Heat resistant ethylene vinyl acetate copolymer composition and process for its production

Abstract

Disclosed herein are curable heat resistant ethylene vinyl acetate copolymer-polyamide blend compositions, wherein the ethylene vinyl acetate copolymer has a melting peak temperature of 100° C. or less. The blend compositions comprise 0.1 to 10 weight percent dispersed polyamide, and may be cured to form articles having improved heat resistance while maintaining the desirable physical properties of unmodified, cured ethylene vinyl acetate articles.

What is claimed is: 
     
         1 . A heat resistant curable ethylene vinyl acetate (EVA) copolymer-polyimide blend composition comprising:
 (A) from about 99.9 wt % to about 90 wt % of an EVA component selected from one or more of
 (i) amorphous EVA copolymers; 
 (ii) EVA copolymers wherein each has melting peak temperatures of 100° C. or less; or 
 (iii) combinations thereof; 
   (B) from about 0.1 wt % to about 10 wt % of one or more polyamides;   wherein the weight percent of the polyamides and the EVA component are based on the total combined amount of EVA component and polyamides in the blend, and the blend composition has a Mooney viscosity determined according to ASTM D1646, ML 1+4 at 100° C. less than 200; and   (C) a peroxide curative.   
     
     
         2 . The composition of  claim 1  wherein each of the one or more EVA copolymer comprises from about 18 wt % to about 90 wt % of vinyl acetate based on the weight of the EVA. 
     
     
         3 . The composition of  claim 1  wherein the EVA component has a Mooney viscosity determined according to ASTM D1646, ML 1+4 at 100° C. of less than 120. 
     
     
         4 . The composition of  claim 1  wherein each of the one or more polyamides has a melting peak temperature of less than about 270° C. as determined according to ASTM D3418-08. 
     
     
         5 . The composition of  claim 4  wherein each of the one or more polyamides has a melting peak temperature of less than 160° C. 
     
     
         6 . The composition of  claim 1  wherein at least one of said one or more polyamides is selected from nylon 6, nylon 6/6 or combinations thereof. 
     
     
         7 . The composition of  claim 1  comprising from about 1 wt % to 5 wt % of the one or more polyamides. 
     
     
         8 . The composition of  claim 1  wherein said composition has an increase in torque MH-ML of at least 2.5 dN-m when tested in a rotorless cure meter at conditions of 177° C. for 24 minutes per ASTM D5289-07a. 
     
     
         9 . An article produced from the blend composition of  claim 1 . 
     
     
         10 . The article of  claim 9  wherein said article is wire or cable jacketing, spark plug boot, hose, belt, molded boot, seal, gasket, tubing, hose or grommet. 
     
     
         11 . A process for producing the composition of  claim 1  comprising:
 (A) providing said EVA component; 
 (B) providing said one or more polyamides; and 
 (C) mixing the EVA component and polyamide at
 (i) a temperature greater than the melting peak temperatures of the one or more polyamides; and 
 (ii) where the EVA component exhibits a melting peak temperature, at a temperature greater than the melting peak temperatures of the EVA copolymers; 
 
 thereby dispersing said polyamide in said EVA component to form an EVA copolymer-polyamide blend composition 
 (D) optionally, cooling the EVA copolymer-polyamide blend composition of (C) to a temperature of less than 160° C.; and 
 (E) adding a peroxide curative at a temperature less than 160° C. to form the curable ethylene vinyl acetate (EVA) copolymer-polyamide composition. 
 
     
     
         12 . A process for production of the composition of  claim 1 , the process comprising the steps:
 (A) providing the EVA component; and   (B) providing the one or more polyamides having melting peak temperatures less than 160° C.; and   (C) providing a peroxide curative; and   (D) mixing the EVA component, the one or more polyamides, and peroxide together
 (i) at a temperature of 160° C. or less, and greater than the melting peak temperatures of the one or more polyamides; and 
 (ii) where the EVA component exhibits a melting peak temperature, at a temperature greater than the melting peak temperatures of the EVA component, 
   thereby dispersing the peroxide and 0.1 wt % to 10 wt % polyamide in the one or more EVA component;   wherein the weight percent polyamide is based on the total amount of EVA component and polyamide in the blend,   thereby producing a curable EVA copolymer-polyamide blend composition having a Mooney viscosity (ML1+4, 100° C.) according to ASTM D-1646 of less than 200.   
     
     
         13 . A process for production of the composition of  claim 1 , the process comprising the steps
 (A) providing the EVA component; and   (B) providing the one or more polyamides having one or more melting peak temperatures; and   (C) mixing the EVA component and the one or more polyamides at a temperature greater than the melting peak temperatures of the one or more polyamides and, where the EVA component has a melting peak temperature, at a temperature greater than the melting peak temperatures of the EVA component,   thereby dispersing up to 60 wt % polyamide in the one or more EVA component to form an intermediate blend composition;   wherein the weight percent polyamide is based on the total amount of EVA and polyamides in the blend and the blend has a Mooney viscosity (ML1+4, 100° C.) according to ASTM D-1646 of less than 200; and   (D) mixing the intermediate blend composition of (C) with an EVA component having melting peak temperatures of 100° C. or less to form an EVA copolymer-polyamide blend comprising 0.1 wt % to 10 wt % polyamide wherein the weight percent polyamide is based on the total amount of EVA and polyamide polymers in the blend, and the blend has a Mooney viscosity (ML1+4, 100° C.) according to ASTM D-1646 of less than 200; and   (E) adding a peroxide curative to the EVA copolymer-polyamide blend of (D) at a temperature less than 160° C. to form the curable blend composition.   
     
     
         14 . The process of  claim 11  in which the curable composition exhibits an increase in torque MH-ML of at least 2.5dN-m when tested in a rotorless cure meter at conditions of 177° C. for 24 minutes per ASTM D5289-07a. 
     
     
         15 . The process of  claim 12  in which the curable composition exhibits an increase in torque MH-ML of at least 2.5dN-m when tested in a rotorless cure meter at conditions of 177° C. for 24 minutes per ASTM D5289-07a. 
     
     
         16 . The process of  claim 13  in which the curable composition exhibits an increase in torque MH-ML of at least 2.5dN-m when tested in a rotorless cure meter at conditions of 177° C. for 24 minutes per ASTM D5289-07a. 
     
     
         17 . A process for a producing a cured article, the process comprising:
 (A) providing the heat resistant curable ethylene vinyl acetate (EVA) copolymer-polyamide blend composition of  claim 1 ;   (B) heating the blend composition, optionally in a mold of a desired article, to a temperature greater than 160° C. for at least one minute, thereby forming a cured article.