Making touch fasteners of multiple resins

Abstract

Touch fasteners with different portions having different material properties, and methods and apparatus for making such a product. In one embodiment, the fastener includes a cross-linkable polymer, and a first portion of the fastener is cross-linked and a second portion of the fastener is not cross-linked or is cross-linked to a degree less than said first portion. In another embodiment, the fastener is made in a continuous process on a rotating mold roll having a plurality of fastener element mold cavities extending into the mold roll from its outer circumferential surface. The method includes applying a first polymer to the mold roll and forcing some of the first polymer into the mold cavities, with some of the first polymer remaining on the surface of the mold roll in the form of a film having thickness; with a doctoring blade, removing at least some of the first polymer remaining on the surface of the mold roll to at least reduce the thickness of the film of the first polymer on the mold roll surface (in some cases, substantially all of the polymer on the mold roll surface is removed); and applying a second polymer to the mold roll, the second polymer being compatible with, and adhering to, the first polymer.

What is claimed is:  
     
         1 . A touch fastener comprising: 
 a sheet-form base portion; and    extending outwardly from, and integral with, the base portion, a plurality of molded fastener elements;    wherein the fastener comprises a cross-linkable polymer, and wherein a first portion of the fastener is more cross-linked than a second portion of the fastener.    
     
     
         2 . The touch fastener of    claim 1    wherein at least some of the fastener elements are cross-linked.  
     
     
         3 . The touch fastener of    claim 2    wherein said base portion is not cross-linked.  
     
     
         4 . The touch fastener of    claim 3    wherein said fastener elements comprise said cross-linkable polymer and said base portion comprises a non-cross-linkable polymer.  
     
     
         5 . The touch fastener of    claim 3    wherein said fastener elements and said base portion comprise said cross-linkable polymer.  
     
     
         6 . The touch fastener of    claim 3    wherein said base portion has a flexural modulus of less than about 80,000 psi.  
     
     
         7 . The touch fastener of    claim 1    wherein said cross-linkable polymer comprises a thermoplastic elastomer.  
     
     
         8 . The touch fastener of    claim 1    formed in a continuous length.  
     
     
         9 . The fastener of    claim 1    wherein said fastener elements are hook-shaped.  
     
     
         10 . The fastener of    claim 9    wherein said hook-shaped fastener elements are cross-linked.  
     
     
         11 . The fastener of    claim 10    wherein said fastener elements have a flexural modulus of at least 80,000 psi.  
     
     
         12 . A method of making a touch fastener, the method comprising: 
 (a) forming a sheet-form base portion from a cross-linkable polymer;    (b) forming a plurality of molded fastener elements extending outwardly from and integral with said sheet-form base portion, the molded fastener elements being formed from said cross-linkable polymer; and    (c) selectively cross-linking a first portion of the cross-linkable polymer while leaving a second portion of the cross-linkable polymer less cross-linked than said first portion.    
     
     
         13 . The method of    claim 12    wherein step (c) is performed with electron beam radiation.  
     
     
         14 . The method of    claim 12    wherein said polymer comprises a thermoplastic elastomer.  
     
     
         15 . The method of    claim 12    wherein the touch fastener further comprises a non-cross-linkable polymer.  
     
     
         16 . The method of    claim 15    wherein substantially all of the cross-linkable polymer is cross-linked.  
     
     
         17 . The method of    claim 15    further comprising coextruding said cross-linkable and non-cross-linkable polymers to form a sheet of molten polymer, and, in step (a), forming said touch fastener from said sheet.  
     
     
         18 . The method of    claim 12    wherein said touch fastener is formed entirely of a cross-linkable polymer, and a portion of the cross-linkable polymer corresponding to the first portion is selectively cross-linked in step (b).  
     
     
         19 . The method of    claim 12    wherein said fastener elements are hook-shaped.  
     
     
         20 . The method of    claim 19    wherein said hook-shaped fastener elements are cross-linked during step (b).  
     
     
         21 . The method of    claim 20    wherein at least part of said base portion is not cross-linked during step (b).  
     
     
         22 . A method of making a touch fastener, the method comprising: 
 (a) forming a preform product comprising a sheet-form base portion and a plurality of molded fastener elements extending outwardly from and integral with said sheet-form base portion, by 
 (a1) forming a first portion of the preform product from a cross-linkable polymer, and  
 (a2) joining the first portion to a second portion of the preform product formed from a second polymer; and  
   (b) at least partially cross-linking the first cross-linkable polymer of the preform product to form the touch fastener.    
     
     
         23 . A method of making a continuous fastener product having an array of fastener elements extending from a sheet-form base, the method comprising: 
 (a) providing a mold roll defining a plurality of fastener element mold cavities extending into the mold roll from the outer circumferential surface of the mold roll;    (b) applying a first polymer to a surface of the mold roll and forcing some of the first polymer into the mold cavities, with some of the first polymer remaining on the surface of the mold roll in the form of a film having thickness;    (c) with a doctoring blade, removing at least some of the first polymer remaining on the surface of the mold roll after step (b) from the surface of the mold roll to at least reduce the thickness of the film of the first polymer on the mold roll surface;    (d) applying a second polymer to the mold roll, the second polymer being compatible with the first polymer and adhering thereto;    (e) solidifying the first polymer in the mold cavities to form fastener elements; and    (f) removing the fastener elements from the mold cavities.    
     
     
         24 . The method of    claim 23    wherein, in step (c), substantially all of the first polymer that remains on the surface of the mold roll is removed.  
     
     
         25 . The method of    claim 23    wherein, after step (c), a portion of the film of first polymer remains on the surface of the mold roll.  
     
     
         26 . The method of    claim 23    wherein said first polymer is applied by an extruder.  
     
     
         27 . The method of    claim 26    wherein said second polymer is applied by an extruder.  
     
     
         28 . The method of    claim 23    wherein said first polymer is cross-linkable, the method further comprising, after step (f), cross-linking said first polymer.  
     
     
         29 . The method of    claim 23    wherein said first polymer is relatively harder than said second polymer.  
     
     
         30 . The method of    claim 23    wherein said first polymer is relatively stiffer than said second polymer.  
     
     
         31 . The method of    claim 23    further comprising, after step (d), bonding a third polymer to said second polymer.  
     
     
         32 . A method of making a continuous fastener product having an array of fastener elements extending from a sheet-form base, the method comprising: 
 (a) providing a mold roll defining a plurality of fastener element mold cavities extending into the mold roll from the outer circumferential surface of the mold roll;    (b) applying a first polymer to a surface of the mold roll and forcing some of the first polymer into the mold cavities, with some of the first polymer remaining on the surface of the mold roll in the form of a film having thickness;    (c) with a doctoring blade, removing at least some of the first polymer remaining on the surface of the mold roll after step (b) from the surface of the mold roll to at least reduce the thickness of the film of the first polymer on the mold roll surface;    (d) applying a tie layer to said mold roll, said tie layer being compatible with said first polymer and adhering thereto; and    (e) applying a second polymer to said tie layer.    
     
     
         33 . The method of    claim 32    wherein said first and second polymers are different materials.  
     
     
         34 . The method of    claim 32    wherein said tie layer comprises an adhesive.  
     
     
         35 . The method of    claim 32    wherein said tie layer comprises a polymer.