WO2003018729A1

WO2003018729A1 - Non-toxic biodegradable grease

Info

Publication number: WO2003018729A1
Application number: PCT/DK2002/000567
Authority: WO
Inventors: Jørgen Peder BEYER; Søren LINDEMANN
Original assignee: Abcon Aps
Priority date: 2001-08-31
Filing date: 2002-08-30
Publication date: 2003-03-06
Also published as: NO20041349D0; NO20041349L

Abstract

A non-toxic biodegradable grease for lubricating mechanisms, which are exposed to high load such as curving rails in railways and wheel flanges on railway cars and locomotives, as well as for lubricating all sorts of equipment working in areas where full biodegradability is required such as in agriculture, forestry, sports areas and marine environments, comprises a glyceride oil, one or more stearates, one or more long chain esters, bentonite, and a meal. Where the grease is exposed to daylight, it usually further comprises an anti-oxidant, and to further enhance the lubricating capacity of the grease a small amount of polytetrafluoroethylene (PTFE) may be added.

Description

Non-toxic biodegradable grease

This invention concerns a non-toxic biodegradable grease for lubricating mechanisms which are exposed to high load such as curving rails in railways and wheel flanges on railway cars and locomotives. The grease may also be used to lubricate moving parts on tracks such as switch blades. Further, the grease may be used for lubricating all sorts of equipment working in areas where full biodegradability is required such as in agriculture, forestry, and sports areas including golf courses, and in marine environments, for example for lubri- eating sluice and floodgate valves, lock gates and marine railways. In addition, the food and pharmaceutical industries are natural users of the grease, as they require non-toxic and harmless lubricating agents.

TECHNICAL BACKGROUND

For some time the railway authorities in major countries such as Rail Track in Great Britain have installed so-called Lubricators on the outer rail in curves for the purpose of obviating pitting and ensuing collapse of the rail and the wheel flanges. These lubricators are devices that at the start of a rail curve release a lubricating grease to the passing wheels which then distribute the grease over up to 2 km of rail.

In order to function properly as a lubricating and protective coating on the rail and the wheel flanges a rail grease must fulfil certain requirements the most important of which are:

■ it must have a paste-like consistency that makes it pumpable and spread- able along the rail;

■ it must have a good adhesion and not be easily washed off by rain water;

■ it must have a high load bearing capacity being resistant to high pressure;

» it must be stable and functional over a wide temperature range of from -20 °C up to +100 °C. Traditionally, rail greases have been based on mineral oil containing emulsifiers and various additives to impart i.a. consistency and pressure resistance (load bearing capacity). However, with the extended use of lubricators in consequence of the introduction of high velocity trains i.a. Rail Track in Great Britain has now decided to use rail grease which is biodegradable and non-toxic.

A few products purporting to be biodegradable and non-toxic as well as to fulfil the general requirements to a rail grease have been put on the market. For example, one known product is based on synthetic ester oils containing lithium and calcium 12-hydroxystearate as thickeners and a sulfur-containing high- pressure additive, but this product has shown problems with insufficient adhesion so that the grease is not distributed far enough along the rail and is liable to water wash-off. In addition, this product is toxic due to the sulfur-containing additive. Another known product is based on rapeseed oil containing lithium 12- hydroxystearate. This product has a relatively large content of water and has shown limited adhesion at the lower end of the temperature range and a tendency to separate when stored. Yet another known product has exhibited inferior winter capabilities due to a high content of water.

SUMMARY OF THE INVENTION

The non-toxic biodegradable grease according to the invention is based on glyceride oil, for example vegetable oil such as cottonseed oil, soybean oil, palm oil, palm kernel oil, rapeseed oil, cottonseed oil and linseed oil. Also oils of animal origin such as lard oils may be used. Preferably, the oil is a so-called RBD-oil (i.e. highly refined, bleached and deodorised) being liquid down to -20 °C or below and being stable to oxidation and other degradation by storage for minimum one year.

By using different oil types of vegetable origin, it is possible to impart particular high and low temperature properties as well as higher or lower carrying capacity and rust-preventing effect to the grease according to the invention. Also, the adherence, in particular to cold and wet surfaces, may be varied in this way.

To this glyceride oil is added emulsifiers comprising various stearates such as lithium, magnesium, calcium or zinc stearate; extreme pressure (EP) additives comprising long chain esters, in general esters of inorganic acids, and optionally specific stearates, such as zinc stearate; and consistency-providing fillers comprising bentonite and various meals. When the grease is to be used in daylight, an anti-oxidant is usually added, too

The stearates are added as emulsifiers and thickeners. Some stearates have specific advantages. For example, calcium stearate imparts water resistance and a thick fatty consistency and also high temperature properties enabling the grease to be heated up to about 150 °C before becoming light-fluid. Zinc stearate besides contributing to the consistency also adds high pressure properties.

The long chain esters are used as high-pressure additives. They are generally esters of inorganic acids such as phosphoric acid and sulfuric acid, in particular phosphate esters, and more particularly polyglycol, sorbitan and alkoxylated polyol esters of phosphoric acid.

