Dry production of a non-woven fibre web

Abstract

A plant that includes two air-lay stations placed one after the other serving for the dry production of a non-woven fiber web. Each station includes a fiber feed duct for feeding fibers to the station from a fiber source, an air-lay forming head connected to the fiber feed duct and at least partly defined by a perforated screen, and a suction box for successively sucking fibers in the forming head through the screen. A separate fiber source is part of each station. The first station furthermore has a fiber collector placed under the screen of its forming head whereas the second station has a forming wire placed under the screen of its forming head. The two stations are connected to at least one conveyor for conveying fibers from the fiber collector of the first station to the forming head of the second station. By means of the plant, a cotton fiber web on the basis of Cotton Linters Pulp and thermobinding fibers can be produced which, considering its quality, are price competitive with corresponding fiber webs based on cellulose pulp. This cotton fiber web has a homogenous, nit-free structure which is desirable for use in various products.

What is claimed is:  
     
         1 . A method for dry production of a non-woven fiber web that includes at least relatively short and relatively long fibers, wherein the method comprises the following process steps: 
 generating that a first air flow that contains short fibers from a fiber source,    passing the first air flow through a first perforated screen having openings of a size that allow open, but not unopen, short fibers to pass therethrough,    passing the first air flow through an air-permeable first forming wire running endlessly during operation to form a non-woven layer of short fibers thereon,    generating a second air flow that contains short fibers from the non-woven fiber layer that is formed on the forming wire,    generating a third air flow that contains long fibers from a fiber source of same,    passing the second and third air flows through a second perforated screen having openings of a size that allow both short and long fibers to pass therethrough,    passing the second and third air flows through an air-permeable second forming wire running endlessly during operation to form a fiber layer on the second forming wire, and    preparing a non-woven fiber web from the fiber layer from the second forming wire.    
     
     
         2 . The method according to  claim 1 , wherein unopen, short fibers are extracted from the first perforated screen.  
     
     
         3 . A plant for dry production of a non-woven fiber web comprising two air-lay stations placed after each other and each comprising at least one fiber feed duct for feeding fibers to the station from a fiber source, at least one air-lay forming head connected with the fiber feed duct and at least partly defined by a perforated screen, a suction box for successively sucking fibers through the screen, a separate fiber source associated with each of the two stations, a fiber collector associated with the first station and placed under the screen of its forming head(s), a forming wire associated with the second station and placed under the screen of its forming head(s), and at least one conveyor associated with the two stations for conveying fibers from the fiber collector of the first station to the forming head of the second station.  
     
     
         4 . The plant according to  claim 3 , wherein the fiber collector of the first station is a forming wire.  
     
     
         5 . The plant according to  claim 3 , wherein the fiber collector of the first station is part of the suction box of the forming head belonging to that station.  
     
     
         6 . The plant according to  claim 3 , wherein the fiber source of the first station consists essentially of relatively short fibers, and that the openings in the screen of its at least one forming head are of a size that mainly allow open, but not unopen short fibers to pass through; that the fiber source of the second station consists essentially of relatively long fibers, and that the openings in the screen of its at least one forming head are of a size that allow both the relatively short and the relatively long fibers to pass through.  
     
     
         7 . The plant according to  claim 6 , wherein the fiber source of the first station consists essentially of Cotton Linters Pulp, and that the fiber source of the second station consists essentially of thermobinding fibers.  
     
     
         8 . The plant according to  claim 7 , wherein the thermobinding fibers are bicomponent fibers having a core that is surrounded by an outer coating of a material having a lower melting point than that of the core.  
     
     
         9 . The plant according to  claim 3 , wherein the conveyor is a fiber feed duct extending between the fiber collector of the first station and the forming head of the second station.  
     
     
         10 . The plant according to  claim 3 , wherein at least the first station has at least one extraction duct and a conveyor fan for extracting unopen fibers or nits from the screen of the at least one forming head of that station.  
     
     
         11 . A non-woven air-laid fiber web comprising a mixture of thermobinding fibers and Cotton Linters Pulp which is mainly screened of unopen fibers.  
     
     
         12 . The non-woven air-laid fiber web according to  claim 11 , wherein the thermobinding fibers are bicomponent fibers having a core consisting essentially of a relatively strong material that is surrounded by an outer coating having a lower melting point than the core.  
     
     
         13 . A non-woven air-laid fiber web obtainable by the method of  claim 7 , such that the web comprises a mixture of thermobinding fibers and Cotton Linters Pulp which is mainly screened of unopen fibers.  
     
     
         14 . The non-woven air-laid fiber web according to  claim 12 , wherein the thermobinding fibers are bicomponent fibers having a core that is surrounded by an outer coating of a material having a lower melting point than that of the core.  
     
     
         15 . In a method for producing a non-woven fiber web, the improvement which comprises combining Cotton Linters Pulp together with thermobinding fibers to produce the web.  
     
     
         16 . The method of  claim 15  wherein the thermobinding fibers are bicomponent fibers having a core that is surrounded by an outer coating of a material having a lower melting point than that of the core.