DE942586C - Additives to lubricants and turbine oils based on mineral lubricants - Google Patents

Description

The invention relates to additives for lubricants and turbine oils based on mineral lubricating oils, which are to be used under conditions in which the oil film tends to tear, the Tearing of the oil film takes place especially when the pressure between the bearing surfaces is very high is.

Lubricants with high oil film tear strength have already been provided. Such lubricants are commonly traded as “super high pressure lubricants” known.

It is an object of the present invention to provide lubricants with extreme pressure properties which Contain additives which practically do not tend to the oxidation of the in use Accelerate oils.

It is another particular object of the present invention to provide additives which are disclosed in US Pat Are able to significantly increase the tensile strength of lubricating oils for turbines and / or hypoid gears without increasing their tendency to oxidize or emulsify with water at the same time increase.

Many of the more commonly used extreme pressure additives are harmful in one or more ways. So z. B. chlorine compounds tend to

have in common to favor oxidation, and likewise they tend to hydrolysis with the resultant Release of hydrochloric acid, which in turn accelerates the rusting of the iron-containing metal parts. Many sulfur compounds also favor oxidation, and those that do so in this regard are without effect, usually have no adequate ones High pressure properties.

It now became a class of organic sulfur compounds found which surprisingly effective maximum pressure properties have, which here but does not increase the oxidation, the corrosion of ferrous metal parts or the emulsification of the oil and which can therefore be used with turbine oils with impunity.

These compounds are the esters of acetic acid, which are in the α-position by sulfur or selenium are substituted and by the general formula

ROOCCH ₂ - (X) _n -CH ₂ -COOR

are represented, wherein the radical R is an aryl or cycloalkyl or preferably not more than Alkyl radical containing 6 carbon atoms, which at the use as additives for lubricants may contain halogen substituents, X sulfur or Means selenium and w = 2, 3 or 4 for -X = sulfur and 2 or 3 for X = selenium.

The radicals R can thus contain halogen substituents, although, as already indicated, the presence Avoid halogen when the compounds are intended for certain uses, in particular in turbine oils.

It appears as if the presence of those attached to the α-position on the di- or polysulfide groups Ester groups have an activating influence with the resulting build-up of extreme pressure properties has, and indeed considerably higher than what one can get through use the simple aliphatic, aromatic or aryl-substituted aliphatic di- or polysulfides receives.

According to the present invention, a lubricant composition essentially comprises a mineral one Lubricating oil base and a smaller proportion that is practically sufficient to ensure the load-bearing capacity of the To increase oil, an ester of acetic acid of the type mentioned above.

The present invention also extends to the use of the additives mentioned for turbine oils, which is a mineral lubricating oil base with a content of agents that promote oxidation Control the stability and corrosion of ferrous metals.

Specific examples of compounds used as additives in the sense of the invention are diethyl dithiodiacetate, di-n-butyltrithiodiacetate, Diphenyl dithiodiacetate, di-n-butyl diselenodiacetate and di-n-butyl tetrathiodiacetate.

It has surprisingly been found that the presence of substituents such. B. of alkyl groups or ester-substituted alkyl groups, which are bonded to the carbon atom next to the X radical, leads to a considerable loss of load capacity. Thus, in addition to the presence of ester groups in the α-position, the presence of unsubstituted CH ₂ groups also appears to be essential in order to bring about the excellent maximum pressure properties referred to.

Even if it can be assumed that at least some of the. the additional connections mentioned above are and have not yet been produced, they can all by methods known to those skilled in the art be generated. So you can z. B. by the reaction of the corresponding α-chlorine or α-bromo ester with sodium disulfides or polysulfides in alcoholic solution or by oxidation of the α-mercaptoesters, to give the corresponding disulfides, or by reaction of the α-mercaptoesters with sulfur dichloride or sulfur monochloride in a non-ionizing solvent to remove the tri- or the Tetrasulfide to be produced.

The additives used must of course be in the mineral oil base in the proportions in which they are intended to be used, be soluble. The preferred compounds are those made with oil are miscible in all proportions, although others of lower solubility will also be satisfactory can be used. The oil solubility necessarily depends on the nature of the R groups, however, in general, complete miscibility with oil can be achieved by using the R radical an aliphatic or cycloaliphatic radical having not less than 4 carbon atoms is used.

