The present invention relates to the use of liquid compositions for the treatment of metal surfaces.
Specifically the invention relates to the use of compositions of fluorinated products soluble in fluorinated fluids, capable to protect from corrosion metallic parts for example bearings, bushings, etc.
The use of fluorinated compounds for surface treatments in general, to give oleo- and hydrorepellence to the substratum, is known in the prior art. Alternatively, also the use of specific coatings such as metal, polymeric coatings, etc., suitable to protect the treated surface, is known.
It is known that the protection against humidity or sea air/sea water for metals is a particularly critical problem, especially in the storage phase.
In U.S. Pat. No. 6,221,434 it is described a series of functional perfluoropolyether derivatives for the various kind surface treatment, in order to give oleo- and hydrorepellence. Tests carried out by the Applicant have pointed out that said derivatives, even though they show good water-repellent properties, are ineffective to protect metals from corrosion (see the Examples).
As regards the protective coating use of metal parts, one generally distinguishes between polymeric and metal coatings. The polymeric coatings have the drawback that when they are used in moving mechanical parts, and therefore subjected to friction and wear, deteriorate in the time.
The metal coatings obtained by surface melting of valuable alloys, see for example U.S. Pat. No. 4,943,485, have the drawback to be very expensive. Furthermore they are not generally appliable, for example when used in transformer lamellar packages they modify the nature itself of the lamellas.
The need was therefore felt to have available compositions of additives appliable by a simple process, quickly, for example, by dipping, spraying, etc., capable to protect the metals from humidity and sea air/sea water.
Liquid compositions solving the above technical problem have been surprisingly and unespectedly found by the Applicant.
An object of the present invention are non aqueous liquid compositions, clear at room temperature, comprising:
(A) A fluorinated compound having the following general formula (I)
T=(CH2CH2O)k, (C3H6O)k′ wherein
k and k′ are integers in the range 0-10, extremes included, preferably 0-4;
X, Y, X1, Y1, equal to or different from each other are independently the one from the other H; NO2; C1-C4 alkyl; C1-C4 alkoxy, with the proviso that at least one of X, Y, X1, Y1 is equal to NO2;
m′ and n′ are integers, selected so that the number average molecular weight of the perfluoropolyether chain formed by the units with m′ and n′ indexes is from 66 to 10,000, preferably from 300 to 4,000;
(B) a fluorinated fluid, liquid at room temperature, having boiling point in the range 50° C.-250° C., preferably 50° C.-130° C., selected from the compounds having one of the following structures, and/or their mixtures:
R′=—(O)n0—CnF2nH, n being an integer from 1 to 4, preferably 1 or 2; n0 is equal to 0, 1;
R is selected between —CnF2nH, —CmF2m+1; wherein
in the R, R′ end groups one fluorine atom is optionally substituted with one chlorine atom;
n in R is as defined in R′; m is an integer from 1 to 3;
Rf is selected from the following:
linear or branched perfluoroalkylene from 2 to 12 carbon atoms, containing at least one ether oxygen atom, in this case n0 in R′ is preferably equal to zero;
perfluoropolyoxyalkylene comprising units statistically distributed in the chain, selected from the following:
(CFXO) wherein X=F or CF3;
(CF2(CF2)dO) wherein d is an integer comprised between 1 and 3;
when Rf is perfluoropolyoxyalkylene n0 in R′ is preferably equal to 1;
Rf 1—O—RH (III)
Rf 1 is a linear or branched perfluoroalkyl radical, optionally containing ether oxygen atoms, preferably having CQF2Q+1 structure, wherein Q is an integer from 4 to 7;
RH is a CPH2P+1 hydrogenated radical wherein p is an integer from 1 to 10, preferably from 1 to 4.
In component (A) preferably m′ is an integer comprised between 0 and 80, extremes included; n′ is an integer comprised between 0 and 20, extremes included, with the proviso that both be not contemporaneously zero; the m′/n′ ratio preferably being from 0.5 to 4, n′ being different from zero. Still more preferably the number average molecular weight of the perfluoropolyether chain of component (A) formed by the units with m′ and n′ indexes is in the range 1,500-2,500.
Preferably in component (A) X=Y=X1=Y1=NO2 or X=X1=NO2 and Y=Y1=H; preferably k and k′ are equal to zero.
When component (B) is a formula (II) compound, and Rf is a perfluoropolyoxyalkylene, the unit (C3F6O) in Rf has the following meanings: (CF2CF(CF3)O), (CF(CF3)CF2O).
