Water base hydraulic fluid

A water base hydraulic fluid is disclosed. The fluid comprises 40 wt % of an amphoteric surfactant of the formula: EQU CH.sub.3 (CH.sub.2).sub.5 --CH(CH.sub.3)--NHCH.sub.2 CH.sub.2 COOH and 10 wt % polypropylene glycol in water. The diluted hydraulic fluid is noted for its good wear characteristics, anticorrosiveness and non foaming nature.

BACKGROUND OF THE INVENTION 
This invention relates to a water base fluid, particularly to a water base 
hydraulic fluid which is noted for antiwear properties and 
noncorrosiveness. 
DESCRIPTION OF THE PRIOR ART 
Water-base hydraulic fluids are particularly valuable because of their fire 
resistant properties. They find use particularly in mining and other 
services such as aircraft, automotive, steel and lumber where fire is an 
exceptional concern. 
Water-base hydraulic fluids have better coolant compatibility, better heat 
transfer properties, are less polluting and are non-oxidizing compared to 
conventional petroleum base hydraulic fluids. However, water-base fluids 
are typically deficient in extreme pressure and antiwear properties which 
limit their usefulness to applications where they are required. It is the 
object of this invention to provide a water based fluid with improved 
properties. 
U.S. Pat. No. 4,238,350 describes a corrosion inhibiting liquid. 
SUMMARY OF THE INVENTION 
The present invention comprises a water base fluid comprising a major 
amount of an amphoteric surfactant and a minor amount of polypropylene 
glycol. The amphoteric surfactant in an amount of 35 to 45 wt % is of the 
formula: 
EQU CH.sub.3 (CH.sub.2).sub.5 --CH(CH.sub.3)--NHCH.sub.2 CH.sub.2 COOH 
The polypropylene glycol is of molecular weight 200 to 600. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention is a water base fluid composition comprising: 
(a) 35 to 45 wt % of an amphoteric surfactant of the formula: 
##STR1## 
(b) 5 to 15 wt %; preferably 8 to 12 wt %, of polypropylene glycol of 
molecular weight 200 to 600; and 
(c) water. 
The composition may additionally comprise rust inhibitor, aluminum 
corrosion inhibitor, copper corrosion inhibitor or mixtures thereof. 
Laboratory tests have shown that the compositions of the present invention 
after dilution with water provide good rust protection and antiwear 
properties with superior foam inhibition. This is unexpectedly achieved 
without steel staining or etching. These compositions do not settle and 
they demonstrate good freeze thaw characteristics. 
In this regard, the present invention is a concentrated hydraulic fluid 
comprising: 
(a) 35 to 45 wt % of an amphoteric surfactant of the formula: 
##STR2## 
(b) 8 to 12 wt % polypropylene glycol of molecular weight 200 to 600; (c) 
triethanolamine, diethanolamine and modified phosphate ester in an amount 
sufficient to inhibit rust; 
(d) phosphoric acid in an amount sufficient to inhibit aluminum corrosion; 
(e) benzotriazole in an amount sufficient to inhibit copper corrosion; and 
(f) water. 
The composition is prepared by stirring the constituents in a stainless 
steel kettle at 100.degree. F. The blends are then diluted with the 
desired amount of water to make the concentrate. 
These fluids are shipped as concentrates. Before use they are diluted with 
water, typically 2 wt % to 10 wt % concentrate in water. Standard 
dilutions are 2 wt %, 5 wt % and 10 wt % concentrate in water, with 5% 
being the industry standard.

This invention is better shown by way of example. 
EXAMPLE 1A 
One of the corrosion tests passed by the composition of the present 
invention was a Modified ASTM D 665 Rust Test. In this modified test a 
cylindrical steel specimen was polished by successive grinding with 150 to 
240 grit aluminum oxide abrasive cloth. The steel specimen was inserted in 
a rubber stopper equipped with a hole. Sufficient quantity of the fluid 
composition to be tested was charged to a flask such that when the 
specimen was in place in the flask, approximately one-half of the specimen 
was immersed. The flask, test solution and specimen were placed in an oil 
bath maintained at a temperature of about 140.degree. F. (55.5.degree. 
C.). The portion of the steel specimen subjected to vapor and the portion 
subjected to the liquid portion of the fluid were rated after the first 
hour for evidence of rusting and again after completion of the first 24 
hour test period. The rating system used was similar to that defined by 
MIL-L-24467. This rating system defined no rust as being no rust visible 
on the specimen, trace rust as being 1-6 rust specks of no more than 1 
millimeter in diameter, light rust as being 7-12 rust specks, moderate 
rust was an overall light rust, and heavy rust was an overall heavy rust 
or heavy rust spots. 
