KR930002766B1 - Inhibited alkylene glycol coolant and cooling process - Google Patents

Abstract

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Description

Inhibited Alkylene Glycol Refrigerants and Cooling Methods

Detailed description of the invention

The present invention relates to corrosion inhibited alkylene glycol compositions useful as coolants for heat exchange systems of internal combustion engines and to methods of using the compositions to cool the engine.

Currently, antifreeze compositions containing alcohols, in particular ethylene glycol, are typically mixed with an equivalent or large amount of water in the cooling system of the internal combustion engine to lower the freezing point of the water. Alcohols mixed with water in the cooling system produce acidic substances that cause corrosion of the metal surfaces in contact with the cooling system. Thus, the uninhibited antifreeze composition promotes the corrosion of brass, copper, lead, steel, cast iron and aluminum and magnesium in more recent engines.

In the past, many corrosion inhibitors and mixtures thereof have been used in the water-based antifreeze compositions described above. Such inhibitors include alkali metal chromates, nitrates, phosphates, borates, tungstates, molybdates, carbonates and silicates and alkaline earth metal borates. Inhibitors also include organic compounds such as carboxylic acids, thiocyanates, phenols, mercaptans, mercaptothiazoles, and various aromatic triazoles.

Many inhibitors, such as silicates, are rapidly consumed and no longer useful for continuous metal protection. Other inhibitors, such as nitrite, which are possible as inhibitors of the corrosion of iron or steel, actually promote the corrosion of aluminum or magnesium. Recently, as an attempt to develop an improved cooling system in view of fuel efficiency and cooling efficiency, a cooling method using a coolant containing little or no water has been developed [US Patent No. 4,550, 694]. And 4,630,572. The main way to improve the engine efficiency of the system is to operate the engine at temperatures higher than the standard engine temperature. Such higher temperatures often break down many corrosion inhibitors such as silicates at much faster rates. In addition, unrestricted glycols used as anhydrous coolants have been found to corrode typical cooling system components.

Thus, it is highly desirable to provide a suppressed coolant composition that can function at temperatures above 105 ° C., but which does not corrode metals commonly used in cooling systems of internal combustion engines.

The present invention relates to (1) at least 90% by weight of alkylene glycol or a mixture of two or more alkylene glycols, (2) (a) 0.02 to 4 parts by weight of azole, (b) 0.05 to 3 parts by weight of molybdate salt and ( c) a composition comprising an inhibitor of corrosion inhibition comprising 0 to 3 parts by weight of phosphoric acid. The present invention is also a method of cooling an internal combustion engine by circulating the composition as a coolant through a cooling jacket of the engine.

By using a mixture of (1) at least 90% by weight of alkylene glycol as the coolant and (2) the corrosion inhibitors described above, metals such as aluminum and magnesium may be added to the absence of a cooling system, for example radiators, coolant pumps, engine blocks. It can be used in the cylinder head. The coolant composition can be used in engines operating at temperatures higher than standard without degradation. As a result, the fuel efficiency of the engine is greater and produces combustion products that are less harmful to the surrounding environment than engines operating at normal temperatures below 100 ° C.

The coolant composition of the present invention is particularly suitable for use in a method for cooling an internal combustion engine, and is also useful for other uses such as fruit liquid or a pressurized liquid.

Alkylene glycol suitably used as a coolant in the composition of the present invention is a dihydric alcohol that is liquid in the temperature range of -65 ° C to -30 ° C and boils at temperatures of 150 ° C to 230 ° C and atmospheric pressure. Examples of glycols include ethylene glycol, propylene glycol, glycerol and mixtures of two or more thereof in certain proportions. Preferred glycols are ethylene glycol, propylene glycol and mixtures thereof. More preferably, the alkylene glycol is propylene glycol or a mixture of at least 30% by weight propylene glycol and 0.1 to 70% by weight ethylene glycol. Most preferably, propylene glycol is used.

Corrosion inhibitor mixtures suitably used in the coolant composition include (a) 0.06 to 0.5 parts by weight of azole, (b) 0.1 to 0.2 parts by weight of molybdate salt and (c) 0.05 to 0.09 parts by weight of phosphoric acid, preferably It consists of these components.

