Patent Publication Number: US-2010108287-A1

Title: Structure for cooling

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is related to a Japanese patent application: Japanese Patent Early-publication No. 2007-289594, published on Nov. 8, 2007. 
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     The present invention relates to a structure having a water-retentive member for cooling human or animal bodies. 
     2. Background Art 
     Absorptive substances that can be used as a disposable diaper and the like usually comprise a liquid-permeable sheet, a liquid-impermeable sheet, and a water-absorptive material, which may be placed between the liquid-permeable sheet and the liquid-impermeable sheet. The water-absorptive material may comprise fibrous base materials such as a nonwoven fabric and water-absorptive resins or highly water-absorptive polymers held to the fibrous base materials. Paper may also be used with the water-absorptive material. 
     Japanese Patent Early-publication No. 2004-358797 discloses a liner for incontinence. This liner includes (1) a water-absorptive composite sheet comprising a water-absorptive sheet containing a fibrous base material and water-absorptive resin particles attached to the fibrous base material and a fibrous base sheet, and that is mounted on at least one side of the water-absorptive sheet, (2) a nonwoven fabric, and (3) a polyethylene sheet. The water-absorptive composite sheet is put between the nonwoven fabric and the polyethylene sheet. This reference discloses that the water-absorptive composite sheet is a highly effective water absorbing material that can absorb large amount of liquids such as urine at high speed. 
     Japanese Patent Early-publication No. 2001-286505 discloses an absorptive substance having a liquid-permeable sheet, a liquid-impermeable sheet, and an absorptive material having liquid-retentive property disposed between these two sheets. The absorptive material contains a first absorptive layer having highly water-absorptive polymers held between nonwoven fabric fibers and a second absorptive layer having aggregates of hydrophilic fibers. The first absorptive layer faces the liquid-permeable sheet and the second absorptive layer faces the liquid-impermeable sheet. This reference, thus, discloses a substance that can prevent liquids, e.g., urine, from moving back. 
     The water-absorptive resin or the highly water-absorptive polymer has been used in cooling materials with water in gelatinous state. 
     Japanese Patent Early-publication No. 2005-118059 discloses a cooling material having a cooling agent that contains a cooling medium. The cooling medium may be a gelatinous substance of a water-absorptive resin containing the resin and water or a water/solvent mixture. The cooling medium is placed in a sealed container made of a water-permeable and water-insoluble base material. At least part of the outer surface of the cooling material is made of a wrapping material that is made of a fibrous and/or plastic three-dimensional structure with air-permeability of at least 200 cm 3 /cm 2 /second (Fragile method). This reference discloses that this material has its cooling effect due to latent heat of water vaporization. 
     Japanese Utility Model Early-publication No. 2001-104359 discloses a cooling sheet that contains aqueous gel applied on one side of a water-absorptive nonwoven fabric sheet made of fibrous water-absorptive resins and/or water-retentive fibers. The cooling effect of this sheet is due to heat of water vaporization. This reference also discloses that water is sprayed onto the surface of the water-absorptive nonwoven fabric when the cooling sheet is prepared. 
     Examples of conventional cooling substances/sheets as described above use latent heat of water vaporization or heat of gasification of water to achieve the cooling effect. However, after water vaporization ceases, the cooling effect is no longer available. 
     The Mie Chemical Co., Ltd. (http://miekagaku.co.jp/sp04.html) discloses a cooling substance containing highly water-absorptive polymers. The cooling substance is soaked in water to absorb the water and then frozen before use. 
     Among inventions that use cooling effects due to latent heat of vaporization of water, the following ones are also known. 
     Japanese Patent Early-publication No. HEI. 11-28034 discloses a cooler mat for pets having (1) a pouch-like member, which comprises water-absorptive polymers placed into a wrapping (pouch-like structure) having a sheet made of an air-permeable material on its first side and another sheet made of a synthetic resin on its second side, and (2) an outer wrapping, which is made of an air-permeable material, for storing the pouch-like member. In this cooler mat, the pouch-like member is soaked in water before use. The water, that has been held by the water-absorptive polymer vaporizes, goes out as a vapor through the sheet made of the air-permeable material on the first side of the pouch-like member and through the outer wrapping material that stores the pouch-like member. The latent heat of vaporization of water results in cooling effects. 
     The cooler mat in the above reference (Japanese Patent Early-publication No. HEI. 11-28034) has problems. The first problem is that the cooling efficiency is not controlled, and the second one is that the outer wrapping, which is made of an air-permeable material, e.g., a nonwoven fabric, may become damp by the water vapor coming from the water-absorptive polymers. These problems should be solved before the device is used in human. 
     Japanese Patent Early-publication No. 2001-120095 discloses a cooler mat for pets. This cooler mat contains a water-permeable pouch-like member in which water-absorptive polymers are placed; and a bag for storing the pouch-like member. In addition, the water-permeable pouch-like member has many polymer-stuffed areas, the peripheries of which are heat-sealed. The water-permeable pouch-like member is soaked in water before use. The bag can be made of an air-permeable material on one side and a water-repellency material on the other side. Alternatively, the bag can be made of water-repellent materials as the inner layer and fabric as the outer layer. Thus, the water vapor from the water-permeable pouch-like member can go out through the bag causing a cooling effect by heat of water vaporization. However, the control of the cooling efficiency is not considered in this device. Additionally, the part of the bag made of the air-permeable material may become damp by the water vapor from the water-permeable pouch-like member. Again, there are problems that need to be solved before human use. In the case that the outside of the bag does not become damp by the water vapor from the water-permeable pouch-like member, the bag may be saturated by the water vapor, resulting in limited cooling effects. 
     SUMMARY OF INVENTION 
     Embodiments of the present invention relate to structures for cooling. These structures may enable controlled cooling efficiency by using latent heat of water vaporization (or heat of gasification of water). By replenishing water, such a structure for cooling may be used repeatedly for a long time. Specifically, embodiments of the present invention relate to structures for cooling, in which the outer surface of each structure cover is less likely to become damp by the moisture coming from a water-holding substance disposed inside the structures. The present invention also relates to structures for cooling that may eliminate or minimize fungal contamination. 
     The first aspect of the invention relates to structures for cooling. A structure for cooling in accordance with one embodiment of the invention may have a cover and a water-retentive member. The water-retentive member may comprises a bag and a water-absorptive material disposed inside the bag. The water-retentive member may be removed from the cover. Referring to FIG.  3 ( 1 ), a first side a of the cover may have an outer fibrous layer and an inner air-permeable sheet layer partially bonded together. The first side a of the cover may have a moisture-permeability of 500 to 3,000 g/m 2 ·24 hours, as determined by the Lyssy Method. The first side I of the bag may be made of a moisture- or water-permeable material. At least one of the second side b of the cover (i.e., the opposite side of the first side of the cover) and the second side II of the bag (i.e., the opposite side of the first side of the bag) is water-impermeable. 
     In one example of embodiments of the invention, the air-permeable sheet layer may be an air-impermeable polymer film having openings, e.g., a porous film that is moisture-permeable. 
     In another example of embodiments of the invention, the first side I of the bag may be made of a fibrous material, preferably a nonwoven fabric. 
     In another example of the first embodiment of the invention, the water-absorptive material may be (1) a water-absorptive sheet(s) with a water-absorptive polymer, or (2) a water-absorptive sheet(s) with a water-absorptive polymer and a water-absorptive sheet(s) without a water-absorptive polymer. 
     In another example of embodiments of the invention, the water-impermeable second side b of the cover (i.e., the opposite side of the first side of the cover) may contain an outer fibrous layer and an inner air-impermeable sheet layer partially or completely bonded together. 
