Antiwear additives for functional fluids

Certain heretocyclic hydrogen phosphonates are disclosed as having utility in functional fluids, particularly synthetic lubricants and/or water-based functional fluids. Antiwear characteristics and other properties are improved by the blending of additives such as spiro-bis-hydrogen phosphonate and cycloneopentyl hydrogen phosphonate with non-petroleum base stocks such as water, phosphate esters, and mixed polyalphaolefins/polyol esters. Preferred formulations are disclosed.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to the use of specific heterocyclic hydrogen 
phosphonates as antiwear additives in functional fluids, and the 
compositions thereby obtained. More particularly, the invention relates to 
the use of spiro-bis-hydrogen phosphonate and cycloneopentyl glycol 
hydrogen phosphonate and related products. The functional fluids are 
particularly synthetic lubricants and/or water-based fluids (rather than 
petroleum-based products). 
2. Prior Art 
The use of antiwear additives in functional fluids is extremely old in the 
art. Spiro-bis-hydrogen phosphonate and cycloneopentyl glycol hydrogen 
phosphonate are both known in various physical forms. However, neither 
compound is now known to have been actually used as an antiwear additive 
in a non-petroleum based functional fluid. 
Spiro-bis-hydrogen phosphonate (hereinafter "Compound A") is indexed by 
Chemical Abstracts Service (CAS) under the name pentaerythritol 
diphosphite and Register No. 2723-44-6. CAS has apparently indexed only 
three references, according to a computer search. These are discussed 
below. 
Russian Pat. No. 476,267 describes spiro-bis-hydrogen phosphonate as being 
a useful intermediate for insecticides and flame-proofing agents. The 
patent includes a method of preparation that is quite similar to the 
method used herein. It gave a 100% yield of a white crystalline powder 
melting at 90.degree.-95.degree. C. (in contrast to about 170.degree. C. 
in Examples 1B-1D hereinafter). 
The CAS reference CA65:10719c is apparently a miscite. 
"Pentaerythritol Phosphite Condensation Polymers" by L. Friedman and H. 
Gould in Am. Chem. Soc., Div. Polymer Chem., Preprints 4(2), 
98-101(1963)(Eng) is primarily directed to polymers intended for flame 
retardant applications. In general, "many of these polymers have 
interesting properties but were too unstable towards moisture to be 
effective as materials of construction". However, "they are quite 
effective as additives in stabilizing other polymer systems, such as 
polyethylene . . . against oxidative and thermal degradation". All of the 
polymers were prepared from raw materials including diphenyl 
pentaerythritol diphosphite, rather than pentaerythritol diphosphite. At 
least three of the references cited by Friedman and Gould are of interest. 
In particular, see U.S. Pat. No. 3,053,878 (Friedman and Gould); U.S. Pat. 
No. 3,047,608 (Friedman and Gould); and U.S. Pat. No. 2,847,443 
(Hechenbleikner and Lanoue). However, they do not appear to disclose or 
suggest the invention claimed hereinafter. 
Cycloneopentyl glycol hydrogen phosphonate (hereinafter "Compound B") is 
old in the art. Three U.S. Patents are discussed below. 
U.S. Pat. No. 3,152,164 (Oswald) relates to the preparation of compounds 
such as Compound B by transesterification of a phosphite diester with a 
glycol. Oswald suggests that the cyclic organic phosphorus compounds of 
his invention will be of particular advantage due to their increased 
thermal and hydrolytic stability as petroleum additives themselves or can 
be used as starting materials for the preparation of additives (see Col. 
2, lines 65-69). 
U.S. Pat. No. 2,916,508 (McConnell) describes the preparation of Compound B 
(shown at Col. 2, line 10). The proposed enduses are merely insecticides, 
stabilizers for polyesters and artificial resins, fungicides, and other 
related uses. 
U.S. Pat. No. 2,899,455 (Coover et al.) concerns derivatives of Compound B 
obtained by addition-type reactions. The derivatives are described as 
being useful as pesticides, plasticizers, solvents, flame-proofing agents 
and intermediates. 
