EP0000514B1 - Phenol-n,n-dioctyl esters of dithiocarbamic acid and lubricants stabilized therewith - Google Patents

Description

The present invention relates to lubricants stabilized with phenol-N, N-dioctyl-dithio-carbamates, or to the use of phenol-N, N-dioctyl-dithiocarbamates for stabilizing lubricants.

Various additives are generally added to mineral and synthetic lubricants to improve their performance properties. In particular, there is a need for additives which are intended to protect the devices to be lubricated from frictional wear. Such wear inhibitors are required to increase the load-bearing capacity of the lubricant and not to have a corrosive effect on the metal parts to be protected.

Alkyl-substituted phenols and dithiocarbams, such as the already widely used commercial products 2,6-di-tert-butyl-4-methylphenol or S-benzyl-N, N-diethyldithiocarbamate, are already generally known in the lubricant sector as antioxidants. US Pat. No. 3,412,026 describes a lubricant composition containing a small proportion of a mixture of antimony-N, N-dialkyldithiocarbamate and dialkylhydroxybenzyl-N, N-diphenyl-dithiocarbamate with good stability. GB-A-1 024 651 describes metal salts of carbamides containing 2,6-dialkylphenol which are to be used as antioxidants and antiwear additives in lubricants. However, it was found that the effects of these metal salt additives are impaired by the formation of residues. W.M. Denton, "Screening of Compounds for Anti-Oxidant Activity in Motor Oil," Inst. Of Pet Review, 2/66, 46-54, describes S- (3,5-di-tert-butyl-4-hydroxy- benzyl) -N, N-di-n-butyl-dithiocarbamate as a lubricant additive.

It has now been found that, surprisingly, an even better antioxidant and anticorrosive effect can be achieved in lubricants by adding a small proportion of selected phenol-N, N-dioctyldithiocarbamic acid esters. These compounds, which have no metal salt character, are also free from the disadvantages arising from the formation of residues.

enthalten, worin

• R C₁-C₁₂ Alkyl, C₅-C₇ Cycloalkyl, gegebenenfalls durch C₁-C₆ Alkyl substituiertes C₆-C₁₀ Aryl, C_I-C₂₂ Aralkyl,
• R₁ und R₂ jeweils unabhängig voneinander H oder R bedeuten und
• R₃ Octyl ist.
  • R ist als C₁-C₁₂ Alkyl verzweigtes oder unverzweigtes Alkyl, wie Methyl, Aethyl, n-Propyl, Isopropyl, n-Butyl, tert.-Butyl, n-Pentyl, a-Methylpentyl, Hexyl, 2,4-Dimethylpentyl, Octyl, 6-Methylheptyl, 2-Aethylhexyl, Decyl, Dodecyl. Bevorzugt sind Alkylgruppen mit 1-8, insbesondere aber solche mit 1-4 C-Atomen.
  • R ist als C₅-C₇ Cycloalkyl, Cyclopentyl, Cyclohpetyl und insbesondere Cyclohexyl.
  • R ist als gegebenenfalls durch C₁-C₆ Alkyl substituiertes C₅-C₁₀ Aryl gegebenenfalls mehrmals jedoch insbesondere einmal durch lineares oder verzweigtes C₁-C₆ Alkyl substituiertes Phenyl oder Naphthyl, wie beispielsweise Methylphenyl oder Methylnaphthyl. Dabei handelt es sich insbesondere um p-substituiertes Phenyl oder in 4-Stellung substituiertes 1-Naphthyl, vorzugsweise jedoch um unsubstituiertes Phenyl oder 1-Naphthyl.
  • R ist als C₇-C₂₂ Aralkyl Phenalkyl oder Naphthalkyl, wobei der Alkylteil jeweils aus verzweigtem oder unverzweigtem C₁-C₁₂ insbesondere jedoch C₁-C₄ Alkyl besteht. Bevorzugte Aralkylreste sind a-Phenäthyl und insbesondere Benzyl.

