METHOD FOR PRODUCING MODIFIED CONJUGATED DIENE POLYMER, MODIFIED CONJUGATED DIENE POLYMER, POLYMER COMPOSITION, CROSSLINKED POLYMER, AND TIRE

A modified conjugated diene-based polymer is produced that is a modified product of a conjugated diene-based polymer obtained by polymerizing a conjugated diene compound, or polymerizing a conjugated diene compound and an aromatic vinyl compound, in the presence of an alkali metal compound or an alkaline-earth metal compound. The modified conjugated diene-based polymer is produced by a production method that includes a main chain modification step that reacts at least either an unsaturated bond or a functional group that is included in a terminal-modified polymer and is not situated at a terminal of the terminal-modified polymer, with a specific compound that includes a functional group that interacts with silica, the terminal-modified polymer being obtained by introducing a functional group that interacts with silica into at least one terminal of the conjugated diene-based polymer.