Patent Publication Number: US-11376167-B2

Title: Apparatus for manufacturing absorbent body

Description:
TECHNICAL FIELD 
     The present invention relates to an apparatus for manufacturing an absorbent body. 
     BACKGROUND ART 
     Hygienic articles such as disposable diapers and sanitary items have absorbent bodies obtained by mixing absorbent fibers and water-absorbent resin. The water-absorbent resin used therein needs to be evaluated for various items in accordance with its application, and examples of evaluation items are various and include absorption capacity, absorption speed, absorption capacity under pressure, and gel strength. Also, as one evaluation of the water-absorbent resin, it is preferable to produce an absorbent body that is equivalent to the actual product as a test piece. Various techniques have been proposed, such as Patent Literature 1, for example, as techniques for manufacturing such an absorbent body. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2011-83545A 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, an apparatus disclosed in Patent Literature 1 is for manufacturing a large number of absorbent bodies as actual products, and thus this apparatus is large-scale, and the absorbent bodies cannot be manufactured unless a large amount of absorbent fibers and water-absorbent resin is used. Therefore, this apparatus is not appropriate for production of an absorbent body for testing. Also, the apparatus that is disclosed in Patent Literature 1 and manufactures the same type of product in a large amount is not appropriate in light of the fact that absorbent bodies for testing need to be modified as appropriate in accordance with the evaluation content such as the weight or the blending ratio of the absorbent fibers and the water-absorbent resin. 
     The present invention was made in order to solve this problem, and an object of the present invention is to provide an apparatus for manufacturing an absorbent body in which absorbent fibers and water-absorbent resin are mixed similarly to the actual product and the composition such as the blending ratio of these absorbent fibers and water-absorbent resin can be easily changed, with a simple configuration. 
     Solution to Problem 
     An apparatus for manufacturing an absorbent body according to the present invention includes a conveying unit that conveys an aggregate of absorbent fibers and a water-absorbent resin; a mixing unit that accepts the aggregate of the absorbent fibers and the water-absorbent resin that were conveyed by the conveying unit and mixes the absorbent fibers and the water-absorbent resin; a chamber portion that has an internal space through which the absorbent fibers and the water-absorbent resin that were mixed in the mixing unit fall; a stacking portion that is disposed below the chamber portion and has a recessed portion in which the absorbent fibers and the water-absorbent resin that fall through the chamber portion are stacked; and a suction unit that causes a negative pressure in the chamber portion, in which the mixing unit includes: a cylindrical body that is supported rotatably and has an outer circumferential surface on which recesses and protrusions are formed; a driving portion that rotates the cylindrical body; and a gap formation portion that forms a gap through which the aggregate of the absorbent fibers and the water-absorbent resin that were conveyed by the conveying unit pass, between the gap formation portion and the outer circumferential surface of the cylindrical body, the gap being smaller than a thickness of the aggregate of the absorbent fibers, and the gap formation portion includes: a connection portion that is located below the cylindrical body, is provided with a plurality of through holes, and connects the gap and the internal space of the chamber portion via the plurality of through holes; and a mixing portion that is disposed on at least an upstream side of the connection portion and is provided with recesses and protrusions facing the outer circumferential surface of the cylindrical body. 
     In the above-described apparatus for manufacturing an absorbent body, the water-absorbent resin can be dispersively disposed in contact with the aggregate of the absorbent fibers. At this time, the water-absorbent resin that is dispersively disposed in contact with the aggregate of the absorbent fibers can be dispersively disposed on an upper surface of the absorbent fibers. 
     In the above-described apparatus for manufacturing an absorbent body, the water-absorbent resin can be introduced into the gap at a time that is different from a time at which the aggregate of the absorbent fibers is introduced. 
     In the apparatus for manufacturing an absorbent body, the gap formation portion can have a plate-shaped mesh member, and the plate-shaped member can be disposed facing the outer circumferential surface of the cylindrical body in order to form the gap and constitute the connection portion and the mixing portion. 
     In the apparatus for manufacturing an absorbent body, the chamber portion can be formed such that its shape increases in size toward its bottom. 
     The apparatus for manufacturing an absorbent body can be configured such that a pressing member that presses the aggregate of the absorbent fibers that have not yet entered the gap is provided between the conveying unit and the mixing unit, and the pressing member is biased in a direction in which the aggregate of the absorbent fibers is pressed. 
     In the apparatus for manufacturing an absorbent body, a circumferential speed of the cylindrical body in the mixing unit can be larger than a conveying speed at which the aggregate of the absorbent fibers and the water-absorbent resin can be conveyed to the mixing unit by the conveying unit. 
     In the apparatus for manufacturing an absorbent body, the internal space of the chamber portion can include at least one guide member that guides the absorbent fibers and the water-absorbent resin downward. 
     In the apparatus for manufacturing an absorbent body, the stacking portion can include a plate-shaped air circulation member provided with a plurality of through holes and a frame member that is disposed on the air circulation member and forms the recessed portion, and the suction unit can be configured to suction air from the internal space via the air circulation member. 
     In the apparatus for manufacturing an absorbent body, the stacking portion can be configured detachably from a wall body that constitutes a side surface of the chamber portion. 
     In the apparatus for manufacturing an absorbent body, the chamber portion can have a length of 10 to 100 cm in a vertical direction and a maximum length of 10 to 100 cm in a lateral direction. 
     Advantageous Effects of Invention 
     According to an apparatus for manufacturing an absorbent body according to the present invention, absorbent fibers and water-absorbent resin are mixed similarly to an actual product, and it is possible to easily change the composition such as the blending ratio of these absorbent fibers and water-absorbent resin, with a simple configuration. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a front view showing a schematic configuration of one embodiment of a manufacturing apparatus according to the present invention. 
         FIG. 2  is a plan view of  FIG. 1 . 
         FIG. 3  is a cross-sectional view (a) and a plan view (b) of a stacking portion. 
         FIG. 4  is a plan view (a) and a partial front view (b) of an absorbent body obtained using a manufacturing apparatus according to a working example. 
         FIG. 5  is a plan view showing division of the absorbent body when absorbent pieces are produced. 