The amounts of additives used depend on the purpose for which the oil is being used shall be. It can be any amount, from the minimum sufficient to any appreciable increase to bring about the tear resistance of the oil film, up to about 10 percent by weight can be used, however, proportions of about 0.5 up to about 2 percent by weight, calculated on, are generally preferred the mineral lubricating oil, especially for use in turbine oils.

The so-called "inhibited" turbine oils to which the compounds according to the invention can be added normally contain additives counteracting oxidation, which can be of the alkylated phenol type, e.g. B. tertiary butyl cresol, 2: 4-dimethyl-6-tertiary-butyl-phenol, 2; 6-di-tertiary-butyl-p-cresol, or of the secondary aromatic amine type, e.g. B. diphenylamine, phenyl - α - naphthylamine, phenyl -β- naphthylamine, as well as rust-preventing additives, which belong to different types, a preferred class of additives are the acidic esters of the long-chain 1x5 monoesters of polyhydric alcohols, such as de in the British Patent 643,025.

Some of the additives considered, especially the tri- and higher polysulfides, tend to be to attack copper and copper alloys somewhat at elevated temperatures. In such cases it is also desirably a copper anticorrosion agent of the type disclosed in British Patent 561,941 is described to incorporate, e.g. B. mercaptobenzothiazole, benzothiazole disulfide, benzothiazole hydroxy

methyl sulfide, or tetramethyl or tetramethylthiuram disulfide.

The additives according to the invention can, if desired, in the mineral lubricating oils to be provided, z. B. Extreme pressure lubricating oils for hypoid gears, together with organic halogenated compounds are used, oils which contain such combinations of additives are capable of withstand higher loads than oils, which

ίο only contain the sulfur compound. As above however, the presence of halogen compounds in turbine oils is undesirable. In order to demonstrate the effectiveness of the compounds according to the invention as extreme pressure agents, tests were carried out on the well-known Society of Automotive Engineers (SAE) testing machine. A description of this machine can be found in the Coordinating Handbook (1946) Research Council (CRC) on pages 458 to 462. This machine was rotated at 500 rev / min. operated, with a normal load of around 34 to 38.5 kg / sec. and a friction ratio of 14.6: 1 were used.

The additives were dissolved in a mineral oil mixture (oil A). This mixture consisted of 70% of one Mineral oil with a viscosity of about 170 redwood seconds at 60 ° C and 30% of one as a solvent used refined mineral oil with a viscosity of about 65 redwood seconds at 60 ° C.

The results obtained are shown in the table below, with the given breaking loads generally represent the mean of several experiments.

Certain other closely related compounds were simultaneously tested for superiority to detect the compounds according to the invention. In the majority of cases the percentages were the The additives used are adjusted so that the amount of sulfur added is 0.23 to 0.28% belief.

link

Through the
Additive
imported
sulfur
in ° / " Breaking load
in kg - about 31.6 1.0 0.23 around 104 1.0 0.28 127 o, 75
1.0 0.27
0.36 124 "
140 1.2 o, 34 - 156 1.0 - - 136 1.0 0.26 - 52 0.8 0.25 - 56 1.0 0.26 41 2.5 0.25 - 45 i, 5 0.32 scattered
Results, no
over around 54 i, 5 0.24 around 41

1. None

2. Di- (n-butyl) dithiodiacetate ..

3. Di- (n-butyl) -trithiodiacetate.,

4. Di (n-butyl) tetrathiodiacetate

5. Di - (/? - chloroethyl) -dithiodiacetate *)

6. Di (n-butyl) diselenodiacetate

7. dibenzyl disulfide,

8. Dibenzyl trisulfide (31.7 ° / ₀ S)

9. Diphenyl disulfide

10. Di (n-butyl) monothiodiacetate

11. Di (n-butyl) di - /? - thiodipropionate.

12. Di (n-butyl) dithio-bis (a-a-dimethyl) diacetate

*) This compound has a rather limited oil solubility.

From the previous test results it can be seen that the compounds according to the invention (No. 2 to 6) have a visible advantage over: a) the usual di- and polysulphides (No. 7 to 9), b) the corresponding monosulfides (No. 10),

c) a closely related ester which has a disulfide group in the /? position to the ester group instead of in the α-position (No. 11), and

d) a compound which contains alkyl substituents attached to the disulfide group (No. 12).

