DE69835694T2 - USE OF BIODEGRADABLE ACETIC ESTOLIDE ESTER AS BASE OIL AND LUBRICATING OIL - Google Patents

Abstract

Esters of estolides derived from oleic acids are characterized by superior properties for use as lubricant base stocks. These estolides may also be used as lubricants without the need for fortifying additives normally required to improve the lubricating properties of base stocks.

Description

Background of the invention

Field of the invention

These This invention relates to esters of oleic acid estolides and their use as biodegradable masterbatches and Lubricant.

description of the prior art

synthetic Esters such as polyol ester and adipate, poly-alpha olefins (PAO) with low viscosity, like PAO 2, vegetable oils, especially canola oil and Oleate, are industrially used as biodegradable masterbatches used to formulate lubricant. Contain lubricant usually 80-100 wt .-% base mix and 0-20 wt .-% additives to their viscometric properties, their behavior at low temperatures, their oxidation resistance, their corrosion protection, their demulsibility and water repellency, their friction coefficients, their lubricity, their protection Wear, their air release, their color and other properties tailor. Biodegradability can not be achieved by using additives be improved.

in the The state of the art lately has become estolides due to their potential for base mixes and lubricants paid much attention. An Estolid is one unique oligomeric fatty acid, the secondary Ester bonds on the alkyl backbone of the molecule includes.

US-A-4 No. 867,965 describes a diester derived from a fatty acid such as oleic acid. Of the Diester in US-A-2 652 411 describes a compound based on a Ester backbone is based on 18 carbon atoms, where one located near the middle of the chain C atom is substituted with an ester group.

estolides were typically synthesized by the homopolymerization of castor oil fatty acids [Modak et al., JAOCS 42: 428 (1965); Neissner et al., Fette Soifen Anstrichm 82: 183 (1980)] or 12-hydroxystearic acid [Raynor et al., J. Chromatogr. 505: 179 (1990); Delafield et al., J. Bacteriol. 90: 1455 (1965) below thermally or acid-catalyzed Conditions. Yamaguchi et al., [Japanese Patent 213,387, (1990)] described recently a process for the enzymatic preparation of estolides from hydroxy fatty acids (in particular Ricinoleic) in castor oil occur, using lipase.

Out Estolides derived from these sources consist of esters on the 12th carbon atom of fatty acids and have a residual hydroxy group on the estolide backbone. Furthermore, that is Extent of Unsatisfaction with the produced estolides (expressed, for example, by the iodine value) not significantly lower than in the starting materials, d. H. Hydroxy fatty acids.

Erhan et al. [JAOCS, 70: 461 (1993)] reported the production of Estolides of unsaturated fatty acids below Use of condensation at high temperatures and high pressure over clay catalysts. The transformation of the fatty acid double bond in an ester function is a completely different method than the hydroxy esterification method.

Summary the invention

We have now discovered a family of novel estolide compounds, derived from oleic acids, and superior to their characteristics Properties for the use as a lubricant base mixtures include. These Estolides can also be used as a lubricant without it being reinforcing Additives that are normally needed to lubricants properties to improve the basic mixes.

wobei x und y jeweils 1 oder größer als 1 sind;
wobei x + y = 10;
wobei n 1 oder größer als 1 ist;
wobei R CHR₁R₂ ist;
wobei R₁ und R₂ unabhängig ausgewählt sind aus Wasserstoff und C1- bis C36-Kohlenwasserstoff, der gesättigt oder ungesättigt, verzweigt oder geradkettig, und substituiert oder unsubstituiert sein kann;
wobei R₃ ein Restfragment einer Ölsäure-, Stearinsäure- oder anderen Fettsäurekette ist; und wobei sich die vorherrschende Sekundäresterverbindungsspezies an der Position 9 oder 10 befindet; d. h., wobei x = 5 oder 6 bzw. y = 5 oder 4 ist.The estolol esters of this invention are generally represented by formula (I):

where x and y are each 1 or greater than 1;
where x + y = 10;
wherein n is 1 or greater than 1;
wherein R is CHR ₁ R ₂ ;
wherein R ₁ and R _{2 are} independently selected from hydrogen and C 1 to C 36 hydrocarbon which may be saturated or unsaturated, branched or straight chain, and substituted or unsubstituted;
wherein R _{3 is} a residual fragment of an oleic, stearic or other fatty acid chain; and wherein the predominant secondary ester compound species is at position 9 or 10; ie, where x = 5 or 6 or y = 5 or 4.

According to this Discovery It is an object of this invention to provide novel estolide compounds provide as base lubricant mixtures and also useful as a lubricant without the inclusion of conventional additives.

One Another purpose of this invention is to provide a family of To provide estolides that are biodegradable and superior Oxidationsbeständigkeits-, Have low temperature and viscometric properties.

