Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2000-12-06
2003-05-06
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C106S014120, C106S014140, C106S287170, C106S287220, C428S413000, C428S416000, C523S457000, C523S458000
Reexamination Certificate
active
06558796
ABSTRACT:
FIELD OF THE INVENTION
The invention concerns aqueous coating compositions with aluminum flakes and phosphonic acid derivate based passivator resin.
BACKGROUND OF THE INVENTION
In principle, the problem when using metallic special-effect pigments, particularly aluminum pigments in waterborne coatings, is that the aluminum pigments react with the water to form aluminum hydroxide, with the generation of hydrogen. It is necessary, therefore, to stabilize these pigments in aqueous media. Commercial aluminum pigments for aqueous systems are, therefore, generally chromated, phosphated or coated with silica or polymer. Moreover, the aluminum pigments may be stabilized by passivators also present in the coating agent. This is advantageous and necessary, particularly in those fields of application where a relatively long storage time of the waterborne coating agents, e.g., a long term storage stability of about 12-24 months in vehicle refinishing, is required.
Various possibilities of stabilizing/passivating aluminum pigments in aqueous systems are known in the prior art. U.S. Pat. No. 4,675,358 discloses coating compositions employing phosphoric acid compounds, which are reaction products of an addition polymer with a hydroxyl group, a monomeric alcohol and a phosphoric acid derivate. Such compositions are not very hydrolytically stable. WO-A-96/08518 (U.S. Pat. No. 5,429,674) describes N-acyl aminomethylene phosphonates and derivatives and their use in waterborne coatings. Such compositions have limited compatibility with other binders and limited durability because of N-containing linkages. EP-A-391 230 (U.S. Pat. No. 5,034,556) discloses compounds which are the reaction product of an alpha-aminomethylene phosphonic acid with an epoxy group of a compound containing at least one epoxy group. Such reaction products have limited end use in water-borne compositions that are anionically stabilized since the amino groups destabilize the coating composition. U.S. Pat. No. 5,151,125 discloses aqueous metallic coating compositions comprising acrylic copolymers prepared by copolymerizing an ethylenic unsaturated monomer and a phosphate monomer to reduce the gassing of aluminum flakes. Such compositions have limited hydrolytic stability and limited effectiveness. EP-A-170 474 (U.S. Pat. No. 4,621,112) discloses reaction products of compounds having a phosphoric acid group —O— PO(OH
2
) with compounds having an epoxy group. Such reaction products only give limited gassing stability. WO-A-99/06450 describes aqueous coating compositions with passivator compounds based on a reaction product of a phosphonic acid derivate and a hydroxy-functional addition polymer. These formulations don't show a good balance between gassing performance and final color stability.
The object of the invention was, therefore, to overcome the disadvantages of the prior art and to provide aqueous coating compositions containing metallic pigments, which compositions have reproducibly good gassing stability, even after prolonged storage, without adversely affecting color properties of the coatings obtained therefrom. Coatings obtained from the coating compositions should exhibit no change of color shade and no impairment of brightness and metallic flop.
SUMMARY OF THE INVENTION
The object was achieved by aqueous coating compositions that contain reaction products of phosphonic acid derivatives and epoxy compounds as passivator component for the metallic pigments.
The present invention is directed to aqueous coating compositions comprising:
A) at least one reaction product of
(a) 5 to 95 weight percent, preferred 10-60 weight percent, of at least one phosphonic acid derivative selected from compounds I and II
wherein R
1
is selected from the group consisting of H or O=P(OH)
2
; R
2
and R
3
are independently selected from the group consisting of H, OH and an aliphatic, cycloaliphatic or aromatic substituent having 1 to 25 carbon atoms and optionally up to 10 heteroatoms of at least one of oxygen and phosphorus; and R′ is selected from the group consisting of an aliphatic, cycloaliphatic or aromatic substituent having 1 to 25 carbon atoms and optionally up to 10 heteroatoms of at least one of oxygen and phosphorus;
(b) 5 to 95 weight percent, preferred 40-90 weight percent of at least one compound having at least two epoxy groups and a number average molecular weight Mn of 300 to 5000 g/mol; and
(c) 0 to 90 weight percent of a compound having one epoxy-functional group, wherein the proportions by weight of components (a), (b) and (c) total 100 weight percent; and
B) at least one metallic pigment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
It was surprisingly found that the above described hydrophobic-substituted phosphonic acid based compounds A) are particularly effective for inhibiting the corrosion of metallic pigments in aqueous coating compositions and that aqueous coating compositions containing the phosphonic acid based compounds show a very good balance between antigassing performance and appearance as well as color properties of the applied coatings.
In a most preferred embodiment, the present invention is directed to aqueous coating compositions comprising
A) 0.1-5 weight percent, preferred 0.3-3 weight percent of at least one reaction product specified above,
B) 0.5-30 weight percent, preferred 1-15 weight percent of at least one metallic pigment,
C) 1-30 weight percent, preferred 5-25 weight percent of at least one film forming binder,
D) 15-85 weight percent, preferred 40-80 weight percent of water and optionally
E) 1-25 weight percent, preferred 5-12 weight percent of pigments, which are different from component B), organic solvents and/or additives which are conventionally used in coating compositions, wherein the proportions by weight of component A), B), C), D) and E) total 100 weight percent.
Component A) of the coating compositions according to the invention are reaction products of the components a), b) and optionally c). Preferred components A) have a number average molecular mass Mn of 400-20000 g/mole, most preferably 600-5000 g/mole and an acid value of 25-300 mg KOH/g, most preferably 40-200 mg KOH/g.
The reaction products A) are preferably made at a temperature between 50° C. and 180° C. in a solvent, a solvent blend or a water/solvent blend. Catalysts can used to speed up the reaction. Typical catalysts known to shorten the reaction time between epoxy and acid groups are metal salts, amines and quaternary ammonium salts. Examples are sodium, potassium and lithium hydroxide, triethylamine, benzyldimethylamine, cyclohexyldimethylamine, triethylammoniumchloride, triethylammoniumbromide, triethylammoniumiodide and triethylbenzyl phosphonium bromide.
Compounds corresponding to the general formula I, preferably with R═C1- to C10-alkyl, may be used as component a). The alkyl radicals may be substituted by heteroatoms such as oxygen, phosphorus or silicon. Examples hereof are ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl and nonylphosphonic acid. It is also possible to use derivatives of diphosphonic acid as component a). For example, these may then be 1-hydroxyalkane-1,1-diphosphonic acids. An example of the latter is 1-hydroxyethane-1,1-diphosphonic acid. Moreover, compounds corresponding to the general formula II, preferably with R′═C1- to C10-alkyl may be used as component a). The alkyl radicals may be substituted by heteroatoms such as oxygen, phosphorus or silicon. A preferred example of compounds corresponding to formula II is vinylphosphonic acid. Ethylphosphonic acid, propylphosphonic acid, octylphosphonic acid and vinylphosphonic acid may be used preferably as component a). Mixtures of several phosphonic acid derivates a) can be used.
The epoxy compounds b) are polyepoxides with an average of at least 2 epoxy groups per molecule. These epoxy compounds can be saturated, unsaturated, cyclic, acyclic, aliphatic, cycloaliphatic, aromatic or heterocyclic. They may contain substituents such as halogen, hydroxyl, ether, alkyl and/or aryl groups. In general th
Bruylants Paul
Huybrechts Josef
Kirshenbaum Kenneth S.
Koerner Michael
Dawson Robert
Deshmukh Sudhir G.
E. I. du Pont de Nemours and Company
Zimmer Marc S
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