         FIG. 6  is a table showing the water-absorption properties of absorbent bodies manufactured using the manufacturing apparatus according to a working example. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, one embodiment of an apparatus for manufacturing an absorbent body according to the present invention will be described. This manufacturing apparatus is mainly for manufacturing an absorbent body for testing. In the present embodiment, a material body obtained by dispersively disposing water-absorbent resin in the vicinity of an aggregate of absorbent fibers is prepared, and an absorbent body in which the absorbent fibers and the water-absorbent resin are uniformly mixed is manufactured in this manufacturing apparatus. Therefore, in the present embodiment, before the manufacture, a body obtained by simply dispersively disposing water-absorbent resin on an aggregate of absorbent fibers is referred to as a “material body”, and a body obtained by mixing the absorbent fibers and the water-absorbent resin using the manufacturing apparatus is referred to as an “absorbent body”. However, the expression “uniformly mixed” above is merely an expression indicating a state in which the absorbent fibers and the water-absorbent resin are mixed sufficiently, and does not necessarily mean that the abundance ratio of the absorbent fibers and the water-absorbent resin is constant in all of the sites of the absorbent body. For example, an absorbent body in which the abundance ratio of the water-absorbent resin and the absorbent fibers varies between the lower portion and the upper portion of the absorbent body. Hereinafter, first, materials that constitute the absorbent body and the material body will be described, and thereafter, an apparatus for manufacturing the absorbent body will be described. 
     1. Absorbent Body and Material Body 
     As described above, the absorbent body and the material body according to the present embodiment include absorbent fibers and water-absorbent resin. Hereinafter, these will be described in detail. 
     (1-1) Absorbent Fibers 
     Hydrophilic fibers that were finely cut and crushed can be used as the absorbent fibers, for example. Examples of the hydrophilic fibers include cellulose fiber obtained from wood, such as cotton-like pulp, mechanical pulp, chemical pulp, and semi-chemical pulp; artificial cellulose fiber such as rayon and acetate; and fibers made of synthetic resin that is subjected to hydrophilic treatment, such as polyamide, polyester, and polyolefin. Moreover, the aggregates of the absorbent fibers have a shape with a thickness, such as a rectangle, circle, or polygon, due to stacking or interlacing multiple absorbent fibers. One type of aggregate having such a shape may be used alone or two or more types thereof may be used in combination. 
     (1-2) Water-Absorbent Resin 
     A known water-absorbent resin can be used as the water-absorbent resin. Specific examples of the water-absorbent resin include water-absorbent resins such as starch-acrylonitrile graft copolymer hydrolysates, substances obtained by neutralizing starch-acrylic acid graft polymers, saponified vinyl acetate-acrylic acid ester copolymers, and crosslinked partially neutralized acrylic acid polymers. Among these, from the industrial viewpoint such as supply capability and cost, crosslinked partially neutralized acrylic acid polymers are preferable. One type of water-absorbent resin may be used alone or two or more types thereof may be used in combination. 
     Examples of a method for manufacturing a crosslinked partially neutralized acrylic acid polymer include a reversed-phase suspension polymerization method and an aqueous solution polymerization method. Also, from the viewpoint of increasing the osmotic pressure and water-absorption capability of the water-absorbent resin, the degree of neutralization of the crosslinked partially neutralized acrylic acid polymer is preferably 50 mol % or more and more preferably 70 to 90 mol %. 
     Also, in order to increase the absorption capability under the load, the vicinity of the surface of the water-absorbent resin that is used is preferably crosslinked. 
     In general, the above-described water-absorbent resin is commercially available in a powder form, there is no particular limitation on the shape thereof, and examples of the shape include a spherical shape, an irregular crushed shape, a granular shape, a scaly shape, a short rod shape, and agglomerates thereof. 
     From the viewpoint of operability at the time of manufacture of the absorbent body, a medium particle size of the water-absorbent resin is preferably 200 to 600 μm, more preferably 250 to 500 μm, and even more preferably 300 to 450 μm. Note that in the present invention, the medium particle size of the water-absorbent resin is a value obtained using a measurement method below. 
     Measurement of Medium Particle Size 
     0.25 g of noncrystalline silica (Degussa Japan Co., Ltd., Siperant 200) is mixed into 50 g of water-absorbent resin powder as a lubricant. Next, JIS standard sieves are combined in the following order, starting from the top: a sieve having a sieve opening of 850 μm, a sieve having a sieve opening of 600 μm, a sieve having a sieve opening of 500 μm, a sieve having a sieve opening of 425 μm, a sieve having a sieve opening of 300 μm, a sieve having a sieve opening of 250 μm, a sieve having a sieve opening of 150 μm, and a saucer. Next, the mixture is introduced into the uppermost combined sieve, and is classified by shaking the sieves using a ro-tap shaker for 20 minutes. After classification, the masses of the mixture remaining on the sieves are calculated as mass percentages with respect to the total amount, the resulting values are integrated sequentially, starting from the largest particle size, and thereby the relationship between the sieve openings of the sieves and the value obtained by integrating the mass percentages of the mixtures remaining on the sieves is plotted on logarithmic probability paper. By connecting the plot on the probability paper with a straight line, a particle size corresponding to an integrated mass percentage of 50 mass % is denoted as the medium particle size. 
     There is no particular limitation on the content of the water-absorbent resin in the absorbent body, but from the viewpoint of obtaining a sufficient liquid absorption property also when the absorbent body according to the present invention is used in an absorbent article such as a diaper, the content of the water-absorbent resin is preferably 10 to 1000 g per square meter of the absorbent body (that is, 10 to 1000 g/m 2 ), more preferably 20 to 900 g/m 2 , and even more preferably 30 to 700 g/m 2 . From the viewpoint of achieving a sufficient liquid absorption property for the absorbent body and suppressing return of liquid in particular, this content is preferably 10 g/m 2  or more, and from the viewpoint of improving the permeability of liquid, this content is preferably 1000 g/m 2  or less. 
     The blending ratio of the water-absorbent resin in the absorbent body that can be produced in the present invention is preferably 5 to 90 mass %, more preferably 10 to 80 mass %, and even more preferably 15 to 70 mass %. When the blending ratio is less than 5 mass %, the amount of the water-absorbent resin is too small, which is not appropriate for an evaluation method. On the other hand, when the blending ratio exceeds 90 mass %, the absorbent fibers tend to separate from the absorbent body because the amount of the absorbent fibers is too small, which is not preferable. 
     (1-3) Modes of Material Body 
     The material body may have various modes.
     (i) The water-absorbent resin is dispersively disposed on the upper surface of an aggregate of absorbent fibers.   (ii) The water-absorbent resin is dispersively disposed on a lower surface of an aggregate of the absorbent fibers.   (iii) The water-absorbent resin is dispersively disposed on the upper surface of an aggregate of the absorbent fibers, and an aggregate of the absorbent fibers is disposed thereon.   (iv) A plurality of (iii) are stacked. That is, the aggregates of the absorbent fibers and the water-absorbent resins are stacked alternately.   (v) A mixture of the aggregates of the absorbent fibers and the water-absorbent resin is used. This mixture can be obtained by purchasing a commercially available absorbent body or taking out an absorbent body from a commercially available disposable diaper. Alternatively, the mixture can be obtained by manufacturing an absorbent body using the manufacturing method of the present invention.   (vi) The water-absorbent resin is disposed on the upstream side (rear side in a conveying direction) of the aggregates of the absorbent fibers in a direction (the conveying direction) in which the material body is introduced into a gap, which will be described later, and is conveyed toward the gap using a conveying means such as a belt conveyor.   (vii) The water-absorbent resin is disposed on the downstream side (a front side in the conveying direction) of the aggregates of the absorbent fibers, and is conveyed toward the gap using a conveying means such as a belt conveyor.   

