. .1 to 3 seconds, more preferably 0.5 to 2 seconds, and the liquid permeation time T2 of the first layer 51 is preferably 0.1 to 3 seconds, and more preferably 0.5 to 2 seconds. The difference between T3 and T4 (T3-T4) is preferably 1 to 8 seconds, more preferably 1 to 3 seconds, and the difference between T4 and T1 (T4-T1) is preferably 0.5. -5 seconds, more preferably 1-4 seconds, and the difference between T1 and T2 (T1-T2) is preferably 0-2.5 seconds, more preferably 0-2 seconds.

  The diaper 1 may further include another member in addition to the topsheet 2, the core wrap sheet 5A (first layer 51, second layer 52), and the absorbent core 40 as the skin-side constituent member. . FIG. 5 shows an example in which a liquid permeable sheet 9 is disposed between the top sheet 2 and the absorber 4. The liquid permeable sheet 9 is a single sheet made of paper, non-woven fabric, etc., and is disposed on the crotch part C where at least the excretory part facing part exists, and further disposed on the back side part A and / or the abdominal side part B. May be. The liquid permeable sheet 9 is effective in reducing so-called liquid return in which the liquid absorbed by the absorber returns to the top sheet.

  As described above, when the diaper 1 includes the liquid permeable sheet 9, when the liquid permeation time of the liquid permeable sheet 9 is T5, the diaper 1 includes the absorbent core 40 and is more than this. The component located on the skin side of the wearer has a liquid permeation rate gradient satisfying T3> T4> T1 ≧ T5 ≧ T2, which improves the utilization efficiency of the absorbent body 4 (absorbent core 40). This is preferable. Even if the liquid permeable sheet 9 is disposed, the core wrap sheet 5A includes the first layer 51 having the fastest liquid permeation speed and the second layer 52 having the slowest liquid permeation speed. It is the same as if not.

  The liquid permeation time T5 of the liquid permeable sheet 9 is preferably 0.1 to 3 seconds, and more preferably 0.5 to 2 seconds. The difference between T1 and T5 (T1-T5) is preferably 0 to 2.5 seconds, more preferably 0 to 2 seconds, and the difference between T5 and T2 (T5-T2) is preferably 0. .5 to 2 seconds, more preferably 0 to 2 seconds. The other liquid permeation time is the same as when the liquid permeable sheet 9 is not provided.

  The most important thing for imparting the liquid permeation velocity gradient (T3> T4> T1 ≧ T2 or T3> T4> T1 ≧ T5 ≧ T2) to the diaper 1 is to select an appropriate core wrap sheet 5A. It is. Of the skin-side constituent members [surface sheet 2, liquid permeable sheet 9, core wrap sheet 5A (first layer 51, second layer 52) and absorbent core 40], other constituent members other than core wrap sheet 5A Even if what is conventionally used in the said technical field is used, if the suitable thing as the core wrap sheet | seat 5A is selected, it is possible to provide the diaper 1 with the liquid permeation speed gradient mentioned above. Hereinafter, the said skin side structural member preferably used by this invention is demonstrated in order from 5 A of core wrap sheets. As described above, the core wrap sheet 5B is different from the core wrap sheet 5A only in size, and the same core wrap sheet 5B as the core wrap sheet 5A can be used. In that case, the core wrap sheet 5B may be arranged so that the first layer 51 is located closer to the absorbent core 40 than the second layer 52, or may be arranged in the opposite manner.

[Core wrap sheet]
The core wrap sheet 5A has a two-layer structure including a first layer (first layer 51 in the diaper 1) that first contacts the liquid and a second layer (second layer 52 in the diaper 1) that overlaps the first layer. In the core wrap sheet, the first layer having a liquid permeability higher than that of the second layer is preferably used. As an example, the first layer may be bulky as compared with the second layer. In such a core wrap sheet, the first layer and the second layer are integrated. Examples of the first layer and the second layer include paper (for example, paper obtained by wet papermaking), nonwoven fabric, and the like, and these materials can be appropriately combined. In the core wrap sheet, both the first layer and the second layer may be paper, or both layers may be non-woven fabric, or the first layer may be paper and the second layer may be non-woven fabric, or The first layer may be a non-woven fabric and the second layer may be paper.

  Examples of paper forming the first layer or the second layer of the core wrap sheet include softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), and thermomechanical pulp (TMP). ), And other papers containing general purpose pulp fibers such as non-wood pulp such as straw, bamboo, kenaf, hemp, etc. Containing rayon paper; mercerized pulp paper containing mercerized pulp that has been subjected to alkali treatment of cellulose fibers, etc., and increased in fiber cross section; synthetic fibers such as polyvinyl alcohol fibers, polyacrylonitrile fibers, polyethylene fibers, polypropylene fibers, and polyester fibers Synthetic fiber paper containing; regenerated cellulose fibers such as acetate, lyocell, tencel, cupra Regenerated cellulose fiber paper or the like comprising the like. Each of these special papers may contain other fibers in addition to specific fibers such as rayon, mercerized pulp, synthetic fibers, and regenerated cellulose fibers. Examples of the other fibers include the general-purpose pulp fibers. Can be mentioned. The content of other fibers is preferably 80% by mass or less, more preferably 5 to 50% by mass in the special paper.

  Moreover, as a nonwoven fabric which forms the 1st layer or 2nd layer of a core wrap sheet | seat, a spun bond nonwoven fabric, an air through nonwoven fabric, a spun bond-melt blown nonwoven fabric, an airlaid nonwoven fabric, a spunlace nonwoven fabric, a needle punch nonwoven fabric etc. are mentioned, for example. These nonwoven fabrics may be subjected to a hydrophilic treatment using a hydrophilic agent such as a surfactant.

  In the core wrap sheet having a two-layer structure composed of the first layer and the second layer, when one of the first layer and the second layer is paper and the other is a nonwoven fabric, examples of the paper include rayon and bulky cellulose fibers ( For example, a paper obtained by blending bulky fibers such as chemically-crosslinked cellulose fibers known as HBA), mercerized pulp, and the like can be used. Examples of the nonwoven fabric include spunbond nonwoven fabric and spunbond fabric. Meltblown-spunbond (SMS) nonwoven fabric, spunbond-meltblown-meltblown-spunbond (SMMS) nonwoven fabric, air-through nonwoven fabric, spunlace nonwoven fabric, and the like can be used. However, papers and non-woven fabrics other than those described above can also be used in the present invention. When the core wrap sheet is composed of a combination of paper and nonwoven fabric, the first layer (the first layer in the diaper 1) is the first layer that comes into contact with the liquid first, which is relatively liquid permeable (relatively bulky). 51) is preferable.

  When the core-wrap sheet having a two-layer structure including the first layer and the second layer is formed only from paper, the first paper that comes into contact with the liquid first is a paper having a relatively high liquid permeability (a relatively bulky paper). The layer is the first layer 51 in the diaper 1. The same composition of the first layer paper and the second layer paper can also be used for the core wrap sheet. In that case, the basis weight, the crepe rate, the degree of fibrillation of the constituent fibers (freeness value) The above-mentioned liquid permeation time difference (liquid permeation speed difference) between the first layer paper and the second layer paper due to the presence or absence of post-processing such as embossing (processing performed after paper making) Can be granted.

  When the core-wrap sheet having a two-layer structure composed of the first layer and the second layer is composed of only a nonwoven fabric, the relatively bulky nonwoven fabric is first contacted with the liquid first layer (first layer 51 in the diaper 1). And A non-woven fabric for the first layer and a non-woven fabric for the second layer that have the same composition can also be used for the core wrap sheet. In that case, post-processing such as basis weight, hydrophilizing agent, embossing (production of the non-woven fabric) Depending on the presence or absence of the subsequent processing), the liquid permeation time difference (liquid permeation speed difference) described above can be imparted to the non-woven fabric for the first layer and the non-woven fabric for the second layer.

  As an example of what is preferably used as the core wrap sheet 5A, a hydrophilic bulky fiber and a pulp fiber having a fiber roughness of 0.30 mg / m or more in the first layer (first layer 51 in the diaper 1) that the liquid first contacts with And a second layer (the second layer 52 in the diaper 1) that overlaps the first layer contains a specific pulp fiber having a fiber roughness of 0.10 to 0.20 mg / m (hereinafter referred to as a specific paper) Also referred to as absorbent paper). In this specific absorbent paper, the first layer is bulky and has higher liquid permeability than the second layer, and both layers are made of paper. Hereinafter, the specific absorbent paper will be described.

