CA1037940A

CA1037940A - Phosphoric acid ester based functional fluids

Info

Publication number: CA1037940A
Application number: CA200,535A
Authority: CA
Inventors: Alain J. G. De Roocker
Original assignee: Labofina SA
Current assignee: Labofina SA
Priority date: 1973-07-13
Filing date: 1974-05-22
Publication date: 1978-09-05
Also published as: FR2236922A1; NL7406987A; DE2421977B2; AU466401B2; GB1441528A; DE2421977A1; SU530651A3; AU6857774A; DE2421977C3; FR2236922B1; IT1017613B; JPS5039289A; BE802298A; ES427983A1

Abstract

ABSTRACT
A functional fluid comprising a mixture of (A) an orthophosphoric acid ester of formula O = P ? (OR)3, wherein R's, which may be the same or different, are an alkyl radical, an aryl radical or an alkylaryl radical and (B) a transesteri-fication product between a dihydroxy aromatic compound and a phosphorous compound selected from the group consisting of the phosphorous acid ester and phosphoric acid ester

Description

~(~37~0 This inven-tion rela-tes to furlctional fluids having improved viscosity characteristics.
Functional fluids have many applications. 'Ihey are particularly useful as lubricants between moving mechanical parts and as force transmission fluids, such as for example, ``-as hydraulic fluids. In indiustrial uses of -these functional -fluids, the viscosity is of utmost importance, due to the fact that these products are commonly employed under wide ranges of temperature. To obtain satisfactory performance, it is recom~
mended that the functional fluids possess a convenient viscosity-temperature relation and a satisfactory flame resistance.
Many compounds and various compositions have already -~
been suggested as functional fluids. Tricresyl phosphates have been used, but their viscosity index is negative. The `
viscosity index of a fluid is an indication of the viscosity variation of the fluid as a function of the temperature and : .
the most valuable products have a positive index. A negative `~
index for tricresyl phosphates indicates that these products ;~
are not useful throughout the temperature ranges normally a~
... . ~
encountered. ~- -',':' ~' Moreover, the viscosity of many phosphoric acid esters is often too low for the conditions of use which are generally required. To obviate this drawback, phosphoric acid esters having a high molecular weight may be employed. However, the viscosity characteristics at low temperatures are particularly unfavorable for such high molecular weight materials. Another `~
known means for overcoming this disadvantage is by incorporating - viscosity-index improvers, generally polymers such as poly-methacrylates, polyolefines and the like. However, the flame -resistance is substantially decreased.

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It is an object of the presen-t inven-tion -to provide new fllnctional fluids contairling phosphoric acid esters. Ano-ther object of the present invention is to provide functional fluids possessing adequate viscosities at the wide range of temperatures normally encountered in use. Still another ;~
object of the present invention is to provide functional fluids having a low flammability.
According to the present invention, the functional fluids essentially consist of~
A) an orthophosphoric acid ester of formula O = P ~ (OR)3, wherein the R radicals, which may be the same or different, are an aryl, an alkyl or an alkylaryl radical, B) a transesterification product between a dihydroxy aromatic compound and a phosphorous compound selected from the group consisting of phosphorous acid esters of the formula oR2 ,:~
R10 - P - oR3 and phosphoric acid esters of the formula R10 - P - oR3, wherein the Rl, R2 and R3 radicals, which oR2 may be the same or different, are an alkyl, an aryl or an alkylaryl radical.
The components A of the composition hereinabove defined are orthophosphoric acid esters of formula O = P = (OR)3 wherein the R radicals, which may be the same or different, are an alkyl radical generally comprising from l to 8 carbon atoms or an aryl radical, which may have substituen-ts thereto. If a substituent ~ ~-is present, it usually will be an alkyl radical having 1 to 8 carbon atoms. The selection of -the component A which is employed for the production of the compositions of the present invention depends on its properties, more particularly its viscosi-ty characteristics, and also on its price. For instance, tricresyl phosphate, trioctyl phosphate, diphenyl-cresyl-phosphate,

