DE723649C - lubricant - Google Patents

Description

The invention relates to a lubricant, in particular for internal combustion engines. The lubricating oils according to the invention have the property of seizing from piston rings when these machines are running for a long time and are in able to lubricate the cylinders and pistons in a suitable manner under heavy loads.

It is known that in modern internal combustion engines, how fast-running Diesel engines or aviation gasoline engines, which, as a result of their high performance, contribute relatively high Tempieraturen work, the piston rings for seizing in the Grooves tend. The main reasons for this seem to be the formation of paint and / or carbon to lie. It is known to use small amounts of certain salts of oil-soluble carbon

ao acids, such as polyvalent metal salts of Fatty and naphthenic acids, or compounds of the calcium phenyl stearate type add to reduce the tendency for the rings to seize. The clogging but small amounts of the aforementioned salts or soaps has one or more, the following disadvantages: The newer bearing metals, such as lead bronze or Cadmium alloy, are made by the soaps of the naphthenic acids and the aliphatic Acids attacked particularly badly. The soaps are among those occurring during lubrication Destroyed at high temperatures, and the additives lose their effectiveness as a result. Certain of the aforementioned salts lead to gelatinization in the lubricants, while others change during use settle out of the lubricating oil.

It has now been found that the salts of polyvalent metals of aromatic,

Optionally substituted monocarboxylic acids, in particular the basic salts of these Acids, when added to mineral oils in small amounts, prevent seizure Prevent rings and do not have the aforementioned disadvantages. These salts show, presumably as a result of their greater heat resistance, a greater effectiveness in oils than salts of aliphatic carboxylic acids or the ίο naphthenic acids. The additives used according to the invention also stand out against each other Calcium phenyl stearate is characterized by the fact that it is not under the working conditions split and become corrosive. The particular ones to be considered polyvalent metals are those of the second and third groups of the periodic; Systems: the salts of zinc, magnesium, calcium and aluminum have been found to be the most effective proven.

It can be the salts, of mononuclear aromatic Acids, such as benzoic acid, or polynuclear acids, such as naphthoic acid, be used.

In general, the substances added according to the invention need to be in the lubricants to be only slightly soluble, since the desired effect is often achieved by adding small amounts is achieved. In most cases, solubility of a few will suffice Tenths of a percent to a few percent off.

'Salts of aromatic monocarboxylic acids with substitution groups generally have a greater solubility in lubricating oil than the corresponding salts of the unsubstituted Acids. Suitable substituents are hydrocarbon radicals (alkyl or aryl radicals), Alkoxy, hydroxyl or aroxy groups, halogens, amino groups with or without hydrocarbon radicals as substituents. If several of these substituents are present, they can be the same or different Be kind.

Zinc benzoate dissolves so z. B. in a furfural-refined Venezuelan lubricating oil distillate up to about 0.3 percent by weight; the zinc methyl benzoate dissolves up to about 1 percent by weight, the zinc salt of p-tcrt-biitylbenzoic acid up to about 1.5 percent by weight and the zinc salt of di-tert-butylbenzoic acid up to about 2 percent by weight. The zinc salt of p-chlorobenzoic acid and the zinc salt of p-bromobenzoic acid dissolve in the oil mentioned up to about 0.5 percent by weight. The copper, manganese and lead salts of p-tert-butylbenzoic acid dissolve in the mentioned lubricating oil distillate up to about ι and 0.9 and 0.7 percent by weight, respectively. The compounds to be added usually have to be dissolved in the lubricants at an elevated temperature, the first example at temperatures between 150 and 300 ⁰ since the release at normal temperature is often carried heavy. However, once the substances have been dissolved at an elevated temperature, the solutions thus obtained remain stable even at normal temperature.

An effective lubricant is e.g. B. obtained by adding about 0.80 / 0 of the zinc salt the p-tert-butylbenzoic acid in lubricating oil, e.g. B. a lubricating oil distillate treated with furfural, dissolves at a temperature of about 2S0 ".

Very good results are also achieved with a lubricating oil in which 1 percent by weight the calcium or zinc salt of diisopropylsalicylic acid at a temperature is resolved by about 180 ".

Other examples of salts added to lubricants in accordance with the invention can are the zinc, magnesium, calcium UHd Aluminum salts of thymotinic acid, the isomeric methylisopropylsalicylic acids, the Isopropylthymotinic acid, tertiary butyl cresotinic acid, tertiary octyl cresotinic acid, tertiary octylsalicylic acid or oxyphenyl cresotinic acid.

If the aforementioned salts are used in small amounts, e.g. B. 1 weight percent, in lubricating oils which, without the additives, cause severe seizure when used the rings and / or excessive sludge formation in combustion engines the seizure of the rings and the formation of sludge are significantly delayed greatly reduced. In addition, those added with the salts mentioned have an effect Lubricating oils are non-corrosive to modern bearing metals, while the oxidizing ioo Resistance, measured according to the Indiana oxidation test or according to other known ones Laboratory test methods, is considerably improved.

The substituted aromatic carboxylic acids can according to the in the relevant Technique known methods are produced. For example, the alkylated Oxy acids are produced by carboxylating the corresponding mono- or no Polyphenols or mixtures containing these substances, e.g. B. of phenol fractions, obtained from coal tar, or from mixtures of phenols obtained from refining Mineral oil fractions arise, or by alkylating the oxy acids.

So can the diisopropylsalicylic acid like can be produced as follows:

104 g salicylic acid and 150 g isopropyl alcohol will be Jaa in the course of a quarter of an hour with stirring and heating to 90 to 95 ° to 1700g- 800 / o sulfuric acid.

sets, whereupon the reaction mixture is stirred for a further IS hours on the same Temperature is maintained. After cooling, the 3 · 5-diisopropylsalicylic acid formed crystallizes the end. This is filtered off, washed a few times with water and in an approximately 250% excess of one 100% lye added; the resulting solution of the sodium salt is five times with

to pentane shaken out. The mixture is then acidified, and the practically pure 3 × 5-diisopropylsalicylic acid which then crystallizes out is filtered off and dried. The yield is 68o / _o of theory, calculated on the salicylic acid. The acid obtained can be converted into the form of the salts of polyvalent metals in various ways, for example via the sodium salt with CaCl ₂ into the calcium salt or directly with ZnO into the zinc salt.

Claims (4)

Patent claims: 1. Lubricants, especially for lubricating internal combustion engines, consisting of a lubricant known per se, such as mineral Lubricating oil, and a small amount of a soluble polyvalent metal salt and an optionally substituted aromatic monocarboxylic acid. 2. Lubricant according to claim 1, characterized in that it is a basic Contains salt from the components specified in claim 1. 3. Lubricant according to claim 1 and 2, characterized in that it is the zinc salt which contains p-tert-butylbenzoic acid. 4. Lubricant according to claim 1 and 2, characterized in that it is the zinc or contains the calcium salt of diisopropylsalicylic acid.