  One of the main features of the specific absorbent paper is that it contains two types of fibers with different fiber roughness, of which fibers with relatively high fiber roughness (hydrophilic bulky fibers with a fiber roughness of 0.30 mg / m or more) ) In the first layer in contact with the liquid, and fibers having a relatively low fiber roughness (specific pulp fibers having a fiber roughness of 0.10 to 0.20 mg / m) are layered on the first layer. The point contained in the 2nd layer to do is mentioned. Fiber roughness is used as a measure of fiber thickness in fibers with uneven fiber thickness, such as wood pulp, and is measured using a commercially available fiber roughness meter as described later. Is done. That is, the specific absorbent paper contains two types of fibers having different thicknesses, and includes thick fibers (bulky fibers) in the first layer and thin fibers in the second layer. Therefore, the first layer is bulky compared to the second layer. In general, a bulky fiber layer has a large number of fibers in a relatively sparse state and has a relatively large number of inter-fiber gaps. Therefore, the bulky fiber layer is not bulky and a large number of fibers are relatively dense. The liquid permeation speed is faster than the fiber layer present in the state. Therefore, in the specific absorbent paper, the relatively bulky first layer has a higher liquid permeation speed than the second layer, and there is a difference in the liquid permeation speed between the first layer and the second layer. The difference in liquid permeation speed causes liquid diffusion at or near the interface between the first layer and the second layer. Moreover, since the thick fiber (bulky fiber) with a fiber roughness of 0.30 mg / m or more contained in the first layer is a hydrophilic bulky fiber, in the specific absorbent paper, the first layer and the second layer In addition to liquid diffusion due to the difference in liquid permeation rate, liquid diffusion due to capillary action of hydrophilic bulky fibers is also manifested, and excellent liquid diffusibility is manifested by these liquid diffusion actions.

  As described above, the fiber roughness of the hydrophilic bulky fibers contained in the first layer of the specific absorbent paper is 0.30 mg / m or more, preferably 0.30 to 0.40 mg / m, and more preferably 0. .32-0.38 mg / m. When the fiber roughness of the hydrophilic bulky fiber is less than 0.30 mg / m, the bulkiness of the first layer is insufficient, and the liquid transmission speed difference between the first layer and the second layer described above becomes small, and the specific absorbent paper There is a risk that the liquid diffusibility of the liquid becomes insufficient. The fiber roughness and average fiber length are each measured as follows.

<Measurement of fiber roughness and average fiber length>
It is measured using a fiber roughness meter FS-200 (manufactured by KAJAANI ELECTRONICS LTD.). The fiber to be measured shall be unbeaten. First, in order to obtain the true weight of the fiber to be measured, the fiber is dried in a vacuum dryer at 100 ° C. for 1 hour to remove moisture present in the fiber. 1 g is accurately weighed from the fibers thus dried (error ± 0.1 mg). Next, while taking care not to damage the fibers as much as possible, the weighed fibers are completely disaggregated in 150 ml of water with the mixer attached to the fiber roughness meter, and this is until the total amount reaches 5000 ml. Diluted with water to obtain a diluted solution. 50 ml is accurately weighed from the diluted solution thus obtained to make a fiber roughness measurement solution, and the target fiber roughness and average fiber length are calculated according to the operation procedure of the fiber roughness meter. In addition, the value calculated by the following formula based on the said operation procedure is used for calculation of average fiber length.

  An example of a hydrophilic bulky fiber contained in the first layer of the specific absorbent paper is a bulky cellulose fiber. The bulky cellulose fiber is a cellulose fiber having a three-dimensional structure such as a twisted structure, a crimped structure, a bent and / or branched structure, and the fiber itself is bulky due to the three-dimensional structure. Bulky cellulose fibers (hydrophilic bulky fibers) include, for example, crosslinked cellulose fibers in which cellulose fibers are cross-linked with and / or between molecules with a cross-linking agent (for example, chemically cross-linked cellulose known as HBA) Fiber); such as mercerized pulp (for example, trade name “Porocenia”) in which cellulose fiber and the like are subjected to alkali treatment to increase the cross section of the fiber, and one of these is used alone or in combination of two or more. be able to. Among these, the crosslinked cellulose fiber is particularly preferably used in the present invention because it can maintain its bulkiness (three-dimensional structure) even in a wet state. The crosslinked cellulose fiber is preferably crosslinked both inside and between the molecules of the cellulose fiber. Examples of the cellulose fiber that is a material for the bulky cellulose fiber (hydrophilic bulky fiber) include regenerated cellulose fibers such as rayon, cupra, tencel, and lyocell, and semisynthetic cellulose fibers such as acetate.

  Examples of the cellulose fiber crosslinking agent used in the production process of bulky cellulose fibers include N-methylol compounds such as dimethylolethyleneurea and dimethyloldihydroxyethyleneurea; citric acid, tricarballylic acid, butanetetracarboxylic acid Examples thereof include polycarboxylic acids such as polyglycidyl ether compounds, and these can be used alone or in combination of two or more.

  It is preferable that the usage-amount of a crosslinking agent shall be 0.2-20 mass parts with respect to 100 mass parts of cellulose fibers. If it is less than 0.2 parts by mass, the bulk density of the bulky cellulose fibers is low because the crosslinking density is low, and there is a risk of twisting / sagging. If it becomes too rigid and stress is applied, the fiber may become brittle. Examples of the method for crosslinking cellulose fibers using a crosslinking agent include the following methods i) and ii). i) Cellulose fibers are impregnated with an aqueous solution of a crosslinking agent, if necessary, and a cellulose fiber is impregnated. The cellulose fibers are dehydrated so that the amount of the crosslinking agent aqueous solution reaches a designed adhesion amount, and then heated to a crosslinking temperature. Method. ii) A method in which an aqueous solution of a crosslinking agent is sprayed on cellulose fibers so as to have a design adhesion amount by spraying, and then the cellulose fibers are heated to a crosslinking temperature to cause a crosslinking reaction.

  The first layer of the specific absorbent paper contains pulp fibers in addition to the hydrophilic bulky fibers. The reason why pulp fibers are contained in the first layer is to suppress a decrease in strength characteristics that are a concern due to the use of hydrophilic bulky fibers. In particular, when the content ratio of the hydrophilic bulky fibers is set to be larger than that of the pulp fibers in the first layer, the small bulk made between the pulp fibers in the high voids created between the hydrophilic bulky fibers occupying the majority. A structure in which the air gap is slightly mixed in the first layer is obtained, whereby the capillary force can be enhanced while maintaining the permeability.

  As the pulp fiber contained in the first layer of the specific absorbent paper, a known pulp fiber can be used without any particular limitation. For example, softwood bleached kraft pulp (NBKP), hardwood bleached kraft pulp (LBKP), softwood bleached monkey Wood pulp such as phytopulp (NBSP), thermomechanical pulp (TMP), etc .; bast fibers such as straw, cocoon, scabbard, etc .; non-wood pulp such as straw, bamboo, kenaf, hemp, etc. Or two or more types can be used in combination. Among these pulp fibers, NBKP is particularly preferably used in the present invention because the strength of paper produced using this is high. As NBKP used in the present invention, NBKP usually used in this type of paper can be used without any particular limitation. As NBKP, ECF (elementary chlorin-free) bleached pulp or TCF (total chlorin-free) bleached pulp that does not use a chlorine compound for pulp bleaching may be used.

  The mass ratio of hydrophilic bulky fibers and pulp fibers (hydrophilic bulky fibers / pulp fibers) in the first layer of the specific absorbent paper is preferably 4/6 to from the viewpoint of the balance between liquid diffusibility and strength characteristics. 9/1, more preferably 5/5 to 8/2. If there are too few hydrophilic bulky fibers with a fiber roughness of 0.30 mg / m or more, the bulkiness of the first layer will be insufficient, and the difference in liquid permeation rate between the first layer and the second layer will be reduced. There is a possibility that the diffusibility may be insufficient, and conversely, if there are too many hydrophilic bulky fibers, the strength of the first layer may be drastically reduced.

  In the first layer of the specific absorbent paper, in addition to the above-described hydrophilic bulky fibers and pulp fibers having a fiber roughness of 0.30 mg / m or more, heat-adhesive adhesive fibers can be further contained as fibers. . The heat-fusible adhesive fiber is a fiber that melts and adheres to each other by heating. By including this fiber in the first layer, the bulky structure of the first layer is more stably maintained. The content of the heat-fusible adhesive fiber is preferably 10% by mass or less, more preferably 8% by mass or less, based on the dry mass of all the fibers in the first layer.