Suitable corrosion inhibition amounts of inhibitor mixtures are determined experimentally using various amounts of inhibitor mixture samples in standard corrosion tests. Since some users may attach greater importance to any one test than others, the importance of the corrosion test is relative, but never absolute. However, the ASTM test method described in the Examples is generally used.

Typically, 0.05 to 2 weight percent inhibitor mixture in the total coolant composition is suitable, preferably 0.1 weight percent, more preferably 0.25 to 1 weight percent, even more preferably 0.75 weight percent inhibitor mixture. do.

The azoles used in the practice of the present invention are azoles which are soluble in alkylene glycols and are corrosion inhibitors for copper and brass. The azole is preferably a triazole such as tolyltriazole, benzotriazole and mixtures of two or more thereof. Most preferred is tolyltriazole. Other azoles that are suitable but less preferred than the triazoles described above include thiazoles such as mercaptobenzothiazole and alkali metal salts of the azoles described above.

Molybdate salts used in inhibitor mixtures are salts that are soluble in alkylene glycols and are corrosion inhibitors for steel and cast iron. The salt includes molybdate data of alkali metals and alkaline earth metals. Examples of preferred molybdates are sodium molybdate, ammonium molybdate, calcium molybdate and mixtures of two or more thereof. Sodium molybdate is most preferred.

Phosphoric acid is used to maintain the pH of the coolant composition at 7 to 9, preferably 7 to 8 as necessary. Some alkylene glycol mixtures have a limited pH, in which case there is no need to adjust the pH.

The coolant composition of the present invention is prepared by first dissolving water of 10 wt% or less in alkylene glycol. Preferably less than about 5% by weight, more preferably about 3% by weight of water is dissolved in propylene glycol. Most preferably alkylene glycols are used with little water, i.e. less than about 1% by weight of water. The corrosion inhibitor mixture is then dissolved in the alkylene glycol composition. Preferably, the resulting coolant composition is made basic by addition of sodium hydroxide or calcium until pH 7-9, or phosphoric acid is added if the initial pH value of the alkylene glycol base emulsion is too alkaline. Optionally, other ingredients such as dyes or antifoams, such as those described in US Pat. Nos. 3, 340, 309, 504, 401, 3, 770, 701 and 2, 425, 755 It can be added to the composition. Antifoam additives are not necessary but can nevertheless be used.

The method of cooling the internal continuous engine is carried out by circulating the coolant composition of the present invention through the cooling jacket of the engine. The compositions of the present invention are described in U.S. Patent Nos. 4, 550, 690 already mentioned at ambient pressure, e.g., atmospheric pressure, in order to prevent corrosion of metal components of the chiller using carefully selected corrosion inhibitor mixtures. It is designed to be used "as is", ie as a finished product coolant, in a chiller as described.

The cooling method is preferably carried out at the temperature already mentioned above, at a coolant operating temperature of 105 ° C to 150 ° C. The operating temperature range of the more preferable coolant is at least 110 ° C, most preferably at least 120 ° C and more preferably at most 140 ° C, most preferably at most 135 ° C.

Preferably the coolant composition contains up to 5% by weight, more preferably up to 3% by weight and most preferably up to 1% by weight of water.

Preferred compositions of corrosion inhibitor packages are the same as already described above and most preferably consist essentially of azoles, molybdate salts and optionally phosphoric acid when pH adjustment is required. The amount of each component used is already described in the text.

The following examples are intended to illustrate the invention and should not be understood as limiting the scope of the invention. Unless otherwise indicated, all parts and percentages are by weight.

[Examples 1 and 2]

The coolant concentrate is prepared by dissolving about 1 part tolyltriazole, about 0.6 part tartrium molybdate dihydrate and about 0.3 part 85% aqueous solution in 20 parts of 4 parts water-containing propylene glycol. The resulting concentrate is mixed with 370 parts of propylene glycol to form a coolant composition (100 ml sample diluted 1: 1 in water) at pH 6-7. Anhydrous coolant compositions are tested for corrosion inhibition. The composition and test results of the resulting coolant are listed in Table I.