For best results, it seems to be desirable that the R radicals are made proportionately short alkyl chains, as the introduction of large or cyclic groups tends to to reduce the resilience. It is therefore preferably selected R radicals, which from Alkyl radicals with no more than 6 carbon atoms exist.

In order to demonstrate the effectiveness of the compounds according to the invention when they are used to impart extreme pressure properties to turbine oils, an “ inhibited ” turbine oil (B oil) was used in accordance with the OM. 88 selected by the British Admiralty. This oil was similar to the Α oil and contained 0.5% of an antioxidant of the type

the secondary aromatic amines, and 0.07 ° / ₀ iron corrosion protection substance consisting of

one

Ethylene glycol mononaphthenate acid phthalate.

The table below shows the effect of the additives according to the invention on the properties of B oil:

Additives Acidity
in mg
KOH / g. Emulsion
resistant
speed Oxydai
Acidity
after
oxidation ion test
Emulsion
resistant
speed
after
oxidation Saltwater
Corrosion test SAE
Maschi
test
η = 500 ι. None 0.08
0, I ₇ *)
0.08
0.20
0.08
0.15 180 "
195 "
180 "
180 "
135 "
150 " 0.17
0.14
0.17
0.08 540 "
330 "
480 "
225 " no rusting
no rusting
no rusting
approach
of rust 150
340
250
275 ' 2. Diethyl dithiodiacetate (2%)
3. Di- (n-butyl) -trithiodiacetate (1.5 ° / ₀ )
+ Benzothiazole disulfide (0.1 ° / ₀ )
4. Di (n-butyl) trithiodiacetate (1%)
- | - Mercaptobenzothiazole (0.05 ° / ₀ )
5. Dicyclohexyl-dithiodiacetate (1.5 ° / ₀ ) ....
6. Di- (n-butyl) -diselenodiacetate (jc ° / _o )
+ Benzothiazole disulfide (0.1 ° / ₀ )

The methods used to determine the various values given above were Standard procedures, as described in the "Standard Methods for Testing Petroleum and its Products" for petroleum and its products) are described under the following reference numbers: Acidity, I.P. 1/46, method A (p. 1, edition 19.51); Emulsion Resistance, I.P. 19/51 (p. 117, edition 1951); Oxidation test, LP. 114/47 (p. 363, edition 1951); Saltwater Corrosion Test, I.P. 135/51 (p. 390, 1951 edition); this latter attempt was made regarding Saltwater composition and duration changed to meet the requirements of regulation OM. 88 the Meet British Admiralty.

From the previous test results it is closed

see that the additives according to the invention do not only significantly increased the load capacity of the turbine oil in which they were dissolved, but also

did not affect the most essential properties of the oil, i.e. its low acidity low demulsification value or high emulsion resistance, its high resistance to Oxidation and the ability to prevent corrosion of the iron

"Inhibit 50 containing metals by salt water.

Any tendency of the oils to corrode copper under the conditions of the normal copper strip corrosion test (I.P. 64/51, method C, p. 550, Aus' would give "195-1), i.e. three hours of immersion at 100 ° C, to exclude completely, it was found necessary to generally use a copper anti-corrosion agent the type already described. Examples of satisfactory combinations of such additives have been listed in the previous table. Here it is generally preferred to use the di- and trisulphides, since the activity of sulfur in the tetrasulphides is greater and is more difficult to regulate.

^a 5 *) The somewhat higher acidity in this case is due to the presence of a trace of acid in the additive.

Ir.an obtained comparative values for certain of the oils through the use of a high-speed disk testing machine in which two disks were in use with hardened steel En. 36 with a diameter of around 203 and 101.5 mm at speeds of 1800 and 7200 respectively Rev / min were rotated in contact with each other at a sliding speed of 1 and 1160 m / min. The disks were immersed in the test oil, which was kept at a temperature of around 69 to around 74 ^° C., and the load on the disks was gradually increased until seizure occurred. The results were recorded as Sc. Loads (scavenging loads) at the onset of feeding. Here the expression Sc. to be defined as follows:

453) 59 % load per 2.54 cm length of the contact line. (Relative radius of curvature) 0.8

Six tests were run on each of the oils listed below, and the mean Sc. Loads were given for each oil. The C oil was a typical turbine oil of similar Viscosity as' the B oil and contained oxidation as well as Rust protection materials.

