Hydraulic fluids comprising orthosilicate esters

An orthosilicate ester having the general formula:

• ##STR13## wherein, i. each of R.sup.7, R.sup.8, R.sup.9, and R.sup.10 is the same or different;
• and
• ii. each of R.sup.7, R.sup.8, R.sup.9 and R.sup.10 is a propylene glycol monoalkyl ether residue of the formula:
• ##STR14## in which:
• a. in each adjacent R.sup.5 and R.sup.6 one is a hydrogen atom and the other is a methyl group;
• b. each n is the same or different and the total value of all integers n is from 8 to 16;
• and
• c. each R is the same or different and is selected from the group consisting of a methyl group and an ethyl group.

An orthosilicate ester having the general formula:

• ##STR15## wherein, i. R.sup.11 is a tertiary alkyl group containing 4 to 8 carbon atoms;
• ii. R.sup.12 is a glycol monoalkyl ether residue of the formula:
• ##STR16## ii. R.sup.13 is the same as or different from R.sup.12 and is a glycol monoalkyl ether residue of the formula:
• ##STR17## iv. R.sup.14 is selected from the group consisting of tertiary alkyl groups containing 4 to 8 carbon atoms, being the same as or different from R.sup.11, and glycol monoalkyl ether residues of the formula:
• ##STR18## being the same as either R.sup.12 or R.sup.13 or being different from both R.sup.12 and R.sup.13 ;
• and
• v. in glycol monoalkyl ether residues of the formula:
• ##STR19## a. each R.sup.5 and R.sup.6 is the same or different and both are hydrogen atoms or in each adjacent R.sup.5 and R.sup.6 one is a hydrogen atom and the other is a methyl group;
• b. each n is the same or different and the total value of all integers n is from 4 to 8 when R.sup.14 is a branched chain alkyl group or from 6 to 12 when R.sup.14 is a glycol monoalkyl ether residue;
• and
• c. each R is the same or different and is selected from the group consisting of a methyl group and an ethyl group.