SK279338B6 - Usable high-pressure lubricant, especially for high-pressure compressors - Google Patents

Abstract

A lubricant is a mixture comprising 40-60 percent by weight of white oil and/or 60-40 percent by weight of polybutene and/or polyisobutene, at least two usable lubricating power-improving additives being composed of by esters saturated fat acids and high-molecular-weight alcohol groups, whereof the overall content of the said additives is 0.1-3.0 percent by weight. At least one of the additives is composed of such ester with at least one free alcohol group. Unsaturated castor oil is a possible additive as well. The lubricant contains 0.05-0.1 percent by weight of at least one antioxidant agent, i.e. usable anisole derivative and/or usable derivative of a pentaerythritol ester and fat acid ester in an overall amount ranging from 0.05 to 0.1 percent by weight. The lubricant further contains a metal-binding deactivator, e.g. a succinimide derivative or amino acid derivative, e.g. N-acyl-sarcosan, in an overall content ranging from 0.005 to 0.5 percent by weight.

Description

Technical field

The invention relates to an edible lubricant which can be used in particular for high pressure compressors. As is known, such an edible or edible, and thus practically non-toxic, lubricant is necessary to lubricate machine parts, of which certain proportions, mostly only trace amounts of lubricant, can be directly or indirectly introduced into the foodstuffs and foods. However, such practically non-toxic lubricants have the advantage that they are only marginally harmful to the environment, as compared to previously known lubricants, which often contain poisonous substances. Edible substances are either:

(a) non - toxic and digestible, such as vegetable and animal fats and oils; or

(b) non-toxic as they are insoluble and chemically inert, such as liquid paraffin, and leave the organism in undigested form.

The invention relates to a lubricant consisting of a mixture consisting predominantly of a component of group b) in the form of a base lubricant mixture (base or base of a lubricant), as well as of edible substances of group a) in the form of additives.

This lubricant is particularly suitable for high-pressure compressors which are used to produce polyolefins (high-pressure polyethylene and high-pressure polypropylene) from the corresponding gaseous monomers, these high-pressure compressors operating at pressures from 150 to mostly 350 MPa. The films obtained from the high-pressure polyethylene or high-pressure polypropylene thus produced are also used for food packaging. The trace amounts of lubricant that may be contained in these films may then partially pass into the foodstuffs when in contact with the foodstuffs packaged in such films. It is therefore essential that the lubricants used are edible.

BACKGROUND OF THE INVENTION

Edible lubricants of this type and for this purpose are known. DE-PS 2137590 discloses such a lubricant. It consists of white mineral oil and 5 to 50% by weight, preferably 20 to 40% by weight of polybutene and 0.1 to 1.0% by weight, preferably 0.1 to 0.5% by weight. % of a fatty acid having 16 to 18 carbon atoms and / or a lower alkyl ester of such a fatty acid; an antioxidant (o-tert-alkyl-substituted phenol). The fatty acids or their lower alkyl esters, which are used in the lubricant described in DE-PS 2137590 as an additive for lubricity, consist of saturated or unsaturated aliphatic monocarboxylic fatty acids having 8 to 22 carbon atoms, as well as many lower alkyl esters, these alkyl esters contain up to about 5 carbon atoms and are, for example, methyl oleate, n-butyl stearate and the like esters.

lubricant formulations can lead to a significant deterioration in its quality. For this reason, the inventions of the present invention are mainly based on the fact that it has been necessary to investigate a very large number of different ingredients, always in numerous combinations, mix ratios and concentrations.

The lubricant according to the invention differs substantially from that described in DE-PS 2137590 in that it does not contain any free fatty acids which, as is known, can lead to corrosion of the compressor components; the lubricant of the invention also contains no lower alkyl esters of fatty acids. Also, this lubricant is not composed of unsaturated fatty acids or lower alkyl esters thereof, such as oleic acid, linoleic acid or linolenic acid and their lower alkyl esters, whose chemical and thermal stability is not shown to be optimal.

The lubricant according to the invention, on the other hand, contains, as an additive to lubricity, only saturated fatty acid derivatives in which there is no free acid group (carboxyl group COOH) and no unprotected double or multiple bond; moreover, the lubricant according to the invention is not an ester of a monohydric alcohol, but solely an ester of a higher edible alcohol. These higher edible alcohols include, for example, propylene glycol glycerin erythritol pentaerythritol hexite mannitol, sorbitol and arabite.

(2 alcohol hydroxy groups), (3 alcohol hydroxy groups), (4 alcohol hydroxy groups, carbon atoms), (4 alcohol hydroxy groups, carbon atoms), (6 alcohol hydroxy groups),

The exception is castor oil (triglyceride), which contains ricinoleic acid (hydroxyoleic acid); this acid is not readily oxidizable and is not prone to thermal instability like oleic acid because it is protected by the (cloning) hydroxyl group it contains. In contrast to oleic acid and its esters, castor oil is chemically and thermally stable.

It goes without saying that the chemical and thermal stability of the additives used is crucial for the quality of the lubricant.