The present invention accordingly relates to lubricants which, as a stabilizer, are a compound of the formula

included in what

• RC ₁ -C ₁₂ alkyl, C ₅ -C ₇ cycloalkyl, C ₆ -C ₁₀ aryl optionally substituted by C ₁ -C ₆ alkyl, C _I -C ₂₂ aralkyl,
• R ₁ and R ₂ each independently represent H or R and
• R _{3 is} octyl.
  • R is C ₁ -C ₁₂ alkyl branched or unbranched alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, tert-butyl, n-pentyl, a-methylpentyl, hexyl, 2,4-dimethylpentyl, Octyl, 6-methylheptyl, 2-ethylhexyl, decyl, dodecyl. Alkyl groups with 1-8, but especially those with 1-4 C atoms are preferred.
  • R is C ₅ -C ₇ cycloalkyl, cyclopentyl, cyclohpetyl and especially cyclohexyl.
  • R is C ₅ -C ₁₀ aryl which is optionally substituted by C ₁ -C ₆ alkyl, but is optionally substituted several times, in particular once by linear or branched C ₁ -C ₆ alkyl, phenyl or naphthyl, such as, for example, methylphenyl or methylnaphthyl. These are in particular p-substituted phenyl or 1-naphthyl substituted in the 4-position, but preferably unsubstituted phenyl or 1-naphthyl.
  • R as C ₇ -C ₂₂ aralkyl is phenalkyl or naphthalkyl, the alkyl part in each case consisting of branched or unbranched C ₁ -C ₁₂ but especially C ₁ -C ₄ alkyl. Preferred aralkyl radicals are a-phenethyl and especially benzyl.

The dithiocarbamate group is bonded to the phenol ring in the o- or in particular in the m- or p-, but preferably in the p-position to the hydroxyl group.

• R und R₁ C₁-C₈ Alkyl, Phenyl oder Benzyl und
• R₂ Wasserstoff oder C₁-C₈ Alkyl sind und
• R₃ Octyl bedeutet,

wobei die Dithiocarbamatgruppe in m- oder p-Stellung zur Hydroxylgruppe des Phenols steht.To be emphasized are lubricants which contain a compound of the formula I as stabilizer, in which

• R and R _{1 are} C ₁ -C ₈ alkyl, phenyl or benzyl and
• R _{2 are} hydrogen or C ₁ -C ₈ alkyl and
• R ₃ means octyl,

wherein the dithiocarbamate group is in the m- or p-position to the hydroxyl group of the phenol.

enthalten, worin

• R und R₁ C₁-C₄ Alkyl und
• R₂ Wasserstoff oder Methyl sind.

Of particular interest are lubricants that act as a stabilizer, a compound of formula IV

included in what

• R and R _{1 are} C ₁ -C ₄ alkyl and
• R _{2 are} hydrogen or methyl.

enthalten, worin R und R₁ C₁-C₄ Alkyl bedeuten.Lubricants which are a stabilizer are a compound of the formula

contain, wherein R and R _{1 are} C ₁ -C ₄ alkyl.

enthalten, worin R und R₁ C₁-C₄ Alkyl sind.Also preferred are lubricants that act as a stabilizer, a compound of the formula

included, wherein R and R _{1 are} C ₁ -C ₄ alkyl.

worin R-C₁-C_1Z Alkyl, C₅-C₇ Cycloalkyl, gegebenenfalls durch C₁-C₆ Alkyl substituiertes C₆-C₁₀ Aryl, C₇-C₂₂ Aralkyl und R₁ und R₂ jeweils unabhängig voneinander H oder R bedeuten.The invention also relates to compounds of the formula

wherein RC ₁ -C _1Z alkyl, C ₅ -C ₇ cycloalkyl, C ₆ -C ₁₀ aryl optionally substituted by C ₁ -C ₆ alkyl, C ₇ -C ₂₂ aralkyl and R ₁ and R ₂ each independently represent H or R. .

mit den äquivalenten Mengen entsprechender Na-dithiocarbamate der Formel

in einem inerten Lösungsmittel wie Acetonitril, Toluol, Aether oder Chloroform unter Abspaltung von NaCI umsetzt.The hydroxybenzyl-N, N-dioctyl-dithiocarbamates to be used according to the invention can be obtained by generally known methods, for example by using mono- or di-chloromethylphenols of the formulas

with the equivalent amounts of corresponding Na dithiocarbamates of the formula

in an inert solvent such as acetonitrile, toluene, ether or chloroform with the elimination of NaCl.

mit Formaldehyd, Schwefelkohlenstoff und einem Amin der Formel

The ortho- and in particular the para-hydroxybenzyl-dithiocarbamates can be obtained analogously in the manner cited above for the meta derivatives, but they are preferably prepared by known methods by reacting molar amounts of a corresponding substituted phenol of the formula.

with formaldehyde, carbon disulfide and an amine of the formula

Even in very small amounts, the compounds of the formula act as stabilizers against the oxidation and corrosion effects in lubricants. Mineral and synthetic lubricating oils and mixtures thereof, which contain 0.001 to 5% by weight, based on the lubricant, and preferably 0.02-3% of a compound of the formula I, have excellent lubricating properties, which are due to greatly reduced wear and tear on the lubricants Friction partners become clear.

