Liquid octylated phenyl-a-naphthylamine composition

Abstract

LIQUID OCTYLATED PHENYL-α-NAPHTHYLAMINE COMPOSITION A liquid blend of octylated phenyl-α-naphthylamine, and at least one low molecular weight aromatic ester, wherein the octylated phenyl-α-naphthylamine is present from about 15% to about 35% by weight of the blend, as well as a lubricating composition comprising a lubricant base and an amount of the blend which provides up to 2.0% by weight of the octylated phenyl-αnaphthylamine in the composition.

Description

BACKGROUND OF THE INVENTIONField of the InventionThe invention relates to an antioxidant additive for lubricants, more particularly (1,1,3,3-tetramethylbutyl)-N-phenyl-1-naphthylamine (chemical abstract service number 68259-36-9), oralkylated phenyl-α-naphthylamine (APANA), preferably octylated N-phenyl-α-naphthylamine.The APANA is blended with a liquid aromatic ester to provide a stable, liquid form of APANAthat provides improved handling qualities. The invention also relates to a lubricant compositioncomprising a lubricant base and the blend of APANA and aromatic ester.APANA is a highly effective antioxidant with applications in a wide range of lubricants includingaviation turbine oils, gas turbine oils, compressor oils, hydraulic fluids and engine oils. Examplesdescribing the use of octylated phenyl-α-naphthylamine in lubricants are wide spread, and can befound in US patents 5726135, 6326336, 8227391, 9783759, US patent applications 2010 / 0099589,2013 / 0252863, 2014 / 0045736, 2016 / 0083671 and UK patent 2384245. Its use, however, has beenlimited because of difficulty that lubricant blending facilities have in handling the product. Themain issue is that APANA must be handled as a powder. This creates a number of complications,the most important of which are the increased cost associated with handling a solid and workerhealth risks caused by dust exposure from the solid. Melting the solid is not practical due to itshigh melting point. Therefore, there is a need in the industry to provide APANA in a liquid formfor improved handling.Discussion of the Prior ArtOctylated N-phenyl-α-naphthylamine may be prepared in a number of different ways. Examplesof its preparation can be found in UK patent 1046353, US patent 3414618, and US patentapplication 2011 / 0124538 A1. These methods of preparation all involve isolating the product as asolid.Numerous attempts have been made to dilute APANA as a fluid that could allow delivery of thesolid product in a liquid form. This would eliminate the exposure of certain workers to the solidand reduce manufacturing costs in blending facilities. Attempts have been made to dissolveAPANA in mineral oils, poly-α-olefins, polyols and polyol esters with no success. Typically, lessthan 1% APANA can be dissolved in these common base fluids. This is not a practical level forapplying the additive to an additive package, additive package concentrate or finished fluid. Apractical level would be 15 wt. % or more of the APANA in a suitable solubilizing fluid. Thus far,such a suitable fluid has not been identified.SUMMARY OF THE INVENTIONIt has been found that APANA, preferably octylated N-phenyl-α-naphthylamine, can besolubilized, quite effectively, in low molecular weight aromatic esters (150-350 MW) at levels ashigh as about 35%, and that the compositions are stable with no signs of solid fall out orcrystallization on prolonged storage under ambient (room temperature 20 degrees C) conditions.Higher concentrations of APANA (up to about 50 wt %) may be solubilized in these aromaticesters with gentle heating (50 to 60 deg C). Aromatic esters that may be used include phthalateesters, isophthalate esters, terephthalate esters, trimellitate esters, and benzoate esters. Examplesof specific