EP2185671A2

EP2185671A2 - Cooling lubricant

Info

Publication number: EP2185671A2
Application number: EP08801267A
Authority: EP
Inventors: Müfit BAHADIR; Hubertus Wichmann; Jürgen HESSELBACH; Ralf Bock; Christoph Herrmann
Original assignee: Technische Universitaet Braunschweig
Current assignee: Technische Universitaet Braunschweig
Priority date: 2007-08-30
Filing date: 2008-08-29
Publication date: 2010-05-19
Also published as: WO2009026916A2; DE102007041372A1; WO2009026916A3

Abstract

The invention relates to a cooling lubricant for machine tools. According to the invention, said lubricant has an alcohol content of more than 40 % by mass of one or more polyvalent alcohols, which have at least three carbon atoms, and is alkaline.

Description

coolant

The invention relates to a cooling lubricant for machine tools. According to a second aspect, the invention relates to a machining process.

Cooling lubricants are used in manufacturing technology for cutting and forming on machine tools of heat dissipation and the reduction of friction between the tool and the workpiece by lubrication. In addition, during machining processes they are used to remove the chips by rinsing them out of the working environment. During cutting and forming, friction occurs between the tool and the workpiece. Cooling lubricants reduce the wear of the tool by reducing this friction and counteract heating of the workpiece and the tool.

In principle, metalworking lubricants are divided into the two main groups of non-water-miscible and water-miscible coolant lubricants. The former are used undiluted and have their strengths in the areas of friction and wear-reducing properties as well as in the area of disposal or recycling. The latter are diluted with water before use and have their strengths in the cooling effect, in the rinsing and wetting action as well as in the area of fire and explosion protection.

The water-miscible cooling lubricants are subdivided further into the water-soluble and the emulsifiable cooling lubricants. In contrast to water-soluble emulsifiable KSS a water-immiscible oil phase, which is dispersed by means of emulsifiers in the water phase. Here, water-soluble cooling lubricants are characterized by better rinsing power and emulsifiable cooling lubricants through better corrosion protection and better friction-reducing properties.

For metalworking, especially for grinding, today all available types of coolants are used. Some decades ago, however, mainly water-soluble cooling lubricants, which are characterized above all by good rinsing and cleaning behavior, were used for grinding operations. Due to the demand for improved corrosion protection and more universal substitution of the cooling lubricants, more and more emulsifiable cooling lubricants have been used over the years for grinding operations. Water-blended cooling lubricants, ie both emulsifiable and water-soluble, are particularly suitable for grinding operations because of the high water content due to the high water content, since the heat released by the high cutting speeds is considerable and must be removed as quickly as possible to avoid damage to the workpieces.

The advancement of tool technology from the classic ceramic and synthetic resin bond of the abrasive grain to the metallic bond has enabled a significant increase in the peripheral speeds of the grinding wheels in the last 15 years. Modern high-speed grinding processes with metal-bonded CBN grinding wheels (Cubic Boron Nitride) today achieve circumferential and thus cutting speeds of up to 200 m / s. In the area of these cutting speeds, it was found that the resulting process heat could no longer be dissipated by water-mixed cooling lubricant. The state of the art in this case is the use of non-water-miscible abrasive oils, since it turned out that the superior friction-reducing properties of these products considerably reduce the heat of the process and thus makes the grinding operation technologically manageable. The basis of a modern grinding oil for high-speed grinding operations is usually a low-viscosity base oil (kinematic viscosity: 5-15 mm ² / s at 40 °) is used, which is characterized by a good viscosity-temperature behavior (high viscosity index), a relatively high flash point , good aging stability and low aerosol formation potential should distinguish. In general, hydrocracking mineral oil or even polyalphaolefins are used for this purpose. To improve the flushing behavior (flushing of the chip chambers of the grinding wheel) and to optimize the friction-reducing properties, ester additives are used. Wear protection additives, aging protection, anti-fog additives to reduce the aerosol formation potential and possibly a non-ferrous metal additive add-on complete the grinding oil, on whose performance every new product concept has to be measured.