     In another example of embodiments of the invention, the water-impermeable second side II of the bag (i.e., the opposite side of the first side of the bag) may contain a nonwoven fabric and an air-impermeable sheet layer partially or completely (preferably completely) bonded together. The air-impermeable sheet layer may be disposed on the outside or the inside of the nonwoven fabric, and preferably on the outside of the nonwoven fabric. 
     In another example of embodiments of the invention, the water-retentive member, preferably the water-absorptive polymer, may contain an antifungal agent. 
     Another aspect of the invention relates to a structure for cooling. The structure may have a cover and a water-retentive member. The water-retentive member may have a bag and a water-absorptive material disposed inside the bag. The water-retentive member may be removed from the cover. Referring to  FIG. 3 , the first side a of the cover may have an outer fibrous layer and an inner air-permeable sheet layer partially bonded together. The first side a of the cover may have a moisture-permeability of 500 to 3,000 g/m 2 ·24 hours, as determined by the Lyssy Method. The second side b of the cover (i.e., the opposite side of the first side of the cover) may contain an outer fibrous layer and an inner air-impermeable sheet layer partially or completely bonded together. The water-retentive member may contain a bag made of a nonwoven fabric and disposed inside the bag a water-absorptive sheet that may contain a water-absorptive polymer. 
     In accordance with embodiments of the invention, one example of a water-absorptive material containing a water-absorptive sheet(s) with a water-absorptive polymer and a water-absorptive sheet(s) without a water-absorptive polymer is as follows: Inside the bag of the water-retentive member, the water-absorptive sheet that is disposed as one of the outermost layers among water-absorptive sheet layers may have the water-absorptive polymer. The outer surface of one side of the bag, of which inner surface faces the water-absorptive sheet containing the water-absorptive polymer, faces the first side a of the cover. 
     In accordance with some embodiments of the invention, another example of a water-absorptive material having a water-absorptive sheet(s) with a water-absorptive polymer and a water-absorptive sheet(s) without a water-absorptive polymer is as follows: Inside the bag of the water-retentive member, the water-absorptive sheet, that is disposed next to (inside of) one of the outermost layers among water-absorptive sheet layers, may have the water-absorptive polymer. The outer surface of one side of the bag, of which inner surface faces the outermost water-absorptive sheet layer next to (outside of) the water-absorptive sheet containing the water-absorptive polymer, faces the first side a of the cover. 
     Another aspect of the invention also relates to a structure for cooling. The structure may contain a cover and a water-retentive member. The water-retentive member may have a bag and a water-absorptive polymer. The water-absorptive polymer may adhere to an inner surface(s) of at least one side of the bag or may be disposed in at least one side of the bag. The water-retentive member may be removed from the cover. The first side a of the cover comprises an outer fibrous layer and an inner air-permeable sheet layer partially bounded together. The first side a of the cover may have a moisture-permeability of 500 to 3,000 g/m 2 ·24 hours, as determined by the Lyssy Method. The first side I of the bag may contain a moisture- or water-permeable material. At least one of the second side b of the cover (i.e., the opposite side of the first side of the cover) and the second side II of the bag (i.e., the opposite side of the first side of the bag) may be water-impermeable. 
     In one example of one embodiment of the invention, the air-permeable sheet layer may be an air-impermeable polymer film having openings, e.g., a porous film that is moisture-permeable. 
     In another example of another embodiment of the invention, the first side I of the bag may be made of a fibrous material, preferably a nonwoven fabric. 
     In another example of another embodiment of the invention, the cooling structure may farther include water-absorptive material disposed inside the bag. The water-absorptive material may be preferably (1) a water-absorptive sheet(s) with a water-absorptive polymer, or (2) a water-absorptive sheet(s) with a water-absorptive polymer and a water-absorptive sheet(s) without a water-absorptive polymer. 
     In another example of another embodiment of the invention, the other water-impermeable second side b of the cover (i.e., the opposite side of the first side of the cover) may contain an outer fibrous layer and an inner air-impermeable sheet layer partially or completely bonded together. 
     In another example of one embodiment of the invention, the other water-impermeable second side II of the bag (i.e., the opposite side of the first side of the bag) may contain a fibrous material, preferably a nonwoven fabric, and an air-impermeable sheet layer partially or completely (preferably completely) bonded together. The air-impermeable sheet layer may be disposed outside the fibrous material. 
     In another example of another embodiment of the invention, the water-retentive member, preferably the water-absorptive polymer may contain an antifungal agent. 
     Another aspect of the invention relates to structures for cooling. A structure may contain a cover and a water-retentive member. The water-retentive member may be removed from the cover. The first side a of the cover may contain an outer fibrous layer and an inner air-permeable sheet layer partially bonded together. The first side a of the cover may have a moisture-permeability of 500 to 3,000 g/m 2 ·24 hours, as determined by the Lyssy Method. The second side b of the cover (i.e., the opposite side of the first side of the cover) may contain an outer fibrous layer and an inner air-impermeable sheet layer partially or completely bonded together. The water-retentive member may contain a bag made of a nonwoven fabric. The inner surface of at least one side of the bag may contain a water-absorptive polymer. 
     Other aspects and advantages of the invention will be apparent from the following description and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of the cover of one example of a structure in accordance with one embodiment of this invention, wherein the fastener of the cover is opened. 
         FIG. 2  is a schematic view of the same example of the cover of a structure in accordance with one embodiment of this invention, wherein the fastener of the cover is closed. 
       FIGS.  3 ( 1 )- 3 ( 4 ) show sectional views of examples of a cover in accordance with one embodiment of this invention. 
         FIG. 4  is a sectional view of one example of a water-retentive member in accordance with one embodiment of this invention. 
         FIG. 5  is a sectional view of another example of a water-retentive member in accordance with one embodiment of this invention. 
         FIG. 6  is a sectional view of another example of a water-retentive member in accordance with one embodiment of this invention. 
         FIG. 7  is a sectional view of another example of a water-retentive member in accordance with one embodiment of this invention. 
         FIG. 8  is a sectional view of another example of a water-retentive member in accordance with one embodiment of this invention. 
         FIG. 9  is a sectional view of one example of a structure in accordance with one embodiment of this invention. 
         FIG. 10  is a sectional view of one example of a water-absorptive sheet containing a water-absorptive polymer in accordance with one embodiment of the invention. 
         FIG. 11  shows surface temperature changes, as a function of time, of cooling structures in accordance with embodiments of the invention. 
         FIG. 12  shows results of cooling of various parts of users by cooling structures in accordance with embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the invention relate to structures having water-retentive members for cooling. In the following detailed description of the subject matter of the present invention, the cooling structures are principally described as being used for cooling human or animal bodies. For example, a structure for cooling according to one embodiment of the present invention may be used as a bed pad, a pad on a futon, or a rug for pets. Hereafter, the present invention will be explained with reference to preferred embodiments. Such examples or applications are intended for illustration purposes only and are not intended to limit the scope of the present invention. 
       FIGS. 1 and 2  are schematic views of a cover  100  of one example of a structure in accordance with one embodiment of this invention, wherein a fastener F of the cover  100  is opened ( FIG. 1 ) or closed ( FIG. 2 ).  FIG. 3  shows sectional views of examples of a first side a and a second side b of the cover  100 .  FIG. 9  also shows a sectional view of one example of the cover  100 . 
     Referring to  FIG. 1  and  FIG. 2 , the cover  100  has a fastener F that may be sewed in the peripheries of the cover  100 . By closing the fastener F, the cover  100  may exhibit a baggy form as shown in  FIG. 2 . The specific form of the cover 100 , though preferably baggy, is not restricted to the example shown as long as a water-retentive member (shown as  200  in  FIG. 4 ) may be put into and withdrawn from the cover  100 . 
