Low-viscosity polyurethane prepolymer with cyclic carbonate end groups and the use thereof in the production of a multi-component adhesive composition
1) Specific polyurethane prepolymer (PP2) comprising at least two terminal (2-oxo-1,3-dioxolan-4-yl)methyl carbamate groups of low viscosity, its preparation process and its use in the manufacture of an adhesive composition. 2) Multicomponent system comprising, as first component (A), a composition comprising at least one such polyurethane prepolymer and, as second component (B), a composition comprising at least one curing agent comprising at least two primary amine (—NH 2 ) groups (B1). 3) Process for assembling materials employing the polyurethane prepolymer (PP2) according to the invention.
1. 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).
2. The preparation process as claimed in claim 1 , wherein the ratio r1 ranges from 1.65 to 1.85.
3. The preparation process as claimed in claim 1 , that does not comprise adding one or more solvent(s) and/or plasticizer(s).
4. The preparation process as claimed in claim 1 , wherein the polyether polyols are polyoxyalkylene polyols, having a linear or branched alkylene part of from 1 to 4 carbon atoms, or polybutadienes comprising terminal hydroxyl groups which are optionally hydrogenated or epoxidized.
5. The preparation process as claimed in claim 1 , wherein the polyether polyols polyoxypropylene diols or triols with a polydispersity index ranging from 1 to 1.4.
6. The preparation process as claimed in claim 1 , wherein the polyol(s) is (are) those having a number-average molar mass ranging from 200 to 20 000 g/mol.
7. The preparation process as claimed in claim 1 , wherein the diisocyanate is 2,4-TDI or a TDI mixture.
8. 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 .
9. A multicomponent system, comprising:
a 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 8 , and
a second component (denoted component (B)), a composition comprising at least one curing agent having at least two primary amine (—NH 2 ) groups (B1).
10. The multicomponent system as claimed in claim 9 , wherein said curing agent(s) (B1) have a primary alkalinity ranging from 0.4 to 34 meq/g of curing agent.
11. The multicomponent system as claimed in claim 9 , wherein the primary amine groups of said curing agent(s) (B1) are methylene(primary amine) (—CH 2 —NH 2 ) groups.
12. The multicomponent system as claimed in claim 9 , having amounts of polyurethane prepolymer(s) having (2-oxo-1,3-dioxolan-4-yl)methyl carbamate end groups (PP2) and of curing agent(s) (B1) having a primary alkalinity of 0.4 to 34 meq/g of curing agent present in the multicomponent system resulting 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.
13. The multicomponent system as claimed in claim 9 , further comprising at least one inorganic filler.
14. 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 8 , comprising the following:
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) having a primary alkalinity ranging from 0.4 to 34 meq/g of curing agent, 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.
15. The process according to claim 14 wherein the primary amine groups of said curing agent(s) (B1) are methylene(primary amine) (—CH 2 —NH 2 ) groups.
16. In an adhesive composition comprising conventional adhesive components and a polyurethane prepolymer, the improvement wherein the composition comprises a polyurethane prepolymer of claim 8 .