DE19634733A1 - Use of bismuth compounds in cooling lubricants - Google Patents

Abstract

The invention concerns a friction-reducing additive for water-miscible or non-water-miscible cooling lubricants which contains: a) bismuth compounds of organic acids; and b) sulphurous organic compounds, in a mixture ratio such that the sulphur content of the additive ranges from 2 to 30 wt % and the bismuth content ranges from 1 to 25 wt %. The invention further concerns the use of this additive in the minimal lubricating technique and as a friction-reducing additive for non-water-miscible cooling lubricants and water-mixed cooling lubricants and their concentrates.

Description

The invention relates to water-immiscible or water-miscible cooling lubricants substances or their concentrates for metal cutting. Against State of the invention is an additive for such cooling lubricants, consisting of a mixture of organic bismuth compounds and organic sulfur compound fertilize.

Cooling lubricants are preparations / mixtures that are used in metal cutting and used in metal forming to cool and lubricate the tools will. The main processing methods, which are characterized by the type of movement the machined part and tool, and the geometry distinguishing the parts to be manufactured is called 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 tool cutting edge engages in the material, thereby removing a chip from the Surface lifts off, so that a new surface is created. For the division of the Very high pressures are required. By the deformation of the chip and The friction that occurs under pressure creates heat that the workpiece, the tool and especially the chips heats up.

The desired effect of using cooling lubricants is therefore the Sen kung the temperature that otherwise in the chips z. B. rise to 1000 ° C  can, and which affects the dimensional accuracy of the manufactured parts. A Another main task of cooling lubricants is to increase the service life of the tools improve that wear out quickly under the influence of high temperature. By Using a cooling lubricant will ver the roughness of the surfaces reduces, since the lubricant welds the tool and workpiece top prevents surface and prevents particles from sticking. Beyond the cooling lubricant takes on the task of removing the chips formed.

With the new version of DIN 51385 No. 1, the Cooling lubricants created, being from water-immiscible, water-mixable and water-mixed cooling lubricants. According to DIN 51385 is the term "water mixed" the final state of the finished medium (mostly as oil-in-water emulsions), but under "water-miscible" the Zu level of the concentrate understood.

Water-mixed cooling lubricants are manufactured by the user through Mi a concentrate of the water-miscible coolant with plant water. As a rule, approximately 5% aqueous emulsions are produced. advantage This type of cooling lubricant is the good cooling effect on the thermal egg properties of water. Due to the good cooling effect, it is very possible to achieve high working speeds and thus the productivity of Ma seem to increase. The lubricating effect of the water-mixed cooling lubricants is sufficient for most machining processes in machining. Another benefit is the low cost of the possible mix of the concentrate can be reached with water. Disadvantage of water-mixed cooling Lubricants is sensitive to attack by microorganisms and therefore require more control and care.

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

• - Cooling and lubricating effects
• - rust protection  
• - 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 appearance
• - good filterability
• - easy disposal.

An overview of the shaping metalworking processes and the corresponding ones Commonly used tools are, for example, Ullmann's Encyclopaedia of Industrial Chemistry, 5th Ed., Vol. A15, 479-486. The spectrum The forms of supply of the aids in question range from oils through oil-in-water emulsions to aqueous solutions.

Non-miscible and water-miscible cooling lubricants are often on Wed. built up mineral oil. The mineral oil qualities used are mostly com combinations of paraffinic, naphthenic and aromatic Koh hydrogen compounds. In addition to mineral oils, they also have synthetic ones Lubricants ("synthetic oils") such as polyalphaolefins, polyalkylene glycols and glycol ethers, dialkyl ethers, natural ester oils as well as synthetic esters and their De derivative meaning.

In order to be able to meet practical requirements, cooling lubricants must be used contain various components in addition to the base oil. The main sub punching groups are the emulsifiers, corrosion protection additives, biocides, EP additives, polar additives, anti fog additives, anti aging agents, solid lubricant additives and Defoamer.  

Emulsifiers (e.g. surfactants, petroleum sulfonates, alkali soaps, alkanolamine soaps) stabilize the fine distribution of oil droplets in the aqueous working fluid speed, which is an oil-in-water emulsion. The emulsifiers make up quantities moderately an important group of additives in the water-miscible cooling lubricants.