The composition of the present invention was tested for foaming according 
to Test Method ASTM D 892 Sequences I, II and III. In the Sequence I Test 
approximately 200 milliliters of samples were decanted into a beaker and 
were heated to about 49.degree. C. and then allowed to cool to about 
24.degree. C. The cooled sample was then poured into a 1000 milliliter 
cylinder until the liquid level was at the 190 milliliter mark. The 
cylinder was then immersed to at least the 900 milliliter mark in a bath 
maintained at about 24.degree. C. A diffuser stone and air inlet tube were 
then inserted into the cylinder and into the sample. About 94 milliliters 
of air per minute were forced through the stone for about 5 minutes. At 
the end of the period the air flow was shut off and the total volume of 
foam was measured and then measured again after ten minutes of waiting. 
In the Sequence II Test, a second portion of sample was poured into a 1000 
milliliter cylinder until the liquid level was at the 180 milliliter mark. 
The cylinder was immersed into a bath maintained at a temperature of about 
93.5.degree. C. A diffuser stone was then immersed into the sample in the 
cylinder and the test was carried out as in the Sequence I Test. 
In the Sequence III Test, any foam remaining after the Sequence II Test was 
collapsed, the sample was then allowed to cool to a temperature below 
about 43.5.degree. C. and then further cooled to a temperaure of about 
24.degree. C. A gas diffuser stone was inserted and the test was then 
carried out as in Sequence I and II. The composition of the present 
invention produced low or no foaming in all sequences. Low foaming is an 
important characteristics of hydraulic fluids. 
The Load Wear Index (LWI) refers to the load carrying property of a fluid. 
It is the index of the ability of a fluid to prevent wear at applied 
loads. Under the conditions of the test, specific loadings in kilograms 
having intervals of 0.1 logarithmic units are applied to three stationary 
balls for ten runs prior to welding. The test procedure is described in 
ASTM D 2596. The Four Ball Wear Test determines wear preventive 
characteristics in sliding steel-on-steel applications carried out as 
described in ASTM D 2266. 
In the Chip Rust Test, approximately 15 ml of clean, dry cast-iron chips 
are soaked in the test fluid. The fluid is drained and the chips are then 
spread evenly over the bottom of a 100 mm diameter Petri dish. After 
drying for 16 hours, the chips are then rated for rust. The rusting of 11 
or more chips constitutes a "fail". 
In the Plate Rust Test, a clean, cast-iron plate 10 
3/4".times.81/2".times.1/2" cross-hatched into 252 equal squares is 
polished by rubbing under oil with No. 150 grade emery cloth. After the 
plate has a mirror finish, the oil is wiped off with tissue paper and 
washed free of oil with acetone. One drop of the test fluid is placed onto 
a square. One drop of a standard fluid (for high water base fluids a 
competitive product was used) is placed on the square beneath the test 
fluid. After standing for 24 hours, the plate is examined for any sign of 
corrosion, pitting, etching, or pink, red or brown discoloration. If any 
of the above are observed, the test fluids fails this test. 
In the Modified ASTM D 2882 Pump Test, five gallons of the test hydraulic 
fluid is circulated through a rotary vane pump rig for 100 hours derated 
to 500 psi, 1200 RPM and room temperature. At the conclusion of the test, 
the weigt loss on the cam ring and vanes of the pump rig are observed. The 
pump cartridge is observed for signs of wear, deposit formation and 
discoloration. The test fluid is observed for discoloration or unusual 
odor. Compositions A and B were compounded according to the procedure 
described herein. 
MA-200 is the amphoteric surfactant of the formula: 
##STR3## 
__________________________________________________________________________ 
EXAMPLE 1A 
A B 
__________________________________________________________________________ 
Concentrate Composition, wt % 
MA-200 40.0 20.0 
Deionized Water 29.0 49.0 
JEFFOX .RTM. PPG-400 (Polypropylene 
10.0 10.0 
glycol, MW 400) 
Triethanolamine 10.0 10.0 
Diethanolamine 5.0 5.0 
UNIHIB .RTM. 2000 (modified phosphate 
4.0 4.0 
ester) 
Phosphoric Acid, 85% 1.0 1.0 
Benzotriazole 1.0 1.0 
Blue Dye (ppm) (50 ppm) 
(50 ppm) 
Tests - Concentrated 
Appearance Clear Blue 
-- 
Specific Gravity 60/60.degree. F. 
1.0536 -- 
Viscosity, cst, 40.degree. C. 
18.40ck18.58 
-- 
65.6.degree. C. 7.83ck7.84 
-- 
Pour .degree.F. 
20ck-20 -- 
Freeze-Thaw Cycle, 5 days 
No Change 
-- 
Oven Stability, 150.degree. F. 
Amber -- 
__________________________________________________________________________ 
Competitive 
Competitive 
Competitive 
Product Product Product 
1 2 3 
__________________________________________________________________________ 
Tests - Concentrate 
Appearance Blue, Separated 
Yellow Blue, Separated 
Specific Gravity 60/60.degree. F. 
1.0414ck1.0223* 
-- 1.0614 
Viscosity, cSt, 40.degree. C. 
25.7 -- 451.9 
65.6.degree. C. 
-- -- 160.0 
Pour .degree.F. 