     FIG.  3 ( 1 ) shows that the first side a of the cover  100  has a fibrous layer  1  at the outside and an air-permeable sheet layer  3  at the inside. The fibrous layer  1  may be partly bonded to the air-permeable sheet layer  3 . 
     The first side a of the cover  100  may have a moisture-permeability of 500 to 3,000 g/m 2 ·24 hours, preferably 700 to 2,000 g/m 2 ·24 hours, and more preferably 1,000 to 1,500 g/m 2 ·24 hours, as determined by the Lyssy Method (JIS Z0208; ASTM E398). The moisture-permeability may affect the amount of water vapor that passes through the first side a. The higher the moisture-permeability is, the higher the cooling effect would be due to a larger amount of water being vaporized. 
     If a structure for cooling according to the present invention is used for sleep in summer, it is preferable that the surface temperature of human body may be lowered by 1 to 2 degrees Celsius. If the structure is used for refrigeration in a medical care field, the surface temperature of human body may be lowered by about 4 degrees Celsius. In the latter case, the first side a (air-permeable side) of the cover  100  has a moisture-permeability of preferably 1,000 to 2,000 g/m 2 ·24 hours, and more preferably 1,400 to 1,800 g/m 2 ·24 hours, as determined by the Lyssy Method. 
     Determination of the moisture-permeability based on the Lyssy Method may be performed at 40 degrees Celsius under a humidity difference of about 90%. More specifically, in an example of the Lyssy Method, a test sample may be set between an atmosphere x having a relative humidity of 100% and an atmosphere y having a relative humidity of 9%, and a time required to achieve a relative humidity of 11% in the atmosphere y may be determined. Known moisture-permeability of standard samples are also determined. By comparing the data of the test sample to the data of the standard samples, the moisture-permeability of the test sample may be determined. 
     Moisture-permeability ranges described above are meant for averages of the useable portions of an article, while local areas or areas not intended to be in contact with a user may have moisture permeability outside of the desired range. For example, portions(s) of side a, e.g., four peripheries, may have a moisture-permeability outside of the above-mentioned range. In other word, the substantially whole part (e.g., parts where used for cooling) of the one side a of the cover  100  may have a moisture-permeability within the above range. 
     FIG.  3 ( 2 ) shows one embodiment of the invention, in which the second side b of the cover  100  may contain a fibrous layer  7  at the outside and an air-impermeable sheet layer  5  at the inside. In this example, the fibrous layer  7  is bonded to the air-impermeable sheet layer  5 . 
     FIG.  3 ( 3 ) shows another example of the second side b of the cover  100 . In this example, the second side b may contain an air-impermeable sheet layer  5  only. To prevent the transpiration of water that has been held by the water-retentive member through the cover  100 , the air-impermeable sheet layer  5  having a repellent or water-proofing property may be used. 
     Referring again to FIG.  3 ( 2 ), the fibrous layer  7  may be bonded completely or partly to the air-impermeable sheet layer  5 . It is preferable that they are completely bonded to each other. The bonding may be achieved by fusing the polymers in the fibrous layer  7  or the air-impermeable sheet layer  5 , or by using an adhesive or other suitable means. 
     FIG.  3 ( 4 ) shows, if the second side II of a bag of the water-retentive member (shown as  9  in  FIG. 4 ) is water-impermeable, the second side b of the cover  100  may be made of a water-permeable material such as fibrous materials  7 . 
     When a structure for cooling according to embodiments of the present invention is used, the first side a may be the top side (right side or usable side) and the second side b may be the bottom side (wrong side). For example, if the structure for cooling is a bed pad, the first side a would face human body and the second side b would face a mattress. 
     In the first embodiment of the invention, the water-retentive member may contain a bag and a water-absorptive material disposed inside the bag. The one side I of the bag may be made of a moisture or water-permeable material. The other side II of the bag may be made of a moisture or water-permeable material or a water-impermeable material. 
       FIG. 4  shows a sectional view of one example of a water-retentive member  200  of a structure according to one embodiment of the invention. The water-retentive member  200  may include a bag  9  made of a nonwoven fabric and a water-absorptive sheet  15  that may contain a water-absorptive polymer. The first side I and the second side II of the bag  9  may be made of a nonwoven fabric that is moisture or water-permeable. Alternatively, the first side I of the bag  9  may be made of a moisture or water permeable material  9   a , while the second side II of the bag  9  may be made of a moisture or water-impermeable material  9   b . The water-absorptive sheet  15  may contain a water-absorptive polymer or any water-absorptive material. The water-absorptive sheet  15  may preferably have an overall sheet configuration. However, other shapes or configurations may also be used without departing from the scope of the invention. 
     The water-retentive member  200  (shown in  FIG. 4 ) may be put into the cover  100  (shown in  FIG. 1  and  FIG. 2 ) so that the first side I ( 9   a ) of the bag  9  faces a side a (an air-permeable side) of the cover  100 , and the second side II ( 9   b ) faces the second side b of the cover  100 . 
       FIG. 10  shows an example of a water-absorptive sheet  15 , which may comprises a water-absorptive polymer  11  and a support sheet  13 . The water-absorptive polymer  11  may be disposed on (coated on, adhered to, etc.) one side of the support sheet  13 . When the water absorptive sheet  15  is put into the bag  9 , the water absorptive polymer preferably faces or touches the first side I ( 9   a ) of the bag  9  (see  FIG. 4 ). 
     Alternatively, a water-absorptive sheet  15  may comprise the water-absorptive polymer  11  compounded into the support sheet  13 , i.e., the polymer  11  may be mixed into the support sheet  13 . In this alternative embodiment, both sides of the water-absorptive sheet  15  will be similar. Thus, when the water-retentive member (shown as  200  in  FIG. 4 ) is put into the cover  100  (shown in  FIGS. 1 and 2 ), either the first side I ( 9   a ) or the second side II ( 9   b ) may face the first side a of the cover  100 . 
       FIG. 5  shows a sectional view of another example of a water-retentive member  300  of a structure for cooling according to one embodiment of the invention. The member  300  may comprise: (1) a bag  9  made of a nonwoven fabric, (2) a first water-absorptive sheet  15  containing a water-absorptive polymer  11  and a support sheet  13 , and (3) a second water-absorptive sheet  17  without a water-absorptive polymer. The first water absorptive sheet  15  and the second water-absorptive sheet  17  are placed inside the bag  9 . The bag  9  may contain a first side I ( 9   a ) and a second side II ( 9   b ), which may be made of a nonwoven fabric moisture- or water-permeable material. Among the water-absorptive sheets as water-absorptive materials, the water-absorptive sheet  15  may be set as the outermost layer that faces or touches the first side I ( 9   a ) of the bag  9 . 
     The water-retentive member  300  may be put into a cover (shown as  100  in  FIG. 1  and  FIG. 2 ) so that the first side I ( 9   a ) of the bag  9  made of a nonwoven fabric faces the first side a of the cover  100 . 
       FIG. 6  shows a sectional view of another example of a water-retentive member  400  of a structure for cooling according to one embodiment of the invention. In the water-retentive member  400 , a bag P is a modified version of bag  9  shown in  FIG. 4 . Bag P may be made of an air-impermeable sheet layer  19  bonded onto the inner surface of the second side II of the bag  9 . The first side I of the bag P may be made of a nonwoven fabric  9   a  that is a moisture- or water-permeable, while the second side II of the bag P may be water-impermeable and made of an air-impermeable sheet layer  19  and a nonwoven fabric  9   b . The air-impermeable sheet layer  19  may be partly or completely bonded onto the inner surface of the nonwoven fabric  9   b . The bonding may be achieved by fusing the polymer within the air-impermeable sheet layer  19  or the nonwoven fabric  9   b , or by using an adhesive or other suitable means. In the water-retentive member  400 , the air-impermeable sheet layer  19  may also be on the outer peripheries of the bag, namely, parts where the side  9   a  may be bonded to the side  9   b.    