Essentially, nowhere does the now-known aforementioned prior art disclose 
or suggest that Compound A or Compound B or closely related compounds have 
utility in water-based functional fluids or synthetic functional fluids. 
SUMMARY OF THE INVENTIOn 
In contrast to the aforementioned prior art it has now been discovered that 
certain species of hydrogen phosphonate are eminently suitable for use as 
additives in water-based functional fluids. Some of the species suitable 
for water-based applications are also suitable for synthetic functional 
fluid applications. The broadest aspects of the invention are described in 
the independent claims hereinafter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments of the invention are shown in the claims 
hereinafter. They are illustrated by the Examples below contrasted to both 
the prior art and the Comparatives Examples below. 
The process of this invention reduces the wear in apparatus having moving 
parts separated by a functional fluid that is at least 90 percent by 
weight a non-petroleum base stock, B. It comprises dispersing in B up to 
10 percent by weight of an additive comprising a first heterocyclic 
compound, C1, or a second heterocyclic compound, C2, or mixtures thereof. 
Numerous non-petroleum base stocks may be used in this invention. Numerous 
heterocyclic compounds C1 and/or C2, likewise may be used. It is normally 
required that the additive C1 and/or C2 be capable of dissolving in B, 
since this simplifies dispersion. 
Preferred variants of B include neat water-based systems; phosphate ester 
bases; and mixed polyalphaolefin/polyol ester bases. 
A preferred variant of C1 is spiro-bis-hydrogen phosphonate (Compound A) 
which has the following structural formula: 
##STR1## 
A preferred variant C2 of cycloneopentyl glycol hydrogen phosphonate 
(Compound B) having the following structural formula: 
##STR2## 
In general, C1 has the following structural formula: 
##STR3## 
wherein: Y is oxygen or sulfur; 
W is hydrogen or an alkali metal; and 
m, n, and m plus n, all have values of 0, 1, 2, 3 or 4. 
In general, C2 has the following structural formula: 
##STR4## 
wherein: Y, W, m, and n are as defined for C1; and 
R.sup.1 -R.sup.6 are individually selected from hydrogen and saturated 
hydrocarbyl radicals containing from one to 10 carbon atoms. 
Methods for preparing Compound A and Compound B are given in the Examples 
below. Method for preparing other variants of C1 and C2 respectively may 
be obvious variants of the foregoing method of preparing Compound A and 
Compound B, as indicated below. 
Compounds wherein Y is sulfur rather than oxygen may be prepared by 
substituting 1 mole of P.sub.2 S.sub.5 for each 2 moles of PCl.sub.3 and 
using an appropriate catalyst. 
Compounds wherein W is an alkali metal such as sodium or potassium, rather 
than hydrogen, may be prepared by reacting Compound A and/or Compound B 
with the appropriate metal hydride. 
Compounds wherein m, n, and m plus n have values of 1, 2, 3, or 4, may be 
prepared by replacing pentaerythritol by the corresponding tetrahydroxyl 
compound. 
Compounds wherein R.sup.1 -R.sup.6 are saturated hydrocarbyl radicals 
rather than hydrogen may be prepared according to the process for 
preparing Compound B except that 2,2-dimethyl-1,3-propanediol is replaced 
by the corresponding dialkyl-1,3-propanediol. 
The preferred combined amount of C1 and C2 in this invention is a maximum 
of 5 weight percent. More preferably, it is in the range from 0.5 to 2.5 
weight percent. Optimum values within these ranges will depend upon the 
remaining constituents of the functional fluid. 
It should be noted that both Compound A and Compound B hydrolyze slowly in 
the presence of water. Accordingly, when B is water, it will be necessary 
to replenish or replace the functional fluid periodically. In practice, 
this does not pose a problem for many applications. 