The consistency-providing bentonite may be unactivated in which case an acti- vator comprising a small amount of propylene carbonate and water or an about ten fold amount of alcohol and water must also be added; or the bentonite may preferably be activated previously (so-called self activating bentonite) in which case no activator needs to be added. Of course, mixtures of unactivated and activated bentonite may also be used with correspondingly reduced amounts of activator.

A meal is also added as a filler to regulate consistency and retain the oil, part of which is absorbed by the meal particles and is squeezed out when subjected to pressure. The meal may be any kind of absorbent meal such as saw dust, wheat flour, maize flour (corn meal), soy meal, soy protein, rape meal, linseed meal, groundnut meal, desiccated coconut etc. Preferably, a meal containing some oil and thus being water repellent such as soy protein is used.

When an anti-oxidant is used, it may be any of the well known antioxidants for use with fats and oils, such as tocopherols, butylated hydroxyanisole (BHA), bu- tylated hydroxytoluene (BHT), gallates and polyaromatic amines, e.g. diphenyl amine, or mixtures thereof, often in admixture with metal chelators such as ascorbic, citric and phosphoric acids or esters thereof. The anti-oxidants inhibit the oxidation of double bonds in the oil under the influence of atmospheric oxy- gen and UV radiation. Thereby, the antioxidants have a strong influence on the hardening time of the oil, which is decisive for how soon or late the oil will solidify on the track. Thus it is possible, by adjusting the type and amount of anti- oxidant, to control the hardening time of the grease according to the invention. This is important, as it provides a means of regulating the distance that the grease will be able to travel along the tracks. Similarly, it is possible by means of the same anti-oxidants to adjust the consistency and smoothness of the grease according to the invention so that it may also be used in train-carried systems for lubricating tracks and wheels when driving straight ahead on high- velocity trains.

As anti-oxidant is preferably used a mixture of propyl gallate (PG) and citric acid esters of fatty acid mono- and diglycerides in a ratio of from 10:90 to 30:70 by weight in a total amount of 100-5000 ppm. Other suitable anti-oxidants are bu- tylhydroxytoluene (BHT) or a polyaromatic amine such as diphenyl amine, also in an amount of 100-5000 ppm.

The lubricating capacity of the rail grease according to the invention may be further enhanced by the addition of a small amount of polytetrafluoroethylene (PTFE).

Thus, a useful embodiment of a grease according to the invention comprises the following, by weight:

70 - 85 % refined vegetable oil, 15 - 30 % stearate, 2 - 10 % long chain ester, 1 - 6 % activated (self activating) bentonite, 1 - 20 % meal.

Another useful embodiment of a grease according to the invention comprises the following, by weight:

70 - 85 % refined vegetable oil, 15 - 30 % stearate, 2 - 10 % long chain ester,

1 - 6 % unactivated bentonite, 2 - 16 % activators, 1 - 20 % meal. If polytetrafluoroethylene is added, the amount will generally be in the range of 0.5-5 % by weight, preferably about 2 % by weight.

In preferred embodiments of a grease according to the invention the oil portion is a mixture of soybean oil with e.g. rapeseed oil or palm kernel oil in varying ra- tios between 90:10 and 10:90 by weight. By admixture of palm kernel oil the flow properties of the grease are enhanced, which entails a faster "travel" of the grease. By admixture of linseed oil the rust-preventing properties are enhanced.

A useful embodiment, designed for applications where the presence of sea water courses problems in terms of premature degration of the lubricant and corro- sion, comprises the following, by weight: 10 - 15 % linseed oil, 5 - 10 % rapeseed oil, 55 - 70 % soybean oil, 10 - 30 % stearates, 15 - 30 % esters,

1 - 2 % anti-oxidant,

2 _r 7 % activated (self activating) bentonite,

1 - 10 % meal.

A useful embodiment, designed for wheel and flange lubrication where the lu- bricant is being applied via train mounted lubrication systems, comprises the following, by weight:

5 - 15 % palm kernel oil, 60 - 75 % soybean oil, 10 - 30 % stearates, 2 - 20 % esters,

2 - 4 % anti-oxidant,

2 - 7 % activated (self activating) bentonite, 1 - 10 % meal. EXAMPLES

Example 1

A grease having the following composition is suitable as a rail grease for lubricating curving rails and wheel flanges on railway cars:

soybean oil, RBD 72.0 % w/w zinc stearate 15.5 % w/w alkoxylated polyol phosphate ester 1.1 % w/w bentonite, unactivated 4.8 % w/w propylene carbonate 1.1 % w/w water 1.1 % w/w soy protein 4.4 % w/w

In this composition the propylene carbonate and water as activator for the bentonite can be replaced by the ten-fold amount of alcohol and water.

If desired, a small amount of polytetrafluoroethylene (PTFE) may be added, for example 2 % w/w PTFE.

The mixed grease has a paste-like consistency and a cream colour. If desired, a non-toxic dye may be added, for example a green fruit colouring.

