Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-02-16
2002-03-26
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C204S502000, C204S504000, C204S505000, C204S506000, C523S402000, C523S404000, C523S428000
Reexamination Certificate
active
06362255
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a cationic electrodeposition coating composition and more particularly to a lead-free cationic electrodeposition coating composition which can be applied to a substrate which has not been subjected to a chemical conversion treatment or any local area of a substrate that has not been sufficiently so pretreated to impart a high resistance to corrosion and rusting.
PRIOR ART
Electrodeposition coating compositions are excellent in rust preventing effect, corrosion resistance and throwing power and can form uniform coatings and, therefore, are widely used on metallic shaped articles, especially as primers for automotive bodies and parts. From the standpoint of corrosion resistance and rust prevention, in particular, cationic electrodeposition coating compositions have now been in use almost universally.
In cationic electrodeposition coating compositions, rust inhibitor pigments, such as lead compounds, for example basic lead silicate, have been used to attain high corrosion and rusting resistance. In recent years, however, the use of lead compounds has been restricted because of their toxicity which causes an environmental pollution problem, among others.
As rust inhibitor pigments other than lead compounds, such pigments as phosphate, molybdate and borate pigments, among others, have heretofore been evaluated. These, however, have a drawback; they are inferior in rust preventing effect when compared with lead compounds. As for other proposals, Japanese Kokai Publication Hei-02-279773 discloses the use of iron oxide, Japanese Kokai Publication Hei-04-325572 discloses the use of copper, nickel, zinc, cobalt, chromium, aluminum, manganese, zirconium, tin or iron, Japanese Kokai Publication Hei-05-140487 discloses the use of bismuth hydroxide/tin, cerium hydroxide/tin or nickel hydroxide/tin, Japanese Kokai Publication Hei-05-239386 discloses the use of lantanum compounds, Japanese Kokai Publication Hei-05-247385 discloses the use of bismuth compounds/tin and, further, Japanese Kokai Publication Hei-06-220371 discloses the use of tungsten compounds. In all these cases, however, the anticorrosive and rust-preventing effects have been found inadequate.
Moreover in order to achieve high corrosion resistance and rust inhibition by the application of a cationic electrodeposition coating, the metal substrate must be subjected to a chemical conversion treatment, using zinc phosphate, for instance, in advance. However, when the metal substrate has a “bag”-like recessed structure, an effective chemical conversion film may not be formed in the recessed area so that no sufficient corrosion resistance or rust inhibition is obtained at times.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a cationic electrodeposition coating composition which is free of toxic rust-preventive pigments such as lead compounds and capable of giving coating films having high resistance to corrosion and rusting, even when applied to a substrate surface which has not been subjected, or only insufficiently subjected, to a chemical conversion treatment.
The present invention provides a cationic electrodeposition coating composition
which comprises a rust inhibitor comprising at least one compound selected from the group consisting of compounds containing any of elemental metals belonging to the period 4, 5 or 6 of group 3 of the periodic table and a sulfonium- and propargyl group-containing resin composition.
It is preferred that the content of said rust inhibitor is 0.03 to 10 weight parts in terms of the elemental metal in the rust inhibitor based on 100 weight parts of the solid resins in the resin composition.
It is also preferred that the resin composition has a sulfonium group content of 5 to 400 millimoles and a propargyl group content of 10 to 495 millimoles per 100 grams of the solid resins in the resin composition, and the sum total of the sulfonium and propargyl group-contents is not more than 500 millimoles per 100 grams of the solid resins in the resin composition, and still more preferred that the resin composition has a sulfonium group content of 5 to 250 millimoles and a propargyl group content of 20 to 395 millimoles per 100 grams of the solid resins in the resin composition, and the sum total of the sulfonium and propargyl group contents is not more than 400 millimoles per 100 grams of the solid resins in the resin composition.
The resin composition comprises an epoxy resin as a skeleton thereof
and said epoxy resin is preferably a novolak cresol type epoxy resin or novolak phenol type epoxy resin and has a number average molecular weight of 700 to 5,000.
DETAILED DESCRIPTION OF THE INVENTION
The cationic electrodeposition coating composition of the present invention contains a rust inhibitor comprising at least one compound selected from the group consisting of compounds containing any of elemental metals belonging to the period 4, 5 or 6 of group 3 of the periodic table and a sulfonium- and propargyl group-containing resin composition.
The rust inhibitor in the cationic electrodeposition coating composition is at least one compound selected from the group consisting of compounds containing any of the elemental metals belonging to the period 4, 5 or 6 of group 3 of the periodic table. As specific examples of such elemental metals, there can be mentioned scandium, yttrium and lanthanoid elements. Promethium, however, is a radioactive element and can hardly be obtained from commercial sources. Therefore, this element is unsuited for all practical purposes.
As examples of the compounds containing such elements, there can be mentioned organic or inorganic compounds containing, as one constituent, an yttrium compound, a cerium compound, a praseodymium compound, a neodymium compound, samarium compound, europium compound, gadolinium compound, terbium compound, dysprosium compound, holmium compound, erbium compound, thulium compound, ytterbium compound or lutetium compound. More specifically, there can be mentioned salts with organic acids, such as yttrium formate, cerium acetate, neodymium acetate, europium acetate, terbium acetate, holmium acetate, erbium acetate, ytterbium acetate, samarium lactate, neodymium lactate, cerium lactate, samarium oxalate, etc. and salts with inorganic acids or inorganic compounds, such as yttrium nitrate, yttrium tungstate, praseodymium molybdate, yttrium amido sulfate, neodymium amidosulfate, samarium amidosulfate, neodymium oxide, samarium hydroxide and so on.
The rust inhibitor mentioned above may be water-soluble or more or less water-insoluble but one having a solubility of not less than 1 g/dm
3
in water is preferred because a high degree of corrosion resistance can be attained at a low concentration. As such rust inhibitors, among the compounds mentioned above, there can be mentioned cerium acetate, neodymium acetate, yttrium amidosulfate, neodymium amidosulfate and samarium amidosulfate.
The content of the above rust inhibitor in the cationic electrodeposition coating composition of the present invention is preferably 0.03 to 10 weight parts, more preferably 0.05 to 8 weight parts, in terms of the elemental metal in the rust inhibitor based on 100 weight parts of the solid resins in the resin composition. When the content of said rust inhibitor is less than 0.03 weight parts in terms of the elemental metal in the rust inhibitor, the coatings obtained will be insufficient in corrosion resistance and rust preventing effect. When it is in excess of 10 weight parts, the physical properties of the coating films obtained will possibly be reduced.
The resin composition in the cationic electrodeposition coating composition of the present invention contains a sulfonium group and a propargyl group. The term “resin composition” as used herein means a composition comprised exclusively of a resin having both sulfonium and propargyl groups per molecule or a composition containing both a sulfonium group-containing resin and a propargyl group-containing resin. In the latter case, the resin composition
Kawakami Ichiro
Kawanami Toshitaka
Kokubun Takayuki
Okumura Yoshiaki
Sakamoto Hiroyuki
Aylward D.
Connolly Bove Lodge & Hutz
Dawson Robert
Nippon Paint Co. Ltd.
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