Patent Application
20080108530
The present invention relates to organometallic-soap-based silicone greases with high cohesion, in particular when cold. The invention also relates to the process for preparing said greases and to their use especially in the motor vehicle industry.
It is known that certain applications in the motor vehicle industry require the application of greases that are highly cohesive, in particular when cold, in order to avoid:
Examples of drive devices that will be mentioned include: a motor vehicle clutch cable, gearbox or starter.
It has been possible to establish in this field of the art a correlation between the behavior in mechanical tests reproducing skating phenomena between components involved in a drive device, and the flow threshold value of grease (or critical stress), such that avoidance of the abovementioned phenomena proceeds via improving the value of the cold threshold; in a manner that is known per se, the flow threshold may be measured, for example, using a controlled-stress rheometer capable of conditioning the grease at the temperature chosen for the test (in this case −40° C.).
The essential objective of the present invention is to propose a silicone grease that can have a high flow threshold, of greater than 600 Pa at −40° C.
Another objective is that of proposing a silicone grease that can have such a high cold flow threshold, without impairing the standard properties of the grease, in particular its consistency at an ambient temperature of 23° C., its low content of volatiles and good resistance to exudation (or bleeding) when hot, i.e. at a temperature in the range from 100° C. to 170° C.
Yet another objective is that of proposing such silicone greases that can be prepared via a process known to those skilled in the art and under economical cost price conditions.
One subject of the present invention is thus a high cohesion silicone grease comprising at least one oily diorganopolysiloxane polymer, 10% to 30% (weight percentage expressed relative to the weight of the grease) of organometallic soap(s) and 5% to 20% by weight of halogenated paraffin(s), said grease being characterized in that chloroparaffins are used consisting essentially of petroleum distillation-based linear hydrocarbons that have been chlorinated, belonging to one and/or other of the following three categories: C10-C13 short-chain chloroparaffins, C14-C17 medium-chain chloroparaffins and C18-C30 long-chain chloroparaffins, each of the abovementioned categories possibly having a weight percentage of chlorine in the range from 30% to 70%.
The oily diorganopolysiloxane polymers, which are the basic constituents of the greases, correspond to the general formula:
(R)3SiO[Si(R)2O]nSi(R)3
in which the symbols R, which may be identical or different, represent hydrocarbon-based radicals free of aliphatic unsaturations and containing up to 13 carbon atoms, and the symbol n represents any number ranging from 30 to 1500.
These linear polymers thus consist essentially, besides the end units, of a succession of units of formula (R)2SiO; however, the presence of a small amount of other units, such as those of formulae SiO2 and (R)SiO1.5, is not excluded in a proportion of up to 1% relative to the number of (R)2SiO units.
The hydrocarbon-based radicals represented by the symbols R are chosen from:
However, for each molecule of the polymers, at least 45% in numerical terms of all of the hydrocarbon-based radicals R are alkyl radicals. These diorganopolysiloxane polymers are oily liquids whose viscosities range (according to the nature of the radicals R and the values of n) substantially from 100 mPa.s to 500 000 mPa.s at 25° C. They are mostly industrially manufactured by silicone manufacturers; moreover, their preparation is given in the chemical literature, for example in French patents 978 058,1 025 150 and 1 108 964.
As a guide for the polymers that may be used, mention may be made of those represented by the following formulae:
(CH3)3SiO [Si(CH3)2O]n1 Si(CH3)3 (I)
(CH3)3SiO [Si(CH3)2O]n2 [Si(C2H5)(CH3)O]n′2 Si(CH3)3 (II)
(CH3)3SiO [Si(CH3)2O]n3 [Si(nC8H17)(CH3)O]n′3 Si(CH3)3 (III)
(CH3)3SiO [Si(CH3)2O]n4 [Si(nC12H25)(CH3)O]n′4 Si(CH3)3 (IV)
(CH3)3SiO [Si(CH3)2O]n5 [Si(C6H5)(CH3)O]n′5 Si(CH3)3 (V)
(CH3)3SiO [Si(CH3)2O]n6 [Si(C6H5)2O]n′6 Si(CH3)3 (VI)
(CH3)3SiO [Si(CH3)2O]n7 [Si(C6H2Cl3)(CH3)O]n′7 Si(CH3)3 (VII)
The values of ni and of n′i (i=1 to 7) vary, respectively, within the given ranges, such that the number of methyl radicals in each polymer molecule represents, as already indicated, at least 45% in numerical terms of all of the radicals attached to the silicon atoms of these polymers.
The oily diorganopolysiloxane polymers preferably used, alone or as a mixture, are those represented by formulae (III) to (VII).
Besides the oily diorganopolysiloxane polymers, the silicone greases according to the invention contain, as gelling agent, organometallic soaps.
The gelling agents used to form the grease may be fatty acid soaps. The saponifiable matter may be derived from higher fatty acids containing from 10 to 32 carbon atoms, these acids possibly being hydroxylated or nonhydroxylated and possibly being saturated or unsaturated.
