# Patent

## Title
Manufacturing method of water absorbing material

## Abstract

A water absorbing material includes a granular core portion and a coating layer portion. The coating layer portion covers the granular core portion. The coating layer portion contains fluff pulp and a water-absorbent polymer. These fluff pulp and water-absorbent polymer are both derived from a sanitary article.

## Background
CROSS REFERENCE TO RELATED APPLICATION
This is a Continuation of International Application No. PCT/JP2013/063179 filed May 10, 2013. The contents of this application are hereby incorporated by reference in their entirety.


TECHNICAL FIELD
The present invention relates to a water absorbing material that absorbs liquid such as excrement of humans or animals, and a manufacturing method of the water absorbing material.
BACKGROUND ART
Patent Document 1 describes an excrement treatment material that is a type of water absorbing material. In this excrement treatment material, a core portion and a surface layer portion that covers the core portion are provided. The surface layer portion has a function of causing the excrement treatment materials, which absorbed liquid such as urine in use, to adhere to each other so as to form an aggregate.

    Patent Document 1: JP2006-333773A


SUMMARY OF INVENTION
Technical Problem
The surface layer portion contains preferably an adhesive material in addition to a water-absorbent material in order to have the function of making an aggregate. Thus, a water absorbing material which is excellent both in the function of absorbing water and in the function of making an aggregate is obtained. However, if the surface layer portion contains both the water-absorbent material and the adhesive material, it causes increase of procuring cost of raw materials and eventually increase of manufacturing cost of the water absorbing material.
Solution to Problem
The present invention was made in view of the above-described problems, and it is an object thereof to provide a water absorbing material which is excellent in the function of absorbing water and in the function of making an aggregate, and which can be manufactured at low cost, and a manufacturing method of the water absorbing material.
A water absorbing material according to the present invention includes a core portion and a surface layer portion that covers the core portion, wherein the surface layer portion contains fluff pulp and a water-absorbent polymer that are derived from a sanitary article.
In this water absorbing material, the surface layer portion contains fluff pulp and a water-absorbent polymer. The fluff pulp functions as a water-absorbent material, and the water-absorbent polymer functions as an adhesive material. These fluff pulp and water-absorbent polymer are both derived from a sanitary article (disposable diaper, sanitary napkin, urine absorbing pad, and so forth). Here, being derived from a sanitary article refers to being produced in classification or manufacture of the sanitary article.
Thus, it becomes possible to use fluff pulp and a water-absorbent material that are separated from a waste sanitary article as raw materials of the surface layer portion. Also, it becomes possible to use fluff pulp and a water-absorbent material that are residues generated in manufacture of a sanitary article as raw materials of the surface layer portion. Accordingly, it is possible to reduce procuring cost of raw materials and eventually reduce manufacturing cost of the water absorbing material.
A manufacturing method of a water absorbing material including a core portion and a surface layer portion that covers the core portion according to the present invention includes an obtaining step of obtaining fluff pulp and a water-absorbent polymer that are derived from a sanitary article, and a forming step of forming the surface layer portion using the fluff pulp and the water-absorbent polymer obtained in the obtaining step as raw materials.
In this manufacturing method, fluff pulp and a water-absorbent polymer that are derived from a sanitary article are used as raw materials of the surface layer portion. Thus, it becomes possible to use fluff pulp and a water-absorbent material that are separated from a waste sanitary article as raw materials of the surface layer portion. Also, it becomes possible to use fluff pulp and a water-absorbent material that are residues generated in manufacture of a sanitary article as raw materials of the surface layer portion. Accordingly, it is possible to reduce procuring cost of raw materials and eventually reduce manufacturing cost of the water absorbing material.
Advantageous Effects of Invention
According to the present invention, a water absorbing material which is excellent in the function of absorbing water and in the function of making an aggregate, and which can be manufactured at low cost, and a manufacturing method of the water absorbing material are realized.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a schematic view of an embodiment of a water absorbing material according to the present invention.
FIG. 2 is a configuration diagram showing an embodiment of a separation device according to the present invention.
FIG. 3 is a side view showing a separation unit 40 of the separation device in FIG. 2.
FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3.
FIG. 5 is a side view showing a separation unit 60 of the separation device in FIG. 2.
FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5.
FIG. 7 is a cross-sectional view showing a transfer path 76 of the separation device in FIG. 2.
FIG. 8 is a cross-sectional view showing a transfer path 78 of the separation device in FIG. 2.
FIG. 9 is a cross-sectional view showing a transfer path 80 of the separation device in FIG. 2.
FIG. 10 is a cross-sectional view for explaining a modification of a ridge 44 shown in FIG. 4.
FIG. 11 is a cross-sectional view for explaining a modification of an uneven surface 77a and an uneven surface 77b shown in FIG. 7.
FIG. 12 is a cross-sectional view for explaining a modification of the uneven surface 77a and the uneven surface 77b shown in FIG. 7.



