CA2098109A1

CA2098109A1 - Non-volatile solvent for aroma-containing active ingredients

Info

Publication number: CA2098109A1
Application number: CA002098109A
Authority: CA
Inventors: Karl Schmid; Josef Steber; Reinhold Wuest; Peter Gode
Original assignee: Individual
Current assignee: Henkel AG and Co KGaA
Priority date: 1989-12-09
Filing date: 1990-12-03
Publication date: 1991-06-10
Also published as: JPH05502262A; WO1991009096A2; EP0505484A1; DE3940803A1; WO1991009096A3

Abstract

Selected, benzoic acid diesters of straight-chain and/or branched aliphatic diols with at least 4 carbon atoms, which are free-flowing at ambient temperature, are used as non-volatile, non-polluting solvents for active ingredients such as oxidation and/or corrosion inhibitors with at least a partially aromatic molecular structure when the latter are used in environmentally safe fats and/or oils, in particular hydraulic oils based on diester oils.

Description

~ W0 91/09096 ~C.......... ~ PCT/EPgo/02083 :
A low-volatility solvent for active sub~tance~ containing ~romatic constituents :
; This invention relates to an improvement in the use of oils, for example as hydraulic fluids for hydrostatic power .. , transmission.
In applications where the escape of oil into the environment has to be counted as a possibility, for example j through unavoidable leakages, there is now an increasing ; demand for the use of hydraulic oils which contain environ--, ment-friendly ester oils, particularly those based on ~; rapeseed oil and/or soybean oil, as the oil base. Typical applications of the kind in question are the machines and tools used in forestry and agriculture, excavators and the like. The use of hydraulic oils having a water hazard classification of 0 is required for such applications. In contrast to the mineral-oil-based hydraulic oils used in the past, corresponding ester-based oils are capable of meeting pollution control requirements.
However, ester oils suitable for use in practice, for example deslimed rapeseed oils and/or soybean oils, have the following weaknesses in relation to mineral oils:
The ester oils based on unsaturated fatty acid systems tend to thicken rapidly, even at only moderately elevated operating temperatures of, for example, 50 to 80-C. The reason for this lies in the readiness of the olefinic double bonds of the ester-forming acids of the oil type in question here to enter under the effect of atmospheric oxygen into reactions which ultimately leads to an increase in viscosity. It is known in principle that, in hydraulic , oils, such unwanted increases in viscosity can be prevented to a certain extent by addition of antioxidants, although it is difficult in their case to establish a satisfactory performance level, particularly over prolonged periods. In ~ .
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- WO 91/09096 2 PCT/~P90/02083 many cases, more antioxidant, corrosion inhibitors and the like have to be added after a certain time to ensure a sufficiently long operating life for ester oils of the type in question here.
The necessary auxiliaries from the classes of anti-oxidants, corrosion inhibitors and the like are frequently, if not generally, compounds which at least partly contain aromatic constituents. More particularly, phenolic struc-tures and/or hydroquinone derivatives are predominant in the class of relevant auxiliaries or active substances against the unwanted attack of atmospheric oxygen. For ~; example, applicants' earlier patent application P 39 27 155.2 (D 8826 "Environment-friendly base oil for the ; formulation of hydraulic oils") describes a corresponding natural base oil for the formulation of hydraulic oils having improved viscosity and/or low-temperature stability , in use which contains the following components:
a) purified rapeseed oil and/or soybean oil as principal , ,.
oil component, i b) 0.5 to 5% by weight, based on the mixture as a whole, of antioxidants selected from the group consisting of methoxyphenol, ethoxypllenol, butyl hydroxyanisole, butyl hydroxytoluene, methoxy hydroquinone, ethoxy , 25 hydroquinone, tert. butyl hydroquinone and/or toco-pherol and, optionally, c) esters of trimethylol ethane, trimethylol propane and/or neopentyl glycol with monocarboxylic acids belonging to the following sub-classes:
cl) saturated C510 monocarboxylic acids and/or c2) fatty acids based on rapeseed oil, soybean oil and/or technical oleic acid, "' the ester components c) being present in substantially the :