     Because of the air-impermeable sheet layer  19 , the water that has been held by the water-absorptive materials, i.e., water-absorptive sheets  21 ,  23 , and  25 , and a water-absorptive sheet  15  that may contain a water-absorptive polymer, may be held within the water retentive member  400  without going out through the side II. 
     Inside the bag P, there may be water-absorptive sheets  21 ,  23 , and  25 , and a water-absorptive sheet  15  having a water-absorptive polymer  11 . In this case, the sheet  15  may be placed second to the outermost water-absorptive sheet  21 . Thus, the water held by the water-absorptive sheet  21  may be absorbed by the water-absorptive polymer  11  on the water-absorptive sheet  15 , ensuring a smooth transfer of water to the polymer  11 . 
     The water-retentive member  400  may be put into the cover (shown as  100  in  FIG. 1  and  FIG. 2 ) so that the side I of the bag P faces the side a of the cover  100 .  FIG. 4-6  show the examples wherein the water-absorptive sheets may not need to be fixed. However, the water-absorptive sheets may be fixed by placing the outer peripheries of the water-absorptive sheets between the first side I ( 9   a ) and the second side II ( 9   b ) in the outer peripheries of the bag  9  and by bonding the water-absorptive sheets to the first side I ( 9   a ) and the second side II ( 9   b ). 
       FIG. 9  shows a water-retentive member  700  of a structure for cooling in accordance with one embodiment of the invention. A first side I of the bag P may include entire nonwoven fabric  9   x , parts of a nonwoven fabric  9   y  (i.e., parts on or above the dotted lines that traverse the nonwoven fabric  9   y   1 , namely, parts  9   y   1  and  9   y   3 ), and parts of an air-impermeable sheet layer  19  (i.e., parts on or above the dotted lines that traverse the air-impermeable sheet layer  19 , namely, parts  19   y   1  and  19   y   3 ). The second side II of the bag P may include the residual part of the nonwoven fabric  9   y  (i.e., the part under the dotted lines that traverse the nonwoven fabric  9   y , namely, part  9   y   2 ) and the residual part of the air-impermeable sheet layer  19  (i.e., the part under the dotted lines that traverse the air-impermeable sheet layer  19 , namely, part  19   y   2 ). The air-impermeable sheet layer  19  may be bonded onto the outer surface of the nonwoven fabric  9   y , and may appear also in parts of the first side I. The air-impermeable sheet layer  19  may appear also in a part(s) of the first side I, provided that it does not prevent the release of water vapor from the first side I of the bag P. 
     In a structure for cooling according to another embodiment of the invention, a water-retentive member may contain a bag and a water-absorptive polymer, wherein the water absorptive polymer adheres to or is fused to an inner surface(s) of at least one side of the bag, or exists in at least one side of the bag. 
       FIG. 7  shows a sectional view of an example of a water-retentive member  500  of a structure for cooling according to another embodiment of the invention. The member  500  may contain a bag  31  made of a nonwoven fabric and a water-absorptive polymer  11 . The water-absorptive polymer  11  may adhere to inner surfaces of both sides I and II of the bag  31 . Alternatively, the water-absorptive polymer  11  may appear on an inner surface of only one side (side I or side II) of the bag  31 . Furthermore, the water-absorptive polymer  11  may be mixed in a nonwoven fabric  31   a  of the first side I and/or a nonwoven fabric  31   b  of the second side II. Alternatively, the side I and/or II each may be made of two sheets of nonwoven fabric, and a water-absorptive polymer may be placed between the two sheets. 
       FIG. 8  shows a sectional view of another example of a water-retentive member  600  of a structure for cooling according to another embodiment of the invention. The water-retentive member  600  may contain a bag Q and a water-absorptive sheet  17  placed inside the bag Q. Of the bag Q, one side I may be made of a nonwoven fabric. The other side II may be made of a nonwoven fabric  33   b , an air-impermeable sheet layer  19 , and a water-absorptive polymer  11 . The side II may be water impermeable and the polymer  11  may be bonded or fused to the inner surface of the nonwoven fabric  33   b . The nonwoven fabric  33   b  may be partly or completely (preferably completely) adhered to the air-impermeable sheet layer  19 . The adhesion may be achieved by fusing a polymer within the nonwoven fabric  33   b  or within the air-impermeable sheet layer  19 , or by using an adhesive. The water-absorptive sheet  17  placed inside the bag Q do not contain water-absorptive polymer, although a water-absorptive sheet with a water-absorptive polymer may also be used. Alternatively, both a water-absorptive sheet without water-absorptive polymer and a water-absorptive sheet with a water-absorptive polymer may be used together. 
     Each element that forms a part of a structure for cooling in accordance with embodiments of the present invention are described in the following section, together with examples. 
     The fibrous layer of the cover (see FIG.  3 ( 1 )) may be made of at least one material selected from the group consisting of a woven fabric, a nonwoven fabric, and a knit material, preferably a woven fabric (a cloth) or a nonwoven fabric. If the fibrous layer is made of a woven fabric, its raw material(s) may be selected from the group consisting of cotton, rayon, polyester, polypropylene, nylon, acrylic, and a combination thereof; and its thickness may be about 60 to 150 g/m 2 , preferably 80 to 130 g/m 2 , and more preferably 90 to 110 g/m 2 . For a fibrous layer used for the first side a (an air-permeable side) of the cover, an ultra high density woven fabric may be used instead of an usual woven fabric. In particular, the ultra high density woven fabric made of ultra microfiber in high density preferably has a moisture-permeability of 2,000 to 3,000 g/m 2 ·24 hours. 
     If the fibrous layer is made of a nonwoven fabric, its raw material(s) may be selected from the group consisting of rayon, nylon, polyester, acrylic, polypropylene, vinylon, polyethylene, urethane, cotton, cellulose, and a combination thereof; and its thickness may be bout 20 to 120 g/m 2 , preferably 30 to 100 g/m 2 , and more preferably 40 to 60 g/m 2 . 
     If the fibrous layer is made of a knit material, its raw materials) may be selected from the group consisting of rayon, polyester, polypropylene, nylon, acrylic, and a combination thereof; and its thickness may be about 80 to 150 g/m 2 , and preferably 90 to 120 g/m 2 . 
     The nonwoven fabric used for the fibrous layer may be, for example, a melt-blown nonwoven fabric, a spun-bonded nonwoven fabric, a spun-lace nonwoven fabric, or a spun-needle nonwoven fabric. In accordance with embodiments of the present invention, any suitable nonwoven fabric may be used. 
     The first side a (an air-permeable side) of the cover may contain an outer fibrous layer and an inner air-permeable sheet layer(see FIG.  3 ( 1 )). The two layers may be partly adhered to each other. The air-permeable sheet may be a film or sheet made of a polymer, through which air (also a water vapor) can pass. Examples of such film or sheet include a moisture-permeable porous film, e.g., an air-impermeable polymer film with air-permeable openings. The polymer film per se may be water repellent or water proof. The thickness of the moisture-permeable porous film used in the present invention may be around 100 μm or less, preferably 30 to 80 μm, and more preferably 50 to 70 μm. 
