CH617717A5 - Process for producing a lithium soap lubricating grease of high dripping point - Google Patents

Description

The present invention relates to a method for producing a lithium soap grease with a high dropping point, containing a lubricating oil and a hydroxy fatty acid lithium soap and a compound of boron as a thickening agent, and a grease produced by the method.

Lubricating greases are superior to lubricating oils in many applications. They are used, for example, to prevent the entry of disruptive foreign substances through a fat pad (use in roller bearings or fabric sleeves), to ensure a very low lubricant requirement (use on axle heads, in bearings with frequent interruptions in operation) to keep maintenance costs low (use in heavy duty accessible bearings or in household machine bearings) or to secure the lubricant requirement at lubrication points with slow sliding movements, high surface pressures and / or strongly changing loads (use for example on agricultural equipment and vehicles).

Aluminum, calcium, sodium and lithium soap greases in particular have become known of the individual types of grease. Lithium soap greases have been used on a large scale for many years. Their widespread use stems from the fact that they combine the essential advantages of calcium and sodium soap greases. This means that they have good water resistance, high shear stability and upper service temperatures above 100 ° C.

However, it has been shown that in many cases, for example when lubricating wheel bearings of some types of cars, the temperature resistance of these greases is no longer sufficient. Especially in vehicles equipped with disc brakes near the wheel bearings, storage temperatures of 180 to 200 ° C have been measured on mountain stretches that require frequent braking. In such cases, when using lithium soap greases of the conventional type, there is a risk that the greases will leak out of the bearings under this load and, under certain circumstances, smear the disc brakes.

Another example is the lubrication of hot air fan bearings. Temperatures from 150 to

200 ° C can be reached in the bearings. Lithium soap greases with dropping points up to 200 ° C can no longer be used to lubricate these bearings.

The subject matter of the invention described in DT-OS No. 2157 207 is to be mentioned as belonging to the prior art, according to which a lithium soap grease can be produced. The thickening system necessary in addition to the lubricating oil reveals three main components: the lithium soap of a hydroxy fatty acid with 12 to 24 C atoms, the lithium salt of a second hydroxy fatty acid with 3 to 14 C atoms and the dilithium salt of a dicarboxylic acid containing 4 to 12 C atoms, this dicarboxylic acid can optionally be replaced by the mono-lithium salt of boric acid.

A consistency-enhancing thickener in a lithium soap lubricating grease has also already been proposed, which consists of 5 to 20% by weight of a lithium soap of a hydroxystearic acid and 0.1 to 3% by weight of the lithium salt of a boron compound, this thickening agent unifying the grease gives extended service temperature range.

Finally, reference is made to DT-OS No. 2 235 098, which aims at a further embodiment of the invention set forth in DT-OS No. 2 157 207, in which the second hydroxy fatty acid contained in the thickening system of the grease is esterified with a lower alcohol should.

It was an object of the present invention to overcome the disadvantages of conventional lithium soap greases and to produce a lithium soap grease which has a high temperature resistance when lubricating rolling bearings, for example, taking into account the fact that the use of both relatively expensive lithium tetraborate and Several hydroxycarboxylic acids at the same time in the thickening system of a lubricating grease meant an increase in costs which was not readily accepted by the market.

To produce a lithium soap grease of the type mentioned, the solution to the problem is that the thickener is prepared by reacting an ester of 12-hydroxystearic acid and boric acid with lithium hydroxide and mixed with a lubricating oil. Methyl, ethyl, propyl, butyl or glycerol esters, preferably methyl esters of 12-hydroxystearic acid, can be used for the reaction.

The lithium soap grease produced by the process is preferably characterized by 5-20% by weight of the lithium soap of 12-hydroxystearic acid and 0.1-3% by weight of boric acid as the lithium salt. The boric acid can be in the form of di- or monolithium borate.

It has been found that the temperature resistance of this improved lithium soap lubricating grease is significantly increased and there is a significantly increased resistance to oxidative influences in addition to a longer lubrication time.

Furthermore, it can be seen that a strong increase in the dropping point can also be determined when using the methyl ester and the dilithium borate.

These greases usually consist of three main components:

the liquid phase - the base oil - the thickener the additives.

The commercial greases usually contain naphthenic mineral oils, paraffinic oils or even weakly refined oils. However, it is also common, especially when lubricating greases are subjected to special stresses, to use synthetic liquids, such as polyalkyl glycols, ester oils made from dibasic acids and monohydric alcohols or from monobasic acids and polyhydric alcohols, silicones, halogenated hydrocarbons or phenyl ethers. For the grease according to the invention

2nd

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

617717

preferably mineral oils and the alkylbenzenes derived from the wake of the alkylbenzene synthesis.

Active ingredients, such as oxidation and corrosion inhibitors, lubricity improvers and high-pressure additives, are commonly used as additives in the grease. 5

It has been found that a content of 7 to 15% by weight (based on the total grease formulation) of the lithium soap of 12-hydroxystearic acid and 0.15-1.5% by weight (also based on the total grease formulation) of boric acid in the form of di- or monolithium borate are sufficient for a satisfactory drop point increase.