DESCRIPTION OF EMBODIMENTS
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the description of the drawings denotes like elements by like reference numerals and omits redundant descriptions.
FIG. 1 is a schematic view of an embodiment of a water absorbing material according to the present invention. A water absorbing material 1 is an excrement treatment material for a pet animal such as cat and dog, and includes a granular core portion 10 (core portion) and a coating layer portion 20 (surface layer portion).
The coating layer portion 20 covers the granular core portion 10. The coating layer portion 20 may cover the entire surface of the granular core portion 10, or may cover only a part of the surface of the granular core portion 10. The coating layer portion 20 contains fluff pulp and a water-absorbent polymer (including a highly water-absorbent polymer; the same shall apply hereinafter). These fluff pulp and water-absorbent polymer are both derived from a sanitary article. The sanitary article is, for example, disposable diaper, sanitary napkin, or urine absorbing pad. A waste sanitary article is preferably used as the sanitary article. In the present embodiment, the fluff pulp and the water-absorbent polymer are separated from the sanitary article with a separation device mentioned later.
The fluff pulp is contained in the coating layer portion 20 as a main material, and the water-absorbent polymer is contained in the coating layer portion 20 as a sub material. Here, the main material refers to the raw material whose weight ratio with respect to the coating layer portion 20 is the highest among all raw materials constituting the coating layer portion 20. The sub material refers to the raw material whose weight ratio with respect to the coating layer portion 20 is the second highest among all raw materials constituting the coating layer portion 20.
FIG. 2 is a configuration diagram showing a separation device used in the present embodiment. A separation device 90 processes a processing target containing a first material and a second material, thereby dissociating the first and second materials from each other and separating the second material from the processing target. In the present embodiment, the processing target is a sanitary article, the first material is plastic, and the second material is fluff pulp and a water-absorbent polymer. The separation device 90 includes a shredding unit 30 (first shredding unit), a separation unit 40 (first separation unit), a shredding unit 50 (second shredding unit), and a separation unit 60 (second separation unit).
The shredding unit 30 shreds the sanitary article. For example, a crusher or a grinder can be used as the shredding unit 30. In the case where the sanitary article is a disposable diaper, for example, it is preferable that no screen is provided in the shredding unit 30.
The structure of the separation unit 40 will be described with reference to FIGS. 3 and 4. FIG. 3 is a side view showing the separation unit 40. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 3. The separation unit 40 has a drum 42 (first tubular portion). The drum 42 has a substantially cylindrical tubular shape and is provided so as to be rotatable about its central axis. The central axis of the drum 42 extends horizontally. The inner diameter of the drum 42 may be between 30 cm and 50 cm inclusive, for example.
A large number of holes 42a (first holes) are formed in the drum 42. The holes 42a are formed over substantially the entire drum 42. The holes 42a do not allow plastic contained in the sanitary article shredded by the shredding unit 30 to pass through, but allow the fluff pulp and the water-absorbent polymer to pass through. In the case where the sanitary article is a disposable diaper, for example, it is preferable that the diameter of the holes 42a is between 10 mm and 30 mm inclusive. The separation unit 40 rotates the drum 42 in a state in which the sanitary article shredded by the shredding unit 30 is accommodated therein, thereby separating the fluff pulp and the water-absorbent polymer passing through the holes 42a from the sanitary article.
A ridge 44 (first ridge) is formed on an inner circumferential surface of the drum 42. The ridge 44 extends in a direction in which the central axis of the drum 42 extends. The ridge 44 extends over substantially the entire path from an inlet side (left side of FIG. 3) to an outlet side (right side of FIG. 3) of the drum 42. Also, the ridge 44 has a substantially triangular cross-sectional shape. The height (length in the radial direction of the drum 42) of the ridge 44 may be between 5 mm and 2 cm inclusive, for example. Preferably, “p” (p: an integer between 3 and 5 inclusive) ridges 44 are provided. The “p” ridges 44 are arranged on the inner circumferential surface of the drum 42 at regular intervals. That is so say, in a cross section (cross section shown in FIG. 4) that is perpendicular to the central axis of the drum 42, an angle α that is formed by a line connecting one ridge 44 to the central axis and a line connecting the next ridge 44 to the central axis is substantially equal to 360°/p. In the present embodiment, p=4 and α=90°.
A rotating rod 46 and a screw member 48 are provided inside the drum 42. The rotating rod 46 has a substantially cylindrical shape and is provided so as to be rotatable about its central axis. The central axis of the rotating rod 46 coincides with the central axis of the drum 42. However, the rotating rod 46 rotates independently of the drum 42. The outer diameter of the rotating rod 46 may be between 15 cm and 25 cm inclusive, for example.
The screw member 48 is helically provided around the rotating rod 46. The screw member 48 is fixed to the rotating rod 46 and rotates together with the rotating rod 46. A plurality of teeth 49 are formed in the screw member 48. An end portion of each tooth 49 is constituted by a side 49a and a side 49b in a front view (see FIG. 4).
The side 49a extends in the radial direction of the drum 42 and the rotating rod 46. An inner end (end that is closer to the rotating rod 46) of the side 49a is located at a position spaced apart from the rotating rod 46. Similarly, an outer end (end that is closer to the drum 42) of the side 49a is located at a position spaced apart from the drum 42. The distance from the outer end of the side 49a to the inner circumferential surface of the drum 42 is larger than the height of the ridge 44 and may be between 1 cm and 3 cm inclusive, for example. The side 49b connects the outer end of the side 49a to the inner end of the side 49a of the next tooth 49. The side 49b is longer than the side 49a. The ratio of the length of the side 49b to the length of the side 49a may be between 2 and 2.5 inclusive, for example.