Example 2

A grease having the following composition is suitable for applications where the presence of sea water courses problems in terms of premature degration of the lubricant and corrosion:

linseed oil 10 % w/w rapeseed oil 5 % w/w soybean oil 55 % w/w calcium stearate 10 % w/w alkoxylated polyol phosphate ester 15% w/w propyl gallate (20%) + citric acid esters of diglycerides (80%) 1 % w/w activated (self activating) bentonite 3% w/w soy protein 1 % w/w.

Example 3

A grease having the following composition is suitable for wheel and flange lubri- cation where the lubricant is being applied via train mounted lubrication systems:

palm kernel oil 6 % w/w soybean oil 60 % w/w zinc stearate 20 % w/w alkoxylated polyol phosphate ester 7 % w/w butyl hydroxy toluene (BHT) 2 % w/w activated (self activating) bentonite 2 % w/w soy protein 3 % w/w.

Claims

1. A non-toxic biodegradable grease comprising a glyceride oil, one or more stearates, one or more long chain esters, bentonite, and a meal.

2. A grease according to claim 1 wherein the glyceride oil is a highly refined, bleached and deodorised vegetable oil being liquid down to -20 °C or below and being stable to oxidation and other degradation by storage for minimum one year.

3. A grease according to claim 1 or 2 wherein the glyceride oil is selected from the group consisting of soybean oil, palm oil, palm kernel oil, rapeseed oil, cot- tonseed oil and linseed oil.

4. A grease according to claim 1 ,2 or 3 wherein the stearate is selected from the group consisting of lithium, magnesium, calcium and zinc stearate.

5. A grease according to claim 4 wherein the stearate is zinc stearate.

6. A grease according to claim 4 wherein the stearate is a mixture of calcium and zinc stearate.

7. A grease according to any one of claims 1-6 wherein the long chain ester is an ester of an inorganic acid.

8. A grease according to claim 7 wherein the ester is a phosphate ester.

9. A grease according to claim 8 wherein the phosphate ester is selected from the group consisting of polyglycol, sorbitan, and alkoxylated polyol esters of phosphoric acid.

10. A grease according to any one of claims 1 -9 wherein the bentonite is a self- activating bentonite.

11. A grease according to any one of claims 1 -9 wherein the bentonite is unac- tivated and is added together with a sufficient amount of propylene carbonate and water or a sufficient amount of alcohol and water to activate it.

12. A grease according to any one of claims 1-11 wherein the meal is selected from the group consisting of saw dust, wheat flour, maize flour (corn meal), soy meal, soy protein, rape meal, linseed meal, groundnut meal, and desiccated coconut.

13. A grease according to claim 12 wherein the meal is soy protein.

14. A grease according to any one of claims 1 -13, which further comprises an anti-oxidant.

15. A grease according to claim 14 wherein the anti-oxidant is selected from the group consisting of tocopherols, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), gallates and polyaromatic amines, e.g. diphenyl amine.

16. A grease according to claim 14 or 15 wherein the anti-oxidant is in admixture with a metal chelator.

17 A grease according to claim 16 wherein the metal chelator is selected from the group consisting of ascorbic acid, citric acid, phosphoric acid and esters thereof.

18. A grease according to any one of claims 1-17, which further comprises a small amount of polytetrafluoroethylene (PTFE).

19. A grease according to claim 1 comprising by weight:

70 - 85 % refined vegetable oil, 15 - 30 % stearate,

2 - 10 % long chain ester,

1 - 6 % activated (self-activating) bentonite,

1 - 20 % meal.

20. A grease according to claim 1 comprising by weight: 70 - 85 % refined vegetable oil,

15 - 30 % stearate,

2 - 10 % long chain ester,

1 - 6 % unactivated bentonite, 2 - 16 % activators, 1 - 20 % meal.

21. A grease according to claim 1 comprising by weight: 10 - 15 % linseed oil, 5 - 10 % rapeseed oil, 55 - 70 % soybean oil, 10 - 30 % stearates,

15 - 30 % esters,

1 - 2 % anti-oxidant,

2 - 7 % activated (self activating) bentonite,

1 - 10 % meal.

22. A grease according to claim 1 comprising by weight: 5 - 15 % palm kernel oil, 60 - 75 % soybean oil, 10 - 30 % stearates,

2 - 20 % esters, 2 - 4 % anti-oxidant,

2 - 7 % activated (self activating) bentonite, 1 - 10 % meal.

23. A grease according to any one of claims 19-22, which further comprises as anti-oxidant a mixture of propyl gallate (PG) and citric acid esters of fatty acid mono- and diglycerides in a ratio of from 10:90 to 30:70 by weight in a total amount of 100-5000 ppm.

24. A grease according to any one of claims 19-22, which further comprises as anti-oxidant butylhydroxytoluene (BHT) in an amount of 100-5000 ppm.

25. A grease according to any one of claims 19-24, which further comprises 0.5-5 % by weight, and preferably about 2 % by weight, of polytetrafluoroethylene (PTFE).