jp05 - 105745(1993)-PRODUCTION OF LACTIDE丙交酯的制造方法

PATENT ABSTRACTS OF JAPAN(11)Publication number : 05-105745(43)Date of publication of application : 27.04.1993(51)Int.Cl. C08G 63/08(21)Application number : 03-270781(71)Applicant : MITSUI TOATSU CHEM INC(22)Date of filing : 18.10.1991(72)Inventor : ENOMOTO TSUYOSHIAJIOKA MASANOBUYAMAGUCHI TERUHIRO(54) PRODUCTION OF LACTIDE(57)Abstract:PURPOSE: To obtain a polylactic acid having high molecular weight from lactic acid in a short time in high yield and to obtain a lactide from the polylactic acid in high yield by using tin trifluoromethanesulfonate as a new catalyst.CONSTITUTION: A polylactic acid is produced by dehydrating lactic acid under heating in the presence of a catalyst consisting of tin trifluoromethanesulfonate (TFS tin). The reaction is carried out preferably at 100-200°C and 10-50mmHg pressure to prevent the loss of lactic acid and lactide by distillation. The amount of the TFS tin is preferably 0.01-1wt.% based on the lactic acid from economical point of view. A lactide is produced by heating the polylactic acid in the presence of TFS tin and distilling out the produced lactide.CLAIMS[Claim(s)][Claim 1]A manufacturing method of polylactic acid carrying out heating drying of the lactic acid under existence of trifluoro tin methanesulfonate.[Claim 2]A manufacturing method of lactide making lactide which heated and generated polylactic acid under existence of trifluoro tin methanesulfonate distill.[Claim 3]A manufacturing method of the lactide according to claim 2 whose average molecular weight of polylactic acid is 300 or more.[Claim 4]A manufacturing method of lactide carrying out heating drying of the lactic acid under existence of a catalyst or nonexistence, once manufacturing polylactic acid, heating polylactic acid under existence of trifluoro tin methanesulfonate subsequently, and making generated lactide distill.[Claim 5]A manufacturing method of lactide carrying out heating drying of the lactic acid under existence of trifluoro tin methanesulfonate, once manufacturing polylactic acid, heatingpolylactic acid under existence of trifluoro tin methanesulfonate subsequently, and making generated lactide distill.DETAILED DESCRIPTION[Detailed Description of the Invention][0001][Industrial Application]This invention relates to the manufacturing method of a lactic acid oligomer and lactide using a new catalyst.[0002][Description of the Prior Art]The manufacturing method of the lactide which heats lactic acid gradually to the temperature of 200 ** in the Germany patent specification No. 267826 gazette, and distills the lactide to generate under decompression preferably in it is indicated.[0003]In the Germany patent specification No. 1234703 gazette, the manufacturing method of the lactide from the lactic acid solution under existence of a titaniumtetraalkoxide has indicated. [0004]The manufacturing method of the lactide from polylactic acid is indicated and made the Germany patent specification No. 1083275 under existence of the metal of a periodic table VI group, V fellows, or a group VIII or its salt, for example, a zinc oxide, tin oxide, and antimony oxide.[0005]In JP,63-101378,A, the manufacturing method of the lactide from lactic acid or polylactic acid is indicated under existence of metal tin or halogenation tin.[0006][Problem(s) to be Solved by the Invention]The chemical yield of the lactide by the above-mentioned publication is never satisfying. In this, to JP,63-101378,A with comparatively sufficient lactide yield. The manufacturing method of the lactide "which adds metal tin of a catalyst amount to lactic acid 90%, carries out temperature up of this solution, distilling off water to about 170 ** under the pressure of 15mmHg, makes it convert to oligomer, subsequently carries out temperature up to about 215 ** under the pressure of 7.5mmHg, and makes lactide distill" is indicated. In this method, although metal tin is used as a catalyst, since this is a heterogeneous catalyst, it is activity only in a catalyst surface, but in order to reduce the amount of the catalyst used in consideration of economical efficiency, a catalyst which becomes uniform is desired during a reaction. Metal tin had a fault which fuses above 232 ** and becomes massive and whose surface area of a catalyst decreases remarkably. In order to raise the lactide purity in the rough lactide to distill, it is necessary to generate oligomer in the case of a lactide distillate, and it once needs to prevent the distillate of lactic acid, a chain dimer, a chain trimer, etc. In the catalyst indicated to JP,63-101378,A, although its metal tin was quick, even if that metal tin was used for the generation rate of this oligomer, it was required for 3 to 4 hours to obtain oligomer of sufficient molecular weight for a lactide distillate.