The rotating rod 46 and the screw member 48 rotate in a left-handed direction (counterclockwise) in FIG. 4. That is to say, in each tooth 49, the side 49b is located on the forward side with respect to the rotation direction, and the side 49a is located on the rearward side with respect to the rotation direction. The rotation direction of the drum 42 described above may be the same as the rotation direction of the rotating rod 46 and the screw member 48 or may be opposite to this rotation direction. In the case where these rotation directions are the same, it is preferable that the rotation speed of the rotating rod 46 and the screw member 48 is greater than the rotation speed of the drum 42.
The shredding unit 50 shreds the sanitary article from which the fluff pulp and the water-absorbent polymer passing through the holes 42a have been separated by the separation unit 40. For example, a crusher or a grinder can be used as the shredding unit 50. A screen is provided in the shredding unit 50. In the case where the sanitary article is a disposable diaper, for example, it is preferable that the hole diameter of the screen is between 30 mm and 70 mm inclusive, for example.
The structure of the separation unit 60 will be described with reference to FIGS. 5 and 6. FIG. 5 is a side view showing the separation unit 60. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG. 5. The separation unit 60 has a drum 62 (second tubular portion). The drum 62 has a substantially cylindrical tubular shape and is provided so as to be rotatable about its central axis. The central axis of the drum 62 extends horizontally. The inner diameter of the drum 62 may be between 30 cm and 50 cm inclusive, for example.
A large number of holes 62a (second holes) are formed in the drum 62. The holes 62a are formed over substantially the entire drum 62. The holes 62a do not allow the plastic contained in the sanitary article shredded by the shredding unit 50 to pass through, but allow the fluff pulp and the water-absorbent polymer to pass through. The area of each of the holes 62a in a plan view is smaller than the area of each of the holes 42a in a plan view. In the case where the sanitary article is a disposable diaper, for example, it is preferable that the diameter of the holes 62a is between 5 mm and 20 mm inclusive. The separation unit 60 rotates the drum 62 in a state in which the sanitary article shredded by the shredding unit 50 is accommodated therein, thereby separating the fluff pulp and the water-absorbent polymer passing through the holes 62a from the sanitary article.
A ridge 64 (second ridge) is formed on an inner circumferential surface of the drum 62. The ridge 64 extends in a direction in which the central axis of the drum 62 extends. The ridge 64 extends over substantially the entire path from an inlet side (left side of FIG. 5) to an outlet side (right side of FIG. 5) of the drum 62. Also, the ridge 64 has a substantially triangular cross-sectional shape. The height (length in the radial direction of the drum 62) of the ridge 64 may be between 5 mm and 2 cm inclusive, for example. Preferably, “q” (q: an integer between 3 and 5 inclusive) ridges 64 are provided. The “q” ridges 64 are arranged on the inner circumferential surface of the drum 62 at regular intervals. That is to say, in a cross section (cross section shown in FIG. 6) that is perpendicular to the central axis of the drum 62, an angle β that is formed by a line connecting one ridge 64 to the central axis and a line connecting the next ridge 64 to the central axis is substantially equal to 360°/q. In the present embodiment, q=4 and β=90°.
A rotating rod 66 and a screw member 68 are provided inside the drum 62. The rotating rod 66 has a substantially cylindrical shape and is provided so as to be rotatable about its central axis. The central axis of the rotating rod 66 coincides with the central axis of the drum 62. However, the rotating rod 66 rotates independently of the drum 62. The outer diameter of the rotating rod 66 may be between 15 cm and 25 cm inclusive, for example.
The screw member 68 is helically provided around the rotating rod 66. The screw member 68 is fixed to the rotating rod 66 and rotates together with the rotating rod 66. A plurality of teeth 69 are formed in the screw member 68. An end portion of each tooth 69 is constituted by a side 69a and a side 69b in a front view (see FIG. 6).
The side 69a extends in the radial direction of the drum 62 and the rotating rod 66. An inner end (end that is closer to the rotating rod 66) of the side 69a is located at a position spaced apart from the rotating rod 66. Similarly, an outer end (end that is closer to the drum 62) of the side 69a is located at a position spaced apart from the drum 62. The distance from the outer end of the side 69a to the inner circumferential surface of the drum 62 is larger than the height of the ridge 64 and may be between 1 cm and 3 cm inclusive, for example. The side 69b connects the outer end of the side 69a to the inner end of the side 69a of the next tooth 69. The side 69b is longer than the side 69a. The ratio of the length of the side 69b to the length of the side 69a may be between 2 and 2.5 inclusive, for example.
The rotating rod 66 and the screw member 68 rotate in a left-handed direction (counterclockwise) in FIG. 6. That is to say, in each tooth 69, the side 69b is located on the forward side with respect to the rotation direction, and the side 69a is located on the rearward side with respect to the rotation direction. The rotation direction of the drum 62 described above may be the same as the rotation direction of the rotating rod 66 and the screw member 68 or may be opposite to this rotation direction. In the case where these rotation directions are the same, it is preferable that the rotation speed of the rotating rod 66 and the screw member 68 is greater than the rotation speed of the drum 62.
The separation device 90 is further provided with a transfer path 76, a transfer path 78, and a transfer path 80 (see FIG. 2). The transfer path 76 is a duct (first air pipe) and transfers the sanitary article after shredding by the shredding unit 30 to the separation unit 40 with air pressure. The transfer path 78 is a duct (second air pipe) and transfers the sanitary article after separation by the separation unit 40 to the shredding unit 50 with air pressure. The transfer path 80 is a duct (third air pipe) and transfers the sanitary article after shredding by the shredding unit 50 to the separation unit 60.
The structure of the transfer path 76 will be described with reference to FIG. 7. FIG. 7 is a cross-sectional view showing the transfer path 76. The transfer path 76 has a portion 76a (first portion) extending in a first direction, a portion 76b (second portion) extending in a second direction, and a portion 76c (third portion) extending in a third direction. In the present embodiment, the first direction is a horizontal direction, the second direction is a vertical direction, and the third direction is a horizontal direction. The portion 76b is connected to the portion 76a on a downstream side of the portion 76a. The portion 76c is connected to the portion 76b on the downstream side of the portion 76b. Thus, the portion 76a, the portion 76b, and the portion 76c constitute a single cranked duct. The inner diameter of the transfer path 76 may be between 10 cm and 20 cm inclusive, for example.