Other Objects and advantages of this invention will become apparent from the following description be easily apparent.

Detailed description

For the purpose of this invention, the term "monoestolide" is used generically, around the acid form to designate compounds having the structure of formula I, where n = 0. The term "polyestolide" is used herein around the acid form to designate compounds having the structure of formula I, where n is greater than 1 is. The terms "ester", "estolidester" and the like are commonly used herein to refer to products which by the esterification of the fatty acid residue (Attachment of R group in formula I) on the estolide or the estolide mixtures as described below getting produced. Of course Estolide esters are derived from secondary ester bonds between fatty acid chains and this is the greatest effort used, the actual To distinguish estolide from its ester.

The preparation of monoestolides and polyestolides in various ways is fully described in Isbell et al. (I) [JAOCS, Vol. 71, No. 1, pp. 169-174 (February 1994)], Erhan et al. [JAOCS, Vol. 74, No. 3, pp. 249-254 (1997)] and Isbell et al. (II) [JAOCS, Vol. 74, No. 4, pp. 473-476 (1997)], which are incorporated herein by reference. Although not necessary, it is preferred for quality control purposes that the starting material be as pure as practically possible with respect to oleic acid. Isbell et al. (III) [YES OCS, Vol. 71, No. 1, pp. 379-383 (April, 1994)] characterize the acid catalysis oleic acid stolids as mixtures of monoestolides and polyestolide oligomers of up to eight or more fatty acid molecules formed by secondary ester linkages the alkyl backbone esterified with each other. This publication also teaches that the positions of these secondary ester bonds are centered around the original C-9 double bond position, where bonds actually range from positions C-5 through C-13, and most often at positions C-9 and C-10 in FIG about equal amounts occur. Likewise, the remaining unsaturated character on the end fatty acid was distributed along the backbone of the fatty acid, presumably also from C-5 to C-13.

The Bonds of the estolides of this invention would be the same or about the same Have distribution of bonds as described by Isbell et al. Reported in 1994. Therefore, it should be understood that Formula I, above, is a generalization the estolide-backbone structure the compound considered herein is that the formula is normal It should include distributions of reaction products made up of to the various reaction techniques referred to above was taken. The notifying parties assume that the outstanding Properties of the representational Estolid esters are not so much affected by the positions of the bond and the Site of the unsaturated Characteristics are determined, but rather by the combination the degree of oligomerization, reducing the size of the unsaturated Characteristic of the lack of hydroxy functionalities on the estolid backbone and the nature of the specific ester moiety (R). However, that leads Method inherent a distribution of secondary Bonding positions in the estolid generally indicate the behavior at low temperatures and the viscometric behavior very favorably influenced. Other minor constituents other than oleic acid, such as linoleic acid or stearic acid, can also lead to variations of the basic estolide structure shown in formula I. is.

The oleic acid-estolides for the Use in the preparation of the esters of this invention may be achieved by a any conventional Procedure to be won. Typically, the overweight a low-boiling monomer fraction (unsaturated fatty acids and saturated fatty acids) and also of dimer acids, that can form away. In a preferred embodiment, the reaction conditions so selected be that no or essentially no dimer acids in the Course of the reaction arise, with only estolides are formed and the residual fraction comprises substantially pure estolides.

The oleic acid estolides are esterified by standard procedures, such as acid catalyzed reduction with a suitable alcohol. In the preferred embodiment of the invention, R ₁ and R _{2 are} not both hydrogen, and more preferably neither R ₁ nor R _{2 is} hydrogen. That is, it is preferable that the reacting alcohol is branched. In the most preferred embodiment of the invention, the oleic acid esters are selected from the group consisting of isopropyl ester, 2-ethylhexyl ester and isostearyl ester. The average value of n in formula I is greater than 1.0.

in the Within the scope of the invention, especially those esters are eye-catching characterized by: a viscosity at 40 ° C of at least 20 cSt and preferably at least about 32 cSt; a viscosity at 100 ° C of at least 5 cSt and preferably at least about 8 cSt; a viscosity index of at least 150; a pour point less than -21 ° C, and more preferably at least -30 ° C; a volatility less than 10% at 175 ° C; a negligible (<10 %) Oxypolymerization in 30 min. At 150 ° C in the micro-oxidation test [Cvitkovic et al., ASLE Trans. 22: 395 (1979); Asadauskas, PhD Thesis, Pennsylvania State Univ. P. 88 (1997)] and biodegradability in the OECD test of more than 70%. The determination of these properties by conventional Testing is routine. Therefore, the identification of oleic acid esters would be Estolidestern in the scope of formula I completely within the capabilities one of ordinary skill in the art.

As previously indicated and shown in the examples below, have the oleic acid esters superior to this invention Properties that they use as masterbatches for biodegradable lubricant applications useful like crankcase oils, hydraulic fluids, drilling fluids Two-stroke engine oils and the same. Certain of these esters are sufficient or superior many, if not all, requirements for some lubricant consumer applications without the inclusion of conventional additives.

