System and method for continuously manufacturing cured membranes
A process for the continuous production of cured rubber membrane, the process comprising (i) preparing a continuous stream of curable rubber composition; (ii) forming the continuous stream of curable rubber composition into a continuous green-rubber extrudate; (iii) curing the continuous green-rubber extrudate to form a continuous cured membrane; and (iv) fabricating the continuous cured membrane into rolls of cured membrane, where the curable rubber composition is characterized by at least one of a t90 at 190° C. of from about 1 to about 12 minutes and a T5 at 135° C. of from about 5 to about 20 minutes.
1 . A process for the continuous production of cured rubber membrane, the process comprising:
(i) forming a first composition including ethylene-propylene-diene rubber;
(ii) mixing the first composition under high shear and increasing the temperature of the first composition to a temperature of about 130 to about 175° C.;
(iii) cooling the first composition to a temperature of about 70 to about 130° C.;
(iv) after cooling the first composition, adding a curative to the first composition to thereby form a continuous stream of curable rubber composition, where the curative includes sulfur;
(v) after adding a curative, increasing the temperature of the continuous stream of curable rubber composition to a temperature of about 135 to about 165 C;
(vi) after increasing the temperature of the continuous stream of curable composition, removing volatiles from the continuous stream of curable composition;
(vii) forming the continuous stream of curable rubber composition into a continuous green-rubber extrudate;
(viii) curing the continuous green-rubber extrudate to form a continuous cured membrane; and
ix) fabricating the continuous cured membrane into rolls of cured membrane, where the curable rubber composition is characterized by at least one of a too at 190° C. of from about 1 to about 12 minutes and a T5 at 135° C. of from about 5 to about 20 minutes.
2 . The process of claim 1 , further comprising removing volatiles from the first composition prior to cooling the first composition.
3 . The process of claim 1 , wherein the curable composition includes a benzothiazole sulfonamide and a thiuram sulfide in the absence of a thiazole.
4 . The process of claim 1 , wherein the curable composition includes carbon black and/or wherein the curable composition includes silica and a coupling agent.
5 . The process of claim 2 , wherein adding a curative includes introducing sulfur to a continuous mixing and conveying apparatus that contains the continuous stream of curable rubber composition, and wherein removing volatiles from the continuous stream of curable composition takes place outside of the mixing and conveying apparatus.
6 . The process of claim 2 , wherein removing volatiles takes place at reduced pressure.