Synthesis of biurets and isocyanates with alkoxysilane functions, formulations containing same and use thereof
The invention relates to a composition and a method of preparing one such composition and an isocyanatoalkoxysilane; the polyisocyanate composition contains at least two different oligomeric compounds comprising at least three units and at most five units selected from aminoalkylsilane units and diamine units and at least one function selected from isocyanate functions and from those derived therefrom, the aforementioned compounds having at least two aminoalkylsilane units and another compound having at least two diamine units; the invention is suitable for coatings.
1. A polyisocyanate composition comprising at least two different oligomeric compounds A and B, where A comprises at least two aminoalkylsilane units and compound B comprises at least two diamino units, in which said oligomeric compounds each comprises (I) at least three and at most five units selected from the group consisting of aminoalkylsilane and diamine functional groups and (II) at least one functional group selected from the group consisting of isocyanate functional groups and derivatives of isocyanate functional groups, wherein said derivative is a carbamate, uretidinedione, isocyanurate, biuret, allophanate, 4,6-dioxo-2-iminohexahydro-1,3,5-triazine, iminooxadiazinedione or 2-imino-4-oxo-1,3-diazetidine functional group,
wherein the aminoalkylsilane unit is derived from a compound of formula I:
wherein:
m and n individually are 0, 1, 2 or 3 with proviso that m+n=3;
R 1 is a linear or branched hydrocarbon chain of 2 to 20 carbon atoms, said hydrocarbon chain being aliphatic, aromatic or aralkyl, optionally interrupted by heteroatoms;
R 2 is a linear or branched hydrocarbon chain of 1 to 20 carbon atoms;
R 3 is a linear or branched hydrocarbon chain of 1 to 20 carbon atoms; and
X═O or S,
said composition having a viscosity of at most 6000 mPa·s and an amount of isocyanate monomer being at most 2% by weight of the composition.
2. A composition according to claim 1 , wherein the ratio in equivalents of the aminoalkylsilane units to the diamino units is at least equal to 15%.
3. A composition according to claim 1 , wherein each oligomeric compound is present in an amount of at least 3% by weight of said composition.
4. A composition according to claim 1 , wherein each oligomeric compound is present in an amount of less than ⅔ by weight of said composition.
5. A composition according to claim 1 , wherein the compounds A and B comprise a biuret functional group.
6. A composition according to claim 5 , wherein the biuret functional groups are present in an amount of at least 5% by weight of the composition.
7. A composition according to claim 6 , wherein the biuret functional groups are present in an amount of less than or equal to 20% by weight of the composition.
8. A composition according to claim 1 , wherein the blocked and free isocyanate functional groups are present in an amount of at least 5% by weight of the composition.
9. A composition according to claim 1 , wherein said composition has a viscosity of at most 4000 mPa·s.
10. A composition according to claim 1 , wherein the amount of isocyanate monomer is at most 1% by weight of the composition.
11. A composition according to claim 1 , wherein the content of isocyanatoalkylsilane formed by reacting at least one isocyanate monomer with an aminoalkylsilane is at most 2% by weight of the composition.
12. A composition according to claim 1 , wherein said composition has a viscosity of at most 3000 mPa·s.