  Examples of the heat-fusible adhesive fibers include polyolefin fibers such as polyethylene, polypropylene, polyvinyl alcohol, polyacrylic acid and salts thereof, polyester fibers, polyethylene-polypropylene composite fibers, polyethylene-polyester composite fibers, and low melting point polyesters. Examples thereof include a polyester composite fiber, a polyvinyl alcohol-polypropylene composite fiber having a hydrophilic fiber surface, and a polyvinyl alcohol-polyester composite fiber. When using a composite fiber, any of a core-sheath type composite fiber and a side-by-side type composite fiber can be used. These heat-fusible adhesive fibers can be used alone or in combination of two or more. Examples of the hot-melt adhesive fiber preferably used in the present invention include polyvinyl alcohol and polyester.

  The first layer of the specific absorbent paper may further contain a dry paper strength enhancer in addition to the various fibers described above. As the dry paper strength enhancer contained in the first layer, conventionally known ones can be used without particular limitation. For example, carboxymethyl cellulose (CMC) and its salt, polyacrylamide resin and its salt, cationized starch , Polyvinyl alcohol (PVA), etc., and one of these can be used alone or two or more can be used in combination. As the salt of CMC or polyacrylamide resin, sodium salt is mainly used. Examples of the polyacrylamide resin include cationic or anionic polyacrylamide (PAM). Among these dry paper strength enhancers, CMC and salts thereof, anionic PAM and salts thereof, and PVA are particularly preferable.

  As will be described later, when the first layer of the specific absorbent paper is produced by the wet papermaking method, a method for adding a paper strength enhancer to the first layer is to make the paper before making the fiber web from the paper. A paper strength enhancer is added to the material by a so-called internal addition method, and a fiber strength obtained by drawing fibers from the paper material is applied to the fiber web by various application methods such as coating, impregnation, spraying, There is a so-called external addition method, and any addition method can be used in the present invention, but the first layer is likely to generate paper dust and fluff due to containing hydrophilic bulky fibers, In addition, since the yield of the paper strength enhancer may decrease in the internal addition method, the first layer is preferably provided with a paper strength enhancer (dry paper strength enhancer) by the external addition method. .

  The content of the dry paper strength enhancer is preferably 0.1 to 5% by mass, more preferably 0.2 to 2% by mass, based on the dry mass of all fibers in the first layer of the specific absorbent paper. . If the content of the dry paper strength enhancer is too low, the significance of using the dry paper strength enhancer (prevention of paper dust and fluff, improvement of strength properties such as dry tensile strength) will be weakened, and the dry paper strength enhancer will be contained. If the rate is too high, the specific absorbent paper will harden (decrease in texture), the paper will stick to the Yankee dryer during manufacture of the specific absorbent paper, and the paper strength enhancer will adhere to the mesh drum. There is a risk of lowering the formation.

  The first layer of the specific absorbent paper may contain components other than the above-described fibers (hydrophilic bulky fibers having a fiber roughness of 0.30 mg / m or more, pulp fibers, etc.) and a dry paper strength enhancer. . Other components include, for example, wet paper strength enhancers such as epoxidized polyamide polyamine resin (PAE), fillers such as talc, dyes, color pigments, antibacterial agents, pH adjusters, yield improvers, water resistance agents, water proofing agents. Those generally used as papermaking raw materials and additives such as foaming agents are mentioned, and one of these can be used alone or in combination of two or more.

  The second layer of the specific absorbent paper contains specific pulp fibers having a fiber roughness of 0.10 to 0.20 mg / m. As described above, what is particularly important with respect to the characteristics of the second layer is that the liquid permeation rate is slower than that of the first layer. From this viewpoint, in the present invention, the fibers constituting the second layer of the specific absorbent paper As a special pulp fiber having a lower fiber roughness than the constituent fibers (hydrophilic bulky fibers) of the first layer of the specific absorbent paper, the second layer is devised so as not to be bulkier than the first layer. doing. The fiber roughness of the specific pulp fiber contained in the second layer is preferably 0.12 to 0.20 mg / m, more preferably 0.15 to 0.20 mg / m. Moreover, the average fiber length of the specific pulp fiber contained in the second layer is preferably 1 to 3 mm, more preferably 2 to 2.8 mm, from the viewpoint of the formation of the specific absorbent paper.

  As the specific pulp fiber contained in the second layer of the specific absorbent paper, a pulp fiber having a fiber roughness in the above range can be used, and a known pulp fiber can be used without any particular limitation as the pulp fiber. For example, the same fiber as the pulp fiber (such as NBKP) contained in the first layer can be used. Therefore, in the present invention, the specific pulp fiber contained in the second layer and the pulp fiber contained in the first layer may be the same. A hydrophilic bulky fiber having a fiber roughness of 0.30 mg / m or more contained in the first layer is usually produced by subjecting the cellulose fiber to a specific treatment (treatment with a crosslinking agent, alkali treatment, etc.). The specific pulp fiber having a fiber roughness of 0.10 to 0.20 mg / m contained in the second layer usually does not require such specific treatment. Accordingly, NBKP or the like having a fiber roughness in the range of 0.10 to 0.20 mg / m can be used as the specific pulp fiber of the second layer as it is.

  In addition to the specific pulp fiber having a fiber roughness of 0.10 to 0.20 mg / m, the second layer of the specific absorbent paper further contains other fibers having a fiber roughness outside the above range. You can also. However, from the viewpoint of more reliably causing the liquid permeation rate difference with the first layer described above, thereby obtaining excellent liquid permeability and liquid diffusibility as the entire specific absorbent paper, other fibers other than the specific pulp fiber The content is preferably 30% by mass or less in the second layer, and more preferably 0% by mass, that is, only the specific pulp fiber is used as the fiber in the second layer of the specific absorbent paper. The content of the specific pulp fiber is preferably 70 to 100% by mass, more preferably 80 to 100% by mass in the second layer.

  The freeness of the fiber contained in the second layer of the specific absorbent paper (when the fiber contained in the second layer is only the specific pulp fiber, the freeness of the specific pulp fiber) is preferably 450 to 700 ml, Preferably it is 480-680 ml, Most preferably, it is 480-650 ml. Freeness is a value indicated by Canadian Standard Freeness (CSF) stipulated in JIS P8121, and is a value of beating of fibers (treatment of mechanically tapping and grinding fibers in the presence of water). It is a value indicating the degree. The beating of the fibers can be carried out according to a conventional method using a known beating machine such as a beader or a disc refiner with respect to the stock (slurry) in which the fibers are dispersed. Usually, the smaller the value of the freeness of the fiber, the stronger the degree of beating, the greater the damage of the fiber due to beating, and the more fibrillation proceeds. The fiber having the freeness in the above range (the specific pulp fiber) is easily entangled with each other because the fibrillation is in progress, and therefore, when the specific absorbent paper (second layer) is designed to have a low basis weight, Even if the number of interfiber bonding points is reduced, the strength of each interfiber bond is higher than that of fibers in which the freeness exceeds 700 ml and the fibrillation has not progressed relatively. On the other hand, when the freeness is less than 450 ml, the effect of improving the strength due to the entanglement of the fibers is saturated, and the cutting of the fibers is promoted, and the permeation time may be delayed. Therefore, the second layer of the specific absorbent paper containing fibers (specific pulp fibers) having a freeness of 450 to 700 ml can have good strength characteristics (tensile strength) and liquid permeability.

  The second layer of the specific absorbent paper may further contain a wet paper strength enhancer in addition to the specific pulp fiber. As the wet paper strength enhancer contained in the second layer, conventionally known ones can be used without particular limitation. For example, epoxidized polyamide polyamine resin (PAE), urea-formalin resin, melamine-formalin resin, Aldehyde starch, polyethyleneamine, methylolated polyamide and the like can be mentioned, and one of these can be used alone or in combination of two or more. Among these wet paper strength enhancers, PAE is particularly preferably used in the present invention because the wet paper strength of paper produced using it is high.

  The content of the wet paper strength enhancer is preferably 0.2 to 2% by mass, more preferably 0.5 to 1% by mass, based on the dry mass of all fibers in the second layer of the specific absorbent paper. . If the content of the wet paper strength enhancer is too small, the significance of using the wet paper strength enhancer (improvement of strength properties such as wet tensile strength) will fade, and if the content of wet paper strength enhancer is too high, it will be specified In addition to hardening of the absorbent paper (decrease in texture), it causes a decrease in the texture of the specific absorbent paper due to sticking of the paper to the Yankee dryer and adhesion of the paper strength enhancer to the mesh drum during the production of the specific absorbent paper There is a fear.

  The second layer of the specific absorbent paper may contain other components other than the specific pulp fiber having a fiber roughness of 0.10 to 0.20 mg / m and the wet paper strength enhancer. Other components include, for example, dry paper strength enhancers such as CMC, fillers such as talc, dyes, color pigments, antibacterial agents, pH adjusters, yield improvers, water resistance agents, antifoaming agents, etc. What is used as a papermaking raw material and an additive is mentioned, These 1 type can be used individually or in combination of 2 or more types.