     In (i) to (v) above, the absorbent fibers and the water-absorbent resin are in contact with each other, and thus the absorbent fibers and the water-absorbent resin are simultaneously introduced into the gap, which will be described later, whereas in (vi) and (vii), the absorbent fibers and the water-absorbent resin are introduced into the gap at different times. That is, the absorbent resin is first introduced into the gap and then the water-absorbent resin is introduced, or the water-absorbent resin is first introduced into the gap and then the absorbent fibers are introduced into the gap. Also, it is possible to repeat (vi) and (vii) respectively, or combine (i) to (vii) as appropriate. 
     Also, according to (vi) above, a large amount of the water-absorbent resin can be dispersed on the upper portion of the absorbent body, and according to (vii), a large amount of the water-absorbent resin can be dispersed on the lower portion of the absorbent body. Also, according to (v) above, it is possible to change the mixing ratio or mixed state of the absorbent fibers and the water-absorbent resin in the absorbent body that has already been produced. 
     2. Apparatus for Manufacturing Absorbent Body 
     Next, an apparatus for manufacturing an absorbent body will be described with reference to the drawings.  FIG. 1  is a front view showing a schematic configuration of this manufacturing apparatus, and  FIG. 2  is a plan view of  FIG. 1 . Hereinafter, for convenience, description will be given with reference to the orientation shown in  FIGS. 1 and 2 , but the apparatus according to the present invention is not limited by this orientation. 
     As shown in  FIGS. 1 and 2 , this manufacturing apparatus includes a rectangular parallelepiped housing  1 , and this housing  1  is provided with a conveying unit  2  that conveys a material body  100 , a mixing unit  3  that mixes absorbent fibers and a water-absorbent resin of the material body  100 , a chamber portion  4  having an internal space  40  through which the mixed absorbent fibers and the water-absorbent resin fall, a stacking portion  5  in which the absorbent fibers and the water-absorbent resin that have fallen are stacked, and a suction unit  6  that suctions air in the internal space  40  in the chamber portion  4 . Hereinafter, each part will be described in detail. 
     First, the conveying unit  2  will be described. The conveying unit  2  is provided on the upper surface of the housing  1 , and is constituted by a belt conveyor disposed on the right side of the upper surface of the housing  1 . That is, the conveying unit  2  includes a driven roller  21  that is disposed on the right side of the upper surface of the housing and extends in the front-back direction, a driving roller  22  that extends in the front-back direction near the center of the upper surface of the housing, and a conveying belt  23  that is bridged over these rollers  21  and  22 , and the driving roller is rotationally driven by a first motor (not shown). With this configuration, the material body  100  disposed on the conveying belt  23  moves leftward (see arrow A in  FIG. 1 ). Also, as described later, this conveying unit  2  is provided with a guide portion  7  that guides the material body  100  conveyed by the conveying belt  23  to the mixing unit  3 . Note that the speed of the conveying belt  23  is 0.1 to 20.0 mm/sec, for example. 
     Next, the mixing unit  3  will be described. The mixing unit  3  includes a cylindrical body  31  that is disposed on the left side of an upper end portion of the housing  1  and is rotatably supported by the housing  1 , a second motor (driving portion)  32  that drives this cylindrical body  31 , and a gap formation portion  33  for forming a gap between the gap formation portion and an outer circumferential surface of the cylindrical body  31  through which the material body  100  passes. The cylindrical body  31  has a surface on which recesses and protrusions are formed, and rotates about a rotation axis extending in the front-back direction. Moreover, the outer circumferential surface of the cylindrical body  31  and a left end portion of the above-described conveying unit  2  are close to each other. Therefore, the material body  100  conveyed leftward on the conveying unit  2  is guided to the outer circumferential surface of the cylindrical body  31  by the guide portion  7 , which will be described next. 
     The guide portion  7  includes a rod-shaped pressing member  71  having a circular cross section that presses the material body  100 . This pressing member  71  extends in the front-back direction so as to pass over the left end portion of the conveying unit  2 . Rod-shaped support members  72  are attached to two ends of the rotatable pressing member  71 . The support members  72  extend in a direction orthogonal to the pressing member  71  and are disposed to hold the conveying belt  23 . Moreover, tips of the support members  72  are rotatably attached to the upper surface of the housing  1 . Accordingly, the pressing member  71  freely swings centered on the tips of the support members  72  (see arrow B in  FIG. 1 ). Also, a gap is formed between the pressing member  71  and the conveying belt  23 , and the material body  100  passes through this gap. This gap is smaller than the thickness of the material body  100 , and may be about 0 to 50 mm, for example, in accordance with the thickness of the material body  100 . 
     Spring members  73  are attached between the two ends of the pressing member  71  and the upper surface of the housing  1 , and the pressing member  71  is biased downward by these spring members  73 . That is, when the material body  100  having a larger thickness than the gap between the pressing member  71  and the conveying belt  23  passes therethrough, the pressing member  71  is pushed upward against the spring members  73  and the material body  100  passes therethrough. However, the thickness of the material body  100  that is introduced into the mixing unit  3  is made as small as possible by preventing the pressing member  71  from being pushed upward by the spring members  73  as much as possible. 
     Furthermore, a support axis  74  is inserted so as to pass through, in the front-back direction, the tip of the support member  72  that is disposed rearward, and a roller  75  that is rotated by the conveying belt  23  is attached to a front end of this support axis  74 . This roller  75  rotates together with the support axis  74  along with the movement of the conveying belt  23  due to friction with the conveying belt  23 . On the other hand, a belt  76  is bridged between a rear end of the support axis  74  and a rear end in the axial direction of the pressing member  71 , and when the support axis  74  rotates, the pressing member  71  also rotates. Therefore, the pressing member  71  is configured to rotate in synchronization with the movement of the conveying belt  23 , and accordingly, the material body  100  is pushed toward the mixing unit  3  by rotation of the pressing member  71 . 
     The description of the mixing unit  3  will continue. The above-described second motor  32  is disposed on the left side of the cylindrical body  31 , a belt  35  is bridged over a rotation axis of this second motor  32  and the rotation axis of the cylindrical body  31 , and the cylindrical body  31  is rotated leftward by belt transmission (see arrow C in  FIG. 1 ). The rotation speed of the cylindrical body  31  may be 1000 to 5000 r/min, for example. 
     Next, the gap formation portion  33  will be described. The gap formation portion  33  includes a pair of circular frames  331  that are disposed outward from both sides of the cylindrical body  31  and whose outer diameter is slightly larger than that of the cylindrical body  31 . Moreover, a cover member  332  having an arc shaped cross section and a mesh member (plate-shaped member)  333  are detachably attached to the outer circumferential surfaces of these frames  331  so as to cover the cylindrical body  31 . The cover member  332  is formed by a cross-sectionally arc-shaped plate member that passes over the cylindrical body  31  near the pressing member  71  and extends toward the left end of the cylindrical body  31 . Also, the mesh member  333  is a thin mesh plate member that is made of metal or the like and is provided with multiple small holes, and has an arc shape so as to pass below the cylindrical body  31  from the left end of the cover member  332  and extends to the vicinity of the conveying unit. 
