NO772682L - LIQUID ANTIOXIDANT WITH IMPROVED SOLUBILITY IN LUBRICANT OILS - Google Patents

Description

The present invention relates to new, liquid mixtures for use as antioxidants in mineral oils, synthetic, liquid hydrocarbons and synthetic, liquid esters. The relevant compounds are p-alkylphenyl derivatives of α- and "(3-naphthylamine.

In order for a compound to be used as an anti-oxidation agent in liquid lubricants, it should be miscible with and soluble in such lubricants at normal temperatures, this to facilitate dissolution and save time and energy.

The products according to the present invention are liquids

which can be easily mixed with and dissolved directly in the oil in suitable quantities without the need for heating. - This results in the desired saving of time and energy. Another advantage of such liquid mixtures is, in comparison with crystalline mixtures, that liquids are easier to handle. Thus, liquids can be easily stored and pumped into the final product

in the right quantities. These correct amounts can be determined either by weighing or, more conveniently, volumetrically.

Although not normally necessary, if desired, concentrates of these liquid mixtures can be prepared for addition to the oil and this can be easily achieved as these products are miscible and soluble (even at low temperatures) in all proportions in both liquid hydrocarbons and liquid esters. Thus, 50% solutions are easily prepared by simple mixing at room temperature. The solutions remain homogeneous even at very low temperatures.

Among typical oils that can be protected with the antioxidants according to the present invention, the following can be mentioned:

1. All mineral oils

2. Synthetic hydrocarbon oils produced by polymerisation of 1-olefins, such as hexene-1, octene-1, decene-1, dodecene-1 and isobutene. 3. Liquid, synthetic esters based on one or more organic carboxylic acid esters intended for use at temperatures of 200°C and higher. Examples of such synthetic lubricants are lubricants based on a diester of a dibasic acid and a monohydric alcohol, for example dioctyl sebacate or dinonyl adipate; on a triester of trimethylolpropane and a monobasic acid or a mixture of monobasic acids, for example trimethylolpropane tripelargonate or trimethylolpropane tricaprylate; on a tetraester of penta-erythritol and a basic acid or a mixture of

monobasic acids, for example pentaerythritoltetracaprylan or on complicated esters also based on monobasic acids, dibasic acids and polyhydric alcohols or on mixtures thereof.

The formulas that exemplify the relevant structures

in the present invention are the following:

where R is mixed propylene trimers.

These compounds can be prepared by exposing either α- or β-phenylnaphthylamine to the action of a mixture of propylene trimers and a Friedel-Crafts catalyst, e.g. aluminum chloride, boron trifluoride or the like. The reaction can be carried out at a temperature between normal room temperature and 300°C. It is preferred to carry out the reaction in an inert atmosphere, but this is not necessary. In the method according to the invention, the reaction products contain an alkylating agent which comprises several (ie at least 30) isomers, which are trimers of propene. Typical such compounds have the following structural formulas:

and such.

Although it is possible that not all of the olefins in such a mixture can alkylate phenylnaphthylamine in the manner indicated above, there are however a majority of olefins in such a mixture which can give alkylation products. Evidence that the resulting alkylated phenylnaphthylamines are mixtures of different isomers is given in the detailed description of the drawings below.

The fact that the reaction product is a mixture of isomeric compounds (as opposed to the pure, simple compounds described in the literature) and the asymmetry of the introduced alkyl groups can prevent the crystallization of the product that would occur using a pure, more symmetrical connection.

Figures IA and IB show gas phase chromatograms of the mixed propylene trimers (nonene mixture) used according to the present invention.

Figure 2 shows a liquid chromatogram of a distilled

nony1phenyl-a-Naphthylamine.

Each peak in Figures IA and IB corresponds to a single isomer and the total area under each peak is directly proportional to the amount of the relevant isomer in the mixture.

Figures IA and IB are based on a curve obtained by evaluating a sample in a gas chromatograph (Perkin Eimer 226) with a column (length 90 m and diameter 3 mm) coated with 95% of squalene and 5% of a surfactant ( ATPET-80). The temperature in the column was 75°C. One microliter of the sample was introduced into the injection block of the apparatus which was maintained at 90°C. The following gases were used at the indicated pressures: H2, 83 kPa; air, 33^ kPa; Huh, 276 kPa.

