SILICONE-MODIFIED POLYESTER COATING
The present invention provides a coating composition having excellent weatherability and durability. The coating composition includes a binder system comprising a durable polyester resin and a siliconized polyester resin having up to about 45 wt % silicone content. Coated articles with the coating composition applied to at least a portion of a surface thereof are also provided.
1 . A cured coating formed from a thermosetting coating composition, the composition comprising:
a binder system including:
a first polyester resin; and
a second polyester resin having up to about 30% silicone content, based on the total weight of the first and second polyester resins;
about 5 to 15 wt % crosslinking agent;
about 0.1 to 2 wt % catalyst; and
about 0.01 to 0.5 wt % flow agent,
wherein the cured coating is a weatherable exterior coating having a 60° gloss rating of about 5 to 90, and demonstrating a change in color (4E) of less than one unit after at least about 1000 MJ of exposure to direct sunlight.
2 . The coating of claim 1 , wherein the second resin has molecular weight (M n ) of less than about 10,000 amu, and a Mw of less than about 15,000.
3 . The coating of claim 1 , wherein the second resin has a hydroxyl number of at least 75.
4 . The coating of claim 1 , wherein the second resin is a silicone-modified polyester.
5 . The coating of claim 1 , wherein the second resin is a silicone-modified polyester made by a method comprising:
providing a polyol prepared by co-condensation of at least one alcohol with at least one silanol; and
esterifying the polyol by reaction with at least one acid-functional compound, wherein the reaction is carried out in the presence of a titanium-based catalyst.
6 . The coating of claim 1 , wherein the first resin is a durable polyester resin.
7 . The coating of claim 1 , wherein the crosslinking agent is an aminoplast resin crosslinker.
8 . The coating of claim 1 , wherein the crosslinking agent is a melamine cure additive.
9 . The coating of claim 1 , wherein the catalyst is an acid catalyst.
10 . The coating of claim 1 , wherein the catalyst is blocked p-toluene sulfonic acid.
11 . The coating of claim 1 , wherein the catalyst is non-blocked p-toluene sulfonic acid.
12 . The coating of claim 1 , wherein the composition further comprises a pigment.
13 . The coating of claim 1 , wherein the composition further comprises a pigment is dispersed in the second polyester resin.
14 . The coating of claim 1 , wherein the composition further comprises a pigment dispersed in the first polyester resin.
15 . The coating of claim 1 , wherein the composition further comprises a pigment dispersed in a blending polyester resin.
16 . The coating of claim 1 , wherein the composition further comprises a pigment dispersed in the crosslinking agent.
17 . The coating of claim 1 , wherein the composition further comprises about 6% to 10% of a blend of polar solvents, based on the total weight of the composition.
18 . The coating of claim 1 , wherein the composition further comprises about 6% to 10% of one or more flatting agents, based on the total weight of resin solids in the composition.
19 . The coating of claim 1 , wherein the composition further comprises about 3% to 10% of one or more waxes, based on the total weight of resin solids in the composition.