-2-.... .
.. . . , - -: 3 ~375~4V ;`
phenyl-dioctyl-phospha-te and the like may be used. For some applica-tions, phosphoric acid esters con-taining ethylphenyl radicals are particularly useful; such es-ters already have a -high viscosity index, which is substan-tially improved by adding the Component B, hereinabove defined.
The Components B of the composition above defined are transesterification products of a dihydroxy aromatic compound and a phosphorous acid ester or a phosphoric acid ester. `~
Hydroquinone, resorcinol, pyrocatechol, 2,2'-bis(4-hydroxy-phenyl)propane (or bisphenol-A) and bis (~-hydroxyphenyl) methane generally are used as dihydroxy aromatic compounds.
The dihydroxy aromatic compound is transesterified by a phosphorous acid ester R O - P - OR or a phosphoric acid ester R O - P - OR , `~
oR2 oR2 wherein the Rl, R2 and R3 radicals, which may be the same or different, are an alkyl, an aryl or an alkylaryl radical.
Preferably, the R , R and R radicals are alkyl radicals - ;
containing from 1 to 12 carbon atoms, an aryl radical or an -alkylaryl radical where the alkyl substituent contains from 1 ~ ~ -20 to 8 carbon atoms. According to a preferred embodiment of `~
this invention, the phosphorous acid ester or the phosphoric acid ester comprises at least two aryl or alkylaryl radicals.
More preferably, these esters are triphenyl phosphate, tri- `~
cresyl phosphate, trixylyl phosphate, tri(m-ehtylphenyl) ~ -phosphate or diphenyl-decyl-phosphate.
The precise composition of the transesterification products is not yet known. Moreover, the molecular weight of these products may be varied according to the molar ratio of the reactants. Products with a high molecular wei~ght are prepared when the molar ratio is 1. A higher molar proportion of any one of the reactants gives rise to products with a 037~4V
lo~ver molecular weight. In order to avoid the produc-tion of transesterifica-tion products containing residual dihydroxy aromatic compounds, the transesterif`ication reaction is preferably carried out with a molar excess of phosphorous compound. This excess may be high; however, an excess higher than two moles of phosphorous compound per mole o~ dihydroxy aromatic compound is of no advantage, either technically or - economically. -One or more monohydroxy compounds may be formed as a by-product during the transesterification reac-tion. ~or instance, when triphenyl phosphate is used for the transesteri-fication reaction, phenol is formed simultaneously with the transesterification product. In order to shift the reaction equilibrium, it is advantageous to remove the monohydroxy compound as soon as it is formed. This shifting of the equilibrium may be performed by using any known method, for ~-instance by stripping and/or by carrying out the transesteri-Eica-tion reaction under vacuum. Basic compounds, such as alkaline metals, alkaline hydroxides, alkaline phenates or -`
alcoholates and the like are catalysts for the transesterifi- `~
cation reaction. This reaction is carried out at a temperature which generally is of from about 100 to 200C.
The viscosity of Components A is noticeably improved by adding Components B or transesterification products. The amount of Component B added largely depends on -the particular Component A employed, on the particular Component B used and on the desired degree of improvement. However, Component B
generally is used in an amount of between 1 and 50% based on the weight of Component A, more particularly in an amount between 1 and 20% by weight.
The functional fluid compositions of the present in-vention may have their properties further improved by adding -.:-~: .:. . . . . .

