US 4,450,087 AGrant
Vapor Lock Resistant Hydraulic Fluids
Issue Date:1984-05-22
•7 Claims
Abstract
A composition suitable for use as a hydraulic fluid comprises: (a) a lubricating oil preferably in an amount of from 20 to 80% by weight; (b) a minor amount of oil-soluble borate ester; (c) an amine which prevents deposition of oil-insoluble hydrolysis products of the borate ester; and optionally (d) an oil soluble orthoester of the formula: ##STR1## wherein R.sup.7, R.sup.8, R.sup.9 and R.sup.10 are specified groups.
Metadata
Inventors
- Herbert F. Askew
- Colin J. Harrington
- Terry J. P. Bridgwater
Application Information
Application Number:US 4765613
Filing Date:1983-03-18
Priority Date:1974-07-12
Art Unit:166
Classifications
IPC:
C10M 126C10M 154
Field of Search:
25249.6;78.1;78.3;78.5;73
Patent Drawings
This patent does not have any drawings.
Description
This invention relates to hydraulic fluids and particularly to mineral oil hydraulic fluids.
In hydraulic systems for which mineral oil or certain other fluids are specified as the operative fluid problems arise due to the presence of water. This water may be present as the result of condensation or inadequate drying prior to the filling of the system or subsequently, by diffusing through worn seals or flexible hoses. In either case the vapour lock temperature of the fluid can be reduced to the boiling point of water even by the presence of very minor amounts of water, e.g. of the order of 0.5%. This constitutes a serious deficiency with particularly dangerous consequences in those systems which are brake systems or central hydraulic systems including brake systems.
According to the present invention there is provided a composition suitable for use as a hydraulic fluid which comprises:
(a) a lubricating oil, preferably in an amount of from 20 to 80% by weight based on the total weight of the composition;
(b) a minor amount of oil-soluble borate ester, preferably of the general formula: ##STR2## wherein: (i) R.sup.1, R.sup.2 and R.sup.3 are the same or different and each is an aryl group or a straight or branched chain alkyl group or alicyclic group, preferably containing from 4 to 20 carbon atoms, or is a group of the formula --(R.sup.4 O).sub.n R.sup.5 wherein each R.sup.4 is the same or different and each is an alkylene group, preferably ethylene, propylene or butylene, R.sup.5 is an alkyl group, preferably containing from 1 to 18, more preferably 1 to 4, carbon atoms, or an aryl group, and n is an integer, preferably of from 1 to 10, more preferably of from 2 to 4;
or
(ii) R.sup.1 and R.sup.2 are the same or different and as defined above and R.sup.3 is a group of the general formula: ##STR3## wherein R.sup.1 and R.sup.2 are as defined above and R.sup.6 is an alkylene group, preferably containing at least 4, more preferably from 4 to 20, carbon atoms, or is an oxyalkylene radical of the formula --R.sup.4 --OR.sup.4).sub.n wherein R.sup.4 and n are as defined above;
or
(iii) R.sup.1 is as defined above and R.sup.2 and R.sup.3 together form the group ##STR4## wherein R.sup.1 is as defined above;
(c) an amine which prevents deposition of oil-insoluble hydrolysis products of the borate ester; and optionally
(d) an oil soluble orthoester of the formula: ##STR5## wherein R.sup.7 is hydrogen or an alkyl group, preferably methyl or an aryl, alkaryl, or aralkyl group; R.sup.8, R.sup.9 and R.sup.10 are the same or different, preferably the same, and each is a straight or branched chain alkyl group, preferably containing from 4 to 20 carbon atoms, an aryl, alkaryl, or aralkyl group, or the group --(R.sup.11 --O).sub.m R.sup.12 wherein each R.sup.11 is the same or different and each is an alkylene group, preferably ethylene or propylene; R.sup.12 is an alkyl group, preferably containing from 1 to 20 carbon atoms, or an aryl, alkaryl or aralkyl group; and m is an integer of from 2 to 10.
It is required that the borate ester used in the composition of the invention should be oil-soluble and, in the case of trialkyl borates, oil solubility may be provided by selecting an ester made from straight chain alcohols containing less than 12 carbon atoms or from branched chain alcohols containing up to 24 carbon atoms. In the case of borate esters of the type derived from di- and polyoxyalkylene glycol ethers, those derived from di- and polyoxyethylene glycol ethers are generally insoluble unless at least one of the terminal ether groups is sufficient to solubilise the ester. Alternatively oil-solubility for this latter type of ester may be achieved by incorporating polyoxypropylene or higher polyoxyalkylene radicals into the molecule.
