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
1999-08-11
2002-04-30
Gorr, 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...
C525S124000, C524S840000, C428S423100
Reexamination Certificate
active
06380342
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to aqueous coating compositions and to their preparation and use, especially for producing coatings that are resistant to chemicals and to the impact of stones.
2. Description of the Prior Art
In the automotive industry organic solutions of polyester resins, stoved with melamine resins or blocked polyisocyanates as hardener, have previously been used for coatings that are resistant to the impact of stones. A process for the preparation of these stoving fillers is described, for example, in DE-A 3,918,510.
Modern, aqueous binders are capable of replacing organic solvent-based binders in many applications. In some applications of such lacquers, such as in the automotive industry, the high property requirements for both the ready-for-use coating compositions and the resulting coatings have not been satisfied.
For example, EP-A 024,727 describes a stoving lacquer based on a combination of epoxy resin-phosphoric acid ester, a water-dilutable polyester and water-soluble melamine resins. DE-A 4,000,748 describes aqueous automotive fillers based on water-dilutable hydroxy-functional polyester-polyurethane resins, optionally other binders and water-soluble amino resins. DE-A 3,813,866 describes hydrofillers of water-dilutable polyurethane resins, water-dilutable polyesters modified with epoxy resins, and optionally water-dilutable aminoplastic resins.
The high demands which the automotive industry in particular places on filler coatings have not yet been completely met by those coatings. An improvement has been achieved with polyisocyanate-crosslinked filler coatings (M. Bock, H. Casselmann, H. Blum, “Progress in Development of Waterborne PUR-Primers for the Automotive Industry”, Proc. Waterborne, Higher Solids and Powder Coatings Symp. New Orleans 1994). However, all of the coating compositions described have the disadvantage that the water-dilutable polyester or polyester-polyurethane resins used are very sensitive to hydrolysis and, thus, the systems have limited storage stability. These systems are not always able to meet high property requirements with regard to chemical resistance.
Hydrolytically stable aqueous dispersions can be prepared, for example, which are based on copolymers of (meth)acrylic acid esters. In addition to improved storage stability, polyacrylates also have greater resistance to chemicals than do polyesters or polyester-polyurethanes. Such systems are not used in the field of coatings that are resistant to the impact of stones, however, since lacquers based on polyesters or polyesters-polyurethanes are markedly superior to polyacrylates with respect to mechanical properties, especially elasticity.
DE-A 4,332,067 describes stoving lacquers based on polyacrylates prepared in low molecular weight oligoesters. The oligoesters used as the reaction medium for the radical polymerization have a molecular weight of <1000 g/mol. Advantages arising from the chemical linking of polyester and polyacrylate are not described. No indication is given of a polyol composition suitable for elastic coatings that is resistant to the impact of stones.
DE-A 4,427,227 describes a non-yellowing stoving lacquer based on a polyacrylate-grafted polyester and a water-dilutable melamine resin and/or a polyisocyanate which has been rendered hydrophilic. Again, polyol compositions suitable for elastic coatings that are resistant to the impact of stones are not disclosed.
An object of the present invention is to provide aqueous coating compositions which are storage stable and have improved resistance to chemicals and excellent resistance to the impact of stones.
Surprisingly, it has been found that this object can be achieved by the use of a combination of specific aqueous polyols and blocked polyisocyanates. The polyol dispersions according to the invention are characterized in that they contain graft copolymers based on polyester-polyacrylates in which the polyester component is based on long-chain aliphatic monocarboxylic acids and &agr;,&bgr;-unsaturated carboxylic acids. The suitability of the polyol dispersions according to the invention as elastic stoving lacquers for automotive fillers is surprising because previously when stoving lacquers containing a high proportion of polyacrylate were used for automotive fillers, they did not satisfy the high property requirements with respect to elasticity and resistance to the impact of stones.