aromatic esters that may be used include tris-methyl trimellitate, tris-ethyl trimellitate,tris-propyl trimellitate, tris-butyl trimellitate, tris-2-ethylhexyl trimellitate, tris-isooctyltrimellitate, tris-2-ethylhexyl trimellitate, tris-n-octyl trimellitate, tris-isononyl trimellitate, trisisodecyltrimellitate, diethyl phthalate, dipropyl phthalate, dibutyl phthalate, di-2-ethylhexylphthalate, diisooctyl phthalate, di-n-octyl phthalate, diisononyl phthalate, diisodecyl phthalate, ,diethyl isophthalate, dipropyl isophthalate, dibutyl isophthalate, di-2-ethylhexyl isophthalate,diisooctyl isophthalate, di-n-octyl isophthalate, diisononyl isophthalate, diisodecyl isophthalate,diethyl terephthalate, dipropyl terephthalate, dibutyl terephthalate, di-2-ethylhexyl terephthalate,diisooctyl terephthalate, di-n-octyl terephthalate, diisononyl terephthalate, diisodecylterephthalate, 2-ethylhexyl benzoate, isooctyl benzoate, n-octyl benzoate, isodecyl benzoate andbenzyl benzoate. Preferably, methyl trans-cinnamate, diethyl phthalate and / or benzyl benzoateare used as the diluent. One or multiple aromatic esters may be used, such as a combination ofdiethyl phthalate and benzyl benzoate at a ratio of about 2:1 to about 1:2 by weight, preferablyabout 1:1. It is preferred that the closed cup flash point of the aromatic ester is above 93.4 deg C.It is also preferred that the molecular weight of the aromatic ester is above 150 amu, and the boilingpoint is above 300 deg C at 760 mm Hg.A liquid blend of APANA composed of one or more aromatic esters may be prepared bymixing the solid APANA with one or more liquid aromatic esters at between room temperature(20 deg. C) and 60 deg C. The order of addition is not critical. The blend may also be prepared aspart of the manufacturing process for production of solid APANA where the aromatic ester isadded at a point in the process that avoids producing the solid product. This is advantageousbecause it would save considerable cost associated with isolating a solid product, such as avoidingsolvents, a crystallization step and a filtration step.A liquid blend of APANA composed of one or more aromatic esters may be added to afinished lubricant, a lubricant additive concentrate or lubricant additive package at roomtemperature or with gentle heating. Typically, heating is not required. Typical practicaltemperatures for adding such a blend range from 20 deg. C to 60 deg. C. A more preferredtemperature is 20 deg. C to 40 deg. C. Most preferred is 20 deg C to 35 deg. C. The blendcomprising APANA and one or more aromatic esters may be poured or pumped into the finishedfluid, additive concentrate or additive package.A liquid blend of APANA composed of one or more aromatic esters has additional benefitsin finished lubricants. For example, the combination of APANA with one or more aromatic estersshould improve solubility of other additives in additive packages and finished lubricants. Thus,the lubricating composition may comprise a lubricant base, a blend of APANA and aromaticamine, as well as one or more of antioxidants, corrosion inhibitors, rust inhibitors, anti-wearadditives, organic friction modifiers and molybdenum-based friction modifiers.BRIEF DESCRIPTION OF THE DRAWINGSFigs. 