Composition of photopolymerizable resins and method to produce an article using this composition

1 . A composition of photopolymerizable resins consisting of:

(A) derivatives of diurethane dimethacrylates having the following formula:

wherein R and R′ are the same or different, and are selected from H and methyl, and/or its oligomers with a molecular weight up to 6000 g/mol;

(B) one or more of the following (meth)acrylic monomers:

(C) one or more radical polymerization photoinitiators for said monomers and/or oligomers; and

(D) one or more additives chosen from the group consisting of organic and inorganic dyes and UV absorbers for the control of the printing resolution with high absorbance at the typical wavelengths of the radiant sources.

2 . The composition of claim 1 , wherein said monomers and/or oligomers have a viscosity at room temperature between 100 and 1000 mPa·s.

3 . The composition of claim 1 , wherein said component (A) is present in an amount from 60 to 90% by mass.

4 . The composition of claim 1 , wherein said component (B) is present in an amount from 10 to 40% by mass.

5 . The composition of claim 1 , wherein said component (C) is present in an amount from 0.5 to 3% by mass.

6 . The composition of claim 1 , wherein said component (D) is present in an amount from 0.005 to 0.05% by mass.

7 . A method to form a three-dimensional article, the method comprising:

(1) depositing on a surface a first thin layer of the composition of photopolymerizable resins according to claim 1 ;

(2) exposing said thin layer to a photopolymerizing radiation of sufficient intensity to cause the resins of said thin layer to polymerize;

(3) depositing a second thin layer of said composition of photopolymerizable resins on said first thin layer previously exposed to said photopolymerizing radiation;

(4) exposing said second thin layer to said photopolymerizing radiation of sufficient intensity to cause the resins of said second thin layer to polymerize and to cause adhesion to said first thin layer;

(5) repeating steps (3) and (4) a sufficient number of times to manufacture said article; and

(6) subjecting the article obtained to a post-curing treatment comprising irradiation with a radiation of a wavelength between 300 and 450 nm, at a temperature between 5° and 100° C. and for a time between 30 and 90 minutes.

8 . The method of claim 7 , wherein:

in said step (1) said composition of photopolymerizable resins is poured into a printing tank with a transparent bottom, creating said first thin layer on the bottom of said tank;

in said step (2) a growth platform is lowered to the bottom of said tank and said first layer is irradiated by a suitable source positioned underneath the tank, in order to solidify said resins;

in said step (3) said growth platform, on which the solidified part of said photopolymerizable resins remains attached, is lifted and another part of photopolymerizable resin is poured on the bottom of said tank with the formation of a second thin layer of liquid resin on the transparent bottom of said tank;

in said step (4) said growth platform is lowered to the bottom of said tank and said second layer is irradiated by said source positioned underneath the tank, in order to solidify said second layer of resins on said first layer of resins;

in said step (5) the process is repeated for a sufficient number of layers to produce said three-dimensional article; and

in said step (6) said article undergoes said post-curing treatment.

9 . An HTM resin article obtained by photopolymerization of said composition of photopolymerizable resins according to claim 1 , said article having a Shore D hardness between 50 and 90 measured according to ISO 868.