Common anti-corrosion additives (e.g. alkanolamines and their salts, sulfonates, or ganic boron compounds, fatty acid amides, aminodicarboxylic acids, phosphoric acid reesters, thiophosphonic acid esters, dialkyldithiophosphates, mono- and dialkylaryl sulfonates, benzotriazoles, polyisobutene succinic acid derivatives) are said to rust Prevent metal surfaces. Some anti-corrosion additives have at the same time emulsifying properties and are therefore also used as emulsifiers dung. Biocides (e.g. phenol derivatives, formaldehyde derivatives, Kathon MW) are supposed to prevent the growth of bacteria and fungi. EP additives (e.g. ge sulfurized fats and oils, phosphorus-containing compounds, organochlorine ver bonds) are said to micro-weld between metal surfaces at high Prevent pressures and temperatures. Polar additives (e.g. natural fats and Oils, synthetic esters) increase the lubrication properties. Protection against aging substances (e.g. organic sulfides, zinc dithiophosphates, aromatic amines) provide a long service life for the cooling lubricants.

In addition to the cooling effect, the second important function of the cooling lubricants is in the lubricating effect (see the article by W. Klose: "Cooling lubricant on Me talloberflächen ", Announcements by the Association of German Email Specialists, 41, Issue 11, Pages 138-142 (1993)). The effect of the lubricating compo is based on this nenten on the formation of surface layers, opposite the basic work have a lower shear strength and thus friction and wear belittle. The spectrum of surface conditions ranges from adsorptive bound layers via chemical sorption to chemical reaction layers, that create a solid bond to the metal surface.

The simplest form of lubricant coating on a surface is adsorptive Lubricant layers. They are, for example, mineral oils without any special  Additives generated. The formation of the adsorption layers can be more polar by additions Active ingredients such as fatty alcohols or fatty esters are strengthened. This occurs over the purely physical adsorption an interaction between the metal surface and the lubricant molecules that lead to a partial chemisorptive Binding of fatty alcohols or fatty esters leads.

Typical representatives of chemisorptive lubricant film formers are fatty acids. The hydrophilic carboxyl group is che by reaction with the metal atoms mix bound to the metal surface and the hydrophobic hydrocarbon residue is aligned perpendicular to the surface. The increased adhesive strength of the chemistry sorptive layer improves the pressure absorption capacity compared to pure ad sorptive layers of lubricant, is sufficient for many cases of metal forming to reduce friction and wear. Here bring Beiengun only of EP or AW additives (extreme pressure or anti wear additives) sufficient improvement of the lubrication performance, so that even difficult forming processes are made possible. These are usually chlorine, phos Active substances containing phosphorus or sulfur. Their effect is based on training of chemical reaction layers in the form of metal chlorides, metal phospha ten or metal sulfides. For disposal reasons, there is now an endeavor to If possible, avoid chlorine-containing EP additives. The on the metal surface reaction layers formed act on the one hand as solid lubricant layers, which are constantly removed and renewed during the forming process. Ande on the other hand, they form monomolecular surface films that further lubricate can accumulate fabric components.

It is known from EP-A-675 192 and the literature cited therein that lubricating oils and greases for the lubrication of bearings intended bismuth compounds to add. The bismuth compounds serve as EP additives. Preferred two These are selected from naphthenates and / or carboxylates of the general NEN formula (R-CO₂) ₃Bi, in which R is a linear, branched or cyclic Al alkyl radical with 1 to 30 carbon atoms or an aryl, alkylaryl or arylalkyl radical with 5 up to 20 carbon atoms. In addition to bismuth naphthenates, bismuth  Alkyl carboxylates with 6 to 10 carbon atoms in the alkyl radical and especially the Wis mutoctoate particularly preferred. These bismuth compounds are especially for Replacement of the lead compounds with the same effect but toxicologically questionable thought.

The invention has as its object non-water-miscible or water-mixed Cooling lubricants or their water-miscible concentrates with improved To provide lubricating effect. The lubricating effect must be ver improving additive be designed such that it with the other components the cooling lubricants or their concentrates are compatible. For example, must it in an oil-based, water-immiscible and water-miscible cooling lubricants are soluble. For water-mixed cooling lubricants that are in the As an emulsion, the stability of the emulsion must not be added influence negatively.

