Low viscosity functional fluids compositions

Details Low viscosity functional fluids compositions Low viscosity functional fluids compositions

2000-11-10

2003-05-06

Gupta, Yogendra N. (Department: 1751)

Compositions

Heat-exchange, low-freezing or pour point, or high boiling...

Organic components

C252S073000, C252S072000, C252S075000, C252S071000, C508S279000, C508S280000, C508S283000

Reexamination Certificate

active

06558569

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to low viscosity functional fluids which are useful in a variety of applications and in particular as brake fluids for new anti-lock brake systems which require lower viscosity fluids for satisfactory operation at low temperatures.
BACKGROUND OF THE INVENTION
Functional fluid compositions based on borate esters are well known in the art. To be useful as DOT 4 or DOT 5.1 brake fluids, these borate ester based compositions must meet stringent physical property and performance requirements particularly with respect to minimum dry equilibrium reflux boiling point (ERBP), minimum wet equilibrium boiling point (WERBP) and maximum low temperature (−40° C.) viscosity while maintaining adequate resistance to corrosion, stability and meeting other physical property requirements such as pH, reserve alkalinity, rubber swell, etc. The minimum ERBP, WERBP and maximum viscosity requirements, as defined in Federal Motor Vehicle Standards 116, are set forth in the following Table 1:
TABLE 1
DOT 4
DOT 5.1
ERBP ° C.
230
260
WERBP ° C.
155
180
−40° C. viscosity cSt
1800
900
Recently developed equipment such as electronic or automated anti-lock braking systems has created a need for high performance brake fluids having even better physical and performance properties than those specified in Table 1. In particular, there is a strong demand for high performance brake fluids having low temperature viscosities which are considerably less than those specified in Table 1 while meeting or exceeding the minimum ERBP and WERBP temperature requirements. High performance brake fluids having low temperature viscosities below about 700 centistokes for a DOT 5.1 fluid and below about 500 centistokes for a DOT 4 fluid are being sought for use in these recently developed brake systems.
The ability to formulate borate ester based brake fluids having low temperature viscosity below about 700 centistokes and even lower for DOT 4 fluids while maintaining sufficiently high ERBP and WERBP temperatures has proven to be a difficult challenge for the industry. Sufficient borate ester must be present in the fluid to provide the desired high ERBP and WERBP temperatures. However, larger amounts of borate esters in the fluid composition tends to raise the low temperature viscosity beyond acceptable levels. In addition, many conventional brake fluid additives such as alkanol amine corrosion inhibitors tend to raise the low temperature viscosity of the fluid especially at levels required to maintain pH stability of the fluid. Thus brake fluid compositions having very low viscosity are still being sought.
The prior art discloses a variety of efforts to lower the viscosity of borate ester based brake fluids while maintaining sufficiently high ERBP and WERBP temperatures. For example, U.S. Pat. No. 4,371,448 discloses a borate ester based brake fluid containing a significant amount of a bis(ethylene glycol monoalkyl ether) as an essential component. EP 0 750 033 and EP 0 617 116 disclose attempts to lower the viscosity of borate ester based brake fluids by substituting a complex compound or mixture of compounds for conventional corrosion inhibitors. All of these efforts involve introducing complex and expensive ingredients into the brake fluid while failing to achieve applicant's objective of reducing the low temperature viscosity of the borate ester based brake fluid below 700 centistokes for a fluid otherwise meeting DOT 5.1 specifications and below about 500 centistokes for a fluid otherwise meeting DOT 4 specifications.
SUMMARY OF THE INVENTION
According to the present invention, applicants have discovered some unique combinations of compositions having sufficiently high ERBP and WERBP temperatures to meet or exceed requirements of DOT 4 and 5.1 fluids and a low temperature viscosity (−40° C.) below about 700 centistokes for DOT 4 and 5.1 fluids and preferably below about 500 centistokes for DOT 4 fluids. The novel functional fluid compositions of the present invention are prepared from readily available, inexpensive components and comprise a specifically defined borate ester component, a specifically defined alkoxy glycol component and one of a number of typical additive packages.
DESCRIPTION OF THE INVENTION
The novel low viscosity functional fluids of the present invention comprise
(a) from 35 to 70 percent by weight, based on the weight of the total composition, of an alkoxy glycol borate ester component having the formula
[RO(CH
2
CH
2
O)
n
]
3
—B
wherein R is methyl, ethyl, propyl or butyl, or mixtures thereof, n is essentially 2 to 4, and wherein borate ester in which n=3 is greater than about 90 percent by weight, based on the total weight of the borate ester component,
(b) from about 25 to about 65 percent by weight, based on the total weight of the composition of an alkoxy glycol component having the formula
RO(CH
2
CH
2
O)
n
H
wherein R is an alkyl group containing 1 to 8 carbon atoms or mixtures thereof, n is essentially 2 to 4, alkoxy glycol in which n=2 is present in an amount of from about 1 to about 88 percent by weight, based on the total weight of the alkoxy glycol component, alkoxy glycol in which n=4 is present in an amount of from about 0 to about 20 percent by weight, based on the total weight of the alkoxy glycol component, and
(c) from 0.3 to about 10 percent by weight, based on the total weight of the composition of an additive package which contains one or more of the following: corrosion inhibitor, antifoaming agent, pH stabilizer and antioxidant,
wherein the total of components (a) and (b) in which n=2 is from about 1 to about 45 percent by weight, based on the total weight of the composition and the total of components (a) and (b) in which n=4 is from about 0 to about 10 percent by weight, based on the total weight of the composition.
Fluid compositions of the present invention having an ERBP of at least 240° C., a WERBP of at least 165° C. and a low temperature viscosity of less than 500 centistokes are obtained when in component (a) n=3 is greater than 90 percent by weight, in component (b) n=2 is from about 12 to 88 percent by weight and n=4 is from about 0 to 10 percent by weight, the total of components (a) and (b) in which n=2 is from about 8 to 45 percent by weight and the total of components (a) and (b) in which n=4 is from about 0 to 6 percent by weight.
Fluid compositions of the present invention having an ERBP of at least 260° C., a WERBP of at least 180° C. and a low temperature viscosity of less than 700 centistokes are obtained when in component (a) n=3 is greater than 95 percent by weight, in component (b) n=2 is from about 1 to 12 percent by weight and n=4 is from about 0 to 20 percent by weight, the total of components (a) and (b) in which n=2 is from about 1 to 8 percent by weight and the total of components (a) and (b) in which n=4 is from about 0 to 10 percent by weight.
Component (a) of the functional fluid compositions of the present invention are alkoxy glycol borate esters represented by the formula
[RO(CH
2
CH
2
O)
n
]
3
—B
wherein R is methyl, ethyl, propyl or butyl, or mixtures thereof, n is essentially 2 to 4, and wherein borate ester in which n=3 is greater than about 90 percent by weight, based on the total weight of the borate ester component. Borate esters and their methods of preparation are well known in the art. Borate esters useful in the functional fluid compositions of the present invention may be prepared by reacting boric acid with a suitable alkoxy glycol component which is typically a selective mixture of alkoxy glycols containing at least 90 percent by weight, preferably 95 percent by weight of the alkoxy triethylene glycol species.
Examples of useful borate esters include those containing methoxy triethylene glycol borate ester, ethyl triethylene glycol borate ester, butyl triethylene glycol borate ester and mixtures thereof. Particularly good results have b

Affiliated with

Also associated with

Rating

Low viscosity functional fluids compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Low viscosity functional fluids compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low viscosity functional fluids compositions will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3041279