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WO 91/09096 ~ C ~ PCT/EP90/02083 same quantity as the principal oil component a).
Only antioxidants based on aromatic molecular con-stituents are used as component (b). For the practical application of environment-friendly base oils such as these, it has been found to be desirable additionally to make available active-substance concentrates in which the stabilizing additives are dissolved, preferably in high concentrations. The useful life of the hydraulic oil can i be effectively prolonged by the subsequent introduction of these active-substance concentrates. However, there is a certain problem here in the choice of the solvent. Active-substance concentrates of the described type require a low-volatility solvent which flows at ambient temperature and which is highly compatible with the aromatic basic struc-ture of the active substances used to ensure the necessary high concentrations of the dissolved active substances. A
partial aromatic basic structure of the solvent would also satisfy this requirement. Starting out from these basic considerations, dibutyl phthalate (DBP) which is now widely used would be a suitable representative as solvent for the production of the active-substance concentrates required.
Recently, however, certain ecological and toxicological objections to the uncontrolled use of DBP have appeared in the literature. This is the starting point of the present invention.
The problem addressed by the invention was to provide auxiliaries of the type mentioned at the beginning, which ; would have an at least partly aromatic molecular structure and which would also be characterized by high environmental compatibility, for the operation of environment-friendly oil phases of the type known, for example, as ester oils from applicants' earlier patent application cited above.
More particularly, the invention set out to make antioxi-`~ dants and/or corrosion inhibitors of the described type ~ 35 available in the form of dissolved concentrates in a :., ~'' .

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i~C~`'`3~0'3 , Wo gl/09096 4 PCT/EP90/02083 solvent which itself had a water hazard classification of 0 and, at the same time, to enable highly concentrated solutions flowable at ambient temperature to be produced :: and safely incorporated in the ester-based hydraulic oils without particular effort.
3 The technical solution to the problem addressed by the invention lies in the use of selected benzoic acid diesters as a low-volatility solvent of high environmental compat-ibility.
Accordingly, the present invention relates to the use of selected benzoic acid diesters of linear and/or branch-~ ed aliphatic diols containing at lest 4 carbon atoms, which flow at ambient temperature, as a low-volatility environ-ment-friendly solvent for active substances, such as anti-. 15 oxidants and/or corrosion inhibitors, having an at leastly ; partly aromatic molecular structure where they are used in .: fats and/or oils of high environmental compatibility, :' particularly in ester-based hydraulic oils.
' In another embodiment, the present invention relatesto an additive which is based on a low-volatility solvent flowable at ambient temperature and which contains active . substances, such as antioxidants and/or corrosion inhibi-:~ tors, having an at least partly aromatic basic structure, .. characterized in that benzoic acid diesters of linear ~ 25 and/or branched aliphatic diols containing at least 4 ;, carbon atoms, which flow at ambient temperature, are ~'. present as the solvent.
Preferred low-volatility solvents according to the . invention are benzoic acid/diol diesters which have pour 30 points below O-C and preferably below -lO-C and, at the .~ same time, flash points no lower than 150-C and preferably above 200-C. Benzoic acid diesters having this property profile are derived in particular from diols containing 4 to 9 carbon atoms and, more particularly, 5 to 7 carbon 35 atoms linearly arranged between the hydroxyl groups of the : ' j , . . .
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C~ 0'3 WO 91/09096 5 P~T/EP90/02083 diol or diol component o~ the ester. This linear inter-mediate member of the diols may be unsubstituted or even branched one or more times by substitution with lower alkyl groups preferably containing up to at most 3 carbon atoms.
Benzoic acid diesters of diols containing at most 10 carbon atoms in the diol component are particularly suitable.
Benzoic acid diesters of the described type satisfy the requirement profile mentioned at the beginning in the sum total of their properties. By virtue of their aromatic molecular components, esters of this type are capable of accommodating large quantities of the aromatic active substances to be dissolved in the additive. Thus, active substance contents of generally 5 to about 50% by weight and preferably up to about 40% by weight can be established in the selected solvent. The benzoic acid esters them-selves are environment-friendly and, in particular, have a water hazard classification of 0. They may readily be introduced into and homogeneously incorporated in hydraulic oils, for example based on the described ester oils.
Preferred active substances for introduction via the additives according to the invention are antioxidants selected from the group consisting of methoxyphenol, ethoxyphenol, butyl hydroxyanisole, butyl hydroxytoluene, - methoxy hydroquinone, ethoxy hydroquinone, tert. butyl hydroquinone and/or tocopherol. Other typical active substances may also be added to the additive concentrates.
Examples of these other additives are high-pressure addi-tives, anti-wear additives and/or pour point depressants.
Further particulars of the composition of hydraulic oils can be found in the relevant prior art literature, cf. in particular "Ullmanns Enzyklopadie der technischen Chemie", 4th Edition (Verlag Chemie, Weinheim), Vol. 13, pages 85 et seq., Hydraulikflussigkeiten (Hydraulic Fluids) and Dieter Xlamann "Schmierstoffe und verwandte ProduXte, Nerstellung, Eigenschaften, Anwendung (Lubricants and Related Products, ;~C'`~5~!3 Wo 91/09096 6 PCT/~P90/02083 i Production, Properties and Applications)", (Verlag Chemie, Weinheim) 1982, pages 147/148 - 11.9, Hydraulikole (Hydrau-lic Oils).
In one particular embodiment of the invention, the S benzoic acid diesters are used in admixture with poly-a-olefins as the solvent phase. In the present context, ; poly-a-olefins are oligomers of ~-olefins of medium chain length. Oligomers which meet the flow requirements of the benzoic acid diol diesters are particularly suitable.
Oligomers of ~-olefins containing 6 to 12 carbon atoms in the monomeric molecule are preferred, oligomers of the Cl0 ~-olefin being particularly preferred. The oligomers in turn may be formed, for example, from 2 to 6 units of the ~-olefin. The benzoic acid diesters may be mixed with the poly-~-olefins in a wide range of ratios so that quantita-tive ratios of the two components to one another in the range from about 95:5 to 5:95 and preferably in the range ~! from about 70:30 to 30:70 are suitable.

