Flexibilized polyaspartic esters
The present invention is directed to a method of preparing polyaspartates, polyaspartates so-produced and the use thereof in a coating composition. The process broadly comprises a) transesterifying an α, β-unsaturated ester with a hydroxy functional material, b) reacting the transesterified product with a primary amine-containing compound and c) reacting any remaining primary amine groups with an α,β-unsaturated ester
1 . A process for the preparation of a polyaspartate comprising:
A) transesterifying i) an α,β-unsaturated ester of the formula:
R 1 OOC—C(R 3 )═C(R 4 )—COOR 2
where R 1 and R 2 may be identical or different and represent organic groups which are inert towards isocyanate groups at 100° C. or less, and R 3 and R 4 may be identical or different and represent hydrogen or organic groups which are inert towards isocyanate groups at 100° C. or less,
with ii) an hydroxyl functional material containing n hydroxyl groups per molecule and having a number average molecular weight of from about 62 to about 3000,
at a molar ratio of from n moles of ester per mole of n-hydroxy functional material to n+8 moles of ester per mole of n-hydroxy functional material where n represents number of hydroxy groups in said hydroxy functional material and is a number of from 2 to 8,
B) reacting the resultant product with a compound containing one or more primary amine groups in an amount of at least one mole of amine compound per α,β-unsaturated ester group, and
C) reacting any remaining primary amine groups with an unsaturated ester of the formula:
R 1 OOC—C(R 3 )═C(R 4 )—COOR 2
where R 1 , R 2 , R 3 and R 4 are as defined above.
2 . The process of claim 1 , wherein R 1 and R 2 represent alkyl groups containing 1 to 9 carbon atoms.
3 . The process of claim 1 , wherein R 3 and R 4 represent hydrogen.
4 . The process of claim 1 , wherein said molar ratio is from n moles of ester per mole of n-hydroxy functional material to n+4 moles of ester per mole of n-hydroxy functional material.
5 . The process of claim 4 , wherein said molar ratio is from n moles of ester per mole of n-hydroxy functional material.
6 . The process of claim 1 , wherein the transesterification is conducted at a temperature of from about 50 to about 300° C.
7 . The process of claim 1 , wherein said compound containing primary amine groups is selected from the group consisting of 1-amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane, bis-(4-aminocyclo-hexyl)-methane, bis-(4-amino-3-methylcyclohexyl)-methane, 1,6-diamino-hexane, 2-methyl pentamethylene diamine and ethylene diamine.
8 . The process of claim 1 , wherein said amount in step B) is from at least one mole of amine compound per α,β-unsaturated ester group up to 5 moles of amine compound per α,β-unsaturated ester group.
9 . The product of the process of claim 1 .
10 . A coating composition comprising:
a) a polyisocyanate component and
b) an isocyanate-reactive component containing
b1) the aspartate of claim 1 and
b2) optionally other isocyanate-reactive components.