JP5833415B2 - Absorbent articles - Google Patents

Description

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

  This type of absorbent article includes a liquid-permeable top sheet, a liquid-impermeable back sheet, and a vertically long absorbent body disposed between the two sheets, and the absorbent body is hydrophilic such as wood pulp. 2. Description of the Related Art There are known ones that include an absorbent core containing fibers 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 an absorbent core-forming material such as a water-absorbing polymer at the time of manufacturing the absorbent body, and plays a role of wrapping and shaping the absorbent core after the manufacture. Conventionally, water-permeable sheets such as thin paper and nonwoven fabric are used as the core wrap sheet.

  Conventionally, in absorbent articles, the ability to absorb and retain soft stool has been a problem. Specifically, a situation occurs in which soft stool remains on the surface sheet without passing through the surface sheet, or soft stool that has permeated through the surface sheet returns to the surface sheet without being held by the absorber. And it brings about complicated skin wiping work. Therefore, various techniques have been proposed for the purpose of promptly moving the soft stool away from the skin and improving the performance of accommodating and holding the soft stool at a position far from the skin (absorbability such as soft stool).

For example, Patent Literature 1 includes a liquid-permeable second sheet between a surface sheet and an absorbent as an absorbent article having excellent soft stool absorbability, and the core wrap sheet constituting the absorbent is the second article. A non-woven fabric located between the sheet and the absorbent core constituting the absorbent body and having a density in the range of 0.01 to 0.2 g / cm ³ , and a crepe paper covering the non-skin facing side of the absorbent core What is composed of is described.

  Patent Document 2 discloses a predetermined range of pore sizes (pore diameters) and distributions formed by entanglement of constituent fibers as a low-diffusibility transmission paper for absorbent articles obtained by a wet papermaking method. Are controlled. The low-diffusibility transmission paper described in Patent Document 2 includes hydrophilic fibers as constituent fibers and is treated with a sizing agent so as to have a specific pore diameter distribution. It exhibits diffusibility and high permeability and is useful as a sub-layer sheet (second sheet) disposed between the top sheet and the absorber (core wrap sheet).

  In addition, a sheet having a relatively low basis weight such as a core wrap sheet is required to have a sheet strength that does not cause tearing during manufacturing in addition to having high liquid permeability. Conventionally, a method of adding a paper strength enhancer has been adopted as a method for improving sheet strength. For example, Patent Literature 3 includes a dry paper strength enhancer and a wet strength enhancer, and the tensile strength is specified. Household hygiene tissue paper in range is described. Incidentally, the household sanitary thin paper described in Patent Document 3 is applied to uses such as roll paper, tissue paper, dust paper, etc. where sensory characteristics such as flexibility and touch feeling are important, and disclosed in Patent Document 3. The main technology that is being used aims to achieve both of these sensory characteristics and sheet strength.

Japanese Patent No. 4390747 JP 2009-148322 A Japanese Patent Laid-Open No. 2005-124484

  In the core wrap sheet described in Patent Document 1, a portion of the absorbent core facing the skin-facing surface is made of a nonwoven fabric having synthetic fibers as constituent fibers, and the constituent fibers are fixed by heat-sealing. ing. Therefore, even if the synthetic fiber (constituent fiber) is hydrophilized, there is a possibility that inconveniences such as clogging occur when loose stool containing solid matter passes through the core wrap sheet, Unless such a disadvantage is prevented by making the distance relatively long, the absorbability of soft stool may be lowered. However, if the interfiber distance in the nonwoven fabric as the core wrap sheet is increased, the absorbent core-forming material such as the water-absorbing polymer that has fallen off from the absorbent core may pass through the nonwoven fabric and leak to the outside. In the core wrap sheet, it has been difficult to achieve both improvement of soft stool absorbability and prevention of leakage of the absorbent core forming material. In order to solve this problem, the absorbent article described in Patent Document 1 has a multilayered absorbent body and prevents the absorbent polymer from falling off by forming a layer that does not contain the absorbent polymer in the upper layer.

  In order to increase the liquid permeability of the core wrap sheet, a method of reducing the basis weight of the constituent fibers of the sheet and reducing the density of the sheet is effective. Since the number of inter-fiber bonding points of the constituent fibers is reduced, the sheet strength may be reduced. When the sheet strength of the core wrap sheet decreases, the core wrap sheet may be damaged during manufacture, and the absorbent core forming material may leak from the damaged portion during use. The sheet strength and liquid permeability of the core wrap sheet are in a trade-off relationship, and it is difficult to achieve a good balance between the two. Patent Documents 1 to 3 do not disclose effective means for solving such a problem.

  Accordingly, an object of the present invention is to provide an absorbent article that is excellent in absorbability of a highly viscous liquid such as soft stool and in which leakage of the absorbent core forming material is prevented.

The present invention includes an absorbent body, and the absorbent body includes an absorbent core including hydrophilic fibers and a water-absorbing polymer and having a shape that is long in one direction, and a core wrap sheet that covers the absorbent core. The core wrap sheet includes high-liquid-permeable paper disposed to face the skin-facing surface of the absorbent core, and the high-liquid-permeable paper is The amount is 8 to 20 g / m ² , the density is 0.05 to 0.2 g / cm ³ , the liquid permeation time measured by the following method is 600 seconds or less, and the dry tensile strength in the conveying direction during production is 600 cN. The problem is solved by providing an absorbent article having a thickness of 25 mm or more.

<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, the sheet to be measured is sandwiched between the upper and lower cylinders, and in that state, in the upper cylinder, 10 g ± 1 g of a highly viscous liquid (viscosity 290 mPa · s) obtained by mixing glycerin and ion-exchanged water at a mass ratio of the former: the latter = 94: 6 is supplied. The supplied highly viscous liquid passes through the measurement target sheet or is absorbed by the measurement target sheet and disappears from the upper cylinder. The time from when the supply of the high-viscosity liquid is started until the liquid surface of the high-viscosity liquid reaches the same position as the surface of the sheet to be measured is measured, and the time is defined as the liquid permeation time.

  ADVANTAGE OF THE INVENTION According to this invention, the absorptive article which was excellent in the absorbability of highly viscous liquids, such as a loose stool, and the leak of the absorptive core formation material was prevented.

