AND RAIL APPLICATIONS

FIELD OF THE INVENTION

The present invention relates to novel lubricant and

friction modifier compositions comprising a solid lubricant, or

a friction modifier, or both along with a binding agent in water

medium suitable for lubricating steel-steel interfaces such as

tractor-trailer couplings, rail-wheel systems and other heavy

duty applications.

The invention also relates to compositions described above which include friction modifiers with high or very high and

positive coefficients of friction such that the coefficient of

friction is considerably higher than the solid lubricant.

The invention further relates to compositions comprising a

binding agent and a friction modifier with a very high and

positive coefficient of friction in a water medium.

BACKGROUND OF THE INVENTION

A conventional lubricant for tractor-trailer couplings,

rail-wheel systems and other heavy duty applications is grease.

However, grease has serious limitations for operation and for

environmental contamination. Following mating of the coupling

components after an application of grease, a large portion of the

grease is immediately lost due to difficulties of the grease adhering to the coupling or rail. The lost grease falls on parts

of the vehicle piping and on the ground as a non-biodegradable

contaminant. Further, grease dissipates during use causing its

lubricating performance to deteriorate to potentially hazardous conditions. This known dissipation thereby encourages users to

apply excessive amounts of grease to compensate. Moreover,

exposed couplings, rails or wheels can become contaminated with

dust and grit thereby forming a grinding compound which causes

rapid wear to the bearing plates unless they are cleaned and regreased before use.

Typically, grease is reapplied every week or two. Its removal prior to regreasing is accomplished with high pressure

steam causing it to be flushed into the water supply.

Alternatively, stronger solvents may be used to remove grease

which are even more unacceptable from an environmental

standpoint .

Lubricant compositions comprising, inter alia , solid

lubricants and polymer media have been used as alternatives to

grease and these lubricants have the advantage of forming a film on the metal surface, and accordingly, better adhesion. However,

as the lubricant dissipates, the polymer medium may still

contaminate the environment .

Aqueous lubricant compositions have been suggested but

discarded as impractical in Swiss patent specification CH 669,207

A5, wherein a method of using an aqueous graphite dispersion for coating or painting sides of rails was discussed and discarded

as the aqueous dispersion is apparently easily removed. The

solution of CH 669,207 A5 is a composition which includes, inter

alia, a polymer resin which has the same drawbacks as other polymer media as discussed above.

It is recognized in U.S. Patents 5,173,204 and 5,308,516,

that when the co-efficient of friction increases with speed, it

is known as having a negative friction characteristic. The origin of much noise emission in steel rail-wheel transportation

systems can be directly attributed to the fact the negative

friction characteristic that under certain conditions arising in

use, the wheels of such systems do not always roll over the rails

but sometimes slide relative to them. This is most pronounced

on curves. An effective way to eliminate the squeaking and

chattering is by changing the friction characteristic from a negative one to a positive one. Hereinafter, the term "positive

friction" means that the coefficient of friction increases with

speed of sliding and a "high" coefficient of friction is greater

than 0.10.

Apart from reduced friction (and noise) and wheel-rail wear,

use of a friction modifier can prevent the initiation and growth

of short pitch corrugation by preventing or eliminating the

oscillatory motions, commonly known as roll-stick oscillations,

which are excited in the rail/wheel interface by the presence of

negative friction.

U.S. Patents 5,173,204 and 5,308,516, teach that in a rail-

wheel system, the lubricant composition should be applied to 25%

of all the wheels of a rail-wheel system. Considering that the effect is most pronounced on curves, a lot of lubricant, time and

effort is required in order to ensure that there is sufficient

lubricant.

SUMMARY OF THE INVENTION

The present invention provides water-based lubricant and

friction modifier compositions for heavy duty use with metal

applications such as tractor-trailer couplings or rail-wheel

systems that has improved adhesion characteristics. The

inclusion of a binding agent, defined below, in the lubricant,

or lubricant and friction modifier, composition helps to bind the lubricant and friction modifier to the coupling, rail or other surface. Therefore, the composition need not be applied as

frequently or in the same quantity and accordingly there will be

less lubricant and friction modifier lost and less environmental

contamination.

In another aspect, the invention also provides a water-based

lubricant composition which includes a wetting agent. The

inclusion of a wetting agent also helps to ensure that there is

better adhesion of the solid lubricant to the coupling, rail or

other surface and thus the solid lubricant may be better applied.

This invention is also directed to water based friction

modifier compositions that include a wetting agent.

In another aspect, the invention also provides a water-based

lubricant composition which may be applied to a rail at precise

areas identified as problem areas such as curves or inclines.

Due to this specific application at identified spots, the subsequent transfer from rail to wheel means that the lubricant

will be spread along the rail by movement of the wheels over the

rail but principally for the identified spots. The advantages of such precision application are that less lubricant, time and

effort are required in order to achieve the same results of

improved noise control, traction and reduced short pitch

corrugation.

In yet a further aspect, the invention provides a lubricant

composition which is easier to apply than previous compositions.

The lubricant composition is water-based which makes it easier

to apply as the binding agent absorbs the water present in the

composition and thus allows for quick adhesion to the metal

surface .

