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 reconstituted leather sheet material having a leather-like feel, the reconstituted leather sheet material being formed by a method comprising the steps of:
 evenly distributing and compressing a mixture of predominantly waste leather base fibres and additional synthetic fibres to form a web, wherein the additional synthetic fibres have meltable surface layers and the base waste leather fibres comprise leather fibres having fibrillated branches,   heating the web to melt the surface layers of the additional synthetic fibres so as to cause such fibres to fuse together at intersections to form fused network intersections within the web mixture, and   subjecting the web mixture to successive hydroentanglement stages to entangle the waste leather fibres with each other while initially constrained by the network, such that the increase in tensile strength arising from the hydroentanglement of the fibers within the web is greater than the tensile strength of the web prior to hydroentanglement.   
     
     
         2 . A method of forming a reconstituted leather sheet material having a leather-like feel, comprising the steps of:
 evenly distributing and compressing a mixture of predominantly waste leather base fibres and additional synthetic fibres to form a web, wherein the additional synthetic fibres have meltable surface layers and the base waste leather fibres comprise leather fibres having fibrillated branches,   heating the web to melt the surface layers of the additional synthetic fibres so as to cause such fibres to fuse together at intersections to form fused network intersections within the web mixture, and   subjecting the web mixture to successive hydroentanglement stages to entangle the waste leather fibres with each other while initially constrained by the network, such that the increase in tensile strength arising from the hydroentanglement of the fibers within the web is greater than the tensile strength of the web prior to hydroentanglement.   
     
     
         3 . The method according to  claim 2 , wherein the waste leather base fibres have a maximum fibre length of 6 mm. 
     
     
         4 . The method according to  claim 2 , wherein at least 90% of the additional synthetic fibres have a maximum fibre length of 10 mm. 
     
     
         5 . The method according to  claim 2 , wherein the additional synthetic fibres constitute less than about 10% of the weight of the formed sheet material. 
     
     
         6 . The method according to  claim 5 , wherein the additional synthetic fibres constitute up to about 5% of the weight of the formed sheet material. 
     
     
         7 . The method according to  claim 2 , wherein the additional synthetic fibres each has an inner core surrounded by a respective meltable outer surface layer that is formed by one or more outer layers having a melting point lower than the melting point of the inner core. 
     
     
         8 . The method according to  claim 7 , wherein the one or more of the outer layers are polyethylene and the inner core is polyester or polypropylene. 
     
     
         9 . The method according to  claim 2 , wherein the additional synthetic fibres have a denier in the range of 1.7 to 3.0 dtex. 
     
     
         10 . The method according to  claim 2 , wherein the mixture of fibres also includes further synthetic fibres which are not melted to cause fusion together. 
     
     
         11 . The method according to  claim 2 , wherein the further synthetic fibres have a denier less than 1.0 dtex. 
     
     
         12 . The method according to  claim 10 , wherein the further synthetic fibres comprise less than 20% by weight of the reconstituted leather sheet material. 
     
     
         13 . The method according to  claim 2 , wherein the leather base fibres have lengths of less than 3 mm. 
     
     
         14 . The method according to  claim 2 , wherein the additional synthetic fibres constitute no more than 2% of the weight of the web. 
     
     
         15 . The method according to  claim 2 , further comprising a fabric layer, and the leather fibres are caused to penetrate the fabric layer. 
     
     
         16 . The method according to  claim 2 , wherein the additional synthetic fibres constitute 2 to 10% of the weight of the reconstituted leather sheet material formed by said method. 
     
     
         17 . The method according to  claim 2 , wherein the hydroentanglement is performed using hydroentangling jets of liquid in multiple passes. 
     
     
         18 . The method according to  claim 17 , further comprising using a collection device positioned adjacent the hydroentangling jets and a surface of the web to collect rebound liquid from the jets that rebounds off the surface of the web, such collection occurring before the liquid falls back onto the surface of the web thereby to minimize the amount of rebound liquid that falls back on the surface of the web. 
     
     
         19 . The method according to  claim 2 , wherein the outer meltable surface layers of the additional synthetic fibres are melted by passing hot air through the web. 
     
     
         20 . The method according to  claim 19 , wherein the web is held between porous belts during passage of the hot air through the web. 
     
     
         21 . The method according to  claim 2 , wherein an outer surface of the body is subjected to heat to melt said additional synthetic fibres at said outer surface.