Prepolymers with alkoxysilane end groups
Alkoxysilane-terminated prepolymers prepared by reaction of a methylene-spaced isocyanate-reactive group-containing alkoxysilane in molar excess with an isocyanate-reactive prepolymer have high reactivity towards atmospheric moisture while preparing elastomers of high tensile strength and elongation.
1 - 11 . (canceled)
12 . A prepolymer (A) having end groups of the formula [1]
-A-CH 2 —SiR 1 a (OR 2 ) 3-a [1],
where
A is a divalent linking group selected from the group consisting of —O—, —S—, —(R 3 )—, —O—CO—N(R 3 )—, —N(R 3 )—CO—O—, —NH—CO—NH—, —N(R 4 )—CO—NH—, —NH—CO—N(R 4 )—, and —N(R 4 )—CO—N(R 4 )—,
R 1 is an optionally halogen-substituted alkyl, cycloalkyl, alkenyl or aryl radical having 1-10 carbon atoms,
R 2 is an alkyl radical having 1-6 carbon atoms or an ω-oxyalkyl-alkyl radical having in all 2-10 carbon atoms,
R 3 is hydrogen, an optionally halogen-substituted cyclic, linear or branched C 1 to C 18 alkyl radical or alkenyl radical or a C 6 to C 18 aryl radical,
R 4 is an optionally halogen-substituted cyclic, linear or branched C 1 to C 18 alkyl radical or alkenyl radical or a C 6 to C 18 aryl radical, and
a has the value 0, 1 or 2,
the prepolymer (A) prepared by reacting isocyanate-functional prepolymers (A1) with alkoxysilanes (A2) possessing at least one isocyanate-reactive group,
and optionally further components,
with the proviso that the alkoxysilanes (A2) are employed in excess, so that the mol ratio of isocyanate-reactive groups to isocyanate groups is at least 1.2:1.
13 . The prepolymer (A) of claim 12 , in which R 1 is selected from the group consisting of methyl, ethyl, and phenyl groups.
14 . The prepolymer (A) of claim 12 , in which R 2 is a methyl or ethyl group.
15 . The prepolymer (A) of claim 12 , in the preparation of which the ratio of isocyanate-reactive groups to isocyanate groups is from 1.4:1 to 4:1.
16 . The prepolymer (A) of claim 12 , in the preparation of which alkoxysilanes (A2) of the general formula (3)
are employed, where
B 1 is an OH, SH or NH 2 group or a group HR 3 N and
R 1 , R 2 , R 3 and a are as defined in claim 12 .
17 . The prepolymer (A) of claim 12 , in which at least 50% of the alkoxysilyl groups of the general formula [1] are composed of dialkoxysilyl groups.
18 . The prepolymer (A) of claim 12 , in the preparation of which urethane-group-containing prepolymers (A1), prepared by reaction of polyols (A11) and di- or polyisocyanates (A12) are employed as isocyanate-functional prepolymers (A1).
19 . The prepolymer (A) of claim 18 , in which the polyols (A11) have an average molecular weight Mn of 1000 to 25,000.
20 . The prepolymer of claim 18 , in which the polyols (A11) are selected from the group consisting of hydroxyl-functional polyethers, polyesters, polyacrylates and polymethacrylates, polycarbonates, polystyrenes, polysiloxanes, polyamides, polyvinyl esters, polyvinyl hydroxides and polyolefins.
21 . The prepolymer (A) of claim 18 , in which the di- or polyisocyanates (A12) are selected from diisocyanatodiphenylmethane (MDI), tolylene diisocyanate (TDI), diisocyanatonaphthalene (NDI), isophorone diisocyanate (IPDI), perhydrogenated MDI (H-MDI), hexamethylene diisocyanate (HDI), polymeric MDI (P-MDI), triphenylmethane triisocyanate, isocyanurate triisocyanates and biuret triisocyanates.
22 . A moisture curable composition (M) comprising a prepolymer (A) of claim 12 .
23 . The composition of claim 22 , further comprising a low molecular weight alkoxysilane.
24 . The composition of claim 22 , further comprising an alkoxysilane of the formula
where B is selected from the group consisting of R 30 —CO—NH—, R 3 2 N—CO—NH—, —OR 3 , —SR 3 , —NH 2 , —NHR 3 , and —NR 3 2 .