EP0658182B1 - Amine-free cooling lubricants - Google Patents

Abstract

Amine-free cooling lubricants contain as essential component sets of anticorrosive substances, besides the usual base oils, emulsifiers and solubilizers. These sets of anticorrosive substances consist of a mixture of dimeric fatty acids and one or several carboxylic acids. The latter are selected among the apliphatic and aromatic carboxylic acids. Alkali metal, magnesium and/or calcium salts of said acids may be used in a similar manner. These amine-free cooling lubricants have an anticorrosive effect comparable to that of alkanolamine-containing cooling lubricants.

Description

The invention relates to amine-free cooling lubricants for metalworking, containing base oils, emulsifiers, solubilizers and corrosion protection additives.

Cooling lubricants are preparations / mixtures that are used in metal cutting and metal forming to cool and lubricate the workpieces. The most important machining processes, which differ in the type of movements that the machined part and tool perform and in the geometry of the parts to be manufactured, are referred to as milling, turning, drilling and grinding as machining operations, as well as rolling, deep drawing and cold extrusion as non-cutting deformations .

The common principle of metal-cutting processes is that the cutting edge engages in the material, lifting a chip off the surface and creating a new surface. Very high pressures are required to break up the material. The deformation of the chip and the friction that occurs under pressure generate heat that heats up the workpiece, the tool and, above all, the chips.

The desired effect of using cooling lubricants is therefore the lowering of the temperature that would otherwise occur in the chips. B. could rise to 1000 ° C, and which has an impact on the dimensional accuracy of the manufactured parts. Another main task of cooling lubricants is to increase the tool life improve that wear out quickly under the influence of high temperature. The use of a cooling lubricant reduces the roughness of the surfaces, since the lubricant prevents welding of the tool and workpiece surface and prevents particles from sticking. In addition, the cooling lubricant takes on the task of removing the chips that have formed. This is particularly important for mass production.

Cooling lubricants are normally used in the circulation process, i. H. In the simplest case, the use of cooling lubricants on a single machine, the machine has a container for the cooling lubricant.

With the new version of DIN 51385 No. 1, a clear designation of the cooling lubricants was created, whereby we speak of non-water-miscible, water-miscible and water-mixed cooling lubricants. According to DIN 51385, the terms "water-mixed" mean the final state of the finished medium (mostly as oil-in-water emulsions), but "water-miscible" means the state of the concentrate.

Water-mixed cooling lubricants are produced by the user by mixing a concentrate, the water-miscible cooling lubricant, with process water. As a rule, approximately 5% aqueous emulsions are produced. The advantage of this type of cooling lubricant is the good cooling effect, which is based on the thermal properties of the water. Due to the good cooling effect, it is possible to achieve very high working speeds and thus increase the productivity of machines. The lubricating effect of the water-mixed cooling lubricants is sufficient for most machining processes in metal-cutting manufacturing. Another benefit is the low cost of mixing the concentrate can be achieved with water. The disadvantage of water-mixed cooling lubricants is that they are sensitive to attack by microorganisms and therefore require more control and care. The presence of water can lead to rust formation and can attack sensitive metals. Water-mixed cooling lubricants are used today for almost all types of machining. In addition to the requirement for rust protection for the machines and for machined parts made of iron alloys, it is also required that non-ferrous metals are not attacked. The cooling lubricants must be well tolerated by the skin, since the machine operators often come into direct contact with the liquid. When the cooling lubricant is circulated, there should be no disruptive foam, and the painting and the seals of the machine must not be attacked. Emulsion stability, which influences almost all other properties of the cooling lubricant, is of particular importance, at least after a long period of use. It is also required that residues of the cooling lubricant do not stick to the machine, that the cooling lubricants can be easily mixed with water, that the smell and appearance are pleasant and that the usual filter devices are not impaired by the cooling lubricant.

• Kühl- und Schmierwirkung
• Rostschutz
• kein Angriff auf NE-Metalle
• toxikologische Unbedenklichkeit insbesondere Hautverträglichkeit
• keine Schaumbildung
• kein Angriff auf Lacke und Dichtungen
• Emulsionsstabilität
• keine Verklebung oder Verharzung
• gute Mischbarkeit
• angenehmer Geruch
• sauberes Aussehen
• gute Filtrierbarkeit
• problemlose Entsorgung.