An uneven surface 77a (first uneven surface) is present in a connecting portion between the portion 76a and the portion 76b. The uneven surface 77a is provided at a position where the sanitary article that is transferred through the portion 76a collides with this uneven surface. The uneven surface 77a is at an angle of about 45° to a vertical plane. For example, a corrugated or embossed plate-like member can be used as the uneven surface 77a. The material for the uneven surface 77a may be aluminum, for example.
An uneven surface 77b (second uneven surface) is present in a connecting portion between the portion 76b and the portion 76c. The uneven surface 77b is provided at a position where the sanitary article that is transferred through the portion 76b collides with this uneven surface. The uneven surface 77b is at an angle of about 45° to a horizontal plane. For example, a corrugated or embossed plate-like member can be used as the uneven surface 77b. The material for the uneven surface 77b may be aluminum, for example.
The structure of the transfer path 78 will be described with reference to FIG. 8. FIG. 8 is a cross-sectional view showing the transfer path 78. The transfer path 78 has a portion 78a (first portion) extending in a first direction, a portion 78b (second portion) extending in a second direction, and a portion 78c (third portion) extending in a third direction. In the present embodiment, the first direction is a horizontal direction, the second direction is a vertical direction, and the third direction is a horizontal direction. The portion 78b is connected to the portion 78a on the downstream side of the portion 78a. The portion 78c is connected to the portion 78b on the downstream side of the portion 78b. Thus, the portion 78a, the portion 78b, and the portion 78c constitute a single cranked duct. The inner diameter of the transfer path 78 may be between 10 cm and 20 cm inclusive, for example.
An uneven surface 79a (third uneven surface) is present in a connecting portion between the portion 78a and the portion 78b. The uneven surface 79a is provided at a position where the sanitary article that is transferred through the portion 78a collides with this uneven surface. The uneven surface 79a is at an angle of about 45° to a vertical plane. For example, a corrugated or embossed plate-like member can be used as the uneven surface 79a. The material for the uneven surface 79a may be aluminum, for example.
An uneven surface 79b (fourth uneven surface) is present in a connecting portion between the portion 78b and the portion 78c. The uneven surface 79b is provided at a position where the sanitary article that is transferred through the portion 78b collides with this uneven surface. The uneven surface 79b is at an angle of about 45° to a horizontal plane. For example, a corrugated or embossed plate-like member can be used as the uneven surface 79b. The material for the uneven surface 79b may be aluminum, for example.
The structure of the transfer path 80 will be described with reference to FIG. 9. FIG. 9 is a cross-sectional view showing the transfer path 80. The transfer path 80 has a portion 80a (first portion) extending in a first direction, a portion 80b (second portion) extending in a second direction, and a portion 80c (third portion) extending in a third direction. In the present embodiment, the first direction is a horizontal direction, the second direction is a vertical direction, and the third direction is a horizontal direction. The portion 80b is connected to the portion 80a on the downstream side of the portion 80a. The portion 80c is connected to the portion 80b on the downstream side of the portion 80b. Thus, the portion 80a, the portion 80b, and the portion 80c constitute a single cranked duct. The inner diameter of the transfer path 80 may be between 10 cm and 20 cm inclusive, for example.
An uneven surface 81a (fifth uneven surface) is present in a connecting portion between the portion 80a and the portion 80b. The uneven surface 81a is provided at a position where the sanitary article that is transferred through the portion 80a collides with this uneven surface. The uneven surface 81a is at an angle of about 45° to a vertical plane. For example, a corrugated or embossed plate-like member can be used as the uneven surface 81a. The material for the uneven surface 81a may be aluminum, for example.
An uneven surface 81b (sixth uneven surface) is present in a connecting portion between the portion 80b and the portion 80c. The uneven surface 81b is provided at a position where the sanitary article that is transferred through the portion 80b collides with this uneven surface. The uneven surface 81b is at an angle of about 45° to a horizontal plane. For example, a corrugated or embossed plate-like member can be used as the uneven surface 81b. The material for the uneven surface 81b may be aluminum, for example.
The operation of the separation device 90 will be described. A sanitary article, which is a processing target, is first shredded by the shredding unit 30. The sanitary article shredded by the shredding unit 30 is transferred to the separation unit 40 through the transfer path 76. The sanitary article transferred to the separation unit 40 is propelled from the inlet side (left side of FIG, 3) to the outlet side (right side of FIG. 3) of the drum 42 by the rotating screw member 48. Meanwhile, due to the centrifugal force and the like generated by the rotation of the drum 42, the fluff pulp and the water-absorbent polymer dissociated from the plastic are discharged to the outside of the drum 42 through the holes 42a. Thus, a portion of the fluff pulp and a portion of the water-absorbent polymer are separated from the sanitary article, and they can be used as raw materials of the coating layer portion 20.
The sanitary article after separation by the separation unit 40 is transferred to the shredding unit 50 through the transfer path 78 and is further shredded. The sanitary article shredded by the shredding unit 50 is transferred to the separation unit 60 through the transfer path 80. The sanitary article transferred to the separation unit 60 is propelled from the inlet side (left side of FIG. 5) to the outlet side (right side of FIG. 5) of the drum 62 by the rotating screw member 68. Meanwhile, due to the centrifugal force and the like generated by the rotation of the drum 62, the fluff pulp and the water-absorbent polymer dissociated from the plastic are discharged to the outside of the drum 62 through the holes 62a. Thus, the remaining fluff pulp and water-absorbent polymer are separated from the sanitary article, and they also can be used as raw materials of the coating layer portion 20.
An example of a manufacturing method of the water absorbing material 1 will be described as an embodiment of a manufacturing method of a water absorbing material according to the present invention. This manufacturing method includes an obtaining step, a fluff pulverizing step, a polymer pulverizing step, a granulating step, a coating step (forming step), a classification step, and a drying step.
