US3445395A - Composition of improved water-glycol antifreeze and heat exchange media and process for manufacture of same - Google Patents

Description

COMPOSITION OF IMPROVED WATER-GLYCOL ANTIFREEZE AND HEAT EXCHANGE MEDIA AND PROCESS FOR MANUFACTURE OF SAME Matthew A. Boehmer, Allen Park, Mich., assignor to Wyandotte Chemicals Corporation, Wyandotte, Mich., a corporation of Michigan No Drawing. Continuation-impart of application Ser. No. 452,354, Apr. 30, 1965. This application Oct. 12, 1967, Ser. No. 674,715

Int. Cl. C09k 3/02 U.S. Cl. 25275 6 Claims ABSTRACT OF THE DISCLOSURE A liquid composition suitable for use in aqueous liquid heat exchange-type cooling systems for internal combustion engines consisting essentially of about 90 to 96 weight percent dihydroxyaliphatic alkanol having about 2 to 6 carbon atoms, about 0.5 to 3.0 weight percent alkali metal orthophosphate, about 0.1 to 3.0 weight percent alkali metal borate, about 0.1 to 1.0 weight percent mercaptobenzothiazole compound, and about 0.05 to 0.5 weight percent Water-soluble complex phosphate depicted by the general formula, A Z P O wherein A is alkali metal, Z is selected from the group consisting of zinc and magnesium, P is phosphorous, O is oxygen, x is about 2 to 3.8, y is about 0.1 to 1.0, the ratio x/y is about 2 to 3.8, v is. about 7 to 10, w is about 2 to 3 and the ratio v/w is about 3.3 to 3.8, and sufiicient minor amount of water necessary to effectively dissolve the components.

This application is a continuation-in-part of copending U.S. patent application Ser. No. 452,354, filed Apr. 30, 1965.

This invention relates to alcoholic antifreeze compositions suitable for use in aqueous liquid heat exchange cooling systems and, more particularly, for internal combustion engine cooling systems.

As is well known to those skilled in the art, glycolbased antifreeze compositions for use in heat exchange systems, and particularly automotive cooling systems, possess definite advantages as compared with volatile antifreeze compositions employing lower aliphatic alcohols. However, these glycol-based antifreeze compositions require compounding with corrosion inhibitors, antifoam additives, and other compatible additives to prevent the corrosion of metals and the foaming of the solution obtained by diluting the antifreeze with various potable waters. It is Well known that the metal parts in the cooling systems of internal combustion engines often comprise iron, copper, brass, solder, steel and aluminum. Due to the variety of metals used and varied resulting metal combinations, the long-term prevention of corrosion on all metals is particularly difficult because of galvanic cells, additive interaction and depletion.

The prior art has suggested the use of many types of corrosion inhibitors among which may be mentioned borax, arsenites, triethanolamine, sulfonated oils, resinates, sodium nitrite, sodium benzoate, triethanol ammonium phosphate, mercaptobenzothiazole and alkali metal mercaptobenzothiazole, maleic acid, picric acid, bolybdates, tungstates, urea, naphthenates, etc., which are used either alone or in combinations.

The inhibitors, known up to now, differ to a rather considerable degree as to their effect in connection with various metallic materials. Thus, there are known inhibitors which give a maximum effect in connection with light metals (for example, in cylinder heads) while others are more suited for nonferrous, heavy metals such as 3,445,395 Patented May 20, 1969 copper, and their alloys (for example, in heat exchanger constructions), and again others are relatively well suited for ferrous metal castings (for example, in motor blocks). It it, therefore, a problem to find an inhibitor or combination thereof which gives the greatest possible protective effect for the combinations of iron-like metals, light metals such as aluminum, heavy non-ferrous metals such as copper and alloys of such metals. While the inhibitors discussed above are suitable for many uses, they present serious problems where high speed, that is, high rpm. aluminum alloy cooling fluid pumps are employed. It has been found that where high r.p.m. aluminum alloy cooling liquid pumps are employed in the system that, in general, the antifreeze compositions employing the above inhibitors do not meet the performance requirements of the automobile industry.

Accordingly, it is a purpose of this invention to provide a liquid antifreeze composition which is suitable for use in aqueous liquid heat exchange-type cooling systems for internal combustion engines wherein said aqueous liquid is circulated by a high r.p.m. aluminum alloy pump and which composition is not detrimental to other parts of the conventional cooling system.