If They can be used as a basic mixture, the figurative Ester with an effective amount of other lubricants such as mineral or vegetable oils, other estolides, poly-alpha olefins, polyol esters, oleates, diesters and other natural ones or synthetic fluids be mixed.

In the manufacture of lubricants, any of a variety of conventional ones can be used Lubricant additives are optionally incorporated into the masterbatch in an effective amount. Exemplary additives are detergents, antiwear agents, antioxidants, viscosity index improvers, pour point depressants, corrosion inhibitors, friction coefficient modifiers, colorants, anti-foaming agents, demulsifiers, and the like.

Of the Expression "effective Amount "is how used herein as being defined to mean any amount, the one for measurable effect for the intended purpose. For example, one is effective amount of a wear-resistant substance, used in a lubricant composition, a lot, the wear in a machine compared to a control composition, the the agent does not encompass a measurable amount.

example 1

Preparation of 2-ethylhexyl-oleic acid solid (Laboratory).

To 1,000 ml of commercial grade oleic acid (70% oleic acid) in a 3,000 ml 3-neck flask evacuated to 27 inches (686 mm) of mercury, 50 ml of sulfuric acid are added over 4 min. The temperature was maintained at 55 ° C for 24 hours and the stirring rate at 300 rpm. After the vacuum was released with nitrogen, 373 ml (2.39 mol, 1.1 molar equivalents) of 2-ethylhexyl alcohol was added to the flask over 5 min, and then the vacuum was restored. After mixing for 2 hours at 55 ° C, 190 g of Na ₂ HPO ₄ in 2 L of water was added with thorough stirring. The mixture was allowed to stand overnight and the water layer was removed. The product was recovered by removal of the alcohol using vacuum distillation at 13.3 to 66.7 Pa (0.1-0.5) Torr at 100 ° C.

in the Course of three passes The overall yield of the product ranged from 82 to 84%, and the average Value of n in formula I was 1.2.

Example 2 (Comparative)

Preparation of 2-ethylhexyl-oleic acid solid (Preliminary experiment).

A production of 2-ethylhexyl-oleic acid solid was carried out on a pilot scale as follows:
Two hundred and fifty pounds (113 kg) of oleic acid (commercial grade) was placed in a plastic-coated drum and degassed with a 15 minute nitrogen fumigation. 23 pounds (10 kg) of concentrated sulfuric acid were added slowly with stirring, keeping the temperature below 55 ° C by the rate of addition. The drum temperature was maintained after the complete addition of the sulfuric acid by storage in a room heated to 55 ° C. After 24 hours, a sample of forty-one pounds (18 kg) was taken and the acid and iodine values checked. Sixty-eight pounds (31 kg) of 2-ethylhexanol were then added, and after 2 hours, it was confirmed that the hydroxyl value was less than 10.0, indicating the completeness of the reaction. The reaction mixture was washed by the addition of a 10% solution of potassium hydrogen phosphate [50 lbs (23 kg) K ₂ HPO ₄ in 500 lbs (227 kg) city water]. After 1 hour separation by settling, it was checked that the pH in both layers was 5-6 and the water layer was decanted off. After separation, the estolidester was transferred to a kettle and dried at 105 ° C and 29 inches of mercury to remove excess water and excess 2-ethylhexanol. The vacuum drying was followed by pressure filtration using 0.5% filter aid. The value of n in formula I was 0.5.

Example 3

Characterization of the physical properties of the 2-ethylhexyl-oleic acid solid of Example 2.

The Biodegradability becomes common tested using the Modified Storm Test, where the percentage Degradation is measured in 28 days (OECD 301 B). The biodegradability of the principal Base mixtures are listed in Table I with that of non-esterified oleic acid stolid compared. It is expected that the 2-ethylhexyl esters of oleic acid solid will not significantly other biodegradable than the non-esterified Estolides.

The viscometric properties determine the lubricating properties of the lubricants, their film strength, and their ability to maintain a lubricating film under varying temperatures. In the In the lubricants industry, these properties are measured by measuring kinematic viscosities using Cannon-Fenske viscometers and then assigned grades of viscosity. The most prominent grades are ISO 32 and ISO 46. The major viscometric properties of the main masterbatches industrially used to make biodegradable lubricants are compared in Table II to 2-ethylhexyl (2EH) ester of oleic acid solid.

Of the Advantage of the Estolides is its high viscosity index (VI) and degree of viscosity after ISO 46. This is similar to the viscometric properties of oleates and vegetable oils. This Estolid would not Need thickeners, the for Tridecyl adipate or PAO 2 are necessary. The presence of on Polymer-based thickeners or viscosity modifiers can cause shear stability problems in formulated lubricants cause.

