Moisture curable polymer systems based on a mixture of polysilylated polyethers
AssigneeDow Global Technologies LLC
InventorsThomas Willumstad, Subodh P. Jagtap
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Abstract
Low viscosity mixtures of polysilylated polyethers are described. The mixtures include a) 50 to 95 weight percent of one or more first polysilylated polyethers which are free of urea groups, have an average of two or more terminal hydrolysable silyl groups per molecule and have a molecular weight of 4,000 to 20,000 and 50 to 5 weight percent of one or more second polysilylated polyethers which are free of urea groups, have an average of 1.8 to 4 terminal hydrolysable silyl groups per molecule and have a molecular weight of 1000 to less than 400. The mixtures have surprisingly low viscosities, and are useful as curable components of adhesive, sealant, caulking and/or coating compositions.
Claims12
A moisture-curable polysilylated polyether composition comprising a mixture of polysilylated polyethers, wherein the mixture comprises
- a) 50 to 95 weight percent, based on the combined weights of a) and b), of one or more first polysilylated polyethers which are free of urea groups, have an average of two or more terminal hydrolysable silyl groups per molecule and have a molecular weight of 4,000 to 20,000, the first polysilylated polyether(s) being a reaction product of a i) linear polyether having a terminal isocyanate group, a terminal hydrolysable silyl group and a number average molecular weight of 250 to 2000 and (ii) a polyether polyol nominally having 2 to 6 hydroxyl groups per molecule and a hydroxyl equivalent weight of 500 to 2500;
- and
- b) 50 to 5 weight percent, based on the combined weights of a) and b), of one or more second polysilylated polyethers which are free of urea groups, have an average of 1.8 to 4 terminal hydrolysable silyl groups per molecule and have a molecular weight of 1000 to less than 4,000, the second polysilylated polyether(s) being a reaction product of i) a linear monosilylated polyether monol having a terminal hydroxyl group, a terminal hydrolysable silyl group and a molecular weight of 250 to 1500 and ii) a coupling agent having at least two groups reactive with hydroxyl groups and a molecular weight of up to 500.
A method for making a moisture-curable polysilylated polyether composition, comprising the steps of
- (I) Forming a first reaction mixture containing at least one starting linear monosilylated polyether monol having a terminal hydroxyl group, a terminal hydrolysable silyl group and a molecular weight of 250 to 1500 and at least one diisocyanate and a molecular weight of up to 500, the linear monosilylated polyether monol and polyisocyanate being provided in amounts such that greater than one equivalent of isocyanate groups is provided per equivalent of hydroxyl groups on the linear monosilylated polyether monol;
- II) reacting the first reaction mixture from step I to form a reaction product containing i) at least one linear monosilylated polyether isocyanate having a terminal isocyanate group, a terminal hydrolysable silyl group and a molecular weight of 500 to 2000 and ii) a polysilylated polyether having at least two terminal hydrolysable silyl groups and a molecular weight of 1000 to less than 4000, which polysilylated polyether lacks isocyanate groups and corresponds to a reaction product of the polyisocyanate with one molecule of the starting linear polyether per isocyanate group of the stating polyisocyanate;
- (III) combining the reaction product formed in step II) with at least one polyether polyol nominally having 2 to 6 hydroxyl groups per molecule and a hydroxyl equivalent weight of 500 to 2500 to form a second reaction mixture, and
- (IV) reacting the polyether polyol(s) and the linear monosilylated polyether isocyanate in the second reaction mixture in the presence of the polysilylated polyether formed in step II to produce a mixture of polysilylated polyethers.
Dependencies are inferred from the claim text.