Water-based low foam hydraulic fluid employing 2-ethylhexanol defoamer

A hydraulic fluid characterized by improved low-foaming properties comprising water, about 0.15 to 2 percent by weight of 2-ethylhexanol and conventional hydraulic fluid additives wherein said fluid includes a thickener and at least one additive selected from the group consisting of

• phosphate esters or salts thereof selected from the group consisting of ##STR11## and mixtures thereof wherein ethylene oxide groups are represented by EO;
• R is selected from the group consisting of linear or branched chain alkyl groups wherein said alkyl groups have about 6 to 30 carbon atoms or alkyklaryl groups wherein the alkyl groups have about 6 to 30 carbon atoms and X is selected from the group consisting of hydrogen, alkali or alkaline earth metal, the residue of ammonia or an amine and mixtures thereof, and n is a number from 1 to 50;
• an alkyldialkanolamide of the formula ##STR12## wherein R.sub.1 is alkyl of about 4 to about 54 carbon atoms and R.sub.2 is alkyl of about 2 to about 6 carbon atoms, or an alkyldialkanolamide prepared by esterifying a dialkanolamine with an alkyl carboxylic acid and removing water of esterification wherein said alkyldialkanolamide is derived from a branched or straight chain, saturated or unsaturated aliphatic dicarboxylic acid having 8 to 54 carbon atoms,
• a metal deactivator;
• an additional defoamer;
• a corrosion inhibitor;
• water-soluble ethers or esters of ethoxylated C.sub.8 -C.sub.36 aliphatic monohydric or polyhydric alcohols or acids,
• sulfur compound additives selected from the group consisting of the ammonia, amine or metal salts of 2-mercaptobenzothiazole or 5-, 6- and 7-substituted 2-mercaptobenzothiazole, and sulfurized molybdenum and antimony compounds represented by the formula:
• ##STR13## wherein M is molybdenum or antimony and R is organic and is selected from the group consisting of C.sub.3 -C.sub.20 alkyl, aryl, alkylaryl radicals and mixtures thereof, and
• wherein said thickener is a polyether polyol having a molecular weight of about 1000 to about 40,000 prepared by reacting ethylene oxide or ethylene oxide and at least one lower alkylene oxide having 3 to 4 carbon atoms with at least one active hydrogen-containing compound and at least one alpha-olefin oxide or glycidyl ether having a carbon chain length of about 12 to 18 aliphatic carbon atoms wherein said alpha-olefin oxide or glycidyl ether is present in the amount of 1 to about 20 percent by weight based upon the total weight of said thickener.

A method of improving low foam properties in a hydraulic fluid comprising blending with said fluid at least about 0.15 percent by weight of 2-ethylhexanol and wherein said hydraulic fluid includes at least one additive selected from the group consisting of

• phosphate esters or salts thereof selected from the group consisting of ##STR15## and mixtures thereof wherein ethylene oxide groups are represented by EO;
• R is selected from the group consisting of linear or branched chain alkyl groups wherein said alkyl groups have about 6 to 30 carbon atoms or alkylaryl groups wherein the alkyl groups have about 6 to 30 carbon atoms and X is selected from the group consisting of hydrogen, alkali or alkaline earth metal, the residue of ammonia or an amine and mixtures thereof, and n is a number from 1 to 50;
• an alkyldialkanolamide of the formula ##STR16## wherein R.sub.1 is alkyl of about 4 to about 54 carbon atoms and R.sub.2 is alkyl of about 2 to about 6 carbon atoms, or an alkyldialkanolamide prepared by esterifying a dialkanolamine with an alkyl carboxylic acid and removing water of esterification wherein said alkyldialkanolamide is derived from a branched or straight chain, saturated or unsaturated aliphatic dicarboxylic acid having 8 to 54 carbon atoms,
• a metal deactivator;
• an additional defoamer;
• a corrosion inhibitor;
• water-soluble ethers or esters of ethoxylated C.sub.8 -C.sub.36 aliphatic monohydric or polyhydric alcohols or acids,
• sulfur compound additives selected from the group consisting of the ammonia, amine or metal salts of 2-mercaptobenzothiazole of 5-, 6- and 7-substituted 2-merceptobenzothiazole, and sulfurized molybdenum and antimony compounds represented by the formula:
• ##STR17## wherein M is molybdenum or antimony and R is organic and is selected from the group consisting of C.sub.3 -C.sub.20 alkyl, aryl, alkylaryl radicals and mixtures thereof, and
• wherein said thickener is a polyether polyol having a molecular weight of about 1000 to about 40,000 prepared by reacting ethylene oxide or ethylene oxide and at least one lower alkylene oxide having 3 to 4 carbon atoms with at least one active hydrogen-containing compound and at least one alpha-olefin oxide or glycidyl ether having a carbon chain length of about 12 to 18 aliphatic carbon atoms wherein said alpha-olefin oxide or glycidyl ether is present in the amount of 1 to about 20 percent by weight based upon the total weight of said thickener.