The lubricant according to the invention preferably contains more than one additive in the form of edible esters, in particular at least one additive in the form of an ester of saturated fatty acids with a 2-, 3-, 4- and 6-saturated alcohol, preferably each constituting one component of castor oil.

The content of lubricity enhancing additives in total is 0.1 to 3.0% by weight, based on the total weight of the finished lubricant.

Castor oil contains the following fatty acids:

% to 91 wt.

% wt.

% to 2 wt.

SUMMARY OF THE INVENTION

In particular, the lubricant according to the invention is novel with respect to the ingredients contained and differs substantially from the lubricant described in the aforementioned DE-PS 2137590.

The nature and the amounts of the ingredients involved are crucial for the quality of the lubricant. Even slight deviations from ricinoleic acid, stearic acid and palmitic acid, dihydroxystearic acid, but also up to 3 wt.

% to 5 wt.

oleic acid and linoleic acid.

Since the latter two components are unsaturated acids, the addition of an antioxidant or antioxidants to the lubricant with an ob2

2796 castor oil content. The hardened (hydrogenated) castor oil is a hardened fat having similar properties to wax and melting in the temperature range of 84 to 86 ^° C.

Said additives are better dissolved in the mineral lubricant base when the mixture of the lubricant base and additives is heated, especially to a temperature that is higher than the melting point of the highest melting additive. Thus, the practical limitation of the applicability of the additive to the lubricant of the present invention is that the melting point of such an additive is too high, or the heating of the lubricant base / additive mixture to a temperature greater than 100 ° C is lengthy and unfavorable.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

As an example of the lubricant enhancement formula, the following mixture is comprised of five such different ingredients:

table

Additive (name) Esterz Content in finished grease (% by weight _r alcohol: fatty acid castor glycerin ridnolejová 0.05-0.5 oil microcapsules kysoina Pentaerytrtt ponta- kyaafina stoarová OJ »-0.6 sslor erythritol apaknlová Etylhexyt- ethylhexyl * · palmitic acid 0.03 · 0.3 paimittt alcohol Etylbexyt- ethylhexyl st 0.03-0.3 stearate Alcohol sorbitan · SORM staaric acid 0.03 -0a triatearát

The lubricant oil base mixture (lubricant base) always consists of about 40 to 60% by weight of a white oil and about 60 to 40% of polybutene and / or polyisobutene. As an antioxidant (anti-aging additive), the lubricant according to the invention contains 0.05 to 0.1 wt. % anisole compound or 0.05 to 0.1 wt. % of a mixture of the two compounds in a ratio of about 1: 1, preferably 0.01-1.1 wt. organic phosphite compound.

The lubricant according to the invention with ester-based additives has the following advantages:

1. The choice of edible saturated fatty acids in the acid residue of the esters provides optimum thermal and chemical stability as well as improved lubricity and reduced abrasion of the lubricated components.

2. The same is achieved by selecting edible higher alcohols with 2 to 6 alcohol groups (hydroxyl groups) for the alcohol residue of the esters.

3. The preferred choice of more, but at least two components, preferably one of which should always be castor oil or hardened castor oil, results in optimum lubricant behavior over a wide range of temperatures, pressures and residence times in the lubricated compressor as well as optimal mechanical parameters (including relative speed of driven parts to lubricated parts, their material composition, friction coefficients and other properties).

4. The content of lubricant additives is a total of 0.1 to 3.0% by weight. irrespective of the number of components of the lubricant additive, so that increasing the number of these components will not significantly increase the price of the lubricant.

5. Appropriate targeted selection of esters in the function of lubricant additives can achieve the desired physical and chemical properties, such as low melting point (freezing point), high boiling point and high flash point, and low vapor pressure of the lubricant of the invention; polyhydric alcohols allow the formation of esters with 1 to 2 6-saturated alcohols with up to 6 alcohol groups, while the free non-esterified alcohol groups provide some desirable properties such as low melting point, good solubility in the mineral oil base of the lubricant and high viscosity at elevated temperature .

6. The free acids which are possibly formed as additive degradation products (only in trace amounts), for example by oxidation of an alcohol hydroxyl group, can lead to the formation of neutral reactive edible esters with the other free alcohol groups; this ester formation is promoted by the fact that the esterification water produced is removed from the lubricant by evaporation under the high temperature prevailing in the lubricant, thereby favoring a shift in chemical equilibrium in favor of ester formation (equilibrium constants, active mass act). Thus, free, non-esterified alcohol hydroxyl groups can provide aging protection to the lubricant by acid binding.

7. Chemically substantially stable esters of higher saturated fatty acids undergo partial oxidation at higher temperatures and prolonged residence in compressors, degrading at the carbon atom in the beta position, so that the oxidation product is always the nearest lower fatty acid; for example, stearate also produces a lubricant-active palmitate and the like. These fatty acid esters therefore constitute intrinsic, built-in anti-aging protection and thus act similarly to antioxidants.

8. As the lubricant additives according to the invention may contain free alcohol groups in the ester, it is thus possible to eliminate the addition of alcohols, for example fatty alcohols, which do not always have the desired properties and which are often inedible.