  The first layer constituting the specific absorbent paper and the second layer superposed thereon can be respectively produced by a known wet papermaking method. The wet papermaking method has a stock preparation process for preparing a stock (slurry) made of an aqueous dispersion of fibers, and a paper making process for making a fiber web by drawing fibers from the stock and drying them. It is. The paper making process is usually divided into a wire part, a press part, a dryer part, a size press, a calendar part, etc., and is carried out sequentially. The wet papermaking method can be carried out according to a conventional method using a paper machine such as a long paper machine, a twin wire paper machine, an on-top paper machine, a hybrid paper machine, or a round paper machine.

  In the specific absorbent paper, the first layer and the second layer are integrated. The method for integrating the first layer and the second layer is not particularly limited as long as both can be integrated. For example, the first layer and the second layer in a dry state separately produced by a wet papermaking method are used. Is used to obtain a laminated body, and press the laminated body through a pair of embossing rolls to integrate the two, or a method of integrating the two by a bonding means such as an adhesive or an adhesive. be able to. In the former method, the laminate may be pressed from the first layer side to the second layer side, or may be pressed in the opposite direction. In the specific absorbent paper obtained by the former method, a concave portion is usually formed in which the first layer and the second layer are integrally recessed.

  In the present invention, as a method for integrating the first layer and the second layer, the wet fiber webs of the first layer and the second layer obtained in the wet papermaking process are continuously integrated in the wet papermaking process. The method of making it preferable is. When both layers are integrated by such a method, the fibers of both layers are intertwined more closely, and the liquid moves smoothly between the two layers. Specific examples of the method for integrating the first layer and the second layer in the wet papermaking process include the following methods. That is, the slurry for forming the first layer is supplied to a paper machine to form a paper layer (fiber web) on the wire. Separately from this, the slurry for forming the second layer is supplied to another paper machine to form a paper layer (fiber web) on the wire. These paper layers (fiber webs) are picked up from the respective wires, and are superposed on each other in a wet state, followed by squeezing, dehydrating, and drying, whereby the specific absorbent paper in which the first layer and the second layer are integrated. Is obtained.

  Moreover, the following method is mentioned as another specific example of the method of integrating a 1st layer and a 2nd layer in a wet papermaking process. That is, the slurry for forming the first layer and the slurry for forming the second layer are respectively supplied onto the wires at once from two rows of papermaking nozzles to form a paper layer (fiber web) having a two-layer structure. Next, the paper layer (fiber web) is taken up from the wire, pressed and dehydrated, and dried to obtain a specific absorbent paper in which the first layer and the second layer are integrated.

The specific absorbent paper preferably has a relatively low basis weight from the viewpoint of being suitable for a core wrap sheet of a thin absorbent body. Specifically, the total of the first layer and the second layer It is preferable that the basis weight is 10 to 30 g / m ² , particularly 12 to 25 g / m ² , particularly 15 to 20 g / m ² . If the basis weight is so low, the paper strength may be lowered. However, by adopting the configuration of the specific absorbent paper described above (particularly, the configuration of the second layer), such a concern can be eliminated. If the basis weight of the specific absorbent paper is less than 10 g / m ² , the paper strength may be remarkably reduced, and if the basis weight of the specific absorbent paper exceeds 30 g / m ² , the specific absorbent paper may be hardened. The basis weight of the first layer is preferably 10-22 g / m ² , more preferably 10-18 g / m ² , and the basis weight of the second layer is preferably 8-15 g / m ² , more preferably 8 ˜12 g / m ² .

The basis weight of the specific absorbent paper (first layer, second layer) is measured as follows. After conditioning the sample (specified absorbent paper or first layer or second layer) under the conditions of JIS P8111, a 10 cm square (100 cm ² ) measurement piece was cut out from the sample, and the weight of the measurement piece was small. Measurement is made with a two-digit balance below the point, and the measured value is divided by the area to calculate the basis weight of the measurement piece. About 10 measurement pieces cut out from the sample, the basis weight is calculated according to the above procedure, and the average value thereof is taken as the basis weight of the sample. When the specific absorbent paper is configured by integrating the first layer and the second layer in a stacked state, the first layer is peeled off from the specific absorbent paper, and the remaining second layer is removed according to the above procedure. The first layer was measured by measuring the basis weight (basis weight of the second layer alone) and subtracting the basis weight of the second absorbent layer from the basis weight of the specific absorbent paper separately measured according to the above procedure. Single basis weight is calculated.

  The specific absorbent paper preferably has crepes (crepe-like wrinkles). The absorbent paper having a crepe has higher liquid permeability than the absorbent paper not having a crepe, and the liquid permeability increases as the crepe rate increases. However, as the crepe rate increases, the strength properties (tensile strength) tend to decrease. Based on such knowledge, the crepe rate of the specific absorbent paper is preferably 5 to 20%, particularly 8 to 18%, particularly 10 to 15% from the viewpoint of the balance between liquid permeability and strength characteristics. Further, the crepe in the specific absorbent paper is preferably a dry crepe that is generated when a dry fiber web is peeled off from a Yankee dryer or the like in the dryer part with a doctor knife or the like. The crepe rate is measured as follows.

<Measurement method of crepe rate>
A rectangular shape having a length of 200 mm in the length direction (conveying direction when manufacturing the measurement target sheet, MD) and a width of 100 mm in the width direction (direction orthogonal to MD, CD) is cut out from the measurement target sheet (specific absorbent paper). . The length C of the MD immediately after the rectangular sample is immersed in water for 10 minutes is measured, and the crepe rate is calculated by the following equation. Crepe rate (%) = {(C−200) / 200} × 100 For example, when MD length C after immersion for 10 minutes is 220 mm, the crepe rate of the sheet calculated by the above formula is 10%. It is.

  Further, the water absorption amount of the specific absorbent paper is preferably 0.2 g / 30 sec · 15 mm or more, more preferably 0.2 to 0.4 g / 30 sec · 15 mm. The fact that the water absorption amount of the specific absorbent paper is in such a range is largely due to the formation of a highly voided structure in the interior, and the formation of the highly voided structure is particularly high in the hydrophilic bulkiness of the first layer. This is largely due to the use of fibers. The specific absorbent paper having the Krem water absorption in such a range has a practically sufficient liquid permeability and liquid diffusibility, and is suitable as a core wrap sheet. The Krem water absorption is measured as follows in accordance with the water absorption test method by the paper Krem method defined in JIS P8141.

<Measurement method of Krem water absorption>
The sheet to be measured (specific absorbent paper) is allowed to stand for 12 hours in an environment of a room temperature of 23 ° C. ± 2 ° C. and a relative humidity of 50% RH ± 2% so as to be in a constant state. A rectangular shape having a size of 150 mm for MD and 15 mm for CD is cut out from the moisture-conditioned sheet, and the cut out rectangular shape is used as a sample. A straight line (marked line) parallel to the short side is drawn with a pencil at a position 5 mm inward in the longitudinal direction from one short side of the sample. Then, the sample is suspended at the bottom of the electronic balance so that the long side of the sample is vertical, and the sample is quickly put into the measuring solution (saline) while maintaining the suspended state up to the marked line. . The sample is hung so that the marked line (straight line drawn with a pencil) is close to the measurement solution. Then, an increase in the weight of the sample 30 seconds after the sample is put in the measurement solution is measured with an electronic balance, and the measured value is defined as a Krem water absorption (g / 30 sec. 15 mm). The higher the Krem water absorption, the higher the rating. The electronic balance is electrically connected to a personal computer on which a commercially available electronic balance data capturing software (trade name RsCom Ver2.40: manufactured by A & D Co., Ltd.) is installed. The change in weight of the sample can be recorded.

  Further, the dry tensile strength in the transport direction (Machine Direction, abbreviated as MD) at the time of manufacturing the specific absorbent paper is preferably 600 cN / 25 mm or more, more preferably 650 to 1500 cN / 25 mm. The wet tensile strength in the direction perpendicular to the cross section (Cross machine Direction, abbreviated as CD) is preferably 50 cN / 25 mm or more, more preferably 60 to 120 cN / 25 mm. The specific absorbent paper whose dry tensile strength and wet tensile strength are in such ranges respectively has a practically sufficient strength and is suitable as a core wrap sheet. In particular, the fact that the dry tensile strength of the MD of the specific absorbent paper is within the above range mainly contributes to the prevention of inconvenience that the specific absorbent paper is torn due to a sudden tension change in the conveyance tension or paper splicing during the manufacture of the specific absorbent paper. In addition, the wet tensile strength of the CD of the specific absorbent paper is in the above range mainly when the specific absorbent paper is used as a core wrap sheet in the absorbent article. This contributes to the prevention of inconvenience that the core wrap sheet is torn by movement, friction, etc. after excretion of body fluid and the absorbent core forming material (wood pulp, super absorbent resin, etc.) comes out on the top sheet. The fact that the dry tensile strength of the MD and the wet tensile strength of the CD of the specific absorbent paper are in the above ranges are largely due to the presence of the second layer, and the excellent tensile strength characteristics of the second layer are as follows. This is largely due to the fact that the freeness of the fibers (specific pulp fibers) is in the specific range and that the wet strength of the second layer is contained in the second layer. The dry tensile strength and the wet tensile strength are measured as follows.