Soaps of nonhydroxylated fatty acids are preferably used, especially such as: capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, myristoleic acid, palmitoleic acid, oleic acid, linoleic acid and erucic acid; fatty acids from cottonseed oil, palm oil and hydrogenated fish oil, optionally as a mixture, and/or glycerides thereof, for instance lard oil, beef oil, rapeseed oil, palm oil, menhaden oil or herring oil; acids derived from the oxidation of liquid petroleum and of waxes; resinous acids; heavy-oil acids; abietic acids; naphthenic acids; sulfonic acids.
The saponification agent used to make the soap may be a metallic Li, Na, K, Cs, Mg, Ca, Sr, Cd, Zn, Pb or Co compound and preferably an oxide, a hydroxide or a carbonate of one of the abovementioned alkali metals and alkaline-earth metals. Mixtures of soaps may also be used, and these soaps may be either prepared in situ or manufactured beforehand to form the grease.
Particular examples of soaps used alone or as mixtures are: the lithium soap of stearic acid; the lithium soaps of hydrogenated fish oil fatty acids; the sodium soap of stearic acid; the sodium soap of oleic acid; the potassium soap of oleic acid; the calcium soap of stearic acid; the barium soap of stearic acid; the barium soaps of mixed stearic and oleic acids; the composite lithium and sodium soaps of stearic acid.
The soaps that are especially suitable, used alone or as a mixture, are the lithium soap of stearic acid and the composite lithium and sodium soaps of stearic acid.
The soap content of the greases according to the present invention represents 10% to 30% by weight; it is recommended for this content to represent from 15% to 25% by weight.
Moreover, auxiliary additives, the aim of which is to facilitate the preparation of the greases (better dispersion of the charges, reduction of the blending time) and/or to improve their internal cohesion and/or to provide a coloration, may be incorporated with the oily diorganopolysiloxane polymers and the organometallic soaps. Additives that may be mentioned, as a guide, include: polyalkylene glycols; boric acid and alkyl borates; pentaerythritol; hydroxylated diorganopolysiloxane oils with a low viscosity ranging from 10 to 500 mPa.s at 25° C.; colored pigments. The total amount of these additives introduced, when they are used, is in the range generally from 1% to 8% by weight relative to the weight of the grease.
The chloroparaffins included in the constitution of the silicone greases according to the present invention may be chosen from many described and marketed organic compounds of this type.
It is known that such compounds are liquid at atmospheric pressure and at room temperature (23° C.); they have a viscosity in the range from 500 to 100 000 mPa.s, preferably ranging from 1000 to 20 000 mPa.s.
The Applicant has found that, under the conditions of the invention, the chloroparaffins used are preferably C14-C17 medium-chain and C18-C30 long-chain chloroparaffins with a weight percentage of chlorine in the range from 40% to 60%.
As specific examples of chloroparaffins that are especially suitable, mention may be made especially of the products sold by the company Ineos Chlor under the trade names: S54, S56, E56, M50, 42SS and 48.
The content of chloroparaffin(s) in the greases according to the present invention represents 5% to 20% by weight; it is recommended for this content to represent from 10% to 15% by weight.
The greases are prepared by melting/recrystallization of the soap in the oily diorganopolysiloxane polymer(s) and by incorporating the chloroparaffin(s) either before or after the melting/recrystallization step, but preferably after the step of melting/recrystallization and cooling of the grease. This procedure is performed in devices designed for the blending of viscous mixtures; thus, for example, blenders and mills are particularly suitable for this preparation. In a subsequent step, it is possible, if necessary, to mill the grease, for example working in a roll mill or in a colloidal mill, to adapt the rheology and/or the appearance of the grease to the desired applications.
The greases according to the present invention may have a high flow threshold, of greater than 600 Pa at −40° C., while at the same time affording desirable characteristics in terms, for example, of penetration, content of volatile compounds and exudation behavior.
These greases are successfully used as treating and/or protecting and/or lubricating agents in the field of moving metallic mobile components; since they have good cohesion, especially when cold, they consequently make it possible to avoid, inter alia, skating phenomena, especially when cold, between components involved in a drive device, for instance the components involved, in the motor vehicle field, in: a vehicle clutch cable, gearbox or starter.
The examples that follow illustrate the invention.
The formulation of this grease is given in table 1 below.
The greases were prepared with a DAC 150FV-K Speed-mixer™ blender (sold by the company Hauschild Engineering), starting with a grease premix composed of 35% by weight of lithium stearate and 65% by weight of oil H510V100. The chloroparaffin additive is added and the oil H510V100 completes the formulation so as to give a final lithium stearate content of 22.4% by weight and a final chloroparaffin content of 12% by weight.
The mechanical tests, performed with the grease prepared according to paragraph 1, on several drive configurations and on several starters, are positive: absence of skating at −40° C. and correct functioning of the starters when hot, on test benches.
It should be pointed out that, in this application, the grease is introduced into the coupling and uncoupling device connecting the starter itself to the combustion engine of a motor vehicle.
The preparation of other silicone greases according to the invention is illustrated below:
These greases:
It is clearly seen from the above table that the addition of the chloroparaffin-based additives allows the flow threshold of the control silicone grease to be substantially increased.
| Number | Date | Country | Kind |
|---|---|---|---|
| 0404793 | May 2004 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR05/00943 | 4/19/2005 | WO | 00 | 11/14/2007 |
