COOLANT CONCENTRATE CONTAINING SILICATE

Abstract

The invention relates to a silicate-containing coolant concentrate, including at least one freezing-point lowering liquid, at least one mixture of at least two saturated, aliphatic dicarboxylic acids, at least one saturated aliphatic or hydroxyl-containing aromatic mono-carboxylic acid, at least one azole, at least one stabilizing silicate, at least one phosphonocarboxylic acid, and at least one heteropoly complex anion from the group IIIA to VIA of the periodic table of the elements.

Claims

1. A silicate-containing coolant concentrate consisting essentially of: at least one freezing-point lowering liquid, at least one mixture of at least two saturated, aliphatic dicarboxylic acids, at least one saturated aliphatic or hydroxyl-containing aromatic mono-carboxylic acid, at least one azole, at least one stabilizing silicate, at least one phosphonocarboxylic acid, and at least one heteropoly complex anion from the group IIIA to VIA of the periodic table of the elements.

2. The coolant concentrate according to claim 1, wherein the freezing point lowering liquid is a compound of the group including alkylene glycol, alkylene glycol ether, glycol ether, glycerin, or of a mixture of two or more of these compounds.

3. The coolant concentrate according to claim 1, wherein the dicarboxylic acids have a chain length between four and 12 carbon atoms.

4. The coolant concentrate according to claim 1, wherein the dicarboxylic acids and/or the monocarboxylic acids are present in the form of their alkaline or alkaline earth metal salts.

5. The coolant concentrate according to claim 1, wherein the heteropoly complex anion is a molybdate anion.

6. The coolant concentrate according to claim 1, wherein the heteropoly complex anion is an anion from the group including phosphomolybdates, silicon molybdates, manganese molybdates, silicon tungstates, tellurium molybdates, arsenic molybdates, or a mixture thereof.

7. The coolant concentrate according to claim 1, wherein the heteropoly complex anion is a phosphomolybdate of the formula (PMo.sub.12O.sub.12O.sub.40).sup.3.

8. The coolant concentrate according to claim 1, wherein the phosphonocarboxylic acid is 2-phosphonobutane-1,2,4-tricarboxylic acid.

9. The coolant concentrate according to claim 1, wherein a pH-adjusting component is contained.

10. The coolant concentrate according to claim 1, wherein the pH value of the concentrate is in the range between 6 and 10.

11. The coolant concentrate according to claim 1, including more than 90 weight percent with respect to the total amount of the concentrate of at least one freezing point lowering liquid, 1.5 to 5 weight percent with respect to the total amount of the concentrate of at least one mixture of at least two saturated aliphatic dicarboxylic acids, 0.1 to 1 weight percent with respect to the total amount of the concentrate of at least one saturated, aliphatic or hydroxyl-containing aromatic monocarboxylic acid, 0.05 to 0.5 weight percent with respect to the total amount of the concentrate of at least one azole, 0.01 to 0.06 weight percent with respect to the total amount of the concentrate of at least one stabilizing silicate, 0.01 to 1 weight percent with respect to the overall amount of the concentrate of at least one phosphonocarboxylic acid, and 0.01 to 1 weight percent with respect to the total amount of the concentrate of at least one heteropoly complex anion from the group IIIA to VIA of the periodic table of the elements.

12. A method of cooling a combustion engine, a solar plant or a refrigerator having a coolant system, the method comprising: providing the coolant concentrate according to claim 1; and applying the coolant concentrate to the coolant system of the combustion engine, the solar plant or the refrigerator.

Description

DETAILED DESCRIPTION

[0065] Hereinafter, the invention will be described in greater detail by means of examples.

[0066] The silicon-containing, nitride-, nitrate-, borate- and amine-free coolant concentrate for combustion engines described here, based on a mixture of carboxylic acids, azoles, phosphono-carboxylic acid, as well as at least one heteropoly complex anion from the group IIIA to VIA of the periodic table of the elements, alkylene glycols, or their derivatives.

[0067] Further possible ingredients of the silicate-containing coolant concentrate are, for example, sabit and/or thiopropionic acid, which function as copper inhibitors.

[0068] Silicate provides an excellent corrosion protection in particular for aluminum and its alloys. Thus, in silicate-containing coolants, it is to be prevented that a reduction of the silicate or silicon content occurs, since otherwise the corrosion protection is affected.

[0069] The coolant concentrate has an increased thermal stability and an increased compatibility towards flux residues.

[0070] Comparative Test:

[0071] Modified ASTM D4340 corrosion tests were performed with various silicate-containing coolants. In each case, 250 ml coolant were mixed with in each case 250 ml NOCOLOK water (2000 mg/l), the initial silicon content was determined through AAS (atomic absorption spectroscopy), and, subsequently, the coolants were heated to 150 C. for 8 hours in the test apparatus, which simulates a hot surface of a cylinder head made of aluminum in a combustion engine. Once the coolants reached room temperature again, 5 ml of each coolant was filtrated with a 0.45 l filter and, subsequently, the silicon content was determined again. The following table shows representative examples for the coolant compositions as well as the decrease in the silicate content on percent over the test period of 8 h.

TABLE-US-00001 Coolant 1 Coolant 2 Coolant 3 Coolant 4 (in weight (in weight (in weight (in weight Component percent) percent) percent) percent) Monoethylene glycol 91.02 90.64 93.34 92.24 Caustic potash (45%) 4.62 5.60 3.00 3.40 2-ethyl-hexane acid 3.20 3.00 Sebacic acid 3.00 0.40 0.20 Hydroxy-benzoic acid 0.40 Adipic acid 0.30 3.00 0.30 Isononanoic acid 0.40 Tolyltriazole 0.20 0.10 0.10 Benzotriazole 0.20 0.10 Heteropoly complex 0.30 0.30 anion Sodium metasilicate 0.16 0.16 0.16 0.16 pentahydrate Silicon content 117 124 120 112 (ppm, start) Silicon content 100 32 25 90 (ppm, end) Si (%) 15 75 80 20

[0072] All coolants shown in the table contain the same amount of silicon in the form of alkaline metal silicates, i.e. 0.16 weight percent. Coolants 1 and 4 are silicate-containing coolant concentrates according to the present invention.

[0073] As can be seen in the table, the reduction of the silicon content in the coolant ( Si [%]), and thus the reduction of the silicate content in the coolant, is significantly smaller in coolants 1 and 4 than in coolants 2 and 3, which do not contain a heteropoly complex anion.