Coating processes – Applying superposed diverse coating or coating a coated base – Synthetic resin coating
Reexamination Certificate
1998-12-11
2001-07-31
Dudash, Diana (Department: 1762)
Coating processes
Applying superposed diverse coating or coating a coated base
Synthetic resin coating
C524S591000, C524S601000, C525S124000, C525S127000, C525S440030, C525S454000, C528S048000, C528S075000, C528S274000, C528S288000
Reexamination Certificate
active
06268021
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to solvent-containing or aqueous binder vehicles and thermally hardening solvent-containing or aqueous coating media and the use thereof for the production of lacquer coatings, particularly multi-layer coatings, for example as a base lacquer and preferably as a clear or covering lacquer.
BACKGROUND OF THE INVENTION
Coating media are known in which resins which contain hydroxyl groups are crosslinked with polyisocyanates. Thus EP-A-0 541 604 describes coating media based on polycondensation and polyaddition products which contain hydroxyl groups and which are crosslinked with polyisocyanates, wherein the binder vehicle which contains hydroxyl groups is composed of at least one polyester and/or one alkyd resin and at least one polyacrylate resin, wherein the polyacrylate resin is produced, at least in part, in the presence of the polyester which is contained as a proportion. Customary organometallic compounds, such as dibutyltin laurate, are employed as catalysts here. Substances of this type are not toxicologically harmless, and moreover often give rise to yellowing. EP-A-0 036 975 describes a two-component lacquer which is composed of a polyester polyol which is low in aromatics, and optionally of a hydroxy-functional polyacrylate resin, which are crosslinked with polyisocyanates. Zinc octoate, which in combination with UV absorbers often results in lacquers which exhibit pronounced yellowing, is used as the catalyst here. EP-A-0 206 072 describes polyacrylate copolymers which are synthesised in the presence of polyester polyols. These binder vehicles can be crosslinked with polyisocyanates or melamine resins. Acids, such as paratoluenesulphonic acid for example, are described as catalysts. The use of acids of this type also frequently results in pronounced yellowing in clear lacquers.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a coating medium which is particularly suitable for high-solids coatings which are highly resistant to chemicals and are free from yellowing, and which result in a very good covering lacquer condition, a reduced run-off tendency and a very high resistance to bubble formation, and with which the disadvantages described above are avoided.
It has been shown that this object can be achieved by a binder vehicle composition or by coating media which, in contrast to known coating media, employ strongly acidic resins as catalysts.
The present invention therefore relates to a binder vehicle composition, which contains:
A) 20 to 77% by weight of one or more binder vehicles based on one or more oligomeric or polymeric polyol compounds with a hydroxyl number of 80 to 300 mg KOH/g, preferably 120 to 200 mg KOH/g, an acid number of 0 to 30 mg KOH/g, preferably 0 to 15 mg KOH/g, a number average molecular weight (Mn) of 500 to 10,000, preferably 1000 to 5000, and a glass transition temperature of −20 to +70° C., preferably 0 to 50° C.;
B) 77 to 20% by weight of one or more crosslinking agents based on aliphatic and/or cycloaliphatic polyisocyanates;
C) 3 to 20% by weight of one or more oligo- or polyesters, which contain carboxyl groups, as catalyst resins, which have an acid number of 210 to 300 mg KOH/g, preferably 220 to 270 mg KOH/g, and a number average molecular weight (Mn) of 420 to 3000, preferably 700 to 2000;
wherein the sum of components A) to C) is 100% by weight in each case; and one or more organic solvents and/or water.
The present invention further relates to aqueous and non-aqueous coating media which contain the binder vehicle composition according to the invention as well as customary lacquer additives, where said customary lacquer additives may also be pigments and/or extenders.
The binder vehicle compositions and coating media according to the invention contain, as component A), one or more polyol compounds as binder vehicles. Preferred examples thereof include hydroxy-functional (meth)acrylic copolymers, polyesters and/or polyester-modified (meth)acrylic copolymers, although other polyols, such as hydroxy-functional polyurethanes and polyethers for example, are also suitable.
These (meth)acrylic copolymers can be produced by polymerisation using customary methods, such as bulk-, solution- or pearl polymerisation for example. These different polymerisation methods are well known to one skilled in the art and are described, for example, in: Houben-Weyl, Methoden der organischen Chemie, 4th Edition, Volume 14/1, pages 24 to 255 (1961). The solution polymerisation method is preferred for the production of the (meth)acrylic copolymers which are used in the coating medium according to the invention. In this method, the solvent is placed in the reaction vessel and heated to boiling temperature, and the monomers are continuously added, optionally in admixture with radical initiators, over a defined period. The polymerisation temperatures are between 60° C. and 160° C. for example, and are preferably between 120° C. and 150° C. The initiators and monomers can also be added separately or at different times during the polymerisation process, however.
The (meth)acrylic monomers which are used can be non-functionalised, hydroxy-functionalised or carboxy-functionalised. Moreover, other ethylenically unsaturated monomers can also be used. The expression “(meth)acrylic” is synonymous with “acrylic and/or methacrylic”.
Examples of non-functionalised (meth)acrylates include long-chain, branched or unbranched, unsaturated monomers such as alkyl (meth)acrylates which comprise C
8
-C
18
chains in their alkyl part, such as 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, 3,5,5-trimethylhexyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, hexadecyl (meth)acrylate, octadecyl (meth)acrylate, lauryl acrylate-1214, isobornyl (meth)acrylate or 4-tert.-butyl cyclohexyl methacrylate for example. Other examples include short- or medium-chain, branched or unbranched unsaturated monomers, such as alkyl (meth)acrylates which comprise C
1
-C
7
chains in their alkyl part, e.g. methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate or cyclohexyl (meth)acrylate.
Another suitable non-functionalised polymerisable component is a monovinyl aromatic compound. This preferably contains 8 to 10 carbon atoms per molecule. Examples of suitable compounds include styrene, vinyltoluenes, &agr;-methylstyrene, chlorostyrene, o-, m- or p-methylstyrene, 2,5-dimethylstyrene, p-methoxystyrene, p-tert.-butyl styrene, p-dimethylaminostyrene, p-acetamidostyrene and m-vinylphenol. Vinyltoluenes, and styrene in particular, are preferably used. It is also possible to use the vinyl ester of versatic acid (Trade Name VEOVA 10 of Shell AG).
Examples of other suitable non-functionalised ethylenically unsaturated monomers include the alkyl esters of maleic, fumaric, tetrahydrophthalic, crotonic, isocrotonic, vinylacetic and itaconic acids, such as the corresponding methyl, ethyl, propyl, butyl, isopropyl, isobutyl, pentyl, amyl, isoamyl, hexyl, cyclohexyl, 2-ethylhexyl, octyl, 3,5,5-trimethylhexyl, decyl, dodecyl, hexadecyl, octadecyl and octadecenyl esters for example.
The (meth)acrylic monomers which are used may comprise primary or secondary hydroxy functions. Examples of monomers comprising primary hydroxy functions include hydroxyalkyl esters of &agr;,&bgr;-unsaturated carboxylic acids, such as acrylic acid and/or methacrylic acid, which comprise a primary OH group and a C
2
-C
3
hydroxyalkyl radical, e.g. hydroxyethyl (meth)acrylate, as well as hydroxyalkyl esters of &agr;,&bgr;-unsaturated carboxylic acids, such as acrylic acid and/or methacrylic acid, which comprise a primary OH group and a C
4
-C
18
hydroxyalkyl radical, e.g. butanediol monoacrylate, hydroxyhexyl acrylate, hydroxyoctyl acrylate and the corresponding methacrylates, and the reaction products of hydroxyethyl (meth)acrylate with caprolactone.
Examples of monomers which compr
Flosbach Carmen
Herrmann Friedrich
Schild Dirk
Schubert Walter
Dudash Diana
Herberts GmbH
Pillsbury Madison & Sutro LLP
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