6 ml was weighed from an ethanol solution ( 6 . 6 ml ) of dichlorodibutyltin ( iv )( 3 . 34 g , 11 mmole ) and added to an ethanol solution ( 13 ml ) of potassium thiocyanate ( 1 . 94 g , 20 mmole ). this solution was stirred at 100 ° c . for 20 hours , returned to room temperature and the produced potassium chloride was filtered . a solvent of a filtrate was removed and recrystallization from toluene afforded dibutyltin ( iv ) diisothiocyanate as white needle crystal ( yield 57 %). dibutyltin oxide ( iv )( 7 . 47 g , 30 mmole ) and an ethanol solution ( 100 ml ) of dibutyl ( iv ) diisothiocyanate ( 3 . 5 g , 10 mmole ) obtained by the above method were stirred at 100 ° c . for 6 hours . then , ethanol was removed , the mixture was exposed to the external air for one day and , thereafter , recrystallization from n - hexane afforded 1 - hydroxy - 3 - isothiocyanate - 1 , 1 , 3 , 3 - tetrabutyldistannoxane as white powder ( yield 85 %). succinic acid ( 0 . 295 g , 2 . 5 mmole ), 1 , 4 - butanediol ( 0 . 225 g , 2 . 5 mmole ) and 1 - hydroxy - 3 - isothiocyanate - 1 , 1 , 3 , 3 - tetrabutyldistannoxane ( 0 . 014 g , 0 . 025 mmole ) were placed in a round - bottom flask equipped with a condenser and stirred at 120 ° c . for 72 hours . after the reaction was complete , methanol was added to stir for 12 hours . after the resulting white powdery polymer was filtered , the polymer was dried at 60 ° c . under reduced pressure to obtain a polyester . number average molecular weight mn ( polystyrene standard ) of the resulting polyester was measured by gpc and found to be 4800 . in addition , molecular weight distribution mw / mn was 1 . 70 . further , solubility of the resulting polyester in an organic solvent was examined and it was found that the polyester is easily dissolved in chloroform , m - cresol and sulfuric acid , and dissolved in acetone , ethyl acetate , toluene , 1 , 4 - dioxane , sulfuric acid , n - methylpyrrolidone , n , n - dimethylformamide , n , n - dimethylacetamide and dimethyl sulfoxide . in addition , the polyester was not dissolved in methanol and hexane . 1h - nmr ( cdcl 3 ) δ : 1 . 71 , 2 . 63 , 4 . 12 ( 4h , m , ch 2 ) 13c - nmr ( cdcl 3 ) δ : 25 . 2 , 29 . 1 , 64 . 3 ( ch 2 ), 172 . 6 ( c ═ o ) according to the same manner as that of example 1 except that 1 , 4 - butanediol was used at an amount of 2 . 525 mmole ( 1 . 01 - fold mole relative to succinic acid ), a polyester was obtained ( yield 83 %). number average molecular weight mn of the resulting polyester was 7800 , and molecular weight distribution - mw / mn was 1 . 98 . according to the same manner as that of example 1 except that 1 , 4 - butanediol was used at an amount of 2 . 575 mmole ( 1 . 03 - fold mole relative to succinic acid ), a polyester was obtained ( yield 80 %). number average molecular weight mn of the resulting polyester was 10000 , and molecular weight distribution mw / mn was 2 . 41 . according to the same manner as that of example 1 except that 1 , 4 - butanediol was used at an amount of 2 . 625 mmole ( 1 . 05 - fold mole relative to succinic acid ), a polyester was obtained ( yield 90 %). number average molecular weight mn of the resulting polyester was 12100 , and molecular weight distribution mw / mn was 2 . 63 . this polymer corresponds to 70 - mer and it means that 99 . 8 % of produced water was removed at an equilibrium constant of 4700 or an equilibrium constant of 10 . according to the same manner as that of example 1 except that 1 , 4 - butanediol was used at an amount of 2 . 75 mmole ( 1 . 10 - fold mole relative to succinic acid ), a polyester was obtained ( yield 92 %). number average molecular weight mn of the resulting polyester was 9900 , and molecular weight distribution mw / mn was 2 . 35 . according to the same manner as that of example 4 except that a polymerization temperature was 130 ° c ., a polyester was obtained ( yield 93 %). number average molecular weight mn of the resulting polyester was 5000 , and molecular weight distribution mw / mn was 2 . 16 . according to the same manner as that of example 4 except that a polymerization temperature was 150 ° c ., a polyester was obtained ( yield 90 %). number average molecular weight mn of the resulting polyester was 4700 , and molecular weight distribution mw / mn was 2 . 18 . according to the same manner as that of example 4 except that an amount of 1 - hydroxy - 3 - isothiocyanate - 1 , 1 , 3 , 3 - tetrabutyldistannoxane as a catalyst to be used was 0 . 0014 g ( 0 . 0025 mmole ), a polyester was obtained ( yield 86 %). number average molecular weight mn of the resulting polyester was 3500 , and molecular weight distribution mw / mn was 2 . 16 . according to the same manner as that of example 1 except that a polymerization time was 168 hours , a polyester was obtained . number average molecular weight mn of the resulting polyester was 7400 , and molecular weight distribution mw / mn was 1 . 91 . succinic acid ( 2 . 36 g , 20 mmole ), 1 , 4 - butanediol ( 1 . 