Polyurethane prepolymer with cyclocarbonate end groups of low viscosity and the use thereof in the production of a multi-component adhesive composition

1. A process for the preparation of a polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) comprising a stage of polyaddition reaction (denoted E2):

of at least one compound (PP1) having at least two NCO groups and at least one divalent unit of formula (I′):

in which:

p is an integer ranging from 1 to 2;

q is an integer ranging from 0 to 9;

R represents a saturated or unsaturated, linear or branched, cyclic or acyclic, hydrocarbon chain of 1 to 20 carbon atoms;

R 3 represents a saturated, linear or branched, divalent hydrocarbon group of 2 to 4 carbon atoms;

with at least one glycerol carbonate, at a reaction temperature T2 of less than 95° C., under anhydrous conditions, in amounts of compound (PP1) and of glycerol carbonate resulting in an NCO/OH molar ratio, denoted r2, ranging from 0.8 to 1.0.

2. The preparation process as claimed in claim 1 , wherein the compound(s) (PP1) is (are) hexamethylene diisocyanate (HDI) allophanate compounds of formula (I):

in which:

p is an integer ranging from 1 to 2;

q is an integer ranging from 0 to 9;

R represents a saturated or unsaturated, linear or branched, cyclic or acyclic, hydrocarbon chain of 1 to 20 carbon atoms;

R 3 represents a saturated, linear or branched, divalent hydrocarbon group having from 2 to 4 carbon atoms.

3. The preparation process as claimed in claim 1 , wherein the compound(s) (PP1) is (are) polyurethane prepolymers having NCO end groups capable of being obtained by a polyaddition reaction:

(i) of a diisocyanate composition comprising at least one hexamethylene diisocyanate (HDI) allophanate compound of formula (I),

in which:

p is an integer ranging from 1 to 2;

q is an integer ranging from 0 to 9;

R represents a saturated or unsaturated, linear or branched, cyclic or acyclic, hydrocarbon chain of 1 to 20 carbon atoms;

R 3 represents a saturated, linear or branched, divalent hydrocarbon group having from 2 to 4 carbon atoms

(ii) with at least one polyether polyol, at a reaction temperature T1 of less than 95° C., under anhydrous conditions and in amounts of diisocyanate(s) and of polyether polyol(s) resulting in an NCO/OH molar ratio, denoted r1, ranging from 1.6 to 1.9.

4. The preparation process as claimed in claim 3 , wherein the polyether polyol(s) is (are) polyoxyalkylene polyols, a linear or branched alkylene part of which has 1 to 4 carbon atoms and the average molar mass of which ranges from 200 to 20 000 g/mol.

5. The preparation process as claimed in claim 1 , that does not comprise adding one or more solvent(s) and/or plasticizer(s).

6. A polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2), capable of being obtained by the preparation process as defined in claim 1 .

7. A multicomponent system, comprising:

as first component (denoted component (A)), a composition comprising at least one polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2), as defined in claim 6 , and

as second component (denoted component (B)), a composition comprising at least one curing agent having at least two primary amine (—NH 2 ) groups (B1).

8. The multicomponent system as claimed in claim 7 , wherein the primary amine groups of said curing agent(s) (B1) are methylene(primary amine) (—CH 2 —NH 2 ) groups.

9. The multicomponent system as claimed in claim 7 , wherein the amounts of polyurethane prepolymer(s) having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) and of curing agent(s) having at least two primary amine groups (B1) as defined in claim 7 present in the multicomponent system result in a molar ratio of the number of cyclocarbonate groups to the number of primary amine groups, denoted r3, ranging from 0.5 to 1.

10. The multicomponent system as claimed in claim 7 , comprising at least one inorganic filler.

11. A process for assembling materials employing the polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) as defined in claim 6 , comprising:

mixing of at least one polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) and of at least one curing agent having at least two primary amine (—NH 2 ) groups (B1), then

coating of said mixture onto the surface of a first material, then

laminating of the surface of a second material onto said coated surface, then

crosslinking of said mixture.

12. In an adhesive composition comprising a polyurethane polymer, the improvement wherein the polymer is produced from a polyurethane prepolymer having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) as defined in claim 6 .