High index and high impact resistant polythiourethane/urea material, method of manufacturing same and its use in the optical field

1. A transparent, non-elastomeric, polythiourethane/urea material comprising the reaction product of:

(a) at least one (α, ω)-diiso(thio)cyanate polysulfide prepolymer, said prepolymer being free from disulfide (—S—S—) linkage; and

(b) at least one aromatic primary diamine, in an equivalent molar ratio amine function/iso(thio)cyanate function (NH 2 /NCX, X═O, S) ranging from 0.5 to 2, said aromatic primary diamine being free from disulfide (—S—S—) linkage,

wherein the (α, ω)-diiso(thio)cyanate polysulfide prepolymer is the reaction product of at least one cycloaliphatic or aromatic (α, ω) -diiso(thio)cyanate and at least one (α, ω)-dithiol prepolymer, said (α, ω)-dithiol prepolymer being a polysulfide or a mixture of polysulfides.

2. The material of claim 1 , wherein the equivalent ratio NH 2 /NCX ranges from 0.90 to 1.10.

3. The material of claim 1 , wherein the equivalent ratio NH 2 /NCX ranges from 0.93 to 0.95.

4. The material of claim 1 , wherein the polysulfide or mixture of polysulfides is a polysulfide of formula:

in which x and y are chosen such that the two following conditions are simultaneously satisfied:

the polysulfide of formula Ia is a prepolymer; and

the number average molecular weight of the polysulfide of formula Ia is not more than 3000 g mol −1 .

5. The material of claim 1 , wherein the aromatic diamine contains at least one S atom in its molecule.

6. The material of claim 5 wherein the diamine is selected from

in which R is H or an alkyl group and R′ is an alkyl group, and mixtures of the above diamines.

7. The material of claim 6 , wherein R and R′ are CH 3 .

8. The material of claim 6 , wherein the diamine is a mixture of by weight:

9. The material of claim 1 , wherein the material is the reaction product of:

a) said at least one (α, ω)-diiso(thio)cyanate polysulfide prepolymer;

b) said at least one aromatic primary diamine; and

c) at least one di-, tri-, or tetra alcohol, or at least one di-, tri-, or tetra thiol, or a mixture thereof.

10. The material of claim 9 , wherein the alcohols and thiols are selected from the group consisting of:

and mixtures thereof.

11. The material of claim 1 , wherein the polysulfide is an hyperbranched polysulfide resulting from the polymerization of a diepisulfide of formula:

in which R 1 and R 2 are, independently from each other, H, alkyl, aryl, alkoxy, alkylthio or arylthio, R 3 and R 4 are independently from each other,

Ra designates H, alkyl, aryl, alkoxy, aryloxy, alkylthio or arylthio, with 2-mercaptoethyl sulfide (DMES).

12. The material of claim 11 , wherein the diepisulfide has formula:

13. The material of claim 1 , wherein the polysulfide or mixture of polysulfides is a prepolymer of the formula:

where n′ is such that the number average molecular weight ( M n ) of the prepolymer ranges from 500 to 1500g mol −1 .

14. The material of claim 13 , wherein n′ is such that the number average molecular weight ( M n ) of the prepolymer ranges from 650 to 1350 g mol −1 .

15. The material of claim 1 , wherein the polysulfide or mixture of polysulfides is a prepolymer resulting from the polymerization of diepisulfides of formula:

in which R 1 and R 2 are, independently from each other, H, alkyl, aryl, alkoxy, alkylthio or arylthio; R 3 and R 4 are, independently from each other,

R a designates H, alkyl, aryl, alkoxy, aryloxy, alkylthio or arylthio and, n is an integer from 0 to 4 and m is an integer from 1 to 6.

16. The material of claim 1 , wherein the at least one (α, ω) -diiso(thio)cyanate polysulfide prepolymer has a number average molecular weight of not more than 3000 g mol −1 .

17. The material of claim 1 having a refractive index,

n

D

25

,

higher 1.53.

18. The material of claim 1 having a refractive index,

n

D

25

,

of at least 1.55.

19. The material of claim 1 having a refractive index,

n

D

25

,

of at least 1.57.

20. An optical article made from a material according to claim 1 .