Curable composition

1. A curable composition comprising:

(A) an organic polymer having a silicon-containing group which is capable of crosslinking by forming siloxane bonds and is represented by the general formula (1):

—SiR 1 X 2   (1)

wherein R 1 represents any of an alkyl group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or a triorganosiloxy group represented by (R′) 3 SiO— where R′ is a hydrocarbon group having 1 to 20 carbon atoms and three R′s may be the same or different, X represents hydroxyl group or a hydrolyzable group and two Xs may be the same or different, wherein a main chain skeleton of said organic polymer (A) is at least one selected from the group consisting of polyoxyalkylene polymers, saturated hydrocarbon polymers and (meth)acrylate polymers,

(B) one or more kinds selected from a titanium catalyst, an aluminum catalyst and a zirconium catalyst and

(C) a low molecular weight compound containing a hydrolyzable silicon group and having a molecular weight of from 100 to 1,000, characterized in that a ratio (a/b) of the total mole (a) of titanium atoms, aluminum atoms and zirconium atoms of the component (B) in the composition to the total mole (b) of silicon atoms of the total component (C) in the composition is not less than 0.51.

2. The curable composition according to claim 1 , wherein said titanium catalyst is a compound represented by the general formula (2):

Ti(OR 2 ) 4   (2)

wherein R 2 is an organic group, and four R 2 s may be each the same or different.

3. The curable composition according to claim 2 , wherein said titanium catalyst is a titanium chelate represented by the general formula (2).

4. The curable composition according to claim 3 , wherein said titanium chelate is a compound represented by the general formula (3):

wherein each of n R 3 s is independently a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms, each of (4-n) R 4 s is independently hydrogen atom or a substituted or unsubstituted hydrocarbon group having 1 to 8 carbon atoms, each of (4-n) A 1 s and (4-n) A 2 s is independently —R 5 or —OR 5 where R 5 is a substituted or unsubstituted hydrocarbon group having 1 to 8 carbon atoms, n is 0, 1, 2 or 3, and/or a compound represented by the general formula (4):

wherein R 4 , A 1 and A 2 are the same as defined above; R 6 is a substituted or unsubstituted divalent hydrocarbon group having 1 to 20 carbon atoms.

5. The curable composition according to claim 1 , wherein said aluminum catalyst is represented by the general formula (5):

Al(OR 7 ) 3   (5)

wherein R 7 is an organic group, and three R 7 s may be each the same or different.

6. The curable composition according to claim 5 , wherein said aluminum catalyst is an aluminum chelate represented by the general formula (5).

7. The curable composition according to claim 6 , wherein said aluminum chelate is a compound represented by the general formula (6):

wherein R 8 and R 9 are hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, R 8 and R 9 may be the same or different, m R 8 s may be each the same or different, and (3-m) R 9 s may be each the same or different; A 3 and A 4 are selected from —R 10 or —OR 10 where R 10 is a hydrocarbon group having 1 to 20 carbon atoms, A 3 and A 4 may be the same or different, (3-m) A 3 s may be each the same or different, and (3-m) A 4 s may be each the same or different; m is 0, 1 or 2, and/or a compound represented by the general formula (7):

wherein R 9 , A 3 and A 4 are the same as defined above; R 11 is a divalent hydrocarbon group having 1 to 20 carbon atoms.

8. The curable composition according to claim 1 , wherein said zirconium catalyst is represented by the general formula (8):

Zr(OR 12 ) 4   (8)

wherein R 12 is an organic group, and four R 12 s may be each the same or different.

9. The curable composition according to claim 8 , wherein said zirconium catalyst is a zirconium chelate represented by the general formula (8).

10. The curable composition according to claim 9 , wherein said zirconium chelate is a compound represented by the general formula (9):

wherein R 13 and R 14 are hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, R 13 and R 14 may be the same or different, l R 13 s may be each the same or different, and (4-l) R 14 s may be each the same or different; A 5 and A 6 are selected from —R 15 or —OR 15 where R 15 is a hydrocarbon group having 1 to 20 carbon atoms, A 5 and A 6 may be the same or different, (4-l) A 5 s may be each the same or different, and (4-l) A 6 s may be each the same or different; l is 0, 1, 2 or 3, and/or a compound represented by the general formula (10):

wherein R 14 , A 5 and A 6 are the same as defined above; R 16 is a divalent hydrocarbon group having 1 to 20 carbon atoms.

11. The curable composition according to claim 1 , wherein said component (B) is a titanium catalyst.

12. The curable composition according to claim 1 , wherein the composition contains an amino silane coupling agent as the low molecular weight compound (C).

13. A sealant comprising said curable composition according to claim 1 .

14. An adhesive comprising said curable composition according to claim 1 .

15. The curable composition according to claim 1 , wherein the component (B) is a titanium chelate and/or a zirconium chelate, and

said titanium chelate is a compound represented by the general formula (3):

wherein each of n R 3 s is independently a substituted or unsubstituted hydrocarbon group having 1 to 20 carbon atoms, each of (4-n) R 4 s is independently hydrogen atom or a substituted or unsubstituted hydrocarbon group having 1 to 8 carbon atoms, each of (4-n) A 1 s and (4-n) A 2 s is independently —R 5 or —OR 5 where R 5 is a substituted or unsubstituted hydrocarbon group having 1 to 8 carbon atoms, n is 2, and/or a compound represented by the general formula (4):

wherein R 4 , A 1 and A 2 are the same as defined above; R 6 is a substituted or unsubstituted divalent hydrocarbon group having 1 to 20 carbon atoms, and

said zirconium chelate is a compound represented by the general formula (9):

wherein R 13 and R 14 are hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, R 13 and R 14 may be the same or different, l R 13 s may be each the same or different, and (4-l) R 14 s may be each the same or different; A 5 and A 6 are selected from —R 15 or —OR 15 where R 15 is a hydrocarbon group having 1 to 20 carbon atoms, A 5 and A 6 may be the same or different, (4-l) A 5 s may be each the same or different, and (4-l) A 6 s may be each the same or different; l is 1, and/or a compound represented by the general formula (10):

wherein R 14 , A 5 and A 6 are the same as defined above; R 16 is a divalent hydrocarbon group having 1 to 20 carbon atoms.

16. The curable composition according to claim 1 , wherein the ratio (a/b) is more than 0.51.

17. The curable composition according to claim 1 , wherein the ratio (a/b) is not less than 0.60.