Mold release and anti-blocking coating for powder-free natural or synthetic rubber articles

Abstract

The present invention is directed to a release composition for molds and formers used in the production of natural and synthetic latex articles. The release coating contains a water-borne, high Tg polymer formed from at least one hydrophobic monomer and at least one hydrophilic monomer, where the Tg of the polymer is at least −10° C. One advantage of the release composition is that it is compatible with a coagulant solution used in the formation of latex gloves. Articles formed using the release coating have good anti-blocking properties

What is claimed is:  
     
         1 . A mold or former for producing a natural or synthetic rubber article having on its surface a release composition comprising a water-borne high Tg polymer formed from: 
 (1) at least one hydrophobic monomer; and    (2) at least one hydrophilic monomer,    wherein said water-borne polymer has a Tg of at least −10° C.    
     
     
         2 . The mold or former of  claim 1  wherein said water-borne polymer comprises an emulsion polymer.  
     
     
         3 . The mold or former of  claim 1  wherein said hydrophobic monomer comprises styrene.  
     
     
         4 . The mold or former of  claim 1  wherein said hydrophilic monomer is an acid monomer.  
     
     
         5 . The mold or former of  claim 1  wherein said mold release composition further comprises a surfactant.  
     
     
         6 . The mold or former of  claim 1  wherein said release composition further comprises microspheres.  
     
     
         7 . The mold or former of  claim 1  wherein said release composition further comprises a dispersant.  
     
     
         8 . The mold or former of  claim 1  wherein said water-borne polymer further comprises a cross-linker.  
     
     
         9 . The mold or former of  claim 1  wherein said release composition further comprises a rheology modifier.  
     
     
         10 . The mold or former of  claim 1  wherein said release composition further comprising a coagulant.  
     
     
         11 . The mold or former of  claim 1  wherein said high Tg polymer comprises: 
 a) from 20 to 35 percent by weight of methyacrylic acid;  
 b) from 65 to 80 percent by weight of styrene; and  
 c) from 0.5 to 1.5 percent by weight of a crosslinker.  
 
     
     
         12 . The mold or former of  claim 1  wherein said release composition is free of silicon compounds.  
     
     
         13 . An article comprising a formed natural or synthetic rubber article having thereon a coating composition comprising a water-borne high Tg polymer formed from: 
 (1) at least one hydrophobic monomer; and    (2) at least one hydrophilic monomer,    wherein said water-borne polymer has a Tg of at least −10° C.    
     
     
         14 . The article of  claim 12  wherein said article is powder-free.  
     
     
         15 . A process for making a glove comprising: 
 (a) immersing a glove former in a coagulant solution containing a release composition comprising a water-borne polymer with Tg of at least −10° C. formed from at least one hydrophobic monomer, and at least one hydrophilic monomer, producing a coated former;    (b) immersing said coated mold into a natural rubber latex to coat the former with said latex;    (c) immersing the latex coated former into a inner surface coating composition;    (d) curing the latex in an oven; and    (e) removing the finished glove from the former.    
     
     
         16 . The process of  claim 14  wherein step (a) comprises two separate steps comprising: 
 a.1) immersing said ceramic former into said water-borne polymer release composition; and  
 a.2) immersing said release coated ceramic former into a coagulant solution.  
 
     
     
         17 . The process of  claim 14  wherein said the latex coated former of step (b) is leached in water prior to step (c).  
     
     
         18 . A release composition comprising: 
 a) a water-borne high Tg polymer formed from at least one hydrophobic monomer; and at least one hydrophilic monomer, wherein said water-borne polymer has a Tg of at least −10° C.;    b) a coagulant.    
     
     
         19 . The composition of  claim 17  wherein said coagulant is a calcium salt.  
     
     
         20 . The composition of  claim 17  further comprising microspheres.  
     
     
         21 . The composition of  claim 17  further comprising a rheology modifier.  
     
     
         22 . The composition of  claim 17  further comprising a surfactant.