Preparation of Compounds A and B 
Compound A was prepared in a manner similar to that given in the CAS 
abstract of aforementioned Russian Patent No. 476,267. The synthesis 
involved esterification of pentaerythritol with PCl.sub.3 to form the 
spiro-bis chloro phosphite in near quantitive yield. The esterification 
was run in CHCl.sub.3 solvent with a catalytic quantity of pyridine. The 
intermediate chlorophosphite was not isolated but treated with t-butanol 
at 25.degree. C. to give a near quantitative yield of the hydrogen 
phosphonate. The product was merely filtered from the reaction solution 
and dried. An earlier experiment under similar conditions indicated that 
the hydrogen phosphonate was an off-white powder with a m.p. of 
172.degree.-175.degree. C. (in contrast to 92.degree.-95.degree. C. as 
reported in the Russian patent). .sup.31 P-NMR analysis indicated one 
phosphorus environment. H-NMR indicated P-H and ring protons in a 1:4 
ratio respectively. IR showed no OH absorption but a strong P-H bond at 
2440 cm.sup.-1. Titration for P.sup.III indicated 98.3% of theory. 
Compound B was prepared essentially according to aforementioned McConnell's 
U.S. Pat. No. 2,916,508, Example 2. 
Solubility of Compound A and B 
Compounds A and B were evaluated for solubility in various functional 
fluids at room temperature. Compound A was found to be soluble in water, 
but insoluble in petroleum based oil. Compound B was found to be insoluble 
in paraffinic oil; but soluble in phosphate ester, polyol ester (short 
chain), polyalphaolefins, and water. 
Comparative Antiwear and Load Bearing Trials 
Four comparative trials were performed. Within each trial of several 
experiments, (1) Compound A or Compound B or a possible competing compound 
was conventionally dissolved in a given base stock; and (2) the resultant 
solutions were evaluated for antiwear properties by ASTM D-2266 and/or 
extreme pressure properties by ASTM D-2783 and/or oxidation corrosion data 
by Federal Test Method Procedure 791B (Method 5308.6). The base stocks 
used in these trials were as follows: 
(i) Neat High Water Based System 
PLURASAFE P 1200 Hydraulic Fluid Concentrate was obtained from BASF 
Wyandotte Corporation. According to BASF's Technical Bulletin (dated 1983 
or earlier) PLURASAFE P 1200 Hydraulic Fluid may be made by adding 1 part 
of the concentrate to 9 parts of tap water, and stirring with a Lightnin' 
Mixer or other comparable device. This was done except that distilled 
water was used. The technical Bulletin states that the so-diluted 
concentrate is a thickened high water hydraulic fluid ready to use. It has 
undefined vapor-phase corrosion protection, lubricant additives and 
anti-corrosive additives as part of its formulation. PLURASAFE P 1200 
Hydraulic Fluid is stated to overcome the deficiencies of unthickened high 
water fluids which are due to low viscosity. Unthickened fluids tend to 
exhibit low efficiency at high pressure, high leakage rates, and the 
wire-draw type of erosion. 
Typical characteristics of ready-to-use PLURASAFE P 1200 Hydraulic Fluid 
include the following: 
______________________________________ 
Specific Gravity, 100.degree. F. 
0.999 
Viscosity at 100.degree. F., SUS 
200 .+-. 50 
Freezing Point, .degree.F. 
32 
Boiling Point .degree.F. 
212 
pH at 25.degree. C. 9.8 .+-. 0.2 
Reserve Alkalinity 
ml 0.1 N HCl/10 ml sample 
5.6 
(ml 0.IN HCl/50 ml sample) 
25-30 
Flash Point None 
Color Hazy blue 
Odor Fruity odor 
______________________________________ 
The Technical Bulletin also indicates that the optimum temperature for use 
of PLURASAFE P 1200 Hydraulic Fluid is 100.degree. F. However, any 
temperature between 80.degree. F. and 120.degree. F. is acceptable. 
(ii) Phosphate Ester Base 
The phosphate ester base was essentially t-butylphenyldiphenyl phosphate 
(Stauffer Chemical Company's SOA-8478). 
(iii) Mixed Polyalphaolefin/Polyol Ester Base 
This base was prepared by conventionally blending four parts of 
poly-alpha-decene (obtained from Mobil Corporation as a 6 cst fluid) with 
one part by weight of trimethylolpropane triheptanoate (Stauffer Chemical 
Company's Base Stock 704). 
