Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-01-21
2001-03-06
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S457000, C524S458000, C524S591000, C524S800000, C524S804000, C524S839000, C524S840000, C525S123000, C525S455000
Reexamination Certificate
active
06197874
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to polyurethane-polyacrylate hybrid dispersions which contain allophanate groups and to their use for wood and furniture coatings which exhibit good resistance to staining liquids.
2. Description of the Prior Art
With the aim of reducing emissions of organic solvents, aqueous coating compositions are increasingly being used instead of solvent-containing compositions. Polyurethane dispersions and polyacrylate dispersions are important classes of aqueous lacquer binder vehicles. The various options for the production of polyurethane dispersions have been compared, for example, in a review article by D. Dieterich (D. Dieterich, Prog. Org. Coatings 9,281(1981)). Polyurethane dispersions and poly-acrylate dispersions are often mixed in order obtain high-quality surface properties.
Furthermore, it is also known, particularly from the patent literature, that the polymerization by a radical mechanism of suitable vinyl monomers can be conducted in the presence of aqueous polyurethane dispersions. Examples of patent applications relating to the production of polyurethane-polyacrylate hybrid dispersions such as these include DE-A-1,953,348 and EP-A 167,188, EP-A 189,945 and EP-A308,115. When compared to a mixture of polyurethane and polyacrylate dispersions, the hybrid dispersions are of higher quality.
A considerable improvement of the performance of aqueous coatings has been achieved by the use of modern technologies. Thus, for example, EP 358 979 describes how the resistance of coatings prepared from aqueous acrylate dispersions can be improved by the addition of polyisocyanates. It is also possible to improve the coating properties of polyurethane dispersions by the addition of polyisocyanate crosslinking agents which have been rendered hydrophilic (e.g. EP-A 469,389).
In addition to the development of two-component systems of this type, attempts have been made to also achieve a significant improvement in coating properties for one-component systems, which can be applied more easily. Thus EP-A 332,326 describes how polyurethane-polyacrylate hybrid dispersions can be crosslinked by the condensation reaction of hydrazide and carbonyl groups. The oxidative crosslinking of polyurethane and polyurethane-polyacrylate hybrid dispersions is also known (Advances in Urethane Science and Technology, Volume 10, pages 121-162 (1987), 4th Nürnberg Congress “Creative Advances in Coatings Technology”, Paper 17, (1997)).
The properties of lacquers can be somewhat improved by the process steps described above, but the chemical resistance of lacquer films of polyurethane-polyacrylate hybrid dispersions, particularly their resistance to staining liquids, is unsatisfactory.
An object of the present invention is to improve the properties of aqueous, one-component polyurethane-polyacrylate hybrid dispersions, and in particular their resistance to staining liquids.
This object may be achieved with the polyurethane-polyacrylate hybrid dispersions according to the invention, which are based on special polyurethane dispersions containing allophanate groups and exhibit a decisive improvement in resistance to staining liquids.
SUMMARY OF THE INVENTION
The present invention relates to polyurethane-polyacrylate hybrid dispersions comprising
A) 20 to 99% by weight, based on resin solids, of a polyurethane wherein i) the polyurethane is rendered hydrophilic by ionic and/or nonionic hydrophilic groups and ii) the polyisocyanate component used to prepare the polyurethane contains an aliphatic or cycloaliphatic polyisocyanate containing allophanate groups, and
B) 1 to 80% by weight, based on resin solids) of a polyacrylate polymer,
wherein the sum of components A and B is 100%, based on the total weight of A) and B).
The present invention also relates to the use of these hybrid dispersions for coating substrates, in particular wood.
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patent: 4644030 (1987-02-01), Loewrigkeit et al.
patent: 4730021 (1988-03-01), Zom et al.
patent: 4983662 (1991-01-01), Overbeek et al.
patent: 5137961 (1992-08-01), Goos et al.
patent: 5380792 (1995-01-01), Renk
patent: 0 469 389 (1994-04-01), None
patent: 705 855 (1996-04-01), None
Blum Harald
Brahm Martin
Irle Christoph
Kremer Wolfgang
Luhmann Erhard
Bayer Aktiengesellschaft
Gil Joseph C.
Niland Patrick D.
Roy Thomas W.
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