     As described above, the frames  331  are slightly larger than the outer diameter of the cylindrical body  31 , and thus gaps are formed between the cover member  332  attached on these frames  331 , the mesh member  333 , and the outer circumferential surface of the cylindrical body  31 , and the material body  100  passes through these gaps. However, it is preferable to make the gap between the mesh member  333  and the cylindrical body  31  smaller than the gap between the cover member  332  and the cylindrical body  31  by adjusting the frames, and the gap between the cover member  332  and the cylindrical body  31  may be 2 mm, and the gap between the mesh member  333  and the cylindrical body  31  may be 1 mm, for example. 
     Next, the chamber portion  4  will be described. The chamber portion  4  is constituted by a front panel  41  having a trapezoidal shape in front view, a rear panel (not shown), and a pair of side panels  43  that connect inclined sides to each other on both sides of these front panel  41  and rear panel, and the chamber portion  4  has the internal space  40  surrounded by these panels. An upper end and a lower end of this internal space  40  are open, and the width of the inner portion gradually increases in the horizontal direction as the lower end is approached. An upper end opening of the internal space  40  is disposed directly below the cylindrical body  31 , and gaps around the cylindrical body  31  and the internal space  40  communicate with each other via the mesh member  333 . 
     Furthermore, a plurality of guide members are disposed in the internal space  40 . Although the guide members can have various configurations, three guide members are provided in the present embodiment. That is, a first plate-shaped guide member  44  disposed near the upper end of the internal space  40  on the left side and a second plate-shaped guide member  45  that is disposed slightly below the first guide member  44  on the right side of the internal space  40  are provided, and a rod-shaped third guide member  46  that extends in the front-back direction is provided near the center of the internal space  40 . These three guide members  44  to  46  extend in the front-back direction so as to connect the front panel  41  and the rear panel (not shown). 
     The first guide member  44  extends downward and guides the mixed absorbent fibers and water-absorbent resin rightward in order to prevent the mixed absorbent fibers and water-absorbent resin from moving excessively leftward in the internal space  40 . The second guide member  45  extends downward and guides the absorbent fibers and the water-absorbent resin leftward such that the absorbent fibers and the water-absorbent resin that are guided rightward by the first guide member  44  do not move excessively to a right end of the internal space  40 . Also, the third guide member  46  guides the absorbent fibers and the water-absorbent resin that fall such that in particular, the water-absorbent resin falls uniformly to the left and the right of the internal space  40 . 
     Note that the length in the vertical direction of the chamber portion  4  is preferably 10 cm to 100 cm, the maximum length in the lateral direction is preferably 10 cm to 100 cm, the length in the vertical direction is more preferably 25 cm to 75 cm, and the maximum length in the lateral direction is more preferably 20 cm to 80 cm. The maximum length in the lateral direction refers to the length in the horizontal direction of the lower end portion in the front view of  FIG. 1  in the present embodiment, for example, and it is sufficient that any maximum length in the lateral direction of the chamber portion  4  is in this range. 
     Next, the stacking portion  5  will be described with reference to  FIG. 3 . The stacking portion  5  is disposed below the chamber portion  4  so as to cover the lower end opening of the chamber portion  4 , and is a site on which the absorbent fibers and the water-absorbent resin that have fallen are stacked. Specifically, as shown in  FIG. 3 , the stacking portion  5  includes a rectangular support frame  51  having a size similar to that of the lower end opening of the chamber portion  4 , a plate-shaped mesh air circulation member  52  that is fitted to this support frame  51  and provided with multiple small holes, and a frame member  53  disposed detachably from this air circulation member  52 , and the absorbent fibers and the water-absorbent resin are stacked in a recessed portion  531  surrounded by the frame member  53 . That is, a desired absorbent body is formed depending on the shape of the frame member  53 . Moreover, this stacking portion  5  can be drawn frontward below the chamber portion  4 . That is, a handle  54  is attached to a front portion of the support frame  51 , and the stacking portion  5  can be removed from the housing  1  by pulling this handle  54 . Note that the handle  54  preferably has a detachable structure such that the back and the front in the direction in which the stacking portion  5  is inserted can be reversed. 
     The suction unit  6  is disposed below this stacking portion  5 . The suction unit  6  is constituted by a suction opening through which the stacking portion  5  is suctioned from below and a suction apparatus such as a known cleaner or a vacuum pump, and suctions the air in the internal space  40  in the chamber portion  4  downward. That is, the air in the internal space  40  is suctioned downward via the air circulation member  52  of the stacking portion  5 . The negative pressure caused by this suction can be monitored by installing a differential pressure gauge in the chamber portion  4 , and an absorbent body can be produced under a constant negative pressure condition by installing a valve for pressure adjustment in the suction unit  6 . 
     The sizes of the above-described conveying unit  2 , mixing unit  3 , chamber portion  4 , stacking portion  5 , and suction unit  6  are adjusted in accordance with the size of an absorbent body for evaluation that is to be produced, and an absorbent body that has uniform distribution of the absorbent fibers and the water-absorbent resin can be produced in the plane direction. The size of the absorbent body that can be produced is determined by the size of the recessed portion  531  of the stacking portion  5 , and the size of the absorbent body is preferably in a range of 15 cm×10 cm to 80 cm×30 cm, and more preferably in a range of 20 cm×10 cm to 60 cm×20 cm. An absorbent body having a size of 15 cm×10 cm or less is too small to serve as the absorbent body for evaluation, the amount of liquid that can not be absorbed and leaks becomes too high, and a difference in evaluation is unlikely to occur, and there is no demand for it to be used in a testing method. Moreover, if an absorbent body having a size of 80 cm×30 cm or more is used, it is difficult to uniformly distribute such an absorbent body in the short axis direction of the absorbent body due to the mechanism of the apparatus, and thus such an absorbent body is not preferable as the absorbent body for evaluation. 
     Note that it is preferable that a breathable sheet member such as tissue paper is disposed on the above-described air circulation member  52 , and the absorbent body is stacked thereon. 
     3. Operation of Manufacturing Apparatus 
     Next, operations of the manufacturing apparatus that has been constituted as described above will be described. First, a highly breathable sheet member (for example, tissue or nonwoven fabric) (not shown) is disposed on the air circulation member  52  of the stacking portion  5 . This is for preventing the stacked absorbent fibers and water-absorbent resin from coming off of pores of the air circulation member  52 . Note that when the power source of the suction apparatus is turned on, it is confirmed that the above-described sheet member is not misaligned. Next, a material body  100  is prepared. As described above, the material body  100  has various modes, but as shown in  FIG. 1  as one example, an aggregate  101  of the absorbent fibers formed into an approximately rectangular shape is disposed on the conveying belt  23  of the conveying unit  2 , and a water-absorbent resin  102  is dispersively disposed thereon uniformly to the left and the right with respect to the direction in which the belt advances. However, the aggregate  101  of the absorbent fibers may have various shapes other than an approximately rectangular shape as described above. 
