Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1990-12-10
1993-05-11
Marquis, Melvyn I.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525520, 523415, C08F 2000
Patent
active
052101541
DESCRIPTION:
BRIEF SUMMARY
The invention relates to water-thinnable baking paints based on a mixture of polyurethane, polyester and, if desired, aminoplast resin as binders and to the use of these baking paints as filler material and intermediate stone chip resistant coat.
In addition, the invention also relates to a process for painting motor vehicle bodies, in which process
In another process a water-thinnable baking paint is applied as an intermediate stone chip resistant coat between process stages (1) and (2) and baked.
In the painting of motor vehicle bodies severe demands are made on the baking paints used as filler material and intermediate stone chip resistant coat. The baking paints which can be used as filler materials must be suitable for problem-free application by electrostatic or electrostatically aided spraying techniques even at a high solids content (.gtoreq.40% by weight) of the spray paint, they must be bakeable without any blemishes occurring in the form of bubbles and they must furnish filler coats which possess optimum interadhesion characteristics, i.e. on the one hand the filler coat must adhere well to the electrocoating and, on the other hand, the topcoat must adhere well to the filler coat.
An important object of the filler coat is to fill and cover surface irregularities in order to level the undercoat for the subsequent topcoat. This cover of the undercoat structure and substrate blemishes must be accomplished without having to carry out much polishing of the filler coat, a requirement which can only be met when the filler material has good flow-out characteristics. Apart from the optical quality, important technical properties of the coating, for example corrosion protection and especially stone chip resistance and other mechanical hazards are also quite crucially dependent on the quality of the filler coat.
If water-thinnable baking paints are to be used as intermediate stone chip resistant coats, the main requirement of these paints is distinctly to improve the resistance of the complete system of coats to stone impact.
Filler materials and intermediate stone chip resistant coats used up to now have been predominantly baking paints based on organic solvents.
For economic and ecological reasons the paint industry has been striving to replace solvent-borne filler materials by water-thinnable filler materials.
Thus water-thinnable baking fillers based on acid polycondensates which can be prepared by reacting aminoplasts, polyesters, polyhydric alcohols, cyclic polycarboxylic acids and acrylate resins are known from DE-OS 3,537,855.
The water-borne fillers based on alkyd resins, known from prior art, leave however much to be desired. Thus they possess poor adhesion to various electrocoated substrates and also to various topcoats, and the solids contents obtainable for a viscosity which is suitable for spray application, is much too low. It is, however, especially the stone chip resistance of the resultant coating which must be further improved.
Furthermore, aqueous polyurethane-based coating compositions which give rise to coatings with good technical properties, have been known for a few years, but not filler materials. Thus, U.S. Pat. No. 4,423,179 describes aqueous coating compositions which may be applied to a variety of substrates by conventional methods. The resultant coatings possess improved flexibility and a resistance to solvents. The principal components of this coating composition ar an aminoplast resin and a polyurethane with a hydroxyl value of >10, prepared from a diisocyanate and a polyester polyol with an average molecular weight between 1200 and 1500. The use of dimeric fatty acids for the synthesis of the polyester polyol forms an essential part of the invention.
U.S. Pat. No. 3,954,899 discloses coating compositions likewise based on a polyurethane containing hydroxyl groups, an aminoplast resin as well as a compound which may or may not contain hydroxyl groups, for example a polyester, which compositions may be used not only in the form of an aqueous dispersion but also based on a
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Hille Hans-Dieter
Muller Bodo
Schmidt Winfried
Weidemeier Klaus
BASF Lacke & Farben Aktiengesellschaft
Gulakowski Randy
Marquis Melvyn I.
Marshall Paul L.
Werner Frank G.
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