Method of coating substrates comprising polyurethane

Details Method of coating substrates comprising polyurethane Method of coating substrates comprising polyurethane

1999-07-07

2001-07-24

Cain, Edward J. (Department: 1714)

Coating processes

With post-treatment of coating or coating material

Heating or drying

C427S385500, C427S393500

Reexamination Certificate

active

06265028

ABSTRACT:

The present invention relates to a method of coating a substrate by applying an aqueous polymer formulation comprising a film-forming polymer A in the form of its aqueous dispersion onto a substrate, the substrate consisting essentially of polyurethane.
Aqueous formulations based on film-forming polymers are widely employed as protective surface coating systems. The polymer in the formulation together with any fillers or pigments therein combine on drying to form a solid polymer film which protects the coated substrate against environmental effects such as sunlight, moisture and mechanical or chemical stresses.
In architectural preservation, especially in exterior applications, stringent requirements are set for the stability of such coatings. In addition to chemical resistance and high photostability they are required to have high elasticity and tear strength so that when the components experience dimensional changes as a result of fluctuating temperatures no cracks are formed in the coating. The coatings must also not become tacky at high temperatures, since that could have unwanted dirt pickup consequences. A further requirement is that the coatings show little tendency to absorb water.
Particular importance is placed on the good adhesion of the coatings to the underlying material to be sealed or to the surface of the substrate to be coated. Formulations based on aqueous polymer dispersions often fail to meet this requirement on hydrophobic substrates which consist essentially of polyurethanes (polyurethane materials), such as on polyurethane foams, despite meeting the other requirements made of them. And yet polyurethane materials find widespread use as construction materials in architecture, an example being polyurethane foams used to insulate flat-roof constructions.
WO 95/09896 and EP-A 609 793 disclose aqueous polymer formulations which comprise at least one polymer having urea groups in the form of an aqueous dispersion and at least one polyaldehyde compound. The use of such formulations as binders for emulsion paints is described.
EP-B 258 988 describes a coating composition for polyurethane foams which comprises a film-forming polymer having acetoacetyl or cyanoacetyl groups. A feature of the coating composition is its adhesion to polyurethane foam surfaces. While the tear strength of such binder polymers is enhanced by the incorporation of the functional groups, however, there is at the same time a marked reduction in the elasticity of these coatings, and thus a risk of cracking in the coating.
WO 98/16589 discloses the use of polymer formulations for coating hydrophobic surfaces, said formulations comprising a polymer having keto or aldehyde groups and at least one compound having two or more primary amino groups, such as the dihydrazide of a dicarboxylic acid. The coatings feature high elasticity and tear strength.
It is an object of the present invention to provide a formulation based on an aqueous polymer dispersion (aqueous polymer formulation) which to a high extent meets the profile of requirements made of coating compositions and which adheres well to coatings on substrates consisting essentially of polyurethanes.
We have found that this object is achieved by aqueous polymer formulations comprising at least one film-forming polymer A having urea or thiourea groups and at least one compound B having at least two aldehyde groups.
The present invention therefore provides a method of coating a substrate consisting essentially of polyurethanes, said method comprising the application of an aqueous formulation onto the substrate and said aqueous formulation comprising
i) at least one film-forming polymer A constructed from ethylenically unsaturated monomers M and present in dispersed form in the aqueous formulation, said monomers M comprising at least one monomer M
1
of the formula I
 where
R
1
and R
2
independently of one another are hydrogen, linear or branched C
1
-C
5