The obtaining step is a step of obtaining fluff pulp and a water-absorbent polymer that are derived from a sanitary article. In the present embodiment, these materials are obtained by being separated from the sanitary article.
In the obtaining step, the separation device 90 described above is used. That is, in the obtaining step, a sanitary article is first shredded by the shredding unit 30 (first shredding step). Next, the drum 42 is rotated in a state in which the sanitary article shredded by the shredding unit 30 is accommodated therein, and thereby the fluff pulp and the water-absorbent polymer passing through the holes 42a are separated from the sanitary article in the separation unit 40 (first separating step).
After that, the sanitary article from which the fluff pulp and the water-absorbent polymer are separated in the first separating step is further shredded by the shredding unit 50 (second shredding step). Next, the drum 62 is rotated in a state in which the sanitary article shredded by the shredding unit 50 is accommodated therein, and thereby the fluff pulp and the water-absorbent polymer passing through the holes 62a are separated from the sanitary article in the separation unit 60 (second separating step).
The fluff pulverizing step is a step of pulverizing the fluff pulp obtained in the obtaining step with a grinder that has a screen a hole diameter of which is 0.5 mm or less (preferably 0.3 mm or less). The polymer pulverizing step is a step of pulverizing the water-absorbent polymer obtained in the obtaining step such that the water-absorbent polymer has a grain size of 50 μm or less (preferably 25 μm or less). It should be noted that the fluff pulverizing step and the polymer pulverizing step may be omitted. The granulating step is a step of forming the granular core portion 10. In this step, a core portion material (material that constitutes the granular core portion 10) is subjected to extrusion granulation using a granulator after adding water thereto. As the core portion material, for example, papers, fibers, woods, plants, plastics, rubbers, or organic sludge can be used. They may be used in combination of two or more. Thus, the granular core portion 10 is formed.
The coating step is a step of forming the coating layer portion 20. In this step, a coating material (material that constitutes the coating layer portion 20) is stuck to the surface of the granular core portion 10 using a coating device and the like. Sticking of the coating material may be performed by, for example, sprinkling or spraying. Thus, the coating layer portion 20 is formed.
The coating material contains the fluff pulp pulverized in the fluff pulverizing step and the water-absorbent polymer pulverized in the polymer pulverizing step. Fluff pulp and a water-absorbent polymer used in the coating material may be those obtained in either of the first separating step or the second separating step, or may be those obtained in both of the first and second separating steps. The coating material may consist only of the fluff pulp and the water-absorbent polymer, or may consist of a mixture of these materials and other materials.
In the classification step, only the water absorbing materials that meet a predetermined standard are obtained by sifting the water absorbing materials manufactured in the preceding step with a sieve having a predetermined mesh size.
In the drying step, the water absorbing materials obtained in the preceding step are dried by a dryer. By appropriately adjusting the moisture content of the granular core portion 10, it is possible to prevent degradation of water absorbing performance caused by movement of water from the granular core portion 10 to the coating layer portion 20, and to prevent the growth of mold and the like during storage of the water absorbing material 1. Accordingly, the water absorbing material 1 is obtained.
The effects of the present embodiment will be described. In the present embodiment, the coating layer portion 20 contains fluff pulp and a water-absorbent polymer. The fluff pulp functions as a water-absorbent material, and the water-absorbent polymer functions as an adhesive material. These fluff pulp and water-absorbent polymer are both produced in classification of a sanitary article.
Thus, it becomes possible to use fluff pulp and a water-absorbent material that are separated from a waste sanitary article as raw materials of the coating layer portion 20. Accordingly, it is possible to reduce procuring cost of raw materials and eventually reduce manufacturing cost of the water absorbing material 1. Consequently, the water absorbing material 1 which is excellent in the function of absorbing water and in the function of making an aggregate, and which can be manufactured at low cost, and the manufacturing method thereof are realized.
In particular, the fluff pulp and the water-absorbent material are contained in the coating layer portion 20 as, respectively, the main material and the sub material. Thus, the effect of reducing procuring cost of raw materials is remarkably exhibited.
In the present embodiment, after shredding by the shredding unit 30 and separation by the separation unit 40, shredding by the shredding unit 50 and separation by the separation unit 60 are performed. Therefore, the separation efficiency is improved when compared with the case where shredding and separation are performed only one time. Here, the separation efficiency refers to the ratio of the weight of the second material that is separated from the processing target to the weight of the second material that is contained in the processing target immediately before the processing.
The drum 42 is provided with the ridges 44. If the ridges 44 are not provided, the sanitary article tends to collect in a lower portion of the drum 42 due to the effect of gravity. In contrast, in the present embodiment, the sanitary article in the drum 42 is scooped up by the ridges 44 and thus easily reaches an upper portion of the drum 42. Therefore, the sanitary article is distributed over a wide range of the inner circumferential surface of the drum 42, so that separation by the separation unit 40 is promoted. Moreover, dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted by the impact of the sanitary article when falling down from the upper portion of the drum 42. Furthermore, the ridges 44 become obstacles when the sanitary article is propelled by the screw member 48, and thus the time for which the sanitary article stays in the drum 42 is prolonged. Thus, a larger amount of fluff pulp and water-absorbent material can be separated from the sanitary article.
The screw member 48 is provided inside the drum 42. The sanitary article in the drum 42 is beaten and rubbed against the inner circumferential surface of the drum 42 by the screw member 48. The impact and the frictional force at that time promote dissociation of the fluff pulp and the water-absorbent material from the plastic. Moreover, since the ridges 44 are provided, the sanitary article may be beaten and rubbed against the inner circumferential surface of the drum 42 by the screw member 48 in a state in which the sanitary article is caught on the ridges 44. In that case, forces are focused, so that the impact and the frictional force that are applied to the sanitary article increase, and accordingly dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted even more.