     A water proof, non-porous membrane through which water vapor can pass, thus, air-permeable, is known. One example of such a membrane is a polyester, moisture-permeable and water proof film ‘Flecron’ made by O. G. Film Co., Ltd. In accordance with embodiments of the invention, such membranes may also be used as an air-permeable sheet. Other examples of the polymer that may be used as a raw material for the air-permeable sheet include polyetylene, polypropylene, polyester, polyamide, poly(vinyl chloride), poly(vinilydene chlorise), polyurethane, polystyrene, ethylene-vinyl acetate copolymer, and polycarbonate. The air-permeable sheet may be a mono-layered or a multi-layered film. 
     The methods for preparing a porous film with an appropriate moisture-permeability are known. For example, the moisture-permeability of the first side a of the cover may be controlled to be 500 to 3,000 g/m 2 ·24 hours. This may be accomplished by controlling the moisture-permeability of the porous polymer film in the air-permeable sheet layer and by selecting an appropriate condition to adhere the fibrous layer and the air-permeable sheet layer together. 
     The second side b of the cover (see FIG.  3 ( 2 )) may be water-permeable or water-impermeable. In the case of water-permeable, the second side b may be made of a woven fabric, a nonwoven fabric, or a knit material. If water-impermeable, the second side b may be an air-impermeable sheet or an air-permeable sheet but with low air-permeability, such as various water repellent, polymeric resin films and sheets. Examples of the air-impermeable sheet and an air-permeable sheet with low air-permeability may include air-impermeable polymer sheets, such as a polyethylene film. The thickness of the polymer sheet may be about 100 μm or less, preferably 20 to 90 μm, more preferably 30 to 70 μm, and still more preferably 40 to 60 μm. Examples of the polymer that may be used as a raw material for the air-impermeable sheet or the air-permeable sheet with low air-permeability may include polyethylene, polypropylene, polyester, polyamide, poly(vinyl chloride), poly(vinilydene chloride), polyurethane, polystyrene, ethylene-vinyl acetate copolymer, and polycarbonate. Further, the air-impermeable sheet or the air-permeable sheet with low air-permeability may be a mono-layered or a multi-layered film. If the second side b is water-impermeable, it is preferable that the second side b may have a two-layered structure that contains an inner, air-impermeable sheet or air-permeable sheet with low air-permeability (preferably an air-impermeable sheet) and an outer fibrous layer. The fibrous layer may be made of a material described above for the first side a. 
     The first side I of the bag of the water-retentive member (see  FIG. 4 ) may be made of a moisture- or water-permeable material. One example of the moisture- or water-permeable material may be a fibrous material. Specific examples of the fibrous material may be the same as those that have been described as the materials for the fibrous layer of the cover. It is preferable that the bag in the water-retentive member may be made of a nonwoven fabric. If the nonwoven fabric is used, the thickness may be about 30 to 150 g/m 2 , preferably 40 to 120 g/m 2 , and more preferably 50 to 70 g/m 2 . 
     The second side II of the bag of the water-retentive member (see  FIG. 4 ) may be water-permeable or water-impermeable. In the case of water-permeable, the second side II may be made of raw material such as a woven fabric, a nonwoven fabric, or a knit material. In the case of water-impermeable, the second side II may be an air-impermeable sheet or an air-permeable sheet with low air-permeability, such as various water repellent, polymeric resin films and sheets. The air-impermeable sheet and the air-permeable sheet with low air-permeability may be the same as those that have been described above. If the second side II is water-impermeable, the second side II may preferably have a two-layered structure containing a layer of an air-impermeable sheet or an air-permeable sheet with low air-permeability (preferably an air-impermeable sheet) and a fibrous layer. The fibrous layer may be the same as one described above. 
     When the second side II has a two-layered structure in the water-retentive member in a structure for cooling according to one embodiment of the invention, the layer of an air-impermeable sheet or an air-permeable sheet with low air-permeability may be placed either inside or outside. Similarly, the fibrous layer may be outside or inside. In a water-retentive member in a structure for cooling according to one embodiment of the invention, if the fibrous layer of the second side II comprises a water-absorptive polymer, a layer of an air-impermeable sheet or an air-permeable sheet with low air-permeability may be placed outside. If a fibrous layer of the second side II contains no water-absorptive polymer, a layer of an air-impermeable sheet or an air-permeable sheet with low air-permeability may be placed outside or inside. 
     A water-absorptive material for use with embodiments of the invention may have a water-absorptive property and/or a water-holding property. In accordance with embodiments of the present invention, preferred materials may include a water-absorptive material with a sheet-like form, i.e., a water-absorptive sheet. Examples of the water-absorptive material may include sheet-like water-absorptive materials such as paper, linear pulp, punched cotton, a nonwoven fabric with water-absorptive or water-retentive property, a woven fabric, and a porous sheet made of a synthetic resin; expanded synthetic resins such as polyurethane foam, viscose foams, nylon foams, expanded phenol resins, and expanded urea resins; sponge; absorptive cotton; rayon cotton; a mat made of a palm shell fiber or an excelsior fiber; and a blanket. Among them, a nonwoven fabric with water-absorptive or water-retentive property, e.g., a spun-needle, nonwoven fabric, is preferred because the nonwoven fabric may be light and resistant to degradation, and may also have excellent durability. 
     If a nonwoven fabric is used as the water-absorptive material, its thickness may be around 30 to 150 g/m 2 , preferably 50 to 120 g/m 2 , and more preferably 80 to 100 g/m 2 . The water-absorptive or water-retentive nonwoven fabric may be made from a water-absorptive fiber or a mixture of a water-absorptive fiber, and a water-retentive fiber. Examples of a water-absorptive fiber may include a cross-linked acrylate fiber, a surface-hydrolyzed acrylic fiber, a fiber made of a polyester-(meth)acrylic acid graft copolymer, and a polyester fiber. In addition to hydrophilic fibers such as rayon, examples of the water-retentive fiber may also include a porous fiber, in which water may be held in voids (pores) present inside the fiber. 
     If a woven fabric is used as a water-absorptive sheet, its raw material may not be limited to those have water-absorptive or water-retentive property. Examples of the raw material include cotton, rayon, polyester, and acrylate. In the present invention, it is preferable to use a water-absorptive sheet containing a water-absorptive polymer. For example, the water-absorptive sheet may contain a water-absorptive polymer, in the following exemplary configurations: (1) a water-absorptive polymer bonded onto a surface of a water-absorptive sheet; (2) a water-absorptive polymer mixed in a water-absorptive sheet; and (3) a water-absorptive polymer present between two water-absorptive sheets to form a compound sheet. Note that these configurations are for illustrations only. One skilled in the art would appreciate that other configurations may also be used without departing from the scope of the invention, such a combination of these exemplary configurations. 
       FIG. 10  shows an example of the above configuration (2). Part of the water-absorptive polymer  11  may be bonded onto a surface of a water-absorptive support sheet  13 . 
     In one embodiment of the invention, a water-retentive member may contain a bag (preferably a bag made of a nonwoven fabric) that has a water-absorptive polymer. In this case, the water-absorptive polymer is present on an inner surface of the bag or in the material of which the bag is made. Thus, the water-absorptive polymer may be bonded onto a surface of a member (e.g., a nonwoven fabric) of the bag or may be mixed within the materials of which the bag is made, Alternatively, at least one side of the bag may be made by placing the water-absorptive polymer between two water-absorptive sheets. 
