Metal treatment – Process of modifying or maintaining internal physical... – Processes of coating utilizing a reactive composition which...
Reexamination Certificate
2003-01-31
2004-03-16
Green, Anthony J. (Department: 1755)
Metal treatment
Process of modifying or maintaining internal physical...
Processes of coating utilizing a reactive composition which...
C106S014120, C106S014440, C148S243000, C148S253000
Reexamination Certificate
active
06706123
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the well known general field of phosphate conversion coating of metals, particularly to the type of phosphate conversion coating known as iron side or non-crystalline conversion coating that is formed on predominantly ferriferous surfaces from a working phosphating composition that does not contain any substantial amount of any divalent cations that form insoluble phosphates, for example, zinc, nickel, cobalt, manganese, calcium, magnesium, or the like. For brevity hereinafter, this type of coating or of composition for forming is called simply iron phosphate or a grammatical variation thereof. The invention relates still more particularly to an aqueous liquid concentrate that can be converted to a complete working liquid iron phosphating composition by dilution with water only.
It is known that many iron phosphating processes are subject to the disadvantage of flash rust(ing) on or of the freshly phosphated surface within a few minutes of emergence of the phosphate coated surface from the rinses following phosphating. It has also been known that addition of an aromatic carboxylic acid, particularly benzoic acid, to a working iron phosphating liquid composition substantially mitigates the likelihood of such flash rust formation. However, the concentration of aromatic carboxylic acid required to produce this effect is fairly close to the solubility of aromatic carboxylic acid in a typical working iron phosphating composition. Therefore, a single package concentrate with as much as even twice the desired concentrations of all ingredients of a working iron phosphating composition that contains a flash rust-inhibiting concentration of dissolved aromatic carboxylic acid has not heretofore been possible. In order to use aromatic carboxylic acid in a working iron phosphating composition for effectively inhibiting flash rust, it has been necessary to supply aromatic carboxylic acid in a separate package from the other ingredients of a concentrate iron phosphating composition. This need for two packages is regarded as an inconvenience by many users and increases the chances that the optimum ratio between dissolved aromatic carboxylic acid and other constituents of a working iron phosphating composition will not be maintained.
Accordingly, a major object of this invention is to provide a single package concentrate iron phosphating composition that makes it possible to obtain the advantages of a flash rust-inhibiting concentration of aromatic carboxylic acid in a working iron phosphating composition without requiring addition of any substance other than water to the concentrate. Other alternative and/or more detailed objectives will be apparent to those skilled in the art from the description below.
Except in the claims and the operating examples, or where otherwise expressly indicated, all numerical quantities in this description indicating amounts of material or conditions of reaction and/or use are to be understood as modified by the word “about” in describing the broadest scope of the invention. Practice within the numerical limits stated is generally preferred. Also, throughout this description, unless expressly stated to the contrary: percent, “parts of”, and ratio values are by weight; the term “polymer” includes “oligomer”, “copolymer”, “terpolymer”, and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members of the group or class are equally suitable or preferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or of generation in situ by chemical reactions specified in the description, and does not necessarily preclude other chemical interactions among the constituents of a mixture once mixed; specification of materials in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole (any counterions thus implicitly specified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to the objects of the invention); the term paint and all of its grammatical variations are intended to include any similar more specialized terms, such as lacquer, varnish, electrophoretic paint, top coat, color coat, radiation curable coating, or the like and their grammatical variations; and the term “mole” means gram-mole and the term itself and its grammatical variations may be applied to elemental, ionic, and any other chemical species defined by number and type of atoms present, as well as to compounds with well defined molecules.
BRIEF SUMMARY OF THE INVENTION
It has surprisingly been found that a dispersion of aromatic carboxylic acid in the other ingredients of an iron phosphating concentrate composition can be provided with sufficient stability to have practical value as a single package concentrate. One embodiment of the invention is a process for making such a stable dispersion. Another embodiment is such a stable dispersion itself, and still another embodiment is a process of using a working composition made from such a stable dispersion for phosphating.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
A concentrate composition according to the invention preferably comprises, more preferably consists essentially of, or still more preferably consists of, water and the following components:
(A) a component of dissolved phosphate anions;
(B) a component of sufficient dissolved acid to give the concentrate composition itself and a working composition made by diluting the concentrate composition with water only, an acidic pH value;
(C) a component of dispersed aromatic carboxylic acid; and
(D) a component of viscosity increasing agent that is not part of any of components (A) through (C) as recited immediately above; and, optionally, none, one or more of dissolved aromatic carboxylic acid and the following components:
(E) a component of phosphating accelerator that is not part of any of components (A) through (D) as recited immediately above;
(F) a component of dissolved fluoride ions that are not part of any of components (A) through (E) as recited immediately above;
(G) a component of chelating agent that is not part of any of components (A) through (F) as recited immediately above;
(H) a component of acidity adjustment agent that is not part of any of components (A) through (G) as recited immediately above; and
(J) a component of one or more surfactants that are not part of any of components (A) through (H) as recited immediately above.
In a composition according to the invention, component (A) preferably, at least for economy, is sourced to a composition according to the invention by at least one of orthophosphoric acid and its salts of any degree of neutralization. Component (A) can also be sourced to a composition according to the invention by pyrophosphate and other more highly condensed phosphates, including metaphosphates, which tend at the preferred concentrations for at least working compositions according to the invention to hydrolyze to orthophosphates. However, inasmuch as the condensed phosphates are usually at least as expensive as orthophosphates, there is little practical incentive to use condensed phosphates, except to prepare extremely highly concentrated liquid compositions according to the invention, in which condensed phosphates may be more soluble.
Whatever its source, the concentration of component (A) in a concentrate composition according to the invention, measured as its stoichiometric equivalent as H
3
PO
4
with the stoichiometry based on equal numbers of phosphorus atoms, preferably is at least, with increasing preference in the order given, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10.0, 10.5, 11.0, 11.3, or 11.6% and independently
Fristad William E.
Saad Karim I.
Cameron Mary K.
Green Anthony J.
Harper Stephen D.
Henkel Kommanditgesellschaft auf Aktien
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