Adhesive dual-component composition based on polyurethane

1. A two-component polyurethane-based adhesive composition comprising an —NCO component and an —OH component, wherein:

the —NCO component is a composition comprising:

A) at least one polyurethane prepolymer comprising at least two NCO end groups, said at least one polyurethane prepolymer obtained by a polyaddition reaction comprising reacting

at least one asymmetric diisocyanate monomer and

at least one diol, wherein the diol has a hydroxyl number (OHN) of 112 to 280 mg KOH/g, wherein the polyaddition reaction takes place in amounts of diisocyanate monomer(s) and of diol(s) resulting in an NCO/OH molar ratio, denoted r 1 , ranging from 1.5 to 2.2, and

B) at least one triisocyanate selected from the group consisting of isocyanurates, biurets, adducts of diisocyanates and of triols, and their mixtures; and

the —OH component is a composition comprising at least one polyol,

wherein for the two-component polyurethane-based adhesive composition, at least one of the at least one polyol of the —OH component or the at least one diol used for obtaining the —NCO component comprises a polyether polyol or a polyether diol, at least one of the at least one polyol of the —OH component or the at least one diol used for obtaining the —NCO component comprises a polyester polyol or a polyester diol, and

a ratio by weight of an amount of polyether polyol(s) to an amount of polyester polyol(s), denoted r 4 , ranges from 0.6 to 2.2, wherein for the determination of the ratio r 4 , an amount of a polyester diol is included in the amount of polyester polyol and an amount of a polyether diol is included in the amount of polyether polyol,

wherein the adhesive is constituted such that when it is used to form an adhesive layer bonding a thermoplastic film and a metal sheet, the level of cohesion of the adhesive layer is greater than or equal to 3 N/15 mm, wherein the level of cohesion is tested by the 180° peel test French standard NF T 54-122.

2. The composition as claimed in claim 1 , wherein the asymmetric diisocyanate monomer is selected from the group consisting of:

isophorone diisocyanate (IPDI),

2,4-toluene diisocyanate (2,4-TDI) and its hydrogenated form,

2,4′-diphenylmethane diisocyanate (2,4′-MDI) and its hydrogenated form,

and their mixtures.

3. The composition as claimed in claim 1 , wherein the at least one diol used for obtaining the —NCO component is selected from the group consisting of polyether diol(s), polyester diol(s) and their mixtures.

4. The composition as claimed in claim 3 , wherein the at least one diol used for obtaining the —NCO component comprises a mixture of polyether diol(s) and polyester diol(s).

5. The composition as claimed in claim 1 , wherein the at least one polyol of the —OH composition is selected from the group consisting of polyether polyols, polyester polyols, and polyurethane prepolymers comprising at least two OH groups and their mixtures.

6. The composition as claimed in claim 5 , wherein the at least one polyol of the —OH composition is selected from the group consisting of polyether diols, polyester diols, polyether triols, polyalkylene triols, polyester triols, and their mixtures.

7. The composition as claimed in claim 1 , wherein the polyaddition reaction takes place in the presence or absence of at least one reaction catalyst, at a reaction temperature T1 of less than 95° C., under anhydrous conditions.

8. The composition as claimed in claim 1 , wherein the triisocyanate comprises a diisocyanate isocyanurate of general formula (I):

wherein:

R represents a linear, branched or cyclic and aliphatic or aromatic alkylene group comprising from 4 to 9 carbon atoms,

with the proviso that the NCO groups are not connected via a covalent bond to a carbon atom forming part of an aromatic hydrocarbon ring.

9. The composition as claimed in claim 1 , wherein the —NCO component comprises a content of aliphatic diisocyanate monomer(s) of less than or equal to 0.5% by weight, with respect to the weight of the —NCO component, and a content of aromatic diisocyanate monomer(s) of less than or equal to 0.1% by weight, with respect to the weight of the —NCO component.

10. The composition as claimed in claim 1 , wherein the —NCO and —OH components are in amounts such that an NCO/OH molar ratio, denoted r 3 , ranges from 1 to 2.5.

11. The composition as claimed in claim 1 , wherein a molar ratio of a number of NCO groups present in a total amount of diisocyanate monomer(s) used for synthesis of the polyurethane prepolymer having NCO endings A) to the number of NCO groups present in the total amount of triisocyanate(s) B) present in the —NCO component, denoted r 2 , ranges from 3 to 8.5.

12. The composition as claimed in claim 11 , wherein the r 2 ratio ranges from 3 to 5.

13. The composition as claimed in claim 1 , wherein the content of NCO groups of the —NCO component ranges from 220 to 280 meq NCO per 100 g of the —NCO component.

14. The composition as claimed in claim 1 , wherein the composition does not comprise solvent.

15. A multilayer structure comprising at least two layers of material bonded together by an adhesive layer, wherein said adhesive layer comprises the adhesive composition of claim 1 , said composition obtained by mixing the —NCO and —OH components in a crosslinked state.

16. A process for the continuous manufacture of a multilayer structure as claimed in claim 15 , comprising the following stages:

(i) mixing the —NCO and —OH components at a temperature of less than or equal to 60° C. to form a mixture, then

(ii) coating said mixture over a surface of a first layer of material to form a coated surface, then

(iii) laminating a surface of a second layer of material over said coated surface, then

(iv) crosslinking said mixture.

17. A two-component polyurethane-based adhesive composition comprising an —NCO component and an —OH component, wherein:

the —NCO component is a composition comprising:

A) at least one polyurethane prepolymer comprising at least two NCO end groups, said at least one polyurethane prepolymer obtained by a polyaddition reaction comprising reacting

at least one asymmetric diisocyanate monomer and

at least one diol, wherein the diol has a hydroxyl number (OHN) of 112 to 280 mg KOH/g, wherein the polyaddition reaction takes place in amounts of diisocyanate monomer(s) and of diol(s) resulting in an NCO/OH molar ratio, denoted r 1 , ranging from 1.5 to 2.2, and

B) at least one triisocyanate selected from the group consisting of isocyanurates, biurets, adducts of diisocyanates and of triols, and their mixtures; and

the —OH component is a composition comprising at least one polyol,

wherein for the two-component polyurethane-based adhesive composition, at least one of the at least one polyol of the —OH component or the at least one diol used for obtaining the —NCO component comprises a polyether polyol or a polyether diol, at least one of the at least one polyol of the —OH component or the at least one diol used for obtaining the —NCO component comprises a polyester polyol or a polyester diol, and

a ratio by weight of an amount of polyether polyol(s) to an amount of polyester polyol(s), denoted r 4 , ranges from 0.6 to 2.2, wherein for the determination of the ratio r 4 , an amount of a polyester diol is included in the amount of polyester polyol and an amount of a polyether diol is included in the amount of polyether polyol,

wherein the adhesive is constituted such that when it is used to form an adhesive layer bonding a thermoplastic film and a metallized thermoplastic film, the level of cohesion of the adhesive layer is greater than or equal to 1 N/15 mm, wherein the level of cohesion is tested by the 180° peel test French standard NF T 54-122.