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 explanatory diagram of a method for measuring the liquid permeation time. FIG. 4 is a cross-sectional view schematically showing a cross section in the width direction of an absorbent body according to another embodiment of the absorbent article of 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, as shown in FIGS. 1 and 2, a liquid-permeable surface sheet 2 that forms a skin facing surface, and a liquid impermeable material that forms a non-skin facing surface. It has a back sheet 3 that is permeable or water repellent (hereinafter collectively referred to as liquid impervious), and an absorbent body 4 that is disposed between both sheets 2 and 3, and is formed substantially vertically long. Yes. 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 portion C is located at the center of the diaper 1 in the longitudinal direction X. 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 the present specification, the longitudinal direction is a direction along the long side of an absorbent article (disposable diaper) or a component (for example, an absorbent core), and the width direction is a direction orthogonal to the longitudinal direction. In the figure, the direction indicated by the symbol X is the longitudinal direction of the diaper 1 (absorbent core 40), and the direction indicated by the symbol Y is the width direction of the diaper 1 (absorbent core 40). Further, the skin facing surface is a surface that is directed to the wearer's skin when the absorbent article (disposable diaper) is worn in the absorbent article (disposable diaper) or a component thereof, and the non-skin facing surface is absorbent. In the article (disposable diaper) or a component thereof, the surface is directed to the side opposite to the skin side (clothing side) when the absorbent article (disposable diaper) is worn.

  As shown in FIG.1 and FIG.2, the side sheet | seat 62 to which the elastic member 61 is being fixed in the expansion | extension state is distribute | arranged to the 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 63 are arranged along the longitudinal direction X on the left and right leg portions arranged around the wearer's legs, and a pair of leg portions when worn due to the contraction of the elastic members 63. Leg gathers are formed. As shown in FIG. 2, the pair of side sheets 62, 62, the top sheet 2, the absorber 4, the elastic member 63, and the back sheet 3 are joined by a known joining means such as a hot melt adhesive.

  Moreover, as shown in FIG. 1, the waist elastic member 64 is arrange | positioned in the waist opening end part of the back side part A and the abdominal side part B, and the waist gathers are formed. The waist elastic member 64 has a belt-like form, and is sandwiched and fixed between the top sheet 2 and the back sheet 3 over substantially the entire width of the diaper 1 along the width direction Y of the diaper 1. In addition, a plurality of waistline gather forming elastic members 65 are disposed on the left and right side portions of the waistline portion in the back side portion A to form a pair of left and right waistline gathers. The waistline gather forming elastic member 65 is arranged substantially linearly in the width direction Y, and is sandwiched and fixed between the top sheet 2 and the back sheet 3.

  As shown in FIG. 1, a pair of fastening tapes 8, 8 are provided on both side edges along the longitudinal direction X of the back side A of the diaper 1. More specifically, the both sides along the longitudinal direction X of each of the back side portion A and the ventral side portion B extend outward in the width direction Y from both side edge portions along the longitudinal direction X of the absorbent body 4. Side flaps 7 and 7 are formed, and a fastening tape 8 is attached to each side flap 7 so as to extend outward in the width direction Y. A fastening part 81 made of a male member of a mechanical surface fastener is attached to the fastening tape 8.

  In addition, a non-skin facing surface of the ventral side B of the diaper 1 is formed with an attachment region 9 made of a female member of a mechanical surface fastener. The to-be-attached region 9 is formed by bonding and fixing a female member of a mechanical surface fastener to the non-skin facing surface of the back sheet 3 by a known joining means (for example, an adhesive or heat seal). The fastening part 81 of the tape 8 can be detachably fastened.

  Hereinafter, the absorber 4 will be described in detail. As illustrated in FIGS. 1 and 2, the absorbent body 4 includes an absorbent core 40 and a core wrap sheet 5 that covers the absorbent core 40. As shown in FIG. 1, the absorbent core 40 has a long shape in one direction (longitudinal direction X of the diaper 1), and the longitudinal center portion is constricted.

  The absorptive core 40 is comprised including a hydrophilic fiber and a water absorbing polymer. The hydrophilic fiber can be used without particular limitation as long as it 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. Examples of such hydrophilic fibers include natural cellulose fibers such as wood pulp such as softwood kraft pulp and hardwood kraft pulp, and non-wood pulp such as cotton pulp and straw pulp; regenerated cellulose fibers such as rayon and cupra; polyvinyl alcohol fiber , Hydrophilic synthetic fibers such as polyacrylonitrile fibers; synthetic fibers such as polyethylene terephthalate (PET) fibers, polyethylene (PE) fibers, polypropylene (PP) fibers, and polyester fibers that have been hydrophilized with a surfactant. These 1 type can be used individually or in mixture of 2 or more types.

  As the water-absorbing polymer, various polymers conventionally used in the technical field can be used without particular limitation. Examples thereof include polyacrylic acid soda, (acrylic acid-vinyl alcohol) copolymer, polyacrylic acid. Cross-linked soda, (starch-acrylic acid) graft polymer, (isobutylene-maleic anhydride) copolymer and saponified product thereof, potassium polyacrylate, cesium polyacrylate, and the like are used alone. Or a mixture of two or more. 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.

  The total content of the hydrophilic fibers and the water-absorbing polymer in the absorbent core 40 is, for example, 70 to 100% by mass, preferably 85 to 100% by mass, and more preferably 95 to 100% by mass with respect to the mass of the absorbent core 40. 100% by mass. The content ratio of the hydrophilic fiber to the water-absorbing polymer is preferably hydrophilic fiber: water-absorbing polymer = 1/9 to 9/1 from the viewpoint of sufficiently holding and fixing urine, loose stool and the like. / 7 to 7/3 is more preferable. In the absorbent core 40, other components other than the hydrophilic fiber and the water-absorbing polymer, for example, various additives such as pH buffer material, hydrophilic fine powder, deodorant, non-hydrophilic fiber and the like, if necessary May be included.

The basis weight of the absorbent core 40 is preferably 200 to 600 g / m ² , particularly 300 to 600 g / m ² , from the viewpoint of sufficiently holding and fixing urine, loose stool and the like. From the same viewpoint, the density of the absorbent core 40 is preferably 0.10 to 0.30 g / cm ³ , more preferably 0.15 to 0.30 g / cm ³ . The thickness of the absorbent core 40 under no load is preferably 1.5 to 3.5 mm, and more preferably 1.7 to 3.0 mm.

