Curable composition

1. A curable composition comprising a reactive silicon group-containing polyoxyalkylene polymer which is obtained by reacting a polyoxyalkylene polymer (A) having a molecular weight distribution of 1.6 or less, a number average molecular weight of 15,000 to 50,000, and 0.8 or more reactive groups, on average, per molecule thereof with an organic compound (B) having in the molecule thereof a reactive silicon group and a functional group capable of reacting with the reactive groups of the polymer (A) in a proportion of 0.8 to 1.5 molecules of the organic compound (B), on average, per molecule of the component (A);

a filler (C);

a curing catalyst (D); and

a plasticizer in an amount of 0 to less than 2 parts by weight in relation to 100 parts by weight of the reactive silicon group-containing polyoxyalkylene polymer.

2. The curable composition according to claim 1 , in which:

in the liquid components of the curable composition according to claim 1 , the ratio y/x of the content y (wt %) of a component having no reactive silicon groups to the content x (wt %) of a component having at least one reactive silicon group is 0.4 or less, with the proviso that x+y=100, wherein:

the liquid component having no reactive silicon groups is a polyoxyalkylene polymer having no reactive silicon groups introduced when the component (A) and the component (B), both according to claim 1 , are reacted with each other; and

in the case where the curable composition according to claim 1 comprises a plasticizer, the liquid component having no reactive silicon groups includes the plasticizer component and the polyoxyalkylene polymer having no reactive silicon groups.

3. The curable composition according to claim 1 , in which the reactive group of the component (A) is an alkenyl group, and the component (B) is an organic compound having a hydrosilyl group as a functional group capable of reacting with the component (A).

4. The curable composition according to claim 1 , in which the reactive group of the component (A) is a hydroxyl group, and the component (B) is an organic compound having an isocyanate group as a functional group capable of reacting with the component (A).

5. The curable composition according to claim 1 , in which the reactive group of the component (A) is an isocyanate group, and the component (B) is an organic compound having an amino group as a functional group capable of reacting with the component (A).

6. The curable composition according to claim 1 , in which the reactive group of the component (A) is an alkenyl group, and the component (B) is an organic compound having a mercapto group as a functional group capable of reacting with the component (A).

7. The curable composition according to claim 2 , in which the reactive group of the component (A) is an alkenyl group, and the component (B) is an organic compound having a hydrosilyl group as a functional group capable of reacting with the component (A).

8. The curable composition according to claim 2 , in which the reactive group of the component (A) is a hydroxyl group, and the component (B) is an organic compound having an isocyanate group as a functional group capable of reacting with the component (A).

9. The curable composition according to claim 2 , in which the reactive group of the component (A) is an isocyanate group, and the component (B) is an organic compound having an amino group as a functional group capable of reacting with the component (A).

10. The curable composition according to claim 2 , in which the reactive group of the component (A) is an alkenyl group, and the component (B) is an organic compound having a mercapto group as a functional group capable of reacting with the component (A).

11. The curable composition according to claim 1 , in which the plasticizer is at least one selected from the group consisting of phthalates; aliphatic dibasic acid esters; epoxidized plasticizers; polyethers; and vinyl polymers.

12. The curable composition according to claim 1 , wherein no plasticizer is present.