Water/glycol-based hydraulic fluid
The present invention provides a water/glycol-based hydraulic fluid that includes a total fatty acid and dimer acid of more than 0.4 and no more than 1.2 mass % as a fatty acid lubricant, and also a phosphate ester at between 0.01 and 0.07 mass %. The phosphate ester has the following structure (1) here R1 and R2 each represent a hydrogen atom or a hydrogen group with a carbon number between 1 and 30, and may either be mutually identical or mutually different; R 3 represents a hydrocarbon group with a carbon number between 1 and 20; R 4 represents a hydrogen atom or a hydrocarbon group with a carbon number between 1 and 30; and X 1 , X 2 , X 3 , and X 4 each indicate an oxygen atom or a sulfur atom, where these may either be mutually identical or mutually different.
1. A water/glycol-based hydraulic fluid that includes water at between 20 and 60 mass %, between 20 and 60 mass % of glycol, a fatty acid and a dimer acid, wherein the total fatty acid and dimer acid is more than 0.4 mass % and no more than 1.2 mass % as a fatty acid lubricant, and also a phosphate ester represented by the following general formula (1):
where R 1 and R 2 each represent a hydrogen atom or a hydrogen group with a carbon number between 1 and 30, and may either be mutually identical or mutually different; R 3 is —CH(CH3)- or —CH2-CH2-; R 4 represents a hydrogen atom or a hydrocarbon group with a carbon number between 1 and 30; and wherein X 1 and X 2 of the phosphate ester are oxygen atoms and X 3 and X 4 are sulfur atoms.
2. The water/glycol-based hydraulic fluid as set forth in claim 1 , wherein: the inclusion proportion of the phosphate ester is between 0.01 and 0.07 mass %.
3. The water/glycol-based hydraulic fluid as set forth in claim 1 , wherein: the carbon number of the fatty acid is between 6 and 18.