Aqueous coating materials and their use for the production of fi

Details Aqueous coating materials and their use for the production of fi Aqueous coating materials and their use for the production of fi

1996-05-06

1999-05-18

Gorr, Rachel

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From reactant having at least one -n=c=x group as well as...

528 71, 25218222, 524839, 524840, 524591, 427470, C08G18/80

Patent

active

059051329

DESCRIPTION:

BRIEF SUMMARY
The invention relates to aqueous coating materials and to their use for the production of filler coats in automotive finishing.
Car bodies are coated by applying over one another an electrodeposition coat, a filler coat and one or two topcoats and baking them in succession in two or more baking steps. Generally in a first step the electrodeposition coat is deposited and baked. Then the baked electrodeposition coat is coated over with a filler coat. This filler coat is baked and coated over with a one- or two-coat topcoat. Finally the topcoat is baked. Two-coat topcoats consist of a pigmented basecoat and a clearcoat applied over it. Two-coat topcoats are usually applied by the wet-on-wet method, i.e. a pigmented basecoat is first produced which in the unbaked state is coated over with the clearcoat. Subsequently the pigmented basecoat and the clearcoat are baked together. However, it is also possible, for example, to apply a filler coat over the deposited electrodeposition coat in the unbaked state and then to bake electrodeposition coat and filler coat together. It is then possible to apply a one- or two-coat topcoat to the baked filler coat and to bake it.
It is also possible to apply the filler coat to an unbaked or to a baked electrodeposition coat and to apply to the unbaked filler coat the pigmented basecoat, for a two-coat topcoat, and then to bake the filler coat and the pigmented basecoat and, if appropriate, the electrodeposition coat together. A clearcoat can then be applied to the baked, pigmented basecoat and baked.
In automotive finishing the function of the filler coat is, in particular, to fill and to cover uneven areas in the electrodeposition coat in order to make the substrate level for the subsequent topcoat.
The better this filling and covering of uneven areas in the electrodeposition coat, the better the optical quality of the overall finish. In addition to the optical quality, there are also important mechano-technological properties of the overall finish, for example protection against corrosion and especially resistance to stone chipping and to other mechanical attacks, for which the quality of the filler coat is crucial. A further important requirement of the filler coat comes from the fact that the windows in a car body are fixed by adhesive bonding into the window-frames of the body, often using the filler coat as substrate. It is then of great importance for the durability of the pane bond that the adhesive employed adheres to the filler coat so well that it is not detached from the filler coat even under extreme weather conditions.
DE-A-40 05 961 discloses aqueous coating materials which contain a water-dilutable polyurethane resin as binder and which are suitable for the production of filler coats. The filler coats produced using these coating materials, with regard to their suitability as a substrate for the adhesive bonding of window panes in car bodies, are in need of improvement.
The object of the present invention is to provide aqueous coating materials which are suitable for the production of filler coats in automotive finishing and which are distinguished in particular by the fact that they give filler coats which are so highly suitable as a substrate for the adhesive bonding of window panes in car bodies that the adhesive bond of the window panes is not weakened even under severe stress, for example sharp fluctuations in humidity and temperature.
This object is surprisingly achieved by the provision of aqueous coating materials which contain at least one water-dilutable polyurethane resin as binder and which are characterized in that the water-dilutable polyurethane resin can be prepared by reacting, in a first step, toward isocyanate groups and at least one acidic group which is capable of forming anions, or a mixture of such compounds, and number-average molecular weight of from 400 to 5000, or a mixture of such polyester- and/or polyether-polyols, and 60 to 399, or a mixture of such polyols, and (d) being reacted with one another in a proportion such that the isocy

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