Low-viscosity polyurethane prepolymer with cyclic carbonate end groups and the use thereof in the production of a multi-component adhesive composition

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

• in a first stage (denoted E1), the preparation of a polyurethane prepolymer having NCO end groups (PP1) by a polyaddition reaction:
• (i) of at least one diisocyanate of the following aliphatic or aromatic diisocyanates, or their mixtures:
• a1) isophorone diisocyanate (IPDI),
• a2) 2,4-toluene diisocyanate (2,4-TDI), or
• a3) 2,4′-diphenylmethane diisocyanate (2,4′-MDI),
• (ii) with at least one polyol of polyether polyols and polydiene polyols, at a reaction temperature T1 of less than 95° C., under anhydrous conditions and in amounts of diisocyanate(s) and of polyol(s) resulting in an NCO/OH molar ratio, denoted r1, ranging from 1.6 to 1.9;
• then
• in a second stage (denoted E2), the reaction, under anhydrous conditions, at a reaction temperature T2 of less than 95° C., of the product formed in the first stage E1 with at least one glycerol carbonate in an amount of glycerol carbonate resulting in an NCO/OH molar ratio, denoted r2, ranging from 0.9 to 1.0,
• the 2,4-toluene diisocyanate (2,4-TDI) optionally being used in the form of a TDI mixture a2) comprising at least 99% by weight of 2,4-toluene diisocyanate (2,4-TDI), with respect to the total weight of said mixture a2), and
• the 2,4′-diphenylmethane diisocyanate (2,4′ MDI) optionally being used in the form of an MDI mixture a3) comprising at least 99% by weight of 2,4′-diphenylmethane diisocyanate (2,4′-MDI), with respect to the total weight of said mixture a3).