Abstract A polyurethane topcoat composition is provided comprising a water-free organic solvent solution containing from 0.5-2.6 isocyanate equivalents of the biuret of 1,6-hexamethylene diisocyanate per hydroxy equivalent of the polyesterification reaction product of the components set forth below having an acid number of less than 7: ______________________________________ Parts by Permitted
Component Weight Variation
______________________________________
1,6-hexanediol 11.63 ± 1.0
di-(2-hydroxyethyl)
dimethylhydantoin
20.92 ± 1.0
trimethylol propane
17.75 ± 1.0
dimethyl terephthalate
28.10 ± 1.0
adipic acid 21.15 ± 1.0
______________________________________
A polyurethane topcoat composition comprising a water-free organic solvent solution containing from 0.5-2.6 isocyanate equivalents of the biuret of 1,6-hexamethylene diisocyanate per hydroxyl equivalent of the polyesterification reaction product of the components set forth below having an acid number of less than 7: ______________________________________
Parts by Permitted
Component Weight Variation
______________________________________
1,6-hexanediol 11.63 ± 1.0
di-(2-hydroxyethyl)
dimethylhydantoin
20.92 ± 1.0
trimethylol propane
17.75 ± 1.0
dimethyl terephthalate
28.10 ± 1.0
adipic acid 21.15 ± 1.0
______________________________________
Claim 2
Dependent Claim
76 words
A polyurethane topcoat composition comprising a water-free organic solvent solution containing from 0.5-2.6 isocyanate equivalents of the biuret of 1,6-hexamethylene diisocyanate per hydroxyl equivalent of the polyesterification reaction product of the components set forth below having an acid number of less than 7: ______________________________________
Parts by Permitted
Component Weight Variation
______________________________________
1,6-hexanediol 11.63 ± 1.0
di-(2-hydroxyethyl)
dimethylhydantoin
20.92 ± 1.0
trimethylol propane
17.75 ± 1.0
dimethyl terephthalate
28.10 ± 1.0
adipic acid 21.15 ± 1.0
______________________________________
Claim 3
Dependent Claim
19 words
A polyurethane topcoat as recited in claim 1 in which the isocyanate to hydroxyl ratio is 1.5:1 to 2.6:1.
Claim 4
Dependent Claim
19 words
A polyurethane topcoat as recited in claim 1 in which the permissible variation for each component is ±0.5 parts.
Claim 5
Dependent Claim
17 words
A polyurethane topcoat as recited in claim 1 in which said composition is pigmented with titanium dioxide.
Claim 6
Dependent Claim
44 words
A polyurethane topcoat as recited in claim 1 in which said polyesterification reaction product is made by transesterifying said dimethyl terephathalate with the hydroxylfunctional components until at least 80% of theoretical methanol has been removed, and then directly esterifying the product with adipic acid.
Claim 7
Dependent Claim
37 words
A polyurethane topcoat as recited in claim 5 in which said transesterification is carried out to remove at least 90% of theoretical methanol and the final polyesterification reaction product has an acid number of less than 5.