-alkyl or, together are a C
2
-C
4
-alkylene group
which is unsubstituted or substituted once or twice by C
1
-C
5
-alkyl, C
1
-C
4
-alkyloxy and/or hydroxyl,
X is oxygen or sulfur, and
R
3
is a monoethylenically unsaturated radical of 2 to 20 carbon atoms,
and at least one monomer M2 copolymerizable with said monomer M1, and
ii) at least one compound B having two or more aldehyde groups.
Substrates consisting essentially of polyurethanes (polyurethane materials) embrace moldings, molding compounds and components made of polyurethanes, coatings, brushing compositions based on polyurethanes and solid polyurethane foams in the form, for example, of constructional slab stock or foam insulation. They generally contain at least 50% by weight, based on their total mass, of polyurethanes, e.g., polyesterurethanes and/or polyetherurethanes. The surfaces of substrates comprising polyurethane are generally of particularly low tension, generally <50 mN/m, preferably <40 mN/m and, in particular, <30 mN/m, and of low polarity, and are not adhered to well, if at all, by conventional coating compositions. The formulations of the invention are particularly suitable for coating the surfaces of polyurethane foams such as those used as slabstock in flat-roof construction or as insulating materials. A compilation of typical polyurethane foams is given for example in A. Franck, Kunststoffkompendium, 4th Edition, Vogel Verlag, Würzburg 1996, pp. 393-406, especially Table 8.4.1.
Preferred monomers M1 are
where R
3
is as defined above and each of the substituents R
4
, R
5
in formula Ib can be hydrogen, a hydroxyl group or a C
1
-C
4
-alkyloxy group. Preferably, R
4
and R
5
are both hydrogen or R
4
is hydrogen and R
5
is a C
1
-C
4
-alkyloxy group.
Preference is given to monomers M1 of formula I in which X is oxygen.
R
3
is generally a monoethylenically unsaturated radical of 2 to 20 carbon atoms. R
3
is preferably a radical of the formula
CH
2
═CH—X—Y— or CH
2
═C(CH
3
)—X—Y—
where X is a single bond, CH
2
, a phenylene group, a carbonyl group, a carbonyloxy group or a carbamoyl group and Y is a single bond or a C
1
-C
10
-alkylene group which is unsubstituted or substituted by hydroxyl and/or carbonyl groups and/or is interrupted by one or more nonadjacent oxygen atoms or imino groups.
Examples of suitable radicals R
3
are CH
2
═CH—, CH
2
═CH—CH
2
—, CH
2
═CH—CH
2
—O—CH
2
—CH(OH)—CH
2
—, CH
2
═CH—CH
2
—O—CH
2
—CH(OH)—CH
2
—NH—CH
2
—CH
2
—CH
2
═CH—CH
2
—O—CH
2
—CH(OH)—CH
2
—O—CH
2
—CH
2
—CH
2
═C(CH
3
)—CH
2
—, CH
2
═C(CH
3
)—C(O)—, CH
2
═CH—C(O)—CH
2
═CH—C(O)—O—CH
2
—CH
2
—, CH
2
═CH—C(O)—NH—CH
2
—CH
2
—, CH
2
═C(CH
3
)—C(O)—O—CH
2
—CH
2
—, CH
2
═C(CH
3
)—C(O)—NH—CH
2
—CH
2
—, CH
2
═CH—C(O)—O—CH
2
—C(O)—O—CH
2
—CH
2
—, CH
2
═CH—C(O)—O—CH
2
—C(O)—NH—CH
2
—CH
2
—CH
2
═CH—C(O)—NH—CH
2
—C(O)—O—CH
2
—CH
2
—, CH
2
═C(CH
3
)—C(O)—O—CH
2
—C(O)—O—CH
2
—CH
2
—, CH
2
═C(CH
3
)—C(O)—O—CH
2
—C(O)—NH—CH
2
—CH
2
—CH
2
═C(CH
3
)—C(O)—NH—CH
2
—C(O)—O—CH
2
—CH
2
—.
Advantageous copolymerizable monomers M1 are the following:
N-vinylethyleneurea,
N-[(methacryloyloxyacetoxyethyl)]ethyleneurea,
N-(2-acryloyloxyethyl)ethyleneurea,
N-[(3-allyloxy-2-hydroxypropyl)aminoethyl]ethyleneurea,
N-(acrylamidoethyl)ethyleneurea, N-allylethyleneurea,
N-(2-methacryloyloxyacetamidoethyl)ethyleneurea, and especially
N-(2-methacryloyloxyethyl)ethyleneurea (also named
[1-(2-methacryloyloxyethyl)imidazolin-2-one]),
N-(methacrylamidoethyl)ethyleneurea and
N-[(3-allyloxy-2-hydroxypropyl)aminoethyl]ethyleneurea.
Further suitable monomers M1 are described in U.S. Pat. No 3,356,627, U.S. Pat. No. 4,104,220, U.S. Pat. No. 4,111,877, U.S. Pat. No. 4,219,454, U.S. Pat. No. 4,319,032, U.S. Pat. No. 4,500,673, U.S. Pat. No. 4,426,503, U.S. Pat. No. 5,210,199, U.S. Pat. No. 5,498,723, U.S. Pat. No. 5,567,826, EP-A 3870, EP-A 9880, EP-A 29 891, EP-A 379 892 and WO 91/12243. Yet further suitable monomers M1 are specified in a review article by R. W. Kreis and A. M. Sherman, “Developments in Ureido Function

Affiliated with

Also associated with

Rating

Method of coating substrates comprising polyurethane does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of coating substrates comprising polyurethane, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of coating substrates comprising polyurethane will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2494251