1. C oil,

2. B-oil + i ° / o di (n-butyl) -] trithio-diacetate, 0.05 ° / ₀ mer \ kaptobenzothiazol J

3. B-oil + 1.50 / 0 di- (n-butyl) -] trithio-diacetate, 0.1% / ₀ benzo- \ thiazole-disulphide J

Medium

Sc.load at the onset of feeding in kg.

around 590 over around 5 750

over 5,750

In the case of oils 2 and 3, three and six tests were carried out up to a limit load of around 5750 kg no eating was observed, after which the experiments were not continued. The other three Trials with No. 2 oil ended at lower loads without any seizure occurring were.

To illustrate the effect of lubricating oil compositions intended for use as extreme pressure lubricants are suitable for hypoid gears, according to the invention, connections were made in one as D-oil called, relatively viscous mineral mixture dissolved. This D-oil consisted of 27 parts by weight of one refined in the usual way

Pennsylyania-Bright Stock oil having a viscosity of 600 Redwoodsekunden at 6o ^Q C, 34 parts of in the usual way Mid-content of a bright stock refined used as the solvent having a viscosity of 750 Redwoodsekunden at 6o ° C, 3 parts of

refined neutral oil with a viscosity of 65 redwood seconds at 60 ° C and 23 parts of one refined distillate of paraffins of similar viscosity used as solvent. Typical Mixtures have been tried on already

as described SAE machine, which, however, operates at a speed of 750 rev / min. instead of 500 rev / min. as operated before:

oil

A. 89.8% D oil

8.0% chlorinated paraffin

(4oo / ₀ chlorine)

2.0% di- (n-butyl) -dithio-

diacetate

0.2% mercaptobenzothiazole ..

B. 91.9% D oil

5.0 ° / ₀ hexachloroethane

3.0% di- (2-ethyl-hexyl) -

trithiodiacetate ..-

0.1% tetraethyl thiuram

disulfide

Tensile strength in kg

around 197

around 184

The normal requirement for a good high pressure hypoid gear lubricant is that it be under must withstand loads of up to around 158 kg under these conditions.

Claims (5)

Patent claims: 1. Use of acetic acid esters substituted in the α-position by sulfur or selenium the general formula ROOC • CH ₃ - (X) _n - CH ₂ • COOR as additives to lubricants and turbine oils based on mineral lubricating oil in amounts of up to 10 percent by weight, preferably 0.5 to 2 percent by weight, calculated on the mineral lubricating oil, where in the general formula R contains an aryl or cycloalkyl or preferably no more than 6 carbon atoms Alkyl radical which, when used as additives for lubricants, can contain halogen substituents, X denotes sulfur or selenium and η 2, 3 or 4 for X = sulfur and 2 or 3 for X = selenium. 2. Embodiment of the invention according to claim i, characterized by the use of di- (n-butyl) -dithiodiacetate and / or di- (n-butyl) -trithiodiacetate. 3. Embodiment of the invention according to claim ι and 2, characterized by the further Use of known anti-corrosion agents for copper or copper-containing metals, such as Mercapto-arylene-thiazoles or their derivatives, e.g. B. Benzothiazole disulfide or Alky "- iiiuramdisulfide, in amounts up to 1 weight per unit. .ent, preferably 0.05 to 0.3 percent by weight, calculated on the mineral lubricating oil. 4. Embodiment of the invention according to spoke ι to 3, characterized by the further Use of known additives of antioxidants and anti-corrosion agents for ferrous' Metals in amounts up to 1 percent by weight, preferably 0.05 to 0.5 percent by weight, or up to 0.5 percent by weight, preferably 0.005 to 0.1 percent by weight, calculated on the Mineral lubricating oil. 5. Embodiment of the invention according to claim ι to 4, characterized by the further Use of a per se known addition of chlorinated paraffins or chlorinated aliphatic Hydrocarbons as additives to lubricating oils in amounts of up to 15 percent by weight, preferably 0.5 to 10 percent by weight, calculated on the mineral lubricating oil. 509 706 4. 5 &