<Measurement method of dry tensile strength>
The sheet to be measured (specific absorbent paper) is allowed to stand for 12 hours in an environment of a room temperature of 23 ° C. ± 2 ° C. and a relative humidity of 50% RH ± 2% so as to be in a constant state. A rectangular shape with dimensions of 150 mm for MD and 25 mm for CD is cut out from the humidity-adjusted sheet, and the cut out rectangular shape is used as a sample. This sample is attached to a chuck of a tensile testing machine (manufactured by Shimadzu Autograph AG-1kN) without tension so that the MD is in the tensile direction. The distance between chucks is 100 mm. The sample is pulled at a pulling speed of 300 mm / min, and the maximum strength until the sample breaks is measured. The measurement is performed 5 times, and the average of these values is taken as the MD dry tensile strength.

<Measurement method of wet tensile strength>
A sample of a sheet to be measured (thin paper) is prepared in the same procedure as in the above <Method for measuring dry tensile strength>. This sample is attached to a chuck of a tensile tester (Shimadzu Autograph AG-1kN) without tension so that the CD is in the tensile direction, and the tip of the brush is wetted with water. After the sample is wetted by applying water at a width of about 10 mm over the entire length in the tensile direction, the sample is pulled at a tensile rate of 300 mm / min, and the maximum strength until the sample breaks is measured. The measurement is performed 5 times, and the average of these values is taken as the wet tensile strength of CD.

<Measurement method of wet tensile strength>
A sample of the measurement target sheet (specific absorbent paper) is prepared in the same procedure as in the above <Dry tensile strength measurement method>. This sample is attached to a chuck of a tensile tester (manufactured by Shimadzu Autograph AG-1kN) with no tension so that its MD is in the tensile direction, and the tip of the brush is wetted with water. After the sample is wetted by applying water at a width of about 10 mm over the entire length in the tensile direction, the sample is pulled at a tensile rate of 300 mm / min, and the maximum strength until the sample breaks is measured. The measurement is performed 5 times, and the average value of these is taken as the wet tensile strength of MD.

[Surface sheet]
As the surface sheet 2, a liquid-permeable sheet conventionally used in the technical field can be used. For example, a nonwoven fabric, an air-through nonwoven fabric, a spunbond nonwoven fabric, a meltblown nonwoven fabric, a spunlace nonwoven fabric, and the like manufactured by the card method Various nonwoven fabrics such as needle punched nonwoven fabrics; films that can be permeated by opening means, and the like. These nonwoven fabrics and films may be subjected to a hydrophilic treatment using a hydrophilic agent such as a surfactant. The basis weight of the surface sheet 2, cost, production, from the viewpoint of absorption performance, preferably 10 to 50 g / m ^2, more preferably a 15 to 30 g / m ^2.

  As the surface sheet according to the present invention, instead of the flat surface sheet 2 (flat surface sheet) having substantially no unevenness, the surface sheet 2A (unevenness) having the uneven shape shown in FIGS. A mold surface sheet) can also be used. As shown in FIGS. 6 and 7, the topsheet 2 </ b> A has a large number of convex portions 21 that protrude toward the wearer's skin and a number of concave portions 22 that are adjacent to the convex portions 21. The convex portions 21 and the concave portions 22 are arranged on the skin facing surface 2a of the topsheet 2A that forms the skin facing surface of the diaper 1 so as to be alternately arranged in one direction. Such an uneven shape of the skin facing surface 2a of the topsheet 2A by the convex portion 21 and the concave portion 22 is an arrangement region of the absorbent body 4 (at least in the crotch part C (the excretory portion facing portion)) of the diaper 1 as shown in FIG. In a plan view, it is formed in a region overlapping with the absorber 4. The central portion of the diaper 1 in the width direction Y. In this embodiment, the region where the absorber 4 is disposed in each of the back side portion A and the ventral side portion B. Also formed.

  The top sheet 2A is made of a nonwoven fabric having a single layer structure. 2 A of surface sheets protrude toward the wearer's skin side in parts other than the recessed part 22, and form the convex part 21. FIG. A space 25 in which the material for forming the topsheet 2A does not substantially exist is formed in the convex portion 21. The concave portion 22 is substantially flat and has no unevenness, and is in contact with the skin facing surface of the absorbent body 4 (core wrap sheet 5A). The surface sheet 2A having a concavo-convex structure formed by the convex portions 21 and the concave portions 22 can be formed by using a known embossing process. For example, a surface sheet original fabric (a flat sheet having no concavo-convex surface) is formed on the peripheral surface. The surface of the first roll having a concavo-convex shape and the second roll having a concavo-convex shape meshing with the concavo-convex shape of the first roll on the peripheral surface, It is obtained by unevenly shaping the original sheet.

  In the diaper 1, when the surface sheet 2 </ b> A is used instead of the surface sheet 2, a space 25 is formed in which the convex portion 21 faces the skin side and the material for forming the surface sheet 2 </ b> A is not substantially present. As a result, the permeability of the surface sheet 2A is improved, and the surface area (skin facing surface) has a relatively low adhesion area to the skin compared to a flat surface sheet having no irregularities on the surface. The adhering amount of the excretory fluid on the skin is reduced, and the effect of improving the dry feeling on the surface (skin facing surface) is exhibited.

From the viewpoint of ensuring the above-described effects by the top sheet 2A, the dimensions and the like of each part of the top sheet 2A are preferably set as follows.
The height L1 (see FIG. 7) of the convex portion 21 is preferably 2 to 6 mm, more preferably 3 to 5 mm.
The maximum diameter L2 (see FIG. 7) of the convex portion 21 is preferably 1 to 10 mm, more preferably 2 to 5 mm.

[Absorbent core]
The absorbent core 40 contains an absorbent material. Examples of the absorbent material contained in the absorbent core 40 include hydrophilic fibers and water-absorbing polymers. The absorbent core 40 may contain only one of the hydrophilic fiber and the water-absorbing polymer, or may contain both. The content of the absorbent material (hydrophilic fiber and water-absorbing polymer) is preferably 70 to 100% by mass, more preferably 95 to 100% by mass in the absorbent core 40. The absorbent core 40 can be manufactured according to a conventional method.

  The hydrophilic fiber (absorbent material) contained in the absorbent core 40 is a fiber having a hydrophilic surface and can form a sheet in which the fibers have a high degree of freedom in the wet state. For example, it can be used without particular limitation. Examples of such hydrophilic fibers include natural cellulose fibers such as wood pulp such as softwood kraft pulp (NBKP) and hardwood kraft pulp (LBKP), and non-wood pulp such as cotton pulp and straw pulp; regeneration of rayon, cupra and the like Cellulose fiber; hydrophilic synthetic fiber such as polyvinyl alcohol fiber and polyacrylonitrile fiber; synthetic fiber such as polyethylene terephthalate (PET) fiber, polyethylene (PE) fiber, polypropylene (PP) fiber, and polyester fiber is hydrophilized with a surfactant. These can be used, and one of these can be used alone or in admixture of two or more.

  As the water-absorbing polymer (absorbing material) contained in the absorbent core 40, various kinds of polymers conventionally used in the technical field can be used. For example, sodium polyacrylate, (acrylic acid-vinyl alcohol) ) Copolymer, cross-linked poly (sodium acrylate), (starch-acrylic acid) graft polymer, (isobutylene-maleic anhydride) copolymer and saponified product thereof, potassium polyacrylate, cesium polyacrylate, etc. These 1 type can be used individually or in mixture of 2 or more types. As the water-absorbing polymer, particles are usually used, but fibers may be used. The particulate water-absorbing polymer includes an amorphous type, a block type, a bowl type, a spherical particle agglomeration type, a spherical type and the like due to the difference in shape, and any type can be used.

  In the vortex method of the water-absorbing polymer contained in the absorbent core 40, the water absorption rate is preferably 1 to 60 seconds, more preferably 5 to 40 seconds. Moreover, the liquid flow rate under pressure of the water-absorbing polymer contained in the absorbent core 40 is 1 to 500 ml / min. Is more preferable, and more preferably 1 to 200 ml / min. It is. The method for measuring the water absorption rate and the liquid passing rate under pressure by the vortex method of the water-absorbing polymer is shown below.

