Process for producing modified conjugated diene based polymer, modified conjugated diene based polymer produced by the process, rubber composition, and tire

Abstract

The invention provides a process for producing a modified conjugated diene based polymer which attains favorable interaction between a rubber component and carbon black and/or silica, thereby improving dispersibility of the fillers, and which exhibits excellent properties such as heat-buildup-suppressing performance, fracture characteristics, and wear resistance; a modified conjugated diene based polymer produced through the process; a rubber composition containing the diene polymer; and a tire produced from the rubber composition and exhibiting the above properties. The process for producing a modified conjugated diene based polymer includes a step (a) of reacting a silicon compound with a conjugated diene based polymer having an active end so that the reaction takes place at the active end, the silicon compound having a protected primary amino group in the molecule thereof and a bi-functional silicon atom to which a hydrocarbyloxy group and a reactive group including a hydrocarbyloxy group are bonded, to thereby modify the active end, and a step (b) of performing condensation reaction which involves the compound having a bi-functional silicon atom, in the presence of a titanium compound serving as a titanium-based condensation-accelerating agent.

1 . A process for producing a modified conjugated diene based polymer, the process comprising
 a step (a) of reacting a silicon compound with a conjugated diene based polymer having an active end so that the reaction takes places at the active end, the silicon compound having a protected primary amino group in the molecule thereof and a bi-functional silicon atom to which a hydrocarbyloxy group and a reactive group including a hydrocarbyloxy group are bonded, to thereby modify the active end, and   a step (b) of performing condensation reaction which involves the compound having a bi-functional silicon atom, in the presence of a titanium compound serving as a titanium-based condensation-accelerating agent.   
     
     
         2 . A process for producing a modified conjugated diene based polymer as described in  claim 1 , which further includes a deprotection step (c) of hydrolyzing a group which is bonded to the active end of the conjugated based polymer and which has been derived from the compound having a bi-functional silicon atom, whereby the protected primary amino group contained in the group bonded to the active end is converted to a free amino group. 
     
     
         3 . A process for producing a modified conjugated diene based polymer as described in  claim 1 , wherein the compound having a bi-functional silicon atom employed in the step (a) is a silicon compound represented by formula (1): 
       
         
           
           
               
               
           
         
       
       (wherein each of R 1  and R 2  represents a hydrocarbon group having 1 to 20 carbon atoms, each of R 3  to R 5  represents a hydrocarbon group having 1 to 20 carbon atoms, R 6  represents a alkylene group having 1 to 12 carbon atoms, A represents a reactive group, and f is an integer of 1 to 10);
 a silicon compound represented by formula (II): 
 
       
         
           
           
               
               
           
         
       
       (wherein each of R 7  to R 11  represents a hydrocarbon group having 1 to 20 carbon atoms, and R 12  represents a alkylene group having 1 to 12 carbon atoms); or
 a silicon compound represented by formula (III): 
 
       
         
           
           
               
               
           
         
       
       (wherein each of R 1  and R 2  represents a hydrocarbon group having 1 to 20 carbon atoms, each of R 3  to R 5  represents a hydrocarbon group having 1 to 20 carbon atoms, R 6  represents a alkylene group having 1 to 12 carbon atoms, R 13  represents a alkylene group having 1 to 12 carbon atoms, A represents a reactive group, and f is an integer of 1 to 10). 
     
     
         4 . A process for producing a modified conjugated diene based polymer as described in  claim 3 , wherein the group A in formula (I) is a halogen atom or a alkoxyl group having 1 to 20 carbon atoms. 
     
     
         5 . A process for producing a modified conjugated diene based polymer as described in  claim 1 , wherein the conjugated diene based polymer having an active end is produced through anionic polymerization, in the presence of an organic alkali metal compound serving as a polymerization initiator, of a conjugated diene compound singly or of a conjugated diene compound and an aromatic vinyl compound in combination. 
     
     
         6 . A process for producing a modified conjugated diene based polymer as described in  claim 5 , wherein the conjugated diene compound is at least one species selected from the group of 1,3-butadiene, isoprene, and 2,3-dimethyl-1,3-butadiene. 
     
     
         7 . A process for producing a modified conjugated diene based polymer as described in  claim 5 , wherein the aromatic vinyl compound is styrene. 
     
     
         8 . A process for producing a modified conjugated diene based polymer as described in  claim 5 , wherein the conjugated diene based polymer has a polymer unit derived from an aromatic vinyl compound in an amount of 0 to 55 mass % based on the total polymer unit present in the conjugated diene based polymer and a vinyl bond content of 7 to 65 mass % based on the total conjugated diene portion. 
     
     
         9 . A process for producing a modified conjugated diene based polymer as described in  claim 1 , wherein the condensation-accelerating agent employed in the step (b) is at least one species selected from among a titanium alkoxide, a titanium carboxylate salt, a titanium acetylacetonate complex salt, and a salt mixture thereof. 
     
     
         10 . A modified conjugated diene based polymer produced by a process as recited in  claim 1 . 
     
     
         11 . A rubber composition comprising a modified conjugated diene based polyner as recited in  claim 10 . 
     
     
         12 . A rubber composition as described in  claim 11 , which comprises a rubber component containing 20 mass % or more of the modified conjugated diene base polymer in an amount of 100 parts by mass and silica and/or carbon black in the total amount of 20 to 120 parts by mass. 
     
     
         13 . A rubber composition as described in  claim 11 , wherein the rubber component comprises the modified conjugated diene based polymer in an amount of 15 to 100 mass % and at least one species selected from among a natural rubber, a synthetic isoprene rubber, a butadiene rubber, a styrene-butadiene rubber, an ethylene-α-olefin copolymer rubber, an ethylene-α-olefin-diene copolymer rubber, a chloroprene rubber, a halogenated butyl rubber, and a styrene-isobutylene copolymer having a halomethyl group, in an amount of 85 to 0 mass %. 
     
     
         14 . A pneumatic tire employing a rubber composition as recited in  claim 11 . 
     
     
         15 . A pneumatic tire employing a rubber composition as recited in  claim 11  as a tread, a base tread, or a sidewall thereof.