The screw member 48 rotates with the side 49b that forms an obtuse angle with the rotation direction (direction of the tangent to the rotating rod 46), rather than the side 49a that forms an approximately right angle with the rotation direction, being located on the forward side (see FIG. 4). Thus, the sanitary article can be prevented from being excessively caught on the teeth 49 of the screw member 48.
The drum 62 is provided with the ridges 64. If the ridges 64 are not provided, the sanitary article tends to collect in a lower portion of the drum 62 due to the effect of gravity. In contrast, in the present embodiment, the sanitary article in the drum 62 is scooped up by the ridges 64 and thus easily reaches an upper portion of the drum 62. Therefore, the sanitary article is distributed over a wide range of the inner circumferential surface of the drum 62, so that separation by the separation unit 60 is promoted. Moreover, dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted by the impact of the sanitary article when falling down from the upper portion of the drum 62. Furthermore, the ridges 64 become obstacles when the sanitary article is propelled by the screw member 68, and thus the time for which the sanitary article stays in the drum 62 is prolonged. Thus, a larger amount of fluff pulp and water-absorbent material can be separated from the sanitary article.
The screw member 68 is provided inside the drum 62. The sanitary article in the drum 62 is beaten and rubbed against the inner circumferential surface of the drum 62 by the screw member 68. The impact and the frictional force at that time promote dissociation of the fluff pulp and the water-absorbent material from the plastic. Moreover, since the ridges 64 are provided, the sanitary article may be beaten and rubbed against the inner circumferential surface of the drum 62 by the screw member 68 in a state in which the sanitary article is caught on the ridges 64. In that case, forces are focused, so that the impact and the frictional force that are applied to the sanitary article increase, and accordingly dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted even more.
The screw member 68 rotates with the side 69b that forms an obtuse angle with the rotation direction (direction of the tangent to the rotating rod 66), rather than the side 69a that forms an approximately right angle with the rotation direction, being located on the forward side (see FIG. 6). Thus, the sanitary article can be prevented from being excessively caught on the teeth 69 of the screw member 68.
The transfer path 76 has the portion 76a and the portion 76b that are orthogonal to each other (see FIG. 7). Thus, the sanitary article transferred by air pressure collides with the inner surface of the transfer path 76 in the connecting portion between the portion 76a and the portion 76b. The impact of this collision promotes dissociation of the fluff pulp and the water-absorbent material from the plastic. Furthermore, the transfer path 76 has the portion 76c that is orthogonal to the portion 76b. Thus, the sanitary article transferred by air pressure also collides with the inner surface of the transfer path 76 in the connecting portion between the portion 76b and the portion 76c. The impact of this collision promotes dissociation of the fluff pulp and the water-absorbent material from the plastic.
The uneven surface 77a is present in the connecting portion between the portion 76a and the portion 76b. When colliding with the uneven surface 77a, the sanitary article is subjected to a stronger impact than in the case where it collides with a flat surface. Therefore, dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted even more. Furthermore, the uneven surface 77b is present in the connecting portion between the portion 76b and the portion 76c. When colliding with the uneven surface 77b, the sanitary article is subjected to a stronger impact than in the case where it collides with a flat surface. Therefore, dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted even more.
The transfer path 78 has the portion 78a and the portion 78b that are orthogonal to each other (see FIG. 8). Thus, the sanitary article transferred by air pressure collides with the inner surface of the transfer path 78 in the connecting portion between the portion 78a and the portion 78b. The impact of this collision promotes dissociation of the fluff pulp and the water-absorbent material from the plastic. Furthermore, the transfer path 78 has the portion 78c that is orthogonal to the portion 78b. Thus, the sanitary article transferred by air pressure also collides with the inner surface of the transfer path 78 in the connecting portion between the portion 78b and the portion 78c. The impact of this collision promotes dissociation of the fluff pulp and the water-absorbent material from the plastic.
The uneven surface 79a is present in the connecting portion between the portion 78a and the portion 78b. When colliding with the uneven surface 79a, the sanitary article is subjected to a stronger impact than in the case where it collides with a flat surface. Therefore, dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted even more. Furthermore, the uneven surface 79b is present in the connecting portion between the portion 78b and the portion 78c. When colliding with the uneven surface 79b, the sanitary article is subjected to a stronger impact than in the case where it collides with a flat surface. Therefore, dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted even more.
The transfer path 80 has the portion 80a and the portion 80b that are orthogonal to each other (see FIG. 9). Thus, the sanitary article transferred by air pressure collides with the inner surface of the transfer path 80 in the connecting portion between the portion 80a and the portion 80b. The impact of this collision promotes dissociation of the fluff pulp and the water-absorbent material from the plastic. Furthermore, the transfer path 80 has the portion 80c that is orthogonal to the portion 80b. Thus, the sanitary article transferred by air pressure also collides with the inner surface of the transfer path 80 in the connecting portion between the portion 80b and the portion 80c. The impact of this collision promotes dissociation of the fluff pulp and the water-absorbent material from the plastic.
The uneven surface 81a is present in the connecting portion between the portion 80a and the portion 80b. When colliding with the uneven surface 81a, the sanitary article is subjected to a stronger impact than in the case where it collides with a flat surface. Therefore, dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted even more. Furthermore, the uneven surface 81b is present in the connecting portion between the portion 80b and the portion 80c. When colliding with the uneven surface 81b, the sanitary article is subjected to a stronger impact than in the case where it collides with a flat surface. Therefore, dissociation of the fluff pulp and the water-absorbent material from the plastic is promoted even more.
