Polyisoprene articles and process for making the same

Abstract

The invention disclosed herein relates to an improved process for making elastomeric polyisoprene articles. In particular, the process of the invention is a system which produces synthetic polyisoprene articles exhibiting tensile strength properties similar to that of solvent-based processes using natural rubber latex. The process comprises an accelerator composition at the pre-cure stage comprising a dithiocarbamate, a thiazole and a guanidine compound. In a preferred embodiment, the accelerator composition comprises zinc diethyldithiocarbamate (ZDEC), zinc 2-mercaptobenzothiazole (ZMBT) and diphenyl guanidine (DPG), in conjunction with a stabilizer, such as sodium caseinate. The invention also includes an elastomeric polyisoprene product made by the process, such as a surgeon's glove.

1 . A polyisoprene latex composition comprising:
 a dithiocarbamate compound;   a thiazole compound;   a guanidine compound; and   a stabilizer.   
   
   
       2 . The latex composition of  claim 1  wherein the latex composition comprises:
 zinc diethyldithiocarbamate;   zinc 2-mercaptobenzothiazole;   diphenyl guanidine; and   sodium caseinate.   
   
   
       3 . A synthetic elastomeric article consisting of a composition comprising a polyisoprene, wherein polyisoprene is the only polymer in the composition, and wherein the article has a tensile strength of greater than about 3000 psi as measured in accordance with ASTM D412, said article being prepared by a process comprising the steps of:
 a) preparing a polyisoprene latex composition comprising a polymer consisting of isoprene monomers, wherein the polyisoprene latex composition comprises polyisoprene, an accelerator composition and a stabilizer, said accelerator composition comprising a dithiocarbamate, a thiazole compound and a guanidine compound;   b) dipping a former into said polyisoprene latex composition;   c) curing said polyisoprene latex composition on said former; and   d) leaching said cured polyisoprene latex composition in a water leaching tank.   
   
   
       4 . The article of  claim 3 , wherein the article is a glove. 
   
   
       5 . The article of  claim 3 , wherein the article is a condom. 
   
   
       6 . The article of  claim 3 , wherein the article is a probe cover. 
   
   
       7 . The article of  claim 3 , wherein the article is a catheter. 
   
   
       8 . The article of  claim 3 , wherein said accelerator composition comprises:
 zinc diethyldithiocarbamate;   zinc 2-mercaptobenzothiazole; and   diphenyl guanidine.   
   
   
       9 . The article of  claim 3 , wherein said stabilizer comprises a milk protein salt that is optionally present in the resulting synthetic elastomeric article. 
   
   
       10 . The article of  claim 3 , wherein said stabilizer comprises sodium caseinate that is optionally present in the resulting synthetic elastomeric article. 
   
   
       11 . The article of  claim 3 , wherein said accelerator composition comprises:
 a) a dithiocarbamate compound, in an amount ranging from 0.50 phr to about 1.00 phr per 100.00 phr polyisoprene of the compounded latex composition;   b) a thiazole compound, in an amount ranging from 0.50 phr to about 1.00 phr per 100.0 phr polyisoprene of the compounded latex composition; and   c) guanidine compound, in an amount ranging from 0.50 phr to about 1.00 phr per 100.0 phr polyisoprene of the compounded latex composition.   
   
   
       12 . A glove consisting of a composition comprising a polyisoprene, wherein polyisoprene is the only polymer in the composition, and wherein the glove has a tensile strength of greater than 3000 psi as measured in accordance with ASTM D412, said glove being prepared from a polyisoprene latex composition comprising a polymer consisting of isoprene monomers, wherein the polyisoprene latex composition comprises polyisoprene, an accelerator composition comprising a dithiocarbamate compound, a thiazole compound, and a guanidine compound. 
   
   
       13 . The glove of  claim 12 , wherein said polyisoprene latex composition further comprises a milk protein salt that is optionally present in the resulting glove. 
   
   
       14 . The glove of  claim 13 , wherein said polyisoprene latex composition is stable to storage for up to at least 7 days prior to its use in the dipping and curing process. 
   
   
       15 . The glove of  claim 13 , wherein said milk protein salt is sodium caseinate. 
   
   
       16 . A synthetic elastomeric article consisting of a composition comprising a polyisoprene, wherein polyisoprene is the only polymer in the composition, said article being prepared by a process comprising the steps of:
 a) preparing a polyisoprene latex composition comprising a polymer consisting of isoprene monomers, wherein the polyisoprene latex composition comprises polyisoprene, an accelerator composition and a stabilizer, said accelerator composition comprising a dithiocarbamate compound, a thiazole compound and a guanidine compound;   b) dipping a former into said compounded latex composition; and   c) curing said compounded latex composition on said former.   
   
   
       17 . A glove consisting of a composition comprising a polyisoprene, wherein polyisoprene is the only polymer in the composition, said glove being prepared from a polyisoprene latex composition comprising a polymer consisting of isoprene monomers, wherein the polyisoprene latex composition comprises polyisoprene, an accelerator composition comprising a dithiocarbamate compound, a thiazole compound, and a guanidine compound.