The table shows a summary of the requirements for water-miscible and water-mixed cooling lubricants:

• Cooling and lubricating effect
• Anti-rust
• no attack on non-ferrous metals
• toxicological harmlessness, especially skin tolerance
• no foaming
• no attack on paints and seals
• Emulsion stability
• no sticking or resinification
• good miscibility
• pleasant smell
• clean look
• good filterability
• easy disposal.

The requirements for the rust protection effect of cooling lubricants are particularly high, since after processing with cooling lubricants, drying is generally not possible. The parts are usually placed wet in boxes and should not rust even when wet. To test the rust protection effect, the test with cast chips according to DIN 51360/2 is often used in the development and also in the control of solutions in practical use.

The rust protection effect of the cooling lubricants is influenced by a number of factors. So the quality of the water used for the mixture has a great influence. The water hardness, but above all chlorides and sulfates, worsen the rust protection effect of the solution. To make matters worse when cooling lubricants are used for a long time, the concentration of the salts rises constantly, since parts of the emulsion evaporate and the losses are replenished with saline water.

Non-water-miscible and water-miscible cooling lubricants, insofar as they are emulsions in use, are often based on mineral oil. The mineral oil qualities used are predominantly combinations of paraffinic, naphthenic and aromatic hydrocarbon compounds. In addition to mineral oils, so-called synthetic lubricants ("synthetic oils") such as Polyolefins, polyalkylene glycols and glycol ethers, natural ester oils and synthetic esters and their derivatives.

In order to meet practical requirements, the water-miscible cooling lubricants must contain various components in addition to the base oil. The most important substance groups are the emulsifiers, anti-corrosion additives, biocides, EP additives, polar additives, anti-fog additives, anti-aging agents, solid lubricant additives and defoamers.

Emulsifiers (e.g. surfactants, petroleum sulfonates, alkali soaps, alkanolamine soaps) stabilize the fine distribution of oil droplets in the aqueous working fluid, which is an oil-in-water emulsion. In terms of quantity, the emulsifiers represent an important group of additives for water-miscible cooling lubricants.

Common anti-corrosion additives (e.g. alkanolamines and their salts, sulfonates, organic boron compounds, fatty acid amides, aminodicarboxylic acids, phosphoric acid esters, thiophosphonic acid esters, dialkyldithiophosphates, mono- and dialkylarylsulfonates, benzotriazoles, polyisobutene succinic acid derivatives) are intended to prevent rusting of metal surfaces. In the past, nitrite was often used as a corrosion protection agent, but today it is frowned upon because of its toxicity and environmental damage, especially because of the risk of carcinogenic nitrosamines. Some corrosion protection additives also have emulsifying properties and are therefore also used as emulsifiers. Biocides (e.g. phenol derivatives, formaldehyde derivatives, Kathon MW) are intended to prevent the growth of bacteria and fungi. EP additives (e.g. sulfurized fats and oils, compounds containing phosphorus, organochlorine compounds) are intended to prevent micro-welding between metal surfaces at high pressures and temperatures. Polar additives (e.g. natural fats and oils, synthetic esters) increase the lubrication properties. Anti-aging agents (e.g. organic sulfides, zinc dithiophosphates, aromatic amines) ensure a long service life of the cooling lubricants.

The alkanolamines and alkanolamine derivatives, which are used in a large number of water-miscible cooling lubricants as corrosion protection additives, occupy a central position among the additives. In addition, in conjunction with carboxylic acids, their good buffer capacity guarantees that the aqueous use emulsions have a certain pH constant. The constancy of pH is of particular importance with regard to emulsion stability and rust protection. Reaction products of alkanolamines with boric acid have a growth-inhibiting effect on bacteria and mold and therefore improve the service life of cooling lubricants.

A disadvantage of the alkanolamines and alkanolamine derivatives is that they are used in practice with nitrosating substances, e.g. B. bacterially formed nitrite or nitrogen oxides in the air, can react and be converted into nitrosamines. For example, nitrosodiethanolamine (NDELA) can be formed in water-mixed cooling lubricants that contain ethanolamines.

Animal experiments have shown that nitrosamines can cause cancer in various organs (e.g. stomach, lungs, bladder, liver, esophagus). Therefore some nitrosamines, e.g. B. also NDELA, classified in the German Hazardous Substances Ordinance as carcinogenic. To avoid health hazards for the operators of metalworking machines, the formation of nitrosamines must therefore be avoided.