The foregoing and other objects of the invention are achieved by a liquid composition suitable for mixing with water which includes about to 96 weight percent dihydroxy aliphatic alcohol having about 2 to 6 carbon atoms, about 0.5 to 3.0 weight percent alkali metal orthophosphate, about 0.1 to 3.0 weight percent alkali metal borate, about 0.1 to 1.0 Weight percent of mercaptobenzothiazole compound, about 0.05 to 0.5 weight percent water-soluble complex phosphate depicted by the following general formula, A Z P O wherein A is alkali metal, Z is selected from the group consisting of zinc and magnesium, P is phosphorous, O is oxygen, x is about 2 to 3.8, y is about 0.1 to 1.0, the ratio x/y is about 2 to 3.8, v is about 7 to 10, w is about 2 to 3 and the ratio v/w is about 3.3 to 3.8, and sufficient minor amount of water necessary to efliciently dissolve the additives.

The composition of this invention is preferably prepared by preparing a solution of a zinc or magnesium compound, or both, and alkali metal pyrophosphates or polyphosphates, or both, and a solution of the remaining components and then combining the two solutions. The zinc and/or magnesium compounds react with the pyrophosphate and/or polyphosphate to produce the compound having the formula, A Z P O' set forth above. More specifically, by way of illustration, when the zinc compound is zinc nitrate and the pyroor polyphosphate is potassium pyrophosphate, the reaction is as follows:

Similarly, if the magnesium compound is magnesium acetate and sodium polyphosphate is employed, the following reaction takes place:

Mg z a z) 2 'b s ex lo" a s io 2 a 2 When the antifreeze composition is diluted with water, a clear solution is formed, proving that the insoluble compounds ZIlzPgOq and Mg P O- have not been formed, and that the complex phosphates as shown in the above formulas have been formed. In the ultimate aqueous solution the complex phosphate, e.g., K ZnP O may ionize in the following manner:

As a source of magnesium or zinc, a wide variety of compounds obvious to those skilled in the art may be employed, such as, for example, zinc nitrate, zinc acetate, zinc trimethylolphenate, zinc thiosulphate, zinc oxide, zinc fluoride, zinc iodate, zinc salicylate, magnesium acetate, magnesium arsenite, magnesium ferrocyanide, magnesium fluosilicate, magnesium nitrate, magnesium oxide, magnesium sulphate, and magnesium thiosulphate. The alkali metal pyrophosphates and polyphosphates which may be employed preferably have mole ratios of oxygen to phosphorous of about 3.3 to 3.8. These include sodium clude mono-, di and tripotassium orthophosphate and mono-, diand trisodium orthophosphate.

