Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-01-17
2003-10-07
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S589000, C524S590000, C524S591000, C524S839000, C524S840000, C525S455000, C528S044000, C528S045000, C528S073000
Reexamination Certificate
active
06630537
ABSTRACT:
The present invention relates to a two-component coating composition (2C system) which comprises (I) at least one isocyanate as crosslinking agent and (II) at least one binder having functional groups which react with isocyanates, and to its use.
PRIOR ART
By two-component coating compositions—dubbed 2C systems for short—is meant a system comprising two different, separately prepared and stored coating components which are nevertheless always employed in conjunction with one another and which, by a user wishing to produce a coating from a coating composition, are mixed to form the coating composition before the coating is produced. 2C systems of this kind are common, inter alia, for the production of top coats. The term top coats here refers to coating materials used to produce the topmost coating film. This topmost coating film can comprise one or more layers, especially two layers. Two-layer top coats (two-coat finishes) consist of a pigmented base coat film and, applied atop the base coat film, a clear coat film which is pigmented only with transparent pigments if at all. Two-coat finishes are nowadays produced by the wet-on-wet method, in which a pigmented base coat is applied first and the resulting base coat film is overpainted with a clear coat, without a baking step, and then base coat film and clear coat film are cured together. This method is highly advantageous economically but places high requirements on the base coat and the clear coat. The clear coat applied to the still uncured base coat must not start to dissolve, or otherwise interfere with, the base coat film, since otherwise the finishes obtained are of poor appearance. This applies in particular to coatings for which base coats comprising special-effect pigments (e.g. metal pigments, especially aluminium flakes, or pearlescent pigments) are employed.
2C systems, which are used primarily for the finishing of motor vehicles, consist normally of hydroxy-functional polyacrylates and/or polyesters and of free isocyanate trimers of hexamethylene diisocyanate or of isophorone diisocyanate (c.f. e.g. the patent texts DE-4432260, DE-4432985). These systems, however, have various grave disadvantages. In particular, coatings with good acid resistance possess only moderate scratch resistance. Conversely, when the scratch resistance is sufficient, the acid resistance is inadequate.
SUBJECT OF THE INVENTION
The present invention is therefore based on the object of providing a 2C system comprising in its component (I) at least one isocyanate as crosslinking agent and in its component (II) at least one binder having functional groups which react with isocyanates and which no longer has the abovementioned disadvantages but instead, in particular, combines good scratch resistance with good acid resistance.
This object is achieved in accordance with the invention in that component (I)
Ia) comprises at least one isocyanate having at least one diisocyanate structural unit which
i) has an unsaturated/aromatic or non-aromatic ring structure having 5-10 ring atoms and
ii) has two isocyanate groups attached to the ring structure, where
iii) in the case of a non-aromatic ring structure
&agr;) both isocyanate groups are attached via linear C
1
-C
9
-alkyl and/or linear C
2
-C
10
-ether-alkyl or
&bgr;) one isocyanate group is attached directly and the other via linear C
2
-C
9
-alkyl and/or linear C
2
-C
10
-ether-alkyl, and
iv) in the case of an unsaturated aromatic ring structure at least one of the two isocyanate groups is attached via linear C
2
-C
9
-alkyl and/or linear C
2
-C
10
-ether-alkyl, both of which radicals have no benzylic hydrogen atoms, to the ring structure; and/or
Ib) comprises at least one oligomer of the isocyanate Ia) having from 2 to 10 isocyanate units, especially a trimer; and/or
Ic) comprises at least one partially blocked isocyanate Ia) and/or a partially blocked oligomer Ib), especially a trimer (Ib).
Component (I)
The essential constituent of component (i) according to the invention is at least one isocyanate Ia) to be used in accordance with the invention. This isocyanate has at least one diisocyanate structural unit having a specific structure. Although the isocyanate Ia) to be used in accordance with the invention can have two or more of these diisocyanate structural units, it has been found appropriate to use only one.
The diisocyanate structural unit has the following features according to the invention:
i) an unsaturated/aromatic or non-aromatic ring structure having 5-10 ring atoms and
ii) two isocyanate groups attached to the ring structure, where
iii) in the case of a non-aromatic ring structure
&agr;) both isocyanate groups are attached via linear C
1
-C
9
-alkyl and/or linear C
2
-C
10
-ether-alkyl or
&bgr;) one isocyanate group is attached directly and the other isocyanate group via linear C
2
-C
9
-alkyl and/or linear C
2
-C
10
-ether-alkyl, and
iv) in the case of an unsaturated/aromatic ring structure at least one of the two isocyanate groups is attached via linear C
2
-C
9
-alkyl or linear C
2
-C
10
-ether-alkyl, both of which radicals have no benzylic hydrogen atoms, to the ring structure.
With regard to the diisocyanate structural unit of the diisocyanate Ia) to be used in accordance with the invention there are various possibilities for its further formation, which are described below.
In terms of the ring structure it is possible in principle for it to comprise heterocyclic rings. In that case the ring structure comprises not only C atoms as ring atoms but also other ring atoms, such as N atoms, C atoms or Si atoms, for example. These heterocyclic rings can be saturated or unsaturated/aromatic heterocyclic rings. Examples of suitable saturated heterocyclic rings are the silacyclopentane, silacyclohexane, oxolane, oxane, dioxane, morpholine, pyrrolidine, imidazolidine, pyrazolidine, piperidine or quinuclidine rings. Examples of suitable unsaturated/aromatic heterocyclic rings are pyrrole, imidazole, pyrazole, pyridine, pyrimidine, pyrazine, pyridazine or triazine rings. It is preferred if the ring structure contains exclusively C atoms as ring atoms.
The ring structure can on the one hand be free of bridges. In the case where the ring structure is a bicyclic terpene framework, decalin, adamantane or quinuclidine, however, bridges may be present. Examples of suitable terpene frameworks are carane, norcarane, pinane, camphane or norbornane frameworks.
The hydrogen atoms of a diisocyanate structural unit, especially of the ring structure, can be substituted by groups or atoms which react neither with isocyanates nor with the component (II) described below. Examples of suitable groups are nitro, alkyl, cycloalkyl, perfluoroalkyl, perfluorocycloalkyl or aryl groups. Examples of suitable atoms are halogen atoms, especially fluorine.
The ring structure consists advantageously of 6 C atoms, especially in the form of cyclohexane or benzene.
Examples of suitable linear C
1
-C
9
-alkyl are methylene or ethylene and also tri-, tetra-, penta-, hexa-, hepta-, octa- or nonamethylene radicals, especially methylene radicals.
The linear C
2
-C
10
-ether-alkyls are attached to the ring structure either via the oxygen atoms or via the alkanediyl radicals present therein. They are preferably attached thereto via the oxygen atoms. The indices 2 to 10 denote that there are from 2 to 10 C atoms in the ether-alkyls.
The ether-alkyls may contain only 1 oxygen atom. It is of advantage in accordance with the invention if from 2 to 10, especially 2 to 5, oxygen atoms is [sic] present in the chain. In that case 1 or more, but especially 2, C atoms are located between 2 oxygen atoms.
Examples of suitable C
2
-C
10
-ether-alkyls are
—(O—CH
2
)
m
—, wherein m=1 to 10,
—(O—C
2
H
4
)
p
—, wherein p=1 to 5,
—(O—C
3
H
6
)
q
—, wherein q=1 to 3, or
—(O—C
4
H
8
)
r
—, wherein r=1 to 2.
If the isocyanate Ia) to be used in accordance with the invention comprises at least one diisocyanate structural unit having a non-aromatic ring system, especially cyclohexane, both isocyanate groups can be
Bartol Fritz
Baumgart Hubert
Bruchmann Bernd
Mohrhardt Günther
Rink Heinz-Peter
BASF Coatings AG
Niland Patrick D.
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