In fig. 2 shows a diagram obtained by evaluating samples in a liquid chromatograph (DuPong 830) with a column ("ZORBAX ODS") of length 25 cm and inner diameter k, 6 mm. The column was packed with a material produced by chemically bonding octadecylsilane groups to particles of "ZORBAX SIL". The bound particles thus obtained were spherical and had a diameter of 6-8 µm.

In all the figures, the curves should be read from the right (where the first peak appeared) to the left (where the last peak formed).

As pointed out above, the alkylated phenylnaphthylamines are produced by reacting an alkene (R) with phenylnaphthylamine and the reaction is catalyzed with a Friedel-Crafts catalyst, for example AlCl or BF^.

If R is a single, single compound, then a single, single alkylated product is obtained. It is equally obvious that a mixture of alkylated products is formed if R is a mixture of compounds.

In the present case, only the first-mentioned isomer can give chemical alkylation of the phenyl-α-naphthylamine and the alkylated product consequently has the following structure:

The fact that this is a single connection forward-

goes by its sharp melting point (j6- 77°C). A mixture of compounds would melt within a wider interval.

Said fact is also proven by the fact that in fig. 3 only a single, very narrow peak occurs..

In contrast, the alkylated product according to the present invention is the result of a reaction of a mixture of alkenes (r) so that the alkylated product is necessarily a mixture of compounds. The chromatograms shown in Figures IA and IB relate to the mixed propylene trimers used in the alkylation of the phenylnaphthylamine according to the present invention. It is clear that there are over 30 main isomers in the mixture. No single isomer makes up even 10% of the total mixture. It is noted that in the example below a double molar excess of the mixed trimer is used because some of the components in the mixture are of a type that do not alkylate the phenylnaphthylamines. Since, as can be seen from an analysis of the reaction product, a significant quantitative yield of monoalkylation product is obtained, it is statistically necessary that more alkylated products are formed. It is undoubtedly true that the main maximum in fig. 2 in reality is a mixture of isomers. Due to the fact that the connections are extremely similar to each other, it has not been possible to achieve good resolution, but a comparison between figures 2 and 3 shows that the width of the main peak in fig. 2 is 2-3 times as large as the height of the main peak in fig. 3, and this shows that in the material according to fig. 2 several isomers occur. Approximately 6 isomeric components occurring in smaller amounts differ sufficiently from the main components to give distinct peaks by the chromatographic method used. This is because the reaction product according to the present invention is a mixture of isomers, that the product is liquid, the statistical fact indicated above and the curve in fig. 3.

In general, 0.05-2, preferably 0.2-2.5 parts of the alkylated phenylnaphthylamines according to the invention are added to 100 parts of the lubricating oil intended for stabilization.

The following examples illustrate the preparation of the compounds according to the invention.

Example 1

109.5 g (0.5 mol) of phenyl-α-naphthylamine and 126 g (1 mol) of mixed propylene trimers were mixed in a three-necked round bottom flask fitted with a stirrer, reflux condenser and thermometer. A static overpressure of nitrogen was maintained via the condenser's upper end. To the above mixture was added 1.5 S AlCl^ and the whole heated to 120°C and this

temperature was maintained for 2k hours. The reaction mixture was then allowed to cool to room temperature and 30 ml of hexane was added. - The solution thus obtained was filtered to remove trace amounts of insoluble catalyst and was then washed with a 5% solution of NaOH (2x300 ml). The hexane solution was washed with water to neutrality. The solution was dried with MgSO 4 , which was then filtered off. The hexane and the propylene trimer excess were distilled off at atmospheric pressure. Finally, a temperature of 250°C was reached in the still and at this point a negative pressure of 20 mm was created to ensure complete removal of the propylene trimer excess. The residue in the flask weighed 165 g. The theoretical yield for complete monoalkylation is 172 grams. The rest consisted of a syrup which did not crystallise, either in the unmixed state or from a hexane solution (10tfo) at -78°C. This residue had the following analysis:

% C ' fo H io N

Calculated for C^<H>^<N:>86.96 8.98 k, 06

Found 87.76 8.89 4.10

As can be seen from the above analysis, the product is essentially monoalkylated phenyl-a-naphthylamine. The above stated residue in the flask can be distilled almost completely between 185 and 188°C at 0.08 mm Hg whereby a pale cherry red liquid is obtained.