In a first aspect, the invention relates to a friction-reducing additive for containing water-miscible or non-water-miscible cooling lubricants

• a) Bismuth compounds of organic acids
• b) sulfur-containing organic compounds

in a mixing ratio that the sulfur content of the additive is in the range from 2 to 30% by weight and the bismuth content was in the range from 1 to 25% by weight Gen. Preferably you choose the mixing ratio such that the sulfur hold the mixture in the range of about 5 to about 25 wt .-% and the bismuth hold in the range of about 4 to about 20 wt .-%. Additives are special preferred, in which the ratio of sulfur to bismuth content in Range from 1: 0.1 to 1: 2, preferably in the range from 1: 0.15 to 1: 1.  

The bismuth compounds are chosen in accordance with the teaching of EP-A-675 192 preferably from naphthenates and / or from carboxylates of the general Formula (R-CO₂) ₃Bi, in which R is a linear, branched or cyclic alkyl radical with 1 to 30 carbon atoms or an aryl, alkylaryl or arylalkyl radical with 5 to 20 C atoms means. The bismuth compounds are preferably selected from Naphthenates and / or from alkyl carboxylates with 6 to 10 carbon atoms in the alkyl radical. Bismutoctoate is particularly preferred. For better compatibility with water Mixed cooling lubricants can use these bismuth compounds with ethylene oxide and / or propylene oxide.

Organic sulfur compounds are known as extreme pressure additives (EP additives) generally known in the lubricant field. Examples of this are organic sulfides and disulfides, sulfurized paraffins, sulfurized fatty oils, sulfurized polyisobutene, sulfurized polypropylene or sulfurized poly styrene. These can be used together with phosphorhal to further increase the effectiveness term organic compounds are used. In the sense of the present Sulfurized fatty oils and sulfurized paraffins are particularly important prefers.

The additive according to the invention can also contain up to 5% by weight, based on the Total mass of the additive, compounds selected from the group of esters and / or the polyglycols. Examples of esters are di- and triglycerides such as turnip oil. Other examples are polymer esters such as Butanol esters of α-olefin-dicarboxylic acid copolymers. Polymer esters of this type, which can have a molecular weight of around 1,800, for example, are used by Akzo sold under the name Ketjenlube® 135. An example of a Usable polyalkylene glycol is the Emkarox® VG 180 from Erbslöh.  

In a further aspect, the invention relates to the use of the above described additive as a friction reducing additive in water-mixed or water-immiscible cooling lubricants. The additive is preferred used in such a concentration range that in the application ready against water-mixed cooling lubricants, which are usually called oil-in-water Emulsion present and prepared by adding a concentrate with water be, the bismuth content in the range of 0.01 to 0.2 wt .-%, preferably in Range from 0.02 to 0.15% by weight. For ready-to-use not water Miscible cooling lubricants are used in such a concentration tration range that the bismuth content in the range of 0.2 to 4 wt .-% before preferably in the range from 0.4 to 3% by weight.

Furthermore, the invention relates to the use of cooling lubricants, which Contain additive according to the invention, for the so-called minimal lubrication technology. This is occasionally, albeit misleading, used as low-quantity lubrication draws. For example, it is explained in the article by A. Walter: "Minimal lubrication technology and dry machining; possible areas of application", Deut sches industrial forum for technology 10/95 (DIF 17/21 / WA). At the minimal lubrication technology is used in comparison to the conventional use of cooling lubricants with significantly reduced amounts of cooling lubricant. this leads to greatly reduced cooling of the tool and workpiece. Therefore, the Lubrication to reduce the frictional heat in the process an increased importance be attributed. Lubrication can be reduced using a minimal Quantity lubrication can only be carried out using a suitable cooling lubricant. Of the Cooling lubricant is sprayed onto the tool and workpiece. For this The additive mixture according to the invention can be used as such, ie. H. without Mixing with other components can be used. However, it is also possible, the additive in a mixture with mineral oils, vegetable oils or synthetic  use polar connections. The proportion of the additive in the Ge velvet mixture amount to at least 10% by weight.

