High moisture absorbing nonwoven fiber structure and production method therefor

Abstract

A high moisture absorbent nonwoven fabric structure comprising a moisture absorbing layer mainly consisting of high moisture absorbent fibers, and surface sheets sandwiching the moisture absorbing layer to constitute a three-layer structure. The high moisture absorbent fibers gel on the surfaces thereof by absorbing water and/or moisture to develop a self-bonding force. The high moisture absorbent nonwoven fabric has an absorptivity, after five hours at 20° C. and relative humidity of 65%, of at least 20 wt. %, at least one of the surface sheets has breathability, and the self-bonding force of high moisture absorbent fibers ensures bonding between fibers in the moisture absorbing layer and between the moisture absorbing layer and the surface sheets. The high moisture absorbent nonwoven fabric structure, which is high in hygroscopicity, applicable to a small space, and easily recyclable by heat treating nonwoven fabrics after moisture absorbed, can be used in a variety of fields such as desiccants and dehumidifying agents.

1 . A high moisture absorbent nonwoven fabric structure consisting of a three layers structure comprising a moisture-absorbing layer consisting mainly of high moisture absorbent fibers and surface sheets with the moisture-absorbing layer between, characterized in the following (a)˜(f): 
 (a) that surface of said high moisture absorbent fiber gels by absorbing water and/or moisture to express self-adhering activity,  
 (b) that the fibers in the moisture-absorbing layer adhere each other and the moisture-absorbing layer and the surface sheets adhere each other by the self-adhering activity of the high moisture absorbent fiber,  
 (c) that at least one of the surface sheets has air permeability,  
 (d) that the thickness of said high moisture absorbent nonwoven fabric structure is not more than 1.5 mm,  
 (e) that the water content of said high moisture absorbent nonwoven fabric structure is 20 to 45 weight %, and  
 (f) that the moisture-absorbing rate of said high moisture absorbent nonwoven fabric structure is at least 20 weight % under absolute dry condition at 20° C. and 65% RH after 5 hours.  
 
     
     
         2 . The high moisture absorbent nonwoven fabric structure according to  claim 1 , wherein said moisture-absorbing layer consists of high moisture absorbent fiber alone.  
     
     
         3 . The high moisture absorbent nonwoven fabric structure according to  claim 1  or  2 , wherein said high moisture absorbent fiber is a high moisture absorbent fiber of a crosslinked sodium acrylate type.  
     
     
         4 . The high moisture absorbent nonwoven fabric structure according to any of  claims 1  to  3 , wherein the apparent density is 0.05 to 0.8 g/cm 3 .  
     
     
         5 . The high moisture absorbent nonwoven fabric structure according to any of  claims 1  to  4 , wherein the high moisture absorbent nonwoven fabric structure consisting of three layers structure is prepared through moistening step and drying step.  
     
     
         6 . A method for the preparation of a high moisture absorbent nonwoven fabric structure, characterized in that a fiber, mixture mainly containing high moisture absorbent fibers are scattered continuously on one surface sheet having air permeability on a net, while sucked from net side to form a moisture-absorbing layer and then moistening step is applied on the moisture-absorbing layer to gel the surface of the high moisture absorbent fiber and then another surface sheet is laminated on it to give a three layers structure and then it is pressed and dried to adhere the fibers in the moisture-absorbing layer each other and adhere the moisture-absorbing layer with the surface sheet.