The mercaptobenzothiazole compounds which may be employed include Z-mercaptobenzothiazole and alkali metal mercaptobenzothiazoles such as sodium and potasand potassium pyrophosphate, sodium and potassium D sium mercaptobenzothiazole. hexametaphosphate and sodium and potassium tripoly- It should be pointed out that the compositions disphosphate. cussed above are concentrates and in practice are added The expressions dihydroxyaliphatic alcohol, alkali to water in a cooling system in a quantity suflicient to metal orthophosphate, alkali metal borate and merlower the freezing point of the final solution to the decaptobenzothiazole compound as used herein include sired temperature. Thus, the amount of concentrate conmixtures of one or more members of the class defined tained in the final coolant solution depends on the desired by the expressions. freezing point. In practice such final coolant solutions It has been found in accordance with this invention comprise about to 60 weight percent of the above that the compound having the general formula, A Z P O 15 described concentrate, balance water. Thus, the final soprovides improved corrosion protection for aluminum and lution would consist essentially of about 15 to 60 weight at the same time functions as an antifoam additive. The percent dihydroxy aliphatic alcohol, about 0.15 to 1.8 combination of orthophosphates and borates employed weight percent alkali metal orthophosphate, about 0.05 in the composition provides desirable corrosion protecto 1.8 weight percent alkali metal borate, about 0.01 to tion for many metals and controls or buffers the pH in 0.6 weight percent of mercaptobenzothiazole compound, the range of 8 to 9 which is desirable for long-term use about 0.007 to 0.3 weight percent of a phosphate dein cooling systems. Conventional alkaline agents such as picted by the formula, A Z P O wherein A is alkali alkali metal hydroxides may also be included to maintain metal, Z is selected from the group consisting of zinc and the pH in the range of 8 to 9. The mercaptobenzothiazole magnesium, P is phosphorous, O is oxygen, x is about compound provides good protection for corrosion of cop- 2 to 3.8, y is about 0.1 to 1.0, the ratio x/y is about 2 to per and brass surfaces and, in addition, acts as a moderate 3.8, v is about 7 to 10, w is about 2 to 3, the ratio v/w antioxidant for the glycols. The combination of zinc or is about 3.3 to 3.8, and about 40 to 85 weight percent magnesium ions in a solution with the orthophosphate, water. In addition, the final solution may contain about borate and mercaptobenzothiazole inhibitors provides a 0.001 to 0.1 weight percent antifoaming agent. highly desirable combination of results and is particu- Illustrative examples of the antifreeze composition of larly advantageous for use where aluminum pumps are this invention are shown in Table I below. An amount of employed in the cooling system. However, it was not conventional dye is added to each solution in amount to possible to use such a composition in the prior art since impart the desired color. The compositions of these exthe zinc or magnesium ions normally react with the orthoamples are obtained by preparing a separate solution of phosphate, borate or the mercaptobenzothiazole inhibitors the zinc nitrate, magnesium acetate and the pyrophosphate to give an undesirable product. or polyphosphate in an amount of water of about 0.25 The applicant has discovered that by including in the percent by weight of the final solution, whereby a phoscomposition a phosphate having the general formula phate depicted by the formula, A Z P O described A Z P O set forth above, this problem is not presented. above, is obtained. A solution of the remaining compo- It is desirable for the liquid composition of this innents is prepared and these solutions are then combined. vention to include at least one of the conventional anti These solutions can be used as a stock solution for addifoaming agents, such as nonionic surface active agents, tion to water to provide the ultimate cooling fluid.

TABLE I Percent by weight Ethylene gly 95.0 95.0 85. Diethylene glycol 5. Propylene glycol 5. Dipotassium phosphate. 1 Trisodium phosphate 1. 0 Sodium hydroxide, aqueous... 0. 18 0. 04 0. 1 2-mercaptobenzothlazole 0.25 0.25 0.05 0.1 0.25 Sodium mercaptobenzothiazole.--.. Potassium mercaptobenzothiazole Sodium tetraborate-5-hydrate 0.36 0.36 0.5 1 Sodium metaborate-8-hydrate- Tetrapotassium pyrophosphate 0.10 0.12 0.4 0.3 Sodium tripolyphosphate Zinc nitrate-6-hydrate-. 0.012 0.045 0 Magnesium acetate i-hydrate 0.023 0.14 0.11 .09 Antifoam 0 02 0.02 0.1 0.1 0. 05 0.05 0.05 0.1 0.1 0.02 0. 02 Water 1 The antiioam is the polyoxyethylene adduct of a polyoxypropylene hydrophobic baseflhaving an average molecular weight of about 2,500, wherein the oxyethylene content is about 10 weight percent of the molecule.

2 Balance.

The above antifreeze solutions exhibit a specific gravity 25/25 C. of about 1.15, a pH of about 8.5 for the formulations shown above and pH of about 8-9 when diluted with water to form a 50% by volume aqueous solution. Reserve alkalinity for 10 mls. is about 15 to 25. The freezing point of a 50% by volume aqueous solution is about 35 F. The equilibrium boiling point is about 340 F.

The superiority of the antifreeze composition of this invention over prior art commercial compositions is shown by the results of parallel tests which were run using antifreeze compositions of Examples 1 and 2 of Table I above,

in comparison with commercial antifreeze compositions containing well known prior art inhibiting agents and the compositions of Table 11 below.

TABLE IL-COMPOSITIONS, WEIGHT PERCENT Ethylene glycol Diethylene glycol Propylene glycol Dipotassium phosphate Sodium hydroxide, 50% aqueous 2-mercaptobenzothiazole Sodium tetraborate-5-hydrat Zinc nitrate hexahydrate. Magnesium acetateA-hydrate. Antiioam (same as Table I) Water Magnesium tetrabnmte 1 Balance. 1 Omit.

voir and is adjusted to give 16 to 22 inches of mercury vacuum at the pump inlet. The pump discharge pressure is controlled at 25 pounds per square inch gauge. This set of test conditions results in severe cavitation conditions within the aluminum pump. ASTM 1384-6 l-T metal corrosion specimens are mounted in the reservoir and weight losses for these metal specimens were determined by the ASTM 1384-61-T method and the results are shown in Table III below. A thermostatically controlled electric resistance heater is provided in the conduit to heat and maintain the temperature of the solution. At the start-up of the test the solution is maintained at about 110 F. After circulation has begun and the conditions level oif, the coolant temperature is increased to 245 F. The pump is then operated for 100 hours under these conditions. The cover of the pump is removed at the completion of 100 hours and the effect of the coolant on the pump is determined by observing the condition, including pitting, etc., of the pump and cover thereof. The solution is then rated from 1 to 10 for pump cavitation and erosion as shown in Table III below.