[0007]The purpose of this invention is to provide the manufacturing method of the lactide which was excellent in the economical efficiency using a catalyst with high lactide yield quickly [ an oligomer generation rate ].[0008][Means for Solving the Problem]This invention persons found out that oligomerization progressed at a more than twice as many speed as this compared with a catalyst known until now,and polylactic acid was obtained, when lactic acid was heated under existence of trifluoro tin methanesulfonate (it abbreviates to TFS tin hereafter.), as a result of inquiring wholeheartedly. Under existence of TFS tin, when polylactic acid was heated, it found out that lactide was distilled with high yield, and this invention was completed.[0009]Namely, are it a manufacturing method of polylactic acid by which it is characterized that an invention of the 1st of this invention carries out heating drying of the lactic acid under existence of trifluoro tin methanesulfonate (TFS tin), and the 2nd invention, Are it a manufacturing method of lactide by which it is characterized to heat polylactic acid under existence of trifluoro tin methanesulfonate (TFS tin), and to make generated lactide distill, and the 3rd invention, It is a manufacturing method of lactide carrying out heating drying of the lactic acid under existence of a catalyst or nonexistence, once manufacturing polylactic acid, heating polylactic acid under existence of trifluoro tin methanesulfonate (TFS tin) subsequently, and making generated lactide distill.[0010]By using TFS tin in the 1st invention, compared with a catalyst known until now, oligomerization of lactic acid progresses at a more than twice as many speed as this, and polylactic acid of a higher molecular weight of the average molecular weights 300-10000 is obtained.[0011]L(+)-lactic acid, D(-)-lactic acid, or its mixture can be used for lactic acid used when compounding polylactic acid from lactic acid using TFS tin.[0012]As for temperature at the time of compounding polylactic acid from lactic acid using TFS tin, 300 ** or less at which disassembly of TFS tin does not take place, but drying advances easily is good. Although it is related also to a decompression degree especially, 100-200 ** which is the temperature which neither lactic acid nor lactide distills is preferred.[0013]A pressure at the time of compounding polylactic acid from lactic acid using TFS tin has 1 in which drying advances efficiently - good 100mmHg. Preferably, although it is related also to reaction temperature, it carries out by adjusting between 10 - 50mmHg so that neither lactic acid nor lactide may distill.[0014]0.01 to 5 or less % of the weight of lactic acid is enough as quantity of TFS tin to be used, and its 0.01 to 1 % of the weight is especially economically preferred.[0015]By using TFS tin in the 2nd invention, lactide with high purity can be obtained with high yield.[0016]Polylactic acid used when manufacturing lactide from polylactic acid using TFS tin The ease of making, Or it also takes into consideration that a treatment low price of becoming liquefied with some heating to 300 or more average molecular weights are good, and prevent mixing of a chain dimer of lactic acid to inside of a lactide distillate part, or lactic acid especially, and 600-2000 are preferred.[0017]What is obtained by carrying out heating drying of L(+)-lactic acid, D(-)-lactic acid, or its mixture under nonexistence of a catalyst can be used for this polylactic acid. L(+)-lactic acid, D(-)-lactic acid, or polylactic acid produced by carrying out heating drying of the mixture can be used under existence of the periodic table IV, V, metal of a group VIII, or its salt. Of course, polylactic acid obtained by the 1st above-mentioned invention can be used.