Preferably in the formula (II) compounds of component (B) R is selected from the following: —CF2H, —CF2CF2H, —CFHCF3.
Generally the formula (II) compounds have a number average molecular weight from 200 to 800, n0 of R′ is equal to 1, Rf is a (per)fluoropolyether chain, it has preferably one of the following structures:
when a is different from zero, then b/a is comprised between 0.3 and 10, extremes included; when a is equal to zero b is an integer as defined below;
2) —(CF2—(CF2)z′—CF 2O)b′—
wherein z′ is an integer equal to 1 or 2; b′ is as defined below;
when b and t are different from zero, r/b=0.5-2.0 (r+b)/t=10-30 and all the units with r, b, and t indexes are present;
or b=t=0 and r complies with the proviso mentioned below;
or b=0 and r and t are different from zero;
a, b, b′, r, t, are integers such that, or whose sum is such that the formula (II) compound containing the bivalent radical Rf has boiling point in the above range.
The liquid invention compositions have an amount of component (A) such that it is soluble in component (B) and the composition results clear at room temperature.
The component (A) amount, soluble in component (B), expressed in % by weight, is generally from 0.01% to 50%, preferably from 0.1% to 15%.
The formula (I) products can be synthesized starting from a bifunctional (per)fluoropolyether, having hydroxyl end groups, converted into the corresponding alkaline alcoholate, for example potassium, and then reacted with a halogen-substituted aromatic compound having the substituents X, Y or X1 and Y1 as above. See for example C. Tonelli, P. Gavezotti, E. Strepparola, Journal of Fluorine Chemistry 95 (1999) 51-70, herein incorporated by reference.
Examples of compound (B) preparation are described in the prior art in U.S. Pat. No. 3,704,214, U.S. Pat. No. 3,715,378, U.S. Pat. No. 5,969,192, and in patent application WO 96/22356.
For the protective treatment of metallic surfaces, the invention compositions are applied to the metal substratum, for example by dipping, spraying, spin coating. In particular the metal part to be protected is treated with the invention compositions, removing then the solvent for example by evaporation in the air and/or in a ventilated stove. The so treated metal can be used in the presence of water/humidity without showing corrosion phenomena.
It has been unexpectedly and surprisingly found by the Applicant that corrosion phenomena on the metallic surfaces treated with the present invention compositions do not even appear in the fog chamber test (see the characterization test reported in the Examples), even after residence times of the order of 300 hours and over.
The Applicant has found that other fluorinated additives used in the prior art for the metal treatment (see the comparative Examples) under the same conditions are not capable to protect from corrosion.
Generally after a time of 100 hours the metal surfaces treated with known fluorinated additives show corrosion phenomena in the above test. The results are still more unexpected if one considers that the invention fluorinated additives and those used in the comparative Examples show, on the treated metallic surfaces, substantially similar contact angle values against water, and that therefore the surfaces have comparable water-repellent properties.
With metals according to the present invention, materials are meant containing iron, such for example carbon steels, iron alloys, titanium alloys containing aluminum and vanadium, materials containing copper, etc.
The invention compositions also show the further advantage to be environmental safe since component (B) has an ODP equal to zero and a low GWP.
Optionally component (B) can be in admixture with perfluorooxyalkylene or perfluoroalkyl fluorinated fluids (Component (C)), liquid at room temperature, whose end groups optionally contain one chlorine atom at the place of one fluorine atom.
When the mixture of components (B) and (C) is used, the amount of component (C), expressed in percentage by weight with respect to (B)+(C), is from 0 to 50%, preferably from 0 to 30%. In this case the invention compositions have an effect on the GWP in function of the amount of (C).
The metal parts thus protected from corrosion with treatment with the invention compositions, show furthermore the advantage to be directly lubricated when used in mechanical systems wherein lubrication with (per)fluorinated fluids, for example oils or fluorinated greases, is required. In fact it has been found by the Applicant that it is not necessary to remove component (A) from the treated surface before lubrication since there is no interaction both of chemical nature and as regards the performances required in the use, between the protective agent and the lubricant.
Therefore with the invention compositions it is possible to avoid the protective agent removal before the piece lubrication. This allows to save on industrial scale, since one step is avoided, and to maintain on the piece the protection against corrosion.
A series of explaining examples follows which are not limitative of the invention.