In one aspect of this invention, the composition comprises:

(a) at least about 24% by weight water medium;

(b) about 8% by weight binding agent; and

(c) at least about 2% by weight solid lubricant.

In another aspect the lubricant composition additionally

includes a friction modifier which exhibits improved high and

positive or very high and positive friction characteristics. The

composition allows for the solution to the steel-steel rolling-

sliding situation described above with respect to the prior

patents U.S. Patents 5,173,204 and 5,308,516 but with the added

benefit of the precision application, described above, namely,

that less lubricant, time and effort will be required to achieve

the same result set out in those patents.

Accordingly, in a further aspect, the invention provides a

lubricant composition comprising a water medium, solid lubricant,

binding agent and a friction modifier present such that the

coefficient of friction produced between steel bodies in rolling-

sliding motion lubricated using the said composition is greater

than 0.10 and wherein said coefficient of friction increases with

an increase in the relative speed of sliding movement between the

bodies .

According to a further aspect of the invention there is

provided a composition comprising:

(a) at least 60% by weight water;

(b) at least 5% by weight binding agent; and

(c) at least 3% by weight friction modifier;

wherein the composition has the characteristics of very high and

positive friction, with a coefficient of friction ranging from

0.45 at 2.5% creep up to 0.72 at 30% creep. This product is used

mainly to enhance traction of the locomotion wheels.

Further, according to the present invention, there is a

method of reducing noise in a steel rail-wheel system by applying

said lubricant, or lubricant and friction modifier, composition

to the surface of the rail whereby the lubricant composition is

effective to change the negative friction characteristics between

the rail and the wheel to a positive friction characteristic.

The present invention also provides compositions which are

capable of effectively reducing short pitch corrugation. This

is achieved by compositions having a high coefficient of friction

and positive friction characteristics.

The above compositions have the advantage of being

relatively non-polluting and economical in that the dispersal

means allows for isolated application of compositions to surfaces

which are targeted as problem areas.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS OF THE INVENTION

Generally the lubricant and friction modifier compositions

are water-based compositions consisting of water, a solid

lubricant, as required, a binding agent and, in some embodiments, a friction modifier and/or a wetting agent.

The lubricant and friction modifier compositions can be

formulated by selecting one or more solid lubricants and friction modifiers as required. Examples of solid lubricants and friction

modifiers can be found from, but are not limited to, the following lists.

Solid Lubricants

molybdenum disuphide graphite aluminum stearate zinc stearate carbon compounds (coal dust, carbon fibres, etc.)

The preferred solid lubricants are molybdenum disulphide and

graphite.

Friction Modifiers calcium carbonate magnesium carbonate magnesium silicate barium sulphate calcium sulphate asbestos

aluminum silicate silica amorphous silica naturally occurring silica slate powder diatomaceous earth ground quartz silica flour white lead basic lead carbonate zinc oxide antimony oxide dolomite calcium sulphite napthalene synemite polyethylene mica

The friction modifier, if any, preferably comprises a

powderised mineral. The friction modifier for a high and positive friction lubricant composition may have a particle size

in the range of about 0.5 microns to about 5 microns, and

preferably has a particle size in the range of about 1 micron to about 2 microns. A very high and positive friction modifier

composition may have a particle size of 10 microns.

The friction modifier should have a coefficient of friction

which is considerably higher than the coefficient of friction of the solid lubricant. The coefficient of friction values given

are those produced between steel bodies in rolling-sliding

contact. High and positive friction modifier compositions

produce a coefficient of friction which is greater than 0.10 and

wherein the said coefficient of friction increases with an

increase in the relative speed of sliding movement between steel

bodies. For very high and positive friction, the steel to steel

coefficient of friction for the lubricant composition according

to the invention should increase from about 0.45 to about 0.72

as creepage increases from about 2.5% to about 30%. Particular compositions contain friction modifiers but not solid lubricants

to create very high and positive friction characteristics.

The term binding agent herein is defined to mean a hydrophilic agent which absorbs water causing it to swell out

physically into particles of a shape capable of adhering to a

rail. The binding agent creates a continuous phase matrix which

is capable of binding solid lubricants, friction modifiers and other compounds to a metallic surface by dispersing the solid

lubricant or holding said solid lubricant in a discontinuous

phase matrix. The binding agent has rigidity such that when the

composition is placed on the metal surface, it has some structure and will maintain its integrity after the wheel goes over the

composition. Examples of binding agents include but are not

limited to clays such as bentonite (sodium montmorillonite) and

casine.

Also optionally are included preservatives, wetting agents

and additives to allow for mixing of the composition with grease

already on rail or coupling. Preservatives such as ammonia are

used for preserving the lubricant composition. Alcohols such as

butoxyethanol may also be used.

The term wetting agent used herein is defined to mean a flow

agent which permits the solid lubricant particles to be

surrounded by water within the matrix of the binding agent and

the solid lubricant. The wetting agent helps to reduce surface

tension and allows the solid lubricant to get into the cracks of the rails or other surfaces and also emulsifies the grease to

permit a good adhesion. An example of a wetting agent includes

but is not limited to nonyl phenoxypolyol .