Low temperature properties are for the pumpability, filterability, flowability of a lubricant as important as for cold cranking and starting. The pour point is the most common Indicator of the Low-temperature behavior. Masterbatches derived from vegetable oils are, can normally remain liquid for no more than 1 day during the cold storage test; therefore, in addition to the pour point the cold storage test developed by ASTM D02 to the suitability of lubricants. The ultimate low-temperature properties are compared in Table III. Estolid has much better Low temperature properties as trioleates, vegetable oils or Polyolester with higher Viscosities.

The volatility is very important for the vapor pressure, the flammability, the volatile burning and the Emissions of lubricants. The volatility affects the flash point, measured using the Cleveland Open Cup test method becomes. Micro oxidation data allow it, the volatility at certain temperatures, in this case 150 ° C (same range as at a hydraulic system or crankcase). The Key volatility properties are compared in Table IV. The estolides are much less volatile as low viscosity PAOs or adipates.

The oxidation resistance defines the durability of a lubricant and its ability to to maintain its functional properties during its use. On vegetable oils and oleate-based lubricants usually suffer from a low Oxidation resistance. Micro-oxidation is a technique in the lubricant industry recognized the oxidation resistance by classifying tendencies towards oxypolymerization. Micro-oxidation data are compared in Table V.

The oxidation resistance of Estolid is comparable to that of fully saturated materials such as PAOs, Polyol esters and adipates. Vegetable oils and most liquids, those who won them are clearly inferior to the Estolids.

in the In general, the 2-ethylhexyl Estolidester has with respect to its oxidation resistance and its low temperature properties over vegetable oils and Oleaten, and re his volatility, its viscometric properties and its biodegradability Advantages over PAOs with low viscosities and adipates.

Example 4

The Methyl, butyl, decyl, oleyl, isopropyl, isostearyl and branched C24 esters of oleic acid solid essentially as described in Example 1 for the 2-ethylhexyl ester produced. These esters were measured for melting point, viscosity index and the viscosity each at 100 ° F (38 ° C), 40 ° C and 100 ° C in the Comparison with known vegetable oils, fatty acids and other estolides and vegetable oil derivatives. The Results are shown in Table VI.

Example 5

Tabelle II

Tabelle III

Tabelle IV

Tabelle V

Tabelle VII

The pour points of 12-hydroxystearin (Guerbet) acid esters and 2-ethylhexyl esters of ricinoleic acid stolid and oleic acid solid were compared (Table VII). Table I

Table II

Table III

Table IV

Table V

Table VII

Claims (11)

Estolide compound having the formula:

where x and y are each 1 or greater than 1; where x + y = 10; wherein n is 1 or greater than 1; wherein R is CHR ₁ R ₂ ; wherein R ₁ and R _{2 are} independently selected from hydrogen and C 1 to C 36 hydrocarbon which may be saturated or unsaturated, branched or straight chain, and substituted or unsubstituted; wherein R _{3 is} a residual fragment of an oleic, stearic or other fatty acid chain; and wherein the predominant secondary ester compound species is at position 9 or 10; ie, where x = 5 or 6 or y = 5 or 4. The estolide compound of claim 1, wherein at least one of R ₁ and R _{2 is} a C 1 to C 36 hydrocarbon. The estolide compound of claim 1, wherein both R ₁ and R _{2 are} C 1 to C 36 hydrocarbons. An estolide compound according to claim 1, wherein R is methyl is. An estolide compound according to claim 1, wherein R is butyl is. An estolide compound according to claim 1, wherein R is isopropyl is. An estolide compound according to claim 1, wherein R 2 is ethylhexyl is. An estolide compound according to claim 1, wherein R is isostearyl is. A lubricant composition comprising (1): an estolide compound of the formula:

where x and y are each 1 or greater than 1; where x + y = 10; wherein n is 1 or greater than 1; wherein R is CHR ₁ R ₂ ; wherein R ₁ and R _{2 are} independently selected from hydrogen and C 1 to C 36 hydrocarbons, which may be saturated or unsaturated, branched or straight chained, and substituted or unsubstituted; wherein R _{3 is} a residual fragment of an oleic, stearic or other fatty acid chain; and wherein the predominant secondary ester compound species is at position 9 or 10; ie where x = 5 or 6 or y = 5 or 4; and (2) an effective amount of a lubricant. A lubricant composition according to claim 9, wherein the lubricant is selected from the group consisting of mineral oil, vegetable oil, estolide, which is different from that defined by formula I, Poly-alpha-olefin, polyol ester, oleate and diester. A lubricant composition according to claim 9, and further comprising an effective amount of a lubricant additive, the selected is from the group consisting of cleaning agent, wear protection material, Antioxidant, viscosity index improver, pour point depressants, Corrosion inhibitors, friction coefficient modifiers, dye, Antifoam and demulsifiers.