Low-temperature-curable, solid polyurethane powder coating compositions containing uretdione groups
AssigneeDegussa AG
InventorsEmmanouil Spyrou, Holger Loesch, Andreas Wenning
Life of this patent
Estimating the term…
Abstract
Solid polyurethane powder coating compositions which contain uretdione groups and cure at low baking temperatures, to processes for preparing such compositions, and to their use for producing plastics, especially powder coatings, which crosslink to high-gloss or matt, light- and weather-stable coating films.
Claims33
A polyurethane powder coating composition, comprising:
- A) at least one uretdione-containing powder coating hardener based on aliphatic, (cyclo)aliphatic or cycloaliphatic polyisocyanates and hydroxyl-containing compounds, having a melting point of from 40 to 130° C., a free NCO content of less than 5% by weight, and a uretdione content of 6-18% by weight,
- B) at least one hydroxyl-containing polymer having a melting point of from 40 to 130° C., and an OH number of between 20 and 200 mg KOH/gram, and
- C) at least one catalyst of the formula [NR1R2R3R4]+[R5]−, in which R1-R4 simultaneously or independently of one another are alkyl, aryl, aralkyl, heteroaryl or alkoxyalkyl radicals, each linear or branched, unbridged or bridged with other radicals R1-R4, to form cyclic, bicyclic or tricyclic systems, possible bridging atoms including not only carbon but also heteroatoms, having 1-18 carbon atoms and each radical R1-R4 may further contain one or more alcohol, amino, ester, keto, thio, urethane, urea or allophanate groups, double bonds, triple bonds or halogen atoms, and R5 is either OH or F,
- wherein
- A) and B) are present in a ratio such that for each hydroxyl group of B) there is from 0.3 to 1 uretdione group of A), and
- the fraction of C) is 0.001-3% by weight of the total amount of A) and B).
A method of providing a catalyst to a polyurethane powder coating composition, comprising incorporating into a polyurethane powder coating composition at least one catalyst of the formula [NR1R2R3R4]+[R5]−, in which R1-R4 simultaneously or independently of one another are alkyl, aryl, aralkyl, heteroaryl or alkoxyalkyl radicals, each linear or branched, unbridged or bridged with other radicals R1-R4, to form cyclic, bicyclic or tricyclic systems, possible bridging atoms including not only carbon but also heteroatoms, having 1-18 carbon atoms and each radical R1-R4 may further contain one or more alcohol, amino, ester, keto, thio, urethane, urea or allophanate groups, double bonds, triple bonds or halogen atoms, and R5 is either OH or F.
A method of catalyzing the curing polyurethane powder coating composition, comprising reacting a polyurethane powder coating composition which contains
- A) at least one uretdione-containing powder coating hardener based on aliphatic, (cyclo)aliphatic or cycloaliphatic polyisocyanates and hydroxyl-containing compounds, having a melting point of from 40 to 130° C., a free NCO content of less than 5% by weight, and a uretdione content of 6-18% by weight, and
- B) at least one hydroxyl-containing polymer having a melting point of from 40 to 130° C., and an OH number of between 20 and 200 mg KOH/gram, in the presence of a catalytically effective amount of at least one catalyst of the formula [NR1R2R3R4]+[R5]−, in which R1-R4 simultaneously or independently of one another are alkyl, aryl, aralkyl, heteroaryl or alkoxyalkyl radicals, each linear or branched, unbridged or bridged with other radicals R1-R4, to form cyclic, bicyclic or tricyclic systems, possible bridging atoms including not only carbon but also heteroatoms, having 1-18 carbon atoms and each radical R1-R4 may further contain one or more alcohol, amino, ester, keto, thio, urethane, urea or allophanate groups, double bonds, triple bonds or halogen atoms, and R5 is either OH or F.
Dependencies are inferred from the claim text.