  As shown in FIG. 2, the core wrap sheet 5 is disposed so as to face the skin facing surface 40 a of the absorbent core 40 (located on the skin facing surface 40 a side of the absorbent core 40). And covering both side edges 40s and 40s along the longitudinal direction X of the absorbent core 40 (disposed on the non-skin facing surface 40b side of the absorbent core 40). And a low liquid permeability sheet 52. More specifically, the core wrap sheet 5 includes two sheets 51 and 52 having different dimensions in the width direction Y, one of which is the longitudinal direction X and the width of the absorbent core 40. A highly liquid-permeable paper 51 having substantially the same dimensions as the length in the direction Y (the length in the longitudinal direction and the width direction of the absorbent core here means the maximum length in each direction). One sheet is a low liquid permeability sheet 52 wider than the high liquid permeability paper 51. The high liquid permeable paper 51 and the low liquid permeable sheet 52 have the same length in the longitudinal direction X. The high liquid permeability paper 51 covers substantially the entire skin facing surface 40a of the absorbent core 40. The low liquid permeability sheet 52 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. The protruding portion is wound up on the highly liquid permeable paper 51 disposed opposite to the skin facing surface 40 a of the absorbent core 40 and covers both side edges along the longitudinal direction X of the highly liquid permeable paper 51. The high liquid permeable paper 51 and the absorbent core 40 and the low liquid permeable sheet 52 and the absorbent core 40 may be joined by a known joining means such as a hot melt adhesive. .

  As one of the main features of the diaper 1 of the present embodiment, the highly liquid-permeable paper 51 that is directly disposed on the skin facing surface 40a of the absorbent core 40 without interposing other members has good strength characteristics. The point which is excellent in liquid permeability is mentioned.

That is, the high liquid-permeable paper 51 is set to have a relatively low basis weight and density from the viewpoint of improving liquid permeability. Specifically, the high liquid-permeable paper 51 has a basis weight of 8 to 20 g. / M ² , preferably 10 to 14.5 g / m ² , more preferably 11 to 14 g / m ² , and the density of the highly liquid-permeable paper 51 is 0.05 to 0.2 g / cm ³ , Preferably it is 0.07-0.20 g / cm < ³ >, More preferably, it is 0.10-0.20 g / cm < ³ >. If the basis weight of the highly liquid-permeable paper 51 is less than 8 g / m ² or the density is less than 0.05 g / cm ³ , the paper strength may be remarkably reduced, and the basis weight of the highly liquid-permeable paper 51 is 20 g. If the density exceeds / m ² or the density exceeds 0.2 g / cm ³ , the effect of improving the liquid permeability may be poor. The basis weight and density of the highly liquid-permeable paper 51 (core wrap sheet 5) are measured as follows.

<Measurement method of basis weight of core wrap sheet>
After conditioning the sample (core wrap sheet) 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 measured with a two-digit scale below the decimal point. The basis weight of the measurement piece is calculated by dividing the measured value by the area. 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.

<Method of measuring the density of the core wrap sheet>
Ten 20 cm square samples (core wrap sheets) are stacked to form a laminate, and the laminate is cooled and solidified with liquid nitrogen, and then the vicinity of the center of the laminate is cut with a cutter. Then, of the 10 samples, one having no shear applied to the cross section generated by cutting with the cutter is selected, and the thickness of the selected sample is measured with an optical microscope. In addition, the thickness of the sample is not the length (apparent thickness) from the bottom to the top of the concavo-convex part when the sample has concavo-convex parts such as crepes described later, but the part where the constituent fibers are deposited Length (substantial thickness). The weight W of the 20 cm square sample whose thickness has been measured in this way is measured using a balance with two decimal places. The target density is calculated by dividing the weight W of the sample by the volume V of the sample calculated by the following equation (that is, by W / V). In the following formula, T is the thickness (cm) of the sample, A is the crepe rate (%) of the sample, and B is the length of one side (20 cm) of the sample. The crepe rate is measured by a measurement method described later. When the core wrap sheet to be measured does not have a crepe (when the crepe rate is 0%), A = 0 in the following equation. V = {T × B × B × (100 + A) / 100}

  Such a low basis weight, low density, highly liquid permeable paper 51 has a liquid permeation time measured by the following method of 600 seconds or less, preferably 400 seconds or less, more preferably 300 seconds or less. . The shorter the liquid permeation time, the higher the liquid permeability and the higher the evaluation. The high-liquid-permeable paper 51 whose liquid permeation time is in the above range is excellent in liquid permeability and has a relatively low viscosity excretion such as loose stool and menstrual blood in addition to a relatively low viscosity excretion such as urine. Can be quickly permeated and absorbed quickly by the absorbent core 40, and the surface liquid residue is hardly generated.

<Measurement method of liquid permeation time>
As shown in FIG. 3, two cylinders 91 and 92 having an inner diameter of 35 mm with upper and lower ends opened are arranged vertically with the axes of both cylinders 91 and 92 being aligned, and the sheet S to be measured (high liquid A transparent paper) is sandwiched between the upper and lower 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 a state where the sheet S to be measured is sandwiched and fixed between the upper and lower cylinders 91 and 92, the viscosity of 290 mPa · s indicated by the symbol W in FIG. Measure with a vibratory viscometer CJV 5000. Put about 10 g of high viscosity liquid into the sample container, set it in the viscometer, insert the sensitive plate at a predetermined level, select the measurement range to 50 mV, and press the measurement switch to start the measurement. 10 g ± 1 g of a highly viscous liquid of 60 seconds after the start of measurement, measured at 25 ° C.). The supplied highly viscous liquid passes through the measurement target sheet S or is absorbed by the measurement target sheet S and disappears from the upper cylinder 91. The time until the liquid level of the high-viscosity liquid reaches the same position as the surface of the sheet S to be measured (the surface on the upper cylinder 91 side) from the start of the supply of the high-viscosity liquid is measured. And The highly viscous liquid is prepared by mixing glycerin and ion exchange water at a mass ratio of the former: the latter = 94: 6.

  Thus, while the high liquid permeability paper 51 has a liquid permeation time of 600 seconds or less and excellent liquid permeability, the low liquid permeation constituting the core wrap sheet 5 together with the high liquid permeability paper 51. The liquid sheet 52 is inferior in liquid permeability because the liquid permeation time exceeds 600 seconds. That is, in the absorbent core 40 according to the present embodiment, the skin facing surface 40a that directly receives excretion fluid such as loose stool is covered with the highly liquid-permeable paper 51 that is excellent in liquid permeability, and is located on the opposite side. The skin facing surface 40b and both side edge portions 40s, 40s are covered with a low liquid permeability sheet 52 having poor liquid permeability.

