Thermal liquids providing glass corrosion protection especially for solar systems

Abstract

A heat transfer liquid concentrate comprises, in addition to at least one glycol, a) from 0.05 to 10, preferably from 0.1 to 5, % by weight of one or more aliphatic amines of the formula (I),  where R 1 to R 3 may be identical or different and are hydrogen, optionally branched C 1 -C 9 -alkyl or C 1 -C 9 -hydroxyalkyl, b) from 0.005 to 3, preferably from 0.01 to 1, % by weight of one or more silicates which may have been stabilized, c) from 0 to 3% by weight of one or more corrosion inhibitors selected from the group consisting of the hydrocarbon-triazoles and of the hydrocarbon-thiazoles, d) from 0 to 5% by weight of one or more alkali metal, ammonium or substituted ammonium molybdates and e) from 0 to 1% by weight of one or more polymeric hard water stabilizers. The concentrates, if required after prior dilution with water, are particularly suitable for use in solar plants in which a heat transfer liquid is in direct contact with the glass of the solar plant.

1 - 18 . (canceled)  
   
   
       19 . A heat transfer liquid concentrate comprising, in addition to at least one glycol, 
 from 0.05 to 10% by weight of one or more aliphatic amines of the general formula (I),                          where R 1  to R 3  may be identical or different and are hydrogen, straight-chain or branched C 1 -C 9 -alkyl or C 1 -C 9 -hydroxyalkyl,    from 0.005 to 3% by weight of one or more silicates which may have been stabilized,    from 0 to 3% by weight of one or more corrosion inhibitors selected from the group consisting of the hydrocarbon-triazoles and of the hydrocarbon-thiazoles,    from 0 to 5% by weight of one or more alkali metal, ammonium or substituted ammonium molybdates and    from 0 to 1% by weight of one or more polymeric hard water stabilizers;    and wherein the concentrate contains no borate.    
   
   
       20 . The concentrate as claimed in  claim 19 , wherein the component c) is present in an amount of from 0.01 to 3% by weight.  
   
   
       21 . The concentrate as claimed in  claim 20 , wherein the component c) is present in an amount of from 0.05 to 1% by weight.  
   
   
       22 . The concentrate as claimed in  claim 19 , wherein, in the amine of the formula (I), R 1  to R 3  are selected from hydrogen, linear and branched alkyl radicals with 1 to 9 carbon atoms and linear and branched alkyl radicals with 1 to 9 carbon atoms with at least one hydroxyl substituent.  
   
   
       23 . The concentrate as claimed in  claim 22 , wherein R 1  to R 3  are selected from hydrogen, linear and branched alkyl radicals with 3 or 4 carbon atoms and linear and branched alkyl radicals with 3 or 4 carbon atoms which have at least one hydroxyl substituent.  
   
   
       24 . The concentrate as claimed in  claim 19 , wherein the amine carries an alkyl radical having at least one hydroxyl substituent.  
   
   
       25 . The concentrate as claimed in  claim 19 , wherein the silicate of component b) is stabilized.  
   
   
       26 . The concentrate as claimed in  claim 25 , wherein the silicate is stabilized by organosilicophosphonates and/or organosilicosulfonates.  
   
   
       27 . The concentrate as claimed in  claim 19 , wherein component b) contains an alkali metal silicate, the silicate being stabilized, if required, with orthophosphates.  
   
   
       28 . The concentrate as claimed in  claim 19 , wherein component c) contains a mixture of at least two hydrocarbon-thiazoles, a mixture of at least one hydrocarbon-triazole and one hydrocarbon-thiazole or a mixture of at least two different hydrocarbon-triazoles.  
   
   
       29 . The concentrate as claimed in  claim 19 , wherein component d) contains sodium molybdate.  
   
   
       30 . The concentrate as claimed in  claim 19 , wherein component e) contains at least one hard water stabilizer based on one or more compounds from the group consisting of polyacrylic acid, polymaleic acid, acrylic acid/maleic acid copolymers, polyvinylpyrrolidone, polyvinylimidazole, vinylpyrrolidone/vinylimidazole copolymers and copolymers of unsaturated carboxylic acids and olefins.  
   
   
       31 . The concentrate as claimed in  claim 19 , wherein furthermore one or more soluble magnesium salts of organic acids, one or more hydrocarbazoles and/or one or more quaternized imidazoles are present.  
   
   
       32 . The concentrate as claimed in  claim 19 , wherein the pH is from 6 to 11.  
   
   
       33 . The concentrate as claimed in  claim 19 , wherein the freezing point depressant contains at least one compound from the group consisting of the lower alkylene glycols and derivatives thereof, higher glycols and glycol ethers, monoethers of glycols, 1,3-propanediol and glycerol.  
   
   
       34 . The concentrate as claimed in  claim 19 , wherein the freezing point depressant is present in the concentrate in an amount of >75% by weight.  
   
   
       35 . The concentrate as claimed in  claim 19 , wherein the freezing point depressant comprises 1,2-propylene glycol or a mixture of 1,2-propylene glycol with one or more other polyalcohols, the mixture containing at least 85% by weight of 1,2-propylene glycol.  
   
   
       36 . A ready-to-use aqueous heat transfer liquid comprising water and from 10 to 90% by weight of a heat transfer liquid concentrate as claimed in  claim 19 .  
   
   
       37 . A method of transferring heat in a solar plant comprising using in the solar plant a heat transfer liquid concentrate as claimed in  claim 19 .  
   
   
       38 . The method as claimed in  claim 37 , comprising bringing the heat transfer liquid concentrate into direct contact with glass of the solar plant.  
   
   
       39 . A method of transferring heat in a solar plant comprising using in the solar plant a ready-to-use heat transfer liquid as claimed in  claim 36 .  
   
   
       40 . The method as claimed in  claim 39 , comprising bringing the heat transfer liquid concentrate into direct contact with glass of the solar plant.