In a further aspect, the invention relates to a water-miscible concentrate for preparing a water-mixed cooling lubricant, which be the above written additive, preferably in an amount of about 2 to about 20% by weight based on the total concentrate contains. In addition to the additive mentioned the concentrate contains at least a base oil, an emulsifier and a selection from the additives listed in the introduction. To prepare the ready-to-use water mixed cooling lubricant is usually mixed with the concentrate about 50 to about 10, for example with about 20 parts by weight of water. A suitable This concentrate emulsifies spontaneously and forms a stable oil-in-water Emulsion.

Furthermore, the invention comprises a water-immiscible cooling lubricant, of about 2 to about 20 weight percent, for example about 10 weight percent, of the above described additive contains.

Embodiments

The following standard tests were carried out to check the lubricating effect:
Testing in the shell four-ball apparatus ("VKA") according to DIN 51350 part 1-3.

According to the DIN 51350 standard, there is a distinction between short and long-term tests distinguished.  

Short-term trial

The method according to this standard is used to determine the good and welding power of liquid lubricants with active ingredients that have high surface pressures in the Allow mixed friction area between surfaces moved relative to each other should (EP behavior).

For this purpose, the lubricant is checked in a four-ball system, which consists of a rotating ball (running ball), the same size under selectable test forces on three ß balls (standing balls) glides, exists. The test force is gradually increased until welding of the four-ball system occurs.

Before the start of the test, the test balls and the ball pot are filled with mineral spirits cleaned to get reproducible and therefore meaningful results. In three cleaned test balls are clamped into the cleaned ball cup. Subsequently the ball cup is filled with the lubricant to be tested so that the test ku gels are completely covered.

A test ball is carefully pressed into the ball holder and into the Test spindle inserted. After inserting the ball cup, the test force is applied brings. The test force is set by moving a barrel weight on the balance beam. This pressure generated in this way corresponds to the test ball load. The duration of the test run is one minute, unless it is by welding the test balls are broken off.

If there is no welding, further test runs with increased test force and new test balls required until the welding force is reached. The force at who is just not welding is called good force.  

Long-term trial

Long-term tests are carried out to make a statement about the wear preservation behavior of a lubricant (AW behavior).

For this purpose, the lubricant is checked in a four-ball system, which consists of a rotating ball (running ball) under a specified test force on three her same balls (standing balls), exists. According to procedure B a test load of 300 N is set. The test time is one hour. Subsequently the calotte diameters of the three standing balls are measured and averaged.

The wear diameter is measured with a Brinell magnifying glass or with a measuring microscope. The value determined in this way is used as a measure of the strength of the Viewed wear and is referred to as the average wear diameter ("AW wear").

Friction wear scales according to Reichert

This procedure is used to determine the pressure absorption capacity (EP behavior) and to determine the adhesive strength of liquid lubricants. Here, a test roller is adapted by means of a lever system to a rotating slip ring, which is immersed with its lower third in the lubricant to be tested. Before the start of the test, the test roll, which has been cleaned in white spirit, is installed in the swiveling holder. The holder is swung in and clamped firmly. The slip ring remains clamped in the device for several test runs, where it is also cleaned with white spirit after each test run. The test roller is placed on the slip ring by slowly applying the load weight (1.5 kg). The number on the Reichertwaage is set to 0. When the motor is switched on, the rotating slip ring immersed in the lubricant continuously supplies the contact point with lubricant. When the number 100 is reached on the counter (100 meter friction distance), the test roller is removed from the slip ring. The test roller is removed and the resultant cut mark is measured using a measuring magnifier. The ellipse area is calculated as 0.785 _* length _* width, or is read off using a number table. So many test runs are carried out until the ellipse surfaces of the last 3 test runs differ from one another by no more than 10%. The Druckaufnahmever like is the greater, the smaller the elliptical surface determined.

1. Water-immiscible cooling lubricants

By mixing base oil and additives according to Table 1, Ver same examples and examples according to the invention for water-immiscible cooling lubricants manufactured. The lubricating effect of the mixtures was determined using the Four-ball apparatus checked. The results are also shown in Table 1. % Figures for base oil and for additives are% by weight with respect to the total mi shung. Sulfur and bismuth contents are also as% by weight based on Ge velvet blend specified.