The disadvantages of today's non-water-miscible KSS are:

fire hazard

Possible formation of explosive aerosols - possible water hazard (WGK 1 or higher)

Need for parts cleaning after processing

disposal costs

Sharp rising costs due to crude oil price increases

Increased effort for chip removal. - Significantly lower cooling effect than water-miscible KSS

Significantly lower rinsing effect than water-miscible KSS

At lower viscosities skin irritation effect by degreasing the

skin The disadvantages of today's water-miscible emulsifiable KSS are:

Microorganism susceptibility, therefore use of partially harmful biocides Disposal costs - Lower lubricity than non-water-miscible KSS Possible water hazard (WGK 1 or higher) Possible skin irritation due to degreasing of the skin due to contained emulsifiers

The disadvantages of today's water-miscible water-soluble KSS are:

Microorganism susceptibility, therefore use of partially harmful biocides Disposal costs Lower lubricity than non-water-miscible KSS and water-miscible emulsifying KSS - Possible water hazard (WGK 1 or higher)

Possible skin irritation due to degreasing of the skin due to wetting agents

A disadvantage of the known cooling lubricant is - the expensive production, since in particular fruit juices are expensive to produce, the use of food-grade components in the manufacture and use, the lack of performance additives, especially wear reducers, the high stresses of the cooling lubricant during industrial processing processes allow only lack of corrosion and non-ferrous metal protection for workpieces and machine tool, poor filterability in the operating phase, with adhesions and precipitation and the lack of heat removal capacity in the described combination. It is known from DE 196 37 168 A1 a cooling lubricant consisting of glycerol, water, sugar, cornflour, gelatin, Tortenguss, plum juice, coffee, yeast, milk and wood spirit. A disadvantage of the known cooling lubricant is its expensive production, since in particular fruit juices are expensive to produce.

The invention has for its object to overcome disadvantages in the prior art. The invention solves the problem by a metalworking machine tool lubricant having an alcohol content of more than 40% by weight of one or more polyhydric alcohols having at least three carbon atoms, and which is alkaline. According to a second aspect, the invention solves the problem by a machining process which uses a cooling lubricant having an alcohol content of more than 20% by mass, in particular more than 50% by mass, of one or more polyhydric alcohols having at least three carbon atoms. Atoms, and which is alkaline.

An advantage of the invention is that the cooling lubricant can rely on inexpensive available glycerol and water (drinking water quality). By processing rapeseed oil into rapeseed oil methyl ester, large quantities of glycerol are produced. Glycerin is therefore available at low cost. Another advantage of the invention is that it is essentially non-toxic. This increases occupational safety and reduces disposal costs. The latter are also drastically reduced by the fact that the workpieces can easily be cleaned of cooling lubricant residues after processing, without resulting in emulsions containing mineral oil (currently 1 million t / a of oily washing liquids from industrial metal processing in Germany, disposal costs: approx. 300 € / t) that, unlike previously, the metal chips can be easily separated from the large amount of grinding sludge and Thus profitable recycling instead of expensive disposal is possible and that the cooling lubricant or the washing liquids can be used for example as a supplement in biogas production.

It is also advantageous that the cooling lubricant without biocides, especially without fungicides and bactericides, gets along. It is advantageous that the cooling lubricant acts to inhibit corrosion, without relying on oil-containing components. The risk of fire and deflation of the inventive cooling lubricant is lower than for mineral oil-containing cooling lubricants.

An advantage of the invention is that the cooling lubricant during internal grinding of 100Cr6 shows an unexpectedly high performance in the grinding process under industrial production conditions. In grinding tests, compared to conventional water-miscible and water-immiscible mineral oil-based cooling lubricants, a significantly lower normal force with constant tangential forces was found. As a result, increases in the time-spanning volume are realized by up to a factor of two. This can be achieved with a fluid, for example, of the composition given as Example 11.

In the context of the present description, the alcohol content is understood to mean the amount in mass% which the polyhydric alcohols having at least three carbon atoms have on the cooling lubricant.

According to a preferred embodiment, the alcohol component consists predominantly of 1,2,3-propanetriol. This component prevents decomposition processes by microorganisms, without even being toxic to humans in low doses. Particularly preferably, the cooling lubricant has more than 40% by mass, in particular more than 80% by mass, of 1,2,3-propanetriol. In order to achieve a high cooling effect, the cooling lubricant preferably comprises at least 20% by mass of water. It has been found that a water content of at most 55% by mass is particularly advantageous. In the following, percentages, unless stated otherwise, are in% by mass.

The cooling lubricant is particularly easy to dispose of and has low toxicity if it is substantially hydrophilic, in particular it is completely free of mineral oil. By the feature that the cooling lubricant is hydrophilic, it is to be understood that the alcohol portion is completely dissolved in water or conversely that water is completely dissolved in the alcohol portion.

With regard to the toxicity, particularly advantageous properties result when substantially only substances with a molecular weight of less than 200 g / mol are contained. This also results in a cooling lubricant, in which a formation of deposits is substantially suppressed. With such a cooling lubricant, the risk of carbonization (charring) is also low. In particular, the cooling lubricant is carbohydrate-free and fruit juice-free, which prevents machined workpieces from sticking and attracting dust.

