Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Elemental metal or boron – or alloyed metal
Reexamination Certificate
2002-07-24
2004-10-19
McAvoy, Ellen M (Department: 1764)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Elemental metal or boron, or alloyed metal
C508S431000, C508S440000, C508S459000, C072S042000, C516S056000, C516S075000, C516S097000
Reexamination Certificate
active
06806238
ABSTRACT:
The present invention relates to the use of lamellar crystallites as extreme pressure additives in aqueous lubricants. It also concerns these lamellar crystallites, and their production.
Lubricants have to be used during operations for transforming and deforming metals, such as rolling, drawing or cutting. During such operations, which are carried out under very severe speed, pressure and applied force conditions, the coefficient of friction between the metal and the tool for carrying out the transformation/deformation is very high. This causes rapid wear of the tool surface. Such rapid wear is the cause of tool breakage and the appearance of superficial defects in the transformed/deformed metal. The use of a lubricant can considerably reduce this coefficient of friction, and thus the problems with wear and surface defects.
A number of different types of lubricant exist, namely oily and aqueous lubricants. The field of application of the first is more limited than the second, as under extreme conditions, oily lubricants are not capable of sufficiently compensating for the heating of the metal. This results in fusion, which welds the metal and tool together, such welding immobilises the assembly. The use of additives known as “extreme pressure” additives can delay the appearance of such phenomena.
However, under extreme conditions, aqueous lubricants are preferably used. One advantage of such lubricants lies in the fact that they can cool the metal surface because of the heat conducting capacity of water. For this reason, the disadvantages encountered with oil-based lubricants regarding heating are partially resolved. In contrast, the requirements for “extreme pressure” additives as regards getting to grips with the coefficient of friction and wear remain acute.
The present invention concerns the use of lamellar crystallites of micronic dimensions in aqueous lubricants as extreme pressure additives, comprising a stack of organic phases and aqueous solutions; said crystallites are dispersed in the aqueous lubricant.
It has ben established that such lamellar crystallites, with a length of 100 &mgr;m or less, a width of 30 &mgr;m or less and with a thickness of 200 nm or less, come into contact with the surface of the metal to be transformed, and they encourage lubrication as the lamellar crystallites slide with respect to each other during the transformation/deformation operation.
Further, heating of the metal surface is not observed because of the aqueous phase in witch the lamellar crystallites are dispersed.
Other advantages and characteristics of the invention will become clear from the following description and example.
It should be noted that the accompanying figure shows a photograph taken using transmission electron microscopy (Cryo-TEM; scale of the photograph: 2 &mgr;m). It shows the lamellar crystallites of the invention.
Thus, in a first aspect, the invention concerns the use, as an extreme pressure additive employed in aqueous lubricants used for deforming or transforming metals, of lamellar crystallites with a length (L) in the range 0.1 &mgr;m to 100 &mgr;m, a width (l) in the range 0.5 &mgr;m to 30 &mgr;m and with a thickness (e) in the range 5 nm to 200 nm, comprising a stack of organic phases (O) and aqueous solutions (A) in the order O/[A/O]
n
, n being a whole other than 0 and such that the thickness of the stack is 5 nm to 200 nm, the organic phases comprising:
i) at least one acid selected from:
saturated or unsaturated carboxylic acids containing at least 5 carbon atoms;
acid phosphate esters with formula (RO)
x
—P(═O)(OH)
x′
, in which formula R is a hydrocarbon radical, optionally polyalkoxy, x and x′ being equal to 1 or 2, provided that the sum of x and x′ is 3;
said acid optionally being neutralised by an organic or mineral base; and at least one metal in the form of a multivalent ion; or
ii) at least one polyoxyalkylene block polymer exhibiting a cloud point.
In a second aspect, the invention is constituted by such lamellar crystallites.
In a still further aspect, the invention is costituted by the production of lamellar crystallites.
In a first variation in producing the lamellar crystallites of the invention, and when the lamellar crystallites comprise organic phases i), the process consists of bringing a solution or a dispersion comprising the acid, which may be neutralised into contact with the metal in the ionic and/or metallic form.
In a second variation in producing the lamellar crystallites of the invention, and when the lamellar crystallites comprise organic phases ii), an aqueous mixture is prepared comprising the polymer, then the temperature of the mixture is increased locally to a point above the cloud point of the block polymer. More particularly, this temperature increase is carried out close to the metal surface to be treated/deformed, in particular by the release of the heat resulting from friction or deformation of the metal.
The lamellar crystallites will be described first for clarity.
As indicated above, the length of said lamellar crystallites is in the range 0.1 &mgr;m to 100 &mgr;m. Preferably, the length of the lamellar crystallites is in the range 0.5 &mgr;m to 20 &mgr;m.
Further, the width of the lamellar crystallites is between 0.5 &mgr;m and 30 &mgr;m. More particularly, the width of the lamellar crystallites is in the range 0.5 &mgr;m to 10 &mgr;m.
Finally, the thickness of the lamellar crystallites is in (he range 5 nm to 200 nm, preferably in the range 10 nm to 100 nm.
The dimensions of the lamellar crystallites indicated above correspond to mean values. In other words, there exists a distribution of lamellar crystallite sizes with the mean located in the ranges given above.
The dimensions of the lamellar crystallites are measured by transmission electron microscopy of a sample that is vitrified cryoscopically (Cryo-TEM—see O. Aguerre-Chariol, M. Deruelle, T. Boukhnikachvili, M. In, N. Shahidzadeh, “Cryo-MET sur échantillons vitrifiés: principes, applications aux émulsions et dispersions de tensioactifs” [Cryo-TEM on vitrified samples principles, applications to surfactant dispersions and emulsions], Proceedings du Congrés Mondial de l'Emulsion, Bordeaux, France (1997)).
More particularly, the lamellar crystallites are constituted by a stack of organic phases (O) and aqueous solutions (A) in the order O/[A/O]
n
, n being a number other than 0 and such that the thickness of the stack is 5 nm to 200 nm.
More particularly, n is a positive whole number that can be at most 100. Preferably, n is a whole number in the range 1 to 20.
In a first embodiment of the present invention, the lamellar crystallites comprise organic phases constituted by at least one acid and at least one metal in the form of a multivalent ion.
The acid forming part of the composition of said phases is selected from:
saturated or unsaturated carboxylic acids containing at least 5 carbon atoms;
acid phosphate esters with formula (RO)
x
—P(═O)(OH)
x′
, in which formula R is a hydrocarbon radical, optionally polyalkoxy, x and x′ being equal to 1 or 2, provided that the sum of x and x′ is 3;
Further, said acid is optionally neutralised by an organic or mineral base.
It should be noted that the organic phase can comprise either a single type of acid or a mixture of these two types. In each of these types, they can also comprise a single acid or a mixture of a plurality thereof.
More particularly, the carboxylic acids that can be used in the composition of the organic phases of the lamellar crystallites of the invention are selected from saturated or unsaturated mono- or poly-carboxylic acids containing 5 to 40 carbon atoms.
Preferably, they have the following formula:
R
1
—COOH;
in which formula R
1
represents a linear or branched alkyl radical or an alkenyl radical containing one or more ethylenically unsaturated bonds, containing 5 to 40 carbon atoms (including the carbon atom of the carboxyl group), optionally substituted with one or more hydroxyl radicals and/or at least one
Georgees Jean-Marie
Lorentz Gilles
McAvoy Ellen M
Rhodia Chimie
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