  Due to such a covering form of the core wrap sheet 5, in the absorbent body 4, the liquid excreted when the diaper 1 is worn and permeated through the top sheet 2 is quickly drawn into the absorbent body 4 by the action of the highly liquid-permeable paper 51. And is absorbed and held by the absorbent core 40. Further, since the non-skin facing surface 40b and both side edges 40s, 40s of the absorbent core 40 are covered with the low liquid permeable sheet 52, the liquid once absorbed and held in the absorbent core 40 is absorbed by the absorbent core 40. Even if it leaks to the outside, it is prevented from leaking to the outside of the absorber 4 by the low liquid permeability sheet 52, so-called side leakage is effectively prevented. From the viewpoint of ensuring the effect of preventing leakage by the low liquid permeable sheet 52, the liquid permeation time of the low liquid permeable sheet 52 is preferably 600 to 3000 seconds, and more preferably 600 to 3000. 2000 seconds.

As the low-liquid-permeable sheet 52, paper, non-woven fabric, or the like can be used. In particular, crepe paper having crepes (crepe-like wrinkles) is preferably used. From the viewpoint of allowing the liquid permeation time to exceed 600 seconds, the basis weight of the low liquid permeability sheet 52 is preferably 13 to 20 g / m ² , more preferably 15 to 18 g / m ² . The density of the sheet 52 is preferably 0.10 to 0.30 g / cm ³ , more preferably 0.20 to 0.25 g / cm ³ , and the crepe rate of the low liquid permeability sheet 52 is preferably 5 to 20%, more preferably 7 to 15%. The crepe can be applied by a conventionally known method, and the crepe rate is measured as follows.

<Measurement method of crepe rate>
A rectangular shape of 200 mm in the length direction (conveying direction at the time of manufacture of the sheet, MD) and 100 mm in the width direction (direction orthogonal to the MD, CD) is cut out from the measurement target sheet. 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 the length C of the MD after immersion for 10 minutes is 220 mm, the crepe rate of the sheet calculated by the above formula is 10%.

  The high-liquid-permeable paper 51 will be further described. As described above, the high-liquid-permeable paper 51 has a strength that is relatively low in terms of basis weight and density from the viewpoint of improving liquid permeability. Specifically, the dry tensile strength in the transport direction (Machine Direction, abbreviated as MD) during production is 600 cN / 25 mm or more, preferably 600 to 1500 cN / 25 mm, more preferably 700 to 1200 cN / 25 mm. It is. The highly liquid-permeable paper 51 having a dry tensile strength of MD in the above range has a practically sufficient strength, hardly breaks at the time of manufacturing the diaper 1, and leaks the absorbent core forming material. It is hard to wake up.

  From the same viewpoint, the dry tensile strength in the direction perpendicular to the MD of the highly liquid-permeable paper 51 (Cross machine direction, abbreviated as CD) is preferably 150 cN / 25 mm or more, more preferably 150 to 350 cN / 25 mm, Particularly preferred is 170 to 300 cN / 25 mm. The dry tensile strength is measured as follows.

<Measurement method of dry tensile strength>
The sheet to be measured (highly liquid permeable paper) is allowed to stand for 12 hours in an environment of room temperature 23 ° C. ± 2 ° C. and relative humidity 50% RH ± 2%, and is conditioned to 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. Further, the dry tensile strength of CD is obtained by cutting a rectangular shape having dimensions of 150 mm for CD and 25 mm for MD from the humidity-controlled sheet, and using this as a sample, and pulling this sample so that the CD is in the tensile direction. Attached to the chuck of the testing machine without tension, the dry tensile strength of the CD is determined by the same procedure as described above.

  The high liquid permeability paper 51 may have crepes (crepe-like wrinkles). When the highly liquid permeable paper 51 has a crepe, the crepe is generated when the dried fiber web (highly liquid permeable paper 51) is peeled off from the Yankee dryer or the like in the dryer part with a doctor knife or the like. A dry crepe is preferred. Paper having a crepe has higher liquid permeability than paper having no 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. In the present invention, based on such knowledge, from the viewpoint of balance between liquid permeability and strength characteristics, the crepe rate of the high liquid permeability paper 51 is 5 to 30%, particularly 5 to 20%, especially 7 to 15%. % Is preferable. The crepe rate is measured by the above method.

  As such a high liquid permeability paper 51 having good strength characteristics and excellent liquid permeability, the following high liquid permeability paper A is preferably used. Highly liquid permeable paper A is a thin paper mainly composed of an aggregate of two types of hydrophilic cellulose fibers having different fiber roughness, to which a paper strength enhancer is added, and as the two types of hydrophilic cellulose fibers, The first pulp contains a first pulp having a fiber roughness of 0.13 to 0.16 mg / m and a second pulp having a fiber roughness of 0.17 to 0.20 mg / m. The difference in fiber roughness between the second pulp and the second pulp is 0.01 to 0.07 mg / m, and the freeness of the aggregate is 400 to 550 ml. Hereinafter, the highly liquid permeable paper A will be described in detail.

  Highly liquid-permeable paper A (thin paper) contains an aggregate of two types of hydrophilic cellulose fibers having different fiber roughness as an essential component. 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 highly liquid-permeable paper A includes an aggregate of two types of hydrophilic cellulose fibers having different thicknesses, thereby achieving both strength characteristics and liquid permeability.

  The high liquid permeability paper A has a fiber roughness of 0.13 to 0.16 mg / m, preferably 0.135 to 0.155 mg / m, more preferably 0.8 as the two kinds of hydrophilic cellulose fibers. The first pulp is 14 to 0.15 mg / m, and the fiber roughness is 0.17 to 0.20 mg / m, preferably 0.175 to 0.195 mg / m, more preferably 0.18 to 0.19 mg. / M, and the second pulp is thicker than the first pulp. Thus, by using a relatively thick pulp as a part of the constituent fibers of the paper, the paper becomes rough and the liquid permeability is improved. Pulp is obtained by converting plant fibers such as wood, kidneys and leaves into single fibers by a chemical or mechanical method.

  And the difference of the fiber roughness of the 1st pulp and 2nd pulp contained in the high liquid permeability paper A is 0.01-0.07 mg / m, Preferably it is 0.02-0.06 mg / m. More preferably, it is 0.03-0.05 mg / m. If the difference in fiber roughness between the two pulps is less than 0.01 mg / m, the effect of improving the liquid permeability is poor, and if the difference in fiber roughness exceeds 0.07 mg / m, the strength of the paper may be significantly reduced. .

  The average fiber length of each of the first pulp and the second pulp is preferably 2 to 3 mm, more preferably 2.2 to 2.8 mm. When the average fiber lengths of the two pulps are in the above ranges, the effects of good balance of the entanglement between the fibers and good formation of the paper are obtained. The average fiber length of both pulps may be the same or different. 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 (pulp) 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.

