POLYTRIMETHYLENE ETHER DIOL BASED COATING COMPOSITION AND USE THEREOF

1 . A coating composition comprising a film forming binder consisting essentially of:

A) a polyester having one or more crosslinkable functional groups and having a glass transition temperature (Tg) in a range of from −75° C. to 5° C.;

B) an acrylic polymer having one or more crosslinkable functional groups and having a glass transition temperature (Tg) in a range of from −40° C. to 5° C.;

C) a polytrimethylene ether diol having a Mn (number average molecular weight) in a range of from 500 to 10,000; and

D) a crosslinking component containing at least one crosslinking agent having one or more crosslinking functional groups reacting with said crosslinkable functional groups.

2 . The coating composition of claim 1 , wherein the polytrimethylene ether diol has a Mn in a range of from 500 to 4,000, a Tg of about −75° C. and a hydroxyl number in a range of from 20 to 200.

3 . The coating composition of claim 2 , wherein the polytrimethylene ether diol is a blend of high and low molecular weight polytrimethylene ether diols wherein the high molecular weight polytrimethylene ether diol has an Mn in a range of from 1,000 to 4,000 and the low molecular weight polytrimethylene ether diol has an Mn in a range of from 150 to 500 and the average Mn of the blend is in a range of from 500 to 4,000.

4 . The coating composition of claim 1 , wherein the polytrimethylene ether diol is polymerized from bio-derived 1,3-propanediol.

5 . The coating composition of claim 1 , wherein at least one of said one or more crosslinking functional groups is isocyanate group.

6 . The coating composition of claim 1 , wherein the polyester is selected from: one or more linear polyesters; one or more branched copolyesters; or a combination thereof.

7 . The coating composition of claim 6 , wherein said linear polyesters have a weight average molecular weight in a range of from 1,000 to 40,000 and are polymerized from monomers selected from the group consisting of benzoic acid, pentaerythritol, neopentyl glycol, isophthalic acid, phthalic acid, adipic acid, and a combination thereof.

8 . The coating composition of claim 6 , wherein said branched polyesters have a weight average molecular weight in a range of from 1,000 to 50,000 and are polymerized from monomers selected from the group consisting of caprolactone, dimethylol propionic acid, pentaerythritol, and a combination thereof.

9 . The coating composition of claim 1 , wherein the crosslinking agent is one or more organic polyisocyanates selected from the group consisting of aliphatic polyisocyanates, cycloaliphatic polyisocyanates, aromatic polyisocyanates, tri-functional isocyanates and isocyanate adducts.

10 . The coating composition of claim 1 , further comprising one or more solvents, one or more pigments, ultraviolet light stabilizers, ultraviolet light absorbers, antioxidants, hindered amine light stabilizers, leveling agents, rheological agents, thickeners, antifoaming agents, wetting agents, catalysts, or a combination thereof.

11 . A substrate coated with the coating composition of claim 1 .

12 . The substrate of claim 11 , wherein said substrate an existing epoxy primer layer.

13 . A process for coating a substrate comprising the steps of:

(A) applying a coating composition over said substrate to form a coating layer, wherein said coating composition comprises a film forming binder consisting essentially of:

(i) a polyester having one or more hydroxyl crosslinkable functional groups and having a glass transition temperature (Tg) in a range of from −75° C. to 5° C.;

(ii) an acrylic polymer having one or more crosslinkable functional groups and having a glass transition temperature (Tg) in a range of from −40° C. to 5° C.;

(iii) a polytrimethylene ether diol having a Mn (number average molecular weight) a range of from 500 to 10,000; and

(iv) a crosslinking component containing at least one crosslinking agent having one or more crosslinking functional groups reacting with said crosslinkable functional groups; and

(B) curing said coating layer to form a coating on said substrate.

14 . The process of claim 13 , wherein the polytrimethylene ether diol is polymerized from bio-derived 1,3-propanediol.

15 . The process of claim 13 , wherein at least one of said one or more crosslinkable functional groups is hydroxyl groups, and wherein at least one of said one or more crosslinking functional groups is isocyanate group.

16 . A substrate coated with the process of claim 13 .

17 . The substrate of claim 16 , wherein said substrate has an existing epoxy primer layer.