Example 2

The procedure described in example 1 was repeated, but with the use of phenyl-P-naphthylamine. A liquid mixture of alkylated phenyl-|3-naphthylamines was obtained.

Example 3

To 100 parts of a liquid, synthetic ester, namely trimethylolpropane triheptanoate, 1.5 parts of the reaction product prepared according to example 1 were added. The mixture thus obtained proved to have excellent antioxidant properties when aged at an elevated temperature.

Example k

2.5 parts of the reaction product prepared according to example 1 were added to 100 parts of mineral oil. The thus obtained mixture also proved to have excellent antioxidant properties in aging tests carried out at an elevated temperature.

Example 5

To 100 parts of a synthetic, liquid hydrocarbon, namely polyoctyltene, 2.0 parts of the reaction product produced according to example 2 were added. The mixture thus obtained proved to have excellent antioxidant properties when aged at an elevated temperature.

Example 6

To 100 parts of liquid, synthetic hydrocarbon, namely polydecene, 2.0 parts of the reaction product produced according to example 1 were added. The mixture thus obtained proved to have excellent antioxidant properties when aged at an elevated temperature.

Example 7

To 100 parts was a mixture of 25 parts polyoctene and

75 parts of trimethylolpropane triheptanoate, 1.7 were added

parts of the reaction product prepared according to example 1.

The mixture thus obtained had excellent antioxidant properties when aged at an elevated temperature.

Example 8

To 100 parts of a mixture of 50 parts polyoctene and

a liquid, synthetic ester, namely trimethylolpropane triheptanoate, 1.7 parts of the reaction product according to example 2 were added. The thus obtained mixture proved to have excellent antioxidant properties when aging was carried out at an elevated temperature.

Claims (15)

1. Liquid mixture effective as an antioxidant in mineral oils, synthetic hydrocarbon lubricants and synthetic ester lubricants, characterized in that it comprises the products obtained by reaction in the presence of a Friedel-Crafts catalyst of phenylnaphthylamine and mixed propylene trimers. 2. Mixture according to claim 1, characterized in that the phenylnaphthylamine is α-phenylnaphthylamine. 3. Mixture according to claim 1, characterized in that the atphenylnaphthylamine is p-phenylnaphthylamine. 4. Mixture according to claim 1, characterized in that the propylene trimers comprise several isomers. 5. Mixture according to claim 1, characterized in that the propylene trimers consist of at least 30 isomers. 6. Mixture according to claim 1, characterized in that the reaction products contain several isomers. 7. Mixture according to claim 1, characterized in that the Fiedel-Crafts catalyst is aluminum chloride. 8. Mixture according to claim 1, characterized in that the Friedel-Crafts catalyst is boron trifluoride. 9. Mixture according to claim 1, characterized in that 0.05-4 parts thereof are mixed into 100 parts of a liquid, synthetic ester lubricant. 10. Mixture according to claim 9, characterized in that the liquid, synthetic ester lubricant is trimethylolpropane triheptanoate. 11. Mixture according to claim 1, characterized by . that it is mixed with a liquid mineral lubricating oil in an amount of 0.05-4 parts of said liquid mixture per 100 parts of said liquid lubricant. 12. Mixture according to claim 1, characterized in that it is mixed with a liquid synthetic hydrocarbon lubricant, whereby the amount of mixture is between 0.05 and 4 parts per 100 parts of the liquid lubricant. 13. Mixture according to claim 12, characterized in that the liquid, synthetic hydrocarbon lubricant is polyoctene. 14. Mixture according to claim 12, characterized in that the liquid, synthetic hydrocarbon lubricant is polydecene. 15. Mixture according to claim 1, characterized in that it is mixed with a liquid lubricant containing between approx. 25 and approx. 50 parts polyoctene and between approx. 50 and 75 parts trimethylolpropane triheptanoate, whereby said mixture is included with 0.05-4 parts per 100 parts of said liquid lubricant.