     Next, after the second motor  32  and the suction apparatus are driven, the first motor is driven. Accordingly, the material body  100  on the conveying belt  23  moves leftward and is guided to the mixing unit  3  while being pressed by the pressing member  71 . Because the cylindrical body  31  of the mixing unit  3  rotates at a high speed, the material body  100  introduced into the mixing unit  3  enters the gap while being cut off in sequence. At this time, the material body  100  moves counterclockwise in the gap due to rotation of the cylindrical body  31 . Also, recesses and protrusions are formed on the outer circumferential surface of the cylindrical body  31 , and thus crushed absorbent fibers and water-absorbent resin are mixed while the material body  100  is rubbed between the cover member  332  and the cylindrical body  31 . Then, the material body  100  is further rubbed between the mesh member  333  and the cylindrical body  31  after passing through the cover member  332 . That is, the material body  100  is crushed due to shearing between the recesses and protrusions of the cylindrical body  31  and the recesses and protrusions of the mesh member  333 , and the absorbent fibers and the water-absorbent resin are further mixed. Upon reaching the lower portion of the cylindrical body  31 , the absorbent fibers and the water-absorbent resin that were mixed fall downward from the pores of the mesh member  333 , assisted by suction performed by the suction unit  6 . Note that the absorbent fibers and the water-absorbent resin that do not fall here are mixed while further moving through the gap and being rubbed by the cylindrical body  31  and eventually fall from the mesh member  333 . 
     Then, the absorbent fibers and the water-absorbent resin that fell from the mesh member  333  are stacked in the recessed portion  531  formed by the frame member  53  of the stacking portion  5  while falling through the internal space  40  of the chamber portion  4 . In the process in which the absorbent fibers and the water-absorbent resin fall, the absorbent fibers and the water-absorbent resin are uniformly stacked in the recessed portion  531  by the above-described three guide members  44  to  46 . 
     In this manner, the absorbent fibers and the water-absorbent resin are mixed in the recessed portion  531 , and an absorbent body stacked in a predetermined weight per area is formed. Thereafter, after the motors and the suction apparatus are turned off, when the stacking portion  5  is drawn to the front, the absorbent body can be removed from the apparatus. 
     4. Features 
     As described above, according to the present embodiment, the material body  100  is gradually introduced into the mixing unit having the cylindrical body  31  that rotates at a high speed, and thus the material body  100  is cut off little by little and introduced into the gap due to the rotation of the cylindrical body  31 . Then, the material body  100  introduced into the gap is rubbed between the cylindrical body  31  having recesses and protrusions and the cover member  332  and between the cylindrical body  31  and the mesh member  333 , and is mixed while receiving a shearing force. Thereafter, the absorbent fibers and the water-absorbent resin that were mixed fall and are stacked uniformly in the recessed portion  531 . As a result, it is possible to obtain an absorbent body in which the absorbent fibers and the water-absorbent resin are mixed uniformly and have a uniform thickness. Therefore, similarly to a commercial production line, the apparatus for manufacturing an absorbent body according to the present embodiment, which is a small apparatus, can manufacture an absorbent body in which the absorbent fibers and the water-absorbent resin are uniformly mixed. That is, an absorbent body can be easily manufactured similarly to a commercial production line without using a commercial production line, and thus various types of testing of a water absorption property or the like can be performed using the absorbent body according to the present embodiment. 
     Also, the material body  100  is mainly manually produced, and at this time, the blending amount of the absorbent fibers and the water-absorbent resin can be modified as appropriate, and even though such modification is made, a uniformly mixed absorbent body can be manufactured using the above-described apparatus. Thus, the blending amount of the absorbent fibers and the water-absorbent resin can be easily changed in accordance with the evaluation content, and thus an absorbent body for testing having a desired formulation can be easily manufactured. 
     5. Variation 
     Although the embodiment of the present invention was described above, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. Note that variations below can be combined as appropriate. 
     (5-1) 
     There is no particular limitation on the length of the mesh member  333  in the circumferential direction of the cylindrical body  31 , and the mesh member  333  need only be disposed to cover the upper opening of the chamber portion  4  so as to connect at least the chamber portion  4  and the gap. However, when the mesh member  333  extends longer toward the downstream side than the upper opening of the chamber portion  4 , the shearing effect with the cylindrical body  31  increases, which can further facilitate mixing of the absorbent fibers and the water-absorbent resin. 
     Also, in the above-described embodiment, the mesh member  333  has the role of applying a shearing force to the material body  100  between the cylindrical body  31  and the mesh member  333 , and the role of connecting the gap and the chamber portion  4 , but these roles can be separated from each other. That is, a member (a mixing portion) provided with recesses and protrusions that can apply a shearing force to the material body  100  between the cylindrical body  31  and the mixing portion may be disposed, and a member (a connection portion) that connects the gap and the chamber portion  4  may also be disposed separately from the mixing portion. Also, the recesses and protrusions may be formed in the cover member  332 . 
     Also, in the above-described embodiment, in the gap through which the material body  100  passes, first, the material body  100  passes between the cover member  332  and the cylindrical body  31 , then, the material body  100  passes between the mesh member  333  and the cylindrical body  31 , and the absorbent fibers and the water-absorbent resin fall from through holes on the downstream side of the mesh member  333 . That is, the material body  100  passes through the gap in which recesses and protrusions are provided on one surface and then passes through the gap in which recesses and protrusions are provided on both surfaces, and thereafter, the absorbent fibers and the water-absorbent resin fall. There is no particular limitation on the configuration of such a gap, and recesses and protrusions may be formed on both surfaces, across the entire gap. Also, it is possible to change positions as appropriate, such as the material body first passing through a site at which recesses and protrusions are formed on both surfaces, or mixing sites at which recesses and protrusions are formed on both surfaces and sites at which recesses and protrusions are formed on one surface. 
     (5-2) 
     Although there is no particular limitation on the shape of the chamber portion  4 , when the shape of the absorbent body  10  that is manufactured is larger than the upper opening of the chamber portion  4 , the chamber portion  4  has a shape that widens toward the bottom as described above. Also, the guide members  44  to  46  of the chamber portion  4  need only to be provided as needed such that the absorbent fibers and the water-absorbent resin are uniformly stacked, and are not necessarily required. Also, the number and the shape of guide members can be changed as appropriate. 
     (5-3) 
     There is no particular limitation on the configuration of the conveying unit  2 , and the conveying unit  2  may have a configuration other than the belt conveyor as described above and need only to guide the material body  100  to the mixing unit  3 . 
     Working Example 
     Hereinafter, working examples of the present invention will be described. However, the present invention is not limited to the working examples below. 
     A. Specification of Manufacturing Apparatus 
     First, the manufacturing apparatus described in the above-described embodiment was prepared as a working example. A specific specification is as follows.
     (1) Conveying unit   