~37~
there-to an oily material in which these mix-tures are soluble.
Chlorinated diphenyls are very in-teres-ting oils, more particularly for the manu~acture of hydraulic ~luids having a high flame resistance. The relative proportions of -the oily material and of the functional fluid mixture of Components A
and B may vary within wide limits, depending upon -the particular intended use. For instance, fire resistant hydraulic fluids are prepared by mixing 70 to 95% by weight, of the mixture of `~
components A and B and 30 to 5% by weight of chlorinated bi~
phenyl. Other valuable fluids contain a major propor-tion of oily material and a minor proportion of the mixture of ;
Components A and B.
Other valuable properties can also be imparted to -the functional fluids of the present invention by the op-tional -addition of certain other additives. Typical additives are, for example, foam inhibitors, rust inhibitors and antioxidan-ts.
Such additives generally are employed in quantities of from O `
to 3% based on -the weight of the functional fluids. As an anti~
oxidant, it is preferred to use arylamines and alkylphenols, typically di-tert butyl-phenol or di-tert butyl-cresol. These materials usually are employed in quantities from abput 0.05 to 1% by weight. As rust inhibitors, higher alkyl malonic or succinic acids and alkaline-earth metal su~fonates may be used, generally in quantity up to 1% by weight and preferably in quantity of 0.01 to 0.5% by weight. Silicones, alpha-chloro~
naphthalene and other known foam inhibitors may be added to the ;
functional fluids in an amount of from 0.5 to 2% by weight.
The following examples are present to illustrate the present invention:

7~

;~) Prep~r~Ltioll of thc transe~riPical:ion product.
0.3 mole oL tril~henyl pll~spll~te alld 0.15 mole o~
bisphellol A ~ere added ullder ~gi~ation to a reactor. 0.5 g.
o~ sodium hydl~oxide was then adAed and tlle mixture he~ted under pressure of 10 mm. ~Ig. Phenol distilled o:ef at about 115C. The heating was carried up to ~80C. A viscous, oily product was obtained in substantially quantitative yield. This product had a molecular weight of 1405 and the elemental composition ~vas:
C calculated: 68.3% C found: 67.35%
H calculated: 5.05% H found: 5.72%
P calculated: 8.7% P found: 8.50%
b) Preparation of functional fluids.
Various amounts of -the above transesterificatlon product prepared in (a) above were added to tricresyl phosphates as shotvn in Table I below. The viscosities and viscosity indexes which are given in Table I below clearly show that the viscosity index is increased by adding the 20 transesterification product referred to in the Table as "T.P."
TABLE I

Viscosity Functional fluid Engler Centistokes Centistokes ~Tiscosity - at 50C at 100F at 210F index _______________________________________________________________ TCP (a) 2.44 28.25 3.96 - 44 TCP + 1% T.P. (b) 2.67 32.04 4.48 18 TCP + 3% T.P. 3.04 38.46 5.03 38 TCP + 5% T.P. 3.47 44.46 6.18 ~2 TCP + 10% T.P. 4.89; 66.87 7.56 79 TCP + 30~ T.P. 16.70 263.9 20.19 95 : . _ 7~

'I`he improvement which is noticeable when the amount of transesteri~ication product is as low as about 1%, is particularly noticeable when this amount is about 5%, based on the weigh-t Or tricresyl phosphate as may be seen from ~ -~
Table I above. Large amounts of transesterification product, such as for instance amounts higher than about 25-30%, do not give rise to a further improvement.
The flame resistance of tricresyl phosphate is not altered when the transesterification product is added. For 10 example, practically pure tricresyl phosphate, on one hand, ~; -and tricresyl phosphate containing 5% of transesterification product, on the other hand, have the same spontaneous ignition ;
temperature, i.e., 560C.
Example 2 '~
The method described in Example 1 was repeated for the manufacture o-E various transesterification products. Each of these transesterification products was added to tricresyl phosphate in amount of 5% based on the weight of said phosphate.
The particular transesterification product and the properties resulting from their use are summarized in Table II below.

TABLE II

Viscosity of the mixture Transesterification product (added to TCP) Engler Centi- Centi-Viscosity at 50 C stokesO stokes index at 100 F at 210 F
... : .
Bisphenol A + tricresyl -phosphate 3.47 44.46 6.18 62 Bisphenol A + tri(m-ethyl-phenyl)phosphate 3.16 40.30 5.31 55 --~

30 Bisphenol A + triphenyl phosphite 2.99 38.09 4.75 0 Bisphenol A + tri(nonyl-phenyl)phosphite 2.89 35.66 4.56 - 9 Bisphenol A + diphenyl-octyl-phosphite 2.69 32.74 4.43 0 Hydroquinone + tricresyl phosphate 2.60 31~30 4.31 - 4 ~:

