A thiol group-containing polymer represented by:

HS(RS.sub.r).sub.nRSH

wherein R is an organic group including a OCH.sub.2O bond and a branched alkylene group, n is an integer of from 1 to 200, r is an integer of from 1 to 5, an average value of r is 1.1 or more and lower than 1.8, and the thiol group-containing polymer is a liquid at room temperature and has a specific gravity at 23 C. of 1.20 to 1.27.

A thiol group-containing polymer represented by:

HS(RS.sub.r).sub.nRSH

wherein R is an organic group including a OCH.sub.2O bond and a branched alkylene group, n is an integer of from 1 to 200, r is an integer of from 1 to 5, an average value of r is 1.1 or more and lower than 1.8, and the thiol group-containing polymer is a liquid at room temperature and has a specific gravity at 23 C. of 1.20 to 1.27.

A thiol group-containing polymer is represented by HS(RS.sub.r).sub.nRSH, wherein R is an organic group including a OCH.sub.2O bond and/or a branched alkylene group, n is an integer of from 1 to 200, r is an integer of from 1 to 5, and the average value of r is 1.1 or more and 1.8 or less. A curable composition using the thiol group-containing polymer can be used in sealants, adhesives, paints and the like, which require properties such as a low specific gravity, a low viscosity and a low glass transition temperature.

A thiol group-containing polymer is represented by HS(RS.sub.r).sub.nRSH, wherein R is an organic group including a OCH.sub.2O bond and/or a branched alkylene group, n is an integer of from 1 to 200, r is an integer of from 1 to 5, and the average value of r is 1.1 or more and 1.8 or less. A curable composition using the thiol group-containing polymer can be used in sealants, adhesives, paints and the like, which require properties such as a low specific gravity, a low viscosity and a low glass transition temperature.

A method of producing a thiol group-containing polymer includes reacting bis(2-chloroethyl) formal with sodium hydrosulfide, wherein the thiol group-containing polymer is represented by general formula:

HS(RS.sub.r).sub.nRSH

where R is an organic group including a C.sub.2H.sub.4OCH.sub.2OC.sub.2H.sub.4 structure, n is an integer of from 1 to 200, r is an integer of from 1 to 5, and the average value of r is 1.1 or more and lower than 1.8, and wherein the thiol group-containing polymer is a liquid polymer.

A method of producing a thiol group-containing polymer includes reacting bis(2-chloroethyl) formal with sodium hydrosulfide, wherein the thiol group-containing polymer is represented by general formula:

HS(RS.sub.r).sub.nRSH

where R is an organic group including a C.sub.2H.sub.4OCH.sub.2OC.sub.2H.sub.4 structure, n is an integer of from 1 to 200, r is an integer of from 1 to 5, and the average value of r is 1.1 or more and lower than 1.8, and wherein the thiol group-containing polymer is a liquid polymer.