     Examples of water-absorptive polymers include polyacrylates (e.g., copolymer of acrylic acid and a sodium salt of acrylic acid, i.e., partial salt of poly(acrylic acid)), a copolymer of an acrylic acid and vinyl alcohol, a cross-linked poly(sodium acrylate), a graft copolymer of starch and acrylic acid, a hydrolyte of a cross-linked graft copolymer of starch and acrylic acid, a copolymer of isobutylene and maleic anhydride, a saponified copolymer of isobutylene and maleic anhydride, poly(aspartic acid), a cross-linked copolymer of acrylamide, a cross-linked copolymer of acrylic acid (or an acrylate) and acrylamide, a cross-linked poly(acrylic acid), a cross-linked polyacrylate, a cross-linked copolymer of acrylic acid (or a salt of acrylic acid) and an acrylic ester, a cross-linked polyvinyl alcohol denatured with a carboxylic acid, a cross-linked N-vinyl compound, a cross-linked poly(sulfonic acid), a cross-linked poly(sulfonate), a cross-linked copolymer of acrylic acid (or an acrylate) and sulfonic acid (or a sulfonate), a cross-linked poly((meth)acrylamide-N-alkyl (C 1-5 ) sulfonic acid (or a sulfonate)), a cross-linked copolymer of a (meth)acrylamide-N-alkyl (C 1-5 ) sulfonic acid (or a sulfonate) and a (meth)acrylate, a cross-linked sulfonated polyethylene, a cross-linked poval (trademark), a cross-linked poly(meth)acrylamide, a cross-linked poly(ethylene oxide), a cross-linked poly(vinylalcohol), and a cross-linked carboxymethylcellulose. Water absorptive polymers may be preferred because, for example, they may absorb a brine (0.9% salt concentration) at the capacity of 70 to 150 times the weight of the polymer (JIS K7223). 
     The methods of manufacturing a sheet (e.g., a nonwoven fabric) that holds a water-absorptive polymer are not particularly limited. Examples include the following: (1) a polymer may be placed between two water-absorptive sheets, and the bonding between them may be achieved by using, for example, a thermal treatment or an adhesive; (2) a water-absorptive polymer may be scattered and adhered onto the adhesive surface(s) of a water-absorptive sheet; and (3) a nonwoven fabric may be prepared or a paper may be prepared from a pulp in the presence of a water-absorptive polymer. 
     Although the amount of the polymer is not limited, it may be about 30 to 200 g/m 2 , preferably 50 to 150 g/m 2 , and more preferably 70 to 100 g/m 2 . 
     The positions of the water-absorptive sheet with a water-absorptive polymer inside the bag are not particularly limited. In the case of plural layers of sheets, the water-absorptive sheet with a water-absorptive polymer may be preferably placed as a outermost layer that faces inner surface of first side I (the outer surface of the side I faces an air-permeable side of the cover) of the water-retentive member, or as a second layer next to the outermost layer. 
     A water-retentive member used in a structure for cooling according to embodiments the present invention may also include a minus (negative) ions-emitting material. This material may be used in the following fashion: (1) bonded onto the inner surface of the bag of a water-retentive member, (2) bonded onto a surface of a water-absorptive material, (3) mixed within a water-absorptive material, or (4) placed between two water-absorptive materials. Examples of the minus (negative) ions-emitting material include tourmaline, weathered coral, minerals of rare earth elements, amber, carbon black, thoron, and germanium. 
     In accordance with some embodiments of the present invention, a water-retentive member or a water-absorptive polymer may contain an antifungal agent. The kinds of the antifungal agents are not limited. However, those agents that cause no or low irritation are preferred. 
     Examples of preferred antifungal agents include triazole derivatives such as  2 -(4-chlorophenyl)-3-cyclopropyl-1-(1H-1,2,4-triazol-1-yl)-butan-2-ol, carboxybenzotriazole, and {1-(4-chlorophenoxy)-3,3-dimethyl-1-(1,2,4-triazole)-1-yl}-butan-2-on; pyrithione derivatives such as zinc or sodium salt of 2-pyridinethiol-1-oxide; benzimidazole derivatives such as 2-(4-thiazolyl)benzimidazole, 2-(carbomethoxyamino)benzimidazole, 2-benzimidazole methylcarbamate, 1-butylcarbamyl-2-benzimidazole methylcarbamate, 6-benzoyl-2-benzimidazole methylcarbamate, 6-(2-thiophenecarbonyl)-2-benzimidazole methylcarbamate, 2-thiocyanomethylthiobenzimidazole, 1-dimethylaminosulfonyl-2-cyano-4-bromo-6-trifluoromethylbenzimidazole, 2-(2-chlorophenyl)benzimidazole, 2-{1-(3,5-dimethylpyrazolyl)}benzimidazole, 2-(2-furyl)benzimidazole, parbendazole, 5,6-dichloro-1-phenoxycarbonyl-2-trifluoromethylbenzimidazole, and 4,5,6,7-tetrachloro-2-trifluoromethylbenzimidazole; benzthiazole derivatives such as 2-(4-thiocyanomethyl-thio)benzthiazole, sodium salt of 2-mercaptobenzthiazole, zinc salt of 2-mercaptobenz-thiazole, and 2-(thiocyanomethylsulfonyl)benzthiazole, isothiazoline derivatives such as 2-(n-octyl)-4-isothiazolin-3-on, 1,2-benzisothiazolin-3-on, 5-chloro-2-methyl-4-isothiazolin-3-on, 2-methyl-4-isothiazolin-3-on, and 4,5-dichloro-2-cyclohexyl-4-isothiazolin-3-on; and thiabendazole derivatives such as thiabendazole. 
     Among the preferred antifungal agents described above, at least one member selected from the group consisting of triazole derivatives, pyrithione derivatives, benzthiazole derivatives, isothiazoline derivatives, and thiabendazole derivatives is preferred. The triazole derivatives are more preferred. The antifungal agents may be adhered to the surface(s) of a water-retentive member, mixed within a water-retentive member, adhered to the surfaces of the particles of water-absorptive polymers, or mixed within water-absorptive polymers. The amounts of the antifungal agents may be preferably 0.1 to 40 g/m 2  of the area of the water-retentive member, more preferably 2 to 20 g/m 2 , still more preferably 4 to 10 g/m 2 , and extremely preferably 6 to 8 g/m 2 . The amounts of the antifungal agents may be preferably 0.001 to 5% by weight of the water-absorptive polymers, more preferably 0.01 to 3% by weight, still more preferably 0.1 to 1% by weight. 
     Methods for bonding antifungal agents to a water-retentive member or a water-absorptive polymer are not restricted. The methods for mixing the antifungal agents within a water-retentive member or a water-absorptive polymer are likewise not restricted. Preferred methods include the following: (1) when a air-permeable sheet is prepared, the antifungal agents may be mixed with other raw materials; (2) when the particles of the water-absorptive polymers are prepared, the antifungal agents may be mixed with other raw materials; (3) the air-permeable sheets or the particles of the water-absorptive polymers may be first immersed in a solution containing a antifungal agent and then dried; (4) a surface of an air-permeable sheet may be printed with a liquid containing an antifungal agent and a binder; (5) a liquid containing an antifungal agent and a binder may be applied onto a surface of an air-permeable sheet; (6) a liquid containing an antifungal agent (and a binder, if necessary) may be first sprayed onto a water-retentive member, a air-permeable sheet or the particles of a water-absorptive polymer, and then dried. It is preferable to use a liquid containing an antifungal agent and a binder to adhere the antifungal agent to a water-retentive member. The liquid may be a solution or an emulsion. The binder may be a monomer, a polymer, or a resin. If the monomer, preferably a self-polymerizing or self-cross-linking type, is used, it may be polymerized or cross-linked during a drying or heating process. A polymer prepared from a self-polymerizing or self-cross-linking monomer may be tightly bound to a water-retentive member with an antifungal agent 
     Examples of a water-soluble or dispersible polymer or resin as the binder may include polyvinyl alcohol; cellulose compounds such as those prepared by chemically treating a natural cellulose, e.g., a sulfated, phosphorylated, nitrated, carboxymethylated, carboxypropylated, or hydroxyethylated cellulose; starch derivatives such as phosphorylated starch, methyl starch, carboxymethyl starch, and hydroxyethyl starch; vinyl acetate derivatives such as poly(vinyl acetate), vinyl acetate-maleate copolymers, and vinyl acetate-acrylic copolymers. Examples of an organic solvent-soluble or dispersible polymer or resin as the binder may include urethane polymers, styrene-butadiene polymers, and acrylic polymers. 