<Measurement method of water absorption rate by vortex method>
In a 200 mL glass beaker, 50 mL of physiological saline (0.9 wt% sodium chloride aqueous solution, ion-exchanged water is used for adjustment) and a magnetic stirrer chip (center diameter 8 mm, both end diameter 7 mm, length 30 mm) The beaker is placed on a magnetic stirrer (HPS-100 manufactured by ASONE). The rotational speed of the magnetic stirrer is adjusted to 600 ± 60 rpm, and the physiological saline in the beaker is stirred. 2.0 g of the water-absorbing polymer as a measurement sample is put into the liquid at the center of the vortex of the saline solution being stirred, and the water absorption rate (seconds) of the water-absorbing polymer is measured according to JIS K7224 (1996). To do. Specifically, the stopwatch is started when the absorption of the water-absorbing polymer into the beaker is completed, and stopped when the stirrer tip is covered with the test liquid (when the vortex disappears and the liquid surface becomes flat). Stop the watch and record the time (in seconds) as the water absorption rate by vortex method. In the measurement, n = 5 was measured, the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value. Measurement is performed at 23 ± 2 ° C. and humidity 50 ± 5%, and the sample is stored in the same environment for 24 hours or more before measurement. In addition, when taking out and measuring a water absorbing polymer from a product (absorbent article), it carries out by the following method. First, the surface material, the back sheet, the mount, etc. are removed from the product to form a water absorbent polymer alone or a mixture of the water absorbent polymer and a fibrous material. The mixture of the water-absorbing polymer and the fibrous material is separated into the water-absorbing polymer and the fibrous material using a sieve. In addition, a water-absorbing polymer taken from at least five products is used.

<Measurement method of liquid flow rate under pressure>
In a 100 mL glass beaker, a sufficient amount of physiological saline (0.9% by weight sodium chloride water) to swell the measurement sample water-absorbing polymer 0.32 ± 0.005 g, for example, saturated absorption of the water-absorbing polymer Immerse in 5 times more saline and leave for 30 minutes. Separately, at the lower end of an opening of a vertically standing cylinder (inner diameter 25.4 mm), a wire mesh (mesh opening 150 μm, biocolumn sintered stainless steel filter 30SUS sold by Sansho Co., Ltd.) and a capillary (with an inner diameter of 2 mm) ( A filtration cylindrical tube having an inner diameter of 4 mm and a length of 8 cm) is prepared, and the contents of the beaker including the swollen measurement sample are put into the cylindrical tube with the cock closed. Open the cock and adjust the liquid level in the filtration cylinder to 5 cm above the 60 mL scale line. Next, a cylindrical rod having a diameter of 2 mm with a wire mesh having an opening of 150 μm and a diameter of 25 mm is inserted into the filtration cylindrical tube so that the wire mesh and the measurement sample are in contact with each other. Place a weight so that the load of. After standing for 1 minute in this state, the cock is opened to flow the liquid, and the time until the liquid level in the filtration cylindrical tube reaches the 40 mL scale line from the 60 mL scale line (that is, 20 mL of liquid passes) (T1). (Seconds) is measured with a stopwatch. Using the measured time T1 (seconds), the liquid flow rate under pressure at 2.0 kPa is calculated from the following equation. In the formula, T0 (seconds) is a value obtained by measuring the time required for 20 ml of physiological saline to pass through the wire mesh without putting the measurement sample in the filtering cylindrical tube. The measurement was performed 5 times (n = 5), the values at each of the upper and lower points were deleted, and the average value of the remaining three points was taken as the measured value.
Flow rate under pressure (ml / min) = 20 × 60 / (T1-T0)

The basis weight of the absorbent core 40, from the viewpoint of the absorption retention of excretory liquid such as urine that practically sufficient, preferably 50 to 800 g / m ^2, even more preferably 100 to 500 g / m ^2.

  As an absorptive core concerning the present invention, it replaces with flat absorptive core 40 (flat type absorptive core) which does not have a concavo-convex substantially, absorptive core 40A which has a concavo-convex shape shown in FIG. An uneven absorbent core) can also be used. As shown in FIG. 8, the absorbent core 40 </ b> A has a high basis weight portion 41 having a relatively large amount of absorbent material and a low basis weight portion 42 having a relatively small amount of absorbent material. 41 and the low basic weight part 42 are alternately formed in the predetermined direction. In the form shown in FIG. 8, the high basis weight portions 41 and the low basis weight portions 42 are alternately formed in the longitudinal direction X and the width direction Y, respectively. More specifically, as shown in FIG. 8, the absorbent core 40 </ b> A includes a linear low basis weight portion 42 </ b> X extending over the entire length along the longitudinal direction X of the absorbent core 40 </ b> A, and the absorbent core. A plurality of linear low basis weight portions 42Y extending over the entire length along the width direction Y of 40A are formed, and the low low weight portion 42 is formed in a lattice shape as a whole. A portion partitioned by the amount portions 42X and 42Y is a high basis weight portion 41. Each of the plurality of high basis weight portions 41 has a rectangular shape in plan view.

  Further, as shown in FIG. 8, the high basis weight portion 41 is thicker than the low basis weight portion 42 (42X, 42Y), and therefore the absorbent core 40A has a high basis weight portion 41 having a low basis weight portion. It has a concavo-convex shape raised compared to 42. When the absorbent core 40A has a concavo-convex shape, the skin-opposing surface and the non-skin-facing surface are not concavo-convex like the absorbent core 40, as compared to a substantially flat absorbent core. When the diaper 1 is worn, deformation of the absorbent core 40A (absorbent body 4), specifically, deformation of the absorbent core 40A into a shape that rises toward the skin of the diaper wearer is easily induced. Due to the deformability of the absorbent core 40A, the excretory part-facing portion in the crotch part C is easily deformed into a shape that is pressed against the skin of the diaper wearer when the diaper 1 is worn. This improves the comfort of the diaper wearer and effectively prevents leakage of body fluids such as urine.

  In the cross-sectional view of the absorbent core 40 </ b> A as shown in FIG. 8B, the low basis weight portions 42 (42 </ b> X, 42 </ b> Y) are unevenly distributed in the thickness direction of the absorbent core 40. More specifically, as shown in FIG. 8, the low basis weight portion 42 is unevenly distributed on the non-skin facing surface 40b side in the thickness direction T of the absorbent core 40A. And since the low basic weight part 42 is unevenly distributed by the non-skin opposing surface 40b side in the thickness direction T in this way, the high basic weight part 41 is the opposite side to the non-skin opposing surface 40b, ie, thickness direction. In T, it protrudes to the skin facing surface 40a side. Therefore, in the absorbent core 40A, the non-skin facing surface 40b (facing surface with the core wrap sheet 5B) is substantially flat with no unevenness, whereas the skin facing surface 40a (with the core wrap sheet 5A) is substantially flat. The opposite surface) has projections and depressions by a high basis weight portion 41 (convex portion) and a low basis weight portion 42 (non-convex portion or concave portion) located between the high basis weight portions 41, 41. Yes.

  In the diaper 1, when the absorbent core 40 </ b> A is used instead of the absorbent core 40, the absorbent core 40 </ b> A has a low basis weight portion 42 and a recess formed corresponding thereto (the material for forming the absorbent core 40 </ b> A is The non-existent space) allows the absorbent core 40A to be efficiently used by diffusing the excretory liquid while shortening the absorption time of the excretory liquid.

From the viewpoint of ensuring the above-described effects of the absorbent core 40A, it is preferable to set the dimensions and the like of each part of the absorbent core 40A as follows.
The ratio (S41 / S42) of the basis weight S41 of the high basis weight portion 41 of the absorbent core 40A and the basis weight S42 of the low basis weight portion 42 is preferably 1.25 to 10, more preferably 3 to 6. .
The basis weight S41 of the high basis weight portion 41 is preferably 100 to 600 g / m ² , more preferably 150 to 500 g / m ² , and the basis weight S 42 of the low basis weight portion 42 is preferably 10 to 150 g / m 2. ² and more preferably 30 to 100 g / m ² .
The ratio (T41 / T42) between the thickness T41 of the high basis weight portion 41 and the thickness T42 of the low basis weight portion 42 is preferably 1 to 20, and more preferably 1.5 to 10.
The thickness T41 of the high basis weight portion 41 is preferably 0.5 to 10 mm, more preferably 1 to 8 mm, and the thickness T42 of the low basis weight portion 42 is preferably 0.1 to 5 mm, more preferably 0. 2 to 3.0 mm.
High basis weight portion 41 has an area 50 cm ² per 25～45Cm ^2, which is preferably particularly 30～45Cm ² formation.

