NOVEL COOLANTS WITH IMPROVED STORAGE STABILITY

Abstract

Coolants with increased activity against corrosion of aluminium and aluminium alloys and with improved storage stability, and corresponding coolant concentrates, are useful.

Claims

1-3: (canceled)

4: A coolant, comprising: (A) at least one glycol, (B) water, (C) at least one azole derivative, (D) at least one inorganic silicate, (E) optionally, at least one ene tertiary amine, (F) at least one carboxylic acid, (G) at least one silicophosphonate of the general structure (V) ##STR00008## wherein R.sup.5 is a bivalent organic residue, R.sup.6 independently of another is hydrogen, C.sub.1- to C.sub.4-alkyl, or hydroxy-C.sub.2- to C.sub.4-alkyl, and R.sup.7 is C.sub.1- to C.sub.4-alkyl, and (H) optionally, at least one further coolant additive.

5: The coolant according to claim 4, wherein the at least one glycol (A) is selected from the group consisting of monoethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, monopropylene glycol, dipropylene glycol, 1,3-propanediol, a higher poly alkylene glycol, an alkylene glycol ether, and glycerol.

6: The coolant according to claim 4, wherein the at least one azole derivative (C) is selected from the group consisting of benzimidazole, benzotriazole, tolutriazole, hydrogenated tolutriazole, (2-benzothiazylthio)acetic acid, and (2-benzothiazylthio) propionic acid.

7: The coolant according to claim 4, wherein the at least one inorganic silicate (D) is selected from the group consisting of an orthosilicate (SiO.sub.4.sup.4-), a metasilicate (SiO.sub.3.sup.2-), and a pyrosilicate (Si.sub.2O.sub.7.sup.6-).

8: The coolant according to claim 4, wherein the at least one carboxylic acid (F) is a mono- or dicarboxylic acid or a mixture thereof.

9: The coolant according to claim 4, wherein the at least one carboxylic acid (F) is a linear or branched monocarboxylic acid (F1).

10: The coolant according to claim 9, wherein the linear or branched monocarboxylic acid (F1) is selected from the group consisting of 2-ethylhexanoic acid and isononanoic acid.

11: The coolant according to claim 4, wherein the at least one carboxylic acid (F) is a linear or branched dicarboxylic acid (F2).

12: The coolant according to claim 11, wherein the linear or branched dicarboxylic acid (F2) is a selected from the group consisting of adipic acid, sebacic acid, azelaic acid, and dodecanedioic acid.

13: The coolant according to claim 4, wherein the at least one tertiary amine comprises a tertiary amine bearing at least one 2-hydroxyethyl- or 2-hydroxypropyl-group.

14: The coolant according to claim 4, wherein in the general structure (V), R.sup.5 is methylene, 1,2-ethylene, 1,2-propylene, 1,3-propylene, or 1,4-butylene.

15: The coolant according to claim 4, wherein in the general structure (V), R.sup.6 is hydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, 2-hydroxyethyl, or 2-hydroxypropyl.

16: The coolant according to claim 7, wherein the at least one inorganic silicate (D) is sodium metasilicate (Na.sub.2SiO.sub.3) or potassium metasilicate (K.sub.2SiO.sub.3).

17: The coolant according to claim 9, wherein the at least one carboxylic acid (F) is a branched aliphatic monocarboxylic acid with 6 to 12 carbon atoms.

18: The coolant according to claim 11, wherein the at least one carboxylic acid (F) is a linear aliphatic dicarboxylic acid with 6 to 12 carbon atoms.

Description

EXAMPLES

[0148] The invention is illustrated in the following examples, but without it being restricted thereto.

[0149] Coolant concentrate compositions were prepared by mixing the constituents as listed in Table 1 (all amounts given in weight % unless stated otherwise) and the features and physical parame-ters as pointed out in Table 1 were determined as follows:

TABLE-US-00001 Water, % DIN 51777 pH as-is ASTM D 1287
Exemplaric coolant concentrates were formulated as follows and the silicon content was meas-ured by ICP-OES after 25 weeks of storage at room temperature.

TABLE-US-00002 TABLE 1 Ex 2 Ex 4 Raw material Ex 1 (Comp) Ex 3 (Comp) Sebacic acid, wt % 2.859 2.841 3.180 3.071 Adipic acid, wt % 0.852 0.841 Dodecanedioic acid, wt % 0.141 0.123 Tolutriazole, wt % 0.204 0.208 0.161 0.153 Iso nonanoic acid, wt % 0.575 0.696 Azol inhibitor, wt % [1] 0.158 0.156 Silicophosphonate, wt % [2][3] 0.06 0.0658 Na metasilicate, wt % [2] 0.14 0.158 Na metasilicate, wt % 0.14% 0.15 water content (Karl-Fischer 2.57 2.78 2.10 2.84 Titration), wt % pH [4] 7.17 7.07 7.07 7.08 mono ethylene glycol wt % 93.174 93.067 93.6022 92.934 Si content (calc) wt .Math. ppm [5] 185 185 210 199 Si content (measured) 140 39 150 44 wt .Math. ppm [6] [1] Azol inhibitor as described in WO 2014/124826 A1, Example KM2, KM3, and KM7 [2] Silicophosphonate and sodium metasilicate were applied together in a mixture of sodium metasilicate pentahydrate and silicophosphonate in a weight ratio of approx. 2.4:1 [3] Sodium silicophosphonate according to formula (V), R.sup.6 = H, R.sup.5 = C.sub.3H.sub.6, R.sup.7 = methyl, ethyl (molar ratio 1:1) [4] the pH-value given was adjusted by addition of sodium hydroxide resp. potassium hydroxide to the formulation [5] Silicon content calculated according to the formulation as given in the table [6] Silicon content measured by ICP-OES after 25 weeks of storage at room temperature

[0150] It can easily be seen that the silicon content of all samples decreased during storage over 25 weeks. However, the samples of Examples 1 and 3 comprising a mixture of silicophosphonate and sodium metasilicate exhibited a higher silicon content after storage than the comparative formulations of Examples 2 and 4 comprising sodium metasilicate without the presence of silicophosphonate.

[0151] The coolant compositions of Examples 1 to 4 were compared in corrosion tests according to ASTM D 1384 at 88? C. and the results (weight change, mg/cm.sup.2) are given in Table 2.

TABLE-US-00003 TABLE 2 Cast Cast aluminium Example Copper Solder Brass Steel iron GALSi6Cu4 1 ?0.09 0.00 ?0.05 ?0.01 ?0.02 0.00 2 (Compar- ?0.06 ?0.03 ?0.06 ?0.02 ?0.07 0.14 ative) 3 ?0.11 0.03 ?0.08 ?0.01 0.01 0.06 4 (Compar- ?0.07 0.08 ?0.07 ?0.01 ?0.02 ?0.06 ative)

[0152] It can be seen that the corrosion tests on aluminium of the comparative Examples 2 and 4 exhibit a slight increase of weight or even material re-moval, while Examples 1 and 3 yield a constant weight of the specimen or a slight increase of the weight which support the higher efficacy of the silicate as corrosion inhibitor in the presence of silicophosphonate.

[0153] The corrosion tests on the other metals and alloys exhibit the good anti-corrosion activity of the formulations according to Examples 1 to 4.