     Examples of a self-polymerizing or self-cross-linking monomer type binder may include an acrylic one for a solution polymerization containing an acrylic monomer and an initiator; and those for emulsion polymerization such as a solvent and wear resistance acrylic emulsion, a weather proof acrylic-silicone emulsion, a colloid-stable, fine-grain acrylic-silicone emulsion, a one-component, cold-cross-linking acrylic emulsion, an alkali-setting, cationic, fine-grain acrylic-silicone emulsion, and a hybrid acrylic epoxy emulsion. 
     The concentration of an antifungal agent in a liquid may be preferably 0.1 to 50% by weight, more preferably 1 to 40% by weight, and still more preferably 2 to 30% by weight. The concentration of a binder (i.e., a monomer, a polymer, or a resin) in a liquid may be preferably 2 to 30% by weight, more preferably 4 to 20% by weight, and still more preferably 6 to 15% by weight. 
     Examples of processes for making a structure for cooling in accordance with embodiments of the present invention are as follows. 
     The cover may be made as follows: 
     A composite material for the first side a (an air-permeable side) of the cover may be prepared by partially adhering an air-permeable polymer film to one surface of a woven or nonwoven fabric using any known method. Another composite material for the second side b (a water-impermeable side) of the cover may be prepared by partially or completely adhering an air-impermeable polymer film with one surface of a woven or nonwoven fabric using any known method. A composite material for the air-permeable side a and a composite material for the water-impermeable side b may be placed so that the air-permeable polymer film faces the air-impermeable polymer film. The peripheries may be subsequently sewn so as to form a bag. A means for opening and closing such as fasteners may be installed on the bag. 
     Water-retentive members used in embodiments of the invention, such as the water-retentive members  200  and  300  shown in  FIGS. 4 and 5 , may be made as follows: 
     First, place a water-absorptive sheet(s) (e.g.,  FIG. 4  shows a water-absorptive sheet  15  with a water-absorptive polymer; and  FIG. 5  shows a water-absorptive sheet  15  with a water-absorptive polymer and a second water-absorptive sheet  17  without a water-absorptive polymer) on a nonwoven fabric. Second, the water-absorptive sheet(s) may be covered by another nonwoven fabric. Finally, the peripheries may be adhered, fused, or sewed. 
     Among the water-retentive members used in embodiments of the invention, the member  700  shown in  FIG. 9  may be made as follows: 
     A composite material may be prepared by completely adhering an air-impermeable polymer film onto one surface of a nonwoven fabric using any known method. The water-absorptive sheets (e.g., a water-absorptive sheet  15  with a water-absorptive polymer and a water-absorptive sheet  17  without a water-absorptive polymer) may then be placed on a nonwoven fabric  9   y  of the composite material. Both ends of the composite material may be folded down to place the edges of the composite material above the both ends of the water-absorptive sheets. A nonwoven fabric  9   x  may be placed above the outermost water-absorptive sheet to cover the sheet. The edges of the nonwoven fabric  9   x  may be adhered to both edges of the composite material (i.e., the edge of a part  9   y   1  and the edge of another part  9   y   3 ). 
     One example of the water retentive members used in some embodiments of the invention may be prepared as follows: 
     A water-absorptive polymer may be adhered to a rectangular (or other shape) nonwoven fabric. Briefly, a nonwoven fabric may be folded into a rectangular form, one half of which may have the water-absorptive polymer present inside. On the three sides of the rectangular form (other than the folded side), two sheets of a nonwoven fabric are adhered or fused to each other to form a bag. A water-absorptive sheet(s) may be placed on one half area of a surface of a nonwoven fabric where water-absorptive polymers are adhered. The bag with a rectangular form and a size of one half may be made by folding and adhering the nonwoven fabric. 
     One example of a method of using a structure for cooling in accordance with one embodiment the present invention is as follows: 
     First, open the fastener of the cover. Second, place the water-retentive member on the second side b (water impermeable side) of the cover. Third, add water to the water-retentive member through the first side I of a moisture- or water-permeable material. For example, water may be poured onto the water-retentive member using a kettle. Then, close the fastener. 
     If the second side II of the bag of the water-retentive member is water-impermeable, the water-retentive member may be taken out of the cover. Water may then be poured onto the member before placing the member back into the cover. The amount of water needed to fill the water-retentive member is not limited, insofar as it is within the water-holding capacity of water-absorptive polymer and other water-absorptive materials. For example, the amount of water may be such that the water-retentive member has a weight of about 300 to 15,000 g/m 2 , preferably 500 to 10,000 g/m 2 , more preferably 1,000 to 7,000 g/m 2 , and specifically preferably 2,000 to 5,000 g/m 2 . The water may be supplied to a part of the water-retentive member. 
     It is preferred to add a preservative, an antiseptics, or an antifungal agent to the water inside the water-retentive member. Examples of preservatives, antiseptics, and antifungal agents may include thiabendazole compounds, organophosphoric acid compounds, phenyphenol compounds, isothiazole compounds, benzalkonium chloride, benzethonium chloride, alkyldiaminoethylglycine hydrochloride, chlorohexydine gluconate, and sodium hypochlorite. The preservatives, the antiseptics, or the antifungal agents may be used at a concentration of about 0.0001 to 0.1% (weight/volume) and preferably 0.01 to 0.1% (weight/volume). 
     EXAMPLES 
     Hereafter embodiments of the present invention are illustrated using the following examples. 
     Example 1 
     (1) Preparation of Pads 
     The pads shown in  FIG. 9  may be prepared, for example, by using the following materials: 
     A. Materials Used for Each Layer
     A-1. Fibrous layers  1  and  7  of a cover  100 : a board made of polyester (65%) and cotton (35%); yarn finenesses of 45 counts×45 counts with density of 100×70.   A-2. Air-permeable sheet layer  3  of a cover  100 : porous polyethylene film with thickness of 50 μm.   A-3. Air-impermeable sheet layer  5  of a cover  100 : polyethylene film; thickness of 50 μm.   A-4. Nonwoven fabric  9   x  of a bag P of a water-retentive member  700 ; a lid portion: spun-bonded nonwoven fabric made of a polyester with thickness of 40 g/m 2 .   A-5. Nonwoven fabric  9   y  of a bag P of a water-retentive member  700 ; a bottom portion and side portions: spun-bonded nonwoven fabric made of a polypropylene with thickness of 40 g/m 2 .   A-6. Air-impermeable sheet layer  19  of a bag P of a water-retentive member  700 : polyethylene film with thickness of 40 μm.   A-7. Water-absorptive sheets  13  and  17 : spun-needle nonwoven fabric made of polyester (50%) and rayon (50%) with thickness of 100 g/m 2 .   A-8. Water-absorptive polymer  11 : cross-linked copolymer of isobutylene and maleic anhydride sodium salt (manufactured by Kurare); absorbable amount of brine: 100 times the weight of the polymer  11 ; amount of the polymer  11  that are adhered to the water-absorptive sheet: 70 g/m 2      

     B. Method for Preparation 
     B-1. Cover  100   
     (i) Five kinds of composite materials a are prepared by partially adhering a porous polyethylene film  3  to a board  1  of polyester (65%) and cotton (35%) using an adhesive. The adhesion areas are controlled so that the composite materials are expected to have moisture-permeability of about 500 g/m 2 ·24 hours, about 700 g/m 2 ·24 hours, about 1,000 g/m 2 ·24 hours, about 1,200 g/m 2 ·24 hours, or about 1,500 g/m 2 ·24 hours, as determined by the Lyssy method. After preparation, the actual moisture-permeabilities of the five composite materials are determined by the Lyssy method. The results are 492 g/m 2 ·24 hours (about 500 g/m 2 ·24 hours), 708 g/m 2 ·24 hours (about 700 g ·m 2 ·24 hours), 1,015 g/m 2 ·24 hours (about 1,000 g/m 2 ·24 hours), 1,263 g/m 2 ·24 hours (about 1,200 g/m 2 ·24 hours), and 1,528 g/m 2 ·24 hours (about 1,500 g/m 2 ·24 hours). 