Method of Preparation

Embodiments of the lubricant and friction modifier

compositions may be prepared according to the following method.

Under a high speed mixer slowly add to 35% of the water in a

mixing drum at room temperature, the binding agent (ie. Bentonite

(sodium montmorillonite)) and the wetting agent (ie. nonyl phenoxypolyol) . These components should be mixed well until

thick gel is formed. Continue to mix then add the balance of

ingredients in the following order: water (the remaining 65%),

ammonia, ether E.B. (if any) , any other liquids, solid lubricant

(ie. molybdenum) as required, and any other solids. These

components should be mixed thoroughly until smooth to ensure that

the solid lubricant is well dispersed.

The resulting composition is a thick, thixotropic liquid

which is jelly-like when standing but upon stirring or pumping

the viscosity decreases . The composition is a matrix whose

continuous phase is the binding agent and which also contains a discontinuous phase, the solid lubricant.

The above compositions may be applied to the coupling or

rail surfaces or the like by means of which will be recognized by one in the art such as pump or brush. The composition is

applied so that a film of the composition is evenly spread on the

rail. Said film is preferably a bead approximately one-eighth

of an inch in diameter.

The binding agent works by absorbing the water in the

composition. Over time the composition dehydrates to leave a

solid bead and thereby enhances adhesion of the lubricant and friction modifier to the rail over previously used greases or

polymer lubricant compositions. The binding agent additionally

keeps the lubricant and friction modifier dispersed even after

the wheel runs over the rail and also reduces reabsorption of water. Therefore, the composition is not easily removed by rain.

The desired coefficient of friction level for the

compositions of this invention are obtained by proportionately

mixing appropriate quantities of the friction modifier with a

high coefficient of friction and the solid lubricant with a very

low coefficient of friction. The solid lubricant and the

friction modifier are preferably present in the composition in

about equal amounts for the high and positive friction

compositions but may be present in differing amounts or with no

solid lubricant in order to achieve very high and positive

friction characteristics.

The following, given by way of example only and not intended

to be construed in a limitative manner, illustrate the

compositions according to embodiments of the invention.

EXAMPLE 1

A water-based, high and positive friction lubricant

composition comprises:

(a) 80.193% by weight water;

(b) 8.940% by weight sodium montmorillonite;

(c) 0.004% by weight ammonia;

(d) 0.002% by weight nonyl phenoxypolyol;

(e) 4.930% by weight molybdenum disulphide; and

(f) 4.93% by weight magnesium silicate;

and is prepared as described above.

A North American heavy haul railroad tested the above

composition and it was found that noise levels were reduced by

20 decibels at the top of the rail and at the gage face.

Similar lubricant compositions can be formulated by

selecting one or more alternative lubricants and friction

modifiers as disclosed above.

EXAMPLE 2

A water-based, very high and positive friction composition

(with no added lubricant) was prepared as described above using

the following components:

(a) 85.254% by weight water;

(b) 9.450% by weight sodium montmorillonite;

(c) 0.004% by weight ammonia;

(d) 0.002% by weight nonyl phenoxypolyol;

(e) 5.20% by weight anydrous aluminum silicate; and

(f) 0.09% by weight black iron oxide (as a colorant) .

The composition was tested and found to produce a positive

steel to steel friction characteristic in the range of 0 to 0.45

as the relative speed of sliding (creepage) increased from zero

to about 2.5%, rising to about 0.72 as creepage increased to

about 30%. These coefficient of friction levels are

substantially above steel to steel friction coefficient levels

obtained with conventional lubricants and above those of the

lubricant composition disclosed in U.S. Patents 5,173,204 and

5, 308, 516.

EXAMPLE 3

A water-based 5th wheel lubricant composition was prepared

as described above using the following components:

(a) 58.994% by weight water;

(b) 8% by weight sodium montmorillonite;

(c) 0.004% by weight ammonia;

(d) 0.002% by weight nonyl phenoxypolyol;

(e) 3% by weight butoxyethanol; and

(f) 30% by weight molybdenum disulphide.

When the lubricant was applied to the surface of a wheel

tread, the composition illustrated a marked improvement with

respect to adhesion of the lubricant . Tests have shown that the

fifth wheel composition lasts substantially longer or for

substantially more miles, in the order of 5-10 times longer than

conventional lubricants.

EXAMPLE 4

A water-based low coefficient friction lubricant composition

was prepared as described above using the following components:

(a) 79.502% by weight water;

(b) 12.621% by weight sodium montmorillonite;

(c) 0.004% by weight ammonia;

(d) 0.002% by weight nonyl phenoxypolyol;

(e) 3% by weight butoxyethanol; and

(f) 4.871% by weight molybdenum disulphide.

Similar testing was done to that described in example 1 and

with similar results being recorded.

It is understood that the invention has been disclosed

herein in connection with certain examples and embodiments.

However, such changes, modifications or equivalents as can be used by those skilled in the art are intended to be included. Accordingly, the disclosure is to be construed as exemplary,

rather than limiting, and such changes within the principles of

the invention as are obvious to one skilled in the art are intended to be included within the scope of the claims.