Additional coolant compositions (Example No. 2) are similarly prepared using mixtures of ethylene glycol and propylene glycol as alkylene glycol mixtures. This composition is similarly tested for corrosion inhibition. The composition of the coolant and the results of these tests are listed in Table I.

For comparison purposes, a control coolant composition is prepared using propylene glycol (Example No. C ₁ ) and a 30/70 mixture of propylene glycol with uninhibited propylene glycol (Example No. C ₂ ). These compositions are tested and the results of these tests are listed in Table I.

TABLE 1

* Not an embodiment of the invention

* * Weight loss (mg) is measured using a standard coupon for testing with an area of 2 inches x 1 inch (5 cm x 2.5 cm).

* * * The same method used for Al except washing the Mg coupon with 20% chromic acid instead of ASTM D-4340 2% chromic acid-5% orthophosphoric acid mixture.

① PG-propylene glycol, EG-ethylene glycol

② TT-tolyltriazole

③ ASTM D-1384

④ ASTM D-4340-ASTM Modified using pure fluid without corrosive water.

⑤ Ford escort operating at ΔT 8.3 ° C (15 ° F) across the entire average engine operating temperature of 107 ° C (225 ° F) and heater core and at ΔT 19.4 ° C (35 ° F) across the radiator. Test engine dynamometer using Ford Escort 4 cylinder engine.

As is evident from the data set forth in Table I, the coolant compositions of the present invention exhibit good corrosion inhibitory properties for both aluminum and magnesium when exposed to temperatures in excess of 105 ° C. for a period of up to 672 hours.

Claims (18)

(1) at least 90% by weight of alkylene glycol or a mixture of two or more alkylene glycols, and (2) (a) 0.02 to 4 parts by weight of azole, (b) 0.05 to 3 parts by weight of molybdate salt and (c) 0 A coolant composition comprising a corrosion inhibiting amount of a caustic agent comprising from 3 parts by weight of phosphoric acid. The composition of claim 1, wherein the alkylene glycol is propylene glycol or a mixture of at least 30% by weight propylene glycol and 0.1 to 70% by weight ethylene glycol. The composition of claim 2 wherein the composition contains up to 5% water. The composition of claim 2 wherein the composition contains up to 1% by weight of water. The composition of claim 4 wherein the alkylene glycol consists solely of propylene glycol. The composition of claim 2 wherein the azole is triazole. 7. The composition of claim 6 wherein the triazole is tolyltriazole, benzotriazole and mixtures thereof. The composition of claim 2 or 4 wherein the azole is tolyltriazole. 7. The composition of claim 6 wherein the azole is mercaptobenzothiazole. The composition of claim 2 wherein the molybdate salt is an alkali metal molybdate. The composition of claim 2 or 4, wherein the molybdate salt is sodium molybdate. 6. The composition of claim 5 wherein (a) tolyltriazole, (b) sodium molybdate and (c) phosphoric acid, respectively, of (a) 0.25%, (b) 0.15% and (c) 0.075% by weight of the composition. Compositions present in amounts. A method of removing heat generated during operation of an internal combustion engine by circulating a coolant exposed to ambient pressure in an ambient environment at approximately 105 ° C. or higher through an engine's cooling jacket, the method comprising contacting the coolant with the coolant as a coolant. A method for improving the use of the liquid composition, which is the coolant composition of claim 1, having low corrosiveness to the material. The process of claim 13 wherein the alkylene glycol consists essentially of propylene glycol or a mixture of at least 30% by weight propylene glycol and 0.1 to 70% by weight ethylene glycol and the coolant composition contains 5% by weight or less of water. . 15. The method of claim 14, wherein the coolant composition contains up to 1 weight percent water and the alkylene glycol consists only of propylene glycol. The method according to claim 14 or 15, wherein (a) azole is tolyl triazole and (b) molybdate is sodium molybdate. 16. The sodium molybdate according to claim 14 or 15, wherein (a) tolyltriazole is present at 0.25% by weight and (b) is present at 0.15% by weight based on the weight of the composition. And (c) the phosphoric acid is present at 0.075% by weight. 16. The method of claim 14 or 15, wherein the coolant operating temperature is typically in the range of 110 degrees to 140 degrees Celsius.