Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Forming nonmetal coating
Patent
1995-10-03
1997-06-17
Tung, T.
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Forming nonmetal coating
204499, 204502, 204503, 524591, 524507, 525123, 525455, C25D 1100, C08J 303, C08L 3104
Patent
active
056393610
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
The present invention relates to new binder systems which are suitable for electrodeposition coating and are based on basic, thermally crosslinkable epoxy or polyurethane resins as binders (B), containing from 0.001 to 1% by weight of a polymer (I) whose predominant components are ethyl acrylate and/or n-propyl acrylate, based on the overall solids content of the binder system.
The invention also relates to new pigment paste formulations for electrodeposition coating which contain the polymers (I). The invention relates, furthermore, to a method of electrodeposition coating using the new binder systems, to the use of polymers (I) as an additive to electrodeposition baths for improving the surface quality of the articles coated by means of electrodeposition, and to the coated articles themselves.
It is generally known to coat metallic articles with the aid of cathodic electrodeposition, a process of which use is made, in particular, in the motor vehicle industry. The electrodeposition coating systems used for this purpose generally contain, as fundamental components, a binder, also called base resin, a crosslinking component and a pigment paste.
Epoxy and polyurethane resins are known, as binders, in numerous configurations. EP-A 261 385 describes binder combinations for cathodic electrodeposition coating which crosslink by means of external agents and are based on an epoxy resin, containing hydroxyl and amino groups, and on a poly(meth)acrylate resin containing amino groups. Also known are coating systems which contain, in addition to the principal components, auxiliaries which reduce the surface tension in the coating material and thus improve the surface quality of electrodeposition-coated articles. The addition of these auxiliaries is necessary, in particular, if the binder systems used have a tendency toward problems in coating flow and toward the formation of craters in the coating film and give rise to adhesion problems in respect of the topcoats applied subsequently. The binder systems known to date which contain silicone oils, polyether-urethanes (DE-A 37 01 547) or polybutyl acrylates (EP-A 422 533) as auxiliaries impart to the finished coating materials the abovementioned, disadvantageous properties, in a more or less pronounced form.
The object of the present invention was to find new binder systems based on basic, thermally crosslinkable epoxy or polyurethane resins as binders, which exhibit a good behavior in respect of both the surface quality of the cathodically deposited coatings and the adhesion of topcoats applied subsequently.
To this end the binder systems defined at the outset were found.
Also found were new pigment paste formulations for electrodeposition coating, a method of electrodeposition coating using the new binder systems, and the use of polymers (I) as an additive to electrodeposition baths for improving the surface quality of the articles coated by means of electrodeposition, and the coated articles themselves.
The binder systems according to the invention contain from 0.001 to 1% by weight, preferably from 0.01 to 0.75% by weight, of a polymer (I) whose predominant components are ethyl acrylate and/or n-propyl acrylate, based on the overall solids content of the binder system. The term "predominant components" should be understood as referring to those quantities of ethyl and/or n-propyl acrylate whose content in a polymer (I) is more than 50 mol %. Particularly suitable polymers (I) are homopolymers of ethyl acrylate and of n-propyl acrylate and copolymers of these two monomer building blocks.
Other suitable polymers (I) are those containing minor quantities of other olefinically unsaturated monomers. Their proportion, based on the polymer (I), is generally less than 50 mol %, preferably from 0.1 to mol %. Examples of comonomers which can be used are the following:
monomers containing amino groups,
e.g. N-dialkylaminoalkyl acrylates and methacrylates such as
and N-dialkylaminoalkylacrylamides and -methacrylamides such as and methacrylates and aminoalkylacrylam
REFERENCES:
patent: 5089101 (1992-02-01), Hayashi et al.
Faul Dieter
Fobbe Helmut
Humke Klaus
Schupp Hans
Schwerzel Thomas
BASF Lacke & Farben AG
Noguerola Alex
Tung T.
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