1-4 are line graphs depicting a thermogravimetric analysis of the liquid blend for determiningmass loss with respect to temperature for benzyl benzoate and diethyl phthalate blended withoctylated N-phenyl-α-naphthylamine at 30%.Figs. 5-7 are bar graphs showing relative oxidation of a lubricating composition comprising adifferent base oils and the inventive blends of octylated N-phenyl-α-naphthylamine / benzylbenzoate and octylated N-phenyl-α-naphthylamine / diethyl phthalate.DETAILED DESCRIPTION OF THE INVENTIONOctylated N -phenyl-α-naphthylamine (available as VANLUBE 1202 antioxidant fromVanderbilt Chemicals, LLC of Norwalk, CT) is blended with a low molecular weight aromaticester at about 20 degrees C. The esters are preferably benzyl benzoate, diethyl phthalate or amixture of the two. However, it is expected that any of the aromatic esters listed earlier in thespecification could be effective for the stated purpose, namely, providing a stable, liquidenvironment for octylated N-phenyl-α-naphthylamine. The amount of octylated N-phenyl-α-naphthylamine in the blend will range from about 15 to about 35 weight percent, preferably about25-32 wt. %, more preferably about 28-32 wt. %, and most preferably about 30 wt. %.The invention also relates to a lubricating composition comprising a lubricating base of atleast 85% by weight, and a blend of APANA, preferably octylated N-phenyl-α-naphthylamine andaromatic ester in an amount which provides from about 0.01 to about 1.0% of APANA in thelubricating composition, preferably about 0.05 to about 0.2 weight %.Test samples were prepared with VANLUBE 1202 octylated N-phenyl-α-naphthylamine(also labeled as VL 1202 in the figures) at 30% and 40% by weight of the total octylated N-phenyl-α-naphthylamine / ester blend in diethyl phthalate. 30% octylated N-phenyl-α-naphthylamine indiethyl phthalate showed good storage stability after 46 days. 30% octylated N-phenyl-α-naphthylamine diethyl phthalate. 40% octylated N-phenyl-α-naphthylamine in diethyl phthalateshowed crystal fallout after 13 days, suggesting that 40% octylated N-phenyl-α-naphthylamine istoo high to achieve stability and therefore the acceptable limit is below 40%.Liquid samples of 30% and 40% octylated N-phenyl-α-naphthylamine were made in 1:1(by weight) benzyl benzoate:diethyl phthalate solvent mixture. 30% octylated N-phenyl-α-naphthylamine sample in 1:1 benzyl benzoate and diethyl phthalate showed good stability after 76days. Table 1 below shows the results for the 30% and 40% blends in terms of stability.TABLE 1*sample stored cold to simulate variable storage temperatures, then gently heated to redissolve. Roomtemperature stability was confirmed.Sample RTJ 683-113 that was kept in a refrigerator showed crystal fall out. However, upon gentlyheating to 50 degrees C, the solid component dissolved completely and remained clear after 70days at room temperature.Table 2 below shows analytic analysis for the 30% octylated N-phenyl-α-naphthylamine(OPANA) blendsTABLE 2TABLE 3With reference to Figs. 1-4 and Table 3 above, a thermogravimetric analysis (TGA) was done toassess volatility, being measured in terms of weight loss to determine the onset temperature atwhich the blend becomes volatile. A higher onset temperature is preferable. TGA of SWD-689-61 (benzyl benzoate) sample showed better volatility compared to SWD-689-66 (diethylphthalate).With reference to Figs. 5-7, samples of the octylated N-phenyl-α-naphthylamine / benzylbenzoate and octylated N-phenyl-α-naphthylamine / diethyl phthalate (both at 30% octylated Nphenyl-α-naphthylaminewithin the blend) were added to Group I and II base oils at treat rates of0.05, 0.1 and 0.2 weight % octylated N-phenyl-α-naphthylamine and were evaluated forantioxidant activity by means of RPVOT (The Rotating Pressure Vessel Oxidation Test) and PDSC(Pressure Differential Scanning Calorimetry). These data demonstrate that blends of octylated Nphenyl-α-naphthylamine / aromatic esters are within a range of acceptance in terms of antioxidantprotection when compared to using octylated N-phenyl-α-naphthylamine on its own. However,given the ease of handling the inventive blend compared to the solid octylated N-phenyl-α-naphthylamine demonstrates that the blend is an advantageous substitute for solid octylated Nphenyl-α-naphthylamine.