[0018]It is beyond a temperature required for an ester exchange reaction, and as for temperature at the time of manufacturing lactide from polylactic acid using TFS tin, 130-300 ** is [ below decomposition temperature of TFS tin ] good, and it is especially preferred. [ of 170-250 ** ][0019]A less than pressure which lactide distills efficiently in the above-mentioned temperature requirement of a pressure at the time of manufacturing lactide from polylactic acid using TFS tin, i.e., 100 mmHg, is good, and especially its 1 - 10mmHg is preferred. When lactide is distilling temperature and a pressure in relation to mutual in the above-mentioned temperature requirement, a pressure is adjusted so that a chain dimer of lactic acid, a chain trimer, etc. may not distill.[0020]0.01 to 5 or less % of the weight of polylactic acid is enough as quantity of TFS tin used at the time of manufacturing lactide from polylactic acid, and it is economically disadvantageous to use it more. 0.01 to 1 % of the weight is preferably good.[0021]TFS tin is Inorganic Chemistry, and 16 and 1414 (1977). It can manufacture by a method of a statement.[0022]A process of manufacturing polylactic acid from the above lactic acid, and a process of manufacturing lactide from polylactic acid can be connected, it can carry out continuously, and the reaction condition at that time can use the above-mentioned conditions, respectively. That is, heating drying of the lactic acid is carried out under existence of a catalyst or nonexistence, polylactic acid which once manufactured polylactic acid, and was continuously obtained under existence of TFS tin is heated under decompression, and lactide is made to distill.[0023][Example]Hereafter, an example explains this invention.[0024]The example 1TFS tin 0.36g was added to L-lactic acid 100g 90%, heating stirring was carried out by 200 ** and 10mmHg after 3-hour stirring by 200 ** and 30mmHg for about 1 hour, and the polylactic acid which is the average molecular weight 7000 of 51.0 g was obtained. [0025]Except having used metal tin instead of TFS tin of comparative example 1 Example 1, it reacted like Example 1 and processed. The polylactic acid which is the average molecular weight 3000 of 45.0 g was obtained.[0026]The example 2TFS tin 2.26g was added to the L(-)-polylactic acid 634g of the average molecular weight 460, and it stirred by 150 ** and 30mmHg for 1 hour. As a result, the average molecular weight of polylactic acid increased to 800-850. Then, decompressed to 5mmHg, lactide was made to distill at 175-230 **, and 609 g of rough lactide was obtained. 300 g of isopropyl alcohol washed this twice, and 505 g of pure lactide was obtained after desiccation.83% (total of the lactic acid unit in the lactide which might receive the total of the lactic acid unit in polylactic acid) of yieldMelting point 96-98 ** [0027]Except having used metal tin instead of TFS tin of comparative example 2 Example 2, it reacted like Example 1 and processed. 602 g of rough lactide was obtained, this was refined like Example 2 and 439 g of pure lactide was obtained.73% (total of the lactic acid unit in the lactide which might receive the total of the lactic acid unit in polylactic acid) of yieldMelting point 96-98 ** [0028]The example 3TFS tin 1.96g was added to the L(-)-polylactic acid 652g of the average molecular weight 550, and it stirred by 150 ** and 30mmHg for 1 hour. As a result, the average molecular weight of polylactic acid increased to 800-850. Then, decompressed to 5mmHg, lactide was made to distill at 175-230 **, and 636 g of rough lactide was obtained. 11 g of residue remained in the reaction machine as a still residue. The aforementioned polylactic acid 713g was newly added to this, it processed similarly, and 703 g of rough lactide was obtained.13 g of residue remained in the reaction machine as a still residue. Twice [ further ], theaforementioned polylactic acid (735g and 613g) was added, and was processed in a similar manner, respectively. Each rough lactide 712g and 600g was obtained. 1250 g of isopropyl alcohol washed 2651 g in all for the rough lactide obtained by four processings twice, and 2235 g of pure lactide was obtained after desiccation.85% (total of the lactic acid unit in the lactide which might receive the total of the lactic acid unit in polylactic acid) of yieldMelting point 96-98 ** [0029]The example 4TFS tin 1.98g is added to L-lactic acid 600g 90%, and temperature up is carried out, distilling off water to 170 ** under the pressure of 15mmHg. Then, heating stirring was carried out by 170 ** and 15mmHg for about 1 hour, and the polylactic acid of the inside molecular weight of the molecular weight 840 was generated. Under the present circumstances, TFS tin dissolves uniformly. The lactide which decompressed this to the pan at 7.5mmHg, and generated it at 175-220 ** was made to distill, and 402 g of rough lactide was obtained. 