Curable composition having improved curability and adhesion

1. A curable composition comprising (A) an organic polymer having, as a silicon-containing group being capable of crosslinking by forming siloxane bonds, a reactive silicon group represented by the general formula (1):

—SiX 3   (1)

wherein X represents hydroxyl group or a hydrolyzable group and three Xs may be each the same or different, (B) one or more kinds selected from a titanium 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, wherein a ratio (a/b) of the total mole (a) of titanium atoms and zirconium atoms of the component (B) to the total mole (b) of silicon atoms of the component (C) is larger than 0.15, and

a main chain skeleton of said organic polymer (A) includes a urethane group, a urea group or a thiourethane group,

wherein the organic polymer (A) is a polyoxypropylene polymer terminated with trimethoxysilyl group,

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

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

wherein R 3 , A 1 and A 2 are the same as defined above; R 5 is a divalent hydrocarbon group having 1 to 20 carbon atoms, and

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

wherein R 12 and R 13 are hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, R 12 and R 13 may be the same or different, 1 R 12 s may be each the same or different, and (4-1) R 13 s may be each the same or different; A 5 and A 6 are selected from —R 14 or —OR 14 where R 14 is a hydrocarbon group having 1 to 20 carbon atoms, A 5 and A 6 may be the same or different, (4-1) A 5 s may be each the same or different, and (4-1) 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 13 , A 5 and A 6 are the same as defined above; R 15 is a divalent hydrocarbon group having 1 to 20 carbon atoms, and

the low molecular weight compound (C) is a silane coupling agent containing a trimethoxysilyl group.

2. The curable composition according to claim 1 , wherein with respect to 100 parts by weight of the organic polymer (A), said one or more kinds (B) selected from a titanium catalyst and a zirconium catalyst are contained in an amount of from 0.1 to 15 parts by weight and said low molecular weight compound (C) is contained in an amount of from 0.1 to 15 parts by weight.

3. The curable composition according to claim 1 , wherein a glass transition temperature of said organic polymer (A) is not more than 20° C.

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

5. A sealant comprising said curable composition according to Claim 1 .

6. An adhesive comprising said curable composition according Claim 1 .

7. The curable composition according to claim 1 , wherein with respect to 100 parts by weight of the organic polymer (A), said one or more kinds (B) selected from a titanium catalyst and a zirconium catalyst are contained in an amount of from 2 to 14.3 parts by weight and said low molecular weight compound (C) is contained in an amount of from 2.5 to 5 parts by weight.

8. The curable composition according to claim 1 , wherein the low molecular weight compound (C) further contains a primary amino group and/or a vinyl group.

9. The curable composition according to claim 1 , wherein the component (B) is titanium diisopropoxidebis(ethylacetoacetate).

10. The curable composition according to claim 1 , wherein the component (B) is zirconium n-butoxide(acetylacetonate)bis(ethylacetoacetate).

11. The curable composition according to claim 1 , wherein the low molecular weight compound (C) is N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane and/or vinyltrimethoxysilane.