Examples of particularly useful borate esters include
tris (dipropylene glycol monomethyl ether) borate
tris (ethylene glycol monobutyl ether) borate
tris (triethylene glycol monobutyl ether) borate
tris (tripropylene glycol monomethyl ether) borate
tri n-decyl borate
tri (isotridecyl) borate
tri (2-ethyl hexyl) borate
tri (3,3-dimethyl butyl) borate
The amine used in the present invention should have a reasonably low vapour pressure consistent with providing a vapour lock temperature in excess of 120.degree. C. The amine used will also depend upon the borate ester used. A simple test for determining whether a particular amine is suitable for preventing deposition of oil-insoluble hydrolysis products of a particular borate ester consists of dissolving the amine and borate in the selected lubricating oil, (in the amounts intended in the final hydraulic fluid), sealing the resulting fluid together with 0.5% by weight of water in a clear glass ampoule and heating at 100.degree. C. for 24 hours and cooling. In this so called "ampoule" test, if the resulting solution is clear and bright then the combination is satisfactory.
Many amines have been found to be suitable, including primary, secondary and tertiary amines, especially those containing a total of at least 5 carbon atoms. Amines which have been found to be particularly useful with a wide range of borates include Primene 81 R and Primene JMT which are commercially available primary amines with two methyl groups on the alpha carbon atom.
Other amines which may be useful are Mannich bases formed by condensation of an amine and formaldehyde with a phenol previously alkylated with di or polyisobutylene; polyisobutenyl succinimides derived from di or polyamines; or amides derived from di or polyalkyl polyamines and polyisbutenyl substituted monocarboxylic acids.
The amounts of components (b), (c) and (d) (when present) may each vary over a wide range. However, it is preferred to use from 1 to 50%, more preferably from 1 to 20%, particularly from 5 to 10% by weight of the borate ester; from 1 to 50%, more preferably from 5 to 30%, particularly from 10 to 20% by weight of the orthoester; and from 0.5 to 20%, more particularly from 1 to 10%, by weight of amine, the percentages being based on the total weight of the composition.
In compositions containing orthoester, the ratio of orthoester to borate may vary, for example, from 10:1 to 1:10 by weight but in general more orthoester than borate will be used, the preferred ratio varying from 5:1 to 2:1 by weight.
The ratio of borate to amine will depend upon the nature of the two particular compounds used but it is preferred to use from 5:1 to 1:1 by weight.
The lubricating oil used as base fluid in the compositions of the invention is preferably a mineral oil but may also be a synthetic hydrocarbon oil, a synthetic carboxylic acid ester or mixture thereof, a siloxane or phosphate ester or other well known synthetic lubricant.
The invention will now be illustrated by the following Examples:
Example 1
This composition has the following physical characteristics: Boiling point 257.degree. C., Viscosity at -40.degree. C. 1328cS, Viscosity index 218. The composition was subjected to the Markey vapour-lock test in the dry state and after contamination with varying amounts of water, with the following results:
The mineral oil alone with 0.5% water had a vapour lock temperature of 101.degree. C.
Examples 2 to 32
Further blends comprising various combinations of borate ester and amine in mineral oil were formulated and subjected to the Gilpin vapour-lock test. Details of these blends and of the results obtained are given in Table 1.
The base fluid used in each case was a naphthenic mineral oil having the following characteristics:
The Gilpin vapour-lock test was conducted in a Gilpin apparatus and by the Gilpin method as described in S.A.E. Paper 710 253 entitled "Operating performance of motor vehicle braking systems as affected by fluid water content." The Gilpin vapour-lock temperature (VLT) was taken to be the temperature which corresponded with the appearance of 3 ml of bubbles.
Examples 33 to 47
Gilpin vapour lock temperatures were evaluated (in the manner described above) for a range of compositions containing different combinations of borate ester and lubricating oil base fluid, Primene JMT being used as the amine component in each case. Details of these compositions and of the results obtained are given in Table 2.
Example 48
This blend conformed with the base oil requirements of Specification DTD 585. The Gilpin vapour-lock temperature was 177.degree. C. after heating at 100.degree. C. for 24 hours with 0.5% water in a sealed glass ampoule.
Example 49
This blend also conformed to the base oil requirements to DTD 585 Specification and the Gilpin (3 ml) wet vapour-lock temperature was 203.degree. C.
Example 50
This blend also conformed to the base oil requirements of the DTD 585 Specification and the Gilpin (3 ml) wet vapour-lock temperature was 206.degree. C.
Example 51
This blend conformed to the base oil requirements of the DTD 858 Specification and has a Gilpin (3 ml) wet vapour-lock temperature of 205.5.degree. C.
Examples 52 to 81
Further blends containing orthoester were formulated from a range of different orthoesters and borate esters. In each case Primene JMT was used as the amine component and the base fluid was the naphthenic mineral oil used in Examples 2 to 32. Samples of these blends were subjected to the Gilpin (3 ml) vapour-lock test (i) after reaction with 0.5% water at 100.degree. C. for 24 hours and (ii) after subjection to a humidity test at a Relative Humidity (RH) of 80% and temperature of 22.degree. C. substantially as described in the FMVSS 113 Specification but extended to a 5 day period and without a reference fluid. Also, the Rubber Swell properties of the test fluids with respect to nitrile rubber were determined by measuring the increase in volume of a 2.54 cm square, 2 mm thick nitrile rubber specimen in 50 mls of fluid at 120.degree. C. for 3 days.
Details of these blends and of the results obtained are given in Table 3.
The abbreviations and commercial products referred to in Tables 1 to 3 are as follows:
The vapour-lock test results set out in the foregoing Examples and in Tables 1 to 3 show that fluids in accordance with the invention retain unexpectedly high vapour-lock temperatures even in the presence of water. Furthermore, the rubber swell test results set out in Table 3 show that fluids in accordance with the invention may be blended so as to provide fluids having rubber swell properties acceptable in commercial hydraulic systems.
Claims
We claim:
1. A composition of matter suitable for use as a hydraulic fluid which comprises (a) at least 20%, by weight, of a lubricating oil which is a member selected from the group consisting of a mineral oil, a synthetic hydrocarbon oil, a synthetic carboxylic acid ester, a siloxane or a phosphate ester; (b) 1 to 50%, by weight, of oil-soluble borate ester which is a compound, or mixture of compounds, having the formula: ##STR6## wherein: (i) R.sup.1, R.sup.2 and R.sup.3 are the same or different and each is an aryl group or a straight or branched chain alkyl group or alicyclic group containing from 4 to 20 carbon atoms, or is a group of the formula --R.sup.4 O).sub.n R.sup.5 wherein each R.sup.4 is the same or different and each is an alkylene group selected from ethylene, propylene or butylene, R.sup.5 is an alkyl group containing from 1 to 18 carbon atoms, or an aryl group, and n is an integer, from 1 to 10; or (ii) R.sup.1 and R.sup.2 are the same or different and as defined above and R.sup.3 is a group of the general formula: ##STR7## wherein R.sup.1 and R.sup.2 are as defined above and R.sup.6 is an alkylene group containing from 4 to 20 carbon atoms, or is an oxyalkylene radical of the formula --R.sup.4 --OR.sup.4).sub.n wherein R.sup.4 and n are as defined above; or (iii) R.sup.1 is as defined above and R.sup.2 and R.sup.3 together form the group ##STR8## wherein R.sub.1 is as defined above; (c) 0.5 to 20%, by weight, of an amine which prevents deposition of oil insoluble hydrolysis products of the borate ester; and (d) 1 to 50%, by weight, of an oil soluble orthoester of the formula: ##STR9## wherein R.sup.7 is hydrogen or lower alkyl; R.sup.8, R.sup.9 and R.sup.10 are the same or different and each is a straight or branched chain alkyl containing from 4 to 20 carbon atoms, benzyl or the group --(R.sup.11 --O).sub.m --R.sup.12 where R.sup.11 is a lower alkylene group and R.sup.12 is an alkyl group containing 1 to 20 carbon atoms; and m is an integer from 2 to 10.
2. A composition as claimed in claim 1 wherein R.sup.7 is a hydrogen atom or a methyl group.
3. A composition as claimed in claim 1 which contains from 5 to 30% by weight of orthoester based on the total weight of the composition.
4. A composition as claimed in claim 1 wherein the ratio of orthoester to borate ester is in the range from 5:1 to 2:1 by weight.
5. A composition as claimed in claim 1 containing from 1 to 20% by weight of borate ester based on the total weight of the composition.
6. A composition as claimed in claim 1 containing from 1 to 10% by weight of amine based on the total weight of the composition.
7. A composition as claimed in claim 1 wherein the ratio of borate ester to amine is from 5:1 to 1:1 by weight.
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