190 g of isopropyl alcohol washed this twice, and 329 g of pure lactide was obtained after desiccation.76% (yield of the lactide to L-lactic acid) of yieldMelting point 96-98 ** [0030]The comparative example 3 metal tin 1.98g is added to L-lactic acid 600g 90%, and temperature up is carried out, distilling off water to 170 ** under the pressure of 15mmHg. Then, heating stirring was carried out by 170 ** and 15mmHg for about 3 hours, and the polylactic acid of the inside molecular weight of the molecular weight 820 was generated. The lactide which decompressed this to the pan at 7.5mmHg, and generated it at 175-220 ** was made to distill, and 370 g of rough lactide was obtained. 175 g of isopropyl alcohol washed this twice, and 289 g of pure lactide was obtained after desiccation.67% (yield of the lactide to L-lactic acid) of yieldMelting point 96-98 **PRIOR ART[Description of the Prior Art]The manufacturing method of the lactide which heats lactic acid gradually to the temperature of 200 ** in the Germany patent specification No. 267826 gazette, and distills the lactide to generate under decompression preferably in it is indicated.[0003]In the Germany patent specification No. 1234703 gazette, the manufacturing method of the lactide from the lactic acid solution under existence of a titaniumtetraalkoxide has indicated. [0004]The manufacturing method of the lactide from polylactic acid is indicated and made the Germany patent specification No. 1083275 under existence of the metal of a periodic table VI group, V fellows, or a group VIII or its salt, for example, a zinc oxide, tin oxide, and antimony oxide.[0005]In JP,63-101378,A, the manufacturing method of the lactide from lactic acid or polylactic acid is indicated under existence of metal tin or halogenation tin.TECHNICAL PROBLEM[Problem(s) to be Solved by the Invention]The chemical yield of the lactide by the above-mentioned publication is never satisfying. In this, to JP,63-101378,A with comparatively sufficient lactide yield. The manufacturing method of the lactide "which adds metal tin of a catalyst amount to lactic acid 90%, carries out temperature up of this solution, distilling off waterto about 170 ** under the pressure of 15mmHg, makes it convert to oligomer, subsequently carries out temperature up to about 215 ** under the pressure of 7.5mmHg, and makes lactide distill" is indicated. In this method, although metal tin is used as a catalyst, since this is a heterogeneous catalyst, it is activity only in a catalyst surface, but in order to reduce the amount of the catalyst used in consideration of economical efficiency, a catalyst which becomes uniform is desired during a reaction. Metal tin had a fault which fuses above 232 ** and becomes massive and whose surface area of a catalyst decreases remarkably. In order to raise the lactide purity in the rough lactide to distill, it is necessary to generate oligomer in the case of a lactide distillate, and it once needs to prevent the distillate of lactic acid, a chain dimer, a chain trimer, etc. In the catalyst indicated to JP,63-101378,A, although its metal tin was quick, even if that metal tin was used for the generation rate of this oligomer, it was required for 3 to 4 hours to obtain oligomer of sufficient molecular weight for a lactide distillate.[0007]The purpose of this invention is to provide the manufacturing method of the lactide which was excellent in the economical efficiency using a catalyst with high lactide yield quickly [ an oligomer generation rate ].MEANS[Means for Solving the Problem]This invention persons found out that oligomerization progressed at a more than twice as many speed as this compared with a catalyst known until now, and polylactic acid was obtained, when lactic acid was heated under existence of trifluoro tin methanesulfonate (it abbreviates to TFS tin hereafter.), as a result of inquiring wholeheartedly. Under existence of TFS tin, when polylactic acid was heated, it found out that lactide was distilled with high yield, and this invention was completed.