  The content mass ratio between the first pulp and the second pulp (first pulp / second pulp) is preferably 3/7 to 7/3, more preferably 4 from the viewpoint of the balance between strength characteristics and liquid permeability. / 6 to 6/4. If the second pulp having a relatively large fiber diameter is too small, sufficient liquid permeability may not be obtained. Conversely, if the second pulp is too large, the strength of the high liquid-permeable paper A is rapidly reduced. May occur.

  The first pulp and the second pulp (hydrophilic cellulose fibers) are fibers having a fiber roughness in the above-mentioned range and having a hydrophilic surface, and the fibers have a high degree of freedom between each other in the wet state. If it can form, it can use without a restriction | limiting especially. Examples of such hydrophilic cellulose fibers include natural cellulose fibers such as wood pulp such as softwood bleached kraft pulp (NBKP) and hardwood bleached kraft pulp (LBKP), and non-wood pulp such as cotton pulp and straw pulp; rayon, cupra Recycled cellulose fibers such as: hydrophilic synthetic fibers such as polyvinyl alcohol fibers and polyacrylonitrile fibers; synthetic fibers such as polyethylene terephthalate (PET) fibers, polyethylene (PE) fibers, polypropylene (PP) fibers, and polyester fibers with surfactants The thing etc. which carried out the hydrophilization process are mentioned, These 1 type can be used individually or in mixture of 2 or more types.

  Among these hydrophilic cellulose fibers, NBKP is particularly preferable, and each of the first pulp and the second pulp is preferably NBKP. Further, 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.

  Highly liquid-permeable paper A is mainly composed of an aggregate of two kinds of hydrophilic cellulose fibers (first pulp and second pulp) having different fiber roughness. Here, “mainly” means that the contents of the first pulp and the second pulp are 50% by mass or more. The content is preferably 70 to 80% by mass, more preferably 80 to 100% by mass, from the viewpoint of achieving both strength characteristics and liquid permeability.

  In the highly liquid-permeable paper A, the freeness of the aggregate of the two types of hydrophilic cellulose fibers (first pulp and second pulp) is set to 400 to 550 ml. That is, the freeness of each of the first pulp and the second pulp is in the range of 400 to 550 ml. Freeness is a value indicated by Canadian Standard Freeness (C.S.F.) specified in JIS P8121, and is a value of pulp beating (a process of mechanically tapping and grinding pulp in the presence of water). It is a value indicating the degree. Usually, the smaller the freeness value, the stronger the degree of beating, the greater the damage of the fibers due to beating, and the more fibrillation proceeds. Fibers having a freeness in the above range are easily entangled with each other because fibrillation is in progress. For this reason, for example, from the viewpoint of improving liquid permeability, the fibers are made by reducing the basis weight (reducing density) of paper. 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 550 ml and the fibrillation has not progressed relatively. Therefore, the highly liquid-permeable paper A mainly composed of an aggregate of fibers having a freeness of 400 to 550 ml can have good strength characteristics.

  The freeness of the aggregate of the two types of hydrophilic cellulose fibers used in the highly liquid-permeable paper A is preferably 450 to 525 ml, more preferably 475 to 510 ml. When the freeness is less than 400 ml, the strength improvement effect due to the entanglement of the fibers is saturated, and the fiber cutting is promoted, and the permeation time may be delayed. The beating of the fiber aggregate is a known method such as a beader or a disc refiner for a stock (slurry) in which each hydrophilic cellulose fiber (first pulp and second pulp) constituting the fiber aggregate is mixed and dispersed. This can be carried out according to a conventional method using a beating machine.

  The highly liquid-permeable paper A may contain fibers other than the first pulp and the second pulp, and the other fibers may not be hydrophilic cellulose fibers such as both pulps. Other fibers include, for example, hardwood bleached kraft pulp (LBKP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP) and other wood pulp; Non-wood pulp such as kenaf and hemp; synthetic fibers such as polyester fiber, rayon fiber, acrylic fiber, and the like. The content of these other fibers is preferably 20% by mass or less.

  From the viewpoint of obtaining good strength characteristics (tensile strength), a paper strength enhancer is added to the high liquid permeability paper A. The paper strength enhancer includes a dry paper strength enhancer that improves the dry paper strength and a wet paper strength enhancer that improves the wet paper strength, either of which may be used.

  As the dry paper strength enhancer, conventionally known dry paper strength enhancers can be used. For example, carboxymethyl cellulose (CMC) and salts thereof, polyacrylamide resins and salts thereof, cationized starch, polyvinyl alcohol (PVA). These can be used, and one of these can be used alone or in combination of two or more. 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 are particularly preferable because of their high versatility and low aggregation effect between fibers.

  As the wet paper strength enhancer, conventionally known wet paper strength enhancers can be used. For example, epoxidized polyamide polyamine resin (PAE), urea-formalin resin, melamine-formalin resin, dialdehyde starch, polyethyleneamine, Examples include methylolated polyamide, and one of these can be used alone or two or more of them can be used in combination. Among these wet paper strength enhancers, PAE is particularly preferable.

  When two or more kinds of paper strength enhancers are used in the highly liquid-permeable paper A, as a preferred combination thereof, 1) a combination of one dry paper strength enhancer and one wet paper strength enhancer, and 2) A combination of two dry paper strength enhancers and one wet paper strength enhancer. In the combination of 1) above, the one dry paper strength enhancer is preferably an anionic PAM salt, and the one wet paper strength enhancer is preferably PAE. In the combination 2), the two dry paper strength enhancers are preferably CMC salts and anionic PAM salts, and one wet paper strength enhancer is preferably PAE.

  Further, as in 2) above, when two kinds of dry paper strength enhancers are CMC salt and anionic PAM salt, and one kind of wet paper strength enhancer is PAE, anionic PAM salt Is preferably 8 million or more, more preferably 10 million or more, and particularly preferably 15 million or more, and the upper limit of the weight average molecular weight of the anionic PAM salt is preferably 25 million. Thus, in the case of using three kinds of specific paper strength enhancers, if the weight average molecular weight of the salt of anionic PAM which is one of them is in the above range (8 million to 25 million), an anion In addition to the effect of improving the strength of the highly liquid-permeable paper A due to the expression of the adhesive property of the salt of the conductive PAM itself, the strength of the highly liquid-permeable paper A can be improved by improving the yield of the salt of the CMC. Due to the improvement effect, better strength characteristics of the highly liquid-permeable paper A can be obtained. In addition, when the weight average molecular weight of the anionic PAM salt is 25 million or less, the dispersibility and viscosity of the anionic PAM salt in water during production of the highly liquid-permeable paper A can be kept relatively low. Good results are obtained in terms of handling properties and prevention of dirt on the paper machine.