~37~0 Exam~le 3 The transesterification product obtained from bis-phenol-A and triphenyl phosphate was added to various aryl phosphates, in an amount corresponding to 5% of the weight of said phosphates. The particular aryl phosphates and the viscosity index of the resulting functional fluids are summarized in the following Table III.
TABLE III
Functional fluid Viscosity index 10 Tri(m-ethylphenyl)phosphate 108 ~ 5% P.T. 135 - 136 Diphenyl-m-ethylphenyl phosphate 75 " " + 5% P.T. 114 - 115 Diphenyl-cresyl-phosphate 30 15 ~- + 5% P.T. 86 - 87 Phenyl-dioctyl-phosphate 67 ;
l~ + 5% P.T. 91 Example 4 Functional fluids were prepared by adding various transesterification products ~T.P.) to diphenyl-cresyl-phosphate, the amount of T.P. corresponding to 5% of the weight of said phosphate. The particular T.P. added and the viscosity index of each mixture is gi~en in Table IV below.
The viscosity index of diphenyl-cresyl-phosphate is 30.
TABLE IV ~

Transesterification product (addedViscosity index ~ ;
to diphenyl-cresyl-phosphate) of mixture Bis(4-hydroxyphenyl)methane +
tricresyl phosphate 100 30 Hydroquinone + tricresyl phosphate 40 Resorcinol + tricresyl phosphate 46 ::
Pyrocatechol + tricresyl phosphate 52 Example 5 A composition was prepared by mixing 85% (by weight) of ; 35 tri(m-ethylphenyl)phosphate, 5% of the transesterification :- :
.- .- ., ~ . , .. , .... . - , -~ 7~4(3 : ~
product between bis~phenol-A and tricre~yl phosphate and 10%
of chlorinated biphenyl ('~2% o~ chlorine). To this mix-ture was added 5% (by weight of the mixture) of` di-tert-butyl-paracresol and 0.1% of calcium petroleumsulfonate. The resulting composition was a fire resistant hydraulic fluid. `

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Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A functional fluid comprising a mixture of (A) an orthophosphoric acid ester of formula 0 = P ? (OR)3, wherein the R radicals, which may be the same or different, are alkyl radicals having from 1 to 8 carbon atoms, aryl radicals or an alkylaryl radical wherein the alkyl sub-stituent has 1 to 8 carbon atoms;
(B) a transesterification product between a phosphorous acid compound and a dihydroxy aromatic compound, the molar ratio of said acid compound to said dihydroxy aromatic compound being in the range of about 1.1:1 to about 2:1; said phosphorous acid compound being selected from the group consisting of the phosphorous acid ester and phosphoric acid ester wherein R1, R2 and R3 which may be the same or different, are alkyl radicals having 1 to 12 carbon atoms, aryl radicals or alkylaryl radicals wherein the alkyl substituent has from 1 to 8 carbon atoms; said dihydroxy compound being selected from the group consisting of hydroquinone, resorcinol, pyrocatechol,2,2'-bis (4-hydroxyphenyl) propane and bis (4-hydroxyphenyl) methane, said transesterification product being present in an amount ranging from 1 to 50% based on the weight of the orthophosphoric ester which comprises com-ponent (A) of the fluid.

2. The functional fluid of Claim 1 wherein said phosphorous compound is a phosphoric acid ester containing at least two aryl radicals or alkylaryl radicals.

3. The functional fluid of Claim 1 wherein said phosphoric acid ester is selected from the group consisting of triphenyl phosphate, tricresyl phosphate, trixylyl phosphate, tri(m-ethylphenyl) phosphate and diphenyl-decyl-phosphate.

4. The functional fluid of Claim 1 comprising said transesterification product in an amount of 1 to 20% based on the weight of orthophosphoric acid ester.

5. The functional fluid of Claim 1 wherein an oily liquid material is in admixture with said mixture of ortho-phosphoric acid ester and transesterification product, said mixture being soluble in said oily material.

6. The functional fluid of Claim 5 wherein said oily liquid material comprises 30 to 5% by weight of said total mixture.