[0009]Namely, are it a manufacturing method of polylactic acid by which it is characterized that an invention of the 1st of this invention carries out heating drying of the lactic acid under existence of trifluoro tin methanesulfonate (TFS tin), and the 2nd invention, Are it a manufacturing method of lactide by which it is characterized to heat polylactic acid under existence of trifluoro tin methanesulfonate (TFS tin), and to make generated lactide distill, and the 3rd invention, It is a manufacturing method of lactide carrying out heating drying of the lactic acid under existence of a catalyst or nonexistence, once manufacturing polylactic acid, heating polylactic acid under existence of trifluoro tin methanesulfonate (TFS tin) subsequently, and making generated lactide distill.[0010]By using TFS tin in the 1st invention, compared with a catalyst known until now, oligomerization of lactic acid progresses at a more than twice as many speed as this, and polylactic acid of a higher molecular weight of the average molecular weights 300-10000 is obtained.[0011]L(+)-lactic acid, D(-)-lactic acid, or its mixture can be used for lactic acid used when compounding polylactic acid from lactic acid using TFS tin.[0012]As for temperature at the time of compounding polylactic acid from lactic acid using TFS tin, 300 ** or less at which disassembly of TFS tin does not take place, but drying advances easily is good. Although it is related also to a decompression degree especially, 100-200 ** which is the temperature which neither lactic acid nor lactide distills is preferred.[0013]A pressure at the time of compounding polylactic acid from lactic acid using TFS tin has 1 inwhich drying advances efficiently - good 100mmHg. Preferably, although it is related also to reaction temperature, it carries out by adjusting between 10 - 50mmHg so that neither lactic acid nor lactide may distill.[0014]0.01 to 5 or less % of the weight of lactic acid is enough as quantity of TFS tin to be used, and its 0.01 to 1 % of the weight is especially economically preferred.[0015]By using TFS tin in the 2nd invention, lactide with high purity can be obtained with high yield.[0016]Polylactic acid used when manufacturing lactide from polylactic acid using TFS tin The ease of making, Or it also takes into consideration that a treatment low price of becoming liquefied with some heating to 300 or more average molecular weights are good, and prevent mixing of a chain dimer of lactic acid to inside of a lactide distillate part, or lactic acid especially, and 600-2000 are preferred.[0017]What is obtained by carrying out heating drying of L(+)-lactic acid, D(-)-lactic acid, or its mixture under nonexistence of a catalyst can be used for this polylactic acid. L(+)-lactic acid, D(-)-lactic acid, or polylactic acid produced by carrying out heating drying of the mixture can be used under existence of the periodic table IV, V, metal of a group VIII, or its salt. Of course, polylactic acid obtained by the 1st above-mentioned invention can be used.[0018]It is beyond a temperature required for an ester exchange reaction, and as for temperature at the time of manufacturing lactide from polylactic acid using TFS tin, 130-300 ** is [ below decomposition temperature of TFS tin ] good, and it is especially preferred. [ of 170-250 ** ] [0019]A less than pressure which lactide distills efficiently in the above-mentioned temperature requirement of a pressure at the time of manufacturing lactide from polylactic acid using TFS tin, i.e., 100 mmHg, is good, and especially its 1 - 10mmHg is preferred. When lactide is distilling temperature and a pressure in relation to mutual in the above-mentioned temperature requirement, a pressure is adjusted so that a chain dimer of lactic acid, a chain trimer, etc. may not distill.[0020]0.01 to 5 or less % of the weight of polylactic acid is enough as quantity of TFS tin used at the time of manufacturing lactide from polylactic acid, and it is economically disadvantageous to use it more. 0.01 to 1 % of the weight is preferably good.[0021]TFS tin is Inorganic Chemistry, and 16 and 1414 (1977). It can manufacture by a method of a statement.