Method and device for bonding a non-woven fibre produced by the air-lay method

Abstract

The conventional method for production of a multiple-layer, non-woven fibre is by means of the air-lay method, with thermal bonding using bonding fibres. The same method can be applied to a composite non-woven fibre with an intermediate pulp layer. This method of bonding does not reduce the later pilling wear and hardly influences the inner composition of the layers of the composite. According to the invention, the outer non-woven fibre is preferably made from a bicomponent fibre and treated by hydrodynamic needling for bonding, such that not just the surface is bonded, but also the layers are bonded to each other.

1 . Method for strengthening a non-woven fabric, which has been produced according to the air-lay method, comprising two outer layers made of cut, thermally activatable fibres and one layer made of cellulose fibres, such as super-absorbent pulp, which is disposed between these outer layers, through continuous forming of initially the lower layer, then overlaying with the pulp layer and finally the top layer, characterised in that the two outer layers of the composite non-woven fabric are formed from fibres, which are from 8 to 10 mm maximum in length, and the three-layered non-woven fabric is subjected to a hydrodynamic needling process for the strengthening, that is to say also for the intimate bonding of the layers, which are laid solely according to the air-lay method.  
     
     
         2 . Method according to  claim 1 , characterised in that in addition to the strengthening by means of the hydrodynamic needling process, the composite non-woven fabric, which is formed solely according to the air-lay method, is treated by means of a thermal strengthening process.  
     
     
         3 . Method according to  claim 2 , characterised in that the term thermal strengthening includes the treatment of the non-woven fabric, which is formed solely according to the air-lay method, with every type of heat treatment, namely heat treatment, for example, with hot air, more especially through-ventilation, with infra-red, with calendering.  
     
     
         4 . Method according to  claim 2  or  3 , characterised in that the composite non-woven fabric, which is formed solely according to the air-lay method, is thermally treated before and/or after the water needling process for strengthening.  
     
     
         5 . Method according to one of the claims  2 - 4 , characterised in that the thermal strengthening together with the drying of the non-woven fabric, which is formed solely according to the air-lay method, is executed after the water needling process.  
     
     
         6 . Method according to one of claims  2 - 5 , characterised in that at the end of the strengthening process, the composite non-woven fabric, which is formed solely according to the air-lay method, is calibrated again.  
     
     
         7 . Method according to one of claims  1 - 6 , characterised in that the hydrodynamic treatment is executed on both sides of the composite non-woven fabric, which is formed solely according to the air-lay method.  
     
     
         8 . Device for executing the method in accordance with one of claims  1 - 7 , comprising the following disposed one after the other in a line 
 a) at least three moulding heads working according to the air-lay method, one for the first layer made of thermally activatable fibres with a fibre length from 8 to 10 mm maximum, one for the pulp and one for the top surface layer again for the thermally activatable fibres with a fibre length of from 8 to 10 mm maximum, and a    b) non-woven fabric strengthening unit, which comprises a hydrodynamic needling device ( 6 ,  7 ) and a drier ( 8 ).    
     
     
         9 . Device according to  claim 8 , characterised in that upstream of the device for the hydrodynamic needling of a composite non-woven fabric, which is formed solely according to the air-lay method, 
 c) is disposed a device ( 5 ) for the thermal strengthening.    
     
     
         10 . Device according to  claim 8  or  9 , characterised in that downstream of the device for the hydrodynamic needling of a composite non-woven fabric, which is formed solely according to the air-lay method, 
 d) is disposed a device ( 8 ) for the thermal strengthening.  
 
     
     
         11 . Device according to  claim 10 , characterised in that the device ( 8 ) for the thermal strengthening of a composite non-woven fabric, which is formed solely according to the air-lay method, is provided after the hydrodynamic needling initially for the drying of the non-woven fabric.  
     
     
         12 . Device according to one of claims  8 - 11 , characterised in that a calibrating device ( 9 ) is provided as the last unit for treating the composite non-woven fabric, which is formed solely according to the air-lay method.  
     
     
         13 . Multi-layered composite non-woven fabric comprising two outer layers, which are formed in accordance with the air-lay method from fusion adhesive fibres, which are from 8 to 10 mm maximum in length, such as more especially double component fibres or and other fibres, such as high polymer fibres, between which layers is laid a further layer made of super-absorbent pulp, which is also produced according to the air-lay method, wherein this composite non-woven fabric, which is formed solely according to the air-lay method, is strengthened by means of the hydrodynamic needling.