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  High moisture absorbent nonwoven fabric structure and production method thereofUSPTO Application #: 20060234585Title: High moisture absorbent nonwoven fabric structure and production method thereof 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. (end of abstract) Agent: Kirschstein, Ottinger, Israel & Schiffmiller, P.C. - New York, NY, US Inventors: Noboru Watanabe, Tadashi Araki, Naomichi Momoi USPTO Applicaton #: 20060234585 - Class: 442327000 (USPTO) Related Patent Categories: Fabric (woven, Knitted, Or Nonwoven Textile Or Cloth, Etc.), Nonwoven Fabric (i.e., Nonwoven Strand Or Fiber Material) The Patent Description & Claims data below is from USPTO Patent Application 20060234585. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a high moisture absorbent nonwoven fabric structure. More particularly, it relates to a high moisture absorbent nonwoven fabric structure which has high moisture absorption capacity and is suitably used as drying agents used in transportation of precision parts, dew condensation preventing agents for industrial equipments, drying agents for eliminating moisture in bags for confectioneries, demoisturizers and the like, and its preparation. BACKGROUND ART [0002] As electronic parts such as silicon wafers cannot be used even when slightly rusted, close attention is paid for their transportation. Electronic parts are put in a tightly closed container together with a drying agent for transportation as they are apt to rust when the humidity comes higher. As the drying agent, silica gel is mainly used at present. Though silica gel can be recycled by heat treatment, it has problems of heat treating cost and breakage of particles during heat treatment. Hence, the silica gel drying agent is usually discarded after use. Though incineration or reclamation is used as the discarding method, the treatment shall be performed in a large amount and various problems such as incineration cost or lack of land to be reclaimed arise and thus materials easily reusable are desired. [0003] Though silica gel has been used for dew condensation prevention of industrial equipment in almost all cases, silica gel has a disadvantage of bulkiness as it is used in particle form. On the other hand, miniaturization of dew condensation inhibitor is desired accompanied to miniaturization of equipment. [0004] Silica gel and deliquescent salts such as calcium chloride are used as the drying agent and dehumidifying agent for confectioneries. Although they are disposed as non-inflammable refuse in average home, there are problems such as lack of land to be reclaimed and thus reduction in quantity is desired. Further, deliquescent salts become liquid by moisture absorption and are in danger of leaking from packing papers and in addition in danger of generating heat when water is added to cause a burn. [0005] On the other hand, the moisture absorbent nonwoven fabric is commonly prepared by a procedure in which high moisture absorbent fibers are mixed with other synthetic fibers and/or natural fibers and carded and needle-punched. However, the high moisture absorbent fiber is low in fiber strength and fibers are fell off highly during the manufacturing process at a higher mixing rate and further twine round the machine as they absorb moisture during the manufacturing process disadvantageously. Particularly, the high moisture absorbent fiber of the type wherein the surface gels by absorbing water and/or moisture has low fiber strength and the mixing rate is limited to about 40 weight %. [0006] Other methods for the preparation of moisture absorbent nonwoven fabrics include air laid method. However, in this method, it is required to mix heat fusion welding fibers to adhere the fibers with each other or to adhere the fiber layers with the surface sheets and also it is required to increase the mixing rate of heat fusion welding fibers for keeping the shape. [0007] The present invention has been made in consideration of the above circumstance and its object is to provide a high moisture absorbent nonwoven fabric which can be easily recycled after use and its preparation method. DISCLOSURE OF THE INVENTION [0008] We, inventors, have eagerly investigated to solve the above problem and, as the results, have invented the high moisture absorbent nonwoven fabric of the present invention. Thus, the high moisture absorbent nonwoven fabric structure of the present invention is 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 and it is characterized in the following (a) to (f). (a) Surface of said high moisture absorbent fiber gels by absorbing water and/or moisture to express self-adhering activity. (b) 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) At least one of the surface sheets has air permeability. (d) The thickness of the high moisture absorbent nonwoven fabric structure is not more than 1.5 mm. (e) The water content of the high moisture absorbent nonwoven fabric structure is 20 to 45 weight %. (f) The moisture-absorbing rate of the high moisture absorbent nonwoven fabric structure is at least 20 weight % under absolute dry condition at 20.degree. C. and 65% RH after 5 hours. [0009] A preferred embodiment of the high moisture absorbent nonwoven fabric structure is a high moisture absorbent nonwoven fabric structure in which the moisture-absorbing layer consists only of high moisture absorbent fibers. More preferably, the high moisture absorbent fibers are of a crosslinked sodium acrylate type. [0010] The apparent density of the high moisture absorbent nonwoven fabric structure is preferably 0.05 to 0.8 g/cm.sup.3. [0011] Furthermore, the high moisture absorbent nonwoven fabric structure having a three layers structure is preferably prepared through a moistening step and a drying step. [0012] The present invention relating to the method for the preparation of a high moisture absorbent nonwoven fabric structure is also 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 a 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 sheets. BEST MODE FOR CARRYING OUT THE INVENTION [0013] The high moisture absorbent fiber used in the moisture-absorbing layer of the present invention should be such one that the surface gels by absorbing water and/or moisture. Because, when the high moisture absorbent fiber is such one that the surface gels by absorbing water and/or moisture, self-adhering activity is expressed and the fibers in the moisture-absorbing layer adhere each other and the moisture-absorbing layer and the surface sheet adhere each other by the self-adhering activity, and hence any thermal bonding fiber is not required and a higher mixing rate of the high moisture absorbent fibers comes to be possible. When the high moisture absorbent fiber does not gel, self-adhering activity is not expressed and the fibers in the moisture-absorbing layer do not adhere each other and the moisture adhering layer and the surface sheet do not adhere each other and the shape cannot be kept. [0014] The high moisture absorbent nonwoven fabric structure of the present invention shall be of a three layers structure comprising a moisture-absorbing layer and surface sheets with the moisture-absorbing layer between. If the moisture-absorbing layer is exposed on the surface, the high moisture absorbent fibers fall off during production and no stable production can be made. Continue reading... Full patent description for High moisture absorbent nonwoven fabric structure and production method thereof Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this High moisture absorbent nonwoven fabric structure and production method thereof patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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