9. Compared to the known alternative formation of esters of polybasic acids, such as adipic acid and fruit acids, the lubricant additives according to the invention have the advantage that, when partially esterified, neutral alcohol groups remain, whereas after partial esterification of polyhydric acids, free acid acids remain. groups that are undesirable due to the risk of corrosion. Said lubricant further comprises a metal-binding deactivator in an amount of 0.005 to 0.5% by weight, based on the weight of the finished lubricant composition, in the form of succinimide derivatives or amino acid derivatives, for example N-acyl sarcosan.

Example 2

As a second example, this time concerning a mixture of only two lubricity enhancing ingredients, the following recipe can be mentioned:

Ingredient (name) Eslerz alkohol: fatty acid Content in finished grease (% by weight) castor glycerin riclnolejové 0.12 to 1.25 oiej acid Sofbitantmte- «orbits stearová kywllra 0.0 - - 0.75 and count Pretty 0.2 · 2.0

The lubricant according to the invention may optionally additionally contain, as an additive solvent and / or as an additive dissolution agent, one of the consumable higher alcohols.

Comparative examples

Various edible mixtures with the following basic composition were mixed from edible lubricants:

% wt. % paraffin oil with a viscosity at 40 ° C of 3.5 cSt (Technol 252 D) wt. a masterbatch made of a 'blend component consisting of:

% wt. % polybutene wt. % of liquid paraffin 68 to which was subsequently added: 1.0 wt. Irgalube 349 (Additive)

0.5 wt. Sarosyl (N-Acyl-sarcosine)

1.0 wt. Irganox (antioxidant) and 9 parts liquid paraffin 68.

The remaining 3 wt. lubricants consist of one (prior art) or more (according to the invention) fatty acid esters.

In the produced lubricants, the drag coefficient tan a was measured by means of a test apparatus. The lower the drag coefficient, the better the lubricating effect of the lubricant.

Comparative Example 1

% 1 wt. % paraffin oil; % of said base mixture wt. sorbitan monostearate as an additive

The following towing coefficients were measured:

pokus 1_______pokus 2_______

0.24 0.24

Comparative Example 2

% 2 wt. % paraffin oil; % of said base mixture wt. sorbitan tristearate as an additive

The following towing coefficients were measured:

pokus 1__________pkus 2_______

0.23 0.23

Comparative Example 3 A 3 wt. % paraffin oil; of said base mixture

1.5 wt. sorbitan monostearate as an additive

1.5 wt. sorbitantristearat

The following towing coefficients were measured:

pokus 1__________pkus 2_______

0.21 0.22

A comparison of mixture 1 or mixture 2 with mixture 3 shows that mixture 3 (which contains 2 fatty acid esters according to the invention) has a better drag coefficient than mixture 1 or 2 (which consist of only one fatty acid ester contained in the mixture). mixtures 3). Thus, it is shown that the composition according to the invention with at least two fatty acid esters as additives has surprisingly better lubricating effects than those known in the art.

Claims (7)

PATENT CLAIMS An edible high-pressure lubricant, in particular for high-pressure compressors, consisting of a lubricant base consisting of 40 to 60 wt. % polybutene and / or polyisobutene and 60 to 40 wt. white oil and at least two lubricity enhancing additives and at least one antioxidant and at least one metal-binding deactivator, characterized in that the lubricity enhancing additives consist of at least two esters of edible alcohols with at least two hydroxyl groups, which are each esterified with at least one higher saturated fatty acid, wherein the total content of lubricity enhancing additives is 0.1 to 3.0% by weight, based on the total weight of the finished lubricant. A edible high-pressure lubricant according to claim 1, wherein the at least one lubricity enhancing additive is an ester with at least one free hydroxyl group. The edible high-pressure lubricant according to claims 1 and 2, characterized in that the edible fatty acid residues in the esters are saturated and that additionally unsaturated castor oil, ricinoleic acid triglyceride and unsaturated hydroxyoleic acid can also be used as an additive. The edible high-pressure lubricant according to claims 1 to 3, characterized in that the edible alcohol-consumable lubricating esters are preferably propylene glycol, glycerin, erythrit, pentaerythrit, arabite and hexites (mannitol, sorbitol), as well as edible alcohol derivatives thereof. The edible high-pressure lubricant according to claim 1, characterized in that it comprises 0.05 to 0.1% by weight, based on the total weight of the finished lubricant mixture, of at least one known antioxidant, consisting of an edible anisole derivative and / or an edible derivative. % pentaerythritol fatty acid ester with a radical-amine-binding hydroxyl group and / or 0.01 to 0.1 wt. organic phosphite compound. The edible high-pressure lubricant according to claim 1, characterized in that it contains as an additive from 0.005 to 0.5% by weight, based on the finished lubricant mixture, of at least one known and inactivable metal-binding deactivator, in particular in the form of succinimide derivative or amino acid derivative, preferably N-acyl-sarcosan. The edible high-pressure lubricant according to claims 1 to 6, characterized in that it contains as an additional additive at least one known edible, thermally and chemically stable higher mono- or polyhydric alcohol as an additive dissolution agent.