Anti-lubricant compositions

Details Anti-lubricant compositions Anti-lubricant compositions

1999-11-22

2004-08-31

Moore, Margaret G. (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

Reexamination Certificate

active

06784244

ABSTRACT:

This invention is concerned with anti-lubricant compositions, and relates in particular to such compositions which may be of use in the joint-producing methods described in our International Patent Application PCT/GB 91/00,950 (now published as WO 91/19,589) and a number of subsequent Applications.
In the Specification of the aforementioned PCT Application [P1220: Trib-joints] there is described and claimed a method of securing against lateral motion two bodies held in face to face asperity contact, thereby to make a join between the two bodies, in which method there is inserted into the interface between the two bodies a material that on minimal initial lateral relative motion of the two surfaces promotes rapid but controllable “galling” between the two surfaces, this galling binding the surfaces against further such motion. The material inserted into the interface, and which causes the galling, is variously referred to as a galling agent, gall promoter, gall enhancer, or anti-lubricant, and the present invention relates to particularly preferred such anti-lubricants, and to compositions thereof. Variants of this are described in the Specification of our International Patent Application PCT/GB 93/00,046 (now published as WO 93/13,908) [P1284: Trib-bond].
The method of the two aforementioned Specifications is very suitable for joining bodies that fit well together, but not always so good at joining bodies that don't, and in the Specification of our International Patent Application PCT/GB 94/00,869 (now published as WO 94/25,216) [P1286: Trib-paste] there is described and claimed another variant of the method, this variant being especially adapted for use with “ill”-fitting joints—that is, joints where it is thought that the two faces to be joined might not be in good face-to-face asperity contact, so there is a gap therebetween—in which there is employed to fill the gap a composition comprising a multiplicity of small metal particles surrounded by or coated with a gall-promoting fluid that acts as a viscous binder.
In the aforementioned WO 91/19,589 and WO 93/13,908 Specifications the preferred described anti-lubricants are said generally to be liquid, especially such a material that appears in use to act as an oxygen scavenger when placed in contact with the material of the two bodies to be joined together. Typical examples of these materials are said to be the range of poly-dimethylsiloxane and polymethylhydrogensiloxane liquids of viscosities generally up to 100 c/s (volatile versions of similar siloxanes can be used where the surplus liquid that exudes from the joint naturally evaporates after the joint is formed). The same materials are identified in our aforementioned WO 94/25,216 Specification, while others are there described as being similar siloxanes but with amino active side groups that are able to cross link, or “vulcanise”, after the joint is made so as to form a synthetic rubber cocoon, and so prevent any small loose unbonded metal particles breaking loose in service.
Both the liquid anti-lubricant materials and the metal-particle-containing compositions of our aforementioned International Applications have proved satisfactory, but nevertheless there are occasions where the joint to be made is constructed from well-fitting parts, so that there is no need for the metal-filled viscous compositions of the latter, and yet the typically more liquid materials of the former are somewhat too fluid—or, rather, surface active—and tend to creep or even to flow out from their application site (which is not only wasteful of material, but means there is a risk of the anti-lubricant turning up where it is not wanted, which might even result in some damage being caused). It would seem that this dilemma might be solved by the provision of the anti-lubricant in the form of a composition that is a viscous fluid, a paste, a gel or even a semi-solid rubber-like material, and it is broadly this that the present invention proposes. More specifically, the invention suggests the use as the anti-lubricant of a composition of two or more siloxanes chemically reacted together to form a desirably thick viscous fluid, paste, gel or rubbery solid reaction product, the resultant reaction product being admixed with a more liquid, mobile siloxane that itself has anti-lubricant properties, this more mobile siloxane, which may be either one of the two reacted together or a completely different one, is immobilised—stably dispersed—within the reaction product (and not only provides the required anti-lubricant property but may also be used to modify the final “viscosity” of the composition).
In one aspect, therefore, the invention provides a silicone composition having anti-lubricant properties and thus being of use in the promotion of galling between two gallable surfaces, the composition comprising a stable dispersion of a relatively mobile gall-promoting silicone “immobilised” within a matrix made of the cross-linked reaction product of at least two polyfunctional siloxanes and having the form of a viscous fluid, a paste, a gel or a rubbery solid.
The invention involves the utilisation of a silicone composition having anti-lubricant properties and thus being of use in the promoting of galling between two gallable surfaces. The concept of galling agents, anti-lubricants, and the promotion or enhancement of galling is well-known from our aforementioned Specifications, and needs no further comment at this time, save perhaps to summarise things by saying that certain types of metal joint, typically that having a form similar to a violin string tuning peg stuck in its hole in the scrolled end of the neck, can be made to bind together by material from one surface being transferred to the other, to make a lump rather like a gall (as seen on plants), this gall causing the joint surfaces to jam one onto the other, and to observe that gall formation can be promoted or enhanced by certain chemicals that seem to have the opposite effect to ordinary lubricants.
The composition of the invention contains the cross-linked reaction product of at least two different monomeric units each of which is itself a polyfunctional siloxane polymer (the product is thus a co-polymer). These materials are polyfunctional in that each contains at least two, and preferably at least three, functional groups (which may be the same or different) by which it can react with, and so attach itself to, the other to form a loose three-dimensional matrix capable of holding the relatively mobile gall-promoting silicone therewithin. Moreover, they are siloxanes—that is, they are themselves silicone polymers made up of many units derived from moieties of the type
wherein R
1
is an alkyl group, and R
2
is the same or a different alkyl group (the preferred alkyl group R
1
and R
2
is the methyl group); these siloxane starting materials are themselves conveniently prepared by reacting corresponding compounds wherein some of the R groups are hydrogen with the donors of the required functional groups. The more useful starting siloxanes seem to be those of relatively limited reactivity, and those of relatively low molecular weight, and thus relatively short chain length (the number of the above moieties in each unit is conveniently, but not necessarily, from below 10 to above 300.
As to the functional groups, these can, within reason, be almost any set of groups capable of reacting one with another to form the desired polymeric product. One suitable pair of such groups is amine and dicarboxylic anhydride,
which react together, two amine to one anhydride, to form amide linkages
many of which will result in several molecules being cross-linked eventually to form a matrix having a complex dimensional structure.
Depending upon the polyfunctionality of the monomers chosen, the reaction product may be a linear polymer and yet, by virtue of the shape and 3D nature of the monomers, have a 2D or even 3D shape of its own, or it may be a 2D macromolecule, rather like a net, or a 3D macromolecule like a sponge. Moreove

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