  The absorbent core 40 </ b> A having an uneven shape can be manufactured using a known fiber stacking apparatus in the same manner as the method for manufacturing the absorbent core of this type of absorbent article. The fiber stacking apparatus usually includes a rotating drum having a concave portion for accumulation on the outer peripheral surface, and supplies the absorbent material to the outer peripheral surface in a scattered state while rotating the rotary drum, and the absorbent material is supplied to the concave portion for collecting. The fiber is stacked in the accumulation recess by suction from the bottom surface, and the piled material in the accumulation recess is released from the accumulation recess by suction from the suction means arranged opposite to the accumulation recess. It is a device to transfer on. In the fiber stacking apparatus having such a configuration, by disposing a non-breathable member or a non-breathable member on a part of the breathable bottom surface of the concave portion for accumulation, etc. When the absorbent material is spread, it is difficult for the absorbent material to be deposited on the non-breathable portion, and the amount of the absorbent material in the non-breathable portion is smaller than that of other portions of the bottom surface. Less. Therefore, by manufacturing an absorbent core according to a conventional method using a fiber stacking device including a rotating drum in which a part of the bottom surface of the concave portion for accumulation is a non-permeability portion or a non-breathable portion, The portion corresponding to the air-impermeable portion is the low basis weight portion 42 (42X, 42Y), and the portion corresponding to the other portion of the bottom surface is the high basis weight portion 41, so that an absorbent core 40A having an uneven shape is obtained.

[Liquid permeable sheet]
As the liquid permeable sheet 9, various sheets interposed between the surface sheet and the absorber in the technical field can be used. For example, paper obtained by wet papermaking; manufactured by a card method Various non-woven fabrics such as non-woven fabric, air-through non-woven fabric, spunbonded non-woven fabric, melt blown non-woven fabric, spunlace non-woven fabric and needle punched non-woven fabric can be used. These nonwoven fabrics may be subjected to a hydrophilic treatment using a hydrophilic agent such as a surfactant. The basis weight of the liquid permeable sheet 9 is preferably 5 to 50 g / m ² and more preferably 10 to 30 from the viewpoint of liquid permeability.

[Back sheet etc.]
As other structural members other than the aforementioned skin-side structural members (core wrap sheet, surface sheet, absorbent core, liquid permeable sheet) in the diaper 1, those conventionally used in the technical field may be appropriately used. it can. Examples of the back sheet 3 include various liquids such as a resin film having no moisture permeability, a resin film having fine pores and moisture permeability, a nonwoven fabric such as a water-repellent nonwoven fabric, and a laminate of these and other sheets. An impermeable or water-repellent material can be used. Moreover, as the side sheet | seat 6, the thing similar to the back surface sheet 3 can be used.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, in the above-described embodiment, the absorbent core 40 is covered using the two core wrap sheets 5A and 5B. However, as shown in FIG. 9, only one core wrap sheet 5A may be used. . In that case, the single core wrap sheet 5 </ b> A covering the absorbent core 40 has a width that is two to three times the length of the absorbent core 40 in the width direction Y. In the absorbent body 4A shown in FIG. 9, the absorbent core 40 is placed at the center in the width direction Y of the single core wrap sheet 5A, and both sides in the width direction Y are on the upper surface side of the absorbent core 40. The sheet 5A is formed into a cylindrical shape by folding and joining both side edges by a known joining means such as a hot-melt adhesive, and obtained by turning upside down.

  Moreover, in the said embodiment, although what was called a deployment type disposable diaper was mentioned as one of the application examples of the absorbent article of this invention, in addition to the pants type disposable diaper previously shape | molded into the pants type, sanitary napkins, It can also be applied to panty liners (origami sheets), incontinence pads, and the like. All the parts of only the one embodiment described above can be used together as appropriate.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to such examples. Unless otherwise specified, “%” means “mass%”.

[Example 1]
An unfolded disposable diaper having the same basic configuration as the diaper 1 shown in FIGS. 1 and 2 was produced and used as a sample of Example 1.
As the surface sheet, an air-through nonwoven fabric having a basis weight of 20 g / m ² was used as a flat surface sheet having substantially no unevenness.
As the back sheet, a liquid-impermeable and moisture-permeable polyethylene resin film (containing calcium carbonate) having a basis weight of 25 g / m ² was used.
The absorbent core is a flat absorbent core having substantially no unevenness, in which a fibrous aggregate is held with particulate water-absorbing polymer (SAP), and fluff pulp 170 g / m ² and water absorption An absorptive core having a total basis weight of 430 g / m ² composed of a uniform mixture with 260 g / m ^{2 of the} conductive polymer was used. The total length of the absorbent core in the longitudinal direction was 360 mm, and the total length in the width direction (maximum length) was 110 mm.
As the core wrap sheet, an absorbent paper having the two-layer structure manufactured by the following method (the specific absorbent paper) was used.

[Manufacturing method of core wrap sheet used in Example 1]
A hydrophilic bulky fiber and pulp fiber are mixed so that the mass ratio of both fibers (hydrophilic bulky fiber / pulp fiber) is 8/2 to obtain an aggregate of fibers, and the aggregate is uniformly in water A slurry (paper material) having a fiber concentration of 2% by mass was prepared by dispersion to obtain a slurry for the first layer.
Also, pulp fibers (specific pulp fibers with a fiber roughness of 0.10 to 0.20 mg / m) are uniformly dispersed in water to prepare a slurry (paper material) with a fiber concentration of 2% by mass, and the slurry is beaten Then, adjust the freeness of the specific pulp fiber to 600 ml, and add PAE as a wet paper strength enhancer to 0.8% by mass with respect to the dry mass of all the fibers in the slurry. The mixture was sufficiently stirred so that a slurry for the second layer having a solid content concentration of 0.1% by mass was prepared.
The slurry for the first layer and the slurry for the second layer are respectively spread on a wire mesh paper making wire having a wire opening diameter of 90 μm (166 mesh), a paper layer is formed on the wire mesh paper making wire, and a suction box is used. After dehydrating the paper layer at a rate of 6 ml / (cm ² · sec), the wet first paper layer obtained from the first layer slurry and the wet second paper layer obtained from the second layer slurry. The two paper layers are stacked in a wet state, then pressed and dehydrated, further dried with a dryer, and the paper layer is peeled off from the dry surface with a doctor blade, and the crepe is applied with a speed ratio of the dryer and winding. Granted. Before the first paper layer and the second paper layer are overlaid, the first paper layer is immersed in a 5% by mass aqueous solution of PVA as a dry paper strength enhancer. Contained a dry paper strength enhancer. The two-layered absorbent paper (crepe paper) thus obtained was used as the sample of Example 1.

[Example 2]
An unfolded disposable diaper was prepared in the same manner as in Example 1 except that a concavo-convex surface sheet having substantially the same configuration as the surface sheet 2A shown in FIGS. 6 and 7 was used as the surface sheet. It was. The concavo-convex surface sheet used in Example 2 uses a flat air-through nonwoven fabric composed of 100% by mass of a core-sheath type composite fiber having PET as a core and PE as a sheath as a raw fabric. Produced by imparting an uneven shape to the original fabric. The concavo-convex surface sheet used in Example 2 has a basis weight of 30 g / m ² , the height of the convex portion (corresponding to L1 in FIG. 7) 4.0 mm, and the maximum diameter of the convex portion (corresponding to L2 in FIG. 7). It was 3.0 mm.

Example 3
An unfolded disposable diaper was produced in the same manner as in Example 2 except that an uneven absorbent core having substantially the same configuration as the absorbent core 40A shown in FIG. 8 was used as the absorbent core. It was. The concavo-convex absorbent core used in Example 3 is obtained by holding a particulate water-absorbing polymer in a fiber assembly, and is composed of a uniform mixture of fluff pulp 170 g / m ² and water-absorbing polymer 260 g / m ^2. It was an absorptive core with a total basis weight of 430 g / m ² , the overall length in the longitudinal direction was 360 mm, and the overall length in the width direction (maximum length) was 110 mm. Moreover, the uneven | corrugated type absorbent core used in Example 3 has a basis weight ratio (high basis weight part / low basis weight part) of high basis weight part and low basis weight part 5.2, basis weight of high basis weight part. the amount 520 g / m ^2, a basis weight 100 g / m ² of the low basis weight portion, the thickness ratio of the high basis weight portion and the low basis weight portion (high basis weight portion / low basis weight portion) 1.5, high basis weight portion thickness 3.0 mm, a thickness 2.0mm of low basis weight portion, the high basis weight portion has an area 50 cm ² per 40 cm ² was formed.