TABLE III Rating No erosion present; no metal loss 10 Very, very light, slight smoothing or shining of pump onstrate the functionality of this component of the in- Surface 9 ventlon. In Table II, compositionNo. 3 is the composltlon very light Slight roughness similar to sand cast a1umi of US. 3,015,629 to Truitt, and 1s exemplary of prlor art num surface 8 patents on corrosion inhibited antifreeze compositions.

. 1 ht medlum rou hness over 0-15 of areara Table IV below sets forth test results for corros1on of 3 1 ittin g 1 n 7 various metals and the cavitation and erosion of alumi- M p 57 E num circulation pumps used in internal combustion en- 6 5 oug mess over a 0 area so eve y 6 gine systems, with solutions of Detroit city water con- Plts or grooves taining 15% by weight of the formulations of this in- Medmm very rough (Over 50% of area) some Plts vention as well as five commercial inhibited antifreeze grooves 5 compositions and compositions 1-3 of Tabl 11 b Medium-severe, plts or grooves 4 In addition, results obtained with solutions of Examples Severe, large and p P of grooves, 110 fflllllfe 3 1 and 2 in ASTM 1384-61T, corrosive water, are also V ry Severe, y large p pits or grooves 2 shown. 40 Pump case leaking due to erosion 1 TABLE IV.15% ANTIFREEZE IN DETROIT CITY WATER Pump cavitation and erosion rating Corrosion losses in milligrams per square inch Cast Alu- Description Pump Cover Copper Solder Brass Steel iron minum Commercial Antifreeze A 5 6 36 25 5 0 0 6 Commercial Antifreeze B 8 8 1 11 1 0 0 54 Commercial Antifreeze C- 3 4 2 27 1 0 0 89 Commercial Antifreeze D 3 4 54 29 3 0 0 17 Commercial Antifreeze E".-. 3 5 1O 13 4 1 1 16 Composition 1 (Table II)- 6 8 1 10 1 .5 0 .5 1 17 I) 8 8 1 7 1 1 1 10 1o 10 1 1 1 1 1 10 Ex. 1 (Table I) compositio 10 10 0 2 1 0 0 1 Ex. 2 (Table I) composition--. 10 10 0 6 1 0 l 2 Antlfreezes Diluted with ASTM 1384-61-T Corrosive Water Ex. 2 (Table I) composition I at cone. in water containing 100 ppm. ea. of chloride, sulfate, and bicarbonate 10 10 1 0 2 0 0 2 Ex. 2 (Table I) composition at 15% cone. in water con taining 100 p.p.m. ea. of chloride, sulfate, and bicarbonate 9 10 0 8 1 1 3 3 The apparatus for the test consists of a standard automotive aluminum water pump having a capacity of 56 gallons per minute which rotates at a speed of 5000 rpm. and a cast metal reservoir about 10 inches in diameter by 12 inches high. The discharge and suction of the pump are connected by a circulation conduit of brass tubing and fittings and rubber hose whereby the antifreeze solution may be circulated from the discharge of the pump through the circulation conduit, the reservoir and back to the suction of the pump. A restrictive inch diameter orifice is installed at the pump inlet. An adjustable flow control While there has been shown and described hereinabove the present preferred embodiments of this invention, it is to be understood that various changes, alterations, and modifications can be made thereto without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. A liquid composition suitable for use in aqueous liquid heat exchange-type cooling systems for internal combustion engines consisting essentially of about 90 to 96 weight percent dihydroxyaliphatic alkanol selected valve is placed between the pump discharge and the reserfrom the group consisting of ethylene glycol, diethylene glycol, propylene glycol and mixtures thereof, about 0.5 to 3.0 weight percent alkali metal orthophosphate, about 0.1 to 3.0 weight percent alkali metal borate, about 0.1 to 1.0 weight percent of a compound selected from the group consisting of mercaptobenzothiazole and alkali metal mercaptobenzothiazoles, and about 0.05 to 0.5 weight percent water-soluble complex phosphate depicted by the general formula: A Z P O wherein A is alkali metal, Z is selected from the group consisting of zinc and magnesium, P is phosphorous, O is oxygen, x is about 2 to 3.8, y is about 0.1 to 1.0, the ratio x/y is about 2 to 3.8, v is about 7 to 10, w is about 2 to 3 and the ratio v/w is about 3.3 to 3.8, and suflicient minor amount of water necessary to effectively dissolve the components.