[0022]A process of manufacturing polylactic acid from the above lactic acid, and a process of manufacturing lactide from polylactic acid can be connected, it can carry out continuously, and the reaction condition at that time can use the above-mentioned conditions, respectively. That is, heating drying of the lactic acid is carried out under existence of a catalyst or nonexistence, polylactic acid which once manufactured polylactic acid, and was continuously obtained under existence of TFS tin is heated under decompression, and lactide is made to distill.EXAMPLE[Example]Hereafter, an example explains this invention.[0024]The example 1TFS tin 0.36g was added to L-lactic acid 100g 90%, heating stirring was carried out by 200 ** and 10mmHg after 3-hour stirring by 200 ** and 30mmHg for about 1 hour, and the polylactic acid which is the average molecular weight 7000 of 51.0 g was obtained.[0025]Except having used metal tin instead of TFS tin of comparative example 1 Example 1, it reacted like Example 1 and processed. The polylactic acid which is the average molecular weight 3000 of 45.0 g was obtained.[0026]The example 2TFS tin 2.26g was added to the L(-)-polylactic acid 634g of the average molecular weight 460, and it stirred by 150 ** and 30mmHg for 1 hour. As a result, the average molecular weight of polylactic acid increased to 800-850. Then, decompressed to 5mmHg, lactide was made to distill at 175-230 **, and 609 g of rough lactide was obtained. 300 g of isopropyl alcohol washed this twice, and 505 g of pure lactide was obtained after desiccation.83% (total of the lactic acid unit in the lactide which might receive the total of the lactic acid unit in polylactic acid) of yieldMelting point 96-98 ** [0027]Except having used metal tin instead of TFS tin of comparative example 2 Example 2, it reacted like Example 1 and processed. 602 g of rough lactide was obtained, this was refined like Example 2 and 439 g of pure lactide was obtained.73% (total of the lactic acid unit in the lactide which might receive the total of the lactic acid unit in polylactic acid) of yieldMelting point 96-98 ** [0028]The example 3TFS tin 1.96g was added to the L(-)-polylactic acid 652g of the average molecular weight 550, and it stirred by 150 ** and 30mmHg for 1 hour. As a result, the average molecular weight of polylactic acid increased to 800-850. Then, decompressed to 5mmHg, lactide was made to distill at 175-230 **, and 636 g of rough lactide was obtained. 11 g of residue remained in the reaction machine as a still residue. The aforementioned polylactic acid 713g was newly added to this, it processed similarly, and 703 g of rough lactide was obtained.13 g of residue remained in the reaction machine as a still residue. Twice [ further ], the aforementioned polylactic acid (735g and 613g) was added, and was processed in a similar manner, respectively. Each rough lactide 712g and 600g was obtained. 1250 g of isopropyl alcohol washed 2651 g in all for the rough lactide obtained by four processings twice, and 2235 g of pure lactide was obtained after desiccation.85% (total of the lactic acid unit in the lactide which might receive the total of the lactic acid unit in polylactic acid) of yieldMelting point 96-98 ** [0029]The example 4TFS tin 1.98g is added to L-lactic acid 600g 90%, and temperature up is carried out, distilling off water to 170 ** under the pressure of 15mmHg. Then, heating stirring was carried out by 170 ** and 15mmHg for about 1 hour, and the polylactic acid of the inside molecular weight of the molecular weight 840 was generated. Under the present circumstances, TFS tin dissolves uniformly. The lactide which decompressed this to the pan at 7.5mmHg, and generated it at 175-220 ** was made to distill, and 402 g of rough lactide was obtained. 190 g of isopropyl alcohol washed this twice, and 329 g of pure lactide was obtained after desiccation.76% (yield of the lactide to L-lactic acid) of yieldMelting point 96-98 ** [0030]The comparative example 3 metal tin 1.98g is added to L-lactic acid 600g 90%, and temperature up is carried out, distilling off water to 170 ** under the pressure of 15mmHg. Then, heating stirring was carried out by 170 ** and 15mmHg for about 3 hours, and the polylactic acid of the inside molecular weight of the molecular weight 820 was generated. The lactide which decompressed this to the pan at 7.5mmHg, and generated it at 175-220 ** was made to distill, and 370 g of rough lactide was obtained. 175 g of isopropyl alcohol washed this twice, and 289 g of pure lactide was obtained after desiccation.67% (yield of the lactide to L-lactic acid) of yield Melting point 96-98 **。