  The addition amount of the paper strength enhancer in the high liquid permeability paper A is preferably 0.01 to 1.5% by mass, more preferably 0.00%, based on the dry mass of all the constituent fibers of the high liquid permeability paper A. It is 03-1.2 mass%. If the added amount of the paper strength enhancer is too small, sufficient strength properties such as tensile strength cannot be obtained. If the added amount of the paper strength enhancer is too large, the highly liquid-permeable paper A is cured (decrease in texture). In addition, there is a possibility that the formation of the high liquid permeability paper A may be reduced due to the sticking of the paper to the Yankee dryer or the adhesion of the paper strength enhancer to the mesh drum during the production of the high liquid permeability paper A. .

  When a combination of one or more dry paper strength enhancers and one or more wet paper strength enhancers is used as the paper strength enhancer, the total added mass of the dry paper strength enhancer and the wet paper strength enhancer The ratio to the total added mass (the former / the latter) is preferably 0.01 to 0.5, more preferably 0.03 to 0.35.

  In addition, as described above, when two kinds of CMC salt and anionic PAM salt are used as the dry paper strength enhancer and one type of PAE is used as the wet paper strength enhancer, all of the high liquid permeable paper A is used. The addition amount of each paper strength enhancer with respect to the dry mass of the constituent fibers is preferably 0.05 to 0.5 mass%, more preferably 0.1 to 0.3 mass% of the salt of CMC, The salt is preferably 0.001 to 0.1% by mass, more preferably 0.02 to 0.05% by mass, and the PAE is preferably 0.5 to 1.5% by mass, more preferably 0.6 to 1.2% by mass.

  The highly liquid-permeable paper A may contain components other than the fibers such as the first pulp and the second pulp (hydrophilic cellulose fibers) and the paper strength enhancer described above. As other components, for example, fillers such as talc, dyes, color pigments, antibacterial agents, pH adjusters, yield improvers, water resistance agents, antifoaming agents and the like are generally used as raw materials for papermaking and additives. These can be used, and one of these can be used alone or in combination of two or more.

  Highly liquid-permeable paper A can be produced by a known wet papermaking method. The wet papermaking method includes a stock preparation step for preparing a stock (slurry) made of an aqueous dispersion of fibers such as NBKP, and a paper making step for drying while transporting a fiber made from the stock into a fiber web. It is what has. 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 above-mentioned dry paper strength enhancer and wet paper strength enhancer are usually added to the stock in the stock preparation step. Usually, the wet paper strength enhancer and the dry paper strength enhancer are added in the order of the paper strength enhancer, but the order of addition of the paper strength enhancer in the present invention is not limited to this, and the order of addition may be reversed. Both may be added simultaneously. 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.

The high liquid permeability paper A is excellent in air permeability in addition to strength characteristics and liquid permeability. The reason is mainly because it mainly comprises an aggregate of two types of hydrophilic cellulose fibers having different fiber roughness. In order to investigate the relationship between the use of two types of hydrophilic cellulose fibers having different fiber roughness and the breathability of thin paper, the present inventors prepared two types of thin paper (samples A and B) having different pulp compositions. The air permeability was measured. Sample A includes the first pulp and the second pulp as the fiber material, and is a high liquid permeability paper II described later. Sample B includes only the first pulp as the fiber material, and the high liquid permeability described later. Paper I. Both samples A and B had a basis weight of 13 g / m ² . The air permeability is measured as follows.

<Measurement method of air permeability>
The air permeability is measured according to JIS P8117. After preparing 32 sheets of 15 cm square measurement object sheets (thin paper) and drying them with hot air dryer for 30 minutes with hot air at 105 ° C., all 32 sheets are stacked to form one laminate, and the laminate is B Set on the air permeability meter. Then, in the B-type air permeability meter, the time required to reach 300 cc is measured using 0 cc of the marked line as a start. The above operation is performed 5 times, and the average value of the obtained five measurement times is defined as the air permeability of the measurement target sheet (thin paper). The unit of air permeability is “s / 32P · 300 cc” and represents the time (seconds) required for 300 cc of air to escape through 32 sheets. It can be evaluated that the smaller the value of the air permeability, the easier the air can escape and the better the air permeability.

  Sample B (highly liquid permeable paper I described later) using only the first pulp as the fiber material had an air permeability in the range of 2.1 to 2.7 s / 32 P · 300 cc, whereas the fiber material Sample A (highly liquid permeable paper II described later) using two kinds of pulps (first and second pulps) having different fiber roughness as the air permeability is 1.6 to 2.2 s / 32 P · In the range of 300 cc, the value of air permeability of sample A was smaller than that of sample B. From this, it can be seen that it is effective to improve the air permeability of the thin paper to make the thin paper mainly composed of an aggregate of two kinds of hydrophilic cellulose fibers having different fiber roughnesses. It is clear that the highly liquid-permeable paper A is excellent in air permeability.

  The high liquid permeable paper 51 is not limited to the above-described high liquid permeable paper A, and may be any paper having basis weight, density, liquid permeation time, and MD dry tensile strength within the above ranges. For example, the highly liquid-permeable paper 51 is mainly composed of NBKP (conifer bleached kraft pulp) having a freeness of 400 to 550 ml, preferably 475 to 525 ml, and more preferably 490 to 510 ml. It may be a thin paper (crepe paper) that is added and has a crepe rate of 5 to 30%, preferably 5 to 20%, more preferably 7 to 15%. Here, “mainly” means that the content of NBKP having a freeness in such a range is 50% by mass or more. The content is preferably 50 to 100% by mass, more preferably 80 to 100% by mass, from the viewpoint of obtaining good strength characteristics. In such crepe paper, the description of the highly liquid-permeable paper A is appropriately applied to points that are not particularly described, such as specific examples of the paper strength enhancer.

  If the formation material of each part in the diaper 1 is demonstrated, as the surface sheet 2 and the back surface sheet 3, various things conventionally used in the said technical field can be used. As the surface sheet 2, various liquid-permeable sheet materials such as a nonwoven fabric and an apertured film can be used. As the back sheet 3, various liquid impervious materials 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. Or water repellent materials can be used. Moreover, as the side sheet | seat 62, the thing similar to the back surface sheet 3 can be used.