It is advantageous if free and in the water / alcohol mixture are well and without special excipients soluble salts of Dialkyldithiophosphorsäuren included, which act as anti-wear additives and at the same time as antioxidants.

It has proved to be particularly advantageous if the cooling lubricant is buffered to a pH of at least 7.5, in particular more than 8. Also advantageous is a pH of less than 10. For buffering, disodium tetraborate decahydrate, for example from 0.5 to 5% by mass, of tripotassium phosphate, for example from 0.5 to 5% by mass, of dipotassium hydrogen peroxide. poshphat, in particular from 0.5 to 5% by mass, and / or fatty acids or salts or derivatives thereof, for example from 0.5 to 5% by mass, are advantageous. In addition, the cooling lubricant preferably contains akanolamines for buffering, such as monoethanolamine, triethanolamine, 2- (2-aminoethoxy) ethanol (diglycolamide), 2-amino-2-methyl-1-propanol, 1-aminopropan-2-ol (isopropanolamine). Preferably, alkali metal hydroxide, such as sodium hydroxide or potassium hydroxide, is used to adjust the desired pH.

Dicarboxylic acids, for example sebacic acid and azelaic acid, and alkylarylsulfonylaminocarboxylic acids, medium-chain isoaliphatic and aliphatic monocarboxylic acids (C8-C10) and triazine tricarboxylic acids are used as anticorrosive components in each case for combination with the abovementioned alkanolamines or alkali metal hydroxides in a concentration of 0.1 to 10% by mass used in concentrations of 0.1 to 5% by mass.

Very advantageous is the use of a non-ferrous metal deactivator, for example 1 H-benzotriazole or derivatives of this substance. Examples of such derivatives are 2,2 '- [[(5-methyl-1H-benzotriazol-1-yl) -methyl] imino] bis-ethanol and 2,2' - [[(4-methyl-1H- benzotriazol-1-yl) methyl] imino] bisethanol in concentrations of 0.05 to 1% by mass.

In addition, wear reducers such as salts of dialkyldithiophosphoric acids, for example dibutyldithiophosphoric acid, contain from 0.1 to 5% by mass of phosphate salts, sulfurized fatty acids, sulfurized fatty acid esters, fatty acid esters, ethoxylated phosphoric acid esters and polyalkylene glycols in the concentration range from 0.1 to 5 mass -% to increase the performance of the cooling lubricant.

In addition, the cooling lubricant preferably also comprises a corrosion inhibitor, for example triethanolamine, where the concentration can range from 0.5 to 10% by mass. The present invention also relates to a machine tool, for example a cutting machine tool, comprising a cooling lubricant described above. This coolant can for example also be diluted with water.

The following are examples of the composition according to the invention of a cooling lubricant:

example 1

From 30 to 70% by weight of glycerol,

28 to 68% by mass of water and

2 to 10 mass%, so that 100% result from a component of the

A group formed from a corrosion inhibiting component, a pH adjusting agent, a non-ferrous metal deactivator and a wear reducer as mentioned above.

Example 2:

60% propylene glycol

1.5% triethanolamine

2.3% Na ₂ B ₄ O ₇ * 10 H ₂ O

4% K ₂ HPO ₄ ad 100% water pH = 8.4

Example 3:

60% glycerol 1, 5% triethanolamine 2.3% Na ₂ B ₄ O ₇ * 10 H ₂ O 4% K ₂ HPO ₄ ad 100% water pH = 7.6 Example 4:

60% propylene glycol 1.5% triethanolamine 2.3% Na ₂ B ₄ O ₇ * 10 H ₂ O

2.4% K ₂ HPO ₄ ad 100% water pH = 9.1

Example 5:

60% glycerin

1.5% triethanolamine 2.3% Na ₂ B ₄ O ₇ ^» 10 H ₂ O

2.4% K ₃ PO ₄ ad 100% water pH = 8.7

Example 6:

60% ethylene glycol 1.5% triethanolamine 2.3% Na ₂ B ₄ O ₇ * 10 H ₂ O 4% K ₂ HPO ₄ ad 100% water

Example 7: 60% glycerol

, , 5% triethanolamine 2.3% Na ₂ B ₄ O ₇ * 10 H ₂ O 2.4% K ₃ PO ₄

1% sulphurised fatty acid (s) ad 100% water Example 8:

60% glycerol 1.5% triethanolamine 2.3 ⁰ ZoNa ₂ B ₄ O ₇ -IOH ₂ O

2.4% K ₃ PO ₄

1% di- (4-methyl-2-pentyl) -di-thiophosphoric acid ad 100% water

Example 9:

60% glycerin

, , 5% triethanolamine 2.3 ⁰ ZoNa ₂ B ₄ O ₇ MOH ₂ O

2.4% K ₃ PO ₄

1% di- (3-methyl-1-butyl) -di-thiophosphoric acid ad 100% water

Example 10:

60 ⁰ Zo glycerin

1.5% triethanolamine 2.3 ⁰ ZoNa ₂ B ₄ O ₇ -IOH ₂ O 2% fatty acids / fatty acid derivatives ad 100% water

Example 11:

51, 50% water

45.00% glycerol 0.85% triethanolamine

0.90% 2-amino-2-methyl-1-propanol 0.90% sulfurized fatty acid 0.50% sebacic acid 0.30% isononanoic acid 0.05% Mixture of 2,2 '- [[(5-methyl-1 H-benzotriazole-1-yl) -methyl] imino] bis-ethanol and 2,2 '- [[(4-methyl-1H-benzotriazol-1-yl) -methyl] imino] bis-ethanol

Pl / be

Claims

claims

1. Cooling lubricant for machine tools, characterized in that it (a) has an alcohol content of more than 40% by mass of one or more polyhydric alcohols having at least three carbon atoms and (b) is alkaline.

2. Cooling lubricant according to claim 1, characterized in that the alcohol content consists predominantly of 1, 2,3-propanetriol.

3. Cooling lubricant according to one of the preceding claims, characterized in that it has more than 40% by mass, in particular more than 80% by mass, 1, 2,3-propanetriol.

4. Cooling lubricant according to one of the preceding claims, characterized in that it contains at least 20% by mass of water.

5. Cooling lubricant according to one of the preceding claims, characterized in that it contains at most 55% by mass of water.

6. Cooling lubricant according to one of the preceding claims, characterized in that it is predominantly hydrophilic, in particular completely mineral oil-free.

7. Cooling lubricant according to one of the preceding claims, characterized in that the organic constituents more than 90% by weight have a molecular weight of less than 200 g / mol.

8. Cooling lubricant according to one of the preceding claims, characterized in that it is buffered to a pH of at least 7.5.

9. Cooling lubricant according to one of the preceding claims, characterized in that it comprises a corrosion inhibitor.

10. Cooling lubricant according to one of the preceding claims, characterized in that it comprises a wear reducer.

11. Cooling lubricant according to one of the preceding claims, characterized in that it comprises a non-ferrous metal deactivator, in particular 1 H-benzotriazole and / or one or more derivatives.

12. Cooling lubricant according to one of the preceding claims, with

(a) 30 to 70% by weight of glycerol,

(b) from 28 to 68% by mass of water; and (c) from 2 to 10% by mass to give 100% of one of the group consisting of a corrosion inhibiting component, a pH adjuster, a non-ferrous metal deactivator, and a wear reducer.

13. Cooling lubricant according to one of the preceding claims, with

(a) 46.5% - 55.5%, especially 51, 5%, water,

(b) 40.0% - 50.0%, especially 45.0%, glycerol,

(c) 0.35% -1.35%, especially 0.85%, triethanolamine,

(d) 0.40% - 1, 40%, especially 0.90%, 2-amino-2-methyl-1-propanol, (e) 0.40% - 1, 40%, in particular 0.90%, sulphurised fatty acid,

(f) 0.10% - 1, 00%, especially 0.50%, sebacic acid,

(g) 0.1% -0.5%, in particular 0.30%, isononanoic acid, (h) 0.01% -0.10%, in particular 0.05%, mixture of

2,2 '- [[(5-methyl-1H-benzotriazole-1-yl) -methyl] imino] bis-ethanol and 2,2' - [[(4-methyl-1H-benzotriazole-1-yl ) -methyl] imino] bis-ethanol, giving 100%.

14. Machine tool, characterized in that it comprises a cooling lubricant according to one of the preceding claims.

15. Zerspanverfahren, characterized in that a cooling lubricant, the

(a) has an alcohol content of more than 20% by mass, in particular more than 50% by mass, of one or more polyhydric alcohols having at least three carbon atoms, and

(b) is alkaline, is used, in particular a cooling lubricant according to one of

Claims 1 to 13 is.

16. Zerspanverfahren according to claim 15, characterized in that it is a Zerspanverfahren with geometrically defined cutting edge, in particular a turning or milling.

17. Zerspanverfahren according to claim 15, characterized in that it is a Zerspanverfahren with geometrically undefined cutting edge, in particular a grinding or lapping.

18. Use of a liquid having the features of one of claims 1 to 13 as a cooling lubricant.