20B x a m p 1 e Bxample 1 856 g pentane-1,5-diol were esterified with 1832 g benzoic acid for 7 hours at 200-C in the presence of 0.1%
tin oxide. A colorless clear oil having the following characte~istic data was obtained: acid value 0.3, hydroxyl value 29, saponification value 350. This oil had a flash point according to DIN ISO 2592 of 224-C, a pour point according to DIN ISO 3016 of -33-C and a cloud point 30according to DIN ISO 3015 of -12-C.
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Comparison Examplo 1 159 g neopentyl glycol, 136 g trimethylol propane and 366 g benzoic acid were reacted as in Example 1 to form an ester. A colorless oil was obtained and crystallized after , :

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Comparison Ex~mple 2 183 g benzoic acid and 76 g propane-1,2-diol were reacted as in Example 1 to form an ester. A crystalline product was obtained.

Example 2 30 g butyl hydroxyanisole were dissolved in 70 g of the ester of Example 1 at 60C. The mixture remained liquid for more than 3 weeks at -10C.
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; Comparison Example 3 342 g trimellitic anhydride, 323 g octanol and 485 g decanol were reacted as in Example 1 to form an ester. A
colorless oil having the following characteristic data was obtained: acid value 0.5, hydroxyl value 2, saponification value 285. This oil had a pour point according to DIN ISO
3016 of -42-C and a flash point according to DIN ISO 2592 of 280-C.
As in Example 2, 30 g butyl hydroxyanisole were dissolved in 70 g of the ester of Comparison Example 3 at 60'C. On cooling to room temperature, the butyl hydroxy-anisole crystallized out from the mixture.
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Claims

WO 91/09096 8 PCT/EP90/02083

1. The use of selected benzoic acid diesters of linear and/or branched aliphatic C4 diols, which flow at ambient temperature, as a low-volatility environment-friendly solvent for active substances, such as antioxidants and/or corrosion inhibitors, having an at leastly partly aromatic molecular structure where they are used in fats and/or oils of high environmental compatibility, particularly in ester-based hydraulic oils.

2. The use claimed in claim l, characterized in that the benzoic acid/diol diesters used have pour points below 0°C
and preferably below -10°C and flash points of not less than 150°C and preferably above 200°C and contain prefer-ably 4 to 9 carbon atoms and, more preferably, 5 to 7 carbon atoms linearly arranged between the hydroxyl groups of the esterified diols, this linear intermediate member optionally being substituted one or more times by lower alkyl groups preferably containing up to 3 carbon atoms.

3. The use claimed in claims 1 and 2, characterized in that the benzoic acid diesters are used for the production of highly concentrated active-substance solutions which have active-substance contents of preferably about 5 to 40%
by weight.

4. The use claimed in claims 1 to 3, characterized in that benzoic acid diesters of diols containing at most 10 carbon atoms are used as the solvent.

5. The use claimed in claims 1 to 4, characterized in that the benzoic acid diesters are used in admixture with poly-.alpha.-olefins in a ratio of 95:5 to 5:95.