     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                 (i) Conveying speed 
                 1.6 (mm/sec) 
               
               
                   
               
            
           
         
       
         
         (2) Cylindrical body 
       
    
     
       
         
           
               
               
               
             
               
                   
               
             
            
               
                   
                 (i) Size 
                 φ70 mm × 200 mm 
               
               
                   
                 (ii) Rotation speed 
                 2700 rotations/min 
               
               
                   
                 (iii) Height of protrusions 
                 4 mm 
               
               
                   
               
            
           
         
       
         
         (3) Gap formation portion
       (i) Gap between cover member and cylindrical body 2 mm   (ii) Gap between mesh member and cylindrical body 1 mm   (iii) Position of mesh member Below cylindrical body over central angle of approximately 90 degrees   
     
         (4) Chamber portion 
       
    
     
       
         
           
               
               
               
               
             
               
                   
               
             
            
               
                   
                 (i) Opening width of upper end 
                 63 
                 mm 
               
               
                   
                 (ii) Opening width of lower end 
                 380 
                 mm 
               
               
                   
                 (iii) Height 
                 440 
                 mm 
               
               
                   
               
            
           
         
       
         
         (5) Stacking portion
       (i) Size of recessed portion in frame member width 120 mm×length 400 mm   
     
         (6) Suction portion
       (i) A vacuum cleaner that operates at 100 V was used as the suction apparatus   
     
       
    
