Hardcoat composition comprising methyl or ethyl trialkoxy silane, articles and methods
Articles are described comprising a substrate and a hardcoat layer disposed on the substrate. The hardcoat layer comprises the hydrolyzed and condensed reaction product of a composition comprising: i) first hydrophobic silane monomer(s) having the formula R 1 Si(OR) 3 wherein R and R 1 is methyl or ethyl; ii) optional second silane monomer(s) having the formula (R 2 ) 4-m Si(OR) m or Si(OR) 4 , wherein R, R 1 and R 2 are organic groups with the proviso that R 1 is not methyl or ethyl and m ranges from 1 to 3. The hardcoat layer may further comprises 10 to 30 wt. % silica nanoparticles. A surface layer comprising a hydrophilic silane may be disposed on the hardcoat layer. Also described is a method of using an article having a rewritable surface, hardcoat coating compositions, and methods of making hardcoat compositions and articles.
1 . An article comprising:
A) a substrate;
B) a hardcoat layer disposed on the substrate wherein the hardcoat layer comprises the hydrolyzed and condensed reaction product of a composition comprising:
i) first hydrophobic silane monomer(s) having the formula R 1 Si(OR) 3 wherein R and R 1 is methyl or ethyl;
ii) optional second silane monomer(s) having the formula (R 2 ) 4-m Si(OR) m or Si(OR) 4
wherein R, R 1 and R 2 are organic groups with the proviso that R 2 is not methyl or ethyl and m ranges from 1 to 3;
wherein when present, the second silane monomer(s) is present in an amount less than 20 wt. % based on the sum of first and second silane monomers;
iii) optionally 10 to 30 wt. % silica nanoparticles;
C) a surface layer comprising a hydrophilic silane disposed on the hardcoat layer.
2 . The article of claim 1 wherein said hydrophilic silane comprises a zwitterionic silane.
3 . The article of claim 2 wherein the surface layer further comprises lithium silicate, sodium silicate, potassium silicate, or combinations thereof.
4 . The article of claim 1 wherein the hardcoat layer comprises silica nanoparticles have an average primary particle size of less than 25, 15, or 10 nm.
5 . The article of claim 1 wherein the first silane monomer(s) is present in at amount of at least 85, 90, or 95 wt. % based on the sum of first and second silane monomers.
6 . The article of claim 1 wherein the hardcoat layer comprises silica nanoparticles that comprise a hydrophilic silane surface treatment.
7 . The article of claim 6 wherein the hydrophilic silane surface treatment is an epoxy alkoxy silane.
8 . The article of claim 1 wherein the substrate comprises an organic polymeric material.
9 . The article of claim 1 wherein the surface layer is a rewritable surface.
10 . The article of claim 9 wherein the article is a dry erase board or film, label, file folder, file tab, or notebook cover or divider.
11 . A method of using an article having a rewritable surface comprising:
providing an article according to claim 1 ;
writing on the rewritable surface layer with a marker; and
removing the writing.
12 . The method of claim 11 wherein said hydrophilic silane comprises a zwitterionic silane.
13 . The method of claim 11 wherein the surface layer further comprises lithium silicate, sodium silicate, potassium silicate, or combinations thereof.
14 . The method of claim 11 wherein the hardcoat layer comprises silica nanoparticles have an average primary particle size of less than 25, 15, or 10 nm.
15 . The method of claim 11 wherein the first silane monomer(s) is present in at amount of at least 85, 90, or 95 wt. % based on the sum of first and second silane monomers.
16 . The method of claim 11 wherein the hardcoat layer comprises silica nanoparticles that comprise a hydrophilic silane surface treatment.
17 . The method of claim 16 wherein the hydrophilic silane surface treatment is an epoxy alkoxy silane.
18 . The method of claim 11 wherein the substrate comprises an organic polymeric material.
19 . The method of claim 11 wherein the surface layer is a rewritable surface.
20 . The method of claim 19 wherein the article is a dry erase board or film, label, file folder, file tab, or notebook cover or divider.
21 . The method of claim 11 wherein the marker is a permanent marker.
22 . The method of claim 11 wherein removing the writing comprises wiping the rewritable surface with a dry eraser, dry cloth or dry paper towel.