Coolant comprising azole derivatives for cooling systems in fuel-cell drives

Abstract

An antifreeze concentrate for cooling systems in fuel-cell drives which gives ready-to-use aqueous coolant compositions having a conductivity of at most 50 μS/cm, based on alkylene glycols or derivatives thereof and containing one or more five-membered heterocyclic compounds (azole derivatives) having 2 or 3 hetero atoms from the group consisting of nitrogen and sulfur, which contain no or at most one sulfur atom and which may carry a fused aromatic or saturated six-membered ring.

1 . An antifreeze concentrate for cooling systems in fuel-cell drives which gives a ready-to-use aqueous coolant composition having a conductivity of at most 50 μS/cm, based on alkylene glycols or derivatives thereof and containing one or more five-membered heterocyclic compounds (azole derivatives) having 2 or 3 heteroatoms from the group consisting of nitrogen and sulfur, which contain no or at most one sulfur atom and which may carry a fused aromatic or saturated six-membered ring, and additionally orthosilicates which give a ready-to-use aqueous coolant composition having a silicon content of from 2 to 2000 ppm by weight.  
   
   
       2 . An antifreeze concentrate for cooling systems in fuel-cell drives as claimed in  claim 1 , comprising a total of from 0.05 to 5% by weight of the azole derivatives.  
   
   
       3 . An antifreeze concentrate for cooling systems in fuel-cell drives as claimed in  claim 1  or  2 , comprising, as azole derivatives, benzimidazole, benzotriazole, tolutriazole and/or hydrogenated tolutriazole.  
   
   
       4 . An antifreeze concentrate for cooling systems in fuel-cell drives as claimed in any one of  claims 1  to  3 , in which the alkylene glycol employed is monoethylene glycol.  
   
   
       5 . An antifreeze concentrate for cooling systems in fuel-cell drives as claimed in any one of  claims 1  to  4 , which gives, on dilution with ion-free water, a ready-to-use aqueous coolant composition having a conductivity of at most 50 μS/cm and which essentially consists of 
 (a) from 10 to 90% by weight of alkylene glycols or derivatives thereof,    (b) from 90 to 10% by weight of water,    (c) from 0.005 to 5% by weight of the azole derivatives, and    (d) orthosilicates in an amount which gives a ready-to-use aqueous coolant composition having a silicon content of from 2 to 2000 ppm by weight.    
   
   
       6 . A ready-to-use aqueous coolant composition for cooling systems in fuel-cell drives which essentially consists of 
 (a) from 10 to 90% by weight of alkylene glycols or derivatives thereof,    (b) from 90 to 10% by weight of water,    (c) from 0.005 to 5% by weight of the azole derivatives, and    (d) orthosilicates in an amount which gives a ready-to-use aqueous coolant composition having a silicon content of from 2 to 2000 ppm by weight,    obtainable by dilution of an antifreeze concentrate as claimed in any one of  claims 1  to  4  with ion-free water.    
   
   
       7 . The use of a five-membered heterocyclic compound (azole derivative) having 2 or 3 heteroatoms from the group consisting of nitrogen and sulfur, which contains no or at most one sulfur atom and which may carry a fused aromatic or saturated six-membered ring, together with orthosilicates for the preparation of an antifreeze concentrate for cooling systems in fuel-cell drives based on alkylene glycols or derivatives thereof.  
   
   
       8 . The use of an antifreeze concentrate as claimed in  claim 7  for the preparation of a ready-to-use aqueous coolant composition having a conductivity of at most 50 μS/cm for cooling systems in fuel-cell drives.