     B. Manufacture of Absorbent Body 
     First, the apparatus was prepared by placing tissue paper (width 140 mm×length 420 mm) having a basis weight of 16 g/m 2  on the stacking portion, such that absorbent fibers and water-absorbent resin were stacked thereon. Next, 10 g of absorbent fibers were molded as an aggregate having a shape with a width of 125 mm and a length of 450 mm, and 10 g of water-absorbent resin was uniformly dispersed manually thereon to form a material body. Leif lock produced by Leonia Co., Ltd. was used as the absorbent fibers and AQUA KEEP SA55SXII produced by SUMITOMO SEIKA CHEMICALS CO., LTD. was used as the water-absorbent resin. Next, that material body was disposed on the conveying unit of the above-described manufacturing apparatus, and all of the motors and the suction apparatus were driven. The entire material body was introduced into the mixing unit, and thereafter, when the absorbent fibers and the water-absorbent resin that were mixed were stacked in the stacking portion, an absorbent body shown in  FIG. 4  was obtained. 
     C. Evaluation of Absorbent Body
     (1) Evaluation of External Appearance   

     The external appearance was evaluated using an absorbent body obtained by using a water-absorbent resin that was colored red in advance so as to be easily visually recognizable in the manufacture of the above-described absorbent body. As shown in  FIG. 4 , it is found that the absorbent fibers and the water-absorbent resin are uniformly mixed in that absorbent body (white portions in  FIG. 4  indicate absorbent fibers and grey portions indicate water-absorbent resin). That is, as shown in  FIG. 4( a ) , the water-absorbent resin is uniformly distributed in the plane direction, and as shown in  FIG. 4( b ) , it is uniformly distributed in the thickness direction as well.
     2. Evaluation of distribution state of absorbent fibers and water-absorbent resin using water absorption test   (2-1) Water absorption test of the absorbent body was conducted in accordance with procedures below.   (i) As shown in  FIG. 5 , the obtained absorbent body was divided into three in the longitudinal direction and the lateral direction, that is, it was divided into nine to produce absorbent pieces, and a weight C (g) of each piece was measured.   (ii) The absorbent pieces were immersed in 8 L of an ion exchange water, and left for 30 minutes. (The ion exchange water was stirred for 10 seconds immediately after the immersion so as to spread the pieces.)   (iii) The absorbent pieces that were spread in the ion exchange water were filtered using a standard sieve (having a diameter of 20 cm and a sieve opening of 75 μm) that was weighted in advance, and water was drained with the standard sieve tilted for 30 minutes.   (iv) The weight of the absorbent pieces together with the standard sieve was measured, and a weight D (g) of the absorbent pieces that absorbed water was obtained.   (v) The content of the water-absorbent resin in each absorbent piece was calculated using the following equations using an ion exchange water absorption capacity A (g/g) of the water-absorbent resin and an ion exchange water absorption capacity B (g/g) of the absorbent fibers that were calculated as shown in (2-2) and (2-3) below.   

     When the weight of the water-absorbent resin is X (g) and the weight of the absorbent fibers is Y (g), Equations (1) and (2) below are true.
 
 X+Y=C   (1)
 
 AX+BY=D   (2)
 
     X and Y can be calculated using these Equations (1) and (2) as described below.
 
 X =( D−BC )/( A−B )
 
 Y=C−X  
 
     (2-2) Ion exchange water absorption capacity (g/g) of water-absorbent resin
     (i) 1000 ml of the ion exchange water was introduced into a beaker.   (ii) 0.5 g of the water-absorbent resin were added to the ion exchange water in the beaker and left for 30 minutes.   (iii) The water-absorbent resin that absorbed water was transferred to a standard sieve that was weighted in advance, and water was drained with the standard sieve tilted for 30 minutes.   (iv) The weight (m) of the water-absorbent resin on the standard sieve was measured, and the ion exchange water absorption capacity A (g/g) of the water-absorbent resin was obtained using Equation (3) below.
 
 A ( g/g )= m ( g )/0.5( g )  (3)
   

     (2-3) Ion exchange water absorption capacity (g/g) of absorbent fibers
     (i) 1000 ml of the ion exchange water was introduced into a beaker.   (ii) 1.0 g of the absorbent fibers was added to the ion exchange water in the beaker.   (iii) The beaker was left for 30 minutes.   (iv) The absorbent fibers that absorbed water were transferred to a standard sieve that was weighted in advance, and water was drained with the standard sieve tilted for 30 minutes.   (v) The weight (m) of the absorbent fibers on the standard sieve was measured, and the measured weight (m) was denoted as the ion exchange water absorption capacity B (g/g) of the absorbent fibers.   

     3. Result of Water Absorption Test 
     First, two absorbent bodies (Samples No. 1 and 2) were manufactured using the manufacturing apparatus according to the working example, and the total weight (g) of each absorbent body was measured. Separately, the ion exchange water absorption capacity A of the water-absorbent resin that was used to produce the absorbent bodies and the ion exchange water absorption capacity B (g/g) of the absorbent fibers that was used to produce the absorbent bodies were measured and calculated. The results are as shown below.
         The ion exchange water absorption capacity A of the water-absorbent resin=355.3 (g/g)   The ion exchange water absorption capacity B of the absorbent fibers=15.0 (g/g)   The total weight of Sample No. 1 absorbent body=19.85 (g)   The total weight of Sample No. 2 absorbent body=19.67 (g)       

