Stock material or miscellaneous articles – Composite – Of polyamidoester
Reexamination Certificate
2001-05-14
2003-05-20
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of polyamidoester
C428S425800, C524S081000, C524S379000, C524S389000, C427S407100
Reexamination Certificate
active
06565979
ABSTRACT:
The invention provides the preparation of two-layered lacquers of the base lacquer/clear lacquer type with improved clear lacquer wetting limits by using certain additives in aqueous base lacquers, and aqueous base lacquers suitable for this purpose. It also provides a process for preparing the two-layered lacquers using the aqueous base lacquer.
EP-A-0 281 936 discloses water-based base lacquers which contain sheet silicate dispersions prepared using polypropylene oxide as a protective colloid. The polypropylene oxides may contain ethylene oxide units in a randomly distributed form or in the form of a block copolymer structure. In the case of block copolymer polypropylene oxides, those with an average molecular weight of 500 to 8000 are suitable. However, polypropylene oxide homopolymers with an average molecular weight of 400 to 1000, very particularly preferably about 900, are preferred.
In particular in the automobile mass lacquering sector, the preparation of decorative two-layered top lacquers is increasingly being achieved by the application of a colour and/or effect providing base lacquer consisting of an aqueous base lacquer and a protective clear lacquer layer. The clear lacquer must be applied in a minimum thickness, which is predetermined by the clear lacquer wetting limits, in order to ensure the formation of a closed clear lacquer film over the entire substrate surface. This minimum thickness may even be exceeded in practice, for example to ensure the formation of a closed clear lacquer film in places which are difficult to reach by the application equipment, such as for example crimping, edges or indentations in a car body. This leads not only to an undesirably high consumption of clear lacquer but, depending on the nature of the clear lacquer, problems often also occur with the sag resistance of the clear lacquer on vertical surfaces if the thickness of the clear lacquer is too great.
EP-A-0 663 428 discloses the use of low molecular weight poly-C4-olefins as additives in water-based base lacquers in order to lower the wetting limit of the clear lacquer being applied. Stable incorporation of poly-C4-olefins in water-based base lacquers requires intensive mixing of the poly-C4-olefin with the aqueous base lacquer or the poly-C4-olefin is expediently added at a stage well before adding substantial amounts of water when preparing the water-based base lacquer.
The object of the invention is to provide water-based base lacquers for subsequent overpainting with clear lacquers which enable lowering of the clear lacquer wetting limits and application of the relevant clear lacquer layer in the thinnest possible layer and also increase process reliability when coating with the clear lacquer. The water-based base lacquer should be easy to prepare and be stable.
It was shown that this object can be achieved by using one or more polyethylene and or polypropylene glycols and/or polyols which are optionally partly or completely etherified with C1-C4-alkanols and have an average molecular weight of more than 1000 to 8000 as additives in water-based base lacquers. Therefore, the invention provides the use of linear and/or branched polyethylene oxide homopolymers, polypropylene oxide homopolymers and/or polyethylene/polypropylene oxide copolymers with randomly distributed ethylene oxide and propylene oxide units, wherein the terminal hydroxyl groups in the homopolymers or copolymers may be non-etherified or partly or completely etherified with C1-C4-alkanols, with an average molecular weight of more than 1000 to 8000 for reducing the clear lacquer wetting limits during two-layered lacquering with an aqueous base lacquer and clear lacquer. The average molecular weight mentioned is understood to be the calculated average molecular weight.
During use, the linear and/or branched polyethylene oxide homopolymers, polypropylene oxide homopolyrners and/or polyethylene/polypropylene oxide copolymers are added to the aqueous base lacquer prior to its application, preferably in a proportion of 0.5 to 15 wt. %, with respect to its solids content.
The invention also provides an aqueous base lacquer composition containing one or more binders and pigments and optionally fillers, cross-linking agents, organic solvents and/or conventional lacquer additives which is characterised in that it also contains one or more linear and/or branched polyethylene oxide homopolymers, polypropylene oxide homopolymers and/or polyethylene/polypropylene oxide copolymers with randomly distributed ethylene oxide and propylene oxide units, wherein the terminal hydroxyl groups in the homopolymers or copolymers may be non-etherified or partly or completely etherified with C1-C4-alkanols, with an average molecular weight of more than 1000 to 8000 in a proportion of 0.5 to 15 wt. %, with respect to its solids content.
The modified colour and/or effect providing water-based base lacquer according to the invention may be used during the preparation of multi-layered lacquers, in particular decorative base lacquer/clear lacquer two-layered lacquers. The waterbased base lacquers contain in an appropriate manner ionic or non-ionic stabilised binder systems. These are preferably anionic and/or non-ionically stabilised. Anionic stabilisation is preferably achieved by the presence of at least partly neutralised carboxyl groups in the binder, whereas non-ionic stabilisation is achieved by the presence of lateral or terminal polyethylene oxide units in the binder. The waterbased base lacquer may have physically drying properties or may be cross-linkable with the formation of covalent bonds. Base lacquers which cross-link with the formation of covalent bonds may be self-cross-linking systems or require the use of external cross-linking agents. In the latter case, they may be single component or multi-component water-based base lacquers.
Water-based base lacquers according to the invention contain one or more conventional film-forming binders. They may also contain cross-linking agents, if the binders are not self-cross-linking or self-drying. Neither the binders nor the optionally present cross-linking components are subject to any restrictions at all. For example, conventional polyester, polyurethane and/or poly(meth)acrylate resins may be used as film-forming binders. The choice of an optionally present cross-linking agent is not critical; it is governed in a manner which is familiar to a person skilled in the art by the functionality of the binder, that is the cross-linking agents are chosen so that they have a reactive functionality which is complementary to the functionality of the binder. Examples of such complementary functionalities between binder and cross-linking agent are: carboxyl/epoxide, hydroxyl/methylolether and/or methylol (methylol ether and/or methylol preferred as cross-linking active groups of aminoplast resins), hydroxyl/free isocyanate, hydroxyl/blocked isocyanate, (meth)acryloyl/CH-acid groups. Provided they are compatible with each other, several such complementary functionalities may also be present alongside each other in a water-based base lacquer. The cross-linking agents which are optionally present in the water-based base lacquer may be present individually or as a mixture.
Water-based base lacquers according to the invention contain colour and/or effect providing pigments and optionally fillers. Examples of colour providing inorganic or organic pigments and fillers are titanium dioxide, micronised titanium dioxide, iron oxide pigments, carbon black, silicon dioxide, barium sulfate, micronised mica, talcum, kaolin, chalk, sheet silicates, azo pigments, phthalocyanine pigments, quinacridone pigments, pyrrolopyrrol pigments, perylene pigments. Examples of effect providing pigments are metal pigments, e.g. consisting of aluminium, copper or other metals; interference pigments such as e.g. metal oxide-coated metal pigments, e.g. titanium dioxide-coated aluminium, coated mica such as e.g. titanium dioxide-coated mica, graphite effect pigments, platelet-shaped iron oxide, platelet-shaped copper phthalocyan
Bosch Werner
Kraus Vom Cleff Oliver
Taschner Marco
Dawson Robert
E. I. du Pont de Nemours and Company
Keehan Christopher
Lerman Bart E.
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