Production, formulation and properties of the new grease are demonstrated by the following examples:

15

Comparative example for a conventional grease sample:

10.00 kg 12-hydroxystearic acid l, 73kgLiOH • H2O

0.50 kg boric acid 20

87.77 kg solvate, paraffin-based, 65 cSt / 50 ° C

25th

Manufacturing:

In the presence of 30 kg of solvate, 10.0 kg of 12-hydroxystearic acid were saponified with 1.73 kg of LiOH.H2O, together with 0.5 kg of boric acid in 10 liters of water, at 70 ° C. After dewatering at 100 ° C, the temperature of the mixture was increased to 210 ° C within 2 hours. A further 30 kg of solvate were added at 150 ° C. and the remainder of 27.77 kg of 30 were added at 210 ° C. After subsequent cooling to 60 ° C. with intensive stirring, the batch was homogenized using a corundum disk mill. j

A fat produced according to this formulation and the procedure described had the following data: 35

Dropping point: 221 ° C resting penetration: 269 mm / 10 full penetration: 263 mm / 10

40

Examples of greases according to the invention

example 1

Weighing:

10.00 kg methyl 12-hydroxystearate 0.50 kg boric acid «

1.65 kg LiOH • H2O 87.85 kg solvate, paraffin-based, 65 cSt / 50 ° C

Manufacturing:

10.0 kg of 12-hydroxystearic acid methyl ester together with 25.0 kg of solvate were heated to 85 ° C. in a suitable stirrer container and then saponified with 1.65 kg of LiOH monohydrate, dissolved in 10 liters of boiling water. During the dewatering period at 100 ° C, 0.5 kg of boric acid was added. After dewatering, the temperature of the contents of the kettle was raised to 240 ° C. within 2 hours. Another part of the solvate (25 kg) was added at 155 ° C. during the heating. The remaining solvate was added to the batch after the maximum temperature of 240 ° C. had been reached. The batch was then stirred cold to 60 ° C. At this temperature, the batch was homogenized using a corundum disk mill. The following data were measured from the finished lubricating grease: Drop point: 265 ° C resting penetration: 261 full penetration: 263

Example 2 sample weight:

10.00 kg methyl 12-hydroxystearate 1.50 kg boric acid 2.33 kg LiOH • H2O

86.17 kg solvate, paraffin-based, 65 cSt / 50 ° C

The preparation was carried out according to the same procedure as given in Example 1.

The following data were determined from the finished grease:

Dropping point: 278 ° C resting penetration: 265 full penetration: 269

Example 3 sample weight:

10.00 kg methyl 12-hydroxystearate 1.50 kg boric acid 3.35 kg LiOH • H2O

85.15 kg solvate, paraffin-based, 65 cSt / 50 ° C

In contrast to Examples 1 and 2, in which the proportions of LiOH • H2O added had been calculated for the production of monolithium borate, the proportion of LiOH • H2O stoichiometric for the development of dilithium borate was added in this example.

Using the same procedure as Example 1, the finished fat had a dropping point of 255 ° C., a resting penetration of 288 mm / 10 and a full penetration of 293 mm / 10.

table

example

Comparison 1

2nd

3rd

12-hydroxystearic acid

%

10.00

12-hydroxystearic acid methyl ester

%

10.00

10.00

10.00

LiOH • H2O

%

1.73

1.65

2.33

3.35

Boric acid

%

0.50

0.50

1.50

1.50

Solvat, paraffin-based 65 cSt / 50 ° C

%

87.77

87.85

86.17

85.15

Machine oil raffinate, naphthenic based 58

%

cSt / 50 ° C

Drip point, ° C (DIN 51801)

221

265

278

255

Resting penetration, mm / 10 (DIN 51804)

269

261

265

288

Walk penetration, mm / 10

263

263

269

293

Claims (5)

617717 PATENT CLAIMS 1. A method for producing a lithium soap grease with a high dropping point, containing a lubricating oil and a hydroxy fatty acid lithium soap and a compound of boron as a consistency-enhancing thickener, characterized in that the thickener is prepared by reacting an ester of 12-hydroxystearic acid and boric acid with lithium hydroxide and with a Lube mixed. 2. The method according to claim 1, characterized in that one uses methyl, ethyl, propyl, butyl or glycerol esters, preferably methyl esters of 12-hydroxystearic acid, for the reaction. 3. Lithium soap lubricating grease produced by the method according to claim 1, characterized by a content of 5-20% by weight of the lithium soap of 12-hydroxystearic acid and 0.1-3% by weight of boric acid as the lithium salt. 4. Grease according to claim 3, characterized in that it contains the boric acid in the form of di- or monolithium borate. 5. Grease according to claims 3 and 4, characterized by a content of 7.5-15% by weight of the lithium soap of 12-hydroxystearic acid and 0.15-1.5% by weight of boric acid in the form of di- or monolithium borate .