     Then, the content of the absorbent fibers and the content of the water-absorbent resin of each absorbent piece obtained from each sample were calculated using A, B, and C, which were measured before the water absorption test, and D, which was obtained by water absorption test. Also, the average value of the absorbent fiber amounts and the water-absorbent resin amounts that were obtained using the absorbent pieces obtained from the samples was obtained, and deviations from the average value were also obtained. The results are as shown in  FIG. 6 . According to  FIG. 6 , it is found that in all of the samples, the nine absorbent pieces had approximately the same amount of the absorbent fibers and the water-absorbent resin. Therefore, it was found that use of the manufacturing apparatus according to the present working example made it possible to manufacture an absorbent body in which the absorbent fibers and the water-absorbent resin were approximately uniformly dispersed in the plane direction. In general, the dispersiveness of the water-absorbent resin in the long axis direction is unlikely to be uniform, but it was found that as described above, use of the manufacturing apparatus according to the present working example made it possible to make the dispersiveness in both directions, that is, in the long axis direction and the short axis direction, approximately the same. 
     Also, if the manufacturing apparatus according to the present working example is used, the absorbent body can be manufactured using about 10 g of the water-absorbent resin, and the water-absorbent resin can be evaluated in the state of the absorbent body. That is, even if the amount of the water-absorbent resin is not sufficient to be used in manufacture in an actual plant, if there are several tens of grams of the water-absorbent resin or several hundreds of grams of the water-absorbent resin that can be manufactured in the laboratory, use of the manufacturing apparatus according to the present working example makes it possible to evaluate the water-absorbent resin as the absorbent body. 
     D. Evaluation Test of Absorbent Body in Which Water-Absorbent Resin is Used 
     Next, an evaluation test of the absorbent body produced in the above-described working example was performed. Specifically, an evaluation test shown below was performed using artificial urine. 
     1. Preparation of Artificial Urine 
     An appropriate amount of distilled water was introduced into a 10 L container, and 60 g of sodium chloride, 1.8 g of calcium chloride dihydrate, and 3.6 g of magnesium chloride hexahydrate were added and dissolved. Next, 0.15 g of polyoxyethylene nonyl phenyl ether was added and distilled water was further added so as to make the overall mass 6000 g. Furthermore, the mixture was colored with a small amount of blue No. 1 to prepare artificial urine. 
     2. Production of Absorbent Body and Absorbent Article 
     A sheet-shaped absorbent body having a size of length 40 cm×width 12 cm was produced using 10 g of the water-absorbent resin and 10 g of crushed pulp (produced by Leonia Co., Ltd., Leif lock) serving as the absorbent fibers, in conformity with the above-described working example “Manufacture of absorbent body”. Next, approximately 0.6 g of water was spread over the entire obtained absorbent body using a vaporizer. Thereafter, an absorbent body for evaluation was produced by placing tissue paper having the same size as the absorbent body and having a basis weight of 16 g/m 2  on this absorbent body, and pressing the absorbent body while applying a load of 196 kPa to the entire absorbent body for 30 seconds. Further, polyethylene-polypropylene air-through type porous liquid permeable sheet having the same size as the absorbent body for evaluation and having a basis weight of 22 g/m 2  was disposed on an upper surface of the absorbent body for evaluation. Also, an absorbent article was prepared by disposing a polyethylene liquid impermeable sheet having the same size and the same basis weight as polyethylene-polypropylene air-through type porous liquid permeable sheet on a lower surface of the absorbent body for evaluation and sandwiching the absorbent body for evaluation therebetween. 
     3. Evaluation Test 
     Next, the evaluation test below was performed using the above-described absorbent article. 
     (3-1) Permeation time of absorbent article 
     The absorbent article was placed on a horizontal table, and a measurement instrument provided with a cylinder for liquid injection having an inner diameter of 3 cm was placed in a central portion of the absorbent article. Then, 50 mL of the artificial urine was introduced into the cylinder at once, and the amount of time until the artificial urine completely disappeared from the cylinder was measured using a stopwatch and the measured amount of time was denoted as a first permeation time (sec). Next, the cylinder was removed and the absorbent article was stored as it was, a similar operation was performed using the measurement instrument at the same position as in the first artificial urine injection 30 minutes and 60 minutes after the start of the first artificial urine injection, and a second permeation time (sec) and a third permeation time (sec) were measured. Then, the total time of the first to third injection was denoted as the total permeation time. It can be said that the shorter the permeation time is, the more preferable the sample is as the absorbent article. 
     (3-2) Return Amount 
     120 minutes after the start of the first test liquid injection in the measurement of the above-described permeation time, about 80 filter papers having 10 cm×10 cm whose mass (Wd(g)) was measured in advance were placed near an artificial urine injection position on the absorbent article, and a weight having a mass of 5 kg and whose bottom surface had a size of 10 cm×10 cm was placed thereon. After a load was applied for 5 minutes, the mass (We (g)) of the filter papers was measured and an increased mass was denoted as a return amount (g) as the equation below. Note that it can be said that the smaller the return amount is, the more preferable the sample is as the absorbent article.
 
Return amount( g )= We−Wd  
 
     (3-3) Diffusion Length 
     A spreading dimension (cm) in the longitudinal direction of the absorbent article through which the artificial urine permeated was measured within 5 minutes after the measurement of the above-described return amount. Because a diffusion distance in the lateral direction of both ends of the liquid that spread from the central portion in which the artificial urine was introduced in the longitudinal direction varied, the maximum length of the distance by which the blue artificial urine spread in the longitudinal direction was measured as the diffusion length and the numerical values after the decimal points were rounded off. 
     Working Example 2 was the case where AQUA KEEP SA55SXII, whose water absorption capacity was 55-fold and that was produced by SUMITOMO SEIKA CHEMICALS CO., LTD., was used as the water-absorbent resin, and Working Example 3 was the case where AQUA KEEP SA60SXII, whose water absorption capacity was 60-fold, was used. The results are as follows. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                   
                   
                   
                 Return 
                 Diffusion 
               
               
                   
                 Water-absorbent 
                 Permeation time (sec) 
                 amount 
                 length 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 resin 
                 first 
                 second 
                 third 
                 Total 
                 (g) 
                 (cm) 
               
               
                   
               
               
                 Work. 
                 SA55SXII 
                 19 
                 16 
                 24 
                 59 
                 30.5 
                 19 
               
               
                 Ex. 2 
                   
                   
                   
                   
                   
                   
                   
               
               
                 Work. 
                 SA60SXII 
                 19 
                 18 
                 27 
                 64 
                 27.4 
                 18 
               
               
                 Ex. 3 
               
               
                   
               
            
           
         
       
     
     Accordingly, it is understood that the return amount was lower when the type with the type with the 60-fold absorption capacity was used, and the permeation time was shorter when the type with the 55-fold absorption capacity was used. 
     LIST OF REFERENCE NUMERALS 
       2 : Conveying unit 
       3 : Mixing unit 
       4 : Chamber portion 
       5 : Stacking portion 
       6 : Suction unit 
       10 : Absorbent body 
       31 : Cylindrical body 
       33 : Gap formation portion 
       333 : Mesh member (plate-shaped member) 
       40 : Internal space 
       52 : Air circulation member 
       53 : Frame member 
       100 : Material body 
       101 : Absorbent fiber 
       102 : Water-absorbent resin 
       531 : Recessed portion