Claims

1. A liquid blend comprising octylated phenyl-α-naphthylamine, and at least one low molecular weight aromatic ester, wherein the octylated phenyl-α-naphthylamine is present from about 15% to about 35% by weight of the blend.

2. The blend of claim 1, wherein the aromatic ester is chosen as one or more in combination of tris-methyl trimellitate, tris-ethyl trimellitate, tris-propyl trimellitate, tris-butyl trimellitate, tris-2-ethylhexyl trimellitate, tris-isooctyl trimellitate, tris-2-ethylhexyl trimellitate, tris-n-octyl trimellitate, tris-isononyl trimellitate, tris-isodecyl trimellitate, diethyl phthalate, dipropyl phthalate, dibutyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, di-n-octyl phthalate, diisononyl phthalate, diisodecyl phthalate, diethyl isophthalate, dipropyl isophthalate, dibutyl isophthalate, di-2-ethylhexyl isophthalate, diisooctyl isophthalate, di-n-octyl isophthalate, diisononyl isophthalate, diisodecyl isophthalate, diethyl terephthalate, dipropyl terephthalate, dibutyl terephthalate, di-2-ethylhexyl terephthalate, diisooctyl terephthalate, di-n-octyl terephthalate, diisononyl terephthalate, diisodecyl terephthalate, 2-ethylhexyl benzoate, isooctyl benzoate, n-octyl benzoate, isodecyl benzoate, methyl trans-cinnamate, and benzyl benzoate.

3. The blend of claim 1, wherein the octylated phenyl-α-naphthylamine is present from about 25% to about 32% by weight of the blend.

4. The blend of claim 3, wherein the octylated phenyl-α-naphthylamine is present at about 30% by weight of the blend.

5. The blend of claim 1, wherein the aromatic ester is chosen from benzyl benzoate, diethyl phthalate and a combination thereof.

6. The blend of claim 3, wherein the aromatic ester is chosen from benzyl benzoate, diethyl phthalate and a combination thereof.

7. The blend of claim 4, wherein the aromatic ester is chosen from benzyl benzoate, diethyl phthalate and a combination thereof.

8. A lubricating composition comprising a lubricant base at 85% or more by weight of the lubricating composition, and a liquid blend comprising octylated phenyl-α-naphthylamine and at least one aromatic ester, wherein the octylated phenyl-α-naphthylamine is present from about 15% to about 35% by weight of the blend, and the blend is present in the lubricating composition in an amount which provides from about 0.01 to about 1.0 weight percent of octylated phenyl-α-naphthylamine in the lubricating composition.

9. The lubricating composition of claim 8, wherein the octylated phenyl-α-naphthylamine is present from about 25% to about 32% by weight of the blend.

10. The lubricating composition of claim 9, wherein the octylated phenyl-α-naphthylamine is present from at about 30% by weight of the blend.

11. The lubricating composition of claim 8, wherein the blend is present in the lubricating composition in an amount which provides from about 0.05 to about 0.2 weight percent of octylated phenyl-α-naphthylamine in the lubricating composition.

12. The lubricating composition of claim 9, wherein the blend is present in the lubricating composition in an amount which provides from about 0.05 to about 0.2 weight percent of octylated phenyl-α-naphthylamine in the lubricating composition.

13. The lubricating composition of claim 10, wherein the blend is present in the lubricating composition in an amount which provides from about 0.05 to about 0.2 weight percent of octylated phenyl-α-naphthylamine in the lubricating composition.

14. The lubricating composition of claim 8, wherein the aromatic ester is chosen from one or more in combination of tris-methyl trimellitate, tris-ethyl trimellitate, tris-propyl trimellitate, tris-butyl trimellitate, tris-2-ethylhexyl trimellitate, tris-isooctyl trimellitate, tris-2-ethylhexyl trimellitate, tris-n-octyl trimellitate, tris-isononyl trimellitate, tris- isodecyl trimellitate, diethyl phthalate, dipropyl phthalate, dibutyl phthalate, di-2- ethylhexyl phthalate, diisooctyl phthalate, di-n-octyl phthalate, diisononyl phthalate, diisodecyl phthalate, diethyl isophthalate, dipropyl isophthalate, dibutyl isophthalate, di-2- ethylhexyl isophthalate, diisooctyl isophthalate, di-n-octyl isophthalate, diisononyl isophthalate, diisodecyl isophthalate, diethyl terephthalate, dipropyl terephthalate, dibutyl terephthalate, di-2-ethylhexyl terephthalate, diisooctyl terephthalate, di-n-octyl terephthalate, diisononyl terephthalate, diisodecyl terephthalate, 2-ethylhexyl benzoate, isooctyl benzoate, n-octyl benzoate, isodecyl benzoate, methyl trans-cinnamate, and benzyl benzoate.