US3414618A

US3414618A - Mono-p-tertiary alkyl diarylamines

Info

Publication number: US3414618A
Application number: US526401A
Authority: US
Inventors: Donald R Randell
Original assignee: Geigy Co Ltd
Current assignee: Geigy Co Ltd
Priority date: 1964-02-11
Filing date: 1966-02-10
Publication date: 1968-12-03
Anticipated expiration: 1985-12-03

Description

United States Patent M MONO-p-TERTIARY ALKYL DIARYLAMINES Donald R. Randell, Cheshire, England, assignor to The Geigy Company Limited, Manchester, England No Drawing. Original application Feb. 10, 1965, Ser. No.

431,709. Divided and this application Feb. 10, 1966,

Ser. No. 526,401 Claims priority, application Great Britain, Feb. 11, 1964,

5,593/64; Feb. 29, 1964, 8,579/64 8 Claims. (Cl. 260-576) ABSTRACT OF THE DISCLOSURE The compounds:

N-p-tertiary octyl-phenyl-a-naphthylamine, N-p-tertiary octyl-phenyl-p-naphthylamine, N-p-tertiary butyl-phenyl-B-naphthylamine, N-p-tertiary butyl-phenyl-u-naphthylamine, N-p-tertiary pentyl-phenyl-u-naphthylamine, N-p-tertiary pentyl-phenyl-B-naphthylamine, N-p-tertiary hexyl-phenyl-a-naphthylamine, and N-p-tertiary hexyl-phenyLB-naphthylamine,

are useful as antioxidants for incorporation into a synthetic lubricant susceptible to oxidative deterioration.

This application is a division of copending application Ser. No. 431,709, filed Feb. 10, 1965, now abandoned.

The present invention relates to organic compounds having valuable antioxidant properties and being useful as additaments to synthetic lubricants requiring antioxidants.

It is known that dialkylated derivatives of conventional antioxidant systems such as diphenylamine and phenothiazine, and synergistic combinations thereof, may be used as antioxidants in ester-based synthetic lubricants, and that these dialkylated derivatives do not have the disadvantage of bringing about the formation of oil-insoluble products in synthetic lubricants at high temperatures, which is encountered if phenothiazine itself is used. It was found that the requirements of standard test specifications could be met by incorporating dialkylated phenothiazines and dialkylated secondary amines, thus avoiding the so-called phenothiazine dirtiness.

However, with the advent of gas turbine engines required to propel aircraft at greater speeds, has come a demand for lubricants which will function satisfactorily at still higher temperatures, at which lubricant compositions comprising the previously suggested dialkylated compounds do not pass the requirements of standard specification tests. For instance, the requirements of the Pratt and Whitney Type II oxidation-corrosion tests, carried out at 425 or 450 F. for 48 hours cannot be met by lubricants containing dialkylated derivatives of diphenylamine and phenothiazine.

It is an object of the present invention to provide improved antioxidants for synthetic lubricants.

The present invention makes it possible to provide a composition which comprises a synthetic lubricant susceptible to oxidative deterioration and as antioxidant, a compound of the formula: ANHB wherein A and B are the same or different and each is an aryl group, and one of the aryl groups A and B contains a tertiary alkyl substituent group having from 4 to 12 carbon atoms.

The synthetic lubricant is preferably a synthetic lubricant based on one or more organic carboxylic acid esters; intended for use at an operating temperature at or above 400 F. Examples of such synthetic lubricants include lubricants based on a diester of a dibasic acid and a monohydric alcohol, for instance dioctyl sebacate or dinonyl adipate; on a triester of trimethylolpropane and a mono- 3,414,618 Patented Dec. 3, 1968 basic acid or mixture of monobasic acids, for instance trimethylolpropane tripelargonate or trimethylolpropane tricaprylate; on a tetraester of pentaerythritol and a monobasic acid or mixture of monobasic acids, for instance pentaerythritol tetracapyrylate; or on complex esters derived from monobasic acids, dibasic acids and polyhydric alcohols; or on mixtures thereof.

Each of the aryl groups A and B may be, for example, a benzene or naphthalene nucleus otherwise unsubstituted or containing further substituents, apart from the tertiary alkyl group which forms a substituent in one of the groups A and B; if either or both of the groups A and B is a naphthalene residue, this may be an ocor fl-naphthyl group. The tertiary alkyl group contains from 4 to 12 carbon atoms, and may be, for example, tertiary butyl (1':1'-dimethylethyl), tertiary pentyl (1':1'-dimethylpropyl), tertiary hexyl (1:1'-dimet-hylbutyl), tertiary octyl (1':1'13:3'-tetramethylbutyl) or tertiary dodecyl (1': l':3:3:5:5'-hexamethylhexyl). The tertiary alkyl substituent preferably has a tertiary carbon atom directly attached to the aryl nucleus of which the alkyl group is a substituent.

