UV-curable film compositions with improved scratch resistance
View Patent ↗Thin walled products having good scratch resistance are disclosed, as are processes for making such products (e.g. films, sheets, and thin walled articles). The product includes a thin layer formed from (A) a cross-linkable polycarbonate resin having endcaps derived from a monohydroxybenzophenone; and (B) if desired, a base polymeric resin. When exposed to ultraviolet light, crosslinking will occur in the layer with the cross-linkable polycarbonate resin, enhancing the scratch resistance properties of the thin layer and the overall product.
1. A thin walled product comprising:
a crosslinked layer formed from a photoactive additive that has been exposed to ultraviolet light, the photoactive additive containing photoactive endcap groups derived from monohydroxybenzophenone and endcap groups derived from a non-photoactive end-capping agent;
wherein the photoactive additive is a homopolycarbonate formed from the reaction of:
the monohydroxybenzophenone;
a diol chain extender which is bisphenol A;
a first linker moiety which is phosgene; and
the non-photoactive end-capping agent; and
wherein the photoactive additive has a monohydroxybenzophenone-derived endcap content from 3.0 to 5.0 mol %; and
wherein the photoactive additive does not contain any aliphatic polyester, aliphatic polyether, aliphatic polythioether, aliphatic polyacetal, aliphatic polycarbonate, C-C linked polymer, and polysiloxane segments.
2. The thin walled product of claim 1 , wherein the thin walled product has a scratch rating of B or harder according to ASTM D3363.
3. The thin walled product of claim 2 , further comprising a substrate layer formed from a substrate resin and bonded to the crosslinked layer.
4. The thin walled product of claim 1 , wherein the monohydroxybenzophenone is 4-hydroxybenzophenone.
5. The thin walled product of claim 4 , wherein the photoactive additive has a weight average molecular weight of 15,000 or greater, measured prior to crosslinking.
6. The thin walled product of claim 1 , wherein the non-photoactive end-capping agent is selected from the group consisting of phenol, p-t-butylphenol, p-cumylphenol, octylphenol, and p-cyanophenol.
7. The thin walled product of claim 1 , wherein the reaction that forms the photoactive additive further comprises a secondary linker moiety having at least three functional groups, each of which can react with a linking group of the first linker moiety.
8. A process for making the thin walled product of claim 1 , comprising:
extruding a film layer comprising the photoactive additive; and
exposing the film layer to ultraviolet light to induce crosslinking in the film layer and obtain the thin walled product.
9. The process of claim 8 , wherein the film layer is co-extruded with a substrate resin that forms a substrate layer bonded to the film layer.
10. The process of claim 8 , wherein the thin walled layer has a scratch rating of B or harder according to ASTM D3363.
11. The process of claim 8 , wherein the film layer further comprises a polymeric base resin.
12. A thin walled product comprising:
a crosslinked layer formed from a photoactive additive that has been exposed to ultraviolet light, the photoactive additive containing photoactive endcap groups derived from monohydroxybenzophenone;
and
wherein the photoactive additive has a monohydroxybenzophenone-derived endcap content from 3.0 to 5.0 mol %; and
the photoactive additive has a structure of Formula (II):
wherein n′ ranges from 29 to 65, and
wherein the thin walled product further comprises a substrate layer formed from a substrate resin and bonded to the crosslinked layer, and the thin walled product has a scratch rating of B or harder according to ASTM D3363.
13. The thin walled product of claim 12 , wherein the crosslinked layer is from about 2% to about 40% of the thickness of the thin walled product.
14. The thin walled product of claim 12 , wherein the crosslinked layer has a thickness of about 2.5 micrometers to about 12.7 millimeters.
15. The thin walled product of claim 12 , wherein the substrate resin is a polycarbonate film.
16. The thin walled product of claim 12 , wherein the photoactive additive has a weight-average molecular weight of between 17,000 and 80,000 Daltons, as measured by gel permeation chromatography using a UV-VIS detector and polycarbonate standards.
17. The thin walled product of claim 12 , wherein the crosslinked layer further comprises a polymeric base resin which is different from the photoactive addictive.
18. The thin walled product of claim 12 , wherein the crosslinked layer further comprises a flame retardant.