Coating compositions capable of producing surfaces with dry-erase properties

1. A waterborne coating composition comprising:

(a) a carboxylic acid functional polyacrylate having a calculated Tg of greater than 50° C. that is a reaction product of reactants comprising:

(a1) at least 50% by weight, based on the total weight of the reactants, of a hardening vinyl aromatic monomer selected from the group consisting of dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene, 3,5-dimethylstyrene, 2-ethylstyrene, α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-methoxystyrene and styrene;

(a2) a plasticizing ethylenically unsaturated monomer that does not include carboxylic acid or hydroxyl groups, the monomer selected from the group consisting of methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, iso-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, dodecyl acrylate, n-hexyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, decyl methacrylate, dodecyl methacrylate; and

(a3) a carboxylic-acid functional ethylenically unsaturated monomer selected from the group consisting of acrylic acid, (meth)acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, maleic acid monoalkyl esters, fumaric acid monoalkyl esters, itaconic acid and propylacrylic acid; and

(b) a water-miscible polyaziridine,

wherein the coating composition is substantially free of isocyanate functionality; and

wherein the carboxylic acid groups of the polyacrylate are base-neutralized during or after the reaction.

2. The coating composition of claim 1 , wherein the calculated Tg is at least 60° C.

3. The coating composition of claim 2 , wherein the calculated Tg is at least 65° C.

4. The coating composition of claim 3 , wherein the calculated Tg is at least 70° C.

5. The coating composition of claim 1 , wherein the composition has a viscosity at 23° C. of less than 1000 cPs.

6. The coating composition of claim 1 , wherein the reactants further comprise:

(a4) a hydroxyl functional ethylenically unsaturated monomer.

7. The coating composition of claim 1 , wherein (a1) comprises styrene in an amount of at least 80% by weight, based on the total weight of reactant (a1).

8. The coating composition of claim 1 , wherein the sum of monomers (a1) and (a3) comprises at least 70% by weight, based on the total weight of reactants used to make the polyacrylate.

9. The coating composition of claim 1 , comprising:

(a1) 50 to 85% by weight styrene;

(a2) 5 to 30% by weight of n-butyl acrylate, ethyl acrylate and/or 2-ethylhexyl acrylate;

(a3) 1 to 5% by weight of acrylic acid and/or methacrylic acid;

(a4) optionally 2 to 30% by weight of hydroxypropyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate and/or hydroxyethyl acrylate,

wherein the sum of the % by weights of (a1) to (a4) is 100.

10. The coating composition of claim 1 , comprising:

(i) at least 70% by weight of the carboxylic acid functional polyacrylate; and

(ii) at least 2% by weight of the water-miscible polyaziridine,

wherein the weight percents are based on the total weight of resin solids in the coating composition.

11. The coating composition of claim 1 , wherein the composition comprises no more than 0.2 equivalents of free isocyanate groups per equivalents of any isocyanate-reactive groups.

12. A method of using the coating composition of claim 1 , comprising:

(A) applying the composition to a substrate; and

(B) allowing the composition to cure at ambient temperature to form a cured coating, wherein the substrate comprises a wall, a chalkboard or a blackboard and/or a material comprising a cellulosic material, fiber board, particle board, and/or gypsum board.

13. A kit comprising:

(a) the coating composition of claim 1 ; and

(b) a marker pen.

14. A method of using the coating composition of claim 1 , comprising:

(A) applying the composition to a substrate; and

(B) allowing the composition to cure at ambient temperature to form a cured coating,

wherein the substrate is a frame of an architectural article.