Polyester Prepolymers
The invention relates to prepolymers containing alkoxysilane groups based on special, low-viscosity polyester polyols, which exhibit particularly high tensile strength, a process for the production thereof and their use as a binder for adhesives, primers or coatings.
1 . Alkoxysilane group-containing polyurethanes of the general formula (I),
in which
PIC is a residue of a diisocyanate reduced by the isocyanate groups,
PES is a residue of a polyester polyol with 2-3 OH groups, reduced by the OH groups, at least 90 wt. % of which (based on acid and alcohols) was produced from adipic acid and a mixture of at least 20 wt. % each (based on the mixture) of butanediol or hexanediol and neopentyl glycol, having a number-average molecular weight (Mn) of between 500 g/mol and 2500 g/mol,
a=0 or 1,
b=0 to 5,
c=1 or 2,
X represents the same or different alkoxy or alkyl residues, which may also be bridged, provided that at least one alkoxy residue is present on each Si atom,
Q is a difunctional, linear or branched, aliphatic residue,
R denotes either hydrogen or any organic residue which can be bridged with R1 (if present), R always denoting hydrogen when a=0, and
R1 denotes either hydrogen or an organic residue which is bridged with R.
2 . Alkoxysilane group-containing polyurethanes according to claim 1 , wherein a=0.
3 . Alkoxysilane group-containing polyurethanes according to claim 1 , wherein a=1.
4 . Alkoxysilane group-containing polyurethanes according to claim 3 , wherein R and R1 are bridged as a hydantoin ring.
5 . Alkoxysilane group-containing polyurethanes according to claim 1 , wherein b=0.
6 . Alkoxysilane group-containing polyurethanes according to claim 2 , wherein b=0.
7 . Alkoxysilane group-containing polyurethanes according to claim 3 , wherein b=0.
8 . Alkoxysilane group-containing polyurethanes according to claim 4 , wherein b=0.
9 . A process for the production of polyurethanes modified with alkoxysilane groups, comprising either
A) a polyester polyol with 2-3 OH groups, at least 90 wt. % of which (based on acid and alcohols) was produced from adipic acid and a mixture of at least 20 wt. % each (based on the mixture) of butanediol or hexanediol and neopentyl glycol, having a number-average molecular weight (Mn) of between 500 g/mol and 2500 g/mol, is first reacted with an excess of diisocyanate to form an isocyanate-functional polyurethane prepolymer, which is then capped with an aminosilane, or
B) a polyester polyol with 2-3 OH groups, at least 90 wt. % of which (based on acid and alcohols) was produced from adipic acid and a mixture of at least 20 wt. % each (based on the mixture) of butanediol or hexanediol and neopentyl glycol, having a number-average molecular weight (Mn) of between 500 g/mol and 2500 g/mol, is optionally first reacted with a deficiency of diisocyanate to form an OH-functional polyurethane prepolymer and then the OH groups of this prepolymer and/or polyester are capped with an isocyanate-functional alkoxysilane.
10 . The process for the production of polyurethanes modified with alkoxysilane groups according to claim 9 A), wherein the aminosilane has the general formula (II),
wherein X signifies the same or different alkoxy or alkyl residues, which may also be bridged, provided that one alkoxy residue is present on each Si atom,
Q is a difunctional, linear or branched aliphatic residue and Z denotes an aliphatic C1-C12 alkoxy residue.
11 . The process for the production of polyurethanes modified with alkoxysilane groups according to claim 10 , further comprising cyclocondensation to form a hydantoin.
12 . An adhesive, coating or primer which comprising at least one alkoxysilane group-containing polyurethane according to claim 1 .