The object of the present invention is to provide amine-free cooling lubricants which, however, are not inferior to the previously usual amine-containing cooling lubricants with regard to the rust protection effect in terms of stability and duration of use and other usage properties.

• a) Dimerfettsäuren und
• b) einer oder mehreren Carbonsäuren ausgewählt aus aliphatischen Carbonsäuren mit 6 bis 14 C-Atomen und aromatischen Monocarbonsäuren oder den Alkalimetall-, Magnesium- und/oder Calciumsalzen der unter
• a) und/oder b) genannten Säuren enthalten ist.

The above-mentioned object is achieved by amine-free cooling lubricants containing base oils, emulsifiers, solubilizers and corrosion protection additives, characterized in that a mixture of corrosion protection additives

• a) Dimer fatty acids and
• b) one or more carboxylic acids selected from aliphatic carboxylic acids having 6 to 14 carbon atoms and aromatic monocarboxylic acids or the alkali metal, magnesium and / or calcium salts of the
• a) and / or b) acids mentioned.

Surprisingly, it was found that the combination of dimer fatty acid and other carboxylic acids, selected from aliphatic and aromatic carboxylic acids or their alkali metal, magnesium and / or calcium salts, is suitable for providing cooling lubricants which, in relation to the corrosion protection effect compared to commercially available cooling lubricants have comparable corrosion protection effects based on alkanolamines.

The selection of the base oils according to the invention in the cooling lubricants is practically not limited. For the purposes of the present invention, emulsions often contain components which are selected from paraffinic, naphthenic and paraffinic-naphthenic mineral oils. In the same way, the use of ester oils, e.g. B. trimethylolpropane esters, neopentyl or pentaerythritol esters, of fatty oil derivatives, polyisobutylenes, Hydrogenated polydecenes, polypropylene glycol, silicate esters, carbonic acid esters, esters of acids containing phosphorus, chain-like diphenyl ethers and phenoxyphenyl ethers are preferred.

The cooling lubricants according to the invention contain emulsifiers known per se in the prior art, in particular those selected from a) anionic emulsifiers, in particular soaps, sulfonates and phosphoric esters and their salts, and b) nonionic emulsifiers, in particular fatty alcohol ethoxylates, fatty alcohol propoxylates and sugar esters.

In addition to base oils, emulsifiers and the corrosion protection additives according to the invention, cooling lubricants in the sense of the present invention also contain solubilizers. For the purposes of the present invention, water can also be regarded as a solubilizer. Accordingly, in a preferred embodiment of the present invention, the solubilizers are selected from water, alcohols, glycols and glycol ethers. In a particularly preferred manner, the solubilizers are used in an amount of 1 to 30% by weight, in particular 2 to 10% by weight, based on the water-miscible cooling lubricant.

In the context of the present invention, cooling lubricants contain, as an essential constituent, one or more carboxylic acids which are selected from aliphatic carboxylic acids and aromatic carboxylic acids. Particularly preferred aliphatic carboxylic acids are selected from adipic acid, caprylic acid, sebacic acid, 2,2,4-trimethylhexanoic acid and ethylhexanoic acid. In the same way, particularly preferred aromatic carboxylic acids are selected from benzoic acid, substituted benzoic acids and especially salicylic acid. Possible substituents for benzoic acid can be a hydroxyl group, a nitro group, and straight-chain or branched alkyl or Alkyloxy groups with up to 4 carbon atoms. Short chain carboxylic acids are known as components of water-soluble anti-corrosion agents, e.g. B. from DE 32 23 940, but not as components of emulsions in the combination according to the invention with dimer fatty acids, emulsifiers, base oils etc.

Another essential constituent of the cooling lubricants according to the invention are dimer fatty acids, which can preferably be contained in an amount of 2 to 20% by weight, in particular 5 to 15% by weight, based on the water-miscible cooling lubricants. Usually, dimer fatty acids are understood to mean mixtures of acyclic and cyclic dicarboxylic acids with an average of 36 carbon atoms obtained by alumina-catalyzed dimerization of unsaturated fatty acids (literature reference: Dimer Acids, EC Leonard, 1975, Humeo Sheffield). By-products of the dimerization are branched C-18 fatty acids and trimer fatty acids or polyhasic fatty acids, which are often separated off by distillation. For the purposes of the present invention, however, dimer fatty acids can also be used which contain monomeric acid, trimer fatty acid and polymeric fatty acid as secondary constituents. Z can be used well. B. Empol ^R 1022, Emery, USA or Pripol ^R 1040 or Pripol ^R 1013 from Unichema, Emmerich.