  The diaper 1 of the present embodiment is used in the same manner as a known unfolded disposable diaper. In the diaper 1 of the present embodiment, the portion of the core wrap sheet 5 that is disposed on the skin facing surface 40a side of the absorbent core 40 is the highly liquid-permeable paper 51. Compared to the absorbent article described in Patent Document 1, which is formed of a nonwoven fabric that is excellent in absorbability (repeated absorbability) of excretory fluids such as loose stool, the absorbent core-forming material such as a water-absorbing polymer Leakage hardly occurs and the manufacturing cost is reduced. Moreover, since the site | part arrange | positioned at the non-skin opposing surface 40b side of the absorptive core 40 in the core wrap sheet | seat 5 of the diaper 1 of this embodiment is the low liquid permeability sheet 52, it is hard to raise | generate a side leak.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention. For example, the core wrap sheet 5 in the above embodiment is composed of the high liquid permeable paper 51 and the low liquid permeable sheet 52, but may be composed of only the high liquid permeable paper 51. In that case, the core wrap sheet 5 may be composed of two high liquid permeable papers 51. For example, in the embodiment shown in FIG. 2, the low liquid permeable sheet 52 may be replaced with the high liquid permeable paper 51. good.

  Alternatively, as shown in FIG. 4, the core wrap sheet 5 may be composed of a single highly liquid permeable paper 51. In the embodiment shown in FIG. 4, as the core wrap sheet 5, a single highly liquid-permeable paper 51 having a width that is two to three times the length of the absorbent core 40 in the width direction Y is used. . In the absorbent body 4 shown in FIG. 4, the absorbent core 40 is placed at the center in the width direction Y of one sheet of high liquid permeability paper 51, and both sides of the high liquid permeability paper 51 in the width direction Y are disposed. Folded to the upper surface side of the absorbent core 40, both edges in the width direction Y of the highly liquid permeable paper 51 are joined by a known joining means such as a hot melt adhesive, and the highly liquid permeable paper 51 is attached. It is formed in a cylindrical shape and obtained by turning it upside down.

  Moreover, the absorbent article of the present invention may be a pants-type disposable diaper, an absorbent pad, a sanitary napkin, or the like previously formed in a pants shape, in addition to a deployable disposable diaper having a fastening tape.

  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%”.

[Production Method of Highly Liquid Permeable Paper I]
NBKP (Cariboo Pulp and Paper Company, trade name “Cariboo”, manufactured in North America) is uniformly dispersed in water to prepare a slurry with a fiber concentration of 2% by mass. Adjusted. Further, an anionic PAM sodium salt (dry paper strength enhancer, manufactured by MT Aqua Polymer, trade name “Akofloc A95”) as a first paper strength enhancer was added to this slurry with respect to the dry mass of all fibers in the slurry. 0.2 mass%, and then PAE (wet paper strength enhancer, trade name “WS4030”, manufactured by Seiko PMC Co., Ltd.) as the second paper strength enhancer, based on the dry weight of all the fibers in the slurry. Then, 0.2% by mass was added and sufficiently stirred so that each component was uniform. 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 dryer, and the paper layer was peeled off from the dry surface with a doctor blade, and a crepe was applied at a speed ratio of the dryer and the winding. The thin paper (crepe paper) thus obtained was designated as a high liquid permeability paper I.

[Method for Producing Highly Liquid Permeable Paper II and III]
A thin paper (crepe paper) was produced in the same manner as the high-liquid-permeable paper I except that the type of pulp (fiber roughness), freeness, and the like were changed as appropriate, and designated as high-liquid-permeable papers II and III, respectively. The high liquid permeability papers II and III are the above-described high liquid permeability paper A, respectively.

The details of the pulp (NBKP) used in the high liquid-permeable papers I to III are as follows (described in ascending order of fiber roughness). These pulps were obtained through Nippon Paper Pulp Trading or Itochu Corporation.
-Fiber roughness 0.13mg / m (trade name "Northwood", manufactured by ConFor)
-Fiber roughness 0.15mg / m (Brand name "Cariboo", Cariboo Pulp and Paper Company)
-Fiber roughness 0.18mg / m (trade name "ARAUCO", manufactured by ARAUCO)
・ Fiber roughness 0.2mg / m (trade name "Crofton CK", Unifibra)

  Various evaluation results of the high liquid permeability papers I to III are shown in Table 1 below. The dry tensile strength and the liquid permeation time were measured by the methods described above.

[Example 1]
An unfolded disposable diaper as shown in FIGS. 1 and 2 was produced and used as a sample of Example 1. In Example 1, the core wrap sheet is composed of the two highly liquid permeable papers I, and the low liquid permeable sheet is not used. As the surface sheet, an air-through nonwoven fabric having a basis weight of 25 g / m ² and comprising synthetic fibers as constituent fibers was used. The air-through nonwoven fabric was composed of a core-sheath type composite fiber (thickness: 2.1 dtex, surface treatment with a surfactant, and liquid permeability) having a core made of polypropylene and a sheath made of linear polyethylene. As the back sheet, a composite film in which a porous film having a basis weight of 20 g / m ^{2 and} a spun pond made of polypropylene having a basis weight of 20 g / m ² are bonded with a 1.5 g / m ² hot-melt adhesive is used. It was. The porous film constituting the back sheet is obtained by uniformly mixing 100 parts by mass of a linear polyethylene resin having a density of 0.925 g / m ³ with 150 parts by mass of calcium carbonate and 4 parts by mass of an ester compound as a third component. After the inflation molding, the film was uniaxially stretched in the longitudinal direction. As the absorbent core, NB416 manufactured by Wafer User is used as the hydrophilic fiber, Sunwet IM997 manufactured by Sundia is used as the water-absorbing polymer, and the mass ratio of the hydrophilic fiber to the water-absorbing polymer is the former / the latter = 10. A mixed fiber type absorbent core having a basis weight of 470 to 10/7 and a basis weight of 470 g / m ² was used. The total length in the longitudinal direction of the absorbent core is 360 mm, the total length in the width direction (maximum length) is 110 mm, the basis weight is 470 g / m ² , the density is 0.17 g / cm ³ , and the thickness under no load is 2.7 mm. Met.

