Solid anti-friction devices – materials therefor – lubricant or se – Lubricants or separants for moving solid surfaces and... – Organic compound containing boron
Reexamination Certificate
2000-06-28
2002-04-16
Howard, Jacqueline V. (Department: 1762)
Solid anti-friction devices, materials therefor, lubricant or se
Lubricants or separants for moving solid surfaces and...
Organic compound containing boron
C508S380000, C508S539000
Reexamination Certificate
active
06372697
ABSTRACT:
The present invention relates to the use, as an additive allowing the adhesion of a brass-plated steel wire and rubber, of an aqueous suspension comprising at least one compound such as a cobalt and/or nickel salt of a saturated or unsaturated carboxylic acid (i) or of a phosphate ester (ii) or of a cobalt and/or nickel boracylate; and at least one surfactant, in a drawing lubricant.
The invention similarly relates to the use, as a drawing lubricant additive for a brass-plated steel wire, of such an aqueous suspension.
In addition, the invention relates to an aqueous suspension comprising at least one compound such as a cobalt and/or nickel salt of a saturated or unsaturated acid (i), of a phosphate ester (ii) or of a cobalt and/or nickel boroacylate; and at least one nonionic or anionic surfactant; the weight ratio of compound (i), (ii) and/or (iii) to the surfactant being between 0.5 and 10; as well as to processes for obtaining it.
The field of the present invention thus essentially forms part of the tyre industry and in particular the preparation of tyres. More particularly, the present invention relates to improving the adhesion of rubber and of the metal cord used to reinforce tyres. This metal cord consists of several wires of small diameter, cabled together and then woven so as to form a mesh which is then incorporated into the rubber.
Generally, the cabled wire is based on steel coated with brass, so as to facilitate the adhesion between the cord and the polymer matrix, This happens because the copper in the brass reacts with the sulphur which is used as the rubber vulcanizing agent. In addition, the ductile nature of brass facilitates deformation of the brass-plated steel in the drawing die.
This solution is very satisfactory, at least as regards the initial adhesion, However, a degradation of the properties of tyres thus equipped, over time, has been observed, due in particular to a migration of the zinc under the effect of the external conditions (humidity, presence of sodium chloride). Effectively, zinc diffuses into the rubber and creates zones rich in zinc oxide. This zinc oxide-then becomes converted into zinc hydroxide which is fragile, as a consequence of which it degrades the mechanical properties of the tyre.
It has been considered to replace brass with a more complex, bilayer alloy obtained, before drawing, by electroplating. This alloy comprises a first layer based on zinc and 1% cobalt; the second based on nickel and 20% zinc. The major drawback of this method is that it replaces the layer of brass, which has many advantages during the drawing operation. In fact, the operation for drawing the cord coated with this bilayer system is made very complex. Specifically, whereas the drawing of brass-plated steel wires conventionally takes place at a rate of about 1000 m/minute, with the dies being worn out every 2000 km, steel wires coated with the bilayer system can only be drawn at rates of about 700 m/min and the dies wear out every 0.2 to 100 km (G. Orjeia, S. J. Harris, M. Vincent, F. Tommasini; Summary Report on Brite-Euram Project BREU-0424, KGK Kautschuk Gummmi Kunststoffe 50 -Jahrgang, No. 11/97; 778-785). Finally, the operation for drawing wires coated with the bilayer system is not industrial.
The subject of the present invention is to propose another route for treating brass-plated steel wires, with the aim of improving the adhesion between the cords and rubber during the preparation of tyres.
These aims and others are achieved by the present invention, a subject of which is thus the use, as an adhesive for a brass-plated steel wire and rubber, of an aqueous suspension comprising at least one compound such as a cobalt and/or nickel salt of a saturated or unsaturated carboxylic acid (i) or of a phosphate ester (ii) or of a cobalt and/or nickel boroacylate; and at least one nonionic or anionic surfactant; the weight ratio of compound (i), (ii) and/or (iii) to the surfactant being between 0.5 and 10.
The process according to the invention is particularly simple since the said suspension is added to the lubricant solution used during the wire-drawing operation.
In addition, the advantage provided by brass during the drawing operation is retained. Thus, the conventional and industrial drawing conditions can still be applied.
Finally, the process according to the invention is highly efficient since, after the drawing operation, it is found that the wire has cobalt or nickel at its surface. The consequence of this is to improve the resistance of the adhesion to ageing of the mesh comprising the woven cords.
It should be noted that the addition of the cobalt or nickel compound to the lubricant solution used during the drawing could not come about in an obvious manner.
Specifically, the lubricant solutions conventionally used during drawing are based on cobalt-and nickel-complexing agents. Thus, it is observed that a suspension of a cobalt or nickel compound gives, within a few minutes, after it has been placed in contact with the lubricant solution, a precipitate which separates out by settling, and which makes the resulting suspension unusable since its constituent lubricant bases have been depleted.
On the other hand, it has been found, surprisingly, that the suspension according to the present invention, when added to a lubricant solution comprising cobalt- or nickel-complexing agents, does not result in the appearance of such a precipitate. In addition, in particular in the case of cobalt and/or nickel salts, the resulting suspension is in the form of a slightly opalescent suspension, which has no flocs visible to the naked eye, is stable and does not separate out by settling.
It has similarly been found, entirely unexpectedly, and this constitutes, as indicated previously, another subject of the invention, that an aqueous suspension comprising at least one cobalt and/or nickel compound as defined above and at least one nonionic or anionic surfactant, the weight ratio of the compound to the surfactant being between 0.5 and 10, had a lubricant action during the drawing operation. Specifically, it has been found that the consumption of drawing dies was lower when the suspension according to the invention was present in the drawing lubricant.
However, other advantages and characteristics of the present invention will emerge more clearly on reading the description and the example which follow.
For reasons of simplification of the description of the invention, the suspension will first be described, along with its production.
As has been mentioned previously, the suspension used in the invention is based on a cobalt and/or nickel compound.
It should be noted that, in the text hereinbelow, the compounds based on cobalt or nickel will be referred to cobalt
ickel, it being understood that this name applies to either of the metals, as well as to their combination.
In one particularly advantageous embodiment of the invention, the metal used is cobalt.
According to a first variant (i) of the invention, the aqueous suspension is based on at least one cobalt
ickel compound which is a carboxylic acid salt.
According to one specific embodiment of the invention, the cobalt
ickel salt of carboxylic acid is insoluble in aqueous media.
More particularly, the salt is derived from a saturated or unsaturated carboxylic acid comprising 5 to 40 carbon atoms.
Preferably, the acid corresponds to the 5 following formula:
R
1
—COOH
in which formula R
1
represents a linear or branched alkyl or alkenyl radical with one or more ethylenic unsaturations, containing from 5 to 40 carbon atoms (the carbon atom of the carboxylic group being included), optionally substituted with one or more hydroxyl radicals and/or a carboxylic function.
According to one advantageous embodiment of the invention, the suspension comprises a salt of an acid corresponding to the abovementioned formula, in which R
1
represents an alkyl radical comprising 7 to 30 carbon atoms, optionally substituted with one or more hydroxyl radicals and/or a carboxylic function.
It should be noted that the second carboxyl
Lannibois-Drean Hélène
Lorentz Gilles
Burns Doane Swecker & Mathis L.L.P.
Howard Jacqueline V.
Rhodia Chimie
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