Low-density nonwoven fabric and production method and installation therefor and uses

Abstract

The invention concerns an installation for nonwoven production, characterized in that it comprises a spunbonded web plant whereof the die is inclined at an angle of 10 to 60° and preferably of 20 to 50° relative to the displacement direction of a conveyor and preferably two spunbonded web plants whereof the dies have opposite inclinations, said conveyor whereon filaments are deposited from the die(s) in the form of a web, a station for compressing the thus formed web into a web compressed perpendicular to its plane, optionally a station for calendering the compressed web, followed by a station for consolidating by pressurized water jet spray the compressed and optionally calendered web with a jet spraying machine comprising a metal fabric whereof the wires have a diameter between 0.10 and 0.35 mm and which has more than 40 wires per cm and preferably 10 to 30 wires per cm both in warp direction and in weft direction or with a water jet spraying machine including a sleeve with perforations of 50 to 600 microns and having 20 to 200 perforations per cm 2 .

1 . A nonwoven fabric made of filaments, having a ratio of the strength in the machine direction to the strength in the cross direction of less than 1.5, preferably less than 1.3 and better still less than 1.1, characterized by a density of less than 0.10 g/cm3, preferably between 0.09 and 0.03 g/cm3 and better still between 0.07 and 0.03 g/cm3.  
     
     
         2 . The nonwoven as claimed in  claim 1 , the filaments of which have a titer of between 0.9 and 10 dtex.  
     
     
         3 . The nonwoven as claimed in  claim 1 , characterized in that it has a tensile strength index in the machine direction of at least 1.5 and in the cross direction of at least 1.3 newtons per 50 mm per gram of nonwoven per m2 and it has a weight of between 12 and 150 g/m2, preferably between 12 and 50 g/m2 and better still between 12 and 30 g/m2.  
     
     
         4 . A method of producing a nonwoven, in which filaments coming from a spunbond unit with a die are deposited as a web having a longitudinal direction onto a conveyor, the web is compressed, perpendicular to the plane of the web, into a compressed web and then the compressed web is subjected to a consolidation operation by blasting it with water jets having a diameter of 50 to 250 microns at a pressure of 50 to 500 bar, characterized in that: 
 the web is deposited onto the conveyor using at least one spunbond unit the die of which is inclined relative to the longitudinal direction, and preferably at least two spunbond units the two dies of which are inclined, preferably in opposite directions, relative to the longitudinal direction, at an angle of 10 to 60°, preferably 20 to 50°;    the water jets are blasted, either with interposition of the web, onto a metal fabric, the threads of which have a diameter of between 0.10 mm and 0.35 mm and preferably between 0.18 mm and 0.30 mm, and which has at most 40 and preferably 15 to 30 warp threads per cm and at most 40 and preferably 15 to 30 weft threads per cm, or, with interposition of the web, onto a microperforated sleeve, the dimensions of the perforations of which are between 50 and 600 microns and preferably between 150 and 500 microns, and which has a number of perforations of between 50 and 200 per cm2.    
     
     
         5 . The method as claimed in  claim 4 , characterized in that the metal fabric has a thickness of between 0.40 and 0.75 mm.  
     
     
         6 . The method as claimed in  claim 4 , characterized in that the metal fabric has a plain, twill or satin weave.  
     
     
         7 . A nonwoven production installation, characterized in that it comprises a spunbond unit whose die is inclined at an angle of 10 to 60°, and preferably 20 to 50°, relative to the direction of movement of a conveyor, and preferably two spunbond units whose dies are inclined, preferably in opposite directions, onto which conveyor the spunbond unit(s) deposits (deposit) filaments as a web, a compression station for compressing the web thus formed perpendicular to its plane into a compressed web, optionally a station for calendering the compressed web, and then a consolidation station for blasting pressurized water jets onto the compressed and optionally calendered web using a water-jet blasting machine which includes a metal fabric, the threads of which have a diameter of between 0.10 mm and 0.35 mm, there being at most 40 threads per cm and preferably 15 to 30 threads per cm both in the warp direction and in the weft direction, or using a water-jet blasting machine with a sleeve having 50 to 600 micron perforations, there being 20 to 200 perforations per cm2.  
     
     
         8 . A filter, characterized in that it comprises a nonwoven as claimed in  claim 1 .  
     
     
         9 . A hygiene product, characterized in that it comprises a nonwoven as claimed in  claim 1 , with a weight of between 12 and 50 g/cm2.