The water absorbing material and the manufacturing method thereof according to the present invention are not limited to the foregoing embodiments, and various modifications can be made thereto. For example, in the foregoing embodiments, an example in which fluff pulp and a water-absorbent material derived from a sanitary article are contained in the coating layer portion 20 as, respectively, the main material and the sub material has been described. However, the fluff pulp is not necessarily contained as the main material and the water-absorbent material is not necessarily contained as the sub material as long as they are contained in the coating layer portion 20.
In the foregoing embodiments, an example in which shredding and separation are performed two times has been described. However, it is also possible that shredding and separation are performed only one time, or three times or more.
In the foregoing embodiments, an example in which the drum 42 has a cylindrical tubular shape has been described. However, it is also possible that the drum 42 has a tapered shape. The same applies to the drum 62.
In the foregoing embodiments, an example in which the central axis of the drum 42 extends horizontally has been described. However, it is also possible that the central axis of the drum 42 is sloped downward from the inlet side toward the outlet side. The same applies to the drum 62.
In the foregoing embodiments, an example in which the holes 42a are formed over substantially the entire drum 42 has been described. However, it is also possible that the holes 42a are formed in only a portion of the drum 42. Moreover, it is also possible that the holes 42a are formed by forming substantially the whole or a portion of the drum 42 in a mesh form. That is to say, in this case, the meshes of the drum 42 correspond to the holes 42a. The same applies to the holes 62a. 
In the foregoing embodiments, an example in which the ridges 44 extend over the entire path from the inlet side to the outlet side of the drum 42 has been described. However, it is also possible that the ridges 44 extend in only a portion of the path from the inlet side to the outlet side of the drum 42. The same applies to the ridges 64.
In the foregoing embodiments, the ridges 44 having a substantially triangular cross-sectional shape have been described as an example. However, it is also possible that the ridges 44 have a flat plate-like shape as shown in FIG. 10. The same applies to the ridges 64.
In the foregoing embodiments, an example in which four ridges 44 are provided on the inner circumferential surface of the drum 42 has been described. However, the number of ridges 44 can be set at any number greater than or equal to 1. The same applies to the ridges 64.
In the foregoing embodiments, an example in which the ridges 44 are provided on the inner circumferential surface of the drum 42 has been described. However, the provision of the ridges 44 is not necessarily required. The same applies to the ridges 64.
In the foregoing embodiments, an example in which the rotating rod 46 and the screw member 48 are provided inside the drum 42 has been described. However, the provision of the rotating rod 46 and the screw member 48 is not necessarily required. The same applies to the rotating rod 66 and the screw member 68.
In the foregoing embodiments, an example in which the uneven surface 77a is at a certain angle to a vertical plane has been described. However, it is also possible that the uneven surface 77a extends along a vertical plane as shown in FIG. 11. Moreover, it is also possible that the uneven surface 77a is realized by providing a protrusion P1 on the inner surface (position with which the sanitary article transferred through the portion 76a collides) of the transfer path 76 as shown in FIG. 12. The number of protrusions P1 may be one or may be two or more. The same applies to the uneven surface 79a and the uneven surface 81a. 
In the foregoing embodiments, an example in which the uneven surface 77b is at a certain angle to a horizontal plane has been described.
However, it is also possible that the uneven surface 77b extends along a horizontal plane as shown in FIG. 11. Moreover, it is also possible that the uneven surface 77b is realized by providing a protrusion P2 on the inner surface (position with which the sanitary article transferred through the portion 76b collides) of the transfer path 76 as shown in FIG. 12. The number of protrusions P2 may be one or may be two or more. The same applies to the uneven surface 79b and the uneven surface 81b. 
In the foregoing embodiments, an example in which the uneven surface 77a is provided has been described. However, the provision of the uneven surface 77a is not necessarily required. The same applies to the uneven surface 79a and the uneven surface 81a. 
In the foregoing embodiments, an example in which the uneven surface 77b is provided has been described. However, the provision of the uneven surface 77b is not necessarily required. The same applies to the uneven surface 79b and the uneven surface 81b. 
In the foregoing embodiment, an example in which the transfer path 76 is constituted by a plurality of portions that are orthogonal to each other has been described (see FIG. 7). However, the transfer path 76 may be a straight line-shaped duct. The same applies to the transfer path 78 and the transfer path 80.
In the foregoing embodiment, an example in which the fluff pulp and the water-absorbent material are separated from the sanitary article by the separation device 90 has been described. However, separation of the fluff pulp and the water-absorbent material from the sanitary article may be performed by other devices or methods.
In the foregoing embodiment, an example in which the fluff pulp and the water-absorbent polymer that are produced in classification of the sanitary article are used as raw materials of the coating layer portion 20 has been described. However, as the fluff pulp and the water-absorbent polymer, those produced in manufacture of the sanitary article may be used. Furthermore, a water-absorbent polymer that is separated from the fluff pulp produced in manufacture of the sanitary article may be used as raw materials of the coating layer portion 20. In this case, the water-absorbent polymer adheres to the fluff pulp, and the weight ratio of the water-absorbent polymer adhering to the fluff pulp with respect to the fluff pulp is preferably 3% or less.
In the foregoing embodiment, an example in which the water absorbing material is a granular excrement treatment material has been described. However, a water absorbing material according to the present invention may be a pet sheet, water stop material, water absorbing sheet, and so forth.
LIST OF REFERENCE NUMERALS