TRIAL 1 
Compound A/Neat High Water Based System 
In Examples 1A (Comparative), 1B, 1C, and 1D, respectively, Compound A was 
dissolved in the neat high water based system at concentrations of 0; 0.5; 
1.0; and 2.0 weight percent. The wear preventive characteristics (four 
ball method) were determined under ASTM D 2266 procedures at 40 kg load, 
room temperature, for 1 hour, at speeds of (i) 600 RPM and (ii) 1800 RPM. 
The wear scars obtained are shown in Table 1 below. 
TABLE 1 
______________________________________ 
Compound A Wear Scar (mm) 
Wear Scar (mm) 
Ex. No. (wt. %) at 600 RPM at 1800 RPM 
______________________________________ 
1A (Comp) 
0 0.84 1.14 
1B 0.5 0.75 0.88 
1C 1.0 0.65 0.94 
1D 2.0 0.65 1.04 
______________________________________ 
The weld point of Example 1A (Comp) was only 80 kg in contrast to 126 kg of 
Example 1C (as tested in accordance with ASTM D-2783). 
TRIAL 2 
Compound B/Neat High Water Based System 
Trial 2 was similar to Trial 1 except that Compound B was substituted for 
Compound A. The wear preventive characteristics are shown in Table 2. 
TABLE 2 
______________________________________ 
Compound B Wear Scar (mm) 
Wear Scar (mm) 
Ex. No. (wt. %) at 600 RPM at 1800 RPM 
______________________________________ 
2A 0.0 0.84 1.14 
2B 0.5 0.75 0.87 
2C 1.0 0.70 0.90 
2D 2.0 0.70 0.94 
______________________________________ 
TRIAL 3 
Compound B/Phosphate Ester Base 
Compound B was compared with three prior art compounds as an additive in 
the phosphate ester base, as shown in Table 3 below. The wear scar test 
was carried out according to ASTM D 2266 at 600 RPM, 40 kg, for three 
sequential 30 minute runs. 
TABLE 3 
______________________________________ 
Wear Scar (mm) 
Ex. No. Additive 200.degree. F. 
400.degree. F. 
500.degree. F. 
550.degree. F. 
______________________________________ 
3A(Comp) 
None .63 .73 .93 .81 
3B 1 wt % cpd. B 
.58 .62 .62 1.2 
3C(Comp) 
1 wt % Dibutyl 
.60 .75 1.2 1.4 
Phosphite 
3D(Comp) 
1 wt % Diphenyl 
.63 .88 1.3 1.2 
Phosphite 
3E(Comp) 
1 wt % Zinc .49 .73 .87 1.3 
Dialkyl 
Dithiophosphate 
______________________________________ 
TRIAL 4 
Compound B/Mixed Pao/Polyol Ester 
Compound B was compared with two prior art compounds as an antiwear 
additive in the mixed polyalphaolefin/polyol ester base. The wear test was 
carried out under ASTM D 2266 at 600 RPM, 40 kg load, for one hour at the 
temperatures indicated in Table 4A below. 
TABLE 4A 
______________________________________ 
Wear Scar (mm) 
Ex. No. Additive 225.degree. F. 
275.degree. F. 
300.degree. F. 
______________________________________ 
4A(Comp) None .55 .60 .46 
4B 1 wt. % Cpd. B 
.48 .47 .41 
4C(Comp) 1 wt % Dibutyl 
.52 .55 .57 
Phosphite 
4D(Comp) 1 wt % Zinc .45 .49 .49 
Dialkyl Dithio- 
phosphate 
______________________________________ 
The blends were also tested according to ASTM D-2783 for Last Non Seizure 
Point (LNS); Weld Point (WP); and Load Wear Index (LWI). The results are 
shown in Table 4B below. 
TABLE 4B 
______________________________________ 
Ex. No. LNS WP LWI 
______________________________________ 
4A(Comp) 20 100 11.1 
4B 32 160 32.4 
4C(Comp) 20 126 34.7 
4D(Comp) 32 126 20.9 
______________________________________