Hardenable composition

1. A curable composition

which comprises an organic polymer (A) containing reactive silyl groups represented by the general formula (1) given below wherein a is 3 and an organic polymer (B) containing an average of 0.5 to 1.0 reactive silyl groups represented by the general formula (1) given below per molecule;

—Si(R 1 3-a )X a   (1)

wherein R 1 represents an alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms, an aralkyl group containing 7 to 20 carbon atoms or a triorganosiloxy group represented by (R′) 3 SiO— (in which the three R′ groups may be the same or different and each represents a monovalent hydrocarbon group containing 1 to 20 carbon atoms) and, when there are two or more R 1 groups, they may be the same or different, and X represents a hydroxyl group or a hydrolysable group and, when there are two or more X groups, they may be the same or different, and a represents 1, 2 or 3, and

wherein the main chain of each of the organic polymers (A) and (B) is an oxyalkylene polymer, and

the molecular weight of the organic polymer (B) is lower than the molecular weight of the organic polymer (A) by not less than 3,000,

the organic polymer (B) contains no urethane bond or urea bond with in the molecule, and

wherein the curable composition contains no organic polymer that has a vinyl polymer as a main chain skeleton.

2. A curable composition

which comprises an organic polymer (A) containing reactive silyl groups represented by the general formula (1) given below wherein a is 3 and an organic polymer (B) containing an average of 0.5 to 1.0 reactive silyl groups represented by the general formula (1) given below per molecule

—Si(R 1 3-a )X a   (1)

wherein R 1 represents a alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms, an aralkyl group containing 7 to 20 carbon atoms or a triorganosiloxy group represented by (R′) 3 SiO— (in which the three R′ groups may be the same or different and each represents a monovalent hydrocarbon group containing 1 to 20 carbon atoms) and, when there are two or more R 1 groups, they may be the same or different, and X represents a hydroxyl group or a hydrolysable group and, when there are two or more X groups, they may be the same or different, and a represents 1, 2, or 3, and

wherein the main chain of each of the organic polymers (A) and (B) is an oxyalkylene polymer,

the molecular weight of the organic polymer (B) is lower than the molecular weight of the organic polymer (A) by not less that 3,000,

the reactive silyl group in the organic polymer (B) is a reactive silyl group represented by the general formula (1) in which a is 2, and

wherein the curable composition contains no organic polymer that has a vinyl polymer as a main chain skeleton.

3. The curable composition according to claim 1

wherein the reactive silyl group in the organic polymer (B) is a reactive silyl group represented by the general formula (1) in which a is 3.

4. The curable composition according to claim 1

wherein the organic polymer (B) is a polymer obtained by reacting the above-mentioned organic polymer with a compound containing both a functional group capable of reacting with the reactive group in the above-mentioned organic polymer and a reactive silyl group represented by the general formula (1) in a compound-to-polymer mole ratio of not lower than 0.5 and not higher than 1.0.

5. The curable composition according to claim 1

wherein the organic polymer (B) contains substantially one reactive silyl group represented by the general formula (1) per molecule.

6. The curable composition according to claim 1

wherein the organic polymer (B) has a molecular weight of not higher than 8,000.

7. The curable composition according to claim 1

wherein the organic polymer (A) contains no urethane bond or urea bond within the molecule.

8. The curable composition according to claim 2

wherein the organic polymer (B) is a polymer obtained by reacting the above-mentioned organic polymer with a compound containing both a functional group capable of reacting with the reactive group in the above-mentioned organic polymer and a reactive silyl group represented by the general formula (1) in a compound-to-polymer mole ratio of not lower than 0.5 and not higher than 1.0.

9. The curable composition according to claim 3

wherein the organic polymer (B) is a polymer obtained by reacting the above-mentioned organic polymer with a compound containing both a functional group capable of reacting with the reactive group in the above-mentioned organic polymer and a reactive silyl group represented by the general formula (1) in a compound-to-polymer mole ratio of not lower than 0.5 and not higher than 1.0.

10. The curable composition according to claim 2

wherein the organic polymer (B) contains substantially one reactive silyl group represented by the general formula (1) per molecule.

11. The curable composition according to claim 3

wherein the organic polymer (B) contains substantially one reactive silyl group represented by the general formula (1) per molecule.

12. The curable composition according to claim 4

wherein the organic polymer (B) contains substantially one reactive silyl group represented by the general formula (1) per molecule.

13. The curable composition according to claim 2

wherein the organic polymer (B) has a molecular weight of not higher than 8,000.