The structure of the dicarboxylic acids used according to the invention differs significantly from the dicarboxylic acids or dicarboxylic acid anhydrides mentioned in WO 90/15663, which are prepared by reacting olefins with unsaturated carboxylic acids or their anhydrides.

The water-miscible or water-mixed cooling lubricants according to the invention can contain further functional additives such as polar additives, EP additives, anti-fog additives, anti-aging substances, Contain solid lubricants, pigments, defoamers and / or biocides. For use in metalworking, the aqueous emulsions or aqueous solutions of the cooling lubricants according to the invention preferably contain 1 to 10% by weight, in particular 2 to 5% by weight, of the water-miscible concentrate.

The pH of the cooling lubricants is usually set in the range from about 7 to 10. An adjustment of the pH value range from 8 to 9.5 is particularly preferred. For the purposes of the present invention, it is also particularly preferred to adjust the alkaline pH using alkali metal hydroxide. The use of magnesium or calcium hydroxide is less preferred because poorly soluble salts could possibly be formed. Accordingly, the use of potassium and / or sodium hydroxide is particularly preferred for the purposes of the present invention.

Examples

1/3 of the required amount of mineral oil, solubilizer and tall oil fatty acid were placed in the reactor and stirred. The aromatic carboxylic acid (only in Examples 1 and 3) was then added and the mixture was stirred for about 15 minutes.
With constant stirring, the aqueous potassium hydroxide solution was carefully metered in over 30 minutes (exothermic reaction). The temperature of the solution was kept between 50-70 ° C. The mixture was stirred vigorously for 1 hour until a clear brown solution was obtained. The remaining amount (2/3) of mineral oil was then added.
The remaining components:
Petroleum sulfonate (only in recipe example 1), dimer fatty acid, caprylic acid (only in recipe examples 1 and 2) and the fatty alcohol ethoxylates were then metered in in the above order. The mixture was stirred for about 1 hour until a brown, clear solution was obtained.

Tables 1 and 2 below give examples of formulations of cooling lubricants according to the invention (Table 1) and not according to the invention (Table 2). Table 1 example 1 Example 2 Example 3 Mineral oil (naphthenic solvent raffinate) 33.3% 44.0% 35.5% Solubilizer (glycol base) 11.7% 5.2% 10.0% long chain fatty acid (tall oil fatty acid) 12.5% 9.0% 14.0% Petroleum sulfonate 4.2% - - short chain fatty acid (caprylic acid) 4.2% 4.0% - Fatty alcohol ethoxylates (oleyl alcohol + 5 EO) 7.2% 15.5% 9.2% Dimer fatty acid (Empol ^R 1022) 8.3% 13.2% 16.0% aromatic carboxylic acid (salicylic acid *, benzoic acid **) 4.2% * - 4.3% ** aqueous potassium hydroxide solution (45% by weight) 14.4% 9.1% 11.0% 100.0% 100.0% 100.0% Comparative Example 1 Comparative Example 2 Mineral oil (naphthenic solvent raffinate) 40.0% 60.0% Solubilizer (glycol base) 3.0% 5.0% long chain fatty acid (tall oil fatty acid) 6.0% 12.5% Petroleum sulfonate - 4.0% short chain fatty acid (Capryl * - or isononanoic acid) - 3.0% Fatty alcohol ethoxylate (oleyl alcohol + 5 EO) 8.0% - Fatty acid ester (ethylhexyl oleate) - 4.5% Fatty acid amide (tall oil fatty acid diethanolamide) 7.0% 6.0% aqueous potassium hydroxide solution (45% by weight) 3.0% 5.0% Diethanolamine 17.0% - Boric acid 5.0% - condensation 11.0% - 100.0% 100.0%

Preparation of Comparative Example 1

Condensed water and diethanolamine were introduced and boric acid was dissolved in with stirring. The mineral oil and all other components were then added in the order given in Table 2 and stirred until a clear, homogeneous concentrate was formed.

Preparation of Comparative Example 2

The mixture was mixed and stirred in the order given in Table 2 until a clear, homogeneous concentrate was formed.