80 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 2 mmole ) as a catalyst were placed in a round - bottom flask equipped with a condenser and a stirrer , nitrogen is flown therein at 5 ml / min . under normal pressure and the system is heated at 120 ° c . for 1 hour into the uniform state . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , which was heated at 193 ° c . to perform a polycondensation reaction for 60 hours under refluxing with decalin while stirring . after the reaction was completed , decalin was removed by drainage and subsequently methanol was added thereto to stir for 12 hours . the resulting white powder polymer was filtered and dried at 60 ° c . to obtain a polyester . number average molecular weight mn ( polystyrene standard ) of the resulting polyester was measured by gpc and found to be 10000 . in addition , molecular weight distribution mw / mn was 1 . 71 . succinic acid ( 2 . 36 g , 20 mmole ), 1 , 4 - butanediol ( 1 . 80 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 2 mmole ) as a catalyst were placed in a round - bottom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 120 ° c . for 1 hour into the uniform state under normal pressure . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , which was heated at 193 ° c . and stirred for 48 hours to perform a polycondensation reaction under reflux with decalin while distilling water off . after the reaction was completed , decalin was removed by drainage and subsequently methanol was added thereto to stir for 12 hours . the resulting white powder polymer was filtered and dried at 60 ° c . to obtain a polyester . number average molecular weight mn ( polystyrene standard ) of the resulting polyester was measured by gpc and found to be 45000 . in addition , molecular weight distribution mw / mn was 1 . 74 . according to the same manner as that of example 11 except that 1 , 3 - dichloro - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 1 . 060 g , 0 . 10 mmole ) was used , a polyester was obtained . number average molecular weight mn of the resulting polyester was 43000 , and molecular weight distribution mw / mn was 1 . 86 . according to the same manner as that of example 11 except that n - octane ( 4 ml , 2 . 8 g ) was used in stead of decalin , a polyester was obtained . a temperature for a polycondensation reaction was 120 ° c . number average molecular weight mn of the resulting polyester was 7000 , and molecular weight distribution mw / mn was 2 . 10 . according to the same manner as that of example 11 except that n - nonane ( 4 ml , 2 . 9 g ) was used in stead of decalin , a polyester was obtained . a temperature for a polycondensation reaction was 150 ° c . number average molecular weight mn of the resulting polyester was 18000 , and molecular weight distribution mw / mn was 1 . 80 . according to the same manner as that of example 11 except that 1 - chloro - 3 - hydroxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 0011 g , 0 . 002 mmole ) was used , a polyester was obtained . number average molecular weight mn of the resulting polyester was 147000 , and molecular weight distribution mw / mn was 1 . 80 . 1 , 4 - cyclohexanedicarboxylic acid ( 3 . 44 g , 20 mmole ), 1 , 4 - cyclohexanedimethanol ( 2 . 88 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 2 mmole ) as a catalyst were placed in a round - buttom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 120 ° c . for 1 hour into the uniform state under normal pressure . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , and the same procedures as those of example 11 were performed to obtain a polyester . a temperature for a polycondensation reaction was 150 ° c . and a time for a polycondensation reaction was 72 hours . number average molecular weight mn of the resulting polyester was 15000 . in addition , molecular weight distribution mw / mn was 2 . 10 . 2 , 5 - norbornanedicarboxylic acid ( 3 . 68 g , 20 mmole ), 2 , 5 - norbornanedimethanol ( 3 . 12 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 2 mmole ) as a catalyst were placed in a round - buttom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 120 ° c . for 1 hour into the uniform state under normal pressure . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , and the same procedures as those of example 11 were performed to obtain a polyester . a temperature for a polycondensation reaction was 120 ° c . and a time for a polycondensation reaction was 72 hours . number average molecular weight mn of the resulting polyester was 6000 . in addition , molecular weight distribution mw / mn was 1 . 92 . 2 , 5 - norbornanedicarboxylic acid ( 3 . 68 g , 20 mmole ), 2 , 5 - norbornanedimethanol ( 3 . 12 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 022 g , 0 . 04 mmole ) as a catalyst were placed in a round - buttom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 120 ° c . for 1 hour into the uniform state under normal pressure . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , and the same procedures as those of example 11 were performed to obtain a polyester . a temperature for a polycondensation reaction was 120 ° c . and a time for a polycondensation reaction was 72 hours . number average molecular weight mn of the resulting polyester was 4000 . in addition , molecular weight distribution mw / mn was 1 . 80 . terephthalic acid ( 3 . 32 g , 20 mmole ), 2 , 5 - norbornanedimethanol ( 3 . 12 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 0 . 2 mmole ) as a catalyst were placed in a round - buttom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 120 ° c . for 1 hour into the uniform state under normal pressure . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , and the same procedures as those of example 11 were performed to obtain a polyester . a temperature for a polycondensation reaction was 120 ° c . and a time for a polycondensation reaction was 72 hours . number average molecular weight mn of the resulting polyester was 10000 . in addition , molecular weight distribution mw / mn was 1 . 96 . 1 , 3 - adamantanedicarboxylic acid ( 4 . 49 g , 20 mmole ), 1 , 3 - adamantanedimethanol ( 3 . 36 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 0 . 2 mmole ) as a catalyst were placed in a round - buttom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 190 ° c . for 1 hour into the uniform state under normal pressure . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , and the same procedures as those of example 11 were performed to obtain a polyester . a temperature for a polycondensation reaction was 120 ° c . and a time for a polycondensation reaction was 72 hours . number average molecular weight mn of the resulting polyester was 8000 . in addition , molecular weight distribution mw / mn was 2 . 12 . tricyclodecanedicarboxylic acid ( 4 . 49 g , 20 mmole ), tricyclodecanedimethanol ( 3 . 92 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 0 . 2 mmole ) as a catalyst were placed in a round - buttom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 120 ° c . for 1 hour into the uniform state under normal pressure . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , and the same procedures as those of example 11 were performed to obtain a polyester . a temperature for a polycondensation reaction was 120 ° c . and a time for a polycondensation reaction was 72 hours . number average molecular weight mn of the resulting polyester was 13000 . in addition , molecular weight distribution mw / mn was 2 . 30 . 5 , 7 - dimethyl - 1 , 3 - adamantanedicarboxylic acid ( 5 . 05 g , 20 mmole ), 5 , 7 - dimethyl - adamantanediol ( 3 . 93 g , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 0 . 2 mmole ) as a catalyst were placed in a round - buttom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 190 ° c . for 1 hour under normal pressure . further , decalin ( 4 ml , 3 . 6 g ) was placed into the two - phased state , and the same procedures as those of example 11 were performed to obtain a polyester . a temperature for a polycondensation reaction was 120 ° c . and a time for a polycondensation reaction was 72 hours . number average molecular weight mn of the resulting polyester was 9000 . in addition , molecular weight distribution mw / mn was 2 . 04 . succinic acid ( 2 . 36 kg , 20 mmole ), 1 , 4 - butanediol ( 1 . 80 kg , 20 mmole ) and 1 - chloro - 3 - hydoxy - 1 , 1 , 3 , 3 ,- tetra n - butyldistannoxane ( 0 . 11 g , 0 . 2 mmole ) as a catalyst were placed in a round - buttom flask equipped with a dean stark apparatus , a condenser and a stirrer , which was heated at 120 ° c . for 1 hour into the uniform state under normal pressure . further , decalin ( 4ml , 3 . 6 g ) was placed into the two - phased state , which was heated at 193 ° c . and stirred for 48 hours under reflux with decalin while distilling water off to perform a polycondensation reaction . after the reaction was completed , decalin was removed by drainage , the resulting polymer was supplied to a biaxial extruder and extruded at 150 ° c . under vacuum to pelletize with a pelletizer , to obtain a polyester . number average molecular weight mn of the resulting polyester was 90000 . in addition , molecular weight distribution mw / mn was 2 . 28 . in example 10 , stirring was performed at 193 ° c . for 60 hours without the use of decalin . after the reaction was completed , methanol was added to stir for 12 hours . the resulting powdery polymer was filtered and dried at 60 ° c . under reduced pressure to obtain a polyester . number average molecular weight of the resulting polyester mn was 4000 and molecular weight distribution mw / mn was 1 . 81 . according to the process of the invention , high polymerization degree aliphatic polyester can be easily obtained without the use of a high boiling point solvent and dehydration procedure under reduced pressure . further , an aliphatic polyester can be industrially produced effectively .