    1 Water absorbing material
    10 Granular core portion
    20 Coating layer portion
    30 Shredding unit (first shredding unit)
    40 Separation unit (first separation unit)
    42 Drum (first tubular portion)
    42a Hole (first hole)
    44 Ridge (first ridge)
    46 Rotating rod
    48 Screw member
    49 Tooth
    50 Shredding unit (second shredding unit)
    60 Separation unit (second separation unit)
    62 Drum (second tubular portion)
    62a Hole (second hole)
    64 Ridge (second ridge)
    66 Rotating rod
    68 Screw member
    69 Tooth
    76 Transfer path (first air pipe)
    77a Uneven surface (first uneven surface)
    77b Uneven surface (second uneven surface)
    78 Transfer path (second air pipe)
    79a Uneven surface (third uneven surface)
    79b Uneven surface (fourth uneven surface)
    80 Transfer path (third air pipe)
    81a Uneven surface (fifth uneven surface)
    81b Uneven surface (sixth uneven surface)
    90 Separation device

## Claims

1. A manufacturing method of a water absorbing material including a core portion and a surface layer portion that covers the core portion comprising:
an obtaining step of obtaining fluff pulp and a water-absorbent polymer that are derived from a sanitary article; and
a forming step of forming the surface layer portion using the fluff pulp and the water-absorbent polymer obtained in the obtaining step as raw materials,
wherein in the obtaining step, the fluff pulp and the water-absorbent polymer are separated from the sanitary article with a separation device,
the separation device including:
a first shredding unit that shreds the sanitary article; and
a first separation unit that has a first tubular portion in which a large number of first holes that allow the fluff pulp and the water-absorbent polymer to pass through without allowing plastic contained in the sanitary article shredded by the first shredding unit to pass through are formed, and that separates the fluff pulp and the water-absorbent polymer passing through the first holes from the sanitary article by rotating the first tubular portion in a state in which the sanitary article shredded by the first shredding unit is accommodated in the first tubular portion, and
an inside of the first tubular portion being provided with a rotating rod that has a central axis coinciding with a central axis of the first tubular portion and is rotatable about the central axis of the first tubular portion, and a screw member that is helically provided around the rotating rod and has a plurality of teeth formed in the screw member.

2. The manufacturing method of the water absorbing material according to claim 1,
wherein the separation device includes a first ridge that is provided on an inner circumferential surface of the first tubular portion and that extends in a direction in which the central axis of the first tubular portion extends.

3. The manufacturing method of the water absorbing material according to claim 2,
wherein “p” of said first ridges are present, “p” being an integer between 3 and 5 inclusive, and the “p” first ridges are arranged on the inner circumferential surface of the first tubular portion at regular intervals.

4. The manufacturing method of the water absorbing material according to claim 1,
wherein the separation device includes a first air pipe for transferring the sanitary article shredded by the first shredding unit to the first separation unit with air pressure, and
the first air pipe has a first portion that extends in a first direction and a second portion that is connected to the first portion on a downstream side of the first portion and that extends in a second direction substantially orthogonal to the first direction.

5. The manufacturing method of the water absorbing material according to claim 4,
wherein the separation device includes a first uneven surface that is present in a connecting portion between the first portion and the second portion of the first air pipe and with which the sanitary article transferred through the first portion collides.

6. The manufacturing method of the water absorbing material according to claim 4,
wherein the first air pipe has a third portion that is connected to the second portion on a downstream side of the second portion and that extends in a third direction substantially orthogonal to the second direction.

7. The manufacturing method of the water absorbing material according to claim 6,
wherein the separation device includes a second uneven surface that is present in a connecting portion between the second portion and the third portion of the first air pipe and with which the sanitary article transferred through the second portion collides.

8. The manufacturing method of the water absorbing material according to claim 1,
wherein the separation device includes:
a second shredding unit that shreds the sanitary article from which the fluff pulp and the water-absorbent polymer passing through the first holes are separated by the first separation unit; and
a second separation unit that has a second tubular portion in which a large number of second holes that allow the fluff pulp and the water-absorbent polymer to pass through without allowing the plastic contained in the sanitary article shredded by the second shredding unit to pass through are formed, and that separates the fluff pulp and the water-absorbent polymer passing through the second holes from the sanitary article by rotating the second tubular portion in a state in which the sanitary article shredded by the second shredding unit is accommodated in the second tubular portion.

9. The manufacturing method of the water absorbing material according to claim 8,
wherein an area of each of the second holes in a plan view is smaller than an area of each of the first holes in a plan view.