Example 4
An unfolded disposable diaper having the same basic configuration as the diaper 1 shown in FIG. 5 (having a liquid-permeable sheet between the top sheet and the absorbent body) was prepared and used as a sample of Example 4. An air-through nonwoven fabric having a basis weight of 25 g / m ² was used as the liquid-permeable sheet. The disposable diaper of Example 4 is the same as the disposable diaper of Example 1 except having a liquid-permeable sheet.

[Comparative Example 1]
An unfolded disposable diaper was produced in the same manner as in Example 1 except that a single-layer absorbent paper (crepe paper) produced by the following method was used as the core wrap sheet, and a sample of Comparative Example 1 was obtained.

[Method for producing core wrap sheet used in Comparative Example 1]
NBKP was uniformly dispersed in water to prepare a slurry (paper) having a fiber concentration of 2% by mass, and this slurry was passed through a beating machine to adjust the freeness of NBKP to 700 ml. Further, while diluting this slurry, PAE as a wet paper strength enhancer was added in an amount of 0.78% by mass with respect to the dry mass of all fibers in the slurry, and sufficiently stirred so that each component was uniform. The slurry was adjusted to a solid content concentration of 0.1% by mass. The slurry thus obtained was spread on a wire mesh paper wire having a wire opening diameter of 90 μm (166 mesh), a paper layer was formed on the wire mesh paper wire, and 6 ml / (cm ² · sec) was formed using a suction box. After the paper layer was dehydrated at a speed, the paper layer was dried with a drier, and a crepe was applied while peeling the paper layer with a doctor blade from the dry surface at a speed ratio of drier and winding. The thin paper (crepe paper) thus obtained was used as a core wrap sheet in Comparative Example 1. In Tables 1 and 2 below, the composition of the single layer of the single layer core wrap sheet is described in the column for the first layer.

[Comparative Example 2]
An unfolded disposable diaper was produced in the same manner as in Comparative Example 1 except that the same surface sheet as the concavo-convex surface sheet used in Example 2 was used.

[Comparative Example 3]
An unfolded disposable diaper was prepared in the same manner as in Comparative Example 1 except that the same absorbent core used in Example 3 was used as the absorbent core, and a sample of Comparative Example 3 was obtained.

In Table 1 below, the numerical value (mass%) in the fiber column means the ratio (mass basis) of the fiber to the total fibers in the first layer or the second layer, and is a component other than the fiber (additive). The numerical value (mass%) in a column means the ratio (mass basis) of the said component with respect to the dry mass of all the fibers in a 1st layer or a 2nd layer. Moreover, the detail of each component in following Table 1 is as follows.
Hydrophilic bulky fiber: HBA with a fiber roughness of 0.32 mg / m.
Pulp fiber: NBKP (trade name “Cariboo”, manufactured by Cariboo Pulp and Paper Company) with a fiber roughness of 0.15 mg / m.
Specific pulp fiber: NBKP (trade name “Cariboo”, manufactured by Cariboo Pulp and Paper Company) having a fiber roughness of 0.15 mg / m (the same fiber as the pulp fiber).
Dry paper strength enhancer: PVA (Kuraray Co., Ltd., trade name “VPB107-1”).
-Wet paper strength enhancer: PAE (manufactured by Seiko PMC, trade name “WS4030”).

[Evaluation]
About each sample (disposable diaper) of an Example and a comparative example, the liquid permeation | transmission time of each structural member was measured by the said method, and the liquid return amount was measured by the following measuring method. The results are shown in Table 2 below.

<Measurement method of liquid return amount>
In a state where the disposable diaper is spread in a flat shape and fixed on a horizontal surface with the surface sheet facing upward, 40 g of artificial urine is injected and absorbed onto the surface sheet in the center of the absorbent body, and left for 10 minutes. 40 g of artificial urine was injected and absorbed. Such artificial urine injection operation was repeated 5 times, and a total of 200 g of artificial urine was absorbed in the diaper. Next, 20 sheets of 4A filter paper made by Toyo Roshi Kaisha, Ltd. were stacked on the artificial urine absorption site in the diaper, and a load was further applied for 10 minutes to absorb the artificial urine absorbed in the diaper on the filter paper. The load was such that 6 kg was applied to an area of 30 cm × 15 cm. After 10 minutes, the load was removed, and the weight of the filter paper that absorbed artificial urine was measured. The weight of the filter paper before artificial urine absorption was subtracted from this weight, and the value was taken as the liquid return amount. The smaller the liquid return amount, the higher the utilization efficiency of the absorber (absorbent core) and the higher the evaluation.

  The composition of artificial urine is as follows. 1.94% by mass of urea, 0.7954% by mass of sodium chloride, 0.11058% by mass of magnesium sulfate (septahydrate), 0.06208% by mass of calcium chloride (dihydrate), 0.19788% by mass of potassium sulfate , Polyoxyethylene lauryl ether 0.0035 mass% and ion-exchanged water (remaining amount).

  As shown in Tables 1 and 2, Example 1 uses a two-layer core wrap sheet and the liquid permeation time of each layer is in the above relationship (T3> T4> T1 ≧ T2 or T3> T4> T1 ≧ T5 ≧ T2) As for -4, the liquid return amount was small compared with Comparative Examples 1-3 using the core wrap sheet | seat of a single layer structure. In addition, Examples 2 and 3 using the uneven surface sheet as the surface sheet had less liquid return than Examples 1 and 4 using the flat surface sheet. From the above, in order to obtain an absorbent article having excellent liquid permeability and liquid diffusibility and high utilization efficiency of the absorber, a core wrap sheet having a two-layer structure is used, and the surface sheet, the core wrap sheet, and It is important that the liquid permeation time of each absorbent core is in the above relationship, and the surface sheet has a large number of convex portions protruding toward the wearer's skin side and concave portions adjacent to the convex portions. When it has, it turns out that a more preferable result is obtained.

1 disposable diaper (absorbent article)
2, 2A, 2B, 2C Topsheet 2a Topsheet skin facing surface 2b Topsheet non-skin facing surface 21 Topsheet convex portion 22 Topsheet concave portion 23 Topsheet upper layer 24 Topsheet lower layer 25 Topsheet space 3 Back sheet 4, 4A Absorbent body 40, 40A Absorbent core 40a Absorbent core skin facing surface 40b Absorbent core non-skin facing surface 5A, 5B Core wrap sheet 51 First layer 52 of core wrap sheet 52 Core wrap sheet Second layer 9 Liquid-permeable sheet

Claims (5)

An absorbent body and a surface sheet disposed on the skin facing surface side of the absorbent body, the absorbent body containing an absorbent material, and a core covering at least the skin facing surface of the absorbent core An absorbent article configured to include a wrap sheet,
The core wrap sheet includes a first layer and a second layer that overlaps the first layer, and the first layer is located closer to the top sheet than the second layer;
The liquid permeation time T1 measured by the following method of the top sheet, the liquid permeation time T2 of the first layer, the liquid permeation time T3 of the second layer, and the liquid permeation time T4 of the absorbent core are T3 Absorbent article in a relationship of>T4> T1 ≧ T2.
<Measurement method of liquid permeation time>
Two cylinders with an inner diameter of 35 mm that open at the top and bottom are arranged vertically with the axes of both cylinders aligned, and an 8 cm square measurement sample is sandwiched between the upper and lower cylinders. 40 g ± 1 g of physiological saline is supplied. The supplied physiological saline passes through the measurement sample or is absorbed by the measurement sample and disappears from the upper cylinder. The time from the start of the physiological saline supply until the physiological water surface becomes the same position as the surface of the measurement sample is measured, and this time is defined as the liquid permeation time.   A liquid permeable sheet is arranged between the top sheet and the absorber, and when the liquid permeation time of the liquid permeable sheet is T5, there is a relationship of T3> T4> T1 ≧ T5 ≧ T2. The absorbent article according to claim 1.   The first layer contains hydrophilic bulky fibers and pulp fibers having a fiber roughness of 0.30 mg / m or more, and the second layer is a specific pulp fiber having a fiber roughness of 0.10 to 0.20 mg / m. The absorptive article according to claim 1 or 2 containing.   The absorptive article according to any one of claims 1 to 3 in which said surface sheet has many convex parts which project toward a wearer's skin side, and a crevice adjacent to this convex part, respectively.   The absorbent core has a high basis weight part with a relatively large amount of the absorbent material and a low basis weight part with a relatively small amount of the absorbent material, and the high basis weight part and the low basis weight part. The absorbent article according to any one of claims 1 to 4, wherein and are alternately formed in a predetermined direction.

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