Formation of sheet material using hydroentanglement

Abstract

A method is described for forming reconstituted leather sheet material from a mixture of base fibres, such as leather fibres, and bi-component synthetic fibres which have outer layers which melt at a lower temperature than their inner cores. The fibres are mixed, formed into a web and then heated so that the synthetic fibres fuse together to form a network within the web. The base fibres are then tangled, whilst constrained by the network, preferably using hydroentanglement. A high quality reconstituted leather sheet material is thus produced.

1 . A method of forming a reconstituted leather sheet material from a mixture of fibres comprising predominantly waste leather base fibres and additional synthetic bicomponent fibres, said bicomponent fibres having outer meltable layers comprising the steps of:
 forming the waste leather base fibres and additional synthetic fibres into a web or webs,   distributing the web or webs onto a driven porous carrier,   heating the outer layers of the bicomponent fibres to melt so as to cause such fibres to fuse together at intersections to form a network within the web, and   
       subjecting the web or webs to hydroentanglement using high pressure jets of liquid whereby the high pressure jets penetrate deeply into the web or webs to entangle the waste leather fibres with each other while constrained by the network and wherein a water receiving structure is provided to remove bounced back liquid, the network comprising a minor proportion by weight of the sheet material, wherein the hydroentanglement procedure at least partially disrupts the fused network intersections. 
     
     
         2 . The method according to claim  37  wherein the leather base fibres have a maximum fibre length of 6 mm. 
     
     
         3 . The method according to  claim 1  wherein at least 90% of the bicomponent additional synthetic fibres have a maximum fibre length of 10 mm. 
     
     
         4 . The method according to  claim 1  wherein the bicomponent additional synthetic fibres constitute less than about 10% of the weight of the formed sheet material. 
     
     
         5 . The method according to  claim 4  wherein the bicomponent additional synthetic fibres constitute up to about 5% of the weight of the formed sheet material. 
     
     
         6 . The method according to  claim 1  wherein the additional synthetic bicomponent fibres have one or more outer layers with a melting point lower than the melting point of an inner core thereof. 
     
     
         7 . The method according to  claim 6  wherein the one or more of the outer layers are polyethylene and the inner core is polyester or polypropylene. 
     
     
         8 . The method according to  claim 1  wherein the bicomponent additional synthetic fibres have a denier in the range of 1.7 to 3.0 dtex. 
     
     
         9 . The method according to  claim 1  wherein the mixture of fibres also includes further synthetic fibres which are not melted to cause fusion together. 
     
     
         10 . The method according to  claim 10  wherein the further synthetic fibres have a denier less than 1.0 dtex. 
     
     
         11 . The method according to  claim 9  wherein the further synthetic fibres comprise less than 20% by weight of the reconstituted leather sheet material. 
     
     
         12 . The method according to  claim 1  wherein the leather fibres have lengths of less than 3 mm. 
     
     
         13 . The method according to  claim 1  wherein the network is predominantly open and solid parts of the network comprise a minor proportion of its structure. 
     
     
         14 . The method according to  claim 1  further comprising a fabric layer. 
     
     
         15 . The method according to  claim 14  wherein the leather fibres are caused to penetrate the fabric layer. 
     
     
         16 . The method according to  claim 1  wherein the bicomponent fibres constitute 2 to 10% of the weight of the reconstituted leather sheet material formed by said method. 
     
     
         17 . The method according to  claim 1  wherein the hydroentanglement is performed using high pressure jets of liquid in multiple passes. 
     
     
         18 . The method according to  claim 1  wherein the outer meltable layers of the bicomponent fibres are melted by passing hot air through the web. 
     
     
         19 . The method according to  claim 18  wherein the web is held between porous belts during passage of the hot air through the web. 
     
     
         20 . The method according to  claim 1  wherein an outer surface of the entangled web is subjected to heat to melt said bicomponent fibres at said outer surface.