Low-viscosity liquid radiation curable dental aligner mold resin compositions for additive manufacturing

1. A liquid radiation curable resin composition comprising, relative to the total weight of the composition:

(a) from about 50 to about 80 wt % of an epoxy component comprising at least two different epoxy-containing compounds, said epoxy component further comprising:

a cycloaliphatic epoxy-containing compound, and

an epoxy compound having an aromatic glycidyl ether group;

(b) from about 5 to about 30 wt % of an oxetane component;

(c) a (meth)acrylate component;

(d) a cationic photoinitiator; and

(e) a free-radical photoinitiator;

wherein at least 25 wt % of the epoxy component is the cycloaliphatic epoxy-containing compound;

wherein the resin liquid radiation curable resin composition has a viscosity of between about 75 and about 300 cps at 30 degrees Celsius; and

wherein the oxetane component consists essentially of mono-functional oxetane compounds.

2. The liquid radiation curable resin composition of claim 1 , wherein at least 50 wt. % of the epoxy component is the cycloaliphatic epoxy-containing compound.

3. The liquid radiation curable resin composition of claim 1 , wherein the resin composition has a viscosity of between about 75 and about 200 cps at 30 degrees Celsius, and wherein the resin composition after cure, 60 min UV postcure, and heat treatment at 100 degrees Celsius for 6 hours, has a Glass Transition temperature (Tg) of greater than 90 degrees Celsius.

4. The liquid radiation curable resin composition of claim 1 , wherein the weight ratio of the cycloaliphatic epoxy-containing compound to the epoxy compound having an aromatic glicidyl ether group is from 3:2 to 5:2.

5. The liquid radiation curable resin composition of claim 4 , wherein the cycloaliphatic epoxy-containing compound is selected from the group consisting of: 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)-cyclohexane-1,4-dioxane, bis(3,4-epoxycyclohexylmethyl)adipate, vinylcyclohexene oxide, 4-vinylepoxycyclohexane, vinylcyclohexene dioxide, bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, 3,4-epoxy-6-methylcyclohexyl-3′,4′-epoxy-6′-methylcyclohexanecarboxylate, ε-caprolactone-modified 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylates, trimethylcaprolactone-modified 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexane carboxylates, β-methyl-δ-valerolactone-modified 3,4-epoxycyclohexcylmethyl-3′,4′-epoxycyclohexane carboxylates, methylenebis(3,4-epoxycyclohexane), bicyclohexyl-3,3′-epoxide, bis(3,4-epoxycyclohexyl) with a linkage of —O—, —S—, —SO—, —SO 2 —, —C(CH 3 ) 2 —, —CBr 2 —, —C(CBr 3 ) 2 —, —C(CF 3 ) 2 —, —C(CCl 3 ) 2 —, or —CH(C 6 H 5 )—, dicyclopentadiene diepoxide, di(3,4-epoxycyclohexylmethyl) ether of ethylene glycol, ethylenebis(3,4-epoxycyclohexanecarboxylate), and epoxyhexahydrodioctylphthalate.

6. The liquid radiation curable resin composition of claim 5 , wherein component (a) is present in an amount from about 60 to about 75 wt %.

7. The liquid radiation curable resin composition of claim 1 , wherein the cationic photoinitiator is present in an amount from about 2 to about 10 wt %.

8. The liquid radiation curable resin composition of claim 1 , wherein the free-radical photoinitiator is present in amount from about 2 to about 10 wt %.

9. The liquid radiation curable resin composition of claim 1 , wherein the (meth)acrylate component is present in an amount from about 2 to about 25 wt %.

10. The liquid radiation curable resin composition of claim 1 , wherein the epoxy compound having an aromatic glycidyl ether group is present in the liquid radiation curable resin composition in an amount from about 5 to about 25 wt %.

11. The liquid radiation curable resin composition of claim 1 , wherein the oxetane component is defined by the following formula:

wherein R 1 is a C 1 -C 4 alkyl group, Z is Oxygen, and R 2 is selected from the group consisting of H, a C 1 -C 8 alkyl group or a phenylgroup.

12. The liquid radiation curable resin composition of claim 10 , wherein the amount of the oxetane component (b) is from about 15 to about 20 wt %.

13. The liquid radiation curable resin composition of claim 1 , wherein at least 75% of the resin composition by weight is a cationically curable component, and the epoxy compound having an aromatic glydicyl ether group is at least difunctional.

14. The liquid radiation curable resin composition of claim 13 , wherein the (meth)acrylate component is a polyfunctional (meth)acrylate containing more than four functional groups.

15. The liquid radiation curable resin composition of claim 14 , wherein the ratio of the cycloaliphatic epoxy-containing compound to the epoxy compound having an aromatic glycidyl ether group to the oxetane is from 1.5:1:1 to 5:2:1.

16. The liquid radiation curable resin composition of claim 15 , wherein the resin composition is substantially free of a polyol.

17. The liquid radiation curable resin composition of claim 16 , wherein the resin composition is substantially free of a stabilizer.

18. A process for fabricating a dental aligner mold, comprising:

(1) placing a first liquid layer of a liquid radiation curable resin composition, thereby forming a surface, wherein the liquid radiation curable resin composition is as defined in claim 3 ;

(2) exposing the first liquid layer imagewise to actinic radiation to form an imaged cross-section, wherein the radiation is of sufficient intensity to cause substantial curing of the first liquid layer in the exposed areas, thereby forming a first cured layer;

(3) lowering the first cured layer in a direction substantially orthogonal to, and away from, the surface, thereby allowing a new layer of liquid radiation curable resin composition to freely flow over the first cured layer without a recoating operation;

(4) exposing said new layer from step (3) imagewise to actinic radiation to form an additional imaged cross-section, wherein the radiation is of sufficient intensity to cause substantial curing of the new layer in the exposed areas and to cause adhesion to the first cured layer; and

(5) repeating steps (3) and (4) a sufficient number of times in order to build up a dental aligner mold.

19. The process of claim 18 , further comprising:

(6) vacuum forming a thermoplastic sheet over the dental aligner mold to form a dental aligner.

20. The dental aligner mold created by the process of claim 18 .