Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-12-12
2003-01-14
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S215000
Reexamination Certificate
active
06506825
ABSTRACT:
The invention relates to aqueous electrodeposition lacquers (EDLs). The invention also relates to a process for preventing edge migration when electrophoretically deposited aqueous electrodeposition lacquers are stoved, using solid, finely divided urea compounds.
Electrodeposition lacquers are used in particular to produce anti-corrosive primer layers on metal substrates. They may also be deposited and stoved, for example, onto any electrically conductive substrates as a one-coat top coat, clear lacquer or as a lacquer film which is arranged within a multi-coat lacquering. An EDL film arranged within a multi-coat lacquering may, for example, be a lacquer film with decorative effect which acts as a top coat or to which a clear lacquer film may further be applied.
A problem which arises when lacquering with electrodeposition lacquers is edge migration when an EDL film previously deposited onto an electrically conductive substrate is stoved. The EDL film pulls away from the edge, reducing the film thickness at and/or in the immediate vicinity of the edge. In extreme circumstances the edge is not coated after stoving. While this is perceived as a difference in colour because of the substrate showing through in the region of the edge, in the case of decorative EDL coatings, for example, in the case of anti-corrosive EDL primers the anti-corrosive effect is impaired or lost at and/or in the region of the edge.
Electrodeposition lacquer coating agents with good edge coverage, which contain polymer powders, are known from EP-A-0 433 783. The polymer powders may also, for example, be pulverulent urea/aldehyde resins which are highly crosslinked and have no melting point. Producing the polymer powders and incorporating them into electrodeposition lacquer coating agents is complex and requires a grinding process for example.
The object of the invention is to provide electrodeposition lacquers with low or no edge migration behaviour when the electrophoretically deposited coating films comprising them are stoved, and which may be provided with no special outlay.
It has been shown that this object can be achieved by adding solid, finely divided urea compounds (A) to EDL coating agents.
Until now it has only been known to use urea compounds (A) as sag control agents in solvent-based stoving lacquers (DE-C-27 51 761, EP-A-0 192 304 and EP-A-0 198 519 for example). In no way could it have been expected, however, that the use of such urea compounds (A) is possible in aqueous EDL coating agents and has an effect which reduces edge migration.
The present invention therefore provides electrodeposition lacquer coating agents, which contain in addition to conventional film-forming, self-curing or non-self-curing binders and optionally curing agents, pigments, fillers, conventional lacquer additives and solvents, 0.1 to 5 wt. % of one or more solid, finely divided urea compounds (A), which are addition products comprising aromatic, araliphatic, cycloaliphatic or aliphatic diisocyanates and/or polyisocyanates derived therefrom and mono and/or polyamines with primary and/or secondary amino groups, related to the resin solids content of the EDL coating agents.
The invention further provides a process for preventing edge migration when staving electrophoretically deposited aqueous electrodeposition lacquers, which is characterized in that one or more solid, finely divided urea compounds are added to the electrodeposition lacquers in a quantity from 0.1 to 5 wt. % related to the resin solids content, before deposition onto a conductive substrate.
The invention further provides the use of solid, finely divided urea compounds as additives in aqueous electrodeposition lacquers.
The urea compounds are preferably added as additives which prevent edge migration in a quantity from 0.3 to 3, particularly preferably 0.5 to 2 wt. %, related to the resin solids.
The electrodeposition lacquers according to the invention are aqueous coating agents with 10 to 30 wt. % solids for example. They may be electrodeposition lacquers which can be deposited anodically or cathodically. The solids of the electrodeposition lacquers according to the invention are formed by the resin solids, pigments, fillers, further conventional lacquer additives and the content of solid, finely divided urea compounds (A) which is essential to the invention. The resin solids of the EDL coating agents according to the invention are composed of the binder or binders and curing resin(s) they optionally contain. Pigment paste resins (paste resins) which the EDL coating agents according to the invention optionally contain are counted among the binders. At least a portion of the binders has ionic substituents and/or substituents which can be converted into ionic groups. The binders may be self-curing or non-self-curing, in the latter case they have groups capable of chemical curing and the EDL coating agents according to the invention then contain curing agents. The curing agents may have ionic groups also.
The EDL coating agents according to the invention contain binders (EDL binders) having ionic substituents and/or substituents which may be converted into ionic groups, also called ionic binders below. In addition to these the EDL coating agents according to the invention may also contain binders free of ionic groups and/or groups which can be converted into ionic groups, called non-ionic binders below, in a quantity from 0 to 25 wt. %, for example, related to the sum of ionic and non-ionic binders which adds up to 100 wt. %, related in each case to the binder solids (comprising binders and paste resin but not the curing agent content).
The ionic binders' ionic groups or groups which can be converted into ionic groups may be anionic groups or groups which can be converted into anionic groups, e.g. acid groups, such as —COOH, —SO
3
H and/or —PO
3
H
2
and the corresponding anionic groups neutralized with bases. The ionic groups may, however, also be cationic groups or groups which can be converted into cationic groups, e.g. basic groups, preferably basic groups containing nitrogen; these groups may be present in quaternized form or they are converted into cationic groups with a conventional neutralizing agent, e.g. an organic monocarboxylic acid, such as formic acid or acetic acid for example. Examples are amino, ammonium, e.g. quaternary ammonium, phosphonium and/or sulfonium groups. Amino groups present may be primary, secondary and/or tertiary. The groups which can be converted into ionic groups may be present in partially or wholly neutralized form.
The ionic binders have functional groups capable of chemical curing, particularly hydroxyl groups, corresponding, for example, to a hydroxyl value from 30 to 300, preferably 50 to 250 mg KOH/g.
The EDL coating agents according to the invention may be per se known EDL coating agents which can be deposited anodically (ADLs). These contain binders which can be deposited anodically, based, for example, on polyesters, epoxy resin esters, (meth)acrylic copolymer resins, maleate oils or polybutadiene oils with a weight average molecular weight (Mw) from 300 to 10000 for example and an acid value from 35 to 300 mg KOH/g. The binders have COOH, SO
3
H and/or PO
3
H
2
groups. The resins may be converted into the aqueous phase after neutralization of at least a portion of the acid groups. The binders may be self-curing or non-self-curing. The ADL coating agents may therefore also contain conventional curing agents, e.g. triazine resins, curing agents which contain groups capable of, transesterification or blocked polyisocyanates.
In the case of EDL coating agents according to the invention used as anti-corrosive primer in particular, they are preferably per se known EDL coating agents which can be deposited cathodically (CDLs). These contain binders which can be deposited cathodically such as resins containing primary, secondary and/or tertiary amino groups, the amine values of which are 20 to 250 mg KOH/g for example. The weight average molecular weight (Mw) of these CDL binders is preferably 300 to 10000.
Flosbach Carmen
Kerber Hermann
Kerlin Klaus-Günter
Klein Klausjörg
Vogt-Birnbrich Bettina
Benjamin Steven C.
Cain Edward J.
E. I. du Pont de Nemours and Company
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