If the aryl group A or B which contains theessential tertiary alkyl substituent is an unsubstituted or substituted phenyl group, the tertiary alkyl group is preferably in the 4-position relative to the carbon atom of the benzene ring directly attached to the nitrogen atom of the secondary amine grouping. If the aryl group A or B which contains the tertiary alkyl substitutent is an otherwise unsubstituted or substituted naphthyl group, the tertiary alkyl group is preferably attached in the same or the analogous position as the 4-substituent in a phenyl group. These preferred structures may be represented as follows, wherein R represents the tertiary alkyl group and wherein the aryl nuclei may be otherwise unsubstituted (as shown) or substituted:

aryl-NH- I aryl-NH the aryl group in each instance being an unsubstituted or substituted phenyl, tat-naphthyl or B-naphthyl group.

Examples of such diarylamines used as antioxidants in the composition of the present invention therefore include -4-tertiary pentyl-diphenylamine,

N-p-tertiary pentyl-phenyl-a-naphthylamine,

N-p-tertiary pentyl-phenyl-fl-naphthylarnine,

4-p-( l: 1'13 3 '-tetramethylbutyl -diphenylamine,

N-p-( 1 1 3 3 -tetramethylbutyl -phenyl-a naphthylamine,

N-p-( l: 1 :3 3-tetramethylbutyl -phenyl-fl-naphthylamine,

4-p-( 1': 1' 3 3 5' 5 -hexamethylhexyl -diphenylamine,

N-p-( 1: 1 :3 :3 :5 :5-hexamethylhexyl) -phenyl-m-naphthylamine,

N-p-(l 1:3 :3 :5 :S-hexamethylhexyl)-pheny1- S-naphthylamine.

The mono tertiary alkyl diarylamines used as antioxidants in the composition of the present invention are produced, as hereinbefore set forth, for example, by contacting the corresponding diarylamine with a 1- or 2- alkylene, the total number of carbon atoms in the molecule of the alkylene being from 4 to 12. The reaction with the alkylene is carried out under the conditions hereinbefore disclosed and advantageously in the presence of a Friedel-Crafts catalyst, for instance in the presence of aluminum chloride.

The proportion of antioxidant present in the lubricant compositions can be varied within wide limits. The compositions of the present invention may, for instance, contain from 0.1% to by weight of antioxidant and preferably from 1.5% to 4% by weight based on the total weight of the composition.

The following examples further illustrate the present invention. Parts by weight shown therein bear the same relation to parts by volume as do kilograms to liters. Percentages shown are expressed by weight unless otherwise stated.

Example 1 (A) 169.2 parts by weight of diphenylamine were heated with 140.3 parts by weight of di-isobutylene (a mixture of 75% of 2:4:4-trimethylpentene-1 and of 2:4:4-trimethylpentene-2) and with 2.2 parts by weight of anhydrous aluminum chloride for 15 hours while maintaining the temperature within the range of from 108 to 146 C.

The product was a mixture of 4- and 4:4'-tertiary octyl diphenylamines with unreacted diphenylamine. The desired 4-tertiary octyl diphenylamine was separated from the other constituents of the reaction product by fractional distillation and was recrystallized from aqueous ethanol.

The 4-tertiary octyl diphenylamine thus obtained had melting point 48 to 49 C. and boiling point 150 to 154 C. at 0.22 millimeter of mercury pressure. The conversion achieved was (B) 84.4 parts by weight of 4-tertiary octyl diphenylamine, produced by the procedure described in Example 1A, were heated with 10.2 parts by weight of sulphur for 20 hours while maintaining the temperature within the range of from 200 to 220 C. The reactants were heated until the rate of evolution of hydrogen sulphide was very slow.

The crude reaction product was crystallized from petroleum ether (boiling point range to C.) to produce 3-tertiary octyl phenothiazine, having melting point 118 C. and the following elemental analysis:

Calculated (C H NS): C, 77.11%; H, 8:10%; N, 4.50%; S, 10.14%. Found: C, 76.82%; H, 8.07%; N, 4.52%; S, 10.29%. The yield was 72% theoretical.

Example 2 (A) 657 parts by Weight of N-phenyl-a-naphthylamine were heated with 673 parts by weight of di-isobutylene (having the same composition as that used in Example 1), and 6.6 parts by weight of anhydrous aluminum chloride for 26 hours, while maintaining the temperature at 108 to 136 C.

The product was N-p-tertiary octyl-phenyl-a-aphthylamine, having melting point 76 to 77 C. and the following elemental analysis:

Calculated (C H N): C, 86.96%; H, 8.82%; N, 4.23%. Found: C, 86.94%; H, 8.82%; N, 4.05%. The yield was 62% theoretical.

(B) 109.4 parts by weight of N-p-tertiary octyl-phenyla-naphthylamine, produced by the procedure described in Example 2A were dissolved in 200 parts by volume of xylene and the solution was heated with 21.5 parts by weight of sulphur and 1.1 parts by weight of iodine as thionation catalyst. The mixture was heated at 148 C. for 24 hours.

The thionation product was 9-tertiary octyl 12H-benzo- [a]-phenothiazine, having melting point 147 to 148 C. and the following elemental analysis:

Calculated (C H NS): C, 79.73%; H, 7.53%; N, 3.88%; S, 8.87%. Found: C, 79.35%; H, 7.60%; N, 3.96%; S, 8.93%. The yield was 56% theoretical.

Example 3 (A) The procedure described as Example 2A was carried out using 219.3 parts by weight of N-phenyl-[i-naphthylamine instead of the N-phenyl-a-naphthylamine, the reaction conditions being otherwise the same.

The product was N-p-tertiary octyl-phenyl-B-naphthylamine, having melting point 126 C. and the following elemental analysis: I

Calculated (C H N): C, 86.96%; H, 8.82%; N, 4.23%. Found: C, 87.18%; H, 8.84%; N, 4.40%. The yield was 53% theoretical.

(B) The procedure described in Example 2B was carried out using 87.5 parts by weight of N-p-tertiary octylphenyl-B-naphthylamine, produced by the procedure described in Example 3A, instead of the N-tertiary octylphenyl-a-naphthylamine, the reaction conditions being otherwise the same except that the reaction temperature was maintained in the range of from 210 to 220 C.

The thionation product was IO-tertiary octyl-7H-benzo- [c]-phenothiazine, having melting point 140 C. and the following elemental analysis:

Calculated (C H NS): C, 79.73%; H, 7.53%; N, 3.88%; S, 8.87%. Found: C, 79.91%; H, 7.57%; N, 4.02%; S, 8.66%. The yield was 73% theoretical.

Example 4 On incorporating 4-tertiary octyl diphenylamine prepared as described in Example 1A into an ester-based synthetic lubricant, the product was found to be an effective antioxidant.

Example 5 On incorporating N-p-tertiary octyl-phenyl-u-naphthylamine prepared as described in Example 2A into an esterbased synthetic lubricant, the product was found to be an eifective antioxidant.

Example 6 On incorporating N-p-tertiary octyl-phenyl-fl-naphthylamine prepared as described in Example 3A into an esterbased synthetic lubricant, the product was found to be an effective antioxidant.

Example 7 84.6 parts by weight of diphenylamine, 185 parts by weight of tertiary butyl chloride and 23.7 parts by weight of anhydrous aluminum chloride were reacted together at 35 C. for 3 hours and the mixture was then boiled under reflux for 24 hours. Unreacted tertiary butyl chloride was then removed by distillation; the residue was dispersed in toluene and treated with aqueous sodium hydroxide. The solvent was then evaporated off and the residue was fractionally distilled.

4-tertiary butyl diphenylamine was obtained as distillate in the fraction having boiling point range of 130 to 148 C. at 0.35 millimeter of mercury pressure. 4:4'-tertiary butyl diphenylamine (having melting point 107 to 108 C.) and unreacted diphenylamine were also isolated from the reaction mixture.

The 4-tertiary butyl diphenylamine obtained was purified by crystallization and recrystallization from aqueous ethanol. The product had melting point 67 to 68 C.

On incorporating 4-tertiary butyl diphenylamine into an ester-based synthetic lubricant, the product was found to be an effective antioxidant.

Example 8 To a mixture of 219.2 parts by weight of N-phenyl-pnaphthylamine and 2.2 parts by weight of anhydrous aluminum chloride were slowly added 140.2 parts by weight of isopentene (consisting mainly of 2-methylbutene-l) over 8 hours while maintaining the temperature of the reaction mixture at to C.

N-p-tertiary pentyl-phenyl-Bnaphthylamine produced was isolated from the reaction product, after washing with aqueous sodium hydroxide solution, by fractional crystallization from petroleum ether (boiling point range 60 to 80 C.). The product had melting point 75 C. and the following elemental analysis:

Calculated (C H N): 'C, 87.12%; H, 8.04%; N, 4.83%. Found: C, 87.19%; H, 8.00%; N, 4.80%.

On incorporating into an ester-based synthetic lubricant the product was found to be an effective antioxidant.

Example 9 164.4 parts of N-phenyl-B-naphthylamine were heated to 160 C. with 1.7 parts of anhydrous aluminum chloride for 10 minutes, cooled to 140 C. and iso-butylene gas passed into the mixture until absorption of the gas was complete. The reaction time was approximately 8 hours. The reaction mixture was taken up into toluene and washed with aqueous sodium hydroxide and then water until the washings were neutral. The toluene was distilled off in vacuo and the residue distilled. The fraction boiling point 180 to 182 C./0.3 mm. was recrystallized from petroleum ether (boiling point 60 to 80 C.) to provide 45 parts (representing a yield of 17.3% of the theoretical) of N-p-t-butyl-phenyl-fl-naphthylamine, melting point 77 to 78 C. The product had the following elemental analysis by weight:

Calculated (C H N): C, 87.10%; H, 7.75 N, 5.05%. Found: C, 87.00%; H, 7.81%; N, 5.18%.

On incorporating into an ester-based synthetic lubricant, the product was found to be an effective antioxidant.

Example 10 In a similar manner from 164.4 parts of N-phenyl-anaphthylamine were obtained 100' parts (representing a yield of 48.8% of the theoretical) of N-p-t-butyl-phenyla-naphthylamine, melting point 875 C. (from petroleum ether boiling point 60 to 80 C.). The product had the following elemental analysis by weight:

Calculated (C H N): C, 87.10%; H, 7.75%; N, 5.05%. Found: C, 86.87%; H, 7.73%; N, 4.94%.

Example 11 219.3 parts of N-phenyl-a-naphthylamine were heated to 120 C. with 2.2 parts of anhydrous aluminum chloride, cooled to 100 C. and 105.3 parts of iso-pentene (2-methylbutene-l) added over 2.5 hours. To complete the reaction the mixture was refluxed for 3 hours. The reaction mixture was then taken up into toluene, washed with aqueous sodium hydroxide and finally with water until the washings were neutral. Distillation of the residue after removal of the toluene provided a fraction consisting mainly of unreacted N-phenyl-a-naphthylamine but the residue on recrystallization from methanol provided 69 parts (representing a yield of 23% of the theoretical) of N-p-t-pentyl-phenyl-u naphthylamine, melting point 71 C. The product had the following elemental analysis by weight:

6 Calculated (C H N): C, 87.15%; H, 8.01%; N, 4.84%. Found: C, 86.93%; H, 8.25%; N, 4.79%.

Example 12 Similarly from 438.6 parts of N-phenyl-fl-naphthylamine were prepared 156.5 parts (representing a yield of 43.7% of the theoretical) of N-p-t-pentyl-phenyl-[3-naphthylamine, melting point 76 C. The product had the following elemental analysis by weight:

Calculated: (C H N): C, 87.15%; H, 8.01%]; N, 4.84%. Found: C, 87.12%; H, 8.25%; N, 4.79%.

Example 13 109.5 parts of N-phenyl-a-naphthylamine and 1.1 parts of anhydrous aluminum chloride were heated together for 10 minutes at 145 C. and then 63 parts of 2-methylpentene-l (propylene dimer) added over 4.5 hours at 130 to 140 C. After this addition the crude reaction product was dissolved in toluene, washed to remove the catalyst and the residue after removal of the toluene distilled to,

provide 106 parts (representing a yield of of the theoretical) of N-p-t-hexylphenyl-a-naphthyla'rnine, boiling point 215 C./1 mm. The product had the following elemental analysis by weight:

Calculated C H N): C, 87.08%; H, 8.3 0%; N, 4.62%. Found: C, 86.75%; H, 8.63%; N, 4.41%.

Example 14 Similarly from 109.5 parts of N-phenyl-B-naphthylamine were obtained parts (representing a yield of 56.3% of the theoretical) of N-p-t-hexyl-phenyl-,3-naphthylamine, melting point 51 C. The product had the following elemental analysis by Weight:

Calculated (C H N): C, 87.08%}; H, 8.30%; N, 4.62%. Found: C, 87.14%; H, 8.43%; N, 4.44%.

Having thus disclosed the invention, what is claimed is:

. N-p-tertiary octyl-phenyl-a-naphthylamine.

. N-p-tertiary octyl-phenyl-B-naphthylamine.

. N-p-tertiary butyl-phenyl-fi-naphthylamine. N-p-tertiary butyl-phenyl-a-naphthylamine.

. N-p-tertiary pentyl-phenyl-u-naphthylamine. N-p-tertiary pentyl-phenyl-fi-naphthyla'mine. N-p-tertiary hexyl-phenyl-a-naphthylamine. N-p-tertiary hexyl-phenyl-B-naphthylamine.

No references cited.

CHARLES B. PARKER, Primary Examiner.

P. C. IVES, Assistant Examiner.