SUMMARY OF THE INVENTION
The present invention relates to an aqueous dispersion containing
A) a polyol component containing
A1) 20 to 60 wt. %, based on the resin solids content of polyol component A), of a polyester resin containing 10 to 60 wt. %, based on the weight of the polyester resin, of one or more aliphatic, saturated or unsaturated monocarboxylic acids having 8 to 30 carbon atoms, and 0.4 to 5 wt. %, based on the weight of the polyester resin, of one or more radically polymerizable &agr;,&bgr;-unsaturated mono- or di-carboxylic acids having 3 to 8 carbon atoms, or their anhydrides, and
A2) 40 to 80 wt. %, based on the resin solids content of polyol component A), of a polyacrylate, which is prepared in the presence of component A1), and
B) 1 to 70 wt. %, based on the resin solids content of the aqueous dispersion, of one or more blocked polyisocyanates.
The present invention relates also to the use of the resulting dispersions to prepare stoving coatings, preferably for the initial lacquering of motor vehicles, especially as stoving fillers.
DETAILED DESCRIPTION OF THE INVENTION
The aqueous dispersions of the present invention contain 1 to 70 wt. %, preferably 20 to 50 wt. % by weight of polyisocyanate component B), based on the resin solids content of the aqueous dispersion. The aqueous dispersions also preferably contain 30 to 99 wt. %, more preferably 50 to 80 wt. % by weight of polyol component A), based on the resin solids content of the aqueous dispersion. Polyol component A) contains 20 to 60 wt. %, preferably 40 to 55 wt. %, of polyester component A1) and 40 to 80 wt. %, preferably 45 to 60 wt. %, of polyacrylate component A2), wherein the preceding percentages are based on the resin solids content of polyol component A).
Polyester component A1) preferably has a number average molecular weight of 500 to 6000, more preferably 1000 to 3000, an acid number of <15, preferably <12, mg of KOH/g, and an OH number of 50 to 250, more preferably 100 to 180 mg of KOH/g. Polyester component A1) is prepared by the reaction of
AI
1)
10 to 60%, preferably 30 to 50%, of one or more aliphatic, saturated or unsaturated monocarboxylic acids having 8 to 30 carbon atoms, preferably 80 to 100 wt. % of component AI
1)
is selected from aliphatic monocarboxylic acids having 12 to 20 carbon atoms and less than two C═C double bonds per molecule.
AI
2
0.4 to 5%, preferably 0.6 to 2%, of one or more &agr;,&bgr;-unsaturated mono- or di-carboxylic acids having 3 to 8 carbon atoms, or an anhydride thereof,
AI
3)
20 to 60%, preferably 25 to 40%, of one or more aliphatic, cycloaliphatic or aromatic di-, tri- or tetra-carboxylic acids having 2 to 40, preferably 2 to 20, carbon atoms, or their anhydrides,
AI
4)
10 to 60%, preferably 20 to 50%, of one or more aliphatic alcohols having 1 to 4 OH groups per molecule,
AI
5)
0 to 10% of one or more aromatic monocarboxylic acids,
AI
6)
0 to 10% of other COOH— or OH-reactive compounds, such as epoxides, isocyanates, amines or oxazolines, having 1 to 4, preferably 1.9 to 2.5, functional groups per molecule,
wherein the percentages of components AI
1)
to AI
6)
are weight percents and add up to 100.
Polyacrylate component A2) is prepared in the presence of polyester component A1) by the radical polymerization of a mixture of by the reaction of
AII
1)
20 to 70%, preferably 25 to 50%, of one or more non-functional esters of &agr;,&bgr;-unsaturated carboxylic acids having 3 to 12 carbon atoms and aliphatic or cycloaliphatic monoalcohols having 1 to 20 carbon atoms,
AII
2)
1 to 10%, preferably 2 to 7%, of one or more &agr;,&bgr;
Blum Harald
Irle Christoph
Möller Heino
Petzoldt Joachim
Bayer Aktiengesellschaft
Gil Joseph C.
Gorr Rachel
Roy Thomas W.
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