Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2002-04-26
2003-08-05
Gobb, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S069000, C528S071000, C525S063000, C525S124000, C524S839000, C524S840000, C427S407100
Reexamination Certificate
active
06602972
ABSTRACT:
The present invention relates to novel self-crosslinking polyurethanes and to novel self-crosslinking, polyurethane-based graft copolymers. The present invention further relates to novel processes for preparing self-crosslinking polyurethanes and self-crosslinking, polyurethane-based graft copolymers. The present invention additionally relates to the use of the novel self-crosslinking polyurethanes and of the novel self-crosslinking, polyurethane-based graft copolymers for preparing self-crosslinking coating materials, adhesives, and sealing compounds. The present invention relates, furthermore, to novel self-crosslinking coating materials, adhesives, and sealing compounds, especially aqueous self-crosslinking coating materials, adhesives, and sealing compounds. The present invention relates not least to novel coatings, adhesive films, and seals obtainable from the novel, especially aqueous, self-crosslinking coating materials, adhesives, and sealing compounds. The present invention relates in particular to decorative and/or protective, single-coat or multicoat paint systems, especially multicoat color and/or effect paint systems.
In the context of the present invention, the term “self-crosslinking” denotes the property of a binder (regarding the term cf. Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, “Binders”, pages 73 and 74) to undergo crosslinking reactions with itself. A precondition for this is that the binders already contain both types of complementary reactive functional groups necessary for crosslinking. Externally crosslinking, on the other hand, is used to denote those coating materials, adhesives, and sealing compounds in which one type of the complementary reactive functional groups is present in the binder and the other type in a curing or crosslinking agent. For further details on this point, refer to Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, “Curing”, pages 274 to 276, especially page 275, bottom.
Externally crosslinking graft copolymers soluble or dispersible in water are known from European patent EP-A-0 608 021. They consist of a core comprising a hydrophobic olefinically unsaturated polyurethane and a shell comprising a hydrophilic acrylate copolymer having an acid number of from 30 to 120 mg KOH/g. The hydrophobic olefinically unsaturated polyurethane is prepared by reacting low molecular mass diols or polyester diols with an acid number of less than 5 mg KOH/g with diisocyanates and 1-(1-isocyanato-1-methylethyl)-3-(1-methylethenyl)benzene (dimethyl-m-isopropenyl-benzyl isocyanate), thereby giving, in particular, terminal ethylenearylene groups. Thereafter, a mixture of olefinically unsaturated monomers is polymerized in solution in the presence of the hydrophobic olefinically unsaturated polyurethane, after which the resulting graft copolymer is neutralized and dispersed in water to give a secondary dispersion. These known secondary dispersions are used for preparing clearcoat materials. Pigmented coating materials or sealing compounds and adhesives are not disclosed by EP-A-0 608 021.
German patent DE-C-197 22 862 discloses an externally crosslinking graft copolymer obtainable by polymerizing olefinically unsaturated monomers in a dispersion of an olefinically unsaturated polyurethane containing hydrophilic functional groups and having on average from 0.05 to 1.1 polymerizable double bonds per molecule. For the preparation of the polyurethane main chains it is possible, in accordance with DE-C-197 22 862, to use not only diisocyanates but also polyisocyanates, whose functionality is decreased by adding monoisocyanates. 1-(1-Isocyanato-1-methylethyl)-3-(1-methylethenyl)benzene is given as an example of a monoisocyanate. Where used, it contributes to a certain extent to the polymerizable double bond content of the polyurethane, although the compounds envisaged for introducing it are primarily compounds which contain isocyanate-reactive functional groups and olefinically unsaturated double bonds, such as hydroxyalkyl (meth)acrylates, for example.
The same externally crosslinking polyurethane and the externally crosslinking graft copolymer based on it are also disclosed by German patent application DE-A-196 45 761. There again, 1-(1-isocyanato-1-methylethyl)-3-(1-methylethenyl)benzene, referred to therein as isopropenyl-alpha,alpha-dimethylbenzyl isocyanate, is used.
The known externally crosslinking graft copolymers of DE-C-197 22 862 and of DE-A-196 45 761 are in the form of primary dispersions and are very highly suitable for preparing aqueous externally crosslinking coating materials, especially aqueous basecoat materials. The aqueous basecoat materials may be used with advantage for the wet-on-wet technique, in which the aqueous basecoat material is applied to a primed or unprimed substrate and then the resultant aqueous basecoat film is dried but not crosslinked. Atop the dried aqueous basecoat film there is then applied a clearcoat material, after which the aqueous basecoat film and the clearcoat film are cured together to form a multicoat color and/or effect paint system.
These known aqueous basecoat materials are crosslinked using hydrophobic crosslinking agents which must be incorporated into the aqueous coating materials by way of cosolvents or emulsifiers. Owing to their hydrophobic properties and the resultant comparatively poor dispersion in the aqueous coating material, it is necessary to incorporate larger amounts of crosslinking agents than would be necessary per se for sufficient crosslinking and adhesion of the resulting coating, particularly of the aqueous basecoat material. Moreover, the cosolvents again raise the emission of organic substances on drying and curing, which the use of aqueous coating materials was intended specifically to decrease or prevent entirely. Moreover, residues of crosslinking agents, emulsifiers, and cosolvents have adverse effects on the so-called flash-off behavior of the known aqueous basecoat films, which is manifested in a reduction in the coat thickness above which cracking (mud cracking) and popping marks appear. Although it might be possible to a certain extent to use hydrophilic crosslinking agents to remove the disadvantages associated with the use of the cosolvents and emulsifiers, there would then be a fall in the condensation resistance and weathering stability of the corresponding coatings.
In the context of the present invention, the property of hydrophilicity denotes the constitutional property of a molecule or functional group to penetrate into the aqueous phase or to remain therein. Accordingly, in the context of the present invention, the property of hydrophobicity denotes the constitutional property of a molecule or functional group to behave exophilically with respect to water, i.e., to tend not to penetrate into water or to tend to depart the aqueous phase. For further details, refer to Römpp Lexikon Lacke und Druckfarben, Georg Thieme Verlag, Stuttgart, New York, 1998, “Hydrophilicity”, “Hydrophobicity”, pages 294 and 295.
The problems depicted above are exacerbated if the known aqueous basecoat materials are used together with powder slurry clearcoat materials for producing multicoat color and/or effect paint systems.
Moreover, in some cases the amount of olefinically unsaturated groups in the polyurethanes may prove too low for complete grafting, so that a large part of the monomers to be grafted on may form separate homopolymers and/or copolymers alongside the polyurethane, which may adversely affect the performance properties of the graft copolymers and of the coating materials, adhesives, and sealing compounds prepared using them.
Because of its high reactivity, the ethenyl-arylene group constitutes a very good grafting site for the attachment by polymerization of olefinically unsaturated monomers. However, the introduction of these groups by way of 1-(1-isocyanato-1-methylethyl)-3-(1-methylethenyl)benzene causes problems, since owing to the steric hindrance the isocyanate group is comparatively slow t
Angermüller Harald
Schwarte Stephan
Wegner Egon
BASF Coatings AG
Gobb Rachel
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