2. The composition of claim 1 wherein said alkali metal borate is the tetraborate of a metal selected from the group consisting of sodium and potassium.

3. The composition of claim 1 which includes about 0.001 to 0.2 weight percent antifoaming agent selected from the group consisting of nonionic surface active agents, silicone antifoam agents, aliphatic alcohols of 10 carbons or more, organic phosphates and phthalates.

4. A liquid composition suitable for use in aqueous liquid heat exchange-type cooling systems for internal combustion engines consisting essentially of about 90 to 96 weight percent dihydroxyaliphatic alcohol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and mixtures thereof, from about 0.5 to 3.0 weight percent alkali metal orthophosphate selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, monosodium phosphate, disodium phosphate, trisodium phosphate and mixtures thereof, about 0.1 to 3.0 weight percent alkali metal borate, about 0.1 to 1.0 weight percent of a compound selected from the group consisting of mercaptobenzothiazole, sodium mercaptobenzothiazole and potassium mercaptobenzothiazole, about 0.05 to 0.5 weight percent of a Water-soluble complex phosphate ob tained by mixing in aqueous solution a phosphate selected from the group consisting of alkali metal pyrophosphates, alkali metal polyphosphates and mixtures thereof with about 0.001 to 0.10 weight percent of cations obtained by the inclusion in the composition of compounds selected from the group consisting of zinc nitrate, zinc acetate, zinc trimethylolphenate, zinc thiosulfate, zinc oxide, zinc fluoride, zinc iodate, zinc salicylate, magnesium acetate, magnesium arsenite, magnesium ferro cyanide, magnesium fluosilicate, magnesium nitrate, magnesium oxide, magnesium sulfate and magnesium thiosulfate, and about 0.5 to 5 Weight percent water.

5. An aqueous coolant fluid for use in heat exchangetype cooling systems for internal combustion engine consisting essentially of about 15 to weight percent dihydroxyaliphatic alkanol selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol and mixtures thereof, about 0.15 to 1.8 weight percent alkali metal orthophosphate selected from the group consisting of monopotassium phosphate, dipotassium phosphate, tripotassium phosphate, monosodium phos phate, disodium phosphate, trisodium phosphate and mixtures thereof, about 0.05 to 1.8 weight percent of alkali metal borate, about 0.01 to 0.6 weight percent of a compound selected from the group consisting of mercaptobenzothiazole and alkali metal mercaptobenzothiazoles, about 0.007 to 0.3 weight percent of a water-soluble complex phosphate depicted by the following formula: A Z P O wherein A is alkali metal, Z is selected from the group consisting of zinc and magnesium, P is phosphorous, O is oxygen, x is about 2 to 3.8, y is about 0.1 to 1.0, the ratio of x/y is about 2 to 3.8, v is about 7 to 10, w is about 2 to 3, the ratio v/w is about 3.3 to 3.8, and about 40 to 85 weight percent water.

6. The composition of claim 5 which includes about 0.001 to 0.1 weight percent antifoaming agent selected from the group consisting of nonionic surface active agents, silicone antifoam agents, aliphatic alcohols of 10 carbons or more, organic phosphates and phthalates.

References Cited UNITED STATES PATENTS 2,616,854 11/1943 Fenske 25279 2,777,821 l/ 1957 Harford 25278 2,937,145 5/1960 Cutlip et a1. 252-75 2,980,620 4/1961 Hatch 252 3,015,629 1/1962 Truitt 252 OTHER REFERENCES Putilova: Metallic Corrosion Inhibitors, Pergamon Press, 1960, p. 151.

LEON D. ROSDOL, Primary Examiner.

STANLEY D. SCHWARTZ, Assistant Examiner.

US. Cl. X.R. 252-78, 389