Table 3 below shows a comparison of the formulations according to the invention with the examples not according to the invention with regard to corrosion protection (test according to DIN 51360/2). Table 3 example 1 2nd 3rd See 1 See 2 Appearance Texture of the 5% emulsion finely dispersed, firmly transparent finely dispersed semi-transparent roughly dispersed milky finely dispersed, semi-transparent coarsely dispersed, milky Degree of corrosion 0 from .... 4.0% 4.0% 5.0% 3.0% 7.0% at pH .. 8.9 9.4 9.6 9.4 9.2 According to DIN 51360/2, the corrosion protection effect of water-mixed cooling lubricants is tested by wetting castings on filter paper with the cooling lubricant. After two hours, the corrosion marks on the filter paper are evaluated according to a comparison scale, where degree of corrosion 0 means that no corrosion was observed.

The minimum concentration required to achieve degree of corrosion 0 was given for the examples.

Claims (13)

1. Amine-free cooling lubricants containing base oils, emulsifiers and solubilizers, characterized in that a mixture of

   a) dimer fatty acids and

   b) one or more carboxylic acids selected from aliphatic carboxylic acids containing 6 to 14 carbon atoms and aromatic monocarboxylic acids or
   the alkali metal, magnesium and/or calcium salts of the acids mentioned under a) and/or b) is present as the corrosion-inhibiting additive.
2. Cooling lubricants as claimed in claim 1, characterized in that the base oil is selected from paraffinic, naphthenic or paraffinic/naphthenic mineral oils, ester oils, for example trimethylol propane esters, neopentyl or pentaerythritol esters, from fatty oil derivatives, polyisobutylenes, hydrogenated polydecenes, polypropylene glycol, silicate esters, carbonic acid esters, esters of phosphorus-containing acids, chain-like diphenyl ethers and phenoxyphenyl ethers.
3. Cooling lubricants as claimed in claim 1 or 2, characterized in that the emulsifiers are selected from

   a) anionic emulsifiers, more particularly soaps, sulfonates, phosphoric acid esters and salts thereof and

   b) nonionic emulsifiers, more particularly fatty alcohol ethoxylates, fatty alcohol propoxylates and sugar esters.
4. Cooling lubricants as claimed in one or more of claims 1 to 3, characterized in that the solubilizers are selected from water, alcohols, glycols and/or glycol ethers.
5. Cooling lubricants as claimed in claim 4, characterized in that the solubilizer is used in quantities of 1 to 30% by weight and, more particularly, 2 to 10% by weight, based on the water-miscible cooling lubricant.
6. Cooling lubricants as claimed in one or more of claims 1 to 5, characterized in that the dimer fatty acids are used in quantities of 2 to 20% by weight and, more particularly, 5 to 15% by weight, based on the water-miscible cooling lubricants.
7. Cooling lubricants as claimed in one or more of claims 1 to 6, characterized in that the aliphatic carboxylic acids are selected from adipic acid, caprylic acid, sebacic acid, 2,2,4-trimethyl hexanoic acid and ethyl hexanoic acid.
8. Cooling lubricants as claimed in one or more of claims 1 to 6, characterized in that the aromatic carboxylic acids are selected from benzoic acid, substituted benzoic acids, the substituents being a hydroxy group, a nitro group or linear or branched alkyl or alkyloxy groups, and in particular salicylic acid.
9. Cooling lubricants as claimed in one or more of claims 1 to 8, characterized in that the aliphatic and/or aromatic carboxylic acids are used in quantities of 1 to 20% by weight and, more particularly, 3 to 10% by weight, based on the cooling lubricant.
10. Cooling lubricants as claimed in one or more of claims 1 to 9 additionally containing polar additives, EP additives, anti-mist additives, antiagers, solid lubricants, pigments, foam inhibitors and/or biocides.
11. Water-miscible cooling lubricants as claimed in one or more of claims 1 to 10 in the form of concentrates.
12. Water-mixed cooling lubricants as claimed in one or more of claims 1 to 10 in the form of aqueous emulsions or solutions.
13. The use of the cooling lubricants claimed in one or more of claims 1 to 12 in the form of aqueous solutions or emulsions containing 1 to 10% by weight and, more particularly, 2 to 5% by weight of the water-miscible coaling lubricant concentrates for the machining of metals.