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  Process for producing nonwoven fabric and nonwoven fabricUSPTO Application #: 20080045109Title: Process for producing nonwoven fabric and nonwoven fabric Abstract: The nonwoven fabric production process of the invention comprises a laminating step in which composite yarn, obtained by bundling a plurality of resin single filaments each having a core-sheath structure with a filamentous core resin surrounded by a sheath resin with a melting point of at least 20° C. lower than the core resin and fusing the sheath resin together, is laminated in at least the three directions of warp direction, slant direction and reverse slant direction, and a bonding step of heating the laminated filament bundles at a temperature lower than the melting point of the core resin and higher than the melting point of the sheath resin for bonding. According to the invention, it is possible to provide a nonwoven fabric production process and nonwoven fabrics with excellent plasticity and shape following property, as well as adjustable strength for adaptation to different purposes and required properties. (end of abstract) Agent: Greenlee Winner And Sullivan P C - Boulder, CO, US Inventors: Toshiyuki Ogata, Shin Kasai, Hirofumi Yashiro, Akio Ohta USPTO Applicaton #: 20080045109 - Class: 442364 (USPTO) The Patent Description & Claims data below is from USPTO Patent Application 20080045109. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001]The present invention relates to a process for production of a nonwoven fabric obtained by laminating continuous filament yarn, and to a nonwoven fabric obtained by laminating continuous filament yarn. BACKGROUND ART [0002]As industrial materials including anti-concrete flaking materials, there are commonly used woven and knitted fabrics made of glass fibers, carbon fibers, aramid fibers, vinylon fibers and the like, as well as various types of Sofu.TM. (continuous filament nonwoven fabrics). Sofu includes triaxial Sofu laminated in the warp, slant and reverse slant directions, and tetraaxial Sofu laminated in the warp, weft, slant and reverse slant directions. [0003]Known processes for production of Sofu include processes wherein vinylon fibers, for example, are paralleled in a prescribed direction and the fibers are bonded together with a hot-melt adhesive or emulsion adhesive. Also publicly known are production processes wherein reinforced fibers (glass fibers, carbon fibers, alumina fibers, aramid fibers or the like) coated with a thermoplastic resin are paralleled and fused together (for example, see Patent document 1), and production processes wherein a thermoplastic resin is attached and bonded to the surfaces of reinforced fibers (for example, see Patent document 2). There are also known mesh sheets obtained by weaving or knitting using core-sheath fibers comprising a polyester-based polymer as the core and a polyester-based polymer with a lower melting point than the core polyester-based polymer as the sheath (for example, see Patent document 3). [0004][Patent document 1] Japanese Unexamined Patent Publication No. HEI 11-20059 [0005][Patent document 2] WO00/21742 [0006][Patent document 3] Japanese Unexamined Patent Publication No. 2003-301346 DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention [0007]However, in production processes involving bonding with a hot-melt adhesive or emulsion adhesive after setting of vinylon fibers, cost is increased due to use of the adhesive, while the adhesive also adheres to unwanted sections and creates a poor operating environment for the nonwoven fabric production process. [0008]In processes employing a thermoplastic resin for fusion of reinforced fibers, because it is difficult to completely cover the reinforced fibers with the thermoplastic resin, the adhesive force is inadequate and consequently the durability is not sufficient particularly for long-term use such as for anti-concrete flaking. [0009]On the other hand, for mesh sheets obtained by weaving or knitting using a polyester-based polymer with a core-sheath structure, it is not possible to increase the gaps between fibers as with Sofu and they are poorly suitable as anti-concrete flaking materials, while extra labor is required for manufacture of the mesh body, such that the production cost is increased. [0010]In addition, the aforementioned disclosed examples of Sofu and mesh sheets all have poor plasticity and flexibility, and their shape following property is therefore inadequate. Because such Sofu and mesh sheet materials are not very universally applicable in the field of industrial materials such as anti-concrete flaking materials, there is a strong demand for their improvement. [0011]It is therefore an object of the present invention to provide a production process for a nonwoven fabric comprising continuous filaments with excellent plasticity and flexibility, a superior shape following property and also adjustable strength and plasticity to yield properties adaptable to various uses and needs. It is another object of the invention to provide a nonwoven fabric comprising continuous filaments obtained by the aforementioned production process. Means for Solving the Problems [0012]In order to achieve these objects, the nonwoven fabric production process of the invention is characterized by comprising a laminating step of bundling a plurality of resin single filaments each having a core-sheath structure with a filamentous core resin surrounded by a sheath resin with a melting point of at least 20.degree. C. lower than the core resin, fusing the sheath resin together to form composite yarn, and laminating it in at least the three directions of warp direction, slant direction and reverse slant direction, and a bonding step of heating the laminated composite yarn at a temperature lower than the melting point of the core resin and higher than the melting point of the sheath resin for bonding. [0013]The composite yarn used in the nonwoven fabric production process of the invention is obtained by fusing the sheath resin, and therefore it has excellent plasticity and strength while the resin single filaments do not separate, thereby allowing production of a nonwoven fabric with minimal trouble during nonwoven fabric production and excellent plasticity and strength. Furthermore, since the sheath resin of the core-sheath structure has a melting point that is at least 20.degree. C. lower than the core resin,. when the composite