Heat cross linkable polyurethane coating compositions
AssigneeBayer Aktiengesellschaft
InventorsWilhelm Thoma, Gerhard Berndt, Josef Pedain, Walter Schroer, Waldemar Kling
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Abstract
The present disclosure is concerned with solvent free or very low solvent coating compositions suitable for use on flexible sheet form substrates particularly textile substrates. The composition comprises a urethane group-containing prepolymer with OH or CONH.sub.2 terminal groups mixed with a urea or melamine formaldehyde resin and a stable aqueous polymer dispersion or solution. The composition may also contain small amounts of an organic solvent. The coating can be applied to the substrate by direct or reverse coating techniques.
Claims15
A coating composition comprising:
- (a) from about 50 to 95% by weight of an optionally branched urethane-group-containing prepolymer having an average molecular weight of from about 500 to 25,000 which is ionic group free and contains from about 2 to 8 terminal groups selected from the group consisting of OH, CONH.sub.2 and ketoxime-urethane groups,
- (b) from about 2 to 20% by weight of a urea-and/or melamine-formaldehyde resin,
- (c) from about 3 to 50% by weight of a stable aqueous polymer dispersion and/or aqueous polymer solution having a solids content of from about 20 to 70% by weight and
- (d) from about 0 to 10% by weight of an organic solvent.
In a process for reverse coating a flexible sheet form substrate wherein a top coat is applied to a release substrate and cured, a coupling coat is then applied to the cured top coat, the substrate applied to the not fully cured coupling coat, the coupling coat cured and the three layer laminate separated from the release substrate, the improvement wherein the coupling coat comprises:
- (a) from about 50 to 95% by weight of an optionally branched urethane-group-containing prepolymer having an average molecular weight of from about 500 to 25,000 which is ionic group free and contains from about 2 to 8 terminal groups selected from the group consisting of OH, CONH.sub.2 and ketoxime-urethane groups,
- (b) from about 2 to 20% by weight of a urea- and/or melamine-formaldehyde resin,
- (c) from about 3 to 50% by weight of a stable aqueous polymer dispersion and/or aqueous polymer solution having a solids content of from about 20 to 70% by weight and
- (d) from about 0 to 10% by weight of an organic solvent.
In a process for direct coating a flexible sheet form substrate wherein the substrate is coated with an uncured coating composition and the coating is then cured, the improvement wherein said coating comprises:
- (a) from about 50 to 95% by weight of an optionally branched urethane-group containing prepolymer having an average molecular weight of from about 500 to 25,000 which is ionic group free and contains from about 2 to 8 terminal groups selected from the group consisting of OH, CONH.sub.2 and ketoxime-urethane groups,
- (b) from about 2 to 20% by weight of a urea- and/or melamine-formaldehyde resin,
- (c) from about 3 to 50% by weight of a stable aqueous polymer dispersion and/or aqueous polymer solution having a solids content of from about 20 to 70% by weight and
- (d) from about 0 to 10% by weight of an organic solvent.
Dependencies are inferred from the claim text.