XDI-terminated polyurethane, and composition comprising said polyurethane

1. An XDI-terminated polyurethane based on methylene diphenyl diisocyanate or based on a mixture of meta-xylylene diisocyanate and methylene diphenyl diisocyanate, said polyurethane not being solid at a temperature ranging from 5° C. to 35° C., characterized in that the polyurethane is obtained using an XDI/(XDI+MDI) molar ratio ranging from 16% to 25% or strictly greater than 50%.

2. The polyurethane as claimed in claim 1 , capable of being obtained by a polyaddition reaction of at least one polyol composition with at least one polyisocyanate composition, under anhydrous conditions, in amounts of polyisocyanate(s) and of polyol(s) leading to an NCO/OH molar ratio ranging from 1.6 to 2.5.

3. The polyurethane as claimed in claim 2 , characterized in that the polyol composition is a mixture of polyether diol and of polyether triol.

4. The polyurethane as claimed in claim 1 , characterized in that it is based on methylene diphenyl diisocyanate and is meta-xylylene diisocyanate-terminated.

5. The polyurethane as claimed in claim 4 , capable of being obtained:

by a first polyaddition reaction of at least one polyol composition with at least one methylene diphenyl diisocyanate composition, under anhydrous conditions, in amounts of polyisocyanate(s) and of polyol(s) leading to an NCO/OH molar ratio strictly less than 1 in order to obtain an OH-terminated polyurethane,

followed by a second polyaddition reaction of the OH-terminated polyurethane with a meta-xylylene diisocyanate composition, under anhydrous conditions, in amounts of polyisocyanate(s) and of polyol(s) leading to an NCO/OH molar ratio ranging from 1.6 to 2.5.

6. The polyurethane as claimed in claim 1 , obtained using an XDI/(XDI+MDI) molar ratio ranging from 16% to 25% or 55% to 95%, preferably ranging from 16% to 25%.

7. A polyurethane composition comprising at least one polyurethane as claimed in claim 1 and at least some residual meta-xylylene diisocyanate monomers.

8. A process for preparing a polyurethane as claimed in claim 1 , said process comprising the mixing of a polyisocyanate composition comprising meta-xylylene diisocyanate and methylene diphenyl diisocyanate with a polyol composition.

9. The process as claimed in claim 8 , wherein the mixing is carried out in two steps, the first step comprising a polyaddition reaction of at least one polyol composition with at least one methylene diphenyl diisocyanate composition, under anhydrous conditions, in amounts of polyisocyanate(s) and of polyol(s) leading to an NCO/OH molar ratio strictly less than 1 in order to obtain an OH-terminated polyurethane and the second step comprising a polyaddition reaction of said OH-terminated polyurethane with a meta-xylylene diisocyanate composition, under anhydrous conditions, in amounts of polyisocyanate(s) and of polyol(s) leading to an NCO/OH molar ratio ranging from 1.6 to 2.5.

10. A composition comprising:

at least one polyurethane as claimed in claim 1 ,

at least one filler, and

at least one crosslinking catalyst.

11. The composition as claimed in claim 10 , comprising:

from 10% to 30% by weight of at least one polyurethane as claimed in claim 1 ,

from 25% to 70% by weight of at least one filler,

from 0.01% to 1% by weight of at least one crosslinking catalyst,

the percentages by weight being expressed relative to the total weight of said composition.

12. The composition as claimed in claim 10 , comprising less than 0.1% by weight of residual methylene diphenyl diisocyanate monomers and less than 0.5% by weight of residual meta-xylylene diisocyanate monomers, the percentages by weight being expressed relative to the total weight of said composition.

13. The composition as claimed in claim 10 , which is in anhydrous form.

14. An article comprising the composition as claimed in claim 10 in airtight hermetic packaging.

15. The article as claimed in claim 14 , wherein the hermetic packaging is an aluminum bag or an aluminum cartridge.