[Examples 2 to 4 and Comparative Example 1]
In Example 1, a core wrap sheet (one sheet disposed on the skin facing surface side of the absorbent core and another sheet disposed on the non-skin facing surface side of the absorbent core) as shown in Table 2 below. Except for the construction, unfolded disposable diapers were produced in the same manner as in Example 1, and these were used as samples of Examples 2 to 4 and Comparative Example 1. The low liquid permeability sheet I used in Examples and Comparative Examples was a crepe paper having a basis weight of 16 g / m ² , a density of 0.23 g / cm ³ , and a crepe rate of 10%.

  Various evaluation results of each sample (disposable diaper) of Examples and Comparative Examples are shown in Table 2 below. Soft stool absorbability and side leakage prevention properties were evaluated by the following methods.

<Soft stool absorbability>
With a disposable diaper spread in a flat shape and fixed on a horizontal surface with the top sheet facing upward, 10 g pseudo-soft stool, which is a model of highly viscous liquid, is fixed to the center of the absorbent body using a syringe from the top sheet side. The batch injection was carried out at a high speed (6 seconds) and left for 5 minutes under a load of 3.5 kPa. At this time, an OHP film was sandwiched between a weight for applying a weight and a disposable diaper. Thereafter, the amount of pseudo-soft stool adhering to the OHP film was measured, and the measured value was defined as the skin adhesion amount. The amount absorbed by the absorbent core was defined as the amount of soft stool absorption. The smaller the skin adhesion amount and the greater the amount of loose stool absorption, the better the stool absorption and the higher the evaluation. The components of the artificial soft stool were bentonite 28.0 g, glycerin 14.0 g, ion-exchanged water 114.1 g, emulgen 130K 0.03% by weight aqueous solution (Kao) 14.2 g, and the viscosity was 300 mPa · s (A &amp;・ Measure with a day-day vibration viscometer CJV 5000. Stir about 170 g of pseudo soft stool in a 300 ml beaker with a stirrer at 300 rpm for 60 seconds, immediately set in the viscometer, insert the sensitive plate at a predetermined level, and set the measurement range. Select 50 mV and start measurement by pressing the measurement switch.The value 60 seconds after the start of measurement, measured at 25 ° C.).

<Side leakage prevention>
While expanding the disposable diaper into a flat shape and fixing the top sheet on the horizontal plane with the top sheet facing upward, 40 g of physiological saline is applied to the center of the absorbent body of the diaper while pressing through the top sheet with 2 kPa. Was injected and absorbed, and after 10 minutes from the injection of physiological saline, 40 g of physiological saline was injected and absorbed. This operation is repeated until the total injection amount of the physiological saline reaches 160 g. After the physiological saline is injected, whether or not the physiological saline flows outward from the side along the longitudinal direction of the diaper in the width direction (i.e., side leakage occurs). Whether or not there was) was visually observed. A case where no side leakage was observed even after the total injection amount of physiological saline reached 160 g, and no side leakage was observed after the total injection amount reached 120 g, but the total injection amount became 160 g. The case where lateral leakage was observed later was evaluated as Δ, and the case where lateral leakage was observed after the total injection amount reached 120 g was determined as ×.

  As is clear from the results shown in Table 2, the disposable diaper of each example in which the core wrap sheet opposed to the skin-facing surface of the absorbent core is a specific highly liquid-permeable paper has the core wrap sheet Compared with the disposable diaper of the comparative example, which is a low liquid permeability sheet, the amount of loose stool attached to the skin is small, the amount of loose stool absorption is large and the stool absorbability is excellent, and the side leakage prevention property is also excellent. there were. In particular, in the disposable diapers of Examples 2 to 4, in which the core wrap sheet disposed opposite to the non-skin facing surface of the absorbent core is a low liquid permeable sheet, the entire core wrap sheet is a specific high liquid permeable paper. Compared with the disposable diaper of Example 1, it is excellent in the side leakage prevention property, and the effectiveness of the combination of such a high liquid permeability paper and a low liquid permeability sheet is clear.

1 Absorbent article (disposable diaper)
2 Top sheet 3 Back sheet 4 Absorbent body 40 Absorbent core 40a Absorbent core skin facing surface 40b Absorbent core non-skin facing surface 40s Absorbent core side edge 5 Core wrap sheet 51 Highly liquid permeable paper 52 Low Liquid permeable sheet

Claims (4)

Comprising an absorbent body, the absorbent body comprising a hydrophilic fiber and a water-absorbing polymer and having an elongated shape in one direction, and a core wrap sheet covering the absorbent core. An absorbent article,
The core wrap sheet includes a highly liquid permeable paper disposed to face the skin facing surface of the absorbent core,
The high liquid permeability paper has a basis weight of 8 to 20 g / m ² , a density of 0.05 to 0.2 g / cm ³ , a liquid permeation time measured by the following method of 600 seconds or less, and the absorption. Ri der dry tensile strength in the longitudinal direction in the same direction 600 cN / 25 mm or more sexual core,
The high liquid permeability paper is mainly composed of an aggregate of two kinds of hydrophilic cellulose fibers having different fiber roughness, and a paper strength enhancer is added,
The two kinds of hydrophilic cellulose fibers include a first pulp having a fiber roughness of 0.13 to 0.16 mg / m and a second pulp having a fiber roughness of 0.17 to 0.20 mg / m. An absorbent article in which the difference in fiber roughness between the first pulp and the second pulp contained is 0.01 to 0.07 mg / m, and the freeness of the aggregate is 400 to 550 ml .
<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, the sheet to be measured is sandwiched between the upper and lower cylinders, and in that state, in the upper cylinder, 10 g ± 1 g of a highly viscous liquid (viscosity 290 mPa · s) obtained by mixing glycerin and ion-exchanged water at a mass ratio of the former: the latter = 94: 6 is supplied. The supplied highly viscous liquid passes through the measurement target sheet or is absorbed by the measurement target sheet and disappears from the upper cylinder. The time from when the supply of the high-viscosity liquid is started until the liquid surface of the high-viscosity liquid reaches the same position as the surface of the sheet to be measured is measured, and the time is defined as the liquid permeation time.   The high-liquid-permeable paper mainly comprises softwood bleached kraft pulp having a freeness of 400 to 550 ml, wherein two or more kinds of paper strength enhancers are added, and the crepe rate is 5 to 30%. Absorbent articles. The core wrap sheets, the arranged opposite to the non-skin-facing side of the absorbent core and covering the both side edges along the longitudinal direction of the absorbent core, low liquid permeable claim includes sheets 1 or 2 The absorbent article as described. The absorbent article according to claim 3, wherein the low liquid permeability sheet is a crepe paper having a liquid permeation time measured by the method exceeding 600 seconds.

Images