     (ii) A composite material b is prepared by completely adhering a polyethylene film  5  to a board  1  of polyester (65%) and cotton (35%)  7  using an adhesive. 
     (iii) The composite materials a and the composite material b are placed so that the porous polyethylene film  3  faces the polyethylene film  5 . Then, one side of the rectangle is sewed. A fastener F is sewed to the remaining three sides to make a bag that can be opened and closed by the fastener F. The size of the bag is about 20 cm×30 cm. 
     B-2. Water-Retentive Member  700   
     (i) Referring to  FIG. 9 , a composite material c is prepared by completely adhering a polyethylene film  19  (having sections  19   y   1 ,  19   y   2 , and  19   y   3 ) onto one surface of a spun-bonded nonwoven fabric  9   y  (having sections  9   y   1 ,  9   y   2 , and  9   y   3 ) made of a polypropylene using an adhesive. 
     (ii) A water-absorptive sheet  15  (comprising water-absorptive polymers 11 adhered to a spun-needle nonwoven fabric  13 ) is placed on the surface of a nonwoven fabric  9   y  of the composite material c. A spun-needle nonwoven fabric  17  is then placed on the water-absorptive sheet  15  (see  FIG. 9 ). 
     (iii) Ends of the composite material c are folded to place the edges of the composite material c above the ends of the spun-needle nonwoven fabric  17 . 
     (iv) A spun-bonded nonwoven fabric  9   x  made of a polyester is placed above the spun-needle nonwoven fabric  17 . The edges of the nonwoven fabric  9   x  may be adhered to both edges of the composite material c (i.e., the edges of the nonwoven fabrics  9   y   1  and  9   y   3 ). On this side and far side, the nonwoven fabric  9   x  and the nonwoven fabrics  9   y   1  and  9   y   3  of the composite material c are adhered to the nonwoven fabric  9   y   2  of the composite material c. 
     B-3. Preparation of Test Samples (Pads) 
     A water-retentive member  700  is placed on the side b of the cover  100 , and then water is poured into the water-retentive member  700  through the nonwoven fabric  9   x . The water-retentive member  700  holds water to a weight of 3.5 kg/m 2 . The fastener is then closed. 
     (2) Determination of Surface Temperatures 
     The test samples are left in a thermostatic chamber of about 33 degrees Celsius, and their surface temperatures are determined at appropriate time intervals. The results from these tests are shown in  FIG. 11 . 
       FIG. 11  clearly shows that the surface temperatures of the pads decrease with time. Pads having covers with higher moisture-permeability show greater decreases of temperature. In the pad having a moisture-permeability of about 500 g/m 2 ·24 hours, the surface temperature barely decreases. 
     Example 2 
     (1) Preparation of Pads 
     Similar to Example 1, three kinds of pads are prepared having a size of 100 cm×200 cm. For the air-permeable side of the cover, composite materials a having moisture-permeability of about 1,000 g/m 2 ·24 hours, about 1,200 g/m 2 ·24 hours, and about 1,500 g/m 2 ·24 hours by the Lyssy method are used. The amount of the water poured into the pads is 7 kg per pad (i.e., 3.5 kg/m 2  of the water-retentive member). 
     (2) Organoleptic Test 
     A futon (which is like a mattress) is positioned inside a room, in which the temperature is set at 30 degrees Celsius. The pad is laid on the futon and covered with a sheet made of a cotton. As a control, a futon without the pad is prepared. 
     The surface temperatures on the sheet are determined by using a surface thermometer. Each panelist lies on the sheet and judged at appropriate time intervals whether he(she) feels cool or warm at neck, shoulders, loin, hip, legs/feet, and arms. The results from these tests are shown in  FIG. 12 . 
       FIG. 12  clearly shows that when a pad is not used (control), five minutes after the start of the test, the panelists feel warm at three portions, i.e., neck, shoulders, and loin. At ten minutes after the start of the test, the panelists feel warm at five portions including portions (areas) other than arms. At forty minutes after the start of the test, the panelists feel warm at all judged portions. On the other hand, when the pads of the present invention are used, the panelists feel cooler with time. Therefore, when a pad of the present invention is used, an appropriate cooling sensation can be felt. A person may thus sleep comfortably even when the ambient temperature is high. 
     Example 3 
     (1) Preparation of Pads Containing Antifungal Agent 
     One pad is prepared in the same manner as described in Example 1, except that the cover  100  has a size of 95 cm×185 cm. The water-retentive member  700  has a size of 90 cm×180 cm containing an antifungal agent. The air-permeable side of the cover has a moisture-permeability of about 1,000 g/m 2 ·24 hours. 
     (2) Preparation of Liquid Containing an Antifungal Agent and Binder 
     Table 1 shows the formulation of a solution containing an antifungal agent. The solution is prepared by mixing the raw materials. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Amounts 
               
               
                 Raw Materials 
                 (% by weight) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
            
               
                 Amorden NBP8 (Triazole Derivative from Yamato 
                 2 
               
               
                 Chemical Industrial Co., Ltd.) 
               
               
                 Aqueous Binder of Vinyl Acetate Derivative 
                 1 
               
               
                 Water 
                 97 
               
               
                 Total 
                 100 
               
               
                   
               
            
           
         
       
     
     (3) Adhesion of Antifungal Agent 
     From about 1 meter above the nonwoven fabric  9   x  of the bag P, the solution shown in Table 1 is uniformly sprayed on the water-retentive member  700 . The amount of the solution used is about 500 g. Namely, to the water-retentive member  700  having a size of 90 cm×180 cm, 10 g of the antifungal agent are given. Then, the water-retentive member  700  is left to dry under the ambient conditions. Cooling structures with antifungal agents are expected to last longer and may be reused without fungal or mold growth. 
     Embodiments of the invention may include one or more of the following advantages. Structures for cooling in accordance with embodiments of the present invention may be repeatedly used for a long time. It is of light weight and portable because the structure may not contain water before its use. Further, these structures may be easily folded for convenient transportation. The structures for cooling may be used for sleep comfort in the summer. By controlling moisture permeability of the cover, the cooling efficiency may then be controlled. For example, having the structure&#39;s cover with a large moisture permeability and the use of large amount of water or refrigerated water, a large cooling effect may be achieved. Furthermore, the structures may be adjusted to hold water in portions of a cooling structure to cool certain parts of body (e.g., shoulder or back). That is, water may be added and held at only part(s) of the water-retentive member corresponding to part(s) of human body that need to be cooled. Thus, the structures may be suitable for cooling in the field of medical care. For example, the structures for cooling according to embodiments of the invention having water-absorptive material may be used as a cushion suitable for bed pads. Furthermore, the structures for cooling in accordance with embodiments of the present invention may contain antifungal agents to eliminate or minimize the problem of mold contamination. 
     While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims.