Compositions – Heat-exchange – low-freezing or pour point – or high boiling... – Organic components
Reexamination Certificate
2000-08-01
2003-02-18
Gupta, Yogendra N. (Department: 1751)
Compositions
Heat-exchange, low-freezing or pour point, or high boiling...
Organic components
C252S079000, C252S574000, C508S433000, C508S440000
Reexamination Certificate
active
06521142
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to hydraulic fluids, and more particularly, to hydraulic fluids that have fire resistant properties.
BACKGROUND OF THE INVENTION
Hydraulic fluids are fluids which are used to offer resistance in hydraulically operated mechanisms. The main classes of hydraulic fluids commonly used are petroleum-based [See U.S. Pat. Nos. 4,566,994 and 4,800,030] (composed of chemically saturated or unsaturated, straight-chained, branched or ring-type hydrocarbons [See U.S. Pat. No. 5,236,610]), water/glycol solutions, and water-in-oil emulsions [See U.S. Pat. No. 3,236,778].
There are several notable disadvantages to these conventional types of hydraulic fluids. The petroleum-based hydraulic fluids pose certain environmental and health risks. In addition, petroleum oils may be the least fire-resistant and attempts to improve fire-resistance by the addition of fire-resistant compounds tends to reduce lubricity. Petroleum is a non-renewable and limited natural resource. Moreover, petroleum oil allowed to escape into the ground causes soil and groundwater contamination which can pose additional health and environmental problems.
Water-based hydraulic fluids have disadvantages as well. Hydraulic fluids of this type often lack sufficient mechanical stability and lubricity to operate at high temperatures and pressures.
There is a need for hydraulic fluids which are based on renewable natural resources and which simultaneously have the characteristics of desirable viscosity, lubricity, stability, and volatility while reducing potential harm to the environment.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides a hydraulic fluid composition comprised of a mixture of about 20% to about 90% by weight of a trialkoxyalkyl-phosphate, about 10% to about 80% by weight of a natural triglyceride diluent, and about 0.1% to about 2% by weight of a high molecular weight polymer. In a preferred embodiment, the trialkoxyalkyl-phosphate is tributoxyethyl-phosphate and the natural triglyceride diluent is canola oil.
In another aspect, the present invention provides a hydraulic fluid composition comprised of a mixture of about 20% to about 90% by weight of a trialkoxyalkyl-phosphate, about 10% to about 80% by weight of a synthetic ester diluent, and about 0.1% to about 2% by weight of a high molecular weight polymer. In a preferred embodiment, the trialkoxyalkyl-phosphate is tributoxyethyl-phosphate and the synthetic ester diluent is selected from the group consisting of polyol esters of C
6
-C
18
acids and dibasic acid esters of monohydric alcohols.
In a further aspect, the present invention provides a hydraulic fluid composition comprised of a mixture of about 20% to about 90% by weight of a trialkoxyalkyl-phosphate, about 10% to about 80% by weight of a polypropylene glycol diluent, and about 0.1% to about 2% by weight of a high molecular weight polymer. In a preferred embodiment, the trialkoxyalkyl-phosphate is tributoxyethyl-phosphate and the polypropylene glycol diluent is selected from the group consisting of polypropylene glycols of the general formula:
R
1
O—[CH
2
—CH(CH
3
)—O]
n
—R
2
where R
1
and R
2
are independently selected from the group consisting of H, an alkyl, alkenyl, and alkadienyl chains of from 1 to 18 carbons and n=3-40.
In yet another aspect, the invention provides for the optional addition to any of the above-described hydraulic fluids of at least one compound selected from the following groups: about 0.5% to about 5% by weight antioxidant, about 0.1% to about 2% by weight corrosion inhibitor, about 0% to about 2% by weight antiwear agent, and about 0% to about 10% by weight viscosity modifier.
Further objects, features, and advantages of the present invention will become apparent from the detailed description of the invention and the preferred embodiments that follows.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides novel fire-resistant hydraulic fluid compositions. One such fluid contains a mixture of a trialkoxyalkyl-phosphate and a natural triglyceride diluent. Another hydraulic fluid of the invention contains a mixture of a trialkoxyalkyl-phosphate and a synthetic ester diluent. Still other fluids of the invention contain a trialkoxyalkyl-phosphate and mixtures of both a natural triglyceride and a synthetic ester. Still another hydraulic fluid of the invention contains a mixture of a trialkoxyalkyl-phosphate and a polypropylene glycol diluent. Yet another hydraulic fluid of the invention contains a trialkoxyalkyl-phosphate and a mixture of a synthetic ester and a polypropylene glycol diluent. Another hydraulic fluid of the invention contains a trialkoxyalkyl-phosphate and a mixture of a natural triglyceride and a polypropylene glycol diluent. In still another hydraulic fluid of the invention, a trialkoxyalkyl-phosphate is mixed with a diluent comprised of a mixture of a natural triglyceride, a synthetic ester, and a polypropylene glycol. Desirably, these compositions also contain a high molecular weight polymer, as defined herein.
The inventors have found that the use of the hydraulic fluid compositions of the present invention improves fire resistance. As used herein, “fire resistance” refers to the ability of a fluid to pass the flame propagation and hot surface ignition tests described below in Example 7. The hydraulic fluid compositions also have a lower heat of combustion compared to hydraulic fluids lacking phosphate esters. See, e.g., Table II of Example 1.
Hydraulic fluids of the present invention contain between about 20% to about 90% by weight of a trialkoxyalkyl-phosphate. Trialkoxyalkyl-phosphates may be represented by the general formula: (R
3
—O)
3
P=O where R
3
is (C
n
H
2n+1
—O—C
m
H
2m+1
) where n is between 1 and 18 and m is between 2 and 6. These trialkoxyalkyl-phosphates are further characterized as having a high flash point and a low heat of combustion, and as being nontoxic and environmentally acceptable. In a preferred embodiment, the trialkoxyalkyl-phosphate is tributoxyethyl-phosphate. However, any trialkoxyalkyl-phosphate of the above formula may readily be incorporated in the compositions of the present invention.
The preferred hydraulic fluids of the invention also may contain between about 10% to about 80% of a natural triglyceride as a diluent. The natural triglycerides used in the hydraulic fluid compositions of the present invention are glycerol esters of fatty acids, and the chemical structure of these esters can be defined by the following formula:
wherein R
4
, R
5
, and R
6
can be the same or different and are selected from the group consisting of saturated and unsaturated straight-chained alkyl, alkenyl, and alkadienyl chains of 9 to 22 carbon atoms. These triglycerides are further characterized by having a high flash point (over 500° F. C.O.C.). As defined herein “C.O.C.” refers to the Cleveland Open Cup test, a standard measurement of flash point.
Several modified versions of these natural triglycerides may be included in the hydraulic fluids of the present invention. Such modifications may be made in the natural triglycerides by oxidation, polymerization, hydrogenation, and transesterification thereof.
Conventional animal fats and vegetable oils provide a convenient source for the natural triglyceride diluents useful in the invention. In a preferred embodiment, the vegetable oil is canola oil. Other suitable vegetable oils include corn oil, cottonseed oil, sunflower oil, peanut oil, soybean oil, coconut oil, Jojoba oil, castor oil, palm oil, and palm kernel oil. These natural triglycerides are readily available from commercial sources, including, for example, Calgene, Inc., Pfau, Inc., Acme Hardestry, Inc., and Resource Material Corp.
These natural triglycerides have numerous properties which are advantageous in hydraulic fluids. The use of natural triglycerides as diluents in hydraulic fluids confers the benefit of a low cost, renewable, natural resource which is environmentall
Adams Richard
Holgado Rosauro V.
Talaty Chan
Gupta Yogendra N.
Hamlin D
Houghton Technical Corp.
Howson and Howson
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