2. Water-miscible cooling lubricants

The following concentrates of water-miscible cooling lubricants were produced, which are similar in their composition to common commercial products. 90 Ge each most of these concentrates were mixed with 10 parts by weight of additive. Out These mixtures were ready-to-use water-mixed coolant emulsions ions produced by adding 5 parts by weight of the concentrate / additive mixture were mixed with 95 parts by weight of water. The lubricating effect was with the Reichert scales measured. The results are shown in Table 2.

Concentrate 1 (Composition in% by weight)

36% paraffinic mineral oil
6% monoethanolamine
4% triethanolamine
8% boric acid
7% tall oil fatty acid
8% tall oil fatty acid monoethanolamide
2% glycerin
7% oleyl / cetyl alcohol x 10 ethylene oxide
Rest: demineralized water

Concentrate 2

45% paraffinic mineral oil
5% beet oil
14% tall oil fatty acid
2.5% potassium hydroxide
7% tall oil fatty acid monoethanolamide
2% triethanolamine
6% hexanediol-2,4
12% oleyl / cetyl alcohol x 2 ethylene oxide
3% benzyl hemiformal
Rest: demineralized water

Concentrate 3

21% paraffinic mineral oil
16% tall oil fatty acid
5% dimer fatty acid
15% potassium hydroxide
4% diethylene glycol monobutyl ether
5% dodecyl succinic anhydride
5% beet oil
0% ethylene glycol monophenyl ether
19% oleyl / cetyl alcohol × 12 EO

Table 2

Water-miscible cooling lubricants

(The indicated S and Bi contents refer to the total mixture)

Claims (12)

1. Friction-reducing additive for water-miscible or non-water-miscible cooling lubricants, containing

• a) Bismuth compounds of organic acids
• b) sulfur-containing organic compounds

in a mixing ratio that the sulfur content of the additive in the Be ranges from 2 to 30% by weight and the bismuth content ranges from 1 to 25 % By weight. 2. Additive according to claim 1, characterized in that the ratio of Sulfur content to bismuth content of the additive in the range of 1: 0, 1 to 1: 2 lies. 3. Additive according to claim 1 or 2, characterized in that the bismuth compounds are selected from naphthenates and / or carboxylates general formula (R-CO₂) ₃Bi, in which R is a linear, branched or cyclic alkyl radical with 1 to 30 carbon atoms or one Aryl, alkylaryl or arylalkyl radical having 5 to 20 carbon atoms. 4. Additive according to claim 3, characterized in that the bismuth compound gen are selected from naphthenates and / or from alkyl carboxylates with 6 up to 10 carbon atoms in the alkyl radical. 5. Additive according to one or more of claims 1 to 4, characterized records that the sulfur-containing organic compounds are selected from organic sulfide and disulfide, sulfurized paraffins, welded  Felt fatty oils or sulfurized polyisobutene, sulfurized polypropylene or sulfurized polystyrene. 6. Additive according to one or more of claims 1 to 5, characterized records that it is additionally up to 5 wt .-%, based on the total mass of Additives, compounds selected from the group of Contains esters and / or the polyglycols. 7. Use of an additive according to one or more of claims 1 to 6 as a friction reducing additive in water-mixed or non-water miscible cooling lubricants. 8. Use according to claim 7, characterized in that the bismuth content of the ready-to-use water-mixed cooling lubricants in the range of 0.01 to 0.2 wt .-%, the bismuth content of the ready-to-use not what miscible cooling lubricants is in the range of 0.2 to 4 wt .-%. 9. Use of an additive according to one or more of claims 1 to 6 alone or in a mixture with mineral oils, vegetable oils and / or synthetic polar connections for minimal lubrication technology. 10. Water-miscible concentrate for preparing a water-mixed cooling Lubricant containing 2 to 20 wt .-% of an additive after one or more of claims 1 to 6 contains. 11. Water-immiscible cooling lubricant containing 2 to 20% by weight of an additive according to one or more of claims 1 to 6.