-- -- 10 
Oven Stability 
Separated, 1 cycle 
-- Separated, 4 Cycles 
__________________________________________________________________________ 
EXAMPLE 1B 
A B 
__________________________________________________________________________ 
Diluted Concentrate 
Wt % in water 5 5 
Tests - Diluted 
Appearance Cloudy Blue 
Cloudy Blue 
Viscosity, cSt, 40.degree. C. 
0.77ck0.73 0.81 
65.6.degree. C. 
0.52ck0.51 0.52 
Pour, .degree.F. 
30 30 
Foam (ASTM D 892) SEQ 
I II III 
I II 
III 
Immed. after Blowing, ml. 
30 
10 300 
10 0 30 
After 10 min. settling, ml. 
10 
0 30 
0 0 20 
pH 7.9ck8.5 8.8 
Chip Rust Pass -- 
Plate Rust FailckPass -- 
Modified (ASTM D 665A) 
Vapor Phase Lt.RustckPass 
Mod. Rust 
Liquid Phase PassckPass Pass 
Modified ASTM 
D 2882 Pump Test 
100 Hr., RT., 500 PSI 
1200 RPM 
Wt Loss, Gram/100 Hr. 
-- 2.2147 
__________________________________________________________________________ 
EXAMPLE 2A 
D E 
__________________________________________________________________________ 
Concentrate Composition, wt % 
Deionized Water 31.0 
29.0 
MA-200 40.0 
40.0 
JEFFOX .RTM. PPG-400 10.0 
10.0 
Triethanolamine 10.0 
10.0 
Diethanolamine 4.0 5.0 
UNIHIB .RTM. 2000 4.0 4.0 
Phosphoric Acid -- 1.0 
Benzotriazole 1.0 1.0 
Blue Dye (ppm Added) -- (150) 
100.0 
100.0 
Tests - Concentrate 
Specific Gravity 60/60.degree. F. 
-- 1.0503 
Viscosity, cst, 40.degree. C. 
-- 19.57 
65.6.degree. C. -- 8.29 
Pour, .degree.F. -- -10 
__________________________________________________________________________ 
EXAMPLE 2B 
D E 
__________________________________________________________________________ 
Diluted Fluid, Wt % in Water 
5 5 
Tests - Diluted 
Viscosity, cSt, 40.degree. C. 
0.83 0.75 
65.6.degree. C. 
0.53 0.50 
Pour .degree.F. 
-- -- 
Foam (ASTM D 892) SEQ 
I II III 
I II 
III 
Immed. after Blowing, ml. 
10 
10 10 10 0 50 
After 10 min. settling, ml. 
0 
0 0 0 0 0 
pH 8.9 8.6 
Chip Rust Pass Pass 
Plate Rust Pass Pass 
Mod ASTM D 665A Rust Test 
Vapor Phase FailckPass Pass 
Liquid Phase FailckPass Pass 
Four Ball Wear 
1 Hr, 600 RPM, RT 
--/0.66/0.78 
-- 
1/10/40 Kg mm scar dia 
LWI (Weld Pt), Kg. 
25(126) -- 
__________________________________________________________________________ 
Competitive 
Competitive 
Competitive 
Product Product Product 
1 2 3 
__________________________________________________________________________ 
Diluted Concentrate 
Wt % in water 5 5 5 
Tests - Diluted Fluid 
Appearance Cloudy Blue 
Cloudy Yellow 
Cloudy Blue 
Viscosity, cSt, 40.degree. C. 
0.81 1.18 26.48 
65.6.degree. C. 
-- -- 5.36 
Pour, .degree.F. 
-- -- 30 
Foam (ASTM D 892) SEQ 
I II III 
I II III 
I II III 
Immed. after Blowing, ml. 
450 
20 340 
200 
260 
270 
420 
940 
430 
After 10 min. settling, ml. 
40 
0 50 
60 
6 100 
420 
540 
430 
pH 10.3ck9.9 
9.2 9.7 
Chip Rust Pass Pass Fail 
Plate Rust Pass Pass Fail 
Modified (ASTM D 665A) 
Rust Test 
Vapor Phase Lt.RustckPass 
Pass Mod. Rust 
Liquid Phase PassckPass 
Pass Pass 
Load Wear Index (LWI) 
23 37 26 
Weld Pt, Kg 100 126 126 
Four Ball Wear, mm scar dia 
1 Hr., 600 RPM, RT 
.52/0.67/0.62 
0.46/0.53/0.60 
0.52/0.62/0.76 
1/10/40 Kg load 
Modified ASTM 
D 2882 Pump Test 
100 Hr., RT., 500 psi 
1200 RPM 
Total Wt Loss, 
2.003 1.622ck2.006 
-- 
Gram/100 Hr. 
__________________________________________________________________________ 
*Variable results probably due to product separation 
Product 1 -- Houghton Hydrolubric 120B 
Product 2 -- Lubrizol OS49084 
Product 3 -- BASF Wyandott Plurasafe P1200 Products 1, 2 and 3 are th 
same as those of Example 1A. 
The principle of the invention and the best mode contemplated for applying 
that principle have been described. It is to be understood that the 
foregoing is illustrative only and that other means and techniques can be 
employed without departing from the true scope of the invention defined in 
the following claims.