yarn is laminated in different directions and then heated at a temperature below the melting point of the core resin and higher than the melting point of the sheath resin in the nonwoven fabric production process of the invention, only the sheath resin is melted without melting of the core resin, thereby allowing the composite yarn to be bonded together. In other words, it is possible to produce a nonwoven fabric of the invention without using an adhesive such as a hot-melt resin or thermoplastic resin. Furthermore, since the difference in melting points is 20.degree. C. or more, the core resin is resistant to melting despite melting of the sheath resin, and the core resin maintains its filamentous shape, thereby allowing deformation of the composite yarn to be prevented during production of the nonwoven fabric. In other words, since it is possible to prevent deformation or cutting of the composite yarn that readily occurs when using resin single filaments without a core-sheath structure, trouble during production is further minimized. [0014]Furthermore, because the composite yarn is laminated in at least the three directions of warp direction, slant direction and reverse slant direction, a nonwoven fabric with excellent strength can be produced regardless of the directional property. [0015]The composite yarn in the nonwoven fabric production process of the invention is composed of 10-500 resin single filaments, and preferably the core resin of the composite yarn forms filamentous island sections with a size of 1-70 dtex (island resin) while the fused sheath resin forms sea sections (sea resin). Because this type of composite yarn is in the form of a fiber-reinforced thermoplastic resin, it has strength and rigidity in the lengthwise (fiber axis) direction, and using such composite yarn can further improve the plasticity and strength of the nonwoven fabric. Moreover, the cross-sectional diameter and number of bundles of the island resin can be adjusted to achieve suitable strength and plasticity, for a further improved shape following property. [0016]For the nonwoven fabric production process of the invention, the core resin and sheath resin of the resin single filaments in the core-sheath structure are preferably polyolefins. Using a polyolefin as the core resin will result in superior plasticity and workability. If both the core resin and sheath resin are polyolefins, affinity between the core resin and sheath resin is high so that even when the polyolefin of the sheath resin has melted it does not separate from the polyolefin of the core resin, thereby allowing a composite yarn structure to be maintained having the core as reinforcing fiber and the sheath as matrix resin. Furthermore, since polyolefins are non-polar it is possible to produce a nonwoven fabric with resistance to acids and bases and excellent durability. [0017]The core resin is preferably polypropylene and the sheath resin is preferably polyethylene with a melting point of no higher than 120.degree. C. A nonwoven fabric having this construction exhibits the properties of composite yarn together with particularly excellent plasticity and flexibility, and a superior shape following property. That is, when conventional Sofu is used to cover folded sections they spring back by the elasticity of the Sofu due to poor plasticity and flexibility, such that it is difficult to cover corners, but the nonwoven fabric of the invention is easily folded and can therefore follow the shape of objects when bonded thereto. [0018]If the core resin is polypropylene its melting point is relatively high, and therefore separation and decomposition by heat or acids/bases can be prevented. The nonwoven fabric can therefore maintain its shape even with prolonged use. Also, since polypropylene is a thermoplastic resin, it can be recycled and is environmentally friendly. [0019]Furthermore, since a polyethylene sheath resin has a relatively low melting point it melts readily, and particularly if its melting point is 120.degree. C. or below the manufacturing efficiency is drastically improved and energy loss is reduced. [0020]The nonwoven fabric of the invention is a nonwoven fabric obtained by laminating a composite yarn having 10-500 filamentous island resin filaments with a size of 1-70 dtex situated in a filamentous sea resin (preferably with the filamentous island resin situated along the lengthwise direction of the filamentous sea resin) in at least the three directions of warp direction, slant direction and reverse slant direction, and melting the sea resin to bond together the laminated composite yarn, characterized in that the sea resin has a melting point of at least 20.degree. C. below that of the island resin. This type of composite yarn has excellent plasticity and therefore produces minimal trouble in the production of nonwoven fabrics, while yielding nonwoven fabrics with excellent plasticity and strength. [0021]The production process for the composite yarn in the nonwoven fabric of the invention may be any of the following. [0022](1) A process wherein resin single filaments with a core-sheath structure are bundled and stretched at a temperature below the melting point of the core resin and above the melting point of the sheath resin, while melting the sheath resin to fuse the sheath resin together and form a sea resin (matrix), for composite yarn having a sea-island structure with the core resin as the island resin (reinforcing fiber). [0023](2) A process wherein stretched core-sheath structure filaments are heated in a paralleled state at a temperature higher than the melting point of the sheath and below the melting point of the core, while thermally bonding the sheaths together through a die of prescribed diameter. [0024](3) A process involving stretching of unstretched filaments having a sea-island structure composed of an island resin and a sea resin with a melting point that is at least 20.degree. C. lower than that of the island resin. In order to obtain a composite yarn with more excellent plasticity and strength, the aforementioned processes (1) and (2) are preferred, with process (1) being especially preferred. Continue reading... Full patent description for Process for producing nonwoven fabric and nonwoven fabric Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Process for producing nonwoven fabric and nonwoven fabric 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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