The lubricants in question are familiar to the person skilled in the art and e.g. in the "Lubricant Pocket Book" (Hüthig Verlag, Heidelberg, 1974). Mineral oils are particularly suitable.

The lubricating oil formulation can additionally contain other additives that are added to improve certain performance properties, such as antioxidants, metal passivators, rust inhibitors, viscosity index improvers, pour point depressants, dispersants / surfactants and other wear protection additives.

Examples of antioxidants are:

• a) Alkylated and non-alkylated aromatic amines and mixtures thereof, for example: dioctyldiphenylamine, (2,2,3,3-tetramethylbutyl) phenyl-cr- and ß-naphthylamine, phenothiazine, dioctylphenothiazine, phenyl-a-naphthylamine , N, N'-di-sec-butyl-p-phenylenediamine.
• b) Sterically hindered phenols, for example: 2,6-di-tert-butyl-p-cresol, 4,4'-bis (2,6-diisopropylphenol) -, 2,4,6-triisopropylphenol, 2.2 '-Thio-bis- (4-methyl-6-tert-butyl-phenol), 4,4'-methylene-bis- (2,6-di-tert-butylphenol).
• c) Alkyl, aryl or alkaryl phosphites e.g. trinonyl phosphite, triphenyl phosphite, diphenyldecyl phosphite.
• d) esters of thiodipropionic acid or thiodiacetic acid, e.g. Dilauryl thiodipropionate or dioctyl thiodiacetate.
• e) Combination of two or more antioxidants of the above, e.g. an alkylated amine and a sterically hindered phenol.

Examples of metal passivators are

• a) for copper, for example:
  Benzotriazole, tetrahydrobenzotriazole, 2-mercaptobenzotriazole, 2,5-dimercaptothiadiazole, salicylidene propylene diamine, salts of salicylaminoguanidine.
• b) for lead, for example:
  Sebacic acid derivatives, quinizarin, propyl gallate,
• c) Combination of two or more of the above additives.

Examples of rust inhibitors are

• a) Nitrogen-containing compounds, for example:
  • I. Primary, secondary or tertiary aliphatic or cycloaliphatic amines and amine salts of organic and inorganic acids, for example oil-soluble alkyl ammonium carboxylates.
  • 11. Heterocyclic compounds, for example: substituted imidazolines and oxazolines.
• b) phosphorus-containing compounds, for example:
  • Amine salts of phosphoric acid partial esters,
• c) Sulfur-containing compounds, for example:
  • Barium dinonylnaphthalene sulfonates, calcium petroleum sulfonates,
• d) combinations of two or more of the above additives.

Examples of viscosity index improvers are

Polymethacrylates, vinyl pyrrolidone methacrylate copolymers, polybutenes, olefin copolymers, styrene / acrylate copolymers.

Examples of pour point depressants are

Polymethacrylates, alkylated naphthalene derivatives.

Examples of dispersants / surfactants are polybutenyl succinic acid imides. Polybutenylphosphonic acid derivatives, basic magnesium, calcium and barium sulfonates and phenolates.

Examples of other wear protection additives are

Compounds containing sulfur and / or phosphorus and / or halogen, such as sulfurized vegetable oils, zinc dialkyldithiophosphates, tritolyl phosphate, chlorinated paraffins, alkyl and aryl disulfides.

The preparation of the compounds to be used as stabilizers in the lubricants according to the invention and the use and action of the lubricant compositions according to the invention are described in more detail in the following examples.

Manufacturing examples Example 1: S- (3-Hydroxy-4-tert-butyl-2,6-dimethylbenzyl) -N, N-di-n-octyldithiocarbamate.

34 g of N, N-di-n-octyldithiocarbaric acid sodium salt are dissolved in 300 ml of acetonitrile and with stirring at 10 ° C. within 30 minutes with a solution of 22.7 g of 3-hydroxy-4-tert-butyl-2, 6-dimethyl-benzyl chloride (see see Macromolecular Chemistry, Volume 9 (1952), pages 21/22) in 50 ml of toluene. The reaction mixture is then stirred for about 15 hours at 20-25 ° C, with a sodium chloride separation being observed.

The mixture is then poured into about 1 liter of ice water, the toluene phase is separated off after the addition of a further 100 ml of toluene, shaken out with water, dried over calcium chloride and evaporated in vacuo. The S- (3-hydroxy-4-tert-butyl-2,6-dimethylbenzyl) -N, N-di-n-octyl-dithiocarbamate remains as a brownish viscous oil and is already sufficiently pure and suitable for use as a stabilizer elementary analytical and chromatographic largely uniform.

Further hydroxybenzyldithiocarbamates, the di-n-octyl (Example 2) to be used according to the invention and the di-n-butyl (Example 3) derivatives to be compared are listed in the following table. They are obtained by known methods, preferably by reacting appropriate phenols (column 2 of the table) with formaldehyde, carbon disulfide and the corresponding secondary amine (column 3 of the table) (for example according to US Pat. No. 2,757,174).

Examples of use Example 5: Oil Oxidation Test, Standard Version According to ASTM D 2272 (Rotary Bomb Oxidation Test)

An oil sample of 50 ml "Rotary Vacuum Oil" from SHELL (viscosity 11 cSt./100:000*) is added to a 0.25 g stabilizer in a glass vessel together with 5 ml of distilled water and a bright polished, petroleum ether-washed catalytic copper spiral oxidized in an oxygen atmosphere.

The glass vessel is in a stainless steel bomb with a pressure gauge. The bomb rotates axially at 100 rpm. at an angle of 30 ° to the horizontal, in an oil bath at 150 ° C. The oxygen pressure is initially around 6 atm (90 psi) before heating, rises to 150 ° C to just under 14 atm (200 psi) and remains constant until oxidation begins. The test is complete when the pressure drops by 1.7 Atm (25 psi). The time is recorded in minutes.

To compare the effects, the following were included in the test series:

Example 6 Oil oxidation test according to IP 280, "CIGRE"

• Modified version with soluble Cu and Fe catalyst.
• Conditions: Introduce 4 hours of oxygen at 150 ° C (4 liters of O ₂ / h).
• Determination of the acid number after the end of the test; Table value: mg KOH consumption per g test oil.
• Stabilizer concentration: 0.5%
• Test oil: Shell Rotary Vacuum Oil (viscosity 11 cSt./100 ° C).
  

Example 7 Testing the effect as an antioxidant and anticorrosive agent in gas turbine oil using the FTMS 5308 method. C

• Conditions: air introduction for 3 days at 174 ° c
• Stabilizer concentration: 0.5%
• Test oil: Shell Rotary Vacuum Oil (viscosity 11 cSt./100 ° C).
  

Claims (12)

1. A lubricant containing as stabiliser a compound of the formula I

wherein

R is C₁-C₁₂ a(kyl, C₅-C7-cycloalkyl, C₆-C₁₀-aryl which is unsubstituted or substituted by C₁-C₆- alkyl, or it is C₇-C₂₂-aralkyl,

R₁ and R₂ independently of one another are each H or R, and

R₃ is octyl.

2. A lubricant according to Claim 1, which contains as stabiliser a compound of the formula I, wherein

R and R₁ are each C₁-C₈-alkyl, phenyl or benzyl, and

R₂ is hydrogen or C₁-C₈-alkyl, and

R₃ is octyl,

the dithiocarbamate group being in the m- or p-position with respect to the hydroxyl group of the phenol.

3. A lubricant according to Claim 1, which contains as stabiliser a compound of the formula IV

wherein

R and R, are C₁-C₄-alkyl, and

R₂ is hydrogen or methyl.

4. A lubricant according to Claim 1, which contains as stabiliser a compound of the formula

wherein

R and R₁ are each C,-C_4-alkyl.

5. A lubricant according to Claim 1, which contains as stabiliser a compound of the formula

wherein

R and R₁ are each C₁-C₄-alkyl.

6. A lubricant according to Claim 1, which contains as stabiliser S-(3-hydroxy-4-tert.-butyl-2,6-dimethylbenzyl)-N,N-di-n-octyl-dithiocarbamate.

7. A lubricant according to Claim 1, which contains as stabiliser S-(3,5-di-tert-butyl-4-hydroxybenzyl)-N,N-di-n-octyl-dithiocarbamate.

8. The use of a compound of the formula I as a stabiliser of lubricants according to Claim 1.

9. The use of a compound of the formula I as a stabiliser of mineral oils, according to Claim 1.

10. A compound of the formula

wherein

R is C₁-C₁₂-alkyl, C₅-C₇-cycloalkyl, C₆-C₁₀-aryl which is unsubstituted or substituted by C₁-C₆- alkyl, or it is C₇-C₂₂-aralkyl, and

R₁ and R₂ independently of one another are each H or R.