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
2000-07-24
2002-11-19
Wu, David W. (Department: 1713)
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...
C524S591000, C524S839000, C524S840000, C525S453000, C525S509000, C525S540000
Reexamination Certificate
active
06482885
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to light-stable coating compositions containing a mixture of at least two mutually compatible cosolvent-free, aqueous, anionic dispersions A and B of polyurethane polyureas.
The present invention also relates to recyclable strippable coating compositions consisting of at least two different cosolvent-free, aqueous, anionic dispersions A and B of polyurethane polyureas, a process for their production and their use as coating compositions, preferably as strippable coating compositions for the temporary protection of motor vehicles, aircraft, steel and aluminium profiles, glass and plastics discs and arbitrary other substrates, and processes for the recovery of the used stripped coating layers.
2. Description of the Prior Art
Anionic polyurethane polyurea dispersions are known. Cosolvent-free, aqueous, anionic polyurethane dispersions, processes for their production and their use as coating compositions, coating agents, adhesives and strippable coating compositions are also known. DE-A 19 653 585, describes polyurea dispersions which after physical drying at 20° to 100° C., preferably at 20° to 80° C., provide transparent, high-gloss UV-resistant, temperature-resistant (−30° to 80° C.) coatings that are resistant to precipitations (of an organic or inorganic nature), and that on the one hand bond well to substrates and on the other hand can easily be removed by stripping. The tear strength and elongation of the coatings layers are appropriately high. A coatings dispersion that can be obtained according to DE-A 19 653 585 is denoted hereinafter as dispersion A.
Mixtures of polyolefins used as strippable coating compositions for automobiles are known from WO 98/23692. However these mixtures do not contain any polyurethane (PUR) constituents. The strippable coatings described therein are also not recyclable.
There is a need for a higher hardness and lower elongation of the polyurethane ureas A used as recyclable strippable coating compositions.
Accordingly, an object of the present invention is to provide new aqueous anionic polyurethane polymers that can be used without any problem and in an environmentally friendly manner and that produce coating compositions and coatings that satisfy requirements with regard to mechanical properties, weathering, light-resistance, transparency, temperature resistance, strippability, water resistance, resistance to precipitations (of an organic and inorganic nature) and recyclability and which also exhibit a high hardness and low elongation.
One possibility of producing a higher degree of hardness of the dried coating layers is to branch the polymer molecules. Branched polyurethane polyureas, such as are described in EP-A 242 731, have such a high hardness that they are used for producing coatings for hard, non-flexible substrates, for example as parquet coatings. When applied in a cosolvent-free manner to glass plates, the satisfactorily adhering coating layers exhibit cracks after drying at room temperature. These coating layers are not strippable as a film. A dispersion produced from EP-A 242 731 is denoted hereinafter as dispersion B.
It has now surprisingly been found that the desired application properties are obtained if at least two mutually miscible, cosolvent-free, aqueous anionic dispersions A and B of polyurethane polyureas are mixed, whose dry films A have a glass transition temperature Tg in the range from −30° to −45° C. and dry films B have a first Tg in the range from −30° to −45° C. and a second Tg in the range from +45° to +60° C., and the mixture of A and B as a dry film has only one Tg in the range from −30° to −45° C.
It is extremely surprising that a mixture of dispersions A and dispersions B forms coherent, strippable and recyclable films, since the person skilled in the art must have expected that the good adhesion of the dispersion B would also be transferred to the coating composition mixture of dispersion A and B, impeding strippability. This, however, is not the case. With the mixtures according to the invention, high-gloss, highly transparent and hard coating layers are obtained having a high filling capacity and good strippability and recyclability.
SUMMARY OF THE INVENTION
The present invention relates to light-stable coating compositions comprising a mixture of at least two cosolvent-free aqueous, anionic dispersions A and B of polyurethane polyureas, wherein polyurethane dispersion A as a dry film has a Tg in the range from −30° to −45° C. and the polyurethane dispersion B as a dry film has a first Tg in the range from −30° to −45° C. and a second Tg in the range from +45° to +60° C., and the mixture of A and B as a dry film has only one Tg in the range from −30° to −45° C.
The present invention also relates to light-stable coatings applied in the form of a mixture of at least two mutually compatible aqueous dispersions to arbitrary substrates and are dried at temperatures of up to 150° C.
The present invention also relates to a process for producing the light-stable coating compositions according to the invention, wherein at least two different cosolvent-free, aqueous, anionic dispersions A and B of polyurethane polyureas are prepared separately and aqueous dispersions A and B are then mixed in weight ratios of 50 to 90, preferably 55 to 85 parts of A to 10 to 50, preferably 15 to 45 parts of B (based on solids).
The present invention further relates to the use of mixtures of the aqueous dispersions A and B for preparing high-gloss, light-stable, water-resistant, solvent-free coatings for protecting vehicles, steel, aluminium and metal objects of all types, glass and plastics of all types, mineral substrates, brickwork or natural stones, for preventing corrosion of ships, bridges, aircraft and railways, and for protecting wood and natural objects and other substrates by dipping, knife coating, casting, spraying, brushing or injection, followed by drying at 20° to 150° C.
The present invention relates to the use of mixtures of the aqueous dispersions A and B as recyclable strippable coating compositions for the temporary protection of vehicles, railways, ships, furniture, metal objects, mineral objects, glass and plastics objects and other substrates by dipping, knife coating, casting, spraying, brushing or injection, followed by drying at 20° to 100° C., preferably 20° to 80° C., by heat or infra-red light, microwave irradiation or sonic irradiation.
The present invention also relates to the use of the used, stripped coatings according to the invention as recycled material, wherein the used, stripped coatings are mechanically comminuted, optionally after prior cleaning, are dissolved, optionally while heating, in acetone, water and neutralizing agents, preferably ammonia, the acetone is optionally distilled off under reduced pressure, and the recovered stripped coating composition is obtained in the form of an aqueous dispersion for renewed use.
The present invention also relates to the use of the used, stripped coating layers according to the invention as recycled material, wherein the used, stripped coating layers are mechanically comminuted, optionally after prior cleaning, and are then compressed in heatable presses under application of temperature and pressure to form polyurethane plates, or the comminuted coating layers are extruded in an extruder under application of temperature, shear forces and conveying, into thermoplastic endless strands, and the resultant strands are granulated by known granulation methods into cylindrical, spherical, lens-shaped or lozenge-shaped granulates.
The present invention also relates to strippable coatings for the temporary protection of motor vehicles, aircraft, steel and aluminium profiles, glass and plastics discs and arbitrary other substrates.
Finally, the present invention relates to the use of the resultant granulates for producing industrial and technical articles as thermoplastic elastom
Gruttmann Horst
Kurek Gerald
Meixner Jürgen
Möller Heino
Müller Hanns-Peter
Bayer Aktiengesellschaft
Egwim Kelechi
Gil Joseph C.
Roy Thomas W.
Wu David W.
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