Use of a room-temperature hardening composition containing a polyether polymer containing hydrolyzable silicon groups and a silanol condensation catalyst, for example as sealant or adhesive, is well known and useful industrially. An example of the method of producing such a hydrolyzable silicon group-containing polyether polymer is to produce a polyether polymer having terminal OH groups, convert the terminal OH groups to olefins, and hydrosilylate the olefin with a hydrolyzable silicon group-containing hydrosilane compound.
However, if an oxidative impurity is present in the unsaturated group-containing polyether prepared by conversion of the terminal OH groups, the impurity inhibits the following hydrosilylation reaction in the method. For prevention of such a reaction inhibition known is a method of advancing the hydrosilylation reaction without problem by decomposing the oxidative impurity present in the unsaturated group-containing polyether with ascorbic acid (see Patent Document 1).
On the other hand, a method of polymerizing an alkyleneoxide by using an alkali metal catalyst such as KOH, a double metal cyanide complex catalyst as a catalyst or the like has been known as a method of producing polyether polymers having terminal OH groups. In such a polymerization method, the catalyst used in polymerization and the residue thereof are removed from the system by a method suitable for the system.
For example, a method of using a double metal cyanide complex gives a polymer having a number-average molecular weight of 8,000 or more and a narrow molecular weight distribution. A curable resin composition containing the hydrolyzable silicon group-containing polyether polymer prepared by such a method is useful, for making the hardened product more flexible, reducing the viscosity of the composition, and making the composition more processable.
The double metal cyanide complexes are removed, for example, by water extraction (see for example Patent Document 2). However, vigorous agitation of the polyether polymer and water for sufficient contact results in emulsification of the system containing the polymer substance, demanding an extended period for separation of the polyether polymer from water after agitation and also a larger facility. Alternatively, gentle agitation for prevention of emulsification also caused a problem of insufficient extraction of metal impurities.
Alternatively, methods of adding a chelating agent such as ethylenediamine tetraacetic acid (EDTA) were also proposed (see for example Patent Document 3). These methods resulted in residual of a chelating agent such as EDTA in the polymer, which functions as a hydrosilylation reaction inhibitor, and thus had a disadvantage of demanding complete removal of EDTA before hydrosilylation.
Patent Document 1: Japanese Unexamined Patent Publication No. 10-212349
Patent Document